DIFB: an important reference for EHV applications

A short-circuit between thebusbars of an electrical powerdistribution or transmissionnetwork station may haveserious consequences not onlydue to the damage suffered bythe equipment, but alsobecause of the loss of supply tothe customer. Different meansare available to the user to limitthe risks created by these faults,for example, setting upindependent sections so that ifa fault occurs on one of them,the loads can be transferredonto the remaining unaffectedsections. However, thesemeasures are only reallyeffective if suitable busbarprotection is available.

• DIF.B busbar differentialprotection operates on theMerz Price principle usingpercentage characteristics.There are two versions of the

Features Common to

equipment called DIFB & DIFBCL.

DIFB

The DIFB protection device wasinitially developed for EHVapplications (≥ 400 kV). It hassegregated phases and isparticularly suitable for gasisolated substations (GIS) withsingle-phase compartments (ND1.6952).

DIFB or DIFB CL

DIFB or DIFB CL

DIFB

DIFB-CL

245 kV

overhead

three-phase GIS

single-phase GIS

the DIFB and DIFB CL

DIFB CL

Confronted with qualityrequirements and the necessityof providing a continuousservice as far as the distributionof high and medium voltages(HV, MV) is concerned, networkusers have been obliged tochoose a fault-eliminating timethat only busbar differentialprotection devices are capableof meeting. The DIFB CL wasdeveloped from the DIFB toprovide a more compact andeconomical device. This isachieved by using a linearcombination of the 3 phasecurrents on each input auxiliarytransformer. Otherwise, itincorporates the maincharacteristics of the DIFB inparticular those concerning itssafety of operation with highlysaturated current transformers(CTs) (ND 1.6913).

Both the DIFB and DIFB CL usepercentage measuring circuitswhich operate with highlysaturated CTs, thus combining ahigh speed busbar faultdetection function (less than 0.5ms) and perfect stability whenexternal faults occur. Althoughthe DIFB and DIFB CL use astabilization principle based ondifferential resistance combined

with a percentagecharacteristic, they only requirelow pulse energy to operatewith internal faults. Thesefactors directly influence thesize and cost of the currenttransformers. In particular, thetripping speed (7 ms with self-reset relays) is not affected bythe DC component of aperiodicconditions due to saturated CTs.

The DIFB CL is derived from theDIFB and uses the same sub-assemblies, in particular thewell-proven measuring board(more than a thousand sub-assemblies were operating withapproximately 350 busbarprotection devices in 1995).

Reliability

DIFB-CL: the high performance of DIFB adapted toHV/MV substations

Operating principleThe DIFB is a percentagemedium impedance protectiondevice with low impedancehigh-speed switching (T/4)when internal faults aredetected.By using the term impedance,this operating principle can bedistinguished from thoserequiring signal processing, butcannot be interpreted in termsof consumption because of thedetection performancecharacteristics with pulseoperating conditions (seebelow, CT specifications).

id

Operating zone

Non operating zone

Percentage detection board 20 51 208.This electronic circuit is fitted in DIFBs andDIFB CLs and is unequalled as far asstability with external faults and acquisitionspeed with internal faults (0.5 ms or 1 ms)is concerned.

The operating principle of theDIFB allows the complexity ofthe design to be kept to aminimum. This ensures a highlevel of reliability.

High Immunity toDisturbancesThe DIFB and DIFB CLprotection devices use currentflow and so their input circuitsare naturally protected againstexternal disturbances becausethe signal to be processed isimposed by the currentgenerators. In addition, thedownstream electronic circuitrymeets the most stringentenvironmental standards(damped oscillations, high-speed transients, electrostaticdischarges, etc.).

Flexibility and ExtensibilityThe DIFB and DIFB CL protectiondevices are installed in unitcubicles (DIFB) or frames (DIFBCL) for one or two zones withan open architecture such thatthe equipment may be extendedin the future even when this hasnot been specified at thebeginning of the project (forexample, changing a 2-zonestructure into a 4-zone structureon-site).

ErgonomicsThe DIFB and DIFB CLprotection devices areequipped with the followingmain aids for commissioningand operation:

- ENERTEST test socket forsecondary injections;

- on/off switch per zone;- mini block diagram of stationwith permanent display ofstatus of routing isolators;

- forcing sensor for the status of theisolator position recopy relays;

- flag indicators of tripping perzone;

- tripping indicators for breaker-failure events.

