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 purpose of differential protection?

One of the most important protection in power system is differential protection. It is used to protect the electrical equipment against internal fault such as internal winding short circuit or bus bar phase to phase short circuit, inter turn short, winding puncture etc.

What is differential protection in power system?

Differential protection is one of the most widely used methods for protecting power transformer against internal faults. … The differential relay trips whenever the difference of the currents in both sides exceeds a predetermined threshold.

Where is differential protection used?

The differential protection relay is used for the protection of the generator, transformer, feeder, large motor, bus-bars etc.

What is differential protection in transmission line?

Abstract: Distance relaying principle is a widely used protective scheme for the protection of all types of transmission lines. … Current differential relays are used for the protection of electrical equipment such as transformers and generators against internal faults because of their simplicity and sensitivity.

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What class of CT is preferable for differential protection?

The PS class CT is special protection class CT. Both the PS class CTs used for differential protection have the identical saturation characteristics and their knee point voltage are the same. The designer takes the data like lead resistance,relay burden and system fault level from user before design of PS class CT.

What happens if CT saturates?

If a CT has reached saturation and a switch is opened to remove the primary current, we would expect the magnetic field (H) to disappear and the flux density (B) to reduce to zero. However, flux density does not go to zero when the primary current stops flowing.

What is differential protection of alternator?

Differential protection of alternator or Merz-Price circulating current protection system is a only protection system that protects alternator stator from burning through at least 80% of it. … There are two types fault might occur in a alternator stator, namely phase to phase fault or phase to ground fault.

What are the difficulties of differential protection?

The differential scheme described suffers from the following drawbacks: Unmatched characteristics of CTs. Ratio change as a result of tapping. Magnetizing inrush current.

What is MHO relay?

Mho relay is a voltage restrained directional relay. Important Points: Reactance relay is suitable for the protection of a short transmission line because its operation is independent of arc resistance. The relay which is selected for a long transmission line should be less affected due to power swings.

What is percentage differential protection?

The percentage differential relay is designed to operate the differential current in terms of its fractional relation with actual current flowing through the circuit. It is used to protect the system under Current transformer saturation, unequal CT ratios, nuisance trip etc.

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