Table of Contents
- 1 What is the purpose of a differential relay?
- 2 What is differential protection of a generator?
- 3 Why is differential protection used?
- 4 What are the different problems in the differential relays?
- 5 How does generator differential protection work?
- 6 What causes generator differential protection?
- 7 What is the difference between differential and percentage differential relay?
- 8 Why are differential relays used in Transformers and generators?
- 9 How is differential protection provided in a generator?
What is the purpose of a differential relay?
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 is differential protection of a 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.
Why is differential protection used?
Differential protection schemes are mainly used for protection against phase-to-phase fault and phase to earth faults. The differential protection used for power transformers is based on Merz-Prize circulating current principle. Such types of protection are generally used for transformers of rating exceeding 2 MVA.
What is the principle of differential relay?
Definition: The relay whose operation depends on the phase difference of two or more electrical quantities is known as the differential protection relay. It works on the principle of comparison between the phase angle and the magnitude of the same electrical quantities.
What happens in differential relay when saturation is too high?
Overexcitation conditions. Overexcitation of a transformer could cause unnecessary operation of transformer differential relays. When the primary winding of a transformer is overexcited and driven into saturation, more power appears to be flowing into the primary of the transformer than is flowing out of the secondary.
What are the different problems in the differential relays?
Problems Encountered in Differential Protection of Transformer:
- Unmatched characteristics of CTs.
- Ratio change as a result of tapping.
- Magnetizing inrush current.
How does generator differential protection work?
Generator differential protection schemes are designed to detect faults by comparing the current following into and out of the stator. 10, the overcurrent elements are connected to core-balance current transformers (CTs) on a per-phase basis. This allows for the detection of both phase and ground faults.
What causes generator differential protection?
The differential protection is provided in the generator by using longitudinal differential relay. Generally instantaneous attracted armature type relays are used for this purpose because all they have high speed operation and also they are free from being affected by any AC transient of the power circuit.
Why are differential relays more sensitive than over current relays?
Why are differential relays more sensitive than overcurrent relays? Differential relays are used to protect transformers and generators from local faults. Overcurrent relays depend on excess current for their operation. Differential relays are very sensitive to the faults occurred within the zonee of protection.
What is the difference between an overcurrent relay and differential relay?
Hello Brainly user ! ♥ The operating coil of over current relay is connected across the CT secondary circuit. ♥ This differential relay compares the current at the two ends of the alternator winding.
What is the difference between differential and percentage differential relay?
Definition: The percentage differential relay is defined as the relay that operates on the phase difference of two or more similar electrical quantities. It is the advanced form of differential protection relay. The only difference between them is the restraining coil.
Why are differential relays used in Transformers and generators?
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.
How is differential protection provided in a generator?
The differential protection is provided in the generator by using longitudinal differential relay. Generally instantaneous attracted armature type relays are used for this purpose because all they have high speed operation and also they are free from being affected by any AC transient of the power circuit.
How does a differential current protective relay work?
A practical differential current protective relay system would monitor current through all six stator wires on the generator, comparing currents in and out of every phase: If the CT primary currents I C 1 p and I C 2 p are equal and the CT ratios are equal, the CT secondary currents I C 1 s and I C 2 s will be equal as well.
Are there any disadvantages to a differential relay?
There are some disadvantages in the voltage balance differential relay such as a multi tap transformer construction is required to accurate balance between current transformer pairs. The system is suitable for protection of cables of relatively short length otherwise capacitance of pilot wires disturbs the performance.