Type MVGC

Voltage Regulating Relay

Service Manual

R8021G

Service ManualType MVGC

Voltage Regulating Relay

HANDLING OF ELECTRONIC EQUIPMENT

A person's normal movements can easily generate electrostatic potentials of several thousand volts.Discharge of these voltages into semiconductor devices when handling electronic circuits can causeserious damage, which often may not be immediately apparent but the reliability of the circuit will havebeen reduced.

The electronic circuits of ALSTOM T&D Protection & Control Ltd products are completely safe fromelectrostatic discharge when housed in the case. Do not expose them to the risk of damage bywithdrawing modules unnecessarily.

Each module incorporates the highest practicable protection for its semiconductor devices. However, if itbecomes necessary to withdraw a module, the following precautions should be taken to preserve the highreliability and long life for which the equipment has been designed and manufactured.

1. Before removing a module, ensure that you are at the same electrostatic potential as the equipmentby touching the case.

2. Handle the module by its front-plate, frame, or edges of the printed circuit board.Avoid touching the electronic components, printed circuit track or connectors.

3. Do not pass the module to any person without first ensuring that you are both at the sameelectrostatic potential. Shaking hands achieves equipotential.

4. Place the module on an antistatic surface, or on a conducting surface which is at the samepotential as yourself.

5. Store or transport the module in a conductive bag.

More information on safe working procedures for all electronic equipment can be found in BS5783 andIEC 60147-0F.

If you are making measurements on the internal electronic circuitry of an equipment in service, it ispreferable that you are earthed to the case with a conductive wrist strap.Wrist straps should have a resistance to ground between 500k 10M. If a wrist strap is not available,you should maintain regular contact with the case to prevent the build up of static. Instrumentation whichmay be used for making measurements should be earthed to the case whenever possible.

ALSTOM T&D Protection & Control Ltd strongly recommends that detailed investigations on the electroniccircuitry, or modification work, should be carried out in a Special Handling Area such as described inBS5783 or IEC 60147-0F.

4CONTENTS

SAFETY SECTION 6

1 APPLICATION 101.1 Operating Sequences 101.2 Voltage regulating schemes 111.3 Optional external connections 111.3.1 Independent/parallel control 111.3.2 Auto /non-auto 121.4 Line drop compensation for parallel transformers 12

2 SETTINGS 152.1 Reference voltage setting, VS 152.2 Deadband setting, V % 152.3 Initial delay setting 162.4 Intertap delay 162.5 Line drop compensation settings, VR and VXL 162.6 Parallel compensating voltage, VC 172.7 Load shedding 172.8 Undervoltage and overvoltage supervision, VU and VO 172.9 Overcurrent detector, IL 172.10 Circulating current detector, IC 182.11 Internal setting switches 18

3 INSTALLATION 19

4 COMMISSIONING 204.1 Commissioning preliminaries 204.2. Commissioning tests 214.2.1 Equipment and input requirements 214.2.2 General 224.2.3 Regulated voltage setting (VS) 224.2.4 Percentage deviation (V%) = 1/2 percentage deadband width. 224.2.5 Under voltage blocking (80% VS) 234.2.6 Load shedding 234.2.6.1 3%, 6%, 9% of VS 234.2.6.2 +3%, +1.5%, 1.5% of VS 234.2.7 Time delays 244.2.7.1 Initial time delay 244.2.7.2 Inter tap time delay 254.2.8 Line drop compensation 264.2.8.1 Resistive compensation VR 264.2.8.2 Reactive compensation VXL 274.2.9 Parallel compensating voltage VC 274.2.10 Supervision circuits 274.2.11 Load check for MVGC relay 29

55 MAINTENANCE 305.1 Preliminary checks 305.2 Functional check using the self test facility 305.2.1 Regulated voltage setting 305.2.2 Deadband setting V% 315.2.3 Initial time delay 315.2.4 Intertap time delay 315.2.5 Undervoltage detector VU 315.2.6 Overvoltage detector VO 315.2.7 Fixed 80% undervoltage detector 315.2.8 Alarm timer 32

6 PROBLEM ANALYSIS 326.1 Servicing instructions 326.2 Equipment and input requirements: 326.3 Test procedure 326.3.1 Regulated voltage setting VS 326.3.2 Deadband setting V% 336.3.3 Initial delay 336.3.4 Intertap delay 346.3.5 Fixed 80% undervoltage blocking 346.3.6 Line drop compensation 346.3.7 Parallel compensating voltage, VC 356.3.8 Load shedding/voltage boost 356.3.9 Supervision circuits 356.4 Re-calibration 37

7 COMMISSIONING TEST RECORD 39

REPAIR FORM 43

6SAFETY SECTION

This Safety Section should be read before commencing any work on the equipment.

Health and safety

The information in the Safety Section of the product documentation is intended toensure that products are properly installed and handled in order to maintain them ina safe condition. It is assumed that everyone who will be associated with theequipment will be familiar with the contents of the Safety Section.

Explanation of symbols and labels

The meaning of symbols and labels which may be used on the equipment or in theproduct documentation, is given below.

Caution: refer to product documentation Caution: risk of electric shock

Protective/safety *earth terminal

Functional *earth terminal.Note: this symbol may also be used for a protective/safety earth terminal if that terminal is part of aterminal block or sub-assembly eg. power supply.

*Note: The term earth used throughout the product documentation is the directequivalent of the North American term ground.

Installing, Commissioning and ServicingEquipment connections

Personnel undertaking installation, commissioning or servicing work on thisequipment should be aware of the correct working procedures to ensure safety.The product documentation should be consulted before installing, commissioning orservicing the equipment.

Terminals exposed during installation, commissioning and maintenance may presenta hazardous voltage unless the equipment is electrically isolated.

If there is unlocked access to the rear of the equipment, care should be taken by allpersonnel to avoid electric shock or energy hazards.

Voltage and current connections should be made using insulated crimp terminationsto ensure that terminal block insulation requirements are maintained for safety. Toensure that wires are correctly terminated, the correct crimp terminal and tool for thewire size should be used.

7Before energising the equipment it must be earthed using the protective earthterminal, or the appropriate termination of the supply plug in the case of plugconnected equipment. Omitting or disconnecting the equipment earth may cause asafety hazard.

The recommended minimum earth wire size is 2.5 mm2, unless otherwise stated inthe technical data section of the product documentation.

Before energising the equipment, the following should be checked:

Voltage rating and polarity;

CT circuit rating and integrity of connections;

Protective fuse rating;

Integrity of earth connection (where applicable)

Equipment operating conditions

The equipment should be operated within the specified electrical and environmentallimits.

Current transformer circuits

Do not open the secondary circuit of a live CT since the high voltage producedmay be lethal to personnel and could damage insulation.

External resistors

Where external resistors are fitted to relays, these may present a risk of electric shockor burns, if touched.

Battery replacement

Where internal batteries are fitted they should be replaced with the recommendedtype and be installed with the correct polarity, to avoid possible damage to theequipment.

Insulation and dielectric strength testing

Insulation testing may leave capacitors charged up to a hazardous voltage. At theend of each part of the test, the voltage should be gradually reduced to zero, todischarge capacitors, before the test leads are disconnected.

Insertion of modules and pcb cards

These must not be inserted into or withdrawn from equipment whilst it is energised,since this may result in damage.

Fibre optic communication

Where fibre optic communication devices are fitted, these should not be vieweddirectly. Optical power meters should be used to determine the operation or signallevel of the device.

8Older ProductsElectrical adjustments

Equipments which require direct physical adjustments to their operating mechanism tochange current or voltage settings, should have the electrical power removed beforemaking the change, to avoid any risk of electric shock.

Mechanical adjustments

The electrical power to the relay contacts should be removed before checking anymechanical settings, to avoid any risk of electric shock.

Draw out case relays

Removal of the cover on equipment incorporating electromechanical operatingelements, may expose hazardous live parts such as relay contacts.

Insertion and withdrawal of extender cards

When using an extender card, this should not be inserted or withdrawn from theequipment whilst it is energised. This is to avoid possible shock or damage hazards.Hazardous live voltages may be accessible on the extender card.

Insertion and withdrawal of heavy current test plugs

When using a heavy current test plug, CT shorting links must be in place beforeinsertion or removal, to avoid potentially lethal voltages.

Decommissioning and Disposal

Decommissioning: The auxiliary supply circuit in the relay may include capacitorsacross the supply or to earth. To avoid electric shock or energyhazards, after completely isolating the supplies to the relay(both poles of any dc supply), the capacitors should be safelydischarged via the external terminals prior to decommissioning.

