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PDVSA N° TITULO

REV. FECHA DESCRIPCION PAG. REV. APROB. APROB.

APROB. FECHAAPROB.FECHA

VOLUMEN 4–I

PDVSA, 1983

N–252 GENERAL SPECIFICATION FOR ELECTRICAL

ENGINEERING DESIGN

APROBADO

Eliecer Jiménez Alejandro NewskiJUL.96 JUL.96

ENGINEERING SPECIFICATION

JUL.96 L.T.0 33 E.J. A.N.

MANUAL DE INGENIERIA DE DISEÑO

ESPECIALISTAS

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GENERAL SPECIFICATIONS FORELECTRICAL ENGINEERING DESIGN JUL.960

PDVSA N –252

Página 1

.Menú Principal Indice manual Indice volumen Indice norma

Index

1 GENERAL DESIGN AND ENGINEERING PRINCIPLES 2. . . . . . . . .

1.1 Scope 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.2 Definitions 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.3 Codes and Standards 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1.4 Safety , Reliability and Energy Conservation 7. . . . . . . . . . . . . . . . . . . . . . . .

2 ELECTRICAL SYSTEM DESIGN 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.1 Basic Information 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.2 System Voltages 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.3 Variations In Supply Voltage 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.4 System Power Factor 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.5 Supply Capacity 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.6 Short Circuit Ratings 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.7 Electrical Protection And Control 10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.8 System Grounding 14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.9 Electricity Supply Facilities for Process Controland Safeguarding Systems 15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 DESIGN AND SELECTION REQUIREMENTS FOR EQUIPMENT,CABLES AND INSTALLATIONS 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.1 Switchgear 16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.2 Transformers 19. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3.3 Electric Motors 21. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.4 Cables And Wires 23. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.5 Lighting 25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.6 Power and Convenience Outlets 25. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.7 Metering Equipment 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.8 Grounding 26. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3.9 Substations 27. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4 SUBSTATION FIRE PROTECTION 28. . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.1 General 28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.2 Mandatory Requirements 28. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5 POWER SUPPLY UNITS 30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6 ECONOMICAL EVALUATION OF LOSSES 30. . . . . . . . . . . . . . . . . . . .

7 DOCUMENTS AND DRAWINGS 30. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1 GENERAL DESIGN AND ENGINEERING PRINCIPLES

1.1 Scope

This general specification covers the minimum technical requirements forelectrical engineering design, electrical area classification, grounding and lightingsystems for oil and petrochemical plants owned by PDVSA.

1.2 Definitions

Shall.

Is to be understood as mandatory

Owner.

Party which initiates the project and ultimately pays for its design and construction.

Contractor.

Party which carries all or part of the design, engineering, procurement,construction and commissioning for the project.

Low Voltage.

Less than 1 000 V (Defined by ANSI C 84.1).

Medium Voltage.1 000 V and less than 100 000 V

High Voltage.

Equal to or greater than 100 000 V.

Vital Service.

A service, which, when failing, can cause an unsafe condition of the processand/or electrical installation, jeopardize life, or cause major damage to theinstallation.

Essential Service.

A service, which, when failing, will affect the continuity, the quality or the quantityof the product.

Certificate

Document issue by a recognised authority certifying that it has examined a certaintype of apparatus and, if necessary, has tested it and concluded that theapparatus complies with the relevant standard for such apparatus.

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Hazardous Area

An area which an explosive atmosphere is or may be expected to be present inquantities such as to require special precautions for the construction, installationand use of electrical apparatus

Stand –by Capacity.

Capacity provided for the purpose of replacing that capacity which may bewithdrawn from service under planned or unplanned circumstances.

Firm Capacity.

The installed capacity less the stand – by capacity.

Spare Capacity.Difference between firm capacity and the maximum calculated (peak) load.

Station or Substation.

An assembly of equipment at one place, including any necessary housing, for theconversion or transformation of electrical energy and for connection between twoor more circuits.

Indoor Substation.

A station which consists of indoor equipment within a field constructed building.

Outdoor Substation.The equipment is protected by a weather proof enclosure (standard outdoorconstruction).

Main Substation.

A station for connection between a power or distribution system of a process unitand an outside electrical supply system.

Power Plant Substation.

A station to which generators and outgoing feeders are connected.

TropicalizedPreparation of equipment or apparatus to avoid the effects due to the tropicalweather.

Distribution Substation.

A station mainly used for feeding several plant stations.

Plant Substation.

A station mainly used for feeding one process installation.


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Secondary Selective Substation.

Station having two busses, each supplied by a normally closed incoming linecircuit and connected together by a normally open bus – tie circuit breaker.

Spot Network Substation.

A station supplied from two or more sources which normally divide the substationload in paralleled operation.

1.3 Codes and Standards

The design and engineering of the electrical installation shall basically comply withthe Venezuelan Codes. Where international standards or codes of practice arereferred to here in, it is the Contractor ’s responsibility to ensure that Venezuelan

Statutory requirements are met if these are more stringent than the referencesprovided.

In the event of contradictions, the requirements of this specification shall prevail.

The codes and specifications listed below, in effect as of the latest edition, shallconstitute minimum requirements:

1.3.1 PDVSA – Petróleos de Venezuela, S.A.

GE – 211 Electric Standby Generator

Set – Engine Driven

HA – 201 Cathodic Protection

JA – 221 Diseño Antisísmico de Instalaciones Industriales

L – STE – 017 Mechanical Coordination

L – STE – 018 Electrical Design Drawings

L – STE – 019 Procedures for Checking Electrical

Design Drawings

L – STE – 020 Electrical Estimating Procedure

N – 201 Electrical Work

N – 241 Installation of wires and Cables in Conduit and

Cable Tray SystemN – 301 Low Voltage Electrical Motors

N – 302 High Voltage Electrical Motors

N – 242 Electrical Work Installation and Testing

Q – 211 – PT Field Inspection for Transformers Reception

Q – 231 Electrical Wire and Cable TestingSD – 251 Site Data

IR – E – 01 Hazard Area Classification

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IR – M – 01 Separación entre Equipos e Instalaciones

90619.1.050 to .064 Engineering Design Guide – Electrical1.3.2 COVENIN – Comité Venezolano de Normas Industriales

200 Venezuelan Código Eléctrico Nacional (similar to NEC / ANSI / NFPA – 70)

548 Recomendaciones para clasificar las áreas destinadas ainstalaciones eléctricas en refinerías de petróleo

559 Recomendaciones para clasificar las áreas destinadas ainstalaciones en los sistemas de tuberías para transportarpetróleo y gas.

