POC ELECTRICAL DEVELOPMENT and BACKGROUND REPORT

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POC ELECTRICAL DEVELOPMENT AND BACKGROUND REPORT- POC Tie-In Report Proposals, Schemes for Feeding POC Project plus related CBDC, RRE Supplies, GUP Power Station and TRANSCO Grid Station/ Substation Page 1

Transcript of POC ELECTRICAL DEVELOPMENT and BACKGROUND REPORT

Page 1: POC ELECTRICAL DEVELOPMENT and BACKGROUND REPORT

POC ELECTRICAL DEVELOPMENT

AND BACKGROUND REPORT-

POC Tie-In Report Proposals,

Schemes for Feeding POC Project plus

related CBDC, RRE Supplies, GUP Power Station

and TRANSCO Grid Station/ Substation

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INDEX

1. SCENARIO ‘A’ RELATED TO TIE-IN REPORT OPTION 2 (TRANSCO RUWAIS 400KV GRID STATION).....6

2. SCENARIO ‘B’ RELATED TO TIE-IN REPORT OPTION 3B (TRANSCO GAYATHI ROAD 220KV SUBSTATION)...........................................................................................................................................................................7

3. MATTERS RELATED TO TIE-IN REPORT SCENARIOS ‘A’ & ‘B’, POWER SUPPLIES and the ONE-LINE DISTRIBUTION SKETCHES....................................................................................................................................................8

3.1. Power Factor.................................................................................................................................................................8

3.2. RRE Substation ‘0’ Loading (33kV Switchboards)...................................................................................................8

3.3. Additional POC 220kV GIS Main Substation............................................................................................................9

Incoming Feeders from TRANSCO..........................................................................................................................9

One Line Diagram...................................................................................................................................................9

Main Substation Location.......................................................................................................................................9

HV Cabling Lengths.................................................................................................................................................9

POC Power Supply Tie-in Concept........................................................................................................................10

3.4. The Supply Authority..................................................................................................................................................10

3.5. IPCS Motor Re-acceleration/ Restarting..................................................................................................................11

Definitions............................................................................................................................................................11

No-Break Changeover (NBC) and Re-acceleration................................................................................................11

Automatic Dead Changeover (ADC) and Restarting..............................................................................................12

Small Motors and ADC Practice............................................................................................................................12

3.6. Reserve Power............................................................................................................................................................13

TAKREER Power Station (GUP)..............................................................................................................................13

TRANSCO Grid Station and Substation..................................................................................................................13

3.7. 220kV GIS Switchboards...........................................................................................................................................14

3.8. Option 3B (Tie-in Report)...........................................................................................................................................14

3.9. Downstream MCC Switchboards Design.................................................................................................................15

Normal MCC Switchboard Considerations............................................................................................................15

Emergency Switchboards......................................................................................................................................15

MCC Contactors....................................................................................................................................................15

Downstream POC Substations..............................................................................................................................16

Incoming Supply Cabling.......................................................................................................................................16

3.10. ETAP Adequacy Study..........................................................................................................................................16

4. POWER DISTRIBUTION CONCLUSIONS.................................................................................................................17

4.1. Power Factor...............................................................................................................................................................17

4.2. RRE Substation ‘0’ Loading (33kV Switchboards).................................................................................................17

4.3. Additional POC 220kV GIS Main Substation..........................................................................................................18

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Incoming Feeders from TRANSCO........................................................................................................................18

Main Substation Location.....................................................................................................................................18

HV Cabling Lengths...............................................................................................................................................19

4.4. The Supply Authority..................................................................................................................................................19

4.5. IPCS Motor Re-acceleration/ Restarting..................................................................................................................19

No-Break Changeover (NBC) and Re-acceleration................................................................................................19

Automatic Dead Changeover (ADC) and Restarting..............................................................................................20

The Choice of NBC or ADC for MCC Switchboard Specification............................................................................20

4.6. Reserve Power............................................................................................................................................................20

TAKREER Power Station (GUP)..............................................................................................................................20

TRANSCO Grid Station and Substation..................................................................................................................21

General.................................................................................................................................................................21

4.7. 220kV GIS Switchboards...........................................................................................................................................21

4.8. Option 3B (Tie-in Report)...........................................................................................................................................21

4.9. Downstream MCC Switchboards Design.................................................................................................................22

Normal MCC Switchboard Considerations............................................................................................................22

Emergency Switchboards......................................................................................................................................23

MCC Contactors....................................................................................................................................................24

The Choice for Normal and Emergency Switchboards..........................................................................................24

Incoming Supply Cabling.......................................................................................................................................24

4.10. ETAP Adequacy Study..........................................................................................................................................25

5. APPENDIX- MCC SWITCHBOARDS DESIGN AND THE CU BUS-BAR RATING...............................................26

5.1. Requirements of the DGS-EU-001 Clause 11.8.d..................................................................................................26

Automatic Dead Changeover (ADC)......................................................................................................................26

No-Break Changeover (NBC).................................................................................................................................27

Double-Jeopardy...................................................................................................................................................27

5.2. Clause Requirements for Turnaround Power Centre (TPC) Switchboard..........................................................28

5.3. Operations and Engineering Design Working Practices........................................................................................28

5.3.1. 11kV Switchboards.................................................................................................................................................28

5.3.2. 415V and 3.3kV Switchboards..............................................................................................................................29

Supply Breakers Changeover Operation...............................................................................................................29

Bus-bars................................................................................................................................................................30

5.4. Conclusions related to MCC Switchboards.............................................................................................................31

5.4.1. 11kV Switchboards.................................................................................................................................................31

5.4.2. 415V and 3.3kV Switchboards..............................................................................................................................31

5.4.3. Switchboard Bus Supply and Section Breakers- General (All Voltages)........................................................32

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ATTACHMENTS:

A. One Line Mark-up Sketch (Initial Scheme)….………………………………………..……………..…….…………33

B. POC Project Development – Future Project Sketch…………………….…………………..………….......………34

C. Power Distribution of GUP Sketch…………………………………………………………………...….……………35

D. POC Project Development – Latest POC Power Distribution Sketch…………………………..……………....36

E. OPTION 3B - Gayathi Road Spare Capacity Estimate……………......………………………………..…….…….37

F. Emergency Distribution System – Switchboard/ EDG Locations Sketch………………………………….…..38

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ABBREVIATIONS:

AC Alternating CurrentADC Automatic Dead Changeover [Switchboard]ADGAS Abu Dhabi Gas Liquefaction Company LimitedADNOC Abu Dhabi National Oil CompanyADWEA Abu Dhabi Water & Electricity AuthorityATS Automatic Transfer SwitchBOROUGE ADNOC & Borealis (Austria) JVCB Circuit BreakerCBDC Carbon Black and Delayed Coker [Project]DGS Design General SpecificationEDG Emergency Diesel GeneratorEPC Engineering Procurement and ConstructionETAP Electrical Transient Analyser ProgramFEED Front End Engineering DesignFERTIL Ruwais Fertilizer IndustriesGASCO Abu Dhabi Gas Industries LtdGIS Gas Insulated SwitchgearGUP General Utilities Plant [incl. Power Station]HAZOP Hazardous and Operability [Study]HV High VoltageHVAC Heating, Ventilation and Air-ConditioningIBCL International Bechtel Company LtdIPCS Integrated Protection & Control SystemLPG Liquefied Petroleum GasLV Low VoltageMCC Motor Control CentreMEP Main Emergency PanelMOM Minutes of MeetingMV Medium VoltageNBC No-Break Changeover [Switchboard]NC Normally ClosedNFPA National Fire Protection AssociationNO Normally OpenPF(C) Power Factor (Correction)PMC Project Managing Contractor [Worley Parsons Abu Dhabi]POC Processing Offshore Crude [Project]RFI Request for InformationRRD Ruwais Refinery Development [Project]RRE Ruwais Refinery Expansion [Project]SEP Secondary Emergency PanelSIS Satellite Instrument RoomSLD Single Line DiagramSRU Sulphur Recovery UnitSS Sub-StationTAKREER Abu Dhabi Oil Refining CompanyTPC Turnaround Power CentreTRANSCO Abu Dhabi Transmission & Dispatch CompanyUPS Uninterruptible Power SupplyU&O Utilities & OffsitesVT Voltage Transformer

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1. SCENARIO ‘A’ RELATED TO TIE-IN REPORT OPTION 2 (TRANSCO RUWAIS 400KV GRID STATION)

It is believed that Engineering Design Data (utilizing Diversity Factors and other Design criteria from the TAKREER Electrical Design Guidelines) shows that future CBDC Project when running can overload the Ruwais Grid Station (utilizing the standard TRANSCO operating requirement of 0.9 for the Power Factor [PF].

So while there was an intention by TAKREER to feed CBDC from the Ruwais Grid Station (Option 2 of the Tie-In Report 5652-STU-EU-001), then this is perhaps the reason why TRANSCO indirectly require downstream consumers including TAKREER to provide sufficient Power Factor Correction [PFC] equipment to achieve a 0.95 overall system PF. This can provide 5% extra power above its nominal rating from Ruwais Grid Station.

The downstream 3rd Party consumers fed from TAKREER switchboards can potentially be a problem, e.g. ADNOC, GASCO, BOROUGE, FERTIL, etc. Strictly TAKREER Standard asks for 0.95 already but have all the EPC Contractors or the 3 rd Party consumers correctly implemented it. Additionally (if necessary) existing TAKREER generation can possibly be utilized to help improve the PF in certain areas by operating as synchronous condensers; large synchronous motors can be used similarly.