Periodic Self-Test (Optional)

This function is performedautomatically so that the userdoes not have to carry outdelicate operations formanually checking whether theequipment is able to trip on areal busbar fault. These self-testoperations may be fairlyinfrequent because the sub-assemblies tested are veryreliable. However, forprocedural reasons the self-testreport should figure daily in thelog of the Status Recorder.

DIFB isolator module

Internal Fault 8In with aperiodic component

CT presaturated by remanence effect

External fault 20In with aperiodic component

Low performance CT’s requirement

Permanent Monitoring of theMeasuring CircuitsThe DIFB measuring circuits arefitted with several differentialcurrent detectors. Thedifference in the setting valuesare used to make logic statuscomparisons and to processany inconsistency between thedifferent detection levels as afailure.

Multiple CriteriaThe fact that multiple criteriaare used is a directconsequence of the previousfunction which requires severalthreshold elements to beconsistent in order for atripping operation to beauthorized.This vertical safety system isreinforced by differentmeasures which require severalparallel channels to supplyidentical data and that anorder is only validated at theoutput of an element if thiselement has received thecorresponding data at its input

Self-test automat board

(see check zones monitoring).

Can be Used on ExistingCurrent Reducers with Non-Homogenous CharacteristicsLow performance CTs(≥ 10 VA 5P10) with noremanence specifications, andcan be connected in series withother existing protectiondevices and different primaryratings.

Through-Fault Stability withHighly Saturated CTsThis stability which isindependent of the amplitude of

the short-circuit current as wellas of the CT saturation level isobtained by combining thecirculating current principle andthe percentage characteristicwhich compares - ininstantaneous values - thedifferential value and anrestraining value that is theimage of the current flowingthrough the protected zone.

Internal Fault Operation withSaturated CTs

If a fault occurs on the busbars,the short-circuit currents mayproduce very high saturation

UR+

50,3

500

Bus-Bar

520 VA 5P20

5005

20 VA PS

UR -

Ud

Rd 8 ms

Copy of DIFB CL test recordings on 63 kV networkat the EDF laboratory, St-Denis

Self Remote Remote manual

Remote manual

Alarm zone 1A unit

Alarm zone 2A unit

Ultra-rapid even during aperiodic conditions

levels on the CTs. These levelsmight be extremely high whenall the fault current flowsthrough one CT only, whichoften occurs at the CTs of thebus coupler section bars and inparticular, if fault current build-up aperiodic conditions arecombined with a remanentmagnetic flux effect. The DIFBis equipped with ultra-fastdetection devices that canoperate in 0.5 ms, i.e. alwaysbefore the saturation point isreached.

DIFB CL section module

High Speed Operation

The duration of the voltagedrop depends on thischaracteristic. It is an extremelyimportant stability factor intransmission networks andguarantees the consumer a highquality of service withdistribution networks. The DIFBdifferential protection deviceprovides a tripping order in atime of between 7 and 15 msdepending on whether theoutput relays have self orelectrical reset. This typicaloperating time alsocorresponds to the maximum

Cut-off device

zone 1A

Cut-off device

zone 2A

No polarity +/- P

No polarity +/- D

initialization command

Inconsistent threshold detection

Converter failure

Fault detection

with self-test

reset command

command zone 1A unit

command zone 2A unit

48 Vdc

48 V

141315 765431221 8 9 10

6c6c4c2c22c 24c26c

26c 18c 20c22c 24c 10c 10c10c 12c 12c 12c14c 14c 16c 16c 16c18c 18c14c28c

3736 1716 1918 2120 2726 2524 2322 3534 3332 3130

KP F18

+ DP1

Bus

SBF (*)

(*) tripping signal bus via 50BF or 87B protection device

(LR)(LR)

(L) K18

KD F18

DIFB CABINET

RACK A CONNECTOR X16

28c 2c 4c

In serv.

Out of

serv.En

serv.Hors serv.

+ DP1

Local control Local control

- DP1

+ DP1

- DP1

out of service - manual command - anomaly circuits 1 - protection device failure - insufficient relaying power supply (+/- DP1)

out-of-service - manual command - anomaly circuits 2 - protection device failure - insufficient relaying powe supply (+/- DP1)

