2243 Is-Limiter_EN

8/7/2019 2243 Is-Limiter_EN

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Is-limiter

The world fastest limitingand switching device


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IS-limiter

The worlds fastestswitching device

Reduces substation cost

Solves short-circuit problems in new sub-stations and substation extensions

Optimum solution for interconnection ofswitchboards and substations

In most cases the only technical solution

Reliability and function proofed inthousands of installations since 1960

Worldwide in service

The peak short-circuit current will neverbe reached

The short-circuit current is limited at thevery fi rst current rise


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Current i = i1

+ i2

at the fault location

Single linediagram of a bustie for a systemwithI

k= 31.5 kA

and with anIS-limiter

Short-circuit currents too high?The I

S-limiter, a switching device with extremely short operating time, solves the problem.

A short-circuit downstream from an outgoing feederbreaker is assumed. The oscillogram shown below

indicates the course of the short-circuit currents in thefi rst half wave.A short-circuit current of 31.5 kA can fl ow to the faultlocation through each transformer. This would resultin a total short-circuit current of 63 kA, which is twiceas much as the switchgear capability.

The course of the current through the IS-limiter

in such an event is shown below as current i2.

It can be seen that the IS-limiter is operating sorapidly, that there is no contribution via the trans-former T

2to the total peak short-circuit current

(i1 + i2). Therefore, a switchgear with a rating of31.5 kA is suitable for this application.

31.5 kA 31.5 kA

31.5 kA

k k

k perm.


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Questions and answers regarding the IS-limiter

2. Why the peak short-circuit

current has to be limited?

Because otherwise insuffi ciently dimen-sioned switchboards, switches, currenttransformers, cables, etc. would bedestroyed due to the magnetic forcescaused by the current.

4. How does the IS-limiter work?

The IS-limiter consists of two parallelconductors. The main conductorcarries the high rated normal current(up to 5.000 A).After tripping, the parallel fuse limitsthe short-circuit current during the fi rstcurrent rise (in less than 1 ms).

3. How can switchboards which are only

dimensioned for 2 x IK be operatedwith four transformers infeeds and

a total short-circuit current of 4 x IK

without any risk of overload and with-

out losses?

By installing an IS-limiter between the

busbar sections 1 - 2 and 3 - 4. (This isonly one of the many possibilities forthe use of an I S-limiter (see page 18 forfurther examples).

1. What is the peak short-circuit current?

The peak short-circuit current ipeak

is themaximum instantaneous value of thecurrent after the short-circuit occurs.

pea

k

1 2 3 4

1 x I 2 x I 3 x I 4 x Ikkkk

Transformers: 1 + 2 1 + 2 + 3 1 + 2 + 3 + 41

t

4

3

2

1

Ik

II k k II k k

1 2 3 4

Due to the peak short-circuit

current the electrical system

is subjected to the maximum

mechanical stress created by

magnetic forces.

Due to the AC short-circuit current

duration the system is subjected to

thermal stress.


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5. How is the main conductor

opened in less than a thousandth

of a second?

Switching devices with mechanical me-chanisms and this high rating are not

able to open the main current path insuch a short time. For this reason weuse an electronically triggered chargeas switching mechanism.

1. Current transformer(detects the short-circuit current)

2. Measuring and tripping device(measures the current and providesthe triggering energy)

3. Pulse transformer (converts thetripping pulse to the busbarpotential)

4. Insert holder with insert (carries therated normal current and limits theshort-circuit current)

7. Can IS-limiter inserts be refurbished

after interruption of a short-circuit?

Yes! They can be refurbished at themanufacturers works. The costs are low.The opened main conductor, the parallel

fuse and the charge will be replaced. Allother parts can be re-used.

6. Which overvoltage occurs as aresult of the sudden interruption of

the current?

8. Does the IS-limiter trip on everyshort-circuit?

No! The IS-limiter only trips when the

system is at risk.Small short-circuit currents areinterrupted by the circuit-breakers.

t

1

2

3

4

The main conductor is suddenlyopened, but not the entire current path.With the opening of the main current paththe current commutates to the parallel fuse,which interrupts the current. The overvolt-age occurring at the interruption by thefuse is considerably below the permissiblelevels stated in the IEC / VDE standards,e.g. IEC 60282-1 / VDE 0670 part 4.

