Distribution Transformers

Distribution Transformers play a vital role in the system which delivers electricity to the end user.   It is the final part of the transmission system from the power plant to the consumer.  Distribution Transformers step down the MV power, usually 11kv into the domestic LV, 440 V supply.

Distribution Transformers are a critical part of the distribution network.  These transformers are always online throughout the year.  Hence, design of the distribution transformer is made considering the high iron losses.  Besides, the transformer is sized to have high efficiency at 70% of the load as the power output varies through the day as per the load cycle. 

Distribution transformer are protected by fuses in the HV side.  They are also designed to withstand unbalanced loading.  They have ONAN cooling (Oil Natural, Air Natural ). 

Distribution Transformer are usually of the vector Dyn11.  While, designers are not particular about any particular vector group , most systems will standardize on one particular vector group, usually the Dyn11.  Some systems also use the Dyn1.  These vector groups have a difference of 30 degrees between the primary and secondary vectors which is unavoidable in delta to star conversion.

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