Disposal: It is recommended that incineration and disposal to watercourses is avoided. The product should be disposed of in a safemanner. Any products containing batteries should have themremoved before disposal, taking precautions to avoid shortcircuits. Particular regulations within the country of operation,may apply to the disposal of lithium batteries.

9Technical SpecificationsProtective fuse rating

The recommended maximum rating of the external protective fuse for this equipmentis 16A, Red Spot type or equivalent, unless otherwise stated in the technical datasection of the product documentation.

Insulation class: IEC 61010-1: 1990/A2: 1995 This equipment requires aClass I protective (safety) earthEN 61010-1: 1993/A2: 1995 connection to ensure userClass I safety.

Installation IEC61010-1: 1990/A2: 1995 Distribution level, fixedCategory Category III installation. Equipment in(Overvoltage): EN 61010-1: 1993/A2: 1995 this category is qualification

Category III tested at 5kV peak, 1.2/50s,500, 0.5J, between all supplycircuits and earth and alsobetween independent circuits.

Environment: IEC 61010-1: 1990/A2: 1995 Compliance is demonstrated byPollution degree 2 reference to generic safetyEN 61010-1: 1993/A2: 1995 standards.Pollution degree 2

Product safety: 73/23/EEC Compliance with the EuropeanCommission Low VoltageDirective.

EN 61010-1: 1993/A2: 1995 Compliance is demonstratedEN 60950: 1992/A11:1997 by reference to generic safety

standards.

10

Section 1 APPLICATION

1.1 Operating Sequences

For a large voltage deviation outside the set deadband the tap changer is required toperform a multiple tap change sequence. Two main methods of controlling such asequence using relay type MVGC 01 are as follows:-

Method 1

Figure 1

This is the standard method and is suitable where rapid correction of large voltagedeviations is required to give better regulation.

The initial delay setting determines the delay in initiating any tap change sequence.After an initiating pulse of 1 second the inter-tap delay setting determines the delaybetween subsequent tap change initiations. This process continues until the systemvoltage is restored to within the deadband limits.

Method 2

For this method a tap changer operated, normally closed contact is connected suchas to interrupt the measuring voltage supply to terminal 17 and 18. This operates the80% undervoltage inhibit circuitry to reset the initial delay timer during each tapchange step and hence the inter-tap delay feature is not used, i.e. set for continuous,non-pulsing by setting intertap delay less than or equal to zero.

The normally closed contact is usually operated by direct movement of the tapchangers motor mechanism using the directional sequence switch.

t

t

tInter-tapdelay

Initial time delay T

definite or inverse

Voltagedeviation

Tap changeincrement

V%

VS

VRR

Measuring VT

1 Second initiating pulse at intervalsset by inter-tap delay.

11

Figure 2

For inverse initial delays the time delay between tap changes gets progressivelylonger as the voltage deviation decreases. With definite initial delay settings the timedelay between each tap change is the fixed initial delay setting.

Method 2 rapidly corrects large voltage deviations, but greatly extends the total timethe voltage remains outside the deadband and is suitable only where load conditionswill tolerate this.

1.2 Voltage regulating schemes

Where Method 2 is used to control a multiple tap change sequence then the relaysundervoltage relay contact will operate during each tap change step. To avoidunwanted alarm signals the undervoltage contact may be used to initiate a timedelayed auxiliary relay type MVUA (see Publication R6039) which is typically set for12 seconds delay on operate. Relay types MVGC and MVUA are availableconnected together as a MIDOS scheme.

1.3 Optional external connections

1.3.1 Independent/parallel control

Where transformers connected in parallel are controlled using the minimumcirculating current principle, independent operation is selected by shorting theinterconnecting pilot wires as below.

Figure 3

Contact A OPEN for parallel controlCLOSED for independent control

Contact B OPEN when local lv OCB is closedCLOSED when local lv OCB is open

Voltagedeviation

V%

VS

VRR

MeasuringVT

Inter-tap delay 0 gives a non-pulsing output and is also suitablefor continuous adjusting equipment.Initial delay of VRR set for definite time gives settime delay between each tap change initiation.

T1

T1

T1

T1

Contact opens during tapchanger operation

T1 is determined by deviationfrom VS setting

23

24

A B To pilot loop

12

1.3.2 Auto /non-auto

Non-auto or manual control can be obtained by isolating the common terminal of therelays raise/lower output contacts.

Figure 4

1.4 Line drop compensation for parallel transformers

Where parallel transformers feed distribution lines and line drop compensation isrequired, it is sometimes necessary to parallel the line drop compensation (LDC)CT inputs of each relay in the scheme.

This ensures that each relay measures a current which is proportional to the loadcurrent of the power transformer (PT) irrespective of the number of paralleltransformers in the scheme. Therefore, when the number of transformers supplying theload changes, the LDC settings on the relay will not need to be adjusted.

Traditionally, when paralleling LDC inputs, it was assumed that line load currentswould split equally between paralleled LDC circuits as LDC impedances wereconsidered large compared to the interconnecting lead resistances.

The MVGC 01 has a LDC burden of 0.4 VA at rated current. This is insufficient toensure that interconnecting lead resistances are neglible. Therefore, when the LDCcircuits are paralleled, it is necessary to pad out the burden of the LDC circuits by useof an external resistor.

It should be remembered that when the LDC input CTs are paralleled, the LDC circuitswill not see any components of the circulating current between parallel transformers,therefore negative reactance compensation cannot be used to combat circulatingcurrent. Only the pilot method of circulating current control or external means ofcontrol can be employed.

The following notes demonstrate how the LDC CTs may be paralleled on anMVGC 01 relay.2RL1 = Lead loop resistance between CT1 and AVR1 plus resistance of AVR

circulating current CT input (terminals 25 and 26 of MVGC 01).XM1 = CT1 magnetising impedance which will be ignored due to its high value

when CT is unsaturated.RCT1 = CT1 winding resistance.RL = Resistance of one lead between AVRs (including any interposing CTs).CT1 = Driving CT (T1 loaded).CT2 = Idling CT (T2 loaded).2IL = Current flowing in line(s) fed by T1/T2 which creates line voltage drop,

which is to be compensated for.

1

5

ACommonMVGC 3

Raise

Lower

13

EQUIVALENT CIRCUIT DIAGRAM FOR 2 MVGC 01 RELAYS WITH PARALLELED LDCINPUTS.

RLDC.(2RL+ RLDC)I1 = 2IL . RLDC + (2RL + RLDC)

RLDC= 2IL . (RLDC.(2RL + RLDC)

RLDC (RL + RLDC)

(2X + 1) RL(X + 1) RLDC

Ideally I1 should equal IL (also I2 = IL), but since RL is not zero, I1 will exceed IL.The required value of X to bring I1 down to 1.05IL will be determined by:

(2X + 1)(X + 1)

1.05X + 1.05 = 2X + 1

0.05 = 0.95X

X = 0.0526

Therefore we require X < 0.0526 for I1 < 1.05ILEXAMPLE 1.

Application of two AVRs (5A rated), using 5A:0.5A interposing transformers toisolate the individual line CTs.

Assume:

= IL . where X =

1.05IL = IL

RCT1

2IL

XM1

2RL1

2IL

RCT2

XM2

2RL2

CT1 CT2

RL

AVR2(MVGC 01)

RLDC

2828

AVR1(MVGC 01)

RLDC

RL 2727 I1 I2

RL

RL

14

is equivalent to:

2(RICT2 + RL')100

Therefore:

(RICT2 + RL')100

MVGC 01 burden for LDC = 0.4 VA at InTherefore:

0.452

= 0.016and

RLRLDC

Therefore:

(RICT2 + RL')100

or RLDC must be increased to RLDC' via a series resistor so that:

RLDC' > 19 (RICT1 + (RICT2 + RL'))100

eg. RICT1 = 0.02RICT2 = 0.3RL' = 0.2

This gives:

RLDC' > 19(0.02 +(0.03 + 0.2)) 100

> 0.475

RLDC' = RLDC + RsTherefore:

Rs > 0.475 0.016> 0.46

Choose a value of 0.5.

2RL = 2RICT1 +

RL = RICT1 +

RLDC =

X = < 0.0526

RICT1 + < 0.0526RLDC

5:0.5A

RICT1

5:0.5A

RICT2 RL' RICT2

RL'

RICT1

15

Required continuous current capability

2In = 10A

Therefore minimum current rating = 50W and, allowing a 50% derating of thecomponent, a 100W resistor is required.

THEREFORE USE RS = 0.5 100W.Note: Rs should withstand the maximum main CT secondary rms current for a

minimum of three seconds. The maximum output of the main CTs should notexceed three times the steady state current through its connected burden andCT resistance to cause saturation.

EXAMPLE 2.