Short-circuitcurrent limited bythe fuse element


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12. Which short-circuit current the

IS-limiter can interrupt?

Tests at KEMA to date havedemonstrated 12 kV up to 210 kARMS

17.5 kV up to 210 kARMS

24 kV up to 140 kA

RMS

36/40.5 kV up to 140 kARMS

11. How often does an IS-limiter trip?

Experience shows that an IS-limiter trips

once every four years on average(based on a statistic with approximately3000 IS-limiters in service).

10. What experience is available with theoperation of IS-limiters?

Since the invention of the IS-limiter by

ABB Calor Emag in 1955, severalthousand devices have been successfullyused in DC, AC and particularly in threephase systems.We have over 50 years of good opera-ting experience worldwide. More andmore customers are selecting theI

S-limiter when they need high short-

circuit currents to be safely limitedand electrical systems and distributionnetworks to be economically built orexpanded.

The function and applications of theIS-limiter are explained in the followingpages with various examples. Discussyour short-circuit problems with us. Wealways fi nd a commercially interestingand technically elegant solution with theI

S-limiter.

9. How does the IS-limiter distinguish

between minor and serious short-

circuits?

The measuring and tripping device ofthe I

S-limiter detects the instantaneous

current level and the rate of current rise.The I

S-limiter only trips when both set

response values are reached.

The rate of current rise ( ) is high with high short-circuit currents is low with low short-circuit currents

di

dt


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The function of the IS-limiter

uneconomical for the user. Theuse of I

S-limiters reduces the

short-circuit current in newsystems and expansions toexisting systems, thus savingcost.Circuit-breakers cannot provideany protection against undulyhigh peak short-circuit currents,as they are too slow. Only theI

S-limiter is capable of detecting

and limiting a short-circuitcurrent at the fi rst rise, i.e. inless than 1 ms. The maximum

instantaneous current occurringremains well below the level ofthe peak short-circuit current.

In comparison with complexconventional solutions, the

IS-limiter has both technical andeconomic advantages whenused in transformer or genera-tor feeders, in switchgear sectio-nalizing and connected inparallel with reactors.The IS-limiter is in every regardthe ideal switching device tosolve the short-circuit problemsfor switchgear in power stati-ons, in heavy industry and atutilities.

The rising demand for energyworld-wide requires more

powerful or additional transfor-mers and generators, and anincreasing interconnection ofthe individual supply networks.This can lead to the permissibleshort-circuit currents for theequipment being exceeded andthus parts of the equipmentbeing dynamically or thermallydestroyed.The replacement of existingswitchgear and cable connec-

tions by new equipment withhigher short-circuit strength isoften technically impossible or

IS-limiter connected in parallel with a reactor

fi xed mounted


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9

10

11

4

12

1

2

3

4

5

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Design

The operation of the clampingdevice will be done with two

levers. Only for insert holdersIr 2500 A and 12 kV/17.5 kV

the inserts are fi xed with twobolts.

Pulse transformer

The location of the pulse trans-former depends on the ratedvoltage: for 17.5 kV, in the lower

insulator 6 only, for 24/36 kV, in the upper

and lower insulators.The pulse transformer transmitsthe tripping pulse from thetripping device (Figure 3) tothe charge 10 in the I

S-limiter

insert, and at the same time

IS-limiters for three-phase sy-

stems basically consist of:

three IS-limiter insert holders, three I

S-limiter inserts,

three tripping current trans-formers,

a measuring and trippingdevice.

IS-limiter insert holders

The IS-limiter insert holder

comprises: base plate 1, insulator 2, insulator with pulse trans-

former 6 and telescopiccontact 5,

pole heads with clampingdevice 3 for the receptionof the I

S-limiter insert.

