In a ground-neutral system, the protection of the transformer can be made by isolating the earth tank or by means of an intensity transformer in which an overcurrent relay is installed.
The overload protection is designed to protect the insulation of the windings against damage caused by heating. Generally the transformers have a temperature indicator on the top of the oil, which can trigger an alarm contact by means of a capillary tube. gates 4L880
There may also be used thermal relays, direct or secondary, which have an instantaneous tripping or timing device.
As for back-up protection, the transformer must be protected against overheating caused by the delayed circulation of fault currents. This protection can be carried out if there is support protection provided by other means, eg generator protection.
The protection functions are those that are addressed in addition to the protection functions approach, the parameter values are also indicated.
After investigating several protection relays, it was decided to adopt the multifunction relay to carry out the alternator protections. The main functions are guaranteed in duplicate, while the other protection functions are guaranteed by the DTP-B and GPM-F-H relays.