[Guest]

Please explain the difference between dead tank & live tank type CTs with relative merits/demerits and constructional difference.
Please explain the difference between dead tank & live tank type CTs with relative merits/demerits and constructional difference.

Topic

[Hamid]

Circuit breakers: Circuit breakers are available as live tank, dead tank, or grounded tank designs. Dead tank means interruption takes place in a grounded enclosure and current transformers are located on both sides of the break (interrupter contacts). Interrupter maintenance is at ground level and seismic withstand is improved versus live tank designs. Bushings (more accurately described as gas-filled weathersheds, because, unlike the condenser bushings found on bulk oil circuit breakers, gas breakers do not have true bushings) are used for line and load connections that permit installation of bushing current transformers for relaying and metering at a nominal cost. The dead tank breaker does require additional insulating oil or gas (i.e., more insulating oil or gas than just the amount required to perform successful interruption and to maintain adequate dielectric strength) to provide the insulation between the interrupter and the grounded tank enclosure. Live tank means interruption takes place in an enclosure that is at line potential. Live tank circuit breakers consist of an interrupter chamber that is mounted on insulators and is at line potential. This approach allows a modular design as interrupters can be connected in series to operate at higher voltage levels. Operation of the contacts is usually through an insulated operating rod or rotation of a porcelain insulator assembly via an operating mechanism at ground level. This design minimizes the quantity of oil or gas required as no additional quantity is required for insulation of a grounded tank enclosure. The live tank design also readily adapts to the addition of pre-insertion resistors or grading capacitors when they are required. Seismic capability requires special consideration due to the high center of gravity of the live tank breaker design, and live tank circuit breakers require separate, structure mounted, free standing current transformers. Grounded tank means interruption takes place in an enclosure that is partially at line potential and partially at ground potential. Although the grounded tank breaker

[V.K.Nambiathiri]

In 400kV substatons which type breaker $CTs , Dead or Live tank Type, preferred?

[Hamid]

Dead tank is more applicable.

[V.K.Nambiathirt]

Thanks a lot

[shozab kazmi]

Dear Hamid What is the advantage of live tank over dead tank…as we are using live tank ct in 800kv, 420kv,220kv,132kv.. what is the reason using live tank type…as u said that “Dead tank is more applicable” shozab.

[S.K.Deore]

describe us the details of live tank PT & how it works?

[Saptarshi Chatterjee]

Dead Tank is more applicable because its cheaper. The manufacturing of bushing for power transformer can be used is this case and automatic wrapping of paper made it easy to manufacture (time and cost reduces) and available in plenty from many manufacturers. Installation is easier since the tank is far from live line. Advantages of Live tank –> a) Shorter primary conductor gives better rigidity and high short circuit current withstanding capability. b) With uniformly distributed primary winding these CTs are with lower reactance –>provides inherent better transient performance. c) Main source of heat – high current part is only in primary tank — ensures less heating of bushing/core compared to dead tank type design. This ensures better thermal stability and less problem created through dissolved gas in insulating oil. In case something goes wrong – a well designed live tank CT wont explode only from top unlike the blast of insulator core of dead tank CTs’ which can damage human life a well as the other substation equipments nearby. Regards Saptarshi

[Author]

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