If this 0.95 PF is not met, TRANSCO have the right to refuse to supply the extra power for CBDC. TRANSCO have decided that their fixed design size of Grid Station does not otherwise have the spare capacity; the Station MVA rating is fixed. This effectively means that TRANSCO will have to disconnect power to part of RRE also if there is no compliance, as CBDC is supplied at 33kV from the RRE 220kV Feeder(s) derived from TRANSCO 400kV Ruwais Grid Station. There is no dedicated EHV/HV Intake Substation for CBDC. Maybe some RRE Process Units get shutdown as a result and there can be a cascade effect on many others.

The possible requirement for some extra PFC equipment can potentially affect most MV (and LV, only if more practical) Switchboards in CBDC, RRE, RRD and 3 rd Party Substations. It can be costly and messy as it uses up spare CBs (if they exist) and needs space for extra panel equipment in Switchrooms. It may not be practical for some associated Switchboards/ Switchrooms, especially such items for 3rd Party consumers. Also the timescale for its design, fabrication and installation is not short, ruling out quick, last-minute retro-fitting.

Note: A simple direct connection only from GUP or RRE to main POC area Intake Substation was part of the Scope basic assumption for the POC FEED Contract as this is all that was really necessary to source power (tele-conference RFI letter L-BL-PA-25886-4.2.1-0027 of 16-1-2014 refers). The direct connection concept from GUP became Option 1 of the Tie-In Report 5652-STU-EU-001 after overloaded RRE was ruled out by its Overall Load Summary document contained in the Report.

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2. SCENARIO ‘B’ RELATED TO TIE-IN REPORT OPTION 3B (TRANSCO GAYATHI ROAD 220KV SUBSTATION)

The prospect of the potential chaos, further high costs for PFC equipment and lost production described in SCENARIO ‘A’ can be avoided by TAKREER agreeing to fully implement Electrical Tie-in Report 5652-STU-EU-001 Option 3B ASAP, without any further conditions or caveats. “OPTION 3B modified” was initially requested as per the Attachment A but subsequently it has developed from Attachment B into the Single Line Diagram of Attachment D.

The simple intent of Option 3B proposed by the FEED ENGINEER (IBCL) is to implement the concept of moving the source of the CBDC electrical power now as part of the POC FEED, so it will be effectively fed from the old TRANSCO Gayathi Road Substation and NOT the new Ruwais Grid Station. There is plenty of spare capacity there (refer to Attachment E). The CBDC cabling work can easily be performed by a local Contractor at any time; very little trench work is necessary.

The Sketch "Scheme for Feeding POC Project" is in error in stating "in case the existing capacity is found to be inadequate". TRANSCO have already decided that they will have a power shortfall. Note that the original Power Demand requirement sent to TRANSCO for the new Ruwais 400kV Grid Station did NOT include the requirement for CBDC loads.

As the CBDC loads require 33kV tie-ins, it is necessary for CBDC area to be fed from a new intermediate FEED Substation at an additional location on route to the main POC area in order to prevent a volt-drop problem; additionally re-use of existing 33kV Incoming Feeder cabling as far as possible is sensible engineering.

220kV incoming Supplies to this Substation is practical from Gayathi Road Substation as spare capacity is available. The choice then appeared to be two completely new 220kV circuits, including GIS Breakers with a big ticket price. However engineering development by Electrical Team as Section 3.3 and 4.3 - Incoming Feeders from TRANSCO has reduced this cost considerably.

A lot of the existing cable route for the 33kV CBDC cables hopefully can remain the same with a suitable choice of location for this 220kV FEED Substation, thus saving TAKREER some further costs. IBCL needed to consider the Engineering and Man-hour requirements for re-routing a portion of the original 33kV CBDC cabling and shifting the cables to the completely new intermediate POC Main Substation (needing extra FEED drawings, etc.).

Subsequently FEED Engineering Man-hours have been agreed for the new POC 220kV Main Substation (SS 200) and other recent Electrical Distribution design downstream from TRANSCO (refer to Attachment D) in order to comply with the Power Supply and Tie-in Study “Option 3B modified” latest.

So it has been finally confirmed that the 54No CBDC Power Supply cables are to be shifted as part of POC Project. The MOM M/BL/PL/5652/1.7.1/0127 of the 9th/10th November Engineering meeting and PMC letter L-PL-BL-5652-1.2.2-0591 of 24th November 2014 refer to the total POC technical requirements agreed by all relevant parties that includes this CBDC Supply cabling.

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3. MATTERS RELATED TO TIE-IN REPORT SCENARIOS ‘A’ & ‘B’, POWER SUPPLIES and the ONE-LINE DISTRIBUTION SKETCHES

3.1. Power Factor

The main intent of TRANSCO is essentially to prevent overload of the Ruwais 400kV Grid Station above its 1000MW nominal capacity. Hence the TRANSCO requirement for a minimum overall PF of 0.95 (capacity is 1055MW if PF=0.95 is achieved, a useful increase of 55MW).

Presently it appears that some people have forgotten about the high cost and relative engineering complexity of extra PFC equipment. Any such costs will be to TAKREER account, even potentially for the downstream 3rd Party consumers. The possible loss in TAKREER Production detailed in SCENARIO ‘A’ surely does NOT warrant the high risk involved in leaving CBDC with its effective source of power as Ruwais Grid Station- already determined by TRANSCO Engineers to be “effectively overloaded” if CBDC is connected.

3.2. RRE Substation ‘0’ Loading (33kV Switchboards)

Generally the operating practice for a Switchboard (any voltage but normally FEED-designed to be supplied by two 100%-rated Transformers) is to run both the incoming Supply Transformers at 50% of the design load, the double-ended mode of operation in TAKREER Standards. The single-ended mode of operation (one Supply circuit in service with Bus-Section breaker closed) is normally used when one Supply Transformer circuit is faulty and awaiting remedial work. This can take some time if it is buried cable damage.

If the remaining Transformer consequently becomes overloaded, then load reduction must ensue. RRE Substation ‘0’ (SS 000) presently falls into this problem category and remains so until there are some remedial electrical design philosophy changes regarding RRE 33kV power sources and subsequent tie-in points (Refer to RRE Overall Load Summary 5578-E3-REP-EU-001). Even with connection of the PFC equipment to the 11kV Switchboards, the Maximum Normal and Peak Load on a Transformer feeding a single-ended RRE 33kV Switchboard is above its rated output, before considering DGS requirement of 25% for Future modifications, etc. Note that POC is adding some such Future motor loads now to RRE SS 000.

Also future CBDC Project presently has its initial tie-ins planned at this same Substation. However refer to Attachment D for an indication of the latest TAKREER Electrical Distribution System showing CBDC Supply as part of POC system.

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3.3. Additional POC 220kV GIS Main Substation

Incoming Feeders from TRANSCO However the Proposal to reuse both the TRANSCO 220kV circuit equipments that previously fed GUP transformers to now feed this intermediate Substation is not perfect. TRANSCO have a plan to re-enforce part of their Gayathi Road network with one of the circuits planned for use with POC 220kV Intake Transformer, specifically the Bay D4 Breaker. So TAKREER Budget needs to include for one new 220kV GIS Breaker and protection/ metering panels for Bay D3 (presently unequipped) at a cost of one to two million dollars.

One Line Diagram The conceptual One Line Sketch “Scheme for Feeding POC Project” (enclosed with letter L-PL-BL-5652-1.2.2-0187 to IBCL dated 2nd May 2014) shows the proposed connections for this major 220kV FEED Substation, including cable connections to POC (ARDS area) Intake Substation; an amended copy is attached as Attachment A. The schematic cable connections were subject to POC loads development and a firmer CBDC load.

Subsequently the electrical system has progressed from Attachment B then Attachment D. POC Distribution Intake Substation now has 4No 132kV incoming feeder circuits as POC load has increased, mainly due to 8No large synchronous motors in the ARDS Unit. There are also two 132kV feeder circuits to the new POC Sulphur Recovery Substation for the local Units 3700, 3800 and 3900.

Note: As per Electrical Deliverables letter L-PL-BL-5652-1.2.2-0445 dated 29th August 2014, this additional 220kV Main Substation (SS 200) has been added to POC scope.

Main Substation Location FEED electrical layout is indicating 85m separation from nearest LPG sphere against a minimum 60m requirement in DGS-PU-001. NFPA 58 (Liquefied Petroleum Gas Code) Table 6.3.1 refers to 122m separation distances between LPG Storage Facilities and 'Important Buildings'. An 'Important Building' is not defined within NFPA; however, it is interpreted as a continuously occupied building. Since Substations are not normally occupied (criterion <20% of the time), the Substations are not classified as 'Important Buildings'. Additionally this Substation is not placed in a down-wind direction of the LPG Sphere(s).

Note: This 'Important Building' definition criteria concerns continuous human occupancy and related possible life-and-death matters and is not related to the cost of the building. The probability of personnel normally being present in Substation 200 is low as it is “unmanned” and the number will only ever be small. In any case, only “a competent person” can get inside as part of normal authorization/ security entry procedures.

HV Cabling Lengths This intermediate 220kV Main Substation represents the load-end of the 220kV POC feeder circuits from TRANSCO. As such, the Substation location saves the cost of an additional 3.6 Km route length of cable onward to POC area, i.e. saving a minimum total length of 21.6 Km of single core 220kV cable, for 2No supply circuits.