603 Recomendaciones para clasificar las áreas destinadas ainstalaciones eléctricas en instalaciones de producción petrolera

734 Código Nacional de Seguridad de Instalaciones de Suministro deEnergía Eléctrica y de Comunicaciones, (Based on the NationalElectrical Safety Code ANSI C2).

2249 Iluminaciones en Tareas y Areas de Trabajo

1.3.3 American Standards:

ANSI – American National Standards Institute

C2 National Electrical Safety Code

C37.2 Standard Electrical Power System Device Function NumbersC37.010 Application Guide for AC High – Voltage Cicuit Breakers Rated

on an Symmetrical Current Basis.

C.37.20.1 Standard for Metal – Enclosed Low Voltage Power CircuitBreaker Switchgear.

C.37.20.2 Standard for Metal – Clad and Station – Type Cubicle Switchgear

C57.12.00 Standard General Requirements for Liquid ImmersedDistribution, Power, and Regulating Transformers.

C57.12.10 Transformers – 230 kV and Below 833/958 through 8333/10417kVA, Single – Phase, and 750/862 through 60000/80000/100000kVA, three – phase without Load tap Changing; and 3750/4687through 60000/80000/100000 kVA, with Load tap Changing – Safety Requirements

C 84.1 Electric Power Systems and Equipment – Voltage Ratings (60Hertz)

Y32.9 Graphic Symbols for Electrical Wiring and Layout Diagrams

70 National Electrical Code (National Fire Codes, vol.3)

979 Guide for Substation Fire Protection.

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NEMA – National Electrical Manufacturers Association

MG – 1 Motors and Generators; Revision No.1 – December 1993,Revision No.2 – April 1995

IEEE – Institute of Electrical and Electronics Engineers

519 Recommended Practices and Requirements for HarmonicControl in Electrical Power Systems

Std. 841 Standard for Petroleum and Chemical Industry – Severe DutyTotally Enclosed Fan Cooled (TEFC) Squirrel Cage InductionMotors – Up to and including 500 HP

ICEA – Insulated Cable Engineers Association

P – 32 – 382 Short – Circuit Characteristics of Insulated Cable

P – 45 – 482 Short – Circuit Performance of Metallic Shielding & Sheaths

API – American Petroleum Institute

RP 500 Recommended Practice for Classification of Locations forElectrical Installations at Petroleum Facilities

Standard 541 Form – Wound Squirrel Cage Induction Motors – 250 HorsePower and Larger

NFPA – National Fire Protection Association

70 National Electrical Code (National Fire Codes, vol.3)

AEIC – Associations of Edison Illuminating Commission

CS5 Specifications for Cross – Linked Polyethylene InsulatedShielded Power Cables Rated s Through 46 kV

1.3.4 International Standard

IEC – International Electrotechnical Commission

76 Power Tansformers

158 Low Voltage Controlgear255 Single Input Energizing Quantity Measuring Relays with

Dependent Specified Time

529 Degrees of Protection Provided by Enclosures (IP Codes)

549 High – Voltage Fuses for the External Protection of Shunt PowerCapacitors

617 Graphics Symbols for Diagrams

947 Low – Voltage Switchgear and Controlgear

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GENERAL SPECIFICATIONS FOR

ELECTRICAL ENGINEERING DESIGN JUL.960

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1.3.5 The Electrical equipment and material shall be designed, manufactured and

tested by the governing standards and regulations of the country of manufacture.In general, the recommendations of IEC shall govern for equipment manufacturedoutside of the USA, while ANSI and NEMA shall govern for equipmentmanufactured in the USA.

1.3.6 Where requirements contained in this specification are higher than those in thecodes or standards referred to above, this specification shall prevail.

1.3.7 Electrical graphical symbols shall be per IEC–617, or ANSI Y32. Identification bydevice code letters and by device code numbers shall be per ANSI C37.2.

1.3.8 The SI unit system shall be used throughout the design. For motors, kW and

equivalent HP shall be indicated.

1.3.9 The equipment and electrical installation shall be tropicalized and suitable for theenvironment influences and climatic conditions as specified:

– Altitude

– Humidity

– Ambient air temperature

– Atmosphere

– Sismic conditions: in accordance with PDVSA .JA–221.

1.4 Safety, Reliability and Energy Conservation

1.4.1 The electrical installation shall be designed and guaranteed to ensure personaland operational safety during all operating conditions, inspections andmaintenance, including those associated with start–up and shutdown of plant andequipment.

1.4.2 Energy conservation shall be pursued throughout the design. Periodic energyaudits shall be carried out to assure optimum results.

1.4.3 The electrical design shall permit periods of continuous operation of at least 4years.

1.4.4 The insulating and dielectric materials used in all electrical equipment shall benon–toxic and shall not contain compounds that are persistent and hazardousenvironmental contaminants, such as poly–chlorinated biphenyls (PCBs).

1.4.5 Standardization of material and equipment shall be aimed. Equipmentincorporating similar or identical components and of similar or identicalconstruction, shall be of the same manufacturer.

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1.4.6 Area classification drawings and electrical equipment selection shall conform to

PDVSA – MIR Vol. 2 (IR – E – 01), and NEC. The former is based on, API RP 500 andCOVENIN 548, 559 and 603. A table shall be included in the area classificationdrawing, showing the relevant physical properties of substances handled in everyclassified area, such as: flash point, ignition temperature, flammable limits inpercent by volume, relative vapor density, operating pressure, flow and volumenhandled

1.4.7 Fire detection and alarm shall conform to PDVSA “Risk Engineering Manual” andNFPA. The minimum distance between equipment and installations shall be perPDVSA IR – M – 01 “Separación entre Equipos e Instalaciones”.

