What will happen if the secondary winding is shorted?
If the secondary coil is shorted, the current in this coil is so directed that it opposes a change of the flux. Therefore the variation of the flux is much smaller, and so is the induced voltage in the primary coil. Therefore, the current in the primary coil increases indefinitely.
What happens if the secondary of a potential transformer is open circuited?
Ans) If the secondary of Ct is open, it means that there will be no current flowing on secondary side and hence no mmf, whereas current will be flowing in the primary side and there will be mmf produced.
Why does a CT need to be shorted?
CT shorting blocks are used to create an intermediate contact point between the meter and load where it is safe to perform wiring alterations. Once the current transformers are properly shorted using the CT shorting block, it is safe to make wiring modifications on the meter side of the shorting block.
Why is the primary winding of current transformer always shorted?
We know that, in a CT the primary current is dependent on the load current or line current as CT is connected in series with the line. So, primary current of CT (assuming constant line current) is constant irrespective of whether the secondary of CT is connected with burden or not.
What can cause a power transformer to fail?
Most of the dielectric interruptions occur suddenly, especially due to lightning or to an abnormal tension, causing a direct failure. Excessive current by an external short circuit or by a mechanical hit also happen suddenly. Disturbances by earthquakes and fires can accidentally damage the transformer.
How is the fault current of a transformer determined?
This also varies with the position of the fault, so that the fault current in the transformer primary winding is proportional to the square of the fraction of the winding that is shortcircuited.
Why does a short circuit of a winding cause a fault?
A short circuit of a few turns of the winding will give rise to a heavy fault current in the short-circuited loop, but the terminal currents will be very small, because of the high ratio of transformation between the whole winding and the short-circuited turns.