Is.13580.Internal Fuses &Internal Overpressure Disconnectors for Power Electronic Capacitors

8/12/2019 Is.13580.Internal Fuses &Internal Overpressure Disconnectors for Power Electronic Capacitors

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IS 1358 : 1992

INTERN L FUSES ND INTERN L

OVERPRESSURE DISCONNECTORS FOR

POWER ELECTRONIC C P CITORS

UDC 621.316.923.621.319 4

@ BI S 1992

BUREAU OF INDIAN STANDARDSMANAK BHAVAN 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

December 1992 Price droop 3

( Reaffirmed 2004 )


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Power Capacitors Sectional Committee, ET 29

FOREWORD

This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalizedby the Power Capacitors Sectional Committee had been approved by the ElectrotechnicalDivision Council.

The object of this standard is to formulate uniform requirements regarding performance, testingand to provide a guidance for co-ordination of fuse and disconnector protection.

Assistance has been derived from IEC Document 33 ( Sectt ) 99 Internal fuses and internaloverpressure disconnectors for power electronic capacitors issued by the International Electro-technical Commission ( IEC ).

For the purpose of deciding whether a particular requirement of this standard is complied with,the final value, observed or calculated, expressing the result of a test or analysis, shall berounded OR in accordance with IS 2 : 1960 Rules for rounding off numerical values ( revised .The number of significant places retained in the rounded off value should be the same as thatof the specified value in this standard.


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Is 13580 : I992

I ndi an St andard

INTERN L FUSES ND INTERN L

OVERPRESSURE DISCONNECTORS FORPOWER ELECTRONIC C P CITORS

1 SCOPE AND FIELD OF APPLICATION

1 1 This standard applies to internal over-pressure disconnectors and fuses when usedto protect power electronic capacitorsmanufactured according to IS 13648 : 1992Power electronics capacitors.

1.2 This standard also applies to internal over-pressure disconnectors used to protect self-healing metalized dielectric capacitors forpower electronics.

1.3 This standard does not apply to fuses anddisconnectors for which the service conditions,in general, are incompatible with the require-ments of the standard unless otherwise agreedbetween manufacturer and purchaser.

1 4 Fuses and disconnectors conforming tothis standard are designed to isolate faultedcapacitors elements or capacitor unit, to allow

,operation of the remaining parts of thatcapacitor unit and the bank in which thecapacitor unit is connected. Such fuses and

disconnectors are not a substitute for a switch-ing device such as a circuit-breaker or theexternal protection of the capacitor bank, orpart thereof.

2 REFERENCE

IS 13648 : 1992 Power Electronic capacitors isa necessary adjunct to this standard.

3 TERMINOLOGY

3.1 Definitions of capacitor parts andaccessories shall be in accordance with

I IS 13648 : 1992.

/ NOTE - The word relement in this standard isused in accordance with the definition containedin capacitor specifications, and not in accordancewith the fuse standards.

3.2 Internal Fuse

A device incorporated in capacitor whichdisconnects an element or a group of elementsin the event of breakdown.

3.3 Internal Overpressure Disconnector

A disconnecting device inside a capacitor,designed to interrupt the current path in thecase of abnormal increase of the internalpressure.

NOTES

1 This disconnector can also be placed outside thecapacitor unit, but is still considered an integralpart of the capacitor unit, and shall fulfill the samerequirements and pass the same tests as the inter-nal overpressure disconnector.

2 This device is normally used in capacitors of theself-healing type.

4 GENERAL

4.1 The fuse is connected in series with theelement(s) which the fuse is intended to isolateif the ,element(s) becomes faulty. The rangeof currents and voltages for the fuse is there-fore dependent on the capacitor design, andin some cases also on the bank in which thefuse is connected.

The operation of an internal fuse is in generaldetermined by one or both of the factors givenin (a) and (b):

a) the discharge energy from elements orunits connected in parallel with thefaulty element or unit; and

b) the line fault current.