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The FEED Engineer has also found that the cabling for part of two existing out-of-use 220kV feeder circuits to GUP running from TRANSCO Gayathi Road Substation can be re-used to feed this POC Main Substation, saving some further 220kV cable cost. The new cables can be spliced into the old at Cable Joint Pit CJP-4, near the old Ruwais Hospital.

This has further saved about 3.5Km route length of cable equating to 21Km of single-core 220kV cable. So overall approximately 21.6 +21 = 42.6Km of 220kV cable is the saving. As the single-core sizing is a large 1200mm2 in order to match the existing, this saving is quite significant. However a further 4.6 Km route length of new 1200mm2 220kV cable is still required with appropriate Joint Pits, a buried cable length of approximately 27.6 Km.

POC Power Supply Tie-in Concept It shall be remembered that the power source for POC was originally assumed to be GUP or RRE and there was no direct involvement with the TRANSCO Grid. Both the Option 2 and Option 3 of Electrical Tie-In Report were proposed as alternatives (at 2nd

March 2014 Electrical Meeting in Abu Dhabi – see MOM M/BL/25886/4.7.1/0012 and follow-on related Site Survey work detailed in MOM M/BL/25886/4.7.1/0018) long after initial POC FEED Scope definition and Contract placement, Option 3 being subject to a late decision on its inclusion.

3.4. The Supply Authority

The Supply Provider for a lot of TAKREER’s electrical power is now TRANSCO (not ADWEA), so as such they have the right and authority to disconnect or withhold their power from any consumer, be it TAKREER or any other customer, if their conditions are not met. These include the TAKREER Motor Contribution to TRANSCO Ruwais Grid Station 220kV Bus-bars; also any requested Tie-in PF for any or all TAKREER circuits, especially as 100% of all the connected circuits power is the responsibility of TAKREER. If necessary, they may need to discipline their 3rd Party Consumers by passing on any TRANSCO requirements.

No overload is also another obvious condition to be met so the electrical protection on individual TRANSCO 220kV feeders will automatically disconnect TAKREER power when necessary. Sensible and proper Electrical Distribution System planning foresight and action is required now.

Attachment C depicts a simplified SLD of the overall TAKREER Electrical Distribution System and its main consumers. Refer to Attachment D for the latest Sketch of the TAKREER POC Distribution System that satisfies both TRANSCO and TAKREER.

Note: The TAKREER ‘Power Demand Forecast 2013-2023’ document that is agreed/ approved by TRANSCO (it includes Ruwais 400kV Grid Station) does NOT include for CBDC or POC Project.

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There is essentially NO power margin on Ruwais Grid Station presently, witness the approximate 1020MW load stated in the FICHTNER 2009 Study Report for this nominal 1000MW Grid Station (at a PF=0.9; 1055MW if PF=0.95). A power margin is necessary for any planned future Project but especially essential for Re-acceleration of motors/ recovery of the Process after an electrical disturbance (refer to Section 3.5).

On this basis, the connection of a future Project (e.g. CBDC) can be sensibly ruled out for Ruwais Grid Station for technical reasons based on prudent load figures and margin requirement - a realistic Reserve power margin is essential and this effectively means that NO spare capacity is available.

Too many Process trips can be an indication of an “effectively overloaded” power supply. An insufficient Reserve capacity allowance can cause such problems and a permanent solution (if practical) can be slow to implement, the aggravated and reduced production taking a long time to be eliminated.

If TAKREER was generating all its own power, they could operate at the more traditional PF of 0.8 for Process Plants, as all related operating costs are to TAKREER account; the power supply is generally firmer and more reliable then. TAKREER could also add additional motor loads at will and only have to answer to them-selves. The Motor Contribution to electrical fault current then only affects TAKREER Switchboards and cannot upset TRANSCO.

3.5. IPCS Motor Re-acceleration/ Restarting

DefinitionsThe term Re-acceleration is more applicable to IPCS MCC Control Modules and motor control schemes associated with “No-Break Changeover (NBC)” of the MCC Switchboard power supply by the Bus Supply/ Section breakers. The changeover is fast and the motors designated for Re-acceleration do not stop as there is no break in their supply.

The term Restarting is more applicable to “Automatic Dead Changeover (ADC)” control schemes for the MCC power supplies. The changeover by the breakers is relatively slow so the motors designated for Re-acceleration/ Restarting do stop due to the inherent supply break, voltage decay delay and a further control sequence IPCS MCC Restart Timer delay, all delaying the return of individual motor supplies. Motor startup currents ensure that all the designated motors cannot restart at once, so a sequence involving several groups of motors may be needed.

No-Break Changeover (NBC) and Re-accelerationProcess trips due to electrical MCC Switchboard supply short-circuit system fault/ supply collapse (i.e. main protection operates and initiates breaker transfer) can generally be eliminated by “worst-case” Bus-bar Cu rating selection plus the correct logical choice (i.e. NBC) of the supply changeover sequence of the Bus Supply/ Section breakers in the FEED; these two MCC Switchboard design philosophy requirements

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work together and complement each other (NBC is as detail in Section 5.1 Appendix, which also includes an explanation/ review of ADC Double-Jeopardy).

When the MCC Switchboard design follows the NBC principle for the breakers (i.e. European Practice), the extra delay associated with each IPCS Restart Timer does not normally come into play; all sizes of motors and other loads remain connected during the supply changeover, thus generally eliminating the possibility of Process/ Unit trips.

It must be noted that a voltage dip or loss can happen reasonably frequently; such a loss is always associated with ADC. So this is another reason why European NBC Practice for changeover of Bus-bar Supply/ Section breakers is strongly recommended in order to eliminate most of such “lost Bus volts” occurrences that are certainly unnecessary. They can be designed out in the FEED to allow normal continuous Unit operation.

Note: The exception to this is when NBC MCC Bus is operating in single-ended mode. The motors may stop and then suffer a Restart sequence delay; however single-ended is classed as abnormal operation.

Automatic Dead Changeover (ADC) and RestartingHowever the extra delay before supply reconnection to the Bus-bar plus Restarting delay of individual motors is always present with the ADC Switchboard Bus design principle (Section 5.1 Appendix), so the probability of a Process trip is much greater. This is true regardless of whether the changeover is initiated by the main or backup (slower) protection device.

A long changeover/ Restart overall delay is an inherent characteristic of this less-desirable ADC control scheme due to the additional voltage decay delay necessary for safety, before the further sequence time-delays prior to the re-connection of the motors by the individual IPCS Restart timers. Such an overall delay can be eliminated by the choice of NBC, reducing the possibility of Process Unit trips after a supply problem.

Small Motors and ADC PracticeAlso the ADC of the Bus-Section breaker will always cause a break in supply and as a result stop the connected small motors and associated pumps, etc. The MCC Switchboard contactors drop out. This will not happen with an NBC Switchboard. Such small motors in particular are not normally part of automatic IPCS Restart control schemes.

Consequently small motors need to be manually restarted and this can easily go unnoticed. This often involves a manual pushbutton action in the field. Operators become lethargic towards restarting such small motors as Unit(s) production does not immediately stop; however the quality of the Process product is affected if they are not restarted and a Unit problem becomes a lot more probable with subsequent trip.

3.6. Reserve Power

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TAKREER Power Station (GUP)A margin of unused Reserve power always needs to exist to ensure that motor loads can re-accelerate quickly after any electrical disturbances. This is in addition to Future/ Spare capacity allowance normally required but not always present after unexpected load growth.

This overall Reserve is normally an inherent part of a U&O Power Station provided by the COMPANY; the GUP provides this Power Generation for TAKREER (Attachment C refers). It needs to be available at the 132/220kV voltage level where the Generation units are feeding power, leading downstream to the 11kV/3.3kV/415V MCC Switchboards supplying the electrical motors.

A dedicated power station normally runs in the Spinning Reserve mode of operation with N main generators running; for example GUP originally had a theoretical power margin of approximately 20% when not running in the (N-1) mode [where N is the total number of main unit generators for 132/220V consumers].

This Spinning Reserve margin allows for motor Re-acceleration/ restart control system to operate correctly to allow a continuous Process without unnecessary Process trips. The intent is that there is sufficient Reserve power margin for a group (or groups) of motors to quickly accelerate and regain top speed. The sequence of the motors for the Re-acceleration control scheme ensures that the least important for continuity of Process Unit operation are restarted last.

TRANSCO Grid Station and SubstationWhen the source of power for a Petro-chemical Project is from the local Supply Authority e.g. TRANSCO, then similarly a Reserve of power is needed at the TRANSCO Grid Station/ Substation at the 220kV level.

TRANSCO Ruwais Grid Station must provide the equivalent to Spinning Reserve for all connected consumers including RRE (and CBDC, if connected) and this can mean a power margin of 10% minimum (estimated) is needed and this needs to remain as unused Reserve at all times.

This Reserve margin is over and above the load figure that includes peak load plus any Spare margin for future load growth. With bad load planning, the Spare margin may already have been allocated but the minimum Reserve still needs to be available; this requirement does not disappear as the Process Switchboard motors need it to Re-accelerate/ Restart. Otherwise the supply voltage can be dragged down for too long a time with potential shutdown consequences

The bigger is the Reserve margin, then the better for the electrical transient performance and safe recovery of the Process Plants without unnecessary trips and shutdowns (refer to Section 3.4 for further information specific to Ruwais Grid Station).