Application of 2 AVRs (1A rated) with direct paralleling

RL = 50m 2.5mm2 Cu = 0.370.412

RLRLDC'

RLDC' > 19RL

RLDC' > 7.03

Therefore: Rs > 7.03 0.4> 6.63

Choose a value of Rs = 6.8.Required continuous rating = 2In = 2A

Therefore required continuous power rating of Rs = 27.2 W.

Allowing a minimum power derating of 50%, use a resistor rated at 75W.

THEREFORE USE Rs = 6.8 75 WNote: See short time current withstand note given in example 1.

Section 2 SETTINGS

Note: All controls whether being used or not, should be set at some point withintheir calibrated range and not set to either end stop.

2.1 Reference voltage setting, VSThe reference voltage setting is selected by thumbwheel switches in 1.0 volt stepsbetween 100 and 139 volts.

2.2 Deadband setting, V %This is set such that the nominal tap step increment is typically between 50% and80% of the set deadband width, depending on preferred practice.

Tap step increment % = preferred ratio x set deadband width

e.g. Nominal tap step increment = 1.4%

Preferred ratio = 70%

RLDC = = 0.4

X = < 0.0526 where RLDC' = RLDC + Rs

16

1.470

Hence V % = 1% of set VS2.3 Initial delay setting

The time delay to initiate a tap change sequence is set by the initial delay setting andis continuously adjustable between 1.2 and 12 seconds or 12 and 120 secondsdepending on the range selected. A setting switch determines either a definite or aninverse time characteristic.

For inverse characteristic the set time delay defines the operating time delay at theedge of deadband, N = 1. Larger voltage deviations give correspondingly fasteroperating times as given by IDMT characteristic, Figure 5, in Publication R6021.

initial delay settingN

Where N = Voltage deviation from VS in multiples of V% setting

i.e. N = 1 defines edge of deadband

2.4 Intertap delay

Where a multiple tap change sequence is required then the time delay betweensuccessive tapping outputs can be set between zero and 10 seconds.

This is normally set to be slightly longer than the operating time of the tap changermechanism. Setting the intertap delay to less than zero then the output contacts arenon-pulsing as previously described in Section 1.1.

2.5 Line drop compensation settings, VR and VXLThese controls are set such that the voltage at a point remote to the tap changingtransformer can be regulated for varying load conditions.

The resistive setting is continuously adjustable between 0 and 24 volts at ratedcurrent.

The reactive setting is continuously adjustable between 0 and 24 volts, or 0 and 48volts at rated current, depending on the range selected.

3.IP.R 3.IP.XLVT ratio VT ratio

Where IP = primary rated current of line CT.R = resistive component of line impedance

XL = reactive component of line impedanceVT ratio = ratio of primary to secondary voltages of line VT

A switch is provided, allowing selection of reverse reactance for control oftransformers connected in parallel. For reverse reactance control the settings are nowas below:

3.IP.XTVT ratio

Where XT = reactance of transformer

3.IP R Cos + XL Sin + XT Sin VT ratio Cos

Where Cos = power factor of load

Deadband width = x 100 = 2% of VS

VR = VXL =

Inverse operating time =

VXL (reverse) =

Now VR = .

17

The above shows that the effective VR compensation can vary significantly for varyingpower factors. Reverse reactance control of parallel transformers is used wheretransformers are dissimilar or at different locations and the power factor variation isnot too great.

2.6 Parallel compensating voltage, VCAn alternative method of achieving stable control of paralleled transformers is tominimise the reactive circulating current IC. This is achieved by the introduction of aparallel compensation voltage setting VC which is proportional to IC.

The VC setting is continuously adjustable between 0 and 24 volts, or 0 and 48 voltsdepending on the range selected, for reactive rated current applied to the circulatingcurrent inputs. The VC setting is determined during commissioning procedures suchthat optimum stability is obtained for paralleled transformers. An approximate settingis given by.

3.IP.XTVT ratio

Circulating current control using VC setting allows both resistive and reactivecomponents of line drop compensation to be utilised and is independent of powerfactor variations.

2.7 Load shedding

Three levels of load shedding or voltage targets are available, either 3%, 6% or9% of VS or +3%, +1.5% or 1.5% of VS, the latter incorporating a 1.5% or 3%voltage boost. The required amount can be selected by either a local or remoteswitch and LED indication of the selected value is given on the relay.

2.8 Undervoltage and overvoltage supervision, VU and VOIndependent controls are provided to detect undervoltage and overvoltageconditions. The settings are continuously variable over the following ranges:

VU : 80 120 volts

VO : 110 160 volts

Independent output contacts are provided for each function. In addition, operation ofthe overvoltage detector blocks raise operations, to prevent excessive voltage onbusbars local to the transformer. Similarly the undervoltage detector blocks loweroperations thus defining the normal working limits of the transformer and onlyallowing tap changes in such a direction as to restore the regulated voltage.

2.9 Overcurrent detector, ILThe overcurrent detector setting IL is continuously variable between 100% and 200%of INL. Where the total load current through a transformer exceeds this setting thenan internal relay operates blocking both raise and lower operations thus preventingtap changer operation for fault or overload current through the transformer.

Note: Plugs for INL and INC should both be set to the same value (1A or 5A).INL is selected as either 1A or 5A by the plug bridge on the front of the relay.

VC =

18

2.10 Circulating current detector, ICThe excessive circulating current detector setting is continuously variable between 5%and 50% of IN. The detector can be used to operate where a given tap disparity isexceeded. Where required, operation of a blocking relay for both raise and loweroperations can be selected by an internal setting switch. Another switch is provided,allowing the circulating current detector to operate an alarm output relay andoperation can be either instantaneous or time delayed. A third switch can be used toprevent any alarm initiation from the IC circuits.

Note: Plugs for INL and INC should both be set to the same value (1A or 5A).INC is selected as either 1A or 5A by the plug bridge on the front of therelay.

2.11 Internal setting switches

Three internal setting switches are provided to give the following options:

Switch Position A Position B

S6 VO and VU settings are VO and VU settings areindependent of selected reduced by selectedload shedding load shedding factor

S7 Indication only of Excessive circulatingexcessive circulating current gives indicationcurrent and also operates

blocking relay to preventtap change initiation

S8 Excessive circulating Excessive circulatingcurrent causes alarm current causesrelay to operate after instantaneous operationtime delay of 180 seconds of alarm relay

Note: S8 is only effective with S10 in position A

S9 Out of dead band signal Voltage out of deaddoes not initiate 180 band for > 180 secondssecond timer gives alarm output

S10 Excessive circulating Excessive circulatingcurrent operates the current does not operatealarm as defined by the alarmthe position of S8

The switches are found at the bottom of the relays pcbs as follows:

Switch PCB Location

S6 ZJ0049 Bottom centreS7 ZJ0044 Bottom frontS8 ZJ0044 Bottom rearS9 ZJ0044 Bottom rear-frontS10 ZJ0044 Bottom rear-middle

Note: Earlier relays are not fitted with the switches S9 and S10. On these relays S9is effectively in position B and S10 is effectively in position A.

19

Section 3 INSTALLATION

3.1 Protective relays, although generally of robust construction, require careful treatmentprior to installation and a wise selection of site. By observing a few simple rules thepossibility of premature failure is eliminated and a high degree of reliability can beexpected.

3.2 The relays are either despatched individually or as part of a panel/rack mountedassembly, in cartons specifically designed to protect them from damage.

Relays should be examined immediately they are received to ensure that no damagehas been sustained in transit. If damage due to rough handling is evident, a claimshould be made to the transport company concerned immediately, and the nearestALSTOM T&D Protection & Control Ltd representative should be promptly notified.Relays which are supplied unmounted and not intended for immediate installationshould be returned to their protective polythene bags.

3.3 Care must be taken when unpacking and installing the relays so that none of theparts are damaged or their settings altered, and they must at all times be handled byskilled persons only.

Relays should be examined for any wedges, clamps or rubber bands necessary tosecure moving parts to prevent damage during transit and these should be removedafter installation and before commissioning.

Relays which have been removed from their cases should not be left in situationswhere they are exposed to dust or damp. This particularly applies to installationswhich are being carried out at the same time as constructional work.

3.4 If relays are not installed immediately upon receipt they should be stored in a placefree from dust and moisture in their original cartons and where de-humidifier bagshave been included in the packing they should be retained. The action of the de-humidifier crystals will be impaired if the bag has been exposed to ambientconditions and may be restored by gently heating the bag for about an hour, prior toreplacing it in the carton.

Dust which collects on a carton may, on subsequent unpacking, find its way into therelay; in damp conditions the carton and packing may become impregnated withmoisture and the de-humidifying agent will lose its efficiency.

