What is line current differential protection?
An alternative principle for line protection that is quickly becoming the norm is differential protection. Differential protection is based on Kirchhoff’s laws, stating that all current into a network node shall add up to 0 in an ideal system.
What is bias setting in differential protection?
The purpose of biased differential protection is to detect faults with high selectivity and sensitivity. This means that it can trip with no intentional time delay for faults within its zone of protection, the reason why differential protection is often applied on high value equipment such as transformers.
What is cable differential protection?
In this cable/line design, cable differential protection provides reliable discrimination between faults in the cables and on overhead lines. They exchange current phasor information to determine if a fault is on the cable (In-Zone) or on the overhead line (Out-of-Zone).
What is differential protection system?
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 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 benefits of the current differential protection?
The key benefits of differential protection as applied to power lines include good performance on multiterminal and series-compensated lines and lines of any length as compared with distance or directional comparison schemes; considerable immunity to changing system conditions, long-term evolution of the system, or …
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 are the drawbacks 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 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 the problems in bus zone differential protection?
What are the problems in bus zone differential protection? _ Large number of circuits, different current levels for different circuits for external faults. _ Saturation of CT cores due to dc component and ac component in short circuit currents. The saturation introduces ratio error.