3.7. 220kV GIS Switchboards

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The Ruwais Grid Station 220kV GIS Bus-bars are in-essence inadequately fault-rated at 40kA (for 3secs); traditionally TRANSCO are more used to supplying power to buildings where large motor loads do not exist. The FICHTNER 2009 Study Report recommendation is for future 220kV GIS Bus-bars to be rated for 50kA 1sec (at least) so that the Motor Contribution from Process Plants does not become too significant and difficult to manage.

As unfortunately it may not be practical to uprate the existing Grid Station GIS equipment, so TRANSCO have made changes to their Grid Network to reduce the fault currents (single phase and 3-phase). Also they require a limit to the connected motor short-circuit capacity on the Consumer side, so TRANSCO have NOT approved connection of any more TAKREER loads that include large motors, specifically POC and CBDC. The Motor Contribution from TAKREER can be significantly increased otherwise and may breach the TRANSCO-imposed limits.

Borouge 3 Project and other recently expanded downstream 3rd Party TAKREER consumers can further increase this Motor Contribution at the TRANSCO 220kV Bus-bars (refer to Attachment C and Section 4.10).

Note: CBDC motor loads in the EPC design have now increased by approximately 26% as the Peak Load is now 123MVA (refer to 5636-REP-EU-001 Rev 2). It is reported that RRE motor loads have similarly increased by approximately 12%, as the Peak Load is now 349MVA. Consequently each is adversely affecting the Motor Fault Contribution to the associated TRANSCO Grid Station and with a further 25% increase to cover for the Future, the numbers are adding up.

3.8. Option 3B (Tie-in Report)

The main intent of TAKREER Option 3B was always to help alleviate an overload on Ruwais 400kV Grid Station (specifically by taking action on behalf of the problem RRE Substation ‘0’ (refer to Section 3.2) and at the same time provide a power source for POC. Thus it can be seen why Option 3 involving the power source of Gayathi Road Substation was added to the Tie-In Report 5652-STU-EU-001.

Option 3B “modified” (see Attachment A) then brought CBDC load into the power supply equation but with the CBDC transformers to be installed in the future; it is noted that a reduction is not possible for the overall CBDC load figure, so a firmer supply derived from Gayathi Road Substation was later deemed necessary to help ensure continuity of the CBDC process (refer to Attachment D SLD Sketch and Attachment E Spare Capacity estimate).

From an electrical system viewpoint, eliminating/ removing load presently planned for Ruwais Station is really what is most desirable so that it does not become “effectively overloaded" in the near future. Certainly POC and CBDC loads are not required by TRANSCO on Ruwais Grid Station as they are not on the approved ‘Power Demand Forecast 2013-2023’ document.

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To fully implement Option 3B, IBCL need to fully incorporate CBDC feeders into the FEED (CBDC Engineering is by another Contractor). This re-routed cabling requires a new intermediate 220kV FEED Main Substation (concept implementation required ASAP - see Section 4.3), including provision for new CBDC 33kV Supply Transformers and Switchgear. There will be as-built CBDC drawings and other documentation needing to be reviewed, etc. when finally received from the Contractor; the CBDC EPC design work is presently ongoing.

3.9. Downstream MCC Switchboards Design

Normal MCC Switchboard ConsiderationsSections 5.1 and 5.2 (attached Appendix), plus Section 3.5 for related motor and IPCS considerations, detail the pros and cons of the two methods for designing MCC Switchboards- namely with main breakers using NBC or ADC for Supply changeover. It is better to implement safe “Electrical HAZOP” Design at the beginning of a Project, as “prevention is better than a cure” and a cure may be impractical. The associated Switchboard Operations and Engineering Design Working Practices in Section 5.3 of Appendix shall also be noted.

It must be highlighted that the TAKREER standard design for a 415V Turnaround Power Centre by necessity uses the automatic “No-Break Changeover” (NBC) switching principle, as per the standard design for such an LV ATS switch. The connected normal/ emergency lighting load needs to be “on” continuously for safety reasons. This argument for NBC-specification Switchboards to ensure as-reliably-as-possible continuous normal lighting can equally apply to all 415V Switchboards. Even short breaks in normal lighting can be very noticeable at night or in buildings with no windows.

Emergency SwitchboardsThe Distribution System for emergency power is shown at Attachment F. A Main Emergency Panel (MEP) is by definition fed from an EDG as backup during an emergency; POC has five of these. A Secondary Emergency Panel (SEP) is fed from a suitable MEP but the SEP is located in another Substation; there are three of these.

The Pipeline Corridor containing high pressure pipelines running through the middle of TAKREER Site has a 200m exclusion zone where the location of an EDG is banned owing to the ignition properties of diesel exhaust fumes. Consequently for the two POC Substations within this zone, each is allocated an SEP as an EDG feeding an MEP is not allowable.

The shutdown of the main redundant HVAC systems when normal Mains power is lost or unavailable can cause Health and Safety/ HAZOP issues with personnel and equipment, especially over-heating problems in the high Abu Dhabi ambient. The issue concerning the lack of continuous HVAC was raised in Abu Dhabi at MOM M/BL/25886/4.7.1/0018 of 3rd to 6th March 2014.

MCC ContactorsA Contactor (air or vacuum type) is the normal power switching device for a 3-phase motor that is powered from a 415V or 3.3kV MCC Switchboard. The Contactor is located within the MCC compartment for the motor. The standard AC-voltage control

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coil of a Contactor has a drop-off voltage of approximately 65% to 70%. It is powered from the main Switchboard supply by an individual control VT hence it is affected by the state of the Switchboard Bus voltage. Refer to Section 4.9 for the implications with ADC or NBC methods for Bus-bar supply changeover.

Downstream POC SubstationsThe Substation locations are also shown in Attachment F. POC and associated RRE real estate has ended up very crowded so that the unclassified “safe” areas are not very large and extensive; hazardous areas are not too far away. Also the 200m Exclusion Zone for the Pipeline Corridor cannot be avoided easily as a large proportion of POC is within this area.

The important POC main 33kV Distribution Substation feeding four other Substations is in this zone; three of these are located similarly. Consequently in order to reduce the risk to the buildings, equipment and personnel, the FEED has specified all the Substations to be blast-resistant reinforced-concrete type of construction.

Incoming Supply Cabling The main instantaneous protection operates fast if it performs correctly and reliably. However if it fails to operate and trip the breaker, the backup overload protection is required to be capable of operating in less than one second as the Bus-bar is rated for this time. The incoming Supply circuits HV cables shall preferably match this Bus-bar and so be rated for greater than 0.25 sec, otherwise expensive cable damage will result when the backup device has to disconnect the short-circuit and initiate the supply changeover.

Procuring and replacing buried cabling can take a lot of time. There can also be reduced production for this time if the remaining Transformer is overloaded and load reduction is then necessary; however this may not be practical and then the total production can be lost.

3.10. ETAP Adequacy Study

Consequently IBCL (or similar) need to perform a formal transient (dynamic) system study using ETAP to establish how much Grid Station Reserve power is needed in order that the Process (or any individual Unit) normally does not trip on TAKREER Process Plants. The Switchboard Bus-bar breakers changeover sequence (refer to APPENDIX Section 5) and associated motor IPCS Re-acceleration/ Restart scheme (refer to Section 3.5 and 4.5) are at the heart of the transient performance.

The adequacy of Supply Authority power supply will be checked as part of this; an Adequacy Study/ Report is generally requested in Clause 3.8 Electrical Systems of the Statement of Requirements (SOR).

Strictly study of the problem Ruwais Grid power supply is outside POC Scope of Work as the Option 3B “modified” choice by TAKREER selects the Gayathi Road Substation power supply as the source for POC FEED.

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4. POWER DISTRIBUTION CONCLUSIONS

4.1. Power Factor

The costs for extra PFC equipment and its installation can potentially be avoided without any risk and quite simply. Tie-in Report Option 3B shall be implemented ASAP so that the CBDC load is removed from Ruwais Grid Station. The implementation of Option 3B (refer to Section 3.8 above) can help prevent the need for extra PFC equipment. The necessary reconnection of some existing RRE load to another source of supply (refer to Section 4.2) can potentially lead to eliminating the need for extra PFC equipment.

Additionally there is some generation available on GUP to help with Power Factor Control (PFC). This can certainly help to meet the TRANSCO requirement of 0.95 for the minimum Power Factor on Ruwais Grid Station.

4.2. RRE Substation ‘0’ Loading (33kV Switchboards)

The three pairs of RRE Substation ‘0’ (SS 000) 33kV Transformers are inadequately sized. Tie-in Report 5652-STU-EU-001 “Attachment 6- RRE Overall Load Summary” clearly identifies and enumerates this technical problem that needs a practical solution ASAP. Load figures for the CBDC Tie-ins have even increased since the Study was issued, exacerbating the problem for one pair of the three sets of Transformers and associated 33kV Switchboard.

The Transformers are NOT 100%-rated so do not comply with DGS-EU-001 Clause 11.8.c. They unfortunately still reflect the RRE FEED as their sizing has not been developed to suite the increase in load during the EPC design phase. The EPC Contractor has NOT fulfilled his Contract electrical requirements.

This is an important lesson-learned item that will directly affect production if not rectified. Using a Continuous Load diversity factor of 1.1 in the FEED can go a long way to ensuring that TAKREER do not have this problem in the future.

