What is generator differential protection?

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. If CTs of identical ratios are used on neutral and line side of generator, an operating current setting of 20% it can be adopted.

What is the principle of differential protection?

Principle of differential protection Differential protection is based on the fact that any fault within an electrical equipment would cause the current entering it, to be different, from the current leaving it.

What are the generator protections?

Generator Protection Devices

  • Stator Earth Fault Protection (Stator windings phase-to-phase & stator ground or earth faults protection by Differential Relay)
  • Rotor Earth Fault Protection.
  • Unbalanced Stator Loading Protection (Loss of field protection and change in reactive power flow)

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 is the difference between differential protection of transformer and generator?

What is the difference between differential protection of transformer and generator? There is no difference. Differential protection is differential protection. Any winding short either to ground or winding to winding will result in a mismatch of currents causing the differential relay to operate.

Why NGR is used in generator?

So, the primary purpose of an NGR in the power system is to limit the high current that flows because of the line to earth fault. An NGR works as a fault current regulator. It limits the fault current with resistance. Neutral grounding resistors can also help operate the Earth Fault Relay.

What are the main function of differential relays?

Among them differential relay is very commonly used relay for protecting transformers and generators from localised faults. Differential relays are very sensitive to the faults occurred within the zone of protection but they are least sensitive to the faults that occur outside the protected zone.

What are disadvantages of differential protection?

When differential relaying is used for protection, the CTs at both sides of the generator winding must be of equal accuracy. Otherwise if the CT errors are excessive it will cause the mal-operation of the relay.

What are the common types of generator faults?

Generator protection can be divided into the below categories: Internal Faults – Phase and/or ground faults in the stator and/or the field winding (rotor). Abnormal Operating Conditions – Issues such as: loss of field, overload, over voltage, under/over frequency, loss of synchronization, etc.

What is busbar differential protection?

Current Differential Protection. The scheme of busbar protection, involves, Kirchoff’s current law, which states that, total current entering an electrical node is exactly equal to total current leaving the node. Hence, total current entering into a bus section is equal to total current leaving the bus section.

What type of relay protection provided in generator?

Generator backup protection (21G): the generator backup relay shall be of three phase impedance type for one zone protection together with required auxiliary relays and two stage timer to give backup protection for faults in the generator, main transformer and transmission system.

What is differential protection?

Differential protection is a unit-type protection for a specified zone or piece of equipment.

How is differential protection work in a transformer?

Transformer Differential Protection Scheme works by using two separate quantities calculated from the primary current (IW1C) and secondary current (IW2C). SEL787 and SEL 387/587 Transformer differential relay is used for this discussion. Other similar relays use similar concepts through the actual terminology could be different.

What is differential protective relay?

Differential Protective Relay is a protective relay that functions on a percentage or phase angle or other quantitative difference of two currents.