XAA

XAA

Regular self-test

in progress

Protection device

not faulty

Protection device faulty

Tripping zone 1A

Current circuit anomaly zone 1A

Alarm zone 1A unit out-of-service

Alarm zone 2A unit, out-of-service

Tripping, zone 2A

Current circuit anomaly zone 2A

Remote Controls and Remote Signals wired for a DIFB CL 2-Zone Frame

A B

SECTION PANEL

WIRING ON A FEEDER BAY

FRONT PANEL OF THE DIFB CL

FEEDER SECTION MODULE

FEEDER BOARD

To o

ther

pr

otec

tion

C

A

A

B

A

B

B

D

- D

D

SA1 - ouv

SA1

Z1

+ T+ D

- T- D

50BF

Tripping

Z2

SA2

SA1 - non ouv

SA2 - ouv

27

1

2

26

25

24

23

22

21

201918

171615

20z

20d

18z

18d

16z

4d2d

2z4z

14d

SA2 - non ouvC

S2

S1

P2

P1

S2

S1

P'2

P'1

P''2

P''1

S2

S1S2

S1P1 P1 P1

P2 P2 P2

N

Yellow led Z1 trip. by 50 or 87BF

Led rouge SA1 closed

Yellow led Z1 trip. by 50 or 87BF

Red Led SA2 closed

Signals that the expert needs

required for processing thefollowing section data:- Current- Position of the isolators andlocal signals

- Reception from BF relay (e.g.non-integrated circuit breakerfailure protection devices,50 BF)

- Tripping orderFor the DIFB, these last twoinformation items are processedin separate modules.

DIFB CL cubicle prepared for a 4-zone substation

time which is not affected bythe aperiodic component of thefault current.

Section ModularityThe DIFB and DIFB CLprotection devices can containseveral modules, depending onthe size of the station to beprotected. A bay module canbe associated with a feeder, abus coupler or a bus section.For the DIFB CL, a modulecontains all the elements

Remote Controls and RemoteSignalsThe main remote controls andremote signals are available onterminals that are free ofpolarities. They allow certainremote operations to be carriedout (on/off controls, automatictest) and are used to receive allthe data that the operatorneeds, for example:- tripped zone,- busbar fault or circuit breakerfailure,

- phase indication for DIFB.- wiring fault,- power supply failure,- self-test results,- system status.

Total Zone Monitoring forDIFB CLOne of the most frequentreasons for busbar differentialprotection relay maloperationis the existence of an errorwhen the real position ofisolator is transmitted orreceived. A differential currentis then produced in some of themeasuring elements.However, if only the incomingand outgoing currents of theentire station are taken intoaccount, their vector sum isalways zero if no faults occur,whatever the recopy errors onthe partial sections. Thereforethe tripping authorization givenby one zone unit is conditionedby the operation of a checkzone unit that is only sensitiveto total values. This function isnot necessary on the DIFBbecause the thresholds can be

TZ1 Z2 21

icc

21

icc

Only one CT core required per bay

87 Z1 87 Z2

F3 F4 Fi Fi F26 F27

87 S

& &

TrippingBusbar 1 Busbar 2

set to higher values than theoperating current of the mostloaded feeders.

Integrated Circuit-BreakerFailure Protection 87BF (forDIFB CL only)

On some subtransmissionnetworks, the DIFB CL can beequipped with a circuit breakerfailure protection deviceassociated with each auxiliaryCT block and which operates byforcing the differential unitwhen an external fault has notbeen cleared in a pre-set timeafter a tripping order has beenreceived. The DIFB however, isdesigned for use preferablywith transmission networks andso this type of integrated optionis not provided because thetripping orders are generallyprocessed by single-phase polesrequiring 50BF relays withseparate poles thatcommunicate by simple loop

with the DIFB.

Oversensitization Independentto Zero Sequence Current

The DIFB CLs were designed foruse with HV or MV distributionapplications and so the fact istaken into account that in thistype of networks the earth fault

Id = 0ie = icc is = -icc

t<tBFP

Figure 1: detailing line circuit breaker control

IA

IB

(A)

(B)

(R)

IC

IR

m

P2P'1

P1

P'2

P''1

P''2

n

m

S1

S2

100

Diagrams in three-phase conditionsFig. 1: Combination RatioFig 2: Resultant in balanced three-phase

conditions (independent of n)

Id = 2iccie = icc is = icc

t>tBFP

Figure 2: framing circuit breaker tripping

current is generally limited by theneutral connection impedances.DIFB CL summation transformersconsist in two phase windings (Aand B) and a zero sequencewinding (R). This design allowsan independent adjustment to beobtained between the multi-phase isolated fault conditionsand the earth fault conditions.

n

FAULT

AN BN CN AB BC CA ABC

Examples with TCA Type LB

4.5 3.5

4 (nominal earth) 1 (nominal phases)