A plan to transfer CBDC loads from RRE Substation ‘0’ to the Option 3B location of 33kV GIS in the new POC 220kV FEED Main Substation will help resolve the power shortage at Substation ‘0’ with one transformer circuit out-of-service (refer to SS-000 Overall SLD 5636-2028-EU-E-031A). This helps the one RRE 33kV Switchboard 1028-HMS-000C only, not the other problem Switchboards -000A and -000B. However it does not eliminate the shortage, based on latest load figures available. Undesirable load reduction still looks likely with loss of some production at the least, even after CBDC loads are moved. RRE “as-built” load figures are information that is presently awaitedfrom the EPC Contractor.

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Consequently Tie-ins of some installed RRE 33kV load to another source need to be considered but separate from the Ruwais Grid Station source. There may still be some spare capacity available derived from generation in the GUP Phase 3 from their latest 132kV or 220kV Switchboards (refer to Attachment C). Certainly there will be capacity available on the Gayathi Road Substation at 220kV (refer to Attachment E). ADWEA may also be a possible source or a small Power Station fed by RRE surplus steam (if ADGAS also require power to develop an adjacent site).

It must be emphasized that this RRE 33kV power shortage problem although reasonably urgent does not now form part of POC work but it does need a solution ASAP.

4.3. Additional POC 220kV GIS Main Substation

Incoming Feeders from TRANSCO A local 220kV breaker is now required by TRANSCO before each Transformer in this POC 220kV Main Substation (SS 200) to facilitate local isolation as the Gayathi Road Substation is quite distant. If a 220kV problem occurs, access to TRANSCO Grid Stations is logistically difficult and time consuming with permits, etc. Such local means of isolation is in TAKREER’s interest (M-BL-PL-5652-1.7.1-0128 MOM in Abu Dhabi dated 13th November 2014 refers) as it can save much time; it is required that the POC 220kV supply problem is resolved quickly and the supply returned to normal ASAP as such downtime is money to TAKREER.

This extra local isolation for SS 200 obviously comes at a cost. However it has been possible to change TRANSCO’s mind regarding the second old GUP circuit; they will no longer use the bay to re-enforce their network. As a result of the Electrical Team meeting with TRANSCO, both 220kV bays D01 and D04 are available for TAKREER use (see above-referenced MOM of 13th November 2014). So a new 220kV GIS Feeder Breaker with protection/ metering panels (Section 3.3 – Incoming Feeders from TRANSCO) is not now required for bay D3 at Gayathi Road Substation; TAKREER can remove this Breaker cost from the Budget Estimate.

Main Substation Location The technical practicalities of volt-drop and physical location of a suitable tie-in point to existing EPC design route for CBDC 33kV cabling locates this new intermediate 220kV Main Substation (SS 200) away from largest POC area and puts it especially close to RRE Substation ‘0’ (SS 000) to allow easy shifting and tie-in of these 33kV CBDC power supply cables. No extra cable is required as route length is shorter.

The FEED concept is that this Main Substation is located at a safety distance of 85m from the nearest Cracked LPG Storage Sphere (1041-D-016), considered a more-than-adequate safety separation as it has a contingency above the 60m in DGS.

It is also located adjacent to SS 000 within the existing TAKREER Battery Limit. So the cost of big land reclamation from adjacent ADGAS area has been saved (assuming no

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steam generation in this area also), certainly less than the proposed 50m shall be necessary in this area. TAKREER have saved this large cost from the Budget Estimate.

The feeder cables route to the main POC ARDS area locally requires the fence and fence lighting to be relocated; less than 10m of ADGAS land will be sufficient. The exact layout and location for this extra Substation can be EPC designed/ developed to suite.

HV Cabling Lengths The location of this Main Substation for POC adjacent to Substation ‘0’ produces a cost saving of 42.6 Km length of 1200mm2 220kV lead-sheathed single-core cable, taking re-use of existing cable into account. TAKREER can remove this cost from the Budget Estimate.

However this is balanced against the cost of 27.6 Km of the new 220kV cable to the same spec, plus 43.2 Km (12 x 3.6) overall total buried length of 132kV cable (50% sized at 630mm2 and 50% sized at 400mm2 csa). However the routes chosen by the Electrical Team for these 132kV and 220kV feeders has eliminated the need for any costly boring for cable installation underneath existing facilities. TAKREER can remove this cost for electrical soil boring from the Budget Estimate.

4.4. The Supply Authority

The Supply Authority is TRANSCO and they have the power to disconnect any consumer. TAKREER must limit their Motor Contribution, comply with any requested Tie-in PF and cause no overload to TRANSCO Ruwais Grid Station 220kV Bus-bars. These conditions are inter-related but generally must be met. Unfortunately this can involve the downstream 3rd Party consumers such as Borouge, who potentially have a large unknown recent Motor Contribution. TAKREER may need to control the PF in-house and supply any extra PFC control equipment found to be necessary.

The connection of a future Project (e.g. CBDC) can be sensibly ruled out for Ruwais Grid Station for technical reasons based on data in the FICHTNER Study Report and prudent load figures – a realistic Reserve power margin (refer to Sections 3.6 and 4.6 for detail) is essential and after its allocation, there is effectively no spare capacity available. Ruwais Grid Station is “effectively overloaded”.

With proper Electrical Distribution System planning foresight and action NOW, the overload, Tie-in PF and Motor Contribution situations can hopefully be managed and avoided.

4.5. IPCS Motor Re-acceleration/ Restarting

No-Break Changeover (NBC) and Re-acceleration There is extra cost involved for Substation equipment for NBC operation of the MCC power supplies linked to the IPCS Re-acceleration scheme; the MCC Switchboards become smaller but an extra one is required. This cost is easily recouped during the life

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of the Plant. Much less tripping of the Process Units with the increase in production and the improvement in quality is what pays for it. So NBC being specified for the MCC Switchboards during FEED is a sensible technical decision that can reap the benefits.

Automatic Dead Changeover (ADC) and Restarting The IPCS Re-acceleration/ Restarting scheme for a Switchboard’s running motors is best viewed as the backup system to try and ensure continuity of the Process in the event of long (i.e. greater than 250ms and up to one second or more) voltage loss/ dips due to local electrical short-circuit faults or any other breaks in the supply; one such definite cause of a break being a wrong selection for the changeover sequence of MCC Switchboard breakers, namely ADC is a bad (most say incorrect also) choice. Motor voltage loss can then be in the order of minutes for some motors with consequent undesirable effects to Unit performance and output quality; a Unit trip is very probable.

The Choice of NBC or ADC for MCC Switchboard SpecificationConsequently the NBC is a very sensible choice for at least the safety “Electrical HAZOP” reason (refer to detail in Section 5.1 Appendix) and also in order to ensure continuity of supply to all the motors especially. The NBC has the big benefit of virtually guaranteeing production continuity by avoiding unnecessary trips of complete Process Units. This tripping can be a consequence of ADC operation and the ensuing prolonged loss of the motors due to the intentional disconnection of supply by the changeover sequence of the ADC.

The ADC switching operation of MCC power supplies will always stop the small motors and associated pumps, etc. and such small motors in particular are not normally part of automatic IPCS Reacceleration/ Restart control schemes. However loss of these small drives can contribute to a delayed Unit trip and certainly affects product quality.

Note: An “effectively overloaded” power supply can also produce the same effect as ADC action by dragging the supply voltage down to a low level towards the zero volts of the supply break always associated with ADC. If the overloaded supply does not recover after a reasonable delay has elapsed, then under-voltage relays will briefly operate/ initiate suitable electrical shutdown actions.

4.6. Reserve Power

TAKREER Power Station (GUP) Some of GUP power is now provided by Ruwais Grid Station. A 10% overall Reserve power margin is the normal minimum design value required to ensure the Re-acceleration/ Restarting of the motor loads under all circumstances. A greater margin than even this 1.1 factor is preferred to reduce the probability of Process outages. Typically RRD was initially designed with up to 20% Reserve power being available (the so-called Spinning Reserve in GUP provided by running the “spare” Main Generator on-line).

This was shaped by the choice of standard machine ratings/ frame sizes available for the GUP Generation. Now GUP has to import power due to expansion of the power system loads but with no increase in main generation capacity presently. GUP has also

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changed its Distribution System as a result of the FICHTNER Report and all the Main Generators are not now connected to a single Bus as part of this GUP 3 expansion. New 33kV, 132kV and 220kV Switchboards were also installed.

TRANSCO Grid Station and Substation Ensuring that POC and CBDC power is derived from Gayathi Road Substation ASAP, as the intent of the Tie-In Report Option 3B, will contribute immensely to transient performance and produce reliable POC and CBDC Plant operation. There is plenty of Reserve power available there for motor re-acceleration.

Additionally relocating CBDC source of power will increase (theoretically, at least) the Reserve margin on Ruwais Grid Station for re-acceleration of RRE and thus help the Plant reliability. Fast electrical system transient performance is an important factor in reducing Process trips.

GeneralToo many RRE Process trips can be an indication of a TRANSCO power supply with no or little Reserve, effectively an “overloaded power supply” as there is insufficient Reserve margin allocation, so this shall be avoided.

Sensible planning and design of TAKREER electrical distribution system allowing for adequate Reserve capacity is the key solution. There has clearly been insufficient emphasis on this in the past so the consequence can be costly production shortfalls or in the worst case no production.