1.4.8 Approved equipment, which is required for classified locations, shall be labeled,

listed or certified by a national recognized testing organization such as theUnderwriter Laboratory (USA), the Department of Trade and Industry (GreatBritain), or PTB (Germany). Where such equipment is not available, its designshall conform to the standard of a nationally recognized testing organization.

1.4.9 Control rooms and switch houses shall be situated in non – hazardous areas. Ingeneral, electrical equipment shall, as far as possible, be located in nonhazardous areas.

1.4.10 For all major equipment, the purchaser shall obtain, at least, the manufacturer’stest report in accordance with PDVSA specifications, e.g. for generators, motors,HV, MV and LV switchgears, transformers, batteries and inverter units.

2 ELECTRICAL SYSTEM DESIGN

2.1 Basic Information

2.1.1 Single line diagrams and data, as indicated in PDVSA N – 201, Section 3.3, shallbe prepared for approval by owner ’s engineer.

2.1.2 A schedule of the installed electrical loads, the maximum normal running plantload and the peak, expressed in kW and kVA, shall be prepared using documentEngineering Design Guide PDVSA 90619.1.050.

2.2 System Voltages

2.2.1 Voltage ratings shall conform to ANSI C84.1, range A. The electrical equipmentshall be designed for 3 – phase, 60 Hz operation at the voltages mentioned inAppendix A. (See PDVSA N – 201 , Chap. 5.1).

2.3 Variations In Supply Voltage

2.3.1 Terminal voltage and voltage drop shall be as indicated in PDVSA N – 201.Sections 3.5.28 up to 3.5.35.

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2.3.2 Voltage sags of short duration causing the drop – out of contactors and other

sensitive loads, usually affect the process continuity. A comprehensive study shallbe carried out to provide appropriate methods to eliminate these events, such as:automatic reacceleration and/or restarting of motors, contactors fed from theUPS, or any other measure to desensitize the critical loads.

2.3.3 Deviations and variations in plant voltages from the rated equipment voltage, shallbe as follows:

– Steady state conditions: – + 5%.

– Starting or reacceleration of a motor or group motor starting/reacceleration:+10%, – 20%.

– Voltage drop to 80% shall not affect plant operations.

– Voltage drop below 80% for a duration of not more than 0.2 seconds shall, ona voltage restoration, result in the instantaneous re – energization of vital andessential services.

– Voltage drop below 80% for a duration of 0.2 and 4 seconds shall, on a voltagerestoration, result in a sequential re – energization of selected loads.

2.3.4 Harmonic voltage – current distortion shall be as per IEEE – 519 (RecommendedPractices and Requirements for Harmonic Control in Electric Power Systems).

The proposed limits are as follows:

Harmonic voltage distortion in %

< 69 kV 69 – 138 kV > 138 kV

Maximum for

Individual harmonic 3.0 1.5 1.0

Total harmonic 5.0 2.5 1.5

Equipment having special requirements with respect to variations in voltage leveland/or wave form shall be provided with a power supply that is adequatelystabilized.

2.4 System Power Factor

The overall system power factor shall not be less than 0.9 lagging at rated design

throughout the process unit.The power factor at the main station (interconnection to power utility) shall be notless than 0.95, averaged over 15 minutes.

2.5 Supply Capacity

2.5.1 The firm capacity of the electricity supply and distribution system shall be capableof supplying continuously 120% of the peak load, assessed according to theapplicable load data without exceeding specified voltage limits and equipmentratings.


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2.5.2 In general, plant substations will be of the double – ended type, operating with

normally open tie breakers. Transformers, shall be rated self cooled (OA) 65°

C/Fan Cooled (FA) 65 oC. Each transformer shall be sized such that its 65° C selfcooled rating be equal to 120% of the maximum demand of the served load.

2.5.3 Transformer rating shall be selected such that the starting of the largest motor willnot cause the motor terminal voltage to drop below 80 percent of the normaloperating level.

2.5.4 Electrical power supply during construction, commissioning and start – up shallcomply with all the applicable rules of ANSI/NFPA 70 and ANSI C2.

2.6 Short Circuit Ratings

2.6.1 All equipment shall be capable of withstanding the effects of short circuit currentpassing through the system in the event of circuit faults.

2.6.2 The short circuit ratings of medium voltage (MV) equipment and cables, exceptionfor secondary selective substation, shall be based on the parallel operation of allavailable supplies. Ratings of equipment are indicated in Engineering DesignGuide PDVSA 90619.1.053.

2.6.3 The short circuit rating of low voltage switchgears shall be as stated in EngineeringDesign Guide PDVSA 90619.1.053. For MV and LV secondary selectivesubstation, the short circuit ratings shall be calculated with one incoming line

breaker open and the bus tie breaker closed.

2.6.4 Short circuit calculations shall conform ANSI/IEEE C37.010 (Application Guide forAC High – Voltage Circuit Breakers Rated on a Symmetrical Current Basis).

2.7 Electrical Protection And Control

2.7.1 General

a. The electrical system components shall be coordinated in regards to short circuitcapability, protective relaying, insulation levels, transient stability,interchangeability, durability and reliability. Phase and ground overcurrent

protection shall be provided in all MV and LV incoming and outgoing circuits. Anexception to this requirement are those LV branch circuits in which phaseovercurrent protection coordinates with upstream ground fault protective devices,such as small motors and general – purpose circuits.

b. Protective relay settings shall be based on a study of the fault conditions for whichthe protective system has been incorporated. Protective relay system shall beselective and the settings shall be coordinated such that back – up protection isprovided to initiate fault clearance in the event of protective system and / orswitching device failure.

