Lighting Transformer

Maybe the lighting circuits are phase-to-neutral 240V, not available on the primary side?

Because that's what the Engineer designed it to be. If you look at the Engineering prints you'll find his name there. Send him an inter office e-mail and ask him.

Generally in a power station the 415 V supply is three wire.There is no neutral. Lighting is generally connected between phase and neutral. Hence, as a neutral has to be created a lighting transformer is used.

Regards,

S. V. Iyer

Dear Guest,

In the Sub-Station -in the Step-down Transformer there may not be NEUTRAL. For Single Phase Circuit, NEUTRAL IS REQUIRED hence a small Transformer is used.

DHAYANANDHAN.S., INDIA

There's an echo around here

You are absolutely right. Another reason is to limit the fault level.

What is the rated voltage of generator?. If not 415V,a step down transformer with secondary voltage of 415V and earthed neutral could be used.

Lighting transformers are usually installed to ensure the lighting supply voltage remains at the optimum level necessary for increased life of the fittings and lamps, over voltage can reduce this considerably.

Delta/ Star (neutral grounded) is used in substation for for the following reasons:

For electrical isolation in case of occurence of fault from primary side of transformer( i.e main L.T. Bus feeding from main transformer)

High % impedance of lighting transformer to restrict fault current.

Generally lighting loads suffer from frequent short circuits. Hence to isolate the main system from these disturbances, a lighting transformer with a delta star scheme may be used.

Dear All, In our plant we use a 415/433 V lighting trafo for lighting distribution through LDB. Usually it is provided with Off Circuit Tap Changer to adjust the voltage on the Load Side when ever the Incoming Voltage increase or decreases. Through the star side single power for single phase load can be derived.