4.7. 220kV GIS Switchboards

A minimum 10% short-circuit margin for a Bus-bar for the worst-case conditions is normal Design Practice for safety reasons as GIS can age. TRANSCO are sensibly concerned about the margin for their Ruwais Grid Station main 220kV Buses. Certainly the 50kA FICHTNER Report lesson-learned shall apply to any future post-FICHTNER EPC 220kV GIS Switchboards, such as for POC Project. It is after all not too far downstream from the TRANSCO Network.

It is not beyond the realms of probability that an existing TRANSCO Grid Station may need uprating to 50kA. The present rating for the Bus-bars of 40kA for 3 seconds surely equates to >40kA for 1 sec, subject to clarification with the Manufacturer. It may be possible for this revised Bus-bar rating to compensate for increases in the TAKREER Motor Contribution since the FICHTNER Report, especially from 3 rd Party downstream consumers such as Borouge 3. This can form part of an ETAP Power System Adequacy Study (Section 4.10).

POC and CBDC cannot increase the TAKREER motor fault contribution to the problem TRANSCO Ruwais 220kV Bus-bar if they are not connected to it. So the shifting and tie-in of CBDC power supply cabling to the POC Main 220kV Substation (Section 4.3) will be welcomed ASAP.

4.8. Option 3B (Tie-in Report)

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Option 3B in FEED Engineer’s Electrical Tie-In Report is best implemented ASAP as it moves the CBDC and POC loads onto Gayathi Road 220kV Substation, where there is plenty of spare capacity. The Ruwais Grid Station 1020MW in the FICHTNER Report does NOT include CBDC and POC Projects. Consequently connection of either is sure to “effectively overload” the Ruwais Grid Station when all related matters in this Report are taken into account.

The tie-in connection moves to Gayathi Road Substation will contribute immensely to motor transient recovery and produce reliable Plant operation for CBDC/ POC. There is plenty of Reserve power available here presently. Attachment A sketch highlights Option 3B and is included at the end of this document. It has been developed as shown on Attachment B Sketch and further modified as Attachment D. The proposed POC 8No Distribution Substation locations can be viewed in Attachment F.

Consequently the Tie-In Report Option-3B best action and solution for Ruwais Grid Station:- a) Essentially helps to prevent overload above its 1000MW nominal capacity (refer to

detail in Section 3.4).b) May not reduce the need for extra PFC equipment on the Consumer side as a better

Reserve power margin is really needed to improve the IPCS Restarting System for the connected motors in RRE especially (refer to Sections 4.1 and 4.5).

c) Reduces the Motor Contribution on the TRANSCO Ruwais 220kV GIS Bus (refer to Section 4.7).

d) At Gayathi Road- it produces an overall power Reserve margin much greater than 10%, which is preferred for fast motor Re-acceleration and the consequent reduction in unnecessary Process/ Unit trips (refer to Attachment E).

Since the Tie-In Report was issued, there has been a change in EPC design Peak Load for CBDC to 122.6MVA. (Ref: CBDC Overall Load Summary 5636-REP-EU-101). This represents a 29% increase from the value stated in the Tie-in Report.

Note 1- It may be easier to increase Item b) Reserve power available by the transfer of some RRE 33kV load from Ruwais Grid Station source in order to reduce the probability of Process trips (refer to Sections 4.1 and 4.2).

Note 2- The Item d) applies to TAKREER CBDC (assumed) and POC Projects only presently (refer to Sections 4.1 and 4.6).

4.9. Downstream MCC Switchboards Design

Normal MCC Switchboard Considerations Loss of a Switchboard is a major catastrophe and shall be avoided by correct modern FEED/ EPC design concepts. It must be remembered that the manual breaker switching actions of local Substation Personnel are not easily controlled/ supervised and mistakes can be made. Switchboards can be designed to invalidate the consequences of any such unsafe action or practice. The safety of personnel and equipment safe-guarding/ protection shall be the main requirements. Refer to Sections 5.4.1 to 5.4.3 (attached

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Appendix) for detailed conclusion discussion on the design of MCC Switchboards and Electrical HAZOP considerations.

ADC concept for an MCC Switchboard has a slower overall electrical supply changeover sequence with a supply break. This can result in unpredictable Process trips/ shutdowns that can be caused by the time duration of the intermittent loss of electrical supply plus the subsequent sequence delays of IPCS Restart system timer for each motor.

Also at the Field level, motors that are seen by Operations personnel to stop and then restart without their intervention can be disconcerting. An unsafe incident is not ruled out and this is another obvious Electrical HAZOP matter with ADC only.

For the 415V and 3.3kV Switchboards, the cost of this lost production or the possible mechanical equipment damage (on automatic re-connection of motors) can be spent on avoiding unnecessary supply interruptions by ensuring that the prudent Switchboard alternate NBC design option is specified in FEED at the beginning of a Project.

Europe considers this NBC approach to be cost-effective over the life of a typical Plant and European Companies generally extol its virtues. Most Process trips can be avoided by sensible electrical Switchboard engineering design at the start of a Project when proposed and chosen in the FEED. Also such a safe “worst-case” EPC design is the best solution to satisfy the Insurer of the Plant.

With this NBC design, the Switchboard Bus-bar is rated for the maximum prospective fault current, a safe scenario for a breaker changeover caused by high-energy fault overcurrent and not just due to a simple loss of a supply; the Bus cannot be damaged. This is unlike the higher probability of Bus-bar damage with the ADC design of MCC Switchboard where the Bus is not rated for the maximum possible short-circuit fault current.

Emergency SwitchboardsBy the very nature of their loads, Emergency MEP Switchboards are required to be dual transformer-fed with NBC supply transfer being specified, as possible with a standard-design of ATS Switch at this LV voltage level, subject to EPC equipment design check; also a local EDG is to feed the Emergency Bus.

Emergency SEP Switchboards shall also be fed from local 11kV Supply Transformers (415V feeders if no 11kV available) in the Substation as with an MEP plus redundant LV cable feeders from the associated remote MEP to ensure a reliable SEP incoming supply.

The connected emergency loads include Normal/ Emergency Lighting and ARDS cooling-down motor-driven equipment, including many small motors; these LV motors especially must be kept running with no unnecessary stoppage during an Emergency Shutdown so, as there is generally no automatic restart system for them, the NBC/ ATS philosophy is very prudent and necessary. In any case, motor Restart delays cannot be tolerated for such an important Shutdown situation.

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It shall be noted that SIS, UPS and Battery rooms have HVAC backup split air-conditioners as part of the POC FEED. These are powered from the Emergency MEP and SEP Panels. It is noted that RRE and CBDC have not been EPC-designed with any backup Emergency HVAC system; a lesson-learned from TAKREER site personnel.

MCC ContactorsA sustained dip in the supply voltage to a motor will cause the Contactor to drop-out and the main-poles to open the motor circuit and the motor to stop. However any intermittent dip, as with an NBC supply changeover, can be tolerated by a suitable drop-off delay for the motor Contactor coil; it can be “slugged” to produce a short delay, e.g. by fitting a suitably-sized capacitor across the coil.

Also at the 3.3kV level, it is quite common for the Contactor coil closing mechanism to mechanically latch closed. Such larger motors are normally considered more important to the core Process, so need to remain on-line and running reliably without unnecessary trips. The Contactor is then required to be positively tripped/ opened via its trip coil by an under-voltage relay timer if a sustained dip is detected, e.g. pneumatic timers are suitable for this service.

Consequently short-term dips in an NBC supply system before the healthy supply takes over fully and seamlessly do not stop any motors; there is no unnecessary opening of the individual Contactors. The opposite occurs with ADC Specification Switchboards as the ADC produces a longer sustained dip/ break.

The Choice for Normal and Emergency Switchboards In conclusion, ADC is not inherently safe as the degree of safety is tempered by an injury/ damage risk situation more probable than true “double-jeopardy” (refer to Section 5.1 Double-Jeopardy) that can arise with the Switchboard Bus-bar. It is not 100% safe for Operations personnel so it is a "no-brainer" choice in this modern day and age. NBC is 100% safe "by design". This safety is worth paying for as it can save lives/ injuries and prevent unnecessary equipment damage. It is the logical Electrical HAZOP choice that is supported by “the weight of evidence” throughout this Report.

At the same time NBC eliminates unnecessary Unit trips caused by any breaks in supply (as always produced by ADC) by ensuring MCC supply continuity. As an NBC bonus, all the small motors remain running continuously to ensure the quality of the Process product and contribute towards smooth continuity of Unit production.

The obvious conclusion is that all the Normal 415V/ 3.3kV MCC Switchboards and Emergency 415V Switchboards on POC shall be specified as NBC-type. The Budget money saved on the expensive 220kV GIS Breaker (Section 4.3 - Incoming Feeders from TRANSCO), 220kV cabling and cable boring (Section 4.3 - HV Cabling Lengths) and ADGAS land reclamation (Section 4.3 - Main Substation Location) is best spent on the cost-effective NBC-specification MCC Switchboards. These NBC Switchboards will in any case eventually pay for their extra cost over their lifetime by reducing losses in production and trips.

Incoming Supply Cabling Backup protection for the incoming cables is as important as the main protection device. The lead sheath on the TAKREER cables can do nothing to prevent short-circuit

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damage as its function in buried cable is to protect the cable against the effects of the environment including corrosion from hydro-carbons, water, etc. However any backup device cannot protect the cable if short-circuit sizing is for less than a one second, then strictly an insufficient time; any other short term rating (e.g. t=0.25 sec) for the cable is insufficient for the heat energy produced by the let-through of the short-circuit current. A cable sized for one second rating is best chosen with copper csa increasing accordingly. However the cable will last for the lifetime of the Plant.