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c. A protection drawing shall be prepared as indicated in PDVSA N – 201, paragraph

3.3.1.d. Trip circuit supervision will be applied to all high and medium voltage circuit

breakers and arranged to provide an alarm on trip circuit interruption.

e. Protective relays shall have two N.O. contacts. One contact shall be wired directlyto the trip coil circuit. The second contact shall be wired to a lock – out relay (86).One 86 N.C. contact shall be connected in series with the closing coil (permissive);one 86 N.O. contact shall be used to repeat the tripping signal to the circuit breakeror contactor.

Frequency relay (81) and undervoltage relay (27) shall not be wired to the lockoutrelay (86).

2.7.2 Generator Protection

Protection shall be arranged to isolate generator or generator and unittransformer (if provided) from the power system. If generator is connected to thesystem via an unit transformer, the generator shall be provided with highimpedance grounding equipment and relevant alarms.

a. Protective Devices

Short circuit protection, differential protection, voltage controlled overcurrentprotection, restricted ground fault protection, over – excitation protection, reversepower protection, loss of excitation protection, negative phase sequence

protection, overvoltage protection, underfrequency protection, delayed groundfault protection, loss of lubrication, over temperature, vibration protection andturbine trips.

b. Alarm equipment

Rotor ground fault, stator temperature (by embedded thermocouples), bearingtemperature, vibration, temperature and humidity of cooling air, synchronizingfailure, automatic voltage regulator, and alarms for protection equipmentindicated in 2.7.2. a

2.7.3 Switchgear Protection

a. The 115/69 – 34.5 kV main substation, shall be protected by bus – zone differentialprotection, at both voltage levels as agreed with the owner.

b. Unrestricted short circuit current and ground fault protective devices shall beapplied at the remote end of the switchboard incoming circuit feeders which shallalso serve as protection of switchboard bus bars in the event of bus bar faults andas back – up to switchboard outgoing circuit protection.

c. Short time current carrying capability shall be three (3) seconds for HV and MVswitchboards, and one (1) second for LV switchboards.

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2.7.4 Power Transformer Protection

a. Power transformers (Dy) shall be controlled and protected on the primary side bycircuit breakers in conjunction with phase short – circuit and ground fault protectiverelays. Phase short – circuit protection shall be by means of two – stage overcurrentrelays.

Stage 1 being time delayed and set to detect secondary circuit faults. Stage 2being instantaneous (High Set elements) in operation and set to detect primarycircuit faults only. Primary circuit ground fault protection shall be by a residualcurrent relay, set to achieve minimum fault clearance time.

b. Power transformers with 480 V on secondary winding shall be provided withextremely inverse definite minimum time relay in accordance with IEC 255 – 4 Type

C.c. Power transformers, rated 10 MVA and above, shall further (2.7.4.1), be provided

with biased differential protection (87T). The transformer primary and secondarycables shall be included within the protected zone. All transformers 34.5 kV andabove shall also be provided with differential protection.

d. The secondary circuits of all distribution and generator unit transformers shallhave separate ground fault protection by means of an overcurrent relay (51G)which shall be energized by a current transformer placed in the neutral – groundconnection of the power transformer secondary winding.

e. Sealed transformers shall be provided with an automatic resetting pressure relief

device. Sealed transformer of 500 kVA and above, shall be provided with a suddenpressure relay device, (fault pressure relay) and Buchholz relay (63) forconservator type transformer.

f. Transformers shall be provided with a hot oil temperature indicator and combinedalarm and trip relays of approved design.

g. Power transformers having HV or MV on the windings shall be provided withwinding hot spot temperature and magnetic oil level with alarm and trip relays.

h. Transformer protection trips (26, 49, 63, 87T, 50, 51G) shall be wired to a lockoutrelay 86T and shall have their individual alarms.

2.7.5 Capacitor ProtectionHV capacitor banks shall comprise individually fused capacitor units. The fusesshall comply with IEC 549 and shall be esily accessible for inspection andreplacement. For large capacitor banks exceeding 1000 kVAr the capacitors shallbe conected in double star with unbalance protection monitoring the star pointvoltages, or with differential current protection across the two halves of thecapacitor bank. Capacitor failure shall trip the bank and provide an alarmindication. If recommended by the Manufacturer, overpressure switches shouldbe fitted to HV capacitor units and connected to trip the capacitor bank.


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Individual capacitors shall be controlled by contactors, circuit breakers or for LV

applications by fused switch units. The switching devices shall be approved forthis duty by the switchgear manufacturer. They shall be rated for at least 1.5 x In,and must be able to withstand transient inrush currents up to 100 x In

Contactor or switch controlled capacitor banks shall be protected by means offuses. In the case of cicuit breaker control, phase fault and earth fault protectionrelays shall be provided.

In those cases where a capacitor is connected in parallel with an electric motor,a single switching device and associated relays and/or fuses that control andprotect both the motor and the capacitor shall be provided.

2.7.6 Asynchronous Cage Induction Motor Protection

a. Induction motors shall be switched direct on line. Other methods shall beapproved by the owner.

b. Medium voltage motors shall be controlled by fused vacuum contactors of thelatched mechanism type. Motors above 1.5 MW (2 000 hp) at 4 000 V, shall becontrolled by circuit breakers with surge suppressors. Other methods shall beapproved by the owner.

c. Medium voltage motors shall be protected as follows:

– Undervoltage protection:

One instantaneous undervoltage relay in each bus (range about 70/100% ofnominal voltage). Each starter shall be provided to operate in conjunction withthe undervoltage relay with and adjustable time relay (range of 0.1 to 5 s) orinverse time undervoltage relay for each motor.

– Short circuit protection:

Motors controlled by contactors shall be protected by current limiting fuses withantisingle phasing features. Motors controlled by circuit breakers shall beprotected by overcurrent relays (High Set).

– Instantaneous ground fault protection (suitable for resistance groundedsystem)

– Thermal overload protection – Unbalanced loading

– Bearing temperature detection

– Locked rotor protection

– Stator temperature detection for motors above 1 500 kW (2 000 hp)

– Differential protection for motor over 1 500 kW (2 000 hp).