0.5 0.5

0.866

(n - 0.5) IB

n.IC

0.866 I IA

0.5 IC

0

Fig. 1 Fig. 2

30°

The assurance of technical support provided byGEC ALSTHOM teams

Protection Device BalanceThe DIFB and DIFB CLprotection devices arebalanced by choosing theappropriate auxiliarytransformer ratio (ACT) withrespect to the ratio of the mainCTs (MCT).The main adjustment concernsthe number of primary turns ina range corresponding to thetype of application.The adequate adjustmentvalues are indicated byGEC ALSTHOM in the files thatare specific to the sub-stationconcerned.However, there are severaldifferent types of applicationwhich also take into accountthe value of the differentialresistance, Rd, which affectsthe stability if saturation occurswith external faults:DIFB MZ: Multi-ratio ACTs withphase segregation In/0.1 to1 A - Rd ≤ 250 ΩDIFB LB: Multi-ratio ACTs withphase segregation In/0.3 to1.2 A - Rd ≤ 250 ΩDIFB LZ: Multi-ratio ACTs withphase segregation In/0.1 to0.3 A - Rd = 4.7 ΩDIFB CL: ACTs with linearphase combination In/0.3 to1.2 A (AB fault basis)Rd ≥ 50 ΩThe final ratio is chosen on thebasis of the highest MCT ratioto which the lowest ACT ratiocorresponds, if possible.

Application Notes

Theoretical dimensions of theMCTs

The dimensions of the MCTs aredetermined by the knee-pointvoltage value so that when aninternal fault occurs, the MCTthat has the highest load interms of the value of thesupplied current and in terms ofsecondary ohmic load be notsaturated in less than 1 ms. Inpractice, the load representedby the ACT windings is notconsidered to be large enoughto influence the dimensions ofthe CT.

Abbreviations

Vk: saturation knee-pointvoltage

In: MCT secondary ratedcurrent (1A or 5A)

IN: MCT primary ratedcurrent

ICC: maximum short-circuitcurrent delivered tothe busbar via theinput where the MCTis installed

RTCP: resistance ofsecondary winding ofthe MCT concerned

RF: resistance of link loopbetween MCT andACT

DIFB

1000/5 A 500/5 A 200/5 A

5/1 A 5/0.5 A 5/0.2 A

Example with phase segregation DIFB MZ

MCT ACT Finalratio

1000/5 A 5/1 A500/5 A 5/0.5 A 1000/1 A200/5 A 5/0.2 A

Ω

ACT

5/1 A

S2

MCT 1000/5 A

40 In

RMCT

ts

Rd 250 Ω

1.5 Ω0.5 Ω

ts 0.5 Ω

Rd250

n: ratio of ACTconcerned

Rd/n2: value of differentialresistance transposedto the ACT primary

K: dimensioningcoefficient

where K = (1.2/40).(ICC/IN)

Examples and practical considerations

In the example given below, thehighest load transposedconcerns the 1000/5A MCTThe following is assumed:ICC = 40 kA, RTCP = 0.5 Ωand RF = 1.5 Ω

Vk = K. In. (RTCP + RF + Rd/n2)

Therefore:

Rd/n2 = 250/25 = 10 ΩK = (1.2/40) x 40 = 1.2Vk = 1.2 x 5 (0.5 + 1.5 +10)

= 72 V

This theoretical valuecorresponds to the minimumstandards given in themanufacturers’ catalogues, i.e.10 to 20 VA 5P20, whichcovers most applications.

The CT performancecharacteristics can beexpressed in terms of saturationknee-point voltage values andin terms of secondaryresistance values:

In = 5 A: Vk > 70 V - RTCP < 0.5 Ω,

In = 1 A: Vk > 350 V - RTCP < 10 Ω

(1) RF includes the primary resistance

P

5/0.2

TCA

RF1.5Ω

S1

S2

RTCP 0.5 Ω

200/5 A MCT

saturated

Conditions ensuring Stabilitywith External Faults and MCTSaturation

These conditions are defined bythe following implicit formula:Rd > (1 - P/2P) RBP > RB/(2 Rd + RB)P is the adjustable slope between0.4 and 0.8RB is the highest loop resistancetransposed to the secondaries ofthe ACTsRB = n2 (RTCP + RF) (1)

This value is highest where theMCT ratios are the lowest (n high).The ACT secondary internalresistances are not taken intoaccount in this calculation,because they are not significant.