In conclusion the incoming Supply cabling needs to be adequately rated to suite the slower speed of backup protection devices and match the 1 second fault duration used for MCC Switchboard Bus-bar design. Rating otherwise is a false economy when the cost of the downtime due to cable damage leading to lost production is considered; the rating of the remaining Transformer inevitably may not reflect 100% as-built load due to insufficient EPC design development to the detail required by TAKREER DGS Standards, so production inevitably has to be reduced.

4.10. ETAP Adequacy Study

An ETAP study needs to be performed on the TAKREER electrical distribution system(s). Good electrical system transient performance for the start-up of a large motor (or an equivalent-sized group of motors) is an important factor in reducing Process trips. The overall Grid System can be required to start several large motors or groups simultaneously so an adequate Reserve margin is required.

The adequacy of 400/220kV power supplies in relation to the associated motor Restart schemes need to be checked as part of this, as any “effectively overloaded” power supply can affect the number count of Process/ Unit trips. Ruwais Grid station needs a “fit-for-purpose” Adequacy Study/ Report check in view of all the new Project loads since FICHTNER Report that have reduced the Reserve Margin, including new loads added by POC Project to RRE; these loads will now be increased further by expansion of the RRE/CBDC SRU system, ultimately allowing all its Sulphur trains to operate fully to stop ‘acid gas flaring’ when POC SRU has a problem. Important power supply recommendations may need to be made.

Borouge 3 Project and other recent downstream TAKREER-supplied consumers can further increase the problem Motor Contribution at the TRANSCO Ruwais 220kV Bus-bars (refer to Attachment C and Section 3.7). Plant expansion has taken place in the last 5 years since the FICHTNER Report. The Motor Contribution from 3rd Party TAKREER consumers downstream warrant further investigation in a full ETAP Study that considers the overall TAKREER system(s) including all 3rd Party consumers.

A complete listing of all as-built data is needed for all the connected users of TAKREER power. Site investigations out in the field will be needed to cross-check/ verify the critical data for the studies, including installed Switchboard ratings. “Missing motors and loads” are often found during such Site Surveys.

Subsequent to Option 3B Tie-in decision, the POC Project Study elements are only applicable to TRANSCO 220kV Gayathi Road Substation. Ruwais Grid Station studies

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are now not part of POC Scope of Work but it is obvious that Ruwais studies are needed.

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APPENDIX

Electrical Matters related to TAKREER Specification

“DGS-EU-001- Electrical Design Guidelines”

5. APPENDIX- MCC SWITCHBOARDS DESIGN AND THE CU BUS-BAR RATING

5.1. Requirements of the DGS-EU-001 Clause 11.8.d

Design Guidelines Revision 2 (or 3) Clause 11.8.d reads-

“All 3.3kV and 415V switchgears shall be operated with bus section breakers normally open. Automatic dead changeover and manual live changeover facilities shall be provided. Each process unit substation shall be provided with a turnaround power centre (TPC) dual fed from main 415V switchgear with automatic changeover facilities. The loads …”

Automatic Dead Changeover (ADC) The most important part of the Clause 11.8.d is the 2nd sentence concerned with TAKREER Switchgear equipment operation to facilitate “Automatic dead changeover (ADC) and manual live changeover” of the incoming feeder supplies to the 415V and 3.3kV Process Motor Control Center (MCC) Switchgears. Such an electrical requirement for a Switchboard follows American Design and Engineering Practice.

Associated Operation Practice is “with Bus-Section (Bus-Tie) breakers normally open (NO)”. It is assumed that TAKREER legacy Plants are designed to meet these requirements at 415V and 3.3kV, for example the original Ruwais Refinery (RRD).

With 415V and 3.3kV Switchboards, it is generally the operating practice to run both the 100%-rated Supply Transformers at 50% loading, the double-ended mode of operation applicable to both ADC and NBC operations. The single-ended mode of operation (one 100%-rated Supply circuit in service with Bus-Section breaker closed) is an abnormal operation and only occurs when one Supply Transformer circuit is faulty and awaiting remedial work. If the remaining Transformer consequently becomes overloaded then load reduction with loss of some production ensues (refer to Section 3.2 for a typical case).

On an older/legacy TAKREER Switchboard, inadvertent manual closure of a Bus-Section breaker tying the two live Bus-bars together can lead to Switchboard damage as the “double-jeopardy” risk situation then happens (refer to Double-Jeopardy below). Operators/ Maintenance Personnel trained in other Plants may well be used to such a switching action as many Operator Companies worldwide

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routinely allow such an operation because with NBC philosophy Switchboards, this is allowable and no Bus damage ensues.

No-Break Changeover (NBC) The “no-break” principle is already used for TAKREER 11kV MCC Switchboards as Clauses 11.8.b and Clause 11.8.c (100%-rated feeders) of TAKREER Standard DGS-EU-001 with the only difference being that the Bus-Section breaker operates NC (refer to Section 5.3.1 below). Similarly the TAKREER 33kV, 132kV and 220kV Distribution Switchboards on GUP follow the same philosophy of operation as such 11kV Switchboards. This follows traditional European/UK Engineering Design Practice. Higher Bus-bar short-circuit ratings requiring extra Cu are needed for the 415V and 3.3kV Switchboards in order to allow NBC of the supplies but the Process benefits immensely.

In Europe, it is not Recommended Practice these days to design an MCC Switchboard in the outdated ADC manner with its inherent reduced short-circuit capacity rating for the Bus-bar that is below the maximum prospective fault current, albeit for a perceived “abnormal” operating condition that in practice does happen quite frequently due to unprofessional EPC detailed design. A cheaper under-rated Bus is a completely false economy. It is not considered safe by Electrical HAZOP meetings, especially as the manual Bus Supply/ Section breaker switching actions of local Substation Personnel are not easily controlled/ supervised and errors of judgment/ mistakes can be made.

With a sensible rating design of the Bus, any Operations mal-function/ mal-practice (automatic or manual) cannot damage a Switchboard (assuming that main or back-up protection devices perform reliably) as the Bus-bar is capable of sustaining the maximum prospective short-circuit current of the two Transformers that are effectively connected in parallel, either momentarily or longer to suite any Operations requirement. This is the main basic principle of NBC design.

This is owing to the safe “Electrical HAZOP” NBC design of MCC Switchboards in the first place, generally following European IEC Practice for the short-circuit rating of its copper Bus-bar to suite the required paralleling of the NBC incoming power supplies to the MCC.

This additionally ensures that there is no loss of supply to the Bus, so all the active motors continue running and stay in synchronism with the supply. There is consequently no possibility of mechanical “kicks” to damage shafts, pumps, compressors, etc. Unit production will continue as normal without any unnecessary interruptions.

Double-JeopardyThe HAZOP definition of 'double-jeopardy' - "Risk of loss or injury arising from two sources/ occurrences present at the same time".

If one problem source is permanently present, e.g. an under-rated Switchboard Bus, then there is a much higher probability of a long-term “loss of supply”; it is almost inevitable. A single problem (such as a short-circuit fault when the Bus supply

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Transformers are effectively operating in parallel) is all that is required to enact the perceived 'double-jeopardy' HAZOP risk event.

This highlighted 'double-jeopardy' electrical example concerning an ADC Bus is a miss-selling of the facts concerning the ADC Switchboard type. It is not a true 'double-jeopardy' situation as there is an inherently greater risk element for a Electrical HAZOP problem occurring, as one “..source..” is already existing and inbuilt into any ADC MCC Switchboard.

Consequently the Bus is a very real and obvious weak point in an ADC Switchboard but this design shortfall is not present with the alternate NBC type of Switchboard, The selling of the ADC product is not good practice and very un-professional for HAZOP reasons, so such assemblies are not built in Europe normally these days.

The choice of the NBC “No-Break Changeover” spec produces the end result of superior-quality fully-fault-rated Switchboards, more reliable Process Units and better quality Process end-products.

5.2. Clause Requirements for Turnaround Power Centre (TPC) Switchboard

It is noted that each existing Ruwais Turnaround Power Centre (TPC) presently operate to European “no-break” Practice and this ensures no loss of lighting when either TPC main LV supply has an electrical problem. This continuous/ no-break lighting is for Personnel safety reasons, utilizing the make-before-break (i.e. ‘over-lapping contacts’ principle) switching rule in the switch design.

There is an Automatic Transfer Switch (ATS) to automatically, rapidly and reliably control the changeover of the 415V 3-phase supplies without the intervention of Operations personnel; this eliminates associated safety issues and ensures no unnecessary delays.

Note: There are no Process loads on a TPC, by design.

5.3. Operations and Engineering Design Working Practices

5.3.1. 11kV Switchboards

At the 11kV MCC Switchboard level, DGS-EU-001 Clause 11.8.b requires that the Bus-Section breaker operates normally closed (NC). Normally the incoming Supply breakers operate NC as well and this really needs to be stated in this Clause as a Client requirement. This requires that an 11kV Switchboard be designed for the higher short-circuit fault current associated with the two Supply Transformers being normally effectively connected in parallel. Loss of one Transformer circuit produces no loss of supply and any motor loads remain in synchronism with it. There will be no possibility of any out-of-synchronism “kick” to associated mechanical equipment, as the supply does not need to return; it remains on the Bus-bar.