MV motors shall be protected by a multi – purpose motor protection relay withall the above functions included, using microcomputer technology.


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d. Low voltage motors (460 V) shall be protected as follows:

– Short circuit protection by molded case circuit breakers (MCP type). – Thermal overload protection with antisingle phasing protection.

– Core balance ground leakage protection for motors above 30 kW (40 hp), andfor smaller motors whose phase short – circuit protection doesn’t coordinatewith upstream ground fault protective devices. Ground faults shall be clearedby the motor circuit breakers through built – in shunt trip devices.

– Electronic Restart Module for essential motors.

2.7.7 Cable Feeder Protection

a. MV cable feeders for distribution (not transformer feeders) shall be controlled and

protected by circuit breakers in conjunction with phase overcurrent (50/51) andground fault (50N/51N)) protective relays. Unless otherwise specified theovercurrent relays will be of Inverse Definite Minimum Time (IDMT) in accordancewith IEC 255.4 Type A with high set elements incorporated.

b. Differential protection shall be provided on all 34.5 kV duplicated undergroundcable feeders.

2.7.8 Overhead Line Protection

a. Overhead lines of primary distribution feeders shall be controlled and protectedby circuit breakers in conjunction with phase shortcircuit and ground faultprotective relays.

b. When distance protection is employed it shall be provided in conjunction withovercurrent and ground fault protection, the latter serving as back – up protection.

2.7.9 Power and Convenience Outlets Protection

Each power and convenience outlet circuit operating at low voltage shall beprotected by phase short circuit protective devices and by current – operatedground leakage protective devices. The residual operating current shall be 30 mAfor single – phase convenience outlets and 500 mA for 3 – phase power outlets.

2.8 System Grounding

2.8.1 Solidly Grounded Neutral Systems

The solidly grounded neutral shall be used for all the low – voltage systems thatsupply lighting, control, instrumentation, heating and fractional horsepower motorloads. These systems include:

a. 120/240V single – phase, three – wire

b. 208Y/120V, three – phase, four – wire

c. 480Y, three – phase, three – wire used to supply motor loads (non critical)


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d. 480Y/277V, three – phase, four – wire used to supply 277V lighting loads

When the 480Y/277V, three – phase, four – wire system is used to supply lightingloads, separate transformers should be used for this service rather thancombining the service with the motor loads.

The use of solidly grounded neutral systems for motor circuits and other powerfeeder circuits is generally limited to the 480V voltage level and should beconsidered when such loads are not part of critical continuous processes.

2.8.2 Low –Resistance Grounded Neutral Systems

Low – resistance grounded neutral systems shall be used for all medium – voltagedistribution where large rotating machinery may be directly connected to thesystem.

This generally applies to the levels of 4.16 kV, 13.8 kV and 34.5 kV.

The resistor is generally sized to limit the ground – fault current to a value of 400A, but in

some cases 600 A or 800 A may be selected.

2.8.3 High –Resistance Grounded Neutral Systems

The high – resistance grounding shall be used on low voltage systems supplyingmotor services (480V) for critical continuous processes, such as petrochemicalplants and refineries. This system provides the advantages of the ungroundedsystem and the main advantage of the solidly grounded system, which limitstransient overvoltages.

A detection and alarm system shall be provided to the trace the ground faultthoughout the system.

2.8.4 Ungrounded Electrical Systems

Ungrounded electrical systems shall not be used for new facilities. Theappropriate replacement is a high – resistance grounding system.

2.9 Electric Supply Facilities for Process Control and Safeguarding Systems

2.9.1 The battery autonomy capacity of the d.c system for process control and safe –

guarding systems shall be 1/2 hour for normal process units and 1 hour for utilityunits at the maximun load.

2.9.2 The electric supply for process control equipment shall be provided from an UPSsystem. The UPS system shall be fully redundant, which includes two rectifiers,two inverters and one battery bank. The electricity supply for safeguardingsystems shall be taken from a dc source of supply. Two units shall be installed andconnected in parallel. The a.c. supply for the d.c. source shall be taken from theUPS source. If the safeguarding is an integral part of the process control systemthe requirements shall be met by the UPS system.


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3 DESIGN AND SELECTION REQUIREMENTS FOR

EQUIPMENT, CABLES AND INSTALLATIONS

3.1 Switchgear

3.1.1 Switchgear and controlgear shall be in accordance with PDVSA N – 201, Sections3, 8, 9 and Engineering Design Guide PDVSA 90619.1.053 – 90619.1.054 andTechnical Specification for M.V and L.V. switchgear

3.1.2 Switchgear and controlgear installations for process area shall be located indoorin a closed air conditioned building in a non – hazardous areas and near the centerof the load.

3.1.3 Medium voltage up to 36 kV and low voltage plant substation shall be of a doubleended secondary selective design. 4160 and lower voltage switchgears,supplying essential loads, shall be secondary selective with automatic transfer.Switchgear and each incoming feeder shall be designed to withstand 120 percentof maximum expected load.

3.1.4 The secondary selective switchgears shall be provided with a trip selector switchfor manual switching (PDVSA N – 201, Section 9.3.4). The trip selector will haveonly 3 positions: one position for bus tie breaker and one position for eachincoming line breaker. The switch shall be arranged so that the selected breakertrips after all three breakers are closed. Incoming lines may thus be momentarily

paralleled during switching to prevent service interruption. MV and LV switchgearshall be provided with a synchronizing check relay (25) when required.

3.1.5 Control and protection schematic diagrams shall be designed according toPDVSA Drawings (N – 201). Protective relaying coordination criteria for secondaryselective substations is presented in a summary table in Appendix B. When twoor more secondary – selective substations are interconnected in cascade,automatic transfer of downstream substation shall be time – delayed to allow forthe upstream substation to complete its transfer operation.

3.1.6 For substations serving process units which are subject to periodic shutdown

(turnaround) for maintenance and repair, essential service required duringshutdown shall be segregated from service during normal operation. (See PDVSAN – 201, Section 3.8). The turnaround power center shall have an alternativesupply from each main bus with manual transfer and interlocking againstparalleling the main busses.