Figure 2: IS-limiter insert

4 Fuse7 Fuse indicator8 Insulating tube9 Bursting bridge10 Charge11 Main conductor indicator12 Fuse element

Figure 1: IS-limiter insert holder

with insert for 12 kV, 2000 A

1 Base plate2 Insulator3 Pole head with clamping device4 Fuse5 Telescopic contact6 Insulator with pulse

transformer

ensures electrical isolation ofthe tripping device from the

charge which is on busbarpotential.

IS-limiter insert

The IS-limiter insert is the swit-

ching element. In a sturdyinsulating tube 8, the insertcontains the main conductor,designed as a bursting bridge 9,which encloses a charge 10. Ontripping, this charge is triggeredand the main conductor opensat the rupture point.


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The IS-limiter consists in prin-

ciple of an extremely fast

switch, able to carry a highrated current but having a lowswitching capacity, and a highrupturing capacity (HRC) fusearranged in parallel. In order toachieve the desired short open-ing time, a small charge is usedas the energy store for openingof the switch (main conductor).When the main conductor isopened, the current continuesto fl ow through the parallel

fuse, where it is limited within0.5 ms and then fi nally inter-rupted at the next voltage zeropassage.The current fl owing throughthe IS-limiter is monitored by anelectronic measuring andtripping device. At the veryfi rst rise of a short-circuit

Function of the IS-limiter

current, this device decideswhether tripping of the

IS-limiter is necessary. In orderto reach this decision, theinstantaneous current and rateof current rise at the I

S-limiter

are constantly measured andevaluated. When the setpointsare simultaneously reached orex-ceeded, the IS-limiter trips.The three phases are operatedindependently of one another.The loss-free conduction of ahigh operating current on the

one hand and the limitation ofthe short-circuit current at thefi rst current rise on the otherhand are made possible bydistributing these two functionsof the IS-limiter between twoconductors. In comparison withreactors, the I

S-limiter avoids

voltage drops and does not

contribute to the peak short-circuit current.

Power unit

A DC voltage of 150 V gener-ated in the power unit is used asthe charging voltage for thetripping capacitors and at thesame time as the supply voltagefor the electronics. As far asnecessary, the supply voltage isdivided and stabilized withinthe individual assemblies. Awatchdog module in the powerunit constantly monitors themost important functions of thethree tripping units.

Figure 4: Schematic diagram of the IS-limiter

equipment

G1 Power unitA2 Tripping unitsA3 Anti-interference unitA4 Indication unitF116 Miniature circuit-breaker

for supply voltageQ6 I

S-limiter

(insert holder and insert)T1 I

S-limiter tripping transformer


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Tripping unit

The current supplied by the

tripping transformers for thecorresponding phases is moni-tored in the tripping units. Thethree tripping units work inde-pendently of each other.Both the rate of current rise andthe instantaneous current valueare used as criteria for tripping.

Figure 5: Schematic diagram of a measuringand tripping unit

T1 IS-limiter tripping

transformerT2 Intermediate

transformer of thetripping unit

T3 Pulse transformerL1 Measuring inductanceR1 .. R6 Setting resistorsC1 Tripping capacitor

RS Discharge resistorRZ

Charge

Both variables are convertedinto proportional voltages and

supplied via logical gates to anelectronic measuring element.The latter provides an outputsignal when the rate of currentrise and the instantaneouscurrent value have both simul-taneously reached the responsevalue of the measuring element.

The output signal from themeasuring element then activa-

tes a thyristor, which dischargesa capacitor via the pulse trans-former in the I

S-limiter insert

holder to the charge. At thesame time, this discharge exci-tes the corresponding fl agindicator relay IS-limiter trip-ped in the indication unit.


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Testing the IS-limiter

As with every other protectivedevice, I

S-limiters should also be

checked at regular intervals.There are special testing setsavailable for those tests whichcan be performed by the opera-tor or by ABB AG. These testsets consist of a test equipmentand a test insert or a test plugand a test insert.

The test plug is used to checkthe voltages and the functions

of the tripping system.The user friendly test equip-ment facilitates further testssuch as determination of theresponse voltages of the measu-ring elements, and testing andsetting of the modules of themeasuring circuits.