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This effective paralleling is inherently a safe Design Practice where there is no possibility of a “double jeopardy” risk situation arising as the Bus-bar shall already be designed for the “worst-case fault”; the integrity of the Switchboard and the safety of Operations personnel is not put at risk. Consequently it is agreed that POC 11kV Design shall comply with this Clause, as done in RRE and CBDC Projects.

Large 11kV motors can retain their residual voltage for some time if their supply is disconnected and this can delay re-connection until conditions are suitable. However these are the very loads that for Process reasons really need to stay on-line whilst an electrical disturbance is rapidly and automatically cleared. Even big 3.3kV and 415V motors can have reasonably long voltage decay times.

So sensibly all the bigger motors need to remain on-line and energized to help prevent Process trips caused by the motor breaker/ contactor reclosing delay (required by “automatic dead changeover” scheme) needed to ensure that the residual voltage has dropped to a safe level, typically 20% or less; this contributes to unduly lengthy overall motor Restart times.

Unnecessary Process trips can be avoided by “worst-case” Switchboard FEED design and the correct choice of the changeover sequence of the Bus-bar Supply/ Section breakers. Additionally the motors can ride through short-term voltage dips in a similar manner if they stay on-line as long as possible. Section 3.6 describes another dip condition regarding inadequate Reserve power margin that can affect MCC Switchboards and contribute to unnecessary Process trips in TAKREER Plants.

The POC 11kV Switchboard short-circuit fault calculations shall check-out as consistent with the parallel incoming circuits. RRD 11kV Switchboard design and its operation may need to be further investigated to ensure that both are consistent and safe. It is a fact that the Bus-bar of a Switchboard can be upgraded to a greater standard short-circuit capacity, however an enforced shutdown is normally necessary in order to install.

Possibly the required higher electrical fault rating is not practical. Then fault-limiting reactors can be retro-fitted. However it is better to implement safe “Electrical HAZOP” Design at the beginning of a Project, as prevention is better than cure.

5.3.2. 415V and 3.3kV Switchboards

Supply Breakers Changeover OperationThe electrical Operations personnel who maintain and operate the Switchboards at a local level will at various times work in different Plants within TAKREER. Presently they are familiar with certain Working Practices for the older main (normal) 3.3kV and 415V Process MCC Switchboards. These relate to the fact that the older 415V and 3.3kV Switchboards have been designed with limited short-circuit current capability and a different

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breaker changeover procedure to suite. This short-circuit rating effectively cannot be increased sufficiently for these 415V Switchboards to match any paralleling of the existing Transformers, so the associated older Working Practices must remain here. However manual Operator error is NOT precluded.

It is noted that the latest GUP Expansion (Phase III) Project has implemented supply changeover, effectively utilizing ATS principles allowing automatic NBC to European Practice for the Bus-Section breakers on at least the 33kV, 132kV and 220kV Switchboards, agreeing with the Design Practice for a typical TPC described in this DGS-EU-001 Clause 11.8.d. However associated Bus-Section breaker practice is operating in normally open state (NO as 415V/3.3kV MCC practice) unlike 33/132/220kV NC practice.

The NBC principle means that there is no supply re-connection required (unlike with ADC), so no subsequent unnecessary Restart delay is introduced. The associated Process Unit will be more stable and less prone to Process trips.

This NO Bus-Section breaker is also true for RRE and CBDC at 415V and 3.3kV levels but the changeover sequence for the Supply and Bus-Section breakers is different, as the ADC principle applies here. The re-connected motors can be out-of-synchronism with the returning supply if the re-connection delay is too short, giving rise to the possibility of twisted shafts from sudden impulse loading, the severity depending on the electrical angle of displacement.

If the overall motors startup delay is too long (including long subsequent motor Re-acceleration steps), then Process sub-systems can easily trip. An “effectively overloaded” power supply can produce this result, especially with the “automatic dead changeover” design of existing TAKREER Switchboards that requires the re-connection of the motors. This is strictly unnecessary, causes problems and should be designed out during the FEED phase.

Bus-barsSwitchboard Bus-bars are best designed for the higher short-circuit current (the maximum prospective fault current) associated with the effective paralleling of Switchboard incoming electrical Supply circuits, as for an NBC supply transfer action. This is the safest approach possible. This is a fast action if the main instantaneous protection operates correctly and reliably.

Additionally this increased short-circuit rating for the Switchboard specifically allows for the very possible scenario of the two incoming transformers operating in parallel for an extended time. This can happen owing to an insufficient margin in the Switchboard EPC design to cover unexpected Future loads. However this parallel operation is in practice effectively ruled out for continuous operation by the risk factor if the Bus-bar is not specified to withstand such a short circuit scenario. It is just asking for trouble so a short-circuit will happen if operated in this manner.

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Such Switchboard operation is really too risky for ADC Switchboards, as used in RRE and CBDC plants. Sections 3.2 and 4.2 contents become very relevant in this context as a single RRE 33kV transformer can easily become overloaded. This ATS “no-break” principle ensures that Switchgear Bus-bar design is inherently safe and follows modern European Practice. So there is NO weak link then in the electrical system design, thus making it very reliable. This is referred to as “worst-case design”, i.e. the Bus-bar design shall be for the “worst-case”, referring to the maximum value of the short-circuit current in this case.

As a result, long-term loss or disruption of electrical supply to 415V/ 3.3kV Switchboard loads caused by over-stressing of the Bus-bar will not occur to any such a Process Switchboard and its motor loads, ensuring that the Plant continues in operation without any unnecessary long-term Process Unit shutdown. This saves TAKREER the costs of lost production associated with the long system downtime that is practically certain with the older Switchboard designs after a heavy fault current causing Bus-bar damage.

5.4. Conclusions related to MCC Switchboards

5.4.1. 11kV Switchboards

DGS-EU-001 Clause 11.8.b indicates that 11kV Bus-Section breakers operate normally closed (NC). Normally the two incoming Supply breakers operate NC as well when there are associated healthy Transformers. Consequently Switchboard Bus-bar short-circuit calculations shall reflect parallel incoming Supply Transformers situation with Clause 11.8.c 100%-rated Transformers, plus contribution from the connected motor loads.

11kV Switchboard matters in common with the higher HV voltages of 33kV, 132kV and 220kV can be found in Section 5.4.3. 11kV Switchboards, in common with higher voltage HV Switchboards, employ a form of NBC for the Supply and Bus-Section breakers to ensure continuity of distribution supplies. The “no-break” is true for existing and POC HV (including 11kV) Switchboards.

5.4.2. 415V and 3.3kV Switchboards

POC Project shall preferably agree with modern automatic NBC for the Supply/ Bus-Section breakers in the 415V and 3.3kV Switchboards, following the principles of a static ATS switch, as used in TAKREER 415V TPC Switchboards. This “no-break” principle is the best choice to ensure safe supply continuity to the electrical motors, but it must be with Switchboard Bus-bars short-circuit rating designed-to-suite i.e. allowing two transformers in parallel, as 11kV Switchboards design (Section 5.4.1).

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This is very safe Facilities design ensuring that an unsafe “double-jeopardy” Switchboard consideration (Section 5.1 Double-Jeopardy) cannot happen; it can be described as foolproof as Operator abuse cannot produce an unsafe condition.

However if TAKREER (Abu Dhabi) lines up with previous practice on RRE, CBDC and RRD, the “double-jeopardy” Switchboard short-circuit capacity consideration will exist and there is the probability that at least the Switchboard Bus-bar can be damaged. Previous RRE/ CBDC/ RRD Projects are in agreement with the DGS-EU-001 Rev-2. This represents a Switchboard requirement with an unnecessary risk element designed in. There is a Switchboard accident waiting to happen with each and every one of existing Takreer 415V/ 3.3kV MCC Switchboards.

5.4.3. Switchboard Bus Supply and Section Breakers- General (All Voltages)

NO (normally open) and NC (normally closed) shown against Bus-Section and Incoming circuit breakers on the Key Single Line Diagram does not tell definitively the principle used for rating/ specifying the Switchboards. However a new Switchboard can be engineered to suite all Working Practices and Principles. A safe “worst-case” design is the best solution to satisfy the Insurer of the Plant.

However an EPC Contractor needs close supervision to ensure compliance, especially if EPC design is performed in a non-EU (IEC) country. This is especially important for an HV (11kV, 33kV, 132kV or 220kV) Switchboard, where the required Clause 11.8.c 100%-rated incoming Transformers are effectively paralleled continuously for normal operation. The short circuit fault calculations shall check out as consistent with this fact. The retro-fitting of fault-limiting reactors is not desirable.

The designing of Switchboards for the “worst-case” fault is European Practice and the safest approach. The 132kV and 220kV Distribution Switchboards on TAKREER GUP Phase III Project by ALSTOM (refer to Attachment C) can be put forward as an example of this. However the increased Safety comes at a higher initial cost for downstream 3.3kV and 415V NBC Switchboards as extra Substation equipment is normally necessary. A larger csa of Bus-bar Cu is the minimum that can be expected with extra reinforcing of the supports to withstand the higher forces.

Similarly the 33kV, 132kV and 220kV Distribution Switchboards on a defined Project (e.g. POC) can follow the same “no-break” philosophy of operation as the DGS-EU-001 Clause 11.8.b and Clause 11.8.c 11kV Switchboards.

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ATTACHMENT C

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ATTACHMENT D

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ATTACHMENT E

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ATTACHMENT F – Emergency Distribution System

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