For example :

In the previous calculation thesuite in question will beequipped with MCTs with aratio of 200/5 A (n = 5/0.2 A= 25)

RBmax = 625 (0.5 + 1.5) =1250 Ω

Rd is assumed to be set to 250 Ω

P > 1250/(2 x 250 + 1250) =0.71

P will be set to 0.8

A range of equipment which integrates our experience

Preparing a Busbar Protection Project

The design characteristics of astation influence the selectionand the cost of the protectionsystem to be installed.Generally it is recommendedthat the system analysis iscoordinated as early as possiblewith the equipmentspecifications. If not, aforgotten element that seems tobe insignificant may increasethe cost of the protection systemsignificantly. There are fewimportant parameters and noneof them should be neglected:

• Station General Diagram- number of independent sections- number of feeders, buscouplers, bus section elementsof busbars

- isolator locations- circuit breaker locations- CT’s locations- planned extensions andsuccessive steps if theextensions are performed invarious stages

• OperationThe DIFB protection device isdesigned to operate in alloperational configurations.However, the possibility ofisolator closing operation mustbe considered at the beginningof an operation and therefore,two busbar sections will beassumed to be contained in theDIFB protection device. Thus, ifa fault occurs on one of the twobusbar sections at the beginningof an operation, it will be

processed as if the isolator wasalready closed (simultaneoustripping of the two busbarsections).

• Short-circuit Conditions- external fault maximum current- internal fault minimum current

• Equipment- CT rated ratio:Highest primary rated current(INCT max)Lowest rated current (INTCmin)if possible, theINCTmax/INCTmin ratio mustbe less than or equal to 4

- Saturation knee-point voltage - Resistors of secondary windings- Section and lengths of the linkconductors between the mainCTs (MCTs) and the auxiliaryCTs (ACTs). If the exact datais not available, the links forthe lowest ratio MCTs must beestimated (see technical datasheet)

- Isolator auxiliary contacts andtiming (see technical datasheet)

- Protection type for circuit-breaker failure.

Main ArchitecturesThe busbar differentialprotection devices aredesigned to be adapted to verydifferent types of stationarchitecture. The nonexhaustive list below gives themost frequent examples.

Architectural elements

The architectural elements ofthe protection devices aregenerally designated by theletters A and B, like the mainparts of a complex substation.An architectural element maybe a cubicle, for DIFBs, or aframe, for DIFB CLs. The sub-assemblies are normallydelivered cubicle-mounted andwired by GEC ALSTHOM:however, for specific examplesof DIFB CLs, the frame andwiring kits may be deliveredseparately and should beassembled by the localassembler.In the following tables:F indicates the number of

connectable feeder baysBC indicates the bus coupler baysT indicates the bus-section

circuit-breakersS indicates the bus-section

isolatorsThe capacity of the equipmentitems can be expressed in thenumber of inputs, bearing thefollowing in mind:Each F bay needs 1 inputEach BC or T bay needs 2inputs (see following page)

Cubicle StandardsIn principle, cubicle-mountedequipment is provided inaccordance with certainspecific contracts, however, forstandardization purposes,GEC ALSTHOM offers thefollowing standards:Single cubicle:

800 x 800 x 2100Double cubicle:1600 x 800 x 2100

Main Models

• DIFB cubicles = 15 inputsDIFB 1100: protection for 1zone with standard capacity of15 feedersDIFB 2210: protection for 2zones, 1 bus coupler andfollowing finishing options:- capacity for 9 feeders,- capacity for 13 feeders,- capacity for 11 feeders +possibility of extension to 4zones with 2 bus sections

DIFB in a double cubicle equipped for theprotection of a EHV station with 3 busbars.

DIFB 2200:DIFB 2210extensioncubicle for 2-zone stationswith more than13 feedersDIFB 2240:DIFB 2210extensioncubicle for 4-zone stations.The DIFB 2210and 2240cubicleassembly isdesignatedDIFB 4450.

DIFB 3330:protection for3 zones, 1 buscoupler, 13feeders andpossibility ofextension to 6

zones.

DIFB 3360: DIFB 3330extension cubicle for 6 zonestations. The DIFB 3330 and3360 cubicle assembly isdesignated DIFB 6690.

• DIFB CL frame = 15 or 20inputs in standard version= 29 inputs in extended version

DIFB CL 1101: frame for 1 zonewith standard capacity of 15 or18 feeders, 27 feeders withextension frame.

DIFB CL 2201: frame for 2zones, 1 bus coupler andfollowing finishing options:- capacity for 13 feeders,- capacity for 18 feeders,- capacity for 16 feeders +

possibility of extensionreserved for 4 zones, - capacity for 27 feeders withextension frame.