During testing, the IS-limiter

insert is replaced by the test

insert. The test insert containsa neon lamp as an indicator,which lights up when a trip-ping pulse is received.

Figure 6: IS-limiter insert holder with test insert Figure 7: Test plug

Figure 8: Test equipment

H

D

W

Width (W) : 400 mm

Height (H) : 215 mm

Depth (D) : 320 mm

Weight : 11 kg


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Rated voltage V 690 12000 12000

Rated current A 1250/2000/3000/40001)/50001) 1250/2000 2500/3000/40001)

Rated power-frequency

withstand voltage kV 3 28 28

Rated lightning impulse

withstand voltage kV - 75 75

Interrupting

current kARMS

up to 140 up to 210 up to 210

IS-limiter

insert holder kg 10.5 23/27.5 65

IS-limiterinsert kg 17.0 12/12.5 15.5

IS-limiter Width W mm 148 180 180

insert holder Height H mm 554 637/651 951

with insert Depth D mm 384 503/510 509

1) With cooling fan

Frequency: 50/60 Hz

For higher rated currents, insert holders with inserts are connected in parallel.

The range

Technical data

A. IS-limiter as loose equipment

supply

In this case the insert holders,the inserts and the trippingcurrent transformers areinstalled in an already exis-ting panel. The equipmentsupply generally comprises: three insert holders, three inserts, three tripping current

transformers, one measuring and trip-

ping device (Figure 3).

H

W

D


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17500 17500 24000 36000/40500

1250/2000 2500/3000/40001) 1250/1600/2000/30001) 1250/2000/25001)

38 38 50 75

95 95 125 200

up to 210 up to 210 up to 140 up to 140

23/27.5 65 27/31.5/33 60

14/14.5 17.5 19/19.5/24 42

180 180 180 240

637/651 951 740/754/837 1016

503/510 509 553/560/560 695


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B. Truck mounted IS-limiter in a switchgear panel

The IS-limiters can also be installed in a metal-clad

switchgear panel. The withdrawable truck with thethree IS-limiter insert holders and inserts has the

function of a disconnector. The three trippingcurrent transformers are fi xed mounted in the panel

and the measuring and tripping device is mountedin the low voltage compartment.

Truck mounted IS-limiter in a switchgear panel


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IS-limiter panels with truck

C. Fixed mounted IS-limiter in a switchgear panel

The IS-limiters for low voltage, 12 kV, 17.5 kV and24 kV are also available as fi xed mounted equip-ment in a metal-enclosed switchgear panel.The three IS-limiter insert holders with the I S-limiterinserts and the three tripping current transformersare fi xed mounted in the panel.The measuring and tripping device is mounted inthe low voltage compartment.

The IS-limiter (fi xed mounted) for 36 kV/40.5 kV

is available in a metal-enclosed switchgear panel.Same as for loose equipment supply, the measuringand tripping device is installed in a separate sheetsteel cabinet (Figure 3).

For all fi xed mounted I S-limiters the electrical dataare the same as for loose equipment supply.Dimensions and weights on request.

1) With cooling fan.

For higher currents, insert holders with inserts are connected in parallel.

Rated Rated Rated Rated Dimensions Weight

voltage current power-frequency lightning impulse including

withstand voltage withstand voltage IS-limiter truck

kV A kV kV Height Width Depth kg

mm mm mm

12 1250 28 75 2200 1000 1300 approx. 1200

2000

2500

3000 1)

3000 1350

4000 1) 1350

17.5 1250 38 95 2200 1000 1300 approx. 1200

2000

3000 1)

3000 1350

4000 1) 1350

24 1250 50 125 2325 1000 1500 approx. 1300

1600

2000

2500 1)


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IS-limiters in system

interconnections

IS-limiters are frequently used ininterconnections betweensystems or in bus sectionswhich would not be adequatelyshort-circuit proof when con-nected by a circuit-breaker.Each partial system should haveat least one incoming feeder, sothat power supply to eachpartial system can be maintai-ned on tripping of the I

S-limiter

(Figure 9).

