Oil Circuit Breakers

Transcription

1 ČESKÉ VYSOKÉ UČENÍ TECHNICKÉ V PRAZE Fakulta elektrotechnická Katedra elektrických pohonů a trakce K13114 BE1M 14 ESP Electrical apparatuses and machines Oil Circuit Breakers

2 BE1M14 SSP Electrical apparatuses and machines Arc quenching in bulk oil circuit breaker.

3 BE1M14 SSP Electrical apparatuses and machines Oil circuit breaker

4 BE1M14 SSP Electrical apparatuses and machines AE1B14SP1

5 BE1M14 SSP Electrical apparatuses and machines Working Principle or arc quenching in minimum oil circuit breaker

6 BE1M14 SSP Electrical apparatuses and machines The ionized gas around the arc sweep away through upper vent and cold oil enters into the arcing chamber through the lower vent in axial direction as soon as the moving contact tip crosses the lower vent opening and final arc quenching in minimum oil circuit breaker occurs

7 BE1M14 SSP Electrical apparatuses and machines The cold oil occupies the gap between fixed contact and moving contact and the minimum oil circuit breaker finally comes into open position.

8 BE1M14 SSP Electrical apparatuses and machines position. Whereas in case of radial venting or cross blast, the gases (mostly Hydrogen) sweep the arc in radial or transverse direction. The axial venting generates high gas pressure and hence has high dielectric strength, so it is mainly used for interrupting low current at high voltage. On the other hand radial venting produces relatively low gas pressure and hence low dielectric strength so it can be used for low voltage and high current interruption. Many times the combination of both is used in minimum oil circuit breaker so that the chamber is equally efficient to interrupt low current as well as high current. These types of circuit breaker are available up to 8000 MVA at 245 KV.

9 BE1M14 SSP Electrical apparatuses and machines In oil circuit breakers, the arc is drawn in oil inside a special compartment of the interrupting chamber called the explosion pot. The intense heat of the arc decomposes the oil and produces gases, mainly composed of hydrogen, generating high pressure that produces a fluid flow through the arc and out of the explosion pot through vents situated on its walls. Thus extending the arc s column and carrying its energy away until its total extension see Fig 3.

10 BE1M14 SSP Electrical apparatuses and machines Minimum Oil Circuit Breaker

11 BE1M14 SSP Electrical apparatuses and machines

12 BE1M14 SSP Electrical apparatuses and machines

13 BE1M14 SSP Electrical apparatuses and machines Oil circuit breaker Short circuit protection

14 Air blast circuit breakers Air blast circuit breakers employ a high pressure air blast as an arc quenching medium. Air blast circuit breakers employ a high pressure air blast as an arc quenching medium. Under normal condition the contacts are closed. When a fault occurs contacts are opened and an arc is struck Under normal condition the contacts are closed. When a fault between the them. The opening of contacts are done by occurs contacts are opened and an arc is struck between the a flow of them. air The blast opening established of contacts are done by by the a flow opening of air blast of blast established by the opening of blast valve (located between air valve (located reservoir and between arcing chamber air ). The reservoir air blast cools and the arc arcing and chamber sweeps away the arching products in to the atmosphere. Thus ). The air blast cools the arc and sweeps away the the dielectric strength of the medium is increased, prevents from arching re-establishing products the in arc. to The the arc atmosphere. get extinguished and flow Thus of the current is interrupted. dielectric strength of the medium is increased, prevents from re-establishing the arc. The arc get extinguished and flow of current is interrupted.