DIFB CL 2204 : DIFB CL 2201extension frame for 4-zonestations. The DIFB 2201 and2204 frame assembly isdesignated DIFB CL 4405.

Accessories to be Specifiedwhen Ordering

• ENERTEST kit:contains an ENERTEST PE 3000type test handle, 4 single-poleDFM 110 connectors and leadswith safety connectors.

• Maintenance KitsP0 type = main kit for DIFB 1100C0 type = additional kit forDIFB 1100P1 type = main kit for DIFB2210 and 4450C1 type = main kit for DIFB2210 and 4450BCL type option (a) for DIFB CL2201BCL type option (b) for DIFB CL4405

• Single-Phase PowerGenerator BAMP 3002 typeGenerator for checking thepercentage characteristic andfor testing the wiring andcurrent transformers. The BAMP3002 supplies:- either a 0 to 1000 A currentwith an internal impedance of1000 Ω on the basis of a 1 Arating,

- or a 0 to 1000 V voltage.It also includes a floating inputtimer to take measurements ofbetween 0 and 99, with aresolution of 1 ms.

Systems that can be extended in the future

1. 1-zone substation

F1

F3 F4 F5 F27

Z1

F2

DIFB CL

Single or extended

frame

1101

18F or

27F

DIFB Single cubicle

1100

15F

2. 2-zone substation with 1 BSCB (2)

DIFB CL

Single or extended

frame

2201

1T 16F or

25F

DIFB Single cubicle

2210

1T 13F

F1

F3 F4 Fi Fj F24 F25

Z1

F2

Z2T

(1) BSI : Bus Section Isolator (2) BSCB : B

Main Configurations

3. 2-zone substation with 1 BSI (1)

F1

F3 F4 Fi Fj F26 F27

Z1

F2

Z2

DIFB CL

Single or extended

frame

2201

1S 18F or

27F

DIFB Single cubicle

2210

1S

13F

S

4. 2-zone substation with central incoming and double routing by isolators

DIFB CL

Single or extended

frame

2201

18F or

27F

DIFB Single cubicle

2210

13F

F1

F2 F3 Fi Fj F26 F27

Z1 Z2

us Section Circuit Breaker

F1 F3

F4F2

Fi

Fj

Z1

Z2

5. 2-zone substation with 1+1/2 circuit breaker per feeder

DIFB CL Single frame

2201

18F

DIFB Single cubicle

2210

12F

or 2 DIFB 1100

6. 2-zone substation, 1 bus coupler, 1 circuit breaker per feeder Busbar routing by isolators

DIFB CL

Single or extended

frame

2201

1BC

25F

can be extended to 4 zones in the future (see 7 and 8)

BCFuture

bus coupler

Future bus

sectionF1 F2 F25

DIFB Single cubicle

2210

1BC 13F

or11F(1)

(1) can be extended to 4 zones in the future (see 7 and 8)

7. 4-zone substation with 2 BS-CB 2 bus couplers 1 circuit-breaker per feeder

DIFB CL 4405 Frame

DIFB CL 2201

1BCA

2T 16FA

DIFB CL 2204

1BCB

2T 16FB

F1A to F16A

F1B to F16B

8. 4-zone substation with 2 BSI 2 bus couplers 1 circuit breaker per feeder

BCA A coupling

BCB B coupling

S1Z1A Z1B

Z2A Z2BS2

=

DIFB 4450 Single cubicles

DIFB 2210

1BCA

2T 11FA

DIFB 2240

1BCB

2T 11FB

=

A B

+

+

S1Z1A

F1A to F16A

F1B to F16B

Z1B

Z2A Z2BS2

BCA A coupling

BCB B coupling

DIFB CL 4405 Frame

DIFB CL 2201

1BCA

16FA

DIFB CL 2204

1BCB

2S 16FB

=

DIFB 4450 Single cubicles

DIFB 2210

1BCA

13FA

DIFB 2240

1BCB

2S 11FB

=

A B

+

+

(1)

(1)

(1) inter-cubicle links

8-1. Architectural variants, 4 zones can be used with the standard configurations of a DIFB CL, type 4405 or DIFB 4450

8-2.

S1Z1A

F1A to F15A

F1B to F15B

Z1B

Z2A Z2BS2

BCA LB BCB

In this architecture the S1 and S2 isolators are operated by a bus link (LB) which is used to create a shunt for the operating isolator by a circuit breaker. The link is considered to be a combination of one bus coupler circuit breaker and two feeders.