There is a large number ofadvantages for the operationunder normal conditionsof bus sections connected byI

S-limiters:

Reduction of the seriesnetwork impedance. Thevoltage drops caused by loadsurges (e.g. of starting ofmotors) can be signifi cantlyreduced.

Applications

Improvement of the currentdistribution at the feeder

transformers. The load dependent losses of

the feeder transformers arereduced.

Increased reliability of thepower supply. On failure ofone feeder transformer, theload is taken over by theother feeder transformerswithout current interruption.The cost for an otherwiserequired new switchboard

with higher short-circuitcapacity will be saved.If a short-circuit occurs within asystem or in an outgoing feeder,the IS-limiter trips at the fi rst riseof the short-circuit current anddivides the busbar system intotwo sections before the instanta-neous current reaches an inad-missible high level. After trip-ping of the I

S-limiter, the

short-circuit is only fed by thetransformer in the part of the

system affected by the short-circuit. The short-circuit currentis now selectively interruptedby the circuit-breaker.A remarkable advantage of theuse of an IS-limiter is that thevoltage in the part of the systemnot affected by the short-circuitonly drops for a fraction of amillisecond so that even sensiti-ve loads (e.g. computers)remain protected from drops in

the system voltage.For this reason the IS-limiter can

also excellently be used as areliable switchgear suitablebetween an unprotected anda protected switchboard orsection of a switchboard.

Figure 9: IS-limiter in a bus section


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IS-limiters used as a link

between public networks and

consumer owned power supplysystems

The decentralization of powersupply leads to systems withtheir own power generatingfacilities being interconnectedwith public supply networks.The additional short-circuitcurrent from generators leads tothe permissible short-circuitcurrent in the utility networkbeing exceeded. The most

appropriate technical solution and mostly the only one isthe installation of anI

S-limiter in the interconnection

with the public utility network(Figure 10).If necessary, the I

S-limiter can be

provided with a directionaltripping criterion. This requires

three additional current trans-formers in the neutral connec-

tions of the generators. The IS-limiter then only trips onshort-circuits in the publicsupply network if a generator isin operation.

IS-limiter in parallel with a

reactor

The IS-limiter can also be con-

nected in parallel with a reactor(Figure 11). If a short-circuitoccurs behind the reactor, theIS-limiter trips and the currentcommutates at the fi rst currentrise to the parallel reactor,which then limits the short-circuit current to the permissi-ble level.For normal operation, the I

S-

limiter bridges the reactor coil.

This avoids: Current dependent copper

losses and the associatedoperating costs of the reactor.

Current dependent voltagedrop at the reactor, whichfrequently causes majordiffi culties on start-up of bigmotors.

Control problems with thegenerator.

Figure 10: IS-limiter in connecting point with

a public supply networkFigure 11: I

S-limiter in parallel with a reactor in

a generator feeder

10 kV3 ~ 50 Hz I" = 25 kA

I" = 15 kA

I" = 16 kAk perm

kT

k perm

I" = 3 kAkG

I S

~


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Use of more than one IS-limiter

with selectivity

In order to achieve selectivity ina switchboard or switchboardswith more than one I

S-limiter

installed, additional trippingcriteria as current summation ordifferences or comparison ofcurrent directions are required.If in case of two IS-limitersinstalled in a switchboardselective tripping is required, ameasurement of the total cur-

rent becomes necessary.The IS-limiter trips as follows:

Short-circuit in section A:Only I

S-limiter no. 1 trips.

Short-circuit in section B:IS-limiter no. 1 and no. 2 trip.

Short-circuit in section C:Only IS-limiter no. 2 trips.

For measurement of the totalcurrent, transformer feeders

must be additionally equippedwith one CT set each. The total

current Isum1 is equal to thecurrent (I

T1) of transformer T1

plus the current (IIs-1

) fl owingthrough the I

S-limiter 1.

The total current Isum2 is equal tothe current of transformer T2plus the currents fl owingthrough IS-limiter 1 and 2.The total current I

sum3is equal to

the current of transformer T3plus the current fl owing throughI

S-limiter 2.