4.2 The disconnector is intended to interrupt

the current to all elements of the capacitoror some of them. The proper operation of thedisconnector is dependent on the leak-tightnessof the container during the life of thecapacitor.

5 DISCONNECTING REQUIREMENTi

5 1 The fuse shall enable the faulty element tobe disconnected when electrical breakdown ofelements occurs in a voltage range, in whichI+ is the lowest and us the highest value of thevoltage between the terminals of the unit atthe instant of fault.

1


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4

IS 13580 1992

The reeommended values for u, and us are thefollowing:

6.4 The fuse connected to the undamagedelement(s) must be able to carry the dischargecurrents due to the breakdown of element(s).

6.5 The fuses and disconnectors must withstandthe discharge test, see 10.

u, = 0.8 UNu, = see Table 1

5.2 The disconnector shall enable the faultycapacitor unit to be disconnected for voltageup to and including u,. 7 MARKING

The recommended value is:a43= 1-3 UN

NOTE - The purchaser shall specify if this voltagewill be exceeded. 8 ROUTINE TESTS

6 WITHSTAND REQUIREMENTS

The marking regarding presence of internalfuse shall be provided on the capacitor asindicated in IS 13648 : 1992.

The unit(s) shall have passed all routine testsspecified in IS 13643 : 1992.

6.1 After operation, the fuse assembly and thedisconnector must withstand rated element

voltage and rated voltage between the terminals9 TYPE TESTS

of the disconnected capacitor respectively,plus any unbalance voltage due to fuse ordisconnector action, and any short timetransient overvoltage normally experiencedduring the life of the capacitor.

9.1 The type tests comprise following:

a) Discharge test ( see IO );

b) Disconnecting test on fuses (see 11 ; and

6.2 Throughout the life of the capacitor, thedisconnector shall be capable of carrying conti-nuously a current equal to or greater than 1-ltimes the maximum permissible units current( see 14 of IS 13648 : 1992 ) and the fusescapable of carrying continuously a currentequal to or greater than maximum permissible

unit current divided by number of parallel fusepaths.

c) Disconnecting test on disconnector( see 12 ).

In a.ddition, the fuses and disconnectors shall beable to withstand all type test of the capacitorunits in accrodance with IS 13748 : 1992.

6.3 The fuse and the disconnector shall becapable of withstanding the surge current (is).

9.2 Type tests are considered valid if they are

performed on capacitors of a design identicalwith that of the capacitor offered, or on acapacitor of a design that does not differ fromit in any way that might affect the propertiesto be checked by the type tests.

Table 1 Test Voltage Between Terminals

Causes5.1 10.1 and 11.4)

I ac Capacitors dc CapacitorsI

non self-healing self-healing I non self-healing I self-healing

acTest voltage 2 u NJ \ i 15 UN/V 2 - - -

dcTest voltage 2 ur? 2 u x J di UN 15 N

NOTE-The Y, and u, values above are based on the voltage that may normally occur across thecapacitor unit terminals at the instant of electrical breakdown of the element.The purchaser shall specify if the u, and U, values differ from the stated ones.

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IS 13580 : 1992

10 DISCHARGE TEST

10 1 The units shall be charged by means ofdc and then discharged through a gap situated asclose as possible to the capacitor. They shallbe subjected to five such discharges within 10minutes.

The test voltage shall be equal to 1.1 UN.

If b.owever a maximum peak current isspecified, the discharge current shall be adjustedby variation of the charging voltage and theimpedance of the discharge circuit to a valueof:

I ttst = l-4 &

Within five minutes after this test, the unitshall be subjected to a voltage test betweenterminals ( see Table 1 ).

The capacitance shall be measured before thedischarge test and after the voltage test. Themeasurements shall not differ by an amountcorresponding either to breakdown of anelement or to blowing of an internal fuse.