Storage temperature 25C to +70C.

3.5 The installation should be clean, dry and reasonably free from dust and excessivevibration. The site should preferably be well illuminated to facilitate inspection.

An outline diagram is normally supplied showing panel cut-outs and hole centres.For individually mounted relays these dimensions will also be found in publicationR6018.

Publication R7012 is a Parts Catalogue and Assembly Instructions. This document willbe useful when individual relays are to be assembled as a composite rack or panelmounted assembly.

20

Section 4 COMMISSIONING

4.1 Commissioning preliminaries

Electrostatic Discharges (ESD)

The relay uses components which are sensitive to electrostatic discharges.When handling the module, care should be taken to avoid contact with componentsand electrical connections. When removed from the case for storage, the moduleshould be placed in an electrically conducting anti-static bag. See fullrecommendations inside the front cover of this manual.

Inspection

Carefully examine the module and case to see that no damage has occurred duringtransit. Check that the relay serial numbers on the module and case cover areidentical and that the model number and rating information are correct.

Wiring

Check that the external wiring is correct to the relevant relay diagram or schemediagram. The relay diagram number appears inside the case. Note that shortingswitches shown on the relay diagram are fitted internally across the relevant caseterminals and close when the module is withdrawn. It is essential that such switchesare fitted across all CT circuits.

Earthing

Ensure that the case earthing connection above the rear terminal block is used toconnect the relay to a local earth bar.

Insulation

The relay and its associated wiring, may be insulation tested between:

all electrically isolated circuits

all circuits and earth

An electronic or brushless insulation tester should be used, having a dc voltage notexceeding 1000V. Accessible terminals of the same circuit should first be strappedtogether. Deliberate circuit earthing links, removed for the tests, subsequently must bereplaced.

Electrical tests

Applicable to all relays involving current transformers:

DANGER

DO NOT OPEN CIRCUIT THE SECONDARY CIRCUIT OF A CURRENT TRANSFORMERSlNCE THE HIGH VOLTAGE PRODUCED MAY BE LETHAL AND COULD DAMAGEINSULATION.

When type MMLG test block facilities are installed, it is important that the sockets inthe type MMLBO1 test plug, which correspond to the current transformer secondarywindings, are LINKED BEFORE THE TEST PLUG IS INSERTED INTO THE TEST BLOCK.Similarly, a MMLB02 single finger test plug must be terminated with an ammeterBEFORE IT IS INSERTED to monitor CT secondary currents.

21

Terminal allocation of relay

Terminals of the relay are usually allocated as follows but not all relay applicationswill use all these terminals.

TerminalsReference ac voltage, VN 17, 18

Auxiliary ac voltage, Vx (110/125V) 15, 14(220/250V) 13, 14

Input from line CT for line drop compensation 27, 28

Input from line CT for circulating current control 25, 26 (in serieswith 27, 28)

Input from circulating current pilots 23, 24

Load shedding control contacts. Common 22(Internally connected to Vx 3% or +3% 19circuit) 6% or +1.5% 20

9% or 1.5% 21

Tap changer control contacts. Common 3Raise 1Lower 5

Output contacts: Undervoltage 2 & 4Overvoltage 7 & 9

Alarm for voltage outside deadband for 3 6 & 8minutes or for excessive circulating current 10 & 12either instantaneously or for 3 minutes

4.2. Commissioning tests

Typical application diagrams are shown in Figures 8 and 9

4.2.1 Equipment and input requirements

AC auxiliary supply suitable to supply a 30VA load. The frequency (Hz) mustbe the same as the Vx and Hz given on the module rating label mounted in thelower handle. The voltage must be set for the selected voltage input, ie. 110V for110/120V input.

Stable measuring ac voltage supply of rated frequency with a fine adjustment controlto operate between 70 and 170 volts ac into a 3VA load.

High accuracy TRMS ac voltmeter, ac voltage accuracy less than 0.1% at full range,50 or 60Hz.

Stopwatch or electronic timer

Two pole switch and resistor (typically 5k 2W).For testing the line drop compensator controls it is necessary to be able to phase shiftthe angle between the regulated voltage supply and the current.

The following equipment is necessary:

Three phase 440V supply

Sinusoidal current source from 0 to 10 amps ac into a 10VA burden at rated current.

Phase shifter (440/240V line to line) and an adjustable single phase voltagetransformer (variac) to supply the regulated voltage supply.

22

Phase angle meter, accuracy better than 2.

AC ammeter, range 0 to 10 amps.

4.2.2 General

Set all controls to the required settings.

NOTE: The tens thumbwheel switch on the VS setting control can be set to anynumber between 0 and 9, but positions 3 to 9 all produce the same settingof 3.

If a test block is not used to isolate the normal VT, auxiliary, CT and any othersupplies, ensure that there is no accidental connection of test and normal suppliesand the CT is not open circuited. Check that the auxiliary ac supply is the correctvoltage and wire to terminals 15 and 14 (110/125V) or to terminals 13 and 14(220/250V). Wire the regulated voltage supply to terminals 17 and 18 and the highaccuracy voltmeter either to the same terminals or to the monitor sockets on the frontof the relay.

4.2.3 Regulated voltage setting (VS)

Set the TEST/NORMAL switch to NORMAL.

Energise the auxiliary voltage supply and check that the Volts Low indicator lamp islit.

Energise the regulated voltage supply and adjust the voltage to the nominal settingvoltage, as set on the VS thumbwheel switches. Check that the Volts Low, VoltsHigh and Tap lamps are not lit. Slowly increase the regulated voltage supply untilthe Volts High lamp just lights and note this voltage (VH). A fine control andaccurate voltmeter are essential to establish this voltage with accuracy.

Decrease the regulated supply and check that the Volts High lamp goes outimmediately.

Continue lowering the voltage until the Volts Low lamp just lights and note thisvoltage (VL).Actual voltage setting = 1/2 (VH + VL) voltsTolerance: 0.5%

NOTE: The above accuracy limit makes no allowance for instrument error andpossible poor waveform which may be experienced during commissioning.

In service it may be found necessary to change the setting voltage VS. It is thereforeadvisable to check all positions of the thumbwheel switches using the aboveprocedure. This involves fourteen checks, ten for the units and four for the tens.

NOTE: The tens switch cannot be set higher than 3.

Reset VS to the required setting.

4.2.4 Percentage deviation (V%) = 1/2 percentage deadband width.Calculate the actual percentage deviation using the voltages VH and VL measured inthe test above and the formula below.

12VS

Tolerance: 0.2 of the value set on the Percentage Deviation Control.

Actual percentage deviation = (VH VL) x 100%

23

4.2.5 Under voltage blocking (80% VS)

This is the voltage below which any further tap change initiation is prevented.The blocking voltage is checked most easily if the intertap time delay control istemporarily set below zero. This ensures that after the initial tap delay has elapsedthe raise or lower auxiliary will stay operated when the voltage is outside thedeadband.

Reduce the voltage slightly below VL (as measured in the previous test) and check thatthe Volts Low and Tap lamps both light continuously.

Continue lowering the voltage until the Tap lamp is extinguished. This voltageshould be 80% of VS (tolerance 3%). Reset the intertap time delay to the requiredsetting.

4.2.6 Load shedding

The effective regulated voltage setting can be reduced by selected amounts byshorting the appropriate relay terminals.

4.2.6.1 3%, 6%, 9% of VSLink terminal 22 to 19 and check that the 3% LED illuminates. Measure the new VHand VL and calculate the centre of dead band voltage. This should be 3% lower thanthe actual VS voltage previously measured.

Link terminal 22 to 20 and check that the 6% LED illuminates. Measure the new VHand VL and calculate the centre of dead band voltage. This should be 6% lower thanthe actual VS voltage previously measured.

Link terminal 22 to 21 and check that the 9% LED illuminates. Measure the new VHand VL and calculate the centre of dead band voltage. This should be 9% lower thanthe actual VS voltage previously measured.

Remove the link after test

4.2.6.2 +3%, +1.5%, 1.5% of VSLink terminal 22 to 19 and check that the +3% LED illuminates. Measure the new VHand VL and calculate the centre of dead band voltage. This should be 1.5% lowerthan the actual VS voltage previously measured.

Link terminal 22 to 20 and check that the +1.5% LED illuminates. Measure the newVH and VL and calculate the centre of dead band voltage. This should be 1.5%higher than the actual Vs voltage previously measured.

Link terminal 22 to 21 and check that the 1.5% LED illuminates. Measure the newVH and VL and calculate the centre of dead band voltage. This should be 3% higherthan the actual VS voltage previously measured.