The tripping criteria of theIS-limiters correspond to a logic

and function. The IS-limiter 1trips in case of short-circuits insection A, if the current ofIS-limiter 1 and the total currentIsum1

reach or exceed theirresponse values simulaneously.The same is applicable forsection C. In case of a short-

circuit in section B IS-limiters

1 and 2 trip.

The summation of the currentscorresponds to the principle ofthe adding up of currents in abusbar protection system. Theonly difference is the non-requirement of current transfor-mers in the outgoing feeders,i.e. the requirement of materialis negligable. With this principleup to 5 transformers have sofar been connected in parallel,using 4 I

S-limiters only. The

principle ensures that alwaysonly the IS-limiter or these

IS-limiters trip, which are closestto the point of short-circuit.

Figure 12: Schematic diagram-IS-limiter

with summation of currents


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Please send by mail or fax +49/2102/121922 to:

Sender:

Questionnaire on the use of IS-limiters in medium and

low voltage three-phase systems

We require the following data for a quotation and design of an IS-limiter

Rated capacity of capacitor banks and theinductance in series connected to thesame voltage level the I

S-limiter is installed.

Rated power of the biggest transformer,energised from the same voltage levelwhere the I

S

-limiter is located. Single Line Diagram.

5. Which parts of the system should beprotected?Please note that more than one I

S-limiter can

be installed in one system and we can realiseselectivity between I

S-limiters.

. Requirements for the installation:

It must be possible to insulate the IS-limiter tothat the IS-limiter insert can be replaced after

tripping. There must be a circuit breaker in series with

the IS-limiter (except the I

S-limiter is in parallel

to a reactor).

1. Operating Voltage:

. Rated Current:

3. Frequency:

. In order to calculate the tripping and settingvalues we need: Single line diagram of the installation with the

following data: Initial symmerical short-circuit current I

K of

generators, transformers, the grid, motorcontribution and the permissible short-circuit current of the switchboard.

Rated power of motors over MWconnected to the same voltage level theIS-limiter is installed.

ABB AG

Calor Emag Medium Voltage Products

Postfach 1010

D-07 Ratingen


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7. WeareabletodelivertheIS-limiterindierent

designs.Whichdesigndoyouneed?

IS-limiterasloosedeliveredcomponentsor

installationinacubicleoyourowndesign

IS-limiterinacubicletypeZS1,truck

mounted(upto24kV)

IS-limiterinacubicletypeZS1,fxed

mounted(upto24kV)

IS-limiterinacubicletypeZS,fxed

mounted(25to40.5kV)

8. TheIS-limitertrippingdeviceneedsthree

auxiliaryvoltagesupplies: a)twoindependent ACsupplies(50or60Hz,

powerconsumptionmax.40VA). Mainsupplyshouldbetakenromthe

systemtobeprotectedviavoltagetransormer.

Stand-bysupplye.g.romlightinggrid(independentromfrst!).

b)onesupplyvoltage(ACorDC)orannunciationpurposes(powerconsumptionmax.20VA).

WhichACvoltagesareavailable?

asmainsupply:

VHz

asstand-bysupply:

VHz

Whichvoltageorannunciationisavailable?

V DC; AC;

9. Remarks:


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Remarks (continuation):


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Contact us

Note:

We reserve the right to make technical changes or

modify the contents of this document without prior

notice. With regard to purchase orders, the agreed

particulars shall prevail. ABB AG does not accept

any responsibility whatsoever for potential errors or

possible lack of information in this document.

We reserve all rights in this document and in the

subject matter and illustrations contained therein.

Any reproduction, disclosure to third parties or

utilization of its contents in whole or in parts is

forbidden without prior written consent of ABB AG.

Copyright 2009 ABB

Al rights reserved

DEABB224308E(08.09-1000-AMC)

ABB AG

Calor Emag Medium Voltage Products

Oberhausener Strasse 33 Petzower Strasse 8

40472 Ratingen 14542 Werder (Havel) OT Glindow

GERMANY GERMANY

Phone: +49 2102 12-0

Fax: +49 2102 12-1777

E-Mail: [email protected]

Internet: http://www.abb.com/mediumvoltage

Documents

2243 Is-Limiter_EN