S1AZ1A

F1A to F15A

F1B to F15B

S1B

Z2A

Z1B

Z2BS2BS2A

The specific feature of this architecture is that the bus coupler is central and can be assigned to the following: A busbars, or B busbars, or A and B busbars simultaneously. The DIFB switching system must be organized in such a way that the coupling section currents can be routed either separately via the A or B frame, or simultaneously (see fig. 8).

9. 3-zone substation = 1 coupling, 1 circuit breaker per feeder

Double cubicle

DIFB 3330

10. substation with 6 isolated zones, 2 couplings, 1 circuit breaker per feeder

DIFB 6690

Double cubicles 1BCA

Z1

Z2

Z3

F1 to F11

A B

1BC 11F

BC

Z1A S1

S2

S3

Z2A

Z3A

F1A to F11A

BCA

=

11FA 1BCB3S

11FB

+DIFB 3330

DIFB 3360

m

Technical dataCURRENT CIRCUITS

- Primary nominal current of the auxiliary CTs: In

- Overload current: continuous : for 1 second

- Secondary nominal current (or referencecurrent of the DIFB internal circuits): Is

- Adjustment of the auxiliary CT ratio

- Standard adjustment fineness- Optional adjustment fineness- Consumption per input with In in non-differential conditions or 1/4 period after abar fault has been detected

- Differential resistance Rd

- Specifications concerning the main CTs:. category. power

. winding max R/min VK

MEASUREMENTS

- Percentage adjustment- Minimum detection threshold by the percentagecharacteristic

- Minimum fault current check threshold forwhich DIFB is authorized to operate

- Wiring fault superposition threshold

- Accuracy of operating thresholds- Detector return percentage

DETECTION MODE

- Measuring time- Influence of harmonics- Influence of frequency variations- Adjustment of wiring fault alarm time delay- Number of measuring circuits

ALARMS

- No power supply- Signals indicating:

. phase A fault

. phase B fault

. phase C fault

. tripping per zone- Circuitry fault signal- Self-test in progress signal- Protection device faulty signal- Protection device not faulty signal- Protection device out-of-service signal

(1) Nominal ratio based upon a two-phase sDepartment depending on earth fault minimu

Standard LowMB Consumption LB

1 A or 5 A 1 A or 5 A

2 In 2 In40 In 40 In

0.3 A 0.3 AIn/0.3 to In/0.3 toIn/1.2 A (1) In/1.2 A (1)

0.1-0.15 0.3-0.63 VA 1 VA

to 15 VA to 5 VA

≥ 50 Ω ≥ 50 Ω

x or equivalent> 10 VA 5P20

In = 1 A: 10 Ω/350 VIn = 5 A: 0.5 Ω/70 V

DIFB DIFB CL

P = 0.4 - 0.5 - 0.6 - 0.7 - 0.8

Ids = 0.125 In

Id>> = 0.25 In to 2.5 Inadjustment fineness 0.25 In

Id> = 0.05 In - 0.125 - 0.25 - 0.4 - 0.5

± 10%95%

instantaneous values

0.5 msnonenone0.087s to 87sindependent circuits per phase

a loop of NC contacts

1 NO contact1 NO contact with common point1 NO contact1 loop of NO contacts1 loop of NO contacts1 loop of NO contacts1 loop of NO contacts1 loop of NO contacts1 loop of NC contacts

instantaneous values

1 msnonenone0.087s to 87s

Standard Low Lowconsumption impedance

1 A or 5 A 1 A or 5 A 1 A

2 In 2 In 4 In40 In 40 In 80 In

1 A 1 A 0.3 AMulti-ratio Dual-ratio Dual-ratioIn/0.05 to 1 A In/0.1 to 1 A 1/0.02 to 0.3 A

0.05A Particular specifications ± 1% to ± 6% depending on ratios of main CTs

8 VA 1.5 VA 0.2 VA

113 Ω 113 Ω 4.7 Ω167 Ω 167 Ω200 Ω250 Ω

x or equivalent Specific> 10 VA 5P20 applications

In = 1 A: 10 Ω/350 VIn = 5 A: 0.5 Ω/70 V

P = 0.4 - 0.5 - 0.6 - 0.7 - 0.8

Ids = 0.125 In

Id>> = 0.25 In to 2.5 Inadjustment fineness 0.25 In

Id> = 0.05 In - 0.125 - 0.25 - 0.4 - 0.5

± 10%95%

a loop of NC contacts

1 loop of NO contacts1 loop of NO contacts1 loop of NO contacts1 loop of NO contacts1 loop of NO contacts1 loop of NC contacts

upply AB. One-phase ratios are offered by GEC ALSTHOM’s Applications current.