Remove the link after test

24

4.2.7 Time delays

To measure accurately the time delays, it is necessary to be able to carry out a stepchange in voltage and start a timer at the same time. This can be conveniently doneusing a two pole switch, a resistor (say 5K) and an electronic timer, see Figure 5below. Alternatively the time may be checked, approximately, using a stopwatch.

Expected tinitial =

Figure 5

4.2.7.1 Initial time delay

Connect the relay as shown in 4.2.7.

Switch the Inverse/Definite time switch to Definite. With the two pole switch openand the resistor in circuit adjust the voltage until it is inside the deadband, so thatneither the Volts Low or Volts High lamp is illuminated.

Close the switch and check that it:(a) starts the timer,(b) raises the voltage on the relay to above the VH value (measured in test 4.2.3) and(c) energises the Volts High lamp.

Also check that the Lower contacts of the relay operate (Terminals 3 and 5) after theinitial time delay set on the relay.

NOTE: To obtain a consistent timing it is essential to ensure that the timer has resetafter each timing. Removal of the stable voltage supply does thisimmediately.

For 1.212s range, operating time should be 0.5s + setting.

Tolerance 0 +0.8s or 10% whichever is greater.

For 12120s range, operating time is as setting. Tolerance 5%.

Inverse time delay

Switch the Inverse/Definite time switch to Inverse. In this position the initial timedelay depends on how far the voltage deviates beyond the operating threshold(i.e. deadband edges). At the threshold the time should be as marked on the initialtime delay scale. At other voltages the following formula applies:

Initial time delay setting(% Voltage deviation from VS)/V%

The inverse initial time delay may be checked at any reasonable voltage outside thedeadband. The expected time may be calculated using the formula above.The procedure given below is for an example where the voltage increases frominside the deadband to a value higher than the setting voltage.

VR

Adjustablestablevoltagesupply

Timer

Start

15 13 14

17 1

5

18 3

Timerstop

Auxiliaryac supply

Circuit for timing tests

25

With the two pole switch open adjust the voltage until it is inside the deadband, sothat neither the Volts Low nor the Volts High lamp is illuminated.

Close the switch and:

(a) check that it starts the timer

(b) measure the voltage accurately (say VH)

(c) check the operating time (as previous removal of the stable voltage supplybetween checks resets the timer).

Calculate the percentage voltage deviation from VS which is (VH VS) 100/VS.

Calculate the expected tinitial from the formula given earlier.

Calculate the error in operating time.

For 1.212s range, operating time should be 0.5s + setting.

Tolerance 0 +0.8s or 20% whichever is greater.

For 12 120s range, operating time is as setting. Tolerance 20%.

4.2.7.2 Inter tap time delay

When the applied voltage is first taken out of the deadband there will be the initialtime delay and then the raise or lower output auxiliary and the Tap lamp will beenergised for 1 second 0.2 seconds. When the auxiliary drops out there will be atime delay equal to the intertap time delay before the auxiliary relay operates.It will continue in this mode until the voltage is returned into the deadband.

Note: If the intertap time delay potentiometer is set below zero there will be no timedelay. Once the Raise or Lower auxiliary has been energised it will remainoperated until the voltage returns inside the deadband.

To measure the intertap time accurately it is necessary to use a timer which hasDwell time facilities on it and will also start when the auxiliary relay contact opensand stop when the same contact closes. The timer will need to be reset during the1 second during which the auxiliary relay contact is closed.

Tolerance on the intertap time = 10%

The intertap time may be reasonably accurately measured by timing any convenientnumber of cycles with a stopwatch and then calculating the intertap time as follows:

Time measuredNumber of cycles

The initiation of the Tap lamp in each cycle is a very convenient point from which tostart and finish timing.

Intertap tap time = number of cycles

26

= volts

Figure 6

4.2.8.1 Resistive compensation VRWith VR still on the required setting, set VC and VXL = 0.

Apply rated current to terminals 27 and 28.

Apply the reference voltage and adjust the phase angle until the voltage leads thecurrent by 90.

Find the centre of deadband voltage as detailed previously for the regulated voltagesetting VS.

New values of VH and VL will be found and the centre of deadband voltageVH + VL

2

This should be higher than the actual VS voltage measured earlier by the voltage seton the VR control.

Tolerance 0.5 volts or 5% whichever is the greater.

NOTE: If the voltage is lower than the actual VS it is almost certain that there is anunintentional polarity reversal somewhere in the test circuit.

4.2.8 Line drop compensation

For these circuits to operate correctly it is important to observe correct polarities forvoltage and current connections. Figure 6 below gives a typical test connectioncircuit.

V

15 13 1417 27

18 28

Auxiliaryac supply

NCBA

Phaseshifter

I

Phaseanglemeter

ncba

110V120V

220V250V

MVGC

27

4.2.8.2 Reactive compensation VXLUsing the above circuit reset VXL to the required setting and set VC and VR = 0.

Set the Direct/Reverse switch to Direct.

Apply rated current to terminals 27 and 28.

Apply the reference voltage and adjust the phase angle until the voltage is in anti-phase with the current.

Measure the new VH and VL and calculate the centre of deadband voltage. Thisshould be greater than the actual VS voltage measured earlier by the voltage set onthe VXL control. If the relay is to be used with the Direct/Reverse switch in the Reverseposition, check as above but with the voltage and current in phase. The voltage willagain be higher by the voltage set on the VXL control.

Tolerance 0.5 volts or 5% whichever is the greater.

4.2.9 Parallel compensating voltage VCThe relay is connected as for 4.2.8 except that the current source is connected toterminals 25 and 26. Ensure that the correct polarity is used (i.e. terminal 25corresponding to the original connection to 27 and 26 to 28). The pilot connectionterminals (23 and 24) which go to the relay on the other transformer circuit must beopen circuited.

Apply rated current to terminals 25 and 26.

Apply the reference voltage and adjust the phase angle until the voltage is in phasewith the current.

Measure the new VH and VL and calculate the centre of the deadband voltage. Thisshould be greater than the actual VS voltage measured originally, by the voltage seton the VC control.

Tolerance 0.5 volts or 5% whichever is the greater.

Short circuit the pilot terminals 23 and 24 and measure VH and VL and calculate thecentre of the deadband voltage. This should be unchanged from the Actual VSvoltage measured originally. Remove the short circuit and reconnect terminals 23 and24.

4.2.10 Supervision circuits

(i) The undervoltage or overvoltage relays operate and energise the appropriate LEDindication when the input voltage falls below the VU setting or rises above the VOsetting.

Note: On pcb ZJ0049 switch 6 (was LKl) makes VU and VO either independentof the load shedding (Position A or Link 1 between A and B) ordependent on the load shedding (Position B or Link 1 between A and C).

Apply the actual setting voltage VS and check that neither the under or overvoltage LEDs indicate.

Reduce the voltage and check the value at which the

28

Further increase the voltage and check the value at which the >VO lampindicates.

Check that the overvoltage output contact has closed to complete the circuitbetween terminals 7 and 9.

Tolerance for VO and VU 10%.

(ii) The overcurrent blocking relay operates when the total load current exceeds the ILsetting.

Monitor across terminals 3 and 5 to check when the lower volts contact closes.

Apply the actual setting voltage VS and check that there is no circuit across 3 and5.

Increase the voltage until the relay operates and check that the circuit is complete.

Apply current to terminals 27 and 28 and check the current at which the 3/5circuit becomes open circuit. This current should correspond to the IL setting.

Tolerance 10%.

A similar test may be carried out with the voltage low, monitor terminals 1 and 3and recheck the IL current setting.

(iii) The circulating current detector operates when the circulating current betweentransformers connected in parallel exceeds the current set on the IC settingpotentiometers.

Note: The calibration of the IC setting potentiometer is in terms of the CTsecondary current.

Wire a current source to terminals 25 and 26 with terminals 23 and 24 opencircuited.

Apply current and increase until the excessive circulating current lamp (>IC)indicates. This should be at the current set on the IC setting potentiometer.

Tolerance 10%.

At the same time as the IC lamp is energised, the alarm circuit is initiated eitherinstantaneously or after a 3 minute time delay. Switch 8 (was LK3) on pcbZJ0044 gives alarm after 3 minutes when selected to position A (or Link 3between A and B) or gives instantaneous alarm selected to position B (or link 3between A and C). If S10 is fitted, position A gives normal operation as aboveand position B gives no operation of the alarm from excessive circulating currents.

Check that when the circulating current exceeds IC, the alarm lamp operates andthe alarm circuits on terminals 6 & 8 and 10 & 12 are completed either after 3minutes or instantaneously depending on the position of switch 8 (LK3).