3.1.7 MV switchgear structures shall be metal clad in accordance with ANSI C.37.20.2“Standard for Metal – Clad and Station – Type Cubicle Switchgear”. LV switchgearshall be metal enclosed in accordance with ANSI C.37.20.1 “Standard forMetal – Enclosed Low – Voltage Power Circuit Breaker Switchgear”.

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3.1.8 The switchgear shall be modular type sheet steel cubicles, not less than 12 gauge

sheet steel (2.75 mm) structural steel frame work, floor mounting and selfsupporting with a degree of protection as a whole of not less than Nema 12 or IP42(IEC 529) without using the floor as part of the enclosure. MCCs and switchgearback to back type are accepted with owner’s approval. Doors shall be providedwith non absorbent, non sticking gaskets.

3.1.9 The bus bar system for MV and LV, shall be insulated to the most practicableextent and its connection arrangement shall be fault – free.

LV/MV contactors and circuit breakers shall be of the withdrawable type, exceptin gas insulated switchgear application. MV contactors shall be latched type. LVmotor control center shall be combination of MCP circuit breaker and air break or

vacuum contactor.3.1.10 115 and 69 kV breakers shall be of SF6 type. MV circuit breakers, including 34.5

kV breakers, and MV contactors shall be of the vacuum or SF6 type. LV circuitbreakers shall be air break type. LV contactors shall be air break typeelectro – magnetically operated, hold – in type. MV breakers shall be of springcharged motor type.

3.1.11 Contactors shall be capable of interrupting the locked rotor current of the motor(NEC 430 – 82) according to NEMA or category AC4 according to IEC 947 – 1 and947 – 4 – 2. Starters shall be full voltage, non reversing, single speed, combinationtype. Soft start or reduced voltage can be used with owner’s approval.

3.1.12 MV switchgear shall be provided with a frequency relay (81) in each bus sectionto shed MV non – essential motors in case of generation deficit. The load sheddingsystem shall prevent relay misoperation due to motor residual voltage duringautomatic bus transfer.

3.1.13 Each LV starter shall be provided with a complete wired base for connecting aplug – in Electronic Restart Module type ERM or TDRM for immediate or delayedrestarting of motors after mains voltaje sag or interruption, in order to comply withparagraph 2.3.2. Aditionally, all critical motor starter shall be provided with theERM relay.

3.1.14 Latched switching devices shall be provided with a healthy trip pilot lights tosupervise condition of tripping circuit. All breakers and starters shall be providedwith pilot lights, green and red, to indicate open – close operation, and shall beprovided with space heater controls.

3.1.15 Watthour, voltampere and ammeter with demand interval of 15 minutes shall beprovided in stations 500 kVA or larger.

3.1.16 A running hour counter and operation counter shall be provided for each MV motorstarter. All MV breakers shall be provided with mechanical operation counter.


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3.1.17 A maximum of one MV breaker or contactor shall be supplied in any vertical

section. Two in one column shall be approved by the Owner. One spare(equipped) motor starter shall be provided in each 4160 V bus section. At leastone spare and one space cubicles should be provided in each 480 V powerdistribution center bus.

The following spare 480 motor starters and spaces shall be included in everymotor control center:

NEMA Size Spare Space

1 – 2 5% 5%

3 and larger 1 unit 1 unit

3.1.18 The vacuum and SF6 contactors shall have a chopping current less than 0.75 A.The vacuum and SF6 breakers shall have a chopping current less than 5 A.

3.1.19 Components of switchgear shall be standardized as much as possible.

3.1.20 Control power shall be as follows:

MV breakers: 120 V ac for spring charged motor

125 V dc for closing

125 V dc for tripping


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3.2.6 The basic impulse insulation levels and insulation classes shall be as specified in

ANSI C57.12.00, tables 3,4 and 5. Bushings shall be of an insulation class not lessthan that of the winding terminal to which they are connected. Neutral, for eachMV winding specified with neutral brought out, shall be fully insulated.

3.2.7 Transformers of the unsealed type shall be provided with a conservator tankmounted above the highest point of the oil circulating system of the equipment.It shall have an inside flexible membrane for oil/air separation. Each conservatorshall be fitted with one oil – level indicator of direct reading prismatic glass typevisible from ground level and one filling orifice with an air tight capture – screwedcap.

3.2.8 At Main Station, where specified, transformers shall be provided with a three

phase on load tap changer to vary the nominal voltage by plus 10% and minus10%. The on load tap changing equipment shall consist of a liquid immersedarcing tap switch or tap selector and a diverter switch (arcing switch), a motormechanism and automatic control devices. Diverter switch tank shall be pressureproof and provided with an overpressure (or overflow) protection device todisconnect the transformer and release the pressure completely. Diverter switchcontacts shall be designed to ensure long life operation.

3.2.9 For system voltage up to 34.5 kV, cable terminations shall be in an integratedair – filled box suitable for mounting on the side wall of the transformer with aremovable non magnetic plate and suitable provisions for terminating cable. A

grounding bolt of adequate size shall be provided for each cable shield and shallbe located inside the box.

The boxes shall be weather proof with a minimum degree of protection of IP 55or NEMA 4. Space heaters shall be installed inside the cable – end boxes toprevent condensation. Low voltage wiring shall be segregated by metal barriers.When the item description calls for a bus duct, the cable box shall be soconstructed as to permit the coupling of the bus duct to the box without losing theminimum degree of protection.

3.2.10 MV and LV boxes,on transformers above 2.5 MVA, shall be provided withdisconnecting links to isolate the cable from the transformer terminals for testing

purposes. Primary and secondary voltage metallic ducts shall be installed directlybelow the transformer’s cable – end boxes up to the ground level. These ducts willgive mechanical protection to power cables.

3.2.11 Radiators for transformers, rated above 2 500 kVA, shall be detachable and shallbe provided with a machined or ground flanged inlet and outlet for bolting to thetransformer tank through isolating valves.

