What is differential protection of generator?

1. Generator differential protection (87 G) It is unit type protection, covering the stator winding for phase to phase faults due to breakdown of insulation between stator phase windings.

What is a differential generator?

Differential protection for a generator is mainly employed for the protection of stator windings of generator against earth faults and phase-to-phase faults. The stator winding faults are very dangerous, and it causes considerable damage to the generator.

What is diff protection?

Differential protection is a unit-type protection for a specified zone or piece of equipment. It is based on the fact that it is only in the case of faults internal to the zone that the differential current (difference between input and output currents) will be high.

What are the types of differential protection?

There are mainly two types of differential relay depending upon the principle of operation.

• Current Balance Differential Relay.
• Voltage Balance Differential Relay.

Why NGT is used in generator?

Neutral grounding transformers are a single phase transformer which is used to protect the generator/alternator winding from damaging short circuit. NGT are mainly used to reduce the installation cost of NGR (Neutral Grounding Resistor).

What is the difference between differential protection of transformer and generator?

There is no difference. Differential protection is differential protection. Any internal fault inside the stator winding is cleared by mainly differential protection scheme of the generator. The differential protection is provided in the generator by using longitudinal differential relay.

What are the difficulties experienced in differential relay in generator protection?

If there is any major mismatched in the current transformer’s characteristics of both sides of the generator, there may be high chance of malfunctioning of differential relay during the fault external to the stator winding and also may be during normal operating conditions of the generator.

Which relay is used in differential protection?

Merz price protection scheme is one form of the differential relay which is used to protect the stator winding of Alternator from the internal faults. Differential relay is also used for the protection of transformer winding.

Which relay is used for generator protection?

Reverse power relay is used for this purpose. As soon as the generator starts rotating in motoring mode, the reverse power relay will trip the generator set.

How to implement differential current protection for a generator?

A simple form of differential current protection for this generator may be implemented by connecting CTs on either side of each winding to operating coils of an electromechanical relay like this. For the sake of simplicity, protection for only one phase winding (C) of the generator will be shown.

What is differentdifferential protection?

Differential protection is a very reliable method of protecting generators, transformers, buses, and transmission lines from the effects of internal faults. Relays, which depend on excess of current for their operation, are less sensitive because they cannot make correct distinction between load conditions and minor fault conditions.

What is a differential current protection zone?

The current at each end of the line is monitored by current transformers connected to local 87 relays, which makes the differential current protection zone cover the entire length of the transmission line.

What is the function of a differential protection relay?

The relay checks constantly if the incoming currents of a winding are met by respective outgoing currents. If the balance of the conductor currents shows a difference, this may suggest a fault within the protection zone. Motors and generators are to be handled from the differential protection in the same way.