Note: On pcb ZJ0044 switch 7 (was LK2) may be selected such that circulatingcurrent gives indication of the IC lamp only, (Position A or Link 2 betweenA and B) or that it gives indication and operates relay RL5 to prevent tapchange initiation. (Position B or Link 2 between A and C).

When in the position to prevent tap change the checks below should be carriedout to check that tapping is prevented. Maintain sufficient current to keep the ICdetector operated. Apply an adjustable voltage supply to terminals 17 and 18and increase this until the voltage is inside the deadband (Volts Low and VoltsHigh lamps will not be lit).

29

Monitor contact outputs 1 & 3 and 3 & 5 and check that there is no circuit.

Reduce the voltage until the Volts Low lamp operates and check that after asuitable time delay the tap lamp indicates but that there is still no circuit on thecontacts.

Repeat with a higher voltage to operate the Volts High lamp. Remove the currentinjected into terminals 25 and 26. Adjust the voltage until it is inside thedeadband and repeat the above procedure but check that output circuits 1 and 3eventually close when the voltage is low, and that circuit 3 and 5 close when thevoltage is high.

(iv) The alarm output relay operates in approximately 3 minutes when the inputvoltage remains continuously outside the deadband limits. If S9 is fitted position Ballows alarm operation, position A does not allow alarm operation. This may besatisfactorily checked using a stopwatch. Apply the actual setting voltage VS andcheck that none of the lamps indicate.

Raise the voltage by approximately 10% and start a stopwatch as soon as theVolts High Lamp indicates.

Stop the stopwatch when the alarm lamp indicates. The time should be between180s and 216s.

Monitor terminals 6 & 8 and 10 & 12 to check that the two contact pairs closewhen the alarm lamp lights.

4.2.11 Load check for MVGC relay

When the line drop compensation facility is used it is essential to carry out a checkwith load down the line to prove that the polarities of the VT and CT as connected tothe relay are correct. The results will be most conclusive if the load current is large.

Calculate the expected R and X voltage drops in the line at the CT rated primarycurrent and convert these to secondary values using the VT ratio.

Set the VR and jVXL controls on the relay to these latter voltages. Set the V%sensitivity setting to 3 and the switch below the jVXL control to direct.

At the receiving end of the feeder measure accurately the phase to phase voltage onthe secondary of the VT. This should be done (at the remote end) on the same pair oflines as those used by the relay at the sending end.

Set the VS setting thumbwheel switches on the relay to the same voltage as thatmeasured at the receiving end of the feeder. The relay should be inoperative underthis condition, as indicated by an absence of the volts high or volts low lamps.If either lamp is illuminated, it is highly probable that either the CT or VT has beenconnected to the relay with the wrong polarity, or that the VR and jVXL relay settingsare not correctly matched to the line.

If the relay is inoperative for V% = 3 then the approximate limits of the deadband orinoperative zone can be established as follows:

Increase and then decrease the VS setting of the relay using the thumbwheel switchesuntil either the volts low or the volts high lamp indicates.

Record the two voltage settings at which the lamps first indicate. If the average ofthese two voltages is within say 2% of that measured at the remote end of the feeder,then the relative polarities of the CT and the VT are correct.

30

It will be appreciated that for this test to be conclusive the actual voltage drop downthe line at the current level available must be well in excess of 2%.

Reset the VS and V% controls to the settings required for the particular application.Note: All controls, whether being used or not, should be set at some point within

their calibrated range and not set to either end-stop.

Section 5 MAINTENANCE

Periodic maintenance is not required. However periodic inspection and test isrecommended as follows:

5.1 Preliminary checks

Loosen the four cover screws and remove the cover, the relay can now be withdrawnfrom its case.

Check all wiring connections to the terminal block and to the pcbs, paying particularattention to polarity of CT connections to the terminal block, terminal number 23 to28 inclusive.

Check that the positions of switches 6, 7 and 8, 9 and 10 are as required; these aredescribed in Section 2.11.

5.2 Functional check using the self test facility

Relay type MVGC has a self test facility which provides a variable measuring voltagesupply allowing a functional check on all of the voltage operated circuits in the relay.

Connect an ac voltmeter capable of measuring 160V rms to the sockets markedvoltage monitor on the front of the relay. With the test switch in normal position thevoltage indicated is the measuring voltage present at relay terminals 17 and 18.Selection of the test position isolates the measuring voltage input and applies avoltage, set by the test volts adjust potentiometer on front of the relay to the relaysmeasuring input. This voltage is variable between 80V and 160V and can be used tocheck regulated voltage setting VS, deadband setting V% as well as undervoltageand overvoltage supervision VU and VO. The test facility may also be used, alongwith a stopwatch, to check the relays timing functions.

Use of the test facility still allows the relay to control the tap change mechanism.It may be desirable, however, before carrying out the checks listed below, to preventtap change initiation by selecting manual/non-auto on the panel control switch.

5.2.1 Regulated voltage setting

Connect ac voltmeter to test volts sockets.Set test switch to test position.Set desired VS on thumbwheel switches.Set V% to 0.5.

Adjust test volts potentiometer until both the volts high and the volts low LEDs are off(i.e. the voltage is inside the deadband). The indicated voltage should beapproximately equal to the set VS.

31

5.2.2 Deadband setting V%Adjustment of the test volts potentiometer about the VS position gives indication ofthe edges of the deadband by illumination of either the volts high or the volts lowLEDs. With V% set at 3% there should be an obvious deadband as the test voltspotentiometer is moved above and below VS setting.

5.2.3 Initial time delay

Set selection switch to definite.

Set the voltage within the deadband by adjusting the test volts potentiometer.

Set initial delay to desired value.

Adjust test volts potentiometer to bring the voltage outside the deadband and startthe stopwatch as the volts high (or volts low) LED comes on; stop timing when thetap LED comes on. The indicated time should be approximately equal to the initialdelay setting.

Note: The initial delay timer is an integrating type and so it resets at a rate equal tothe rate at which it times out. The timer can be reset instantaneously if thevoltage is swung through the deadband from one side to the other andreturned immediately to inside the deadband. Following this procedurebefore a timing check will ensure that the timer is starting from zero time.The initial delay timer resets where the voltage varies about the centre of thedeadband, i.e. the actual VS setting.

5.2.4 Intertap time delay

If the test voltage is left outside the deadband after the initial time delay has elapsedthen a check may be made on the intertap time delay. With the intertap time set for10 seconds there will be a 10 second delay between successive tapping outputs.To measure this time approximately, start the stopwatch when the tap LED goes outand stop the stopwatch when it comes on again. Reduction of the intertap time tobelow 0 seconds will result in a continuous output indicated by a continuouslyilluminated tap LED.

5.2.5 Undervoltage detector VUSet VU to the desired value.

Reduce the test volts until the VU LED just comes on; the indicated voltage should beapproximately equal to the set voltage VU.

5.2.6 Overvoltage detector VOSet VO to the desired value.

Increase the test volts until the VO LED just comes on; the indicated voltage should beapproximately equal to the set voltage VO.

5.2.7 Fixed 80% undervoltage detector

Set the initial delay fully anticlockwise (to give minimum time delay) Set the intertaptime fully anticlockwise (to give continuous output) Set the test volts to between 80%and 100% of set VS, so that the relay times out.

Gradually reduce the test volts until the tap LED goes out; the indicated voltageshould be approximately 80% of the set VS.

32

5.2.8 Alarm timer

To test the timer ensure S9 is in position B.

Reset the alarm timer by bringing the test volts inside the deadband. Adjust the testvolts outside the deadband and start the stopwatch; stop the stopwatch when thealarm LED comes on. The indicated time should be approximately 3 minutes.

Section 6 PROBLEM ANALYSIS

6.1 Servicing instructions

In addition to the maintenance functional checks of the voltage operated circuits,the following instructions provide a complete functional and calibration check forrelay type MVGC 01. Should any of the relays functions found to be faulty it isrecommended that the complete relay is returned to the ALSTOM T&D Protection &Control factory or local service agency.

Should the need arise for the equipment to be returned to ALSTOM T&D Protection &Control Ltd for repair, then the form at the back of this manual should be completedand sent with the equipment together with a copy of any commissioning test results.

The following instructions are essentially laboratory bench tests requiring highaccuracy instrumentation.

6.2 Equipment and input requirements:

Auxiliary supply of rated VX voltage to supply a 30 VA load.

Stable three phase measuring voltage supply to operate between 70V and 170V acinto a 3VA load at rated frequency.

Load current and circulating current inputs require stable current sources from 0 to10A ac, burden 10VA.

Phase shifter to adjust relative phase angle, so that the voltage may lead the currentby phase angles of 0, 90 and 180.

Phase angle meter, typical accuracy 2.