11 DISCONNECTING TEST ON FUSES

11 1 Test Procedure

The disconnecting test on fuses is performed-first at the upper dc test voltage U, given inTable 1 and multiplied by 1.1 and then, assoon as possible after the blowing of one fuse,at the lower dc test voltage of O&9 U Untilthe blowing of another fuse.

The fuse action must be such that the voltagedrop across the tested unit is equal to or lessthan 10 percent.

If the voltage drop is more than 10 percentadditional capacitors can be put in parallel toincrease the parallel stored energy.

The tests on fuses are performed either on onecomplete capacitor unit or on two units, ifthere is only one fuse inside.

11 1 1 One of the following test procedures a),b) or an alternative method shall be used. Ifno agreement has been reached, the choice isleft to the manufacturer.

NOTES1 At the upper voltage limit, one additional fuse (orone tenth of the fused elements directly in parallel)connected to a sound element(s aliowed to bedamaged.2 The test voltage shall be maintained for 10seconds after a breakdown to ensure the fuse hasdisconnected correctly unaided by disconnection ofthe power supply.

3 In special cases, ir may be necessary to extendthe tests unti two or more breakd0wr.a of capacitorelements have occurred. The number of break-downs at each voltage limit shall in such caseS besubject to agreement between manufacturer andpurchaser. If the number of breakdowns is exceeded,the voltages stated in 11.4 may have to be ir,creased.

4 Precautions shall be taked when performing thistest against the posible explosion of a capacitorunit.

5 The voltage shall be gradually increased to thespecified value.

a) Capacitor preheating - The capacitor unit ispreheated in a chamber before applying thetest voltage at the upper limit. Preheatingtemperature ( 100C to 150C) is chosen by themanufacturer to achieve a practical short time( some minutes fo some hours ) to the firstbreakdown.A lower preheatirg temperature should be usedwhen applying the test voltage limit : to avoidbreakdowns before reaching the test voltage.Capacitor current is to be recorded during the test.

NOTE -TO prevent excessive internal liquidpressure due to high temperature the unit may beequipped with a relief tnbe including a valvewhich must be closed at the instant of applyingthe test voltage.

b) Electrical breakdown o the element - Someelements in the test unit are each provided withfor example a tab, inserted between the dielectriclayers. Each tab is connected to a separateterminal.To obtain breakdown of an element thus equiped,a surge voltage of sufficient amplitude is appliedbetween the tab and oile of the foils of themodified element.Capacitor current is to be recorded during the

test.11 2 Capacitance Measurement

After the test, capacitance shall be measuredto prove that the fuse(s) has ( have ) blown.

A measuring method shall be used that issufficiently sensitive to detect the capacitancechange caused by one blown fuse.

11.3 Visual Checking

After the disconnecting test, no significantdeformation of the contamer shall be apparent.

11.4 Voltage TestA voltage test shall be carried out by applying1.1 times the voltage mentioned in Table 1 fora period of 10 s.

12 DISCONNECTING TEST ONDISCONNECTOR

12 1 Test Sequence

The test shall be carried out On a capacitorunit.

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IS 13580: 992

Unless agreed otherwise, a capacitor which haspassed the endurance test ( under considerationmay be used.

The capacitor shall be mounted in a circulat-

ing air oven having a temperature equal to themaximum ambient air temperature of thetemperature category of the capacitor.

When all the parts of the capacitor havereached the temperature of the oven thefollowing test sequence shall be performed withthe circuit given in Fig. 1.

a

b

c

d

With the selector switches H a n d K inposition 1 and a respectively the Nvoltage source is set to 1.3 UN and thecapacitor current is recorded. The Nsource is ac for testing ac capacitorsand dc for dc capacitor.

The T source is set to lOi& the switchH is then set to position 2 and thevariable resistor is adjusted to give a dcshort circuit current of 300 mA.

Switch H is set to position 3 and switchK to position b to apply the dc test voltageto the capacitor which is maintaineduntil the voltmeter indicates approxi-mately zero for 3 to 5 seconds.