15 Air blast circuit breakers employ a high pressure air blast as an arc quenching medium. The circuit breakers are classified on the basis the direction of air blast to the arc. They are classified into Air blast circuit breakers employ a high pressure air blast as an arc quenching medium. 1. Axial Blast Type - air blast is directed along the arc path. Under normal condition the contacts are closed. When a fault occurs contacts are opened and an arc is struck between the them. The opening of contacts are done by a flow of air blast established by the opening of blast valve (located between air reservoir and arcing chamber ). The air blast cools the arc and sweeps away the arching products in to the atmosphere. Thus the dielectric strength of the medium is increased, prevents from re-establishing the arc. The arc get extinguished and flow of current is interrupted. 2. Cross Blast Type - air blast is directed at right angles to the arc path. 3. Radial Blast Type - air blast is directed radially.

16 Air blast circuit breakers employ a high pressure air blast as an arc quenching medium. Under normal condition the contacts are closed. When a fault occurs contacts are opened and an arc is struck between the them. The opening of contacts are done by a flow of air blast established by the opening of blast valve (located between air reservoir and arcing chamber ). The air blast cools the arc and sweeps away the arching products in to the atmosphere. Thus the dielectric strength of the medium is increased, prevents from re-establishing the arc. The arc get extinguished and flow of current is interrupted.

17 Principal arrangement of axial air blast circuit breaker Air blast circuit breakers employ a high pressure air blast as an arc quenching medium. Under normal condition the contacts are closed. When a fault occurs contacts are opened and an arc is struck between the them. The opening of contacts are done by a flow of air blast established by the opening of blast valve (located between air reservoir and arcing chamber ). The air blast cools the arc and sweeps away the arching products in to the atmosphere. Thus the dielectric strength of the medium is increased, prevents from re-establishing the arc. The arc get extinguished and flow of current is interrupted.

18 Construction of axial and radial Air Blast Circuit Breakers

19 Axial Blast Air Circuit Breaker

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21 Operational principle of Cross Blast Air Circuit

22 Air Circuit Breaker This type of circuit breakers, is those kind of circuit breaker which operates in air at atmospheric pressure. After development of oil breaker, the medium voltage air circuit breaker (ACB) is replaced completely by oil circuit breaker in different countries. Nowadays are replaced by SF6 or vacuum circuit breakers. In America ACBs were exclusively used for the system up to 15 KV until the development of new vacuum and SF6 circuit breakers.

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25 Low voltage protecting apparatus

26 Against over-current: Fuses, circuit breakers Fault voltage protection: Residual current circuit breaker Impulse over-voltage: Surge arresters (for HV and LV networks protection)

27 Fuses apparatus operation based on conductor melting in spatial adapted chamber (with extinguishing dust) Melting characteristics Dependence of melting time as a function of current passing through fuse

28 Circuit breaker Time-current switching off characteristics

29 Block diagram of miniature circuit breaker Current sensor Switch Release Current dependent release Current independent release Switch and extinguishing chamber

30 Cross-section of miniature circuit breaker Extuinguishing chamber Electromagnetic release Bimetal release

31 Operational principle of arc quenching in insulated plates chamber under atmospheric pressure Similar principle for metallic plates chamber is used

32 Industrial circut breaker Electric scheme of CB internal connection Electronic control unit

33 Block diagram of circuit breaker electronic control unit Adjustment of current dependent part of disconnecting characteristic Adjustment of current Independent part of disconnecting characteristic

34 Residual current circuit breaker - RCCB Residual current versus time disconnecting characteristics of RCCB

35 Schema of residual current circuit breaker RCCB Switching mechanism Test knob Differential rele Sum-transformer Fault Load

36 Spring Permannent magnet Permannent magnet Anchor Exitation coil Magnetic flux View of RCCB differential relais

37 Application of RCCB in TN-C and TN-S networks

38 Over voltage surge arresters

39 Literature +minimum+oil+circuit+breaker&source=bl&ots=ejitf28-nn&sig=lor4rwzpsqf3oamdvtowpdsivy8&hl =cs&sa=x&ved=0cfsq6aewcgovchmitu_j1tzzyaivhg4uch1yqwab#v=onepage&q=cross%20blast %20minimum%20oil%20circuit%20breaker&f=false

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