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Dry vs Oil type Power Transformers

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To minimize the iron loss during transmission, power needs to be transmitted at a very high voltage. Series of transformers reduce the voltage of the electricity supplied by the towers to a level suitable for use by the electric equipment in the city [220 domestic / 440 Industry].  

The pole mounted oil cooled transformer

Since all of the electricity used by us, passes through several transformers, even a small efficiency improvement will result in significant electricity savings. High efficiency transformers are now available that can reduce your facility's total electricity use. Even if this saving is of the order of one percent, is good money, for Bangalore. It is good for the environment too.

The dual coils of a transformer generate heat while in use which can generate high temperature damaging the winding insulation. Oil-filled transformers have been in operation for over fifty years, where the oil is used as a conductor of heat to the metal cover. The accepted rule of thumb is that Transformer life expectancy is halved for every 8 degree Centigrade increase in operating temperature. It is not uncommon for us to hear the transformer bursts as they explode from time to time. It is important there fore to ensure enough free space for these transformers

The Uphaar Cinema fire, one of the worst fire tragedies in recent Indian history, occurred on Friday, June 13, 1997 at Uphaar Cinema, Green Park, Delhi, during the premiere screening of the movie, Border. Trapped inside, 59 people died, mostly due to suffocation, and 103 were seriously injured in the resulting stampede. The fire broke out at 5:10 pm. According to reports, it was caused when a 1000 kVA electricity transformer, maintained by the Delhi Vidyut Board (electricity Board) (DVB), and housed in the theatre’s overcrowded basement car park, burst, and engulfed some 20 cars, where some 36 cars were parked instead of the admissible. For the full report Click here [2]

Cast-resin power transformers encase the windings in epoxy resin. These transformers simplify installation since they are dry, without cooling oil, and so require no fire-proof vault for indoor installations. The epoxy protects the windings from dust and corrosive atmospheres. However, because the molds for casting the coils are only available in fixed sizes, the design of the transformers is less flexible.

BESCOM needs to optimize the spread / locations of the two types of transformers in Bangalore if not done already. 

Comments

psaram42's picture

Oil Type Transformer in a Bank

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The ordinary oil type transformer example in a Bank in Indiranagar 12th main.

State Bank Of India at 12 th main Indiranagar Bangalore. The oil type transformer is in the SBI premises next to the ATM.

murali772's picture

'burst' - wrong terminology

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It is not uncommon for us to hear the transformer bursts as they explode from time to time. It is important there fore to ensure enough free space for these transformers.

"Transformer burst" is a wrong terminology. Transformers are always protected by 'curcuit breakers', and the loud sound of the tripping of the CB, when a fault develops in the circuit, is mistakenly referred to as a 'transformer burst'.

Poor manufacturing practices invariably lead to leakage of oil from transformer tanks, which makes for a serious fire hazard. And, that's exactly what happened in Uphaar cinema (Delhi). And, as to why transformers should be of poor quality, when India is a leading exporter of engineering goods, the reason may be found here.

BESCOM has certainly changed for the better after Mr Manivannan has taken over as the MD. But, BESCOM's finances continue to be in the doldrums, and there is not much that Manivannan can do to change that (check this)

Resin-cast transformers are about twice the cost of oil-filled transformers, and with BESCOM's financial position being what it is, don't ever expect them to use resin-cast transformers.

Muralidhar Rao

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