3.2.12 Metal sun shades shall be fitted over all boxes at approximate 50 mm above topcover.


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3.2.13 A durable metal nameplate of corrosion resistant materials shall be affixed to each

transformer by the manufacturer. The minimum information shown on thenameplate shall be that specified in ANSI C57.12.00, table 9, nameplate C andthe following information, when applicable:

– Purchaser order number.

– Indication of provision for future forced cooling equipment

– Maximum operating pressure of oil preservation system (positive andnegative).

– Tank designed for vacuum filling.

3.2.14 Finish paint shall be light gray NFPA 70. Alternative manufacturer’s standard is

acceptable, as long as it is at least equivalent to the above finish.

3.2.15 Rated voltage for three – phase transformers (nominal):

115 and 69 kV Neutral solidly grounded

34.5 kV Grounded through low resistance



0.480 kV Solidly grounded

3.2.16 Unless otherwise specified, the angular displacement between the primary andsecondary phase voltages with a delta – wye connection shall be as per IEC 76standard Dyn 11 (secondary voltage lags primary voltage by 30 deg.).

3.2.17 All windings, up to 34.5 kV, shall be fully insulated, as defined in ANSI C57.12, orIEC 76. All neutral points of star windings shall be brought out to a terminalbushing. The neutral terminal shall have an insulation class equal to the insulationclass of the line terminal. For 69 and 115 kV, it shall be agreed with the owner ’sengineer.

3.3 Electric Motors

3.3.1 Medium voltage (MV) electric motors shall be in accordance with API Standard541 “Form Wound Squirrel – Cage Induction Motors – 250 hp and larger”. Lowvoltage (LV) motors shall be in accordance with IEEE Std 841 ”IEEE Standard forPetroleum and Chemical Industry – Severe Duty Totally Enclosed Fan Cooled(TEFC) Squirrel Cage Induction Motors Up to and Including 500 hp”. Electricmotors shall be high efficiency type. Unless otherwise specified herein, when theword “should” appear in the API 541 and IEEE Std 841 it must be substituted by“shall” and, therefore, considered mandatory.


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3.3.2 MV induction motors, 150 kW (200 hp up to 7000 hp) and larger, shall be 4 000

V, 60 Hz, squirrel cage type, suitable for full voltage, across the line starting. LVmotors, 0.56 kW to 149 shall be 460 V. The kW break point may vary for reasonsof economy with approval by Owner.

3.3.3 Cooling system shall be air to air (CACA). Air to water cooling is not acceptable,for motors up to 7 000 hp (4 000 V).

3.3.4 The minimum degree of protection of an industrial motor shall be IP 54, (IEC 529)or TEFC – Guarded (NEMA MG – 1) for the motor enclosure and IP 55 for theterminal boxes and bearing housings.

3.3.5 Nema II, weather – protected motors (IPW24) are not acceptable.

3.3.6 Motors for Division I shall be explosion proof. For Division 2 they shall be, inaddition to (3.3.4), non – sparking, which in normal service do not arc or spark orproduce ignition due to hot surfaces. Unless otherwise specified on therequisition, a Div.. 2 motor shall be designed for temperature class T3 (200° C).

3.3.7 Site condition is highly corrosive. Motors shall be ruggedized, suitable forextremes of environmental conditions and shall include antifungus tropicalprotection. For LV motors, all enclosure parts shall be cast iron. For MV motors,all enclosure parts shall be cast iron or fabricated carbon steel sheet of 1/8 inch(3 mm) minimum thickness.

3.3.8 The starting torque characteristics shall be minimum NEMA Design B. At 80%rated voltage and rated frequency applied at the motor terminals, it shall beadequate for starting the driven load under the most severe conditions, e.g pumpwith open discharge. Under these conditions, the accelerating torque shall be notless than 10% of the rated full load torque, at 80% rated voltage and at any speedbetween zero and that at which pull – out occurs.

3.3.9 Motors shall be suitable for starting duties of at least two starts in succession aftercontinuous running, once the motor is allowed to coast to rest.

3.3.10 Motors shall be applied within their rating based on a service factor de 1.0. In thoseapplications requiring a prolonged overload capacity, the use of a higher

horsepower rating is required to avoid the reduction of insulation and bearing lifeassociated with operation above the 1.0 service factor.

3.3.11 All motors shall have their windings star – connected and shall have identicalinsulation levels. Stator windings of MV motors shall be preformed and be madeof rectangular copper conductors. MV rotors shall be copper. Motors withaluminum frames are unacceptable.

3.3.12 All motors shall have a class F insulation, with a class B temperature rise at thecontinuous required nameplate rating.


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3.3.13 A terminal box of sturdy construction shall be provided with ample space for

connecting the cables as indicated on the requisition order which, due to voltagedrop, short circuit, large number of duct cables, can be twice that considerednormal by manufacturer.

Terminal boxes shall be watertight. Transition box between cable and motor boxis not acceptable. For MV motors all terminal boxes shall be made of steel.Terminal boxes made of cast iron are not acceptable. The main terminal box shallbe of the non – compound filled design, phase insulated, phase segregated orphase separated type.

3.3.14 MV Motors shall be designed to be controlled by vacuum contactors. Motors of1 500 kW (2 000 hp) and above shall be provided with surge suppressors.

3.3.15 Within the application limits, about 285 kW – 3 600 rpm, 2 240 kW . – 1 800 rpm,motors shall be provided with ball and roller bearing with suitable grease nipplesand relief devices. Minimum relubrication interval to be 4 000 hours for horizontalmotors and 2 000 hours for vertical motors.

3.3.16 Motors of 75 hp and above, shall be provided with space heaters. Voltage supplyshall be 120 V ac.

3.3.17 Standardization of motors of the same size and manufacturer shall be pursued.

3.4 Cables And Wires

3.4.1 Cables and wires shall conform to PDVSA N – 201, Section 14, 15 and EngineeringDesign Guide PDVSA 90619.1.057. Cables shall be designed, manufactured andtested according to the additional provisions of AEIC CS5 to the ICEA S – 66 – 524standard.