Switch K is then set to position a againto apply the test voltage :o the capacitorfor a period of 3 min when the currentis again recorded.

4

The following conditions maybe obtained:

i

ii)

iii)

When

The ammeter Z and the voltmeter U bothindicate zero. In this case the fuseshall be checked. If it has blown, itshall be replaced. Then the voltage isapplied to the capacitor and if the fuseblows again the procedure is interrupted.If the fuse does not blow, the procedureconsisting in the application to thecapacitor voltage as prescribed in itemsc) and d) above is continued using onlythe switch K,

The current indicated by the ammeter Zislower than 66 percant of the initial valueand the voltmeter U indicates 1.3 U NThe current shall indicate that at leastone disconnector in the capacitor hasinterrupted. In this case the procedure is

interrupted;The current indicated by the ammeterZ is higher than 66 percent of the initialvalue. In this case the procedure iscontinued as per items (c) and (d).the procedure is interrupted, the

capacitor is cooled to the ambient temperatureand the voltage test between terminals andcontainer is carried out according to 10 1 fIS 13648 : 1992.The minimum short-circuit current of the Ngenerator at the capacitor terminals is 2 000 Aor as agreed between manufacturer and user.

The rated current Zc of the fuse shall be notless than 21,.

SE L E TOR_ SWIT H

\C P CITOR uNlTUNDER TEST

FIG. 1 CIRCUIT TO PERFORM HE DISCONNECTING EST

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12.2 Test Requirements

At the conclusion of the test, the enclosure ofeach capacitor shall be intact except thatnormal operation of a vent, or minor damageof a case ( for example cracks ) is permittedprovided the following are met:

a

b

cl

4

Escaping liquid material may wet theouter surface of the capacitor but shallnot fall in drops;

The container of the capacitor may bedeformed and damaged but not broken;

Flames and/or fiery particles shall notbe emitted from the openings. This maybe checked by enclosing the capacitorin gauze ( cheese cloth ). Burning orscorching of the gauze is then considered

to be a criterion of failure;A voltage test shall be carried out inaccordance with 10.1 of IS 13648 : 1992

NOTE - Excessive emanation of fumes during thetest couId be dangerous

13 GUIDE FOR FUSE AND DISCONNECTORPROTECTION

The fuse is connected in series with the element

\1

IS 13580 : 1992

that the fuse is designed to isolate; if theelement becomes faulty. After the breakdownof an element the fuse connected to it willblow and isolate it from the remaining partof the capacitor, which allows the unit tocontinue in service. The blowing of one ormore fuses will cause voltage changes withinthe bank, when series connections is used.

The voltage across sound unit(s) must notexceed the value given in the relevant standard.

Depending on the internal connection of theunits, the blowing of one or more fuses mayalso cause a change of voltage within the unit.The remaining elements in a series group willhave an increased working voltage and themanufacturer shall, on request, give details ofthe voItage rise caused by blown fuses.

Because of the self-healing properties of thecapacitor, breakdowns are not dangerous anddo not increase the current significantly. But,in the event of rising pressure ( for examplecaused by thermal instability, which may occurat the end of the capacitor, or in some cases,by an excessive number of self-healing break-down, caused by extreme overloads ) the self-healing power capacitor must be protected byan internal overpressure disconnector orequivalent devices.


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Standard Mark

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Revision of Indian Standards

Indian Standards are reviewed periodically and revised, when necessary and amendments, ifany, are issued from time to time. Users of Indian Standards should ascertain that they are inpossession of the latest amendments or edition. Comments on this Indian Standard may besent to BIS giving the following reference:

Dot : No. ET 29 ( 3211 )

mendments Issued Since Publication

Amend No. Date of Issue Text Affected

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Is.13580.Internal Fuses &Internal Overpressure Disconnectors for Power Electronic Capacitors