High accuracy TRMS ac voltmeter, ac voltage accuracy less than 0.1% at full range50 or 60 Hz.

Note: The measuring voltage supply will require a fine adjustment controlaccurately to determine the edge of deadband limits.

6.3 Test procedure

Note: The accuracy limits specified in the following tests make no allowance forinstrument error.

6.3.1 Regulated voltage setting VSSet VS to 100 V, V% to 1% and the TEST/NORMAL switch to NORMAL. Apply100V to relay terminals 17 and 18 and slowly increase this voltage until the VOLTSHIGH LED just illuminates. Measure the input voltage using a high accuracyvoltmeter connected to the VOLTAGE MONITOR sockets on the front of the relay andnote the VOLTS HIGH value, VH. Reduce the input voltage until the VOLTS LOW LEDjust comes on; note this voltage, VL.

33

VH + VL2

Tolerance: actual VS = set VS 0.5%

6.3.2 Deadband setting V%Set desired V% value and again measure VOLTS HIGH and VOLTS LOW values.

VH VL2

VH VL2VS

6.3.3 Initial delay

To measure accurately the initial delay it is necessary to connect a variable resistor inseries with the measuring voltage supply to relay terminals 17 and 18 as shown inFigure 7.

or x 100% (for all values of VS)

Figure 7

Potentiometer R should be approximately 5k, 2W.The input voltage VS on terminals 17 and 18 is monitored at the VOLTAGEMONITOR sockets with the TEST switch in NORMAL position.

Set initial time delay multiplier to 10.

a) Definite times

To check times on the lower side of the deadband: set VN equal to thethumbwheel setting, open switch S1 and adjust R to reduce the monitored voltageto the required value below set VS. Close S1 so that VS returns inside thedeadband and allow time for the relay to reset. Opening S1 will now initiate atime delay which can be measured on the timer.

Required timer accuracy: accurate to 0.1 second

Initial delay accuracy: 5% of INITIAL setting

To check volts high times: set VN to required value above set VS. Open S1 andadjust R to bring VS into the deadband. Arrange the timer to start on opening ofS1 and open S1 to measure time delay.

Accuracy: 5% of INITIAL setting

Note: The initial timer can be reset instantaneously by a varying input voltageboth above and below the VS setting or alternatively by removing inputvolts. This operates the 80% undervoltage circuits.

Actual voltage setting VS = volts

V% = % (for VS set at 100V)

1 5 3

17

18

MVGC VS

Timer stopS1

Timer start

RVN

Stablevoltagesupply

34

b) Inverse times

Select the inverse characteristic and set initial delay to 120 seconds.

Check the time delay for voltage deviation of 5 times and 10 times the deadbandsetting away from the VS setting.

Voltage deviation (N) Time delay

5x 24s10x 12s Tolerance 15%

6.3.4 Intertap delay

Set the initial delay to 15 seconds and apply voltage to the relay to cause a volts lowor volts high condition. When the initial delay has elapsed the output relay willcontinue to give pulsed closure for 1 second at intervals determined by the intertapdelay setting.

Arrange for the timer to start when the output contacts open and stop when theyreclose. The measured time is the intertap delay.

Tolerance: 5% of setting

6.3.5 Fixed 80% undervoltage blocking

Set VS = 100V, initial delay = 15s inverse and intertap delay to continuous.i.e. less than zero. With 82V applied the relay should time out and give a continuousoutput and the TAP LED should go out above 79V.

6.3.6 Line drop compensation

For these circuits to work correctly it is important to observe correct polarities forvoltage and current connections. See Figure 8.

Figure 8

Set VS = 100 V

V% = 1a) Resistive compensation scale VR

With rated current applied to relay terminals 27 and 28 adjust the phase shiftsuch that the voltage leads the current by 90.Set : VC = VXL = 0, VR = 24 and VR multiplier = 1.

V

A17

18

25

26

MVGC

Volts CurrentPhase shifter

35

Obtain the new deadband centre voltage by recording the voltages at which thevolts low and volts high LEDs illuminate.

VH + VL2

This should be an increase of 24V 5% on the actual VS value obtained inSection 6.3.1.

b) Reactive compensation scale VXLSet : VC = VR = 0, VXL = 24V direct and VXL multiplier =1.

Apply rated current in antiphase with VS and obtain the deadband centre voltageas before.

Again deadband centre = actual VS + 24V

Tolerance = 5% of 24V

Adjust phase shift to give current and voltage in phase and with VXL = 24VREVERSE, check that deadband centre is within 2% of the value determined forcurrent and voltage in antiphase.

i.e. VS (24V) = VS + 24V.

6.3.7 Parallel compensating voltage, VCThe relay is connected as shown in Figure 9. Ensure that pilot wire connectionterminals 23 and 24 are open circuited.

Apply rated current, to be in phase with the measuring voltage supply, to terminals25 and 26.

Set VC = 24 and obtain the new deadband centre by recording the voltages at whichthe volts high and volts low LEDs just come on.

This should be actual VS + 24V

Tolerance = 5% of 24V

By short circuiting the pilot terminals 23 and 24 the deadband centre should bereturned to the actual VS value independent of the VC setting or applied current.

6.3.8 Load shedding/voltage boost

The effective regulated voltage setting can be altered by selected amounts asindicated by the load shedding LED indications.

Connect terminal 22 to terminals 19, 20 and 21 to give load shedding as follows:

Link Actual VS value is altered by:

19 and 22 3% or +3%

20 and 22 6% or +1.5%

21 and 22 9% or 1.5%

Check the appropriate LED indicator operates. Remove the link after test.

6.3.9 Supervision circuits

(i) Undervoltage and overvoltage relays operate where the input voltage is below orabove VU and VO settings respectively.

Deadband centre = volts

36

Set VS = 115V, V% = 0.5%With VO = 110V and VU = 80V adjust the input voltage to just operate theovervoltage relay, but below the lower deadband limit at approximately 113V.Check that operation of the raise contact, terminals 1 and 3, is blocked byoperation of the overvoltage relay. Set VO = 140V and check that raise output isno longer blocked.

Similarly, with VO = 140V and VU = 120V, set the input volts just above theupper deadband limit at about 117V with the undervoltage relay operated.Check that operation of the lower contact, terminals 3 and 5, is blocked byoperation of the undervoltage relay.

(ii) The overcurrent blocking relay operates where the total load current exceeds theIL setting.

Set IL = 150% IN, IN = rated current

Apply 150% IN current to load current CT input, terminals 27 and 28. Check thatoperation of overcurrent detector blocks both raise and lower output contacts.

(iii) The alarm output relay operates where the input voltage remains continuouslyoutside the set deadband limits. If S9 is fitted then it must be set to position B forthis test.

Connect the relay as in Figure 7, but connect stop terminals of timer to outputcontacts of the alarm relay, terminals 6 and 8 or 10 and 12.

With SWl open adjust R such that the input voltage is within the set deadband.Operation of SWl causes the relay to go to a volts high condition. Check that thealarm LED and output relay operate after a period of approximately 180seconds.

(iv) The circulating current detector operates where the circulating current betweentransformers connected in parallel, exceeds the IC setting. Apply a current sourceto terminals 25 and 26 with terminals 23 and 24 open circuited.

Set IC = 25% INand set internal switches SW7 and SW8 to position A (see Section 2.11).

Apply 25% of rated current and check that LED indication is given for excessivecirculating current.

Set VC = 0

With the excessive circulating current detector operated, check that raise andlower outputs are given. Check with SW7 in position B, that raise and loweroutputs are blocked by operation of a common blocking relay.

Operation of the circulating current detector initiates the alarm output relay.If S10 is fitted then it must be selected to position A for this test.

Adjust the relay input volts to be within the set deadband.

Check that the alarm output relay operates 180 seconds after the operation of thecirculating current detector.

Check with SW8 in position B, that the alarm output relay operatesinstantaneously with the operation of the circulating current detector.

37

6.4 Re-calibration

If necessary relay type MVGC 01 may be re-calibrated using the trimmingpotentiometers indicated in the following table:

Scale Calibration Adjustment of Adjustment ofadjustment highest setting lower setting

VS RV3 RV2

V% RV5 RV6Initial delay RV9 RV8

Intertap delay RV11

80% U/V inhibit RV12

VU RV23 RV24

VO RV20 RV21

IL RV29 RV30

IC RV26 RV27

Alarm Timer RV31

VR RV16 RV34

VXL RV14 RV33

VC RV18 RV32

Each setting can be calibrated to be within the specified tolerance. It is essential thathigh accuracy instrumentation is used throughout calibration.

Adjustment of RV2 can be used to provide a fine adjustment to give interim values ofVS setting.