LOCAL OPTICAL SIGNALSPer busbar section and phase:- percentage threshold LED indicator- check threshold Id>> LED indicator- Circuitry fault Id> LED indicator- tripping flag indicator

- protection device failure LED Indicator- auxiliary source insufficient flag indicator

TRIPPINGTripping relay options self reset or Electrical resetContacts per feeder 2 NO contacts 3 NO contacts with

common pointClosing capacity 250 W with 10 A

maximumof 250 V or 5 A

Continuous current 5 A 10 AOverloads 10 A - 4 s 40 A - 1 s

30 A - 0.5 s 250 A - 30 msBreaking capacity (L/R = 20 ms) 0.2 A - 250 VCC 2 A - 250 VCC

OPERATING TIME < 8 ms < 15 msConsumption on tripping 3 W per feederRe-setting local or remote

RECEPTION OF CIRCUIT BREAKER FAILURE INFORMATION (OPTIONAL)One reception relay per feederNominal supply voltage 48 VCC - 110 VCC - 125 VCC - 220 VCC

or 250 VCCConsumption 2.5 WTime of tripping by circuit breaker 18 ms with self-reset relaysfailure information 25 ms with electrical reset relays

AUXILIARY POWER SUPPLYUn nominal voltage 48 VCC - 110 VCC - 125 VCC - 220 VCC

or 250 VCCVariation range Un -20% +20%Power consumption - in standby state 5 W per bar section- during switching of a feeder +25 W- on tripping +3 W per feederVoltage drop 100% - 30 ms insensitive

ENVIRONMENTStandards DICOT EDF, CEI, ANSIElectric Strength 2 kV - 50 Hz - 1 mnShock wave 1.2/50 µs - 5 kV - 0.5 J CEI 255-5Susceptibility to HF disturbances- dampened oscillations 2.5 kV - 1 MHz (category IV)- high-speed transients 4 kV - 5 kHz (category IV)- radiated waves 10 V/m (category III)- electrostatic discharges 15 kV (category IV)- energy shock wave 8/20 µs - 4 kV (category IV)- radio frequency supervision 015/80 MHz - 10 V mod 1 kHz 80%

(category III)Temperatures- nominal operating range - 10°C, +55°C- storage - 40°C, +70°C

PRESENTATION - CONNECTIONSDepending on the size of single bay 800 x 800 x 2100 the installation to be protected or double bay 1600 x 800 x 2100Access to the connection terminal blocks- standard via the front, rotate the frame holding the

racks- on request via the rear,Connections of the current circuits on stud terminals for lugs of diameter 4 mmConnections of the cue circuits on tunnel terminals for cross-sections of 4 mm2

Weight of a single bay fitted for protecting a 2-zone busbar9 feeders and 1 coupling approx. 400 kg(33 auxiliary transformers included)

DIFB

LED indicatorLED indicatorLED indicatorflag indicator

LED indicatorflag indicator

self-reset with possibility of electric locking2 NO contacts

250 W withmaximumof 250 V or 5 A5 A10 A - 4 s30 A - 0.5 s0.2 A - 250 VCC

< 10 ms (typically 7 ms) (1)

2.5 W per feederlocal or remote

48 VCC - 110 VCC - 125 VCC220 VCC - 250 VCC2.5 W20 ms

48 VCC - 110 VCC - 125 VCC -220 VCC or 250 VCCUn -20% +20%

5 W per bar section2 W+2 W per feederinsensitive

DICOT EDF, CEI, ANSI2 kV - 50 Hz - 1 mn1.2/50 µs - 5 kV - 0.5 J CEI 255-5

2.5 kV - 1 MHz (category IV) 1000-4-14 kV - 5 kHz (category IV) 1000-4-410 V/m (category III) 1000-4-315 kV (category IV) 1000-4-28/20 µs - 4 kV (category IV)015/80 MHz - 10 V mod 1 kHz 80% (category III)

- 10°C, +55°C- 40°C, +70°C

- standard 14-U frame for 2 zones- 18 feeders 490 x 625 x 410weight : 20 kg

- can be extended up to 27 feeders withadditional 4-U frame

- can be extended up to 27 feeders withadditional 4-U frame

DIFB CL

(1) The natural time can be increased by20 ms in the event of switching for thedetection of a fault involving a high neutralearth impedance.