3.4.2 Distribution feeders and branch feeders to motors shall be done, whereverpossible, by underground distribution system, for inherent protection against fireand mechanical damage.

3.4.3 13.8 and 34.5 kV feeder shall be directly buried, using armored cables. Motorbranches 4.16 and 0.480 kV shall preferably be buried directly in the ground.

Underground cable ducts shall be avoided in hazardous areas due to increasedrisks. Also it will affect the cable current rating unfavorably.

3.4.4 Directly buried cables shall be identified with lead trips, approximately 20 mmwide, at each end and then over their entire lenghth at 5 m intervals and at allpoints where they enter and leave ducts and at changes in direction, etc.

3.4.5 In areas where the possibility of soil contamination is present, cables shall beprovided with a lead sheath, and appropriate external cover to prevent electrolyticcorrosion

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3.4.6 Above ground cables are allowed in process units having equipment installed on

tall structures, and in soil with high probability of contamination where the use ofcable lead sheath is not possible, all agreed with the owner ’s engineer. Cablesshall be supported by cable racks, trays or cable ladders all the way up to theirterminations. All materials used shall be properly protected against corrosion,such as hot – dip galvanized materials, stainless steel, reinforced fiberglass, fireresistant polyester, depending on severity of environmental conditions. Cabletrays and conduits shall conform PDVSA N – 201, Section 14.

3.4.7 Above ground cables are also allowed if underground cabling leads to impracticalor uneconomic solutions because of excessive ground space requirements, orhigh freatic level.

3.4.8 A technical and economic analysis shall be carried out for the selection of aboveground, underground or a combined above ground and underground cablesystem. The result shall be approved by Pequiven.

3.4.9 All power, lighting and grounding cables shall have copper conductors. Type andsize of cable shall be agreed with the owner ’s engineer for standardizationreasons. Minimum size shall be as indicated in PDVSA 90619.1.057.

3.4.10 MV cables shall be copper cross linked polyethylene (XLPE) or ethylenepropylene rubber EPR insulated (90° C) and PVC jacketed, shielded type. LVcables shall be PVC, PVC (75° C). Distribution cables (13.8 and 34.5 kV) shall beof one core construction. Feeders and motor branch enclosed in duct (4.16 and

0.480 kV) shall be three core up to the size AWG No. 1/0. Size AWG No. 2/0 andabove shall be one core.

3.4.11 For the sizing of cables, thermal short circuit capacity, voltage drop, current ratingand derating factors shall be taken into consideration. The latter will take intoaccount deviation for ground/ ambient temperature, deviation for soil thermalresistivity, grouping of cables in ducts or trenches and the shield losses.A soilaverage temperature and thermal resistivity survey shall be conducted prior toperform the ampacity calculations.

3.4.12 Conductor short – circuit capability shall be calculated with the maximum expected

three – phase shortcircuit current circulating for a time equal to the backupprotective relay setting, according to ICEA P – 32 – 382. Shield and armorshort – circuit capability shall be calculated with maximum expected phase toground short – circuit current for a time equal to the backup protective relay settingfor solidly grounded neutral systems, and for the rated current and time of theneutral grounding resistor for low resistance grounded systems. Calculation shallbe made according to ICEA P – 45 – 482.

3.4.13 Cables at 600 V and below, and feeders to motors above 600 V, shall not beincreased in size because of short circuit duty.

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3.4.14 When installing shielded cable, metallic shielding must be solidly grounded. For

safe and effective operation, the shielding shall be grounded at each end of thecable and at each splice. For short lengths, grounding at one point may beconsidered with the owner’s engineer approval.

3.4.15 Grounding cables between equipment and ground net shall be PVC covered(green color), as protection against electrolytic corrosion. Ground net conductorsshall be bare copper.

3.4.16 Instrument and telecommunication cables shall be laid in trenches or traysseparated from those used for MV and/or LV cables.

3.4.17 Conductors No. 14 AWG and larger shall be stranded. Wire smaller than No. 12AWG shall not be used in both lighting and power systems.

3.5 Lighting

3.5.1 Lighting system shall conform to PDVSA N – 201, Section 13. Lighting levels shallbe as per COVENIN 2 249 “Iluminancias en Tareas y Areas de Trabajo”.

3.5.2 As far as practical, energy efficient fluorescent luminaries in white color shall, ingeneral, be used for plant lighting.

3.5.3 High pressure discharge lamps (sodium vapor type fixtures) may be used whereflood lighting and street lighting be required.

3.5.4 Low pressure sodium discharge lamps shall not be used, as they constitute a fire

hazardous in the event of breakage.3.5.5 For standardization reasons the same type of fittings shall be used in all plant

areas.

3.5.6 For the control of lamp groups in individual rooms of a process building, or whereotherwise necessary, local lighting switches shall be provided.

3.5.7 Lighting for outdoor operating areas and streets shall be automatic controlled byphotocell. An auto – on – off selector switch shall be located at the controller locationto permit manual control of the lighting (PDVSA N – 201, Section 13.21).

3.5.8 All lighting voltage for process plants shall be 208 V, 3 – phase.

3.5.9 Lighting transformers and lighting panels shall be located inside of a switch house.3.5.10 Fixed emergency lighting shall be installed in control rooms, switch rooms, fire

fighting station, first – aid rooms, watchmen’s offices, the main entrances and in allother buildings and areas when required for safety reasons.

3.6 Power and Convenience Outlets

3.6.1 For maintenance purposes an adequate number of 3 – phase power outlets formovable equipment and single phase convenience outlets for the supply ofportable tools and hand lamps shall be provided at suitable locations.

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PDVSA N –252

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3.6.2 Convenience outlets shall have a standard supply voltage equal to the voltage

selected for normal lighting. (208 and/or 120 V in agreement with the owner’sengineer).

3.6.3 Hand torches shall be provided for all locations where operating personnel will bepresent. The equipment shall consist of fixed charging units with sockets andplug – in – type hand torches suitable for classified area.

3.7 Metering Equipment

3

PDVSA N-252 1996

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