38

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re 9

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pplic

atio

n di

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m: S

tatic

vol

tage

regu

latin

g re

lay

25 26

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39

VH + VL2VS

Section 7 COMMISSIONING TEST RECORD

TYPE MVGC

STATIC VOLTAGE REGULATING CONTROL RELAY DATE ....................................

STATION CIRCUIT

RELAY MODEL NO. MVGC SERIAL NO.

RATED AC VOLTAGE VN

RATED AC AUXILIARY VOLTAGE VX SET ON RELAY

RATED AC CURRENT IN SET ON RELAY

FREQUENCY Hz

4.2.3 VOLTAGE SETTlNG (VS)

EXPECTED VOLTAGE SETTING (VS) V

VOLTS HlGH THRESHOLD (VH) V

VOLTS LOW THRESHOLD (VL) V

ACTUAL VOLTAGE SETTING V

% ERROR = 100 1 V

4.2.4 PERCENTAGE DEVIATION (V%)

EXPECTED PERCENTAGE DEVIATION (V%) %

ACTUAL PERCENTAGE DEVIATION = 100 %

4.2.5 UNDER VOLTAGE BLOCKING (80% VS)

EXPECTED UNDER VOLTAGE BLOCKING (80% VS) V

ACTUAL UNDERVOLTAGE BLOCKING V

(VH + VL)2

( )VH VL2VS

( )

40

(VH.R + VL.R) (VH + VL)2 2

4.2.6 LOAD SHEDDING VOLTAGES

EXPECTED LOAD SHEDDING VOLTAGES

3% V 6% V 9% V or +3% V +1.5% V 1.5% V

ACTUAL LOAD SHEDDING VOLTAGES

3% V 6% V 9% V or +3% V +1.5% V 1.5% V

4.2.7 INITIAL TlME DELAY

EXPECTED INITIAL TIME DELAY (DEFINITE) Secs

ACTUAL INITIAL TIME DELAY (DEFINITE) Secs

EXPECTED INITIAL TIME DELAY (INVERSE) Secs

ACTUAL INITIAL TIME DELAY (INVERSE) Secs

INTERTAP TIME DELAY

EXPECTED INTERTAP TlME DELAY Secs

ACTUAL INTERTAP TIME DELAY Secs

4.2.8 LINE DROP COMPENSATION VOLTAGE (VR & VXL)

EXPECTED RESISTIVE COMP. VOLTS (VR) V

VOLTS HIGH THRESHOLD (VH.R) V

VOLTS LOW THRESHOLD (VL.R) V

ACTUAL VOLTAGE SETTING V

ACTUAL RESISTIVE COMP VOLTS

V

EXPECTED REACTIVE COMP. VOLTS (VXL) V

VOLTS HIGH THRESHOLD (VH.XL) V

VOLTS LOW THRESHOLD (VL.XL) V

ACTUAL VOLTAGE SETTING V

ACTUAL REACTIVE COMP. VOLTS

V

(VH.R + VL.R)2

(VH.XL + VL.XL)2

(VH.XL + VL.XL) (VH + VL)2 2

41

4.2.9 PARALLEL COMPENSATION VOLTAGE (VC)

EXPECTED PARALLEL COMP. VOLTS (VC) V

VOLTS HIGH THRESHOLD (VH.C) V

VOLTS LOW THRESHOLD (VL.C) V

ACTUAL VOLTAGE SETTlNG V

ACTUAL PARALLEL COMP. VOLTS

V

* VH and VL as in 4.2.3.

4.2.10 SUPERVISION

(i) UNDER VOLTAGE DETECTION (VU)

EXPECTED UNDER VOLTAGE SETTING VU V

ACTUAL UNDER VOLTAGE SETTING V

OVERVOLTAGE DETECTION (VO)

EXPECTED OVER VOLTAGE SETTING VO V

ACTUAL OVER VOLTAGE SETTING V

(ii) OVER CURRENT DETECTION (IL)

EXPECTED OVERCURRENT SETTING (IL) A

ACTUAL OVERCURRENT SETTING A

(iii) CIRCULATING CURRENT DETECTOR (IC)

EXPECTED OVERCURRENT SETTING (IC) A

ACTUAL OVERCURRENT SETTING A

(iv) ALARM: AFTER 3 MINUTES s

(VH.C + VL.C)2

(VH.C + VL.C) (VH* + VL*)2 2

42

4.2.11 LOAD CHECK

VOLTS AT RECEIVING END (VR) V

VOLTS LOW LAMP WHEN VS IS SET AT V

VOLTS HIGH LAMP WHEN VS IS SET AT V

AVERAGE VS (SHOULD BE = VR APPROX.) V

_____________________________________ ______________________________________

Commissioning Engineer Customer Witness

_____________________________________ ______________________________________

Date Date

43

continued overleaf

!

REPAIR FORM

Please complete this form and return it to ALSTOM T&D Protection & Control Ltd with theequipment to be repaired. This form may also be used in the case of application queries.

ALSTOM T&D Protection & Control LtdSt. Leonards WorksStaffordST17 4LX,England

For: After Sales Service Department

Customer Ref: ___________________________ Model No: __________________

Contract Ref: ___________________________ Serial No: __________________

Date: ___________________________

1. What parameters were in use at the time the fault occurred?

AC volts _____________ Main VT/Test set

DC volts _____________ Battery/Power supply

AC current _____________ Main CT/Test set

Frequency _____________

2. Which type of test was being used? ____________________________________________

3. Were all the external components fitted where required? Yes/No(Delete as appropriate.)

4. List the relay settings being used

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

5. What did you expect to happen?

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

44

______________________________________ _______________________________________Signature Title

______________________________________ _______________________________________Name (in capitals) Company name

!

6. What did happen?

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

7. When did the fault occur?

Instant Yes/No Intermittent Yes/No

Time delayed Yes/No (Delete as appropriate).

By how long? ___________

8. What indications if any did the relay show?

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

9. Was there any visual damage?

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

10. Any other remarks which may be useful:

____________________________________________________________________________

____________________________________________________________________________

____________________________________________________________________________

45

AREVA T&D's Automation & Information Systems Business www.areva-td.com T&D Worldwide Contact Centre online 24 hours a day: +44 (0) 1785 25 00 70 http://www.areva-td.com/contactcentre/

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Contents SAFETY SECTION 1 APPLICATION 1.1 Operating Sequences 1.2 Voltage regulating schemes 1.3 Optional external connections 1.3.1 Independent/parallel control 1.3.2 Auto /non-auto 1.4 Line drop compensation for parallel transformers 2.1 Reference voltage setting, VS 2.2 Deadband setting, V % 2.3 Initial delay setting 2.4 Intertap delay 2.5 Line drop compensation settings, VR and VXL 2.6 Parallel compensating voltage, VC 2.7 Load shedding 2.8 Undervoltage and overvoltage supervision, VU and VO 2.9 Overcurrent detector, IL 2.10 Circulating current detector, IC 2.11 Internal setting switches 4.1 Commissioning preliminaries 4.2. Commissioning tests 4.2.1 Equipment and input requirements 4.2.2 General 4.2.3 Regulated voltage setting (VS) 4.2.4 Percentage deviation ( V%) = 1/2 percentage deadband width. 4.2.5 Under voltage blocking (80% VS) 4.2.6 Load shedding 4.2.6.1 3%, 6%, 9% of VS 4.2.6.2 +3%, +1.5%, 1.5% of VS 4.2.7 Time delays 4.2.7.1 Initial time delay 4.2.7.2 Inter tap time delay 4.2.8 Line drop compensation 4.2.8.1 Resistive compensation VR 4.2.8.2 Reactive compensation VXL 4.2.9 Parallel compensating voltage VC 4.2.10 Supervision circuits 4.2.11 Load check for MVGC relay 5.1 Preliminary checks 5.2 Functional check using the self test facility 5.2.1 Regulated voltage setting 5.2.2 Deadband setting V% 5.2.3 Initial time delay 5.2.4 Intertap time delay 5.2.5 Undervoltage detector VU 5.2.6 Overvoltage detector VO 5.2.7 Fixed 80% undervoltage detector 5.2.8 Alarm timer 6 PROBLEM ANALYSIS 6.1 Servicing instructions 6.2 Equipment and input requirements: 6.3 Test procedure 6.3.1 Regulated voltage setting VS 6.3.2 Deadband setting V% 6.3.3 Initial delay 6.3.4 Intertap delay 6.3.5 Fixed 80% undervoltage blocking 6.3.6 Line drop compensation 6.3.7 Parallel compensating voltage, VC 6.3.8 Load shedding/voltage boost 6.3.9 Supervision circuits 6.4 Re-calibration Repair Form

A: