Back Charging

Charging through back in a switch yard is known as back charging in switchyard. You can watch this in some movies.

After a switchyard erection is complete, how do you test that the clearances, creepage distances, etc. are okay? You have to apply the rated voltage or the recommended test voltage for ensuring the same. But, where from will you get such a high voltage. The only possible supplier - the grid - would not be supplying the system with high voltage unless it is proven by tests that the switchyard is capabnle of withstanding that high voltage. Thusw, you are in a "CATCH-22" situation.

The only way out is to "step-up" the available voltage at the site using a transformer. This is called back-charging of the switchyard.

The procedure is lengthy one. You need to take a lot of precautionary steps before undertaking this back-charging of a switchyard. Reputed Electriocal Testing agencies would help you in getting the procedure.