What do you mean by differential protection?
What do you mean by differential 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 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 meant by slope in differential protection?
The slope characteristic provides high sensitivity when low levels of current are flowing in the zone of protection but has less sensitivity when high levels of current are flowing and false differential current due to current transformer (CT) saturation is more likely.
What is differential protection of motor?
Motor overcurrent differential protection measures the current flow into a load and compares it to the current measured on the neutral side of the motor. A current difference is detected as a fault.
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 percentage bias?
Percent bias (PBIAS) measures the average tendency of the simulated values to be larger or smaller than their observed ones. The optimal value of PBIAS is 0.0, with low-magnitude values indicating accurate model simulation.
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.
What is CT saturation?
CT Saturation When the primary current is so high that the core cannot handle any more flux, the CT is said to be in saturation. In saturation, there is no flux change when the primary current changes (as the core is already carrying maximum flux). Since there is no flux change there is no secondary current flow.
When to use percentage differential or biased differential protection?
Percentage differential relay or Biased Differential Protection: Generally differential protection relay means the relay operates when the phasor difference between the two or more electrical quantities exceed the pre-set value. The electrical quantity may be voltage or current. But mostly voltage based relays are not preferred.
When do you use a differential protection relay?
Generally differential protection relay means the relay operates when the phasor difference between the two or more electrical quantities exceed the pre-set value. The electrical quantity may be voltage or current. But mostly voltage based relays are not preferred.
How is differential protection used in a transformer?
It is used to protect the system under Current transformer saturation, unequal CT ratios, nuisance trip etc. It increases the stability of the differential protection relays. Two coils are there in the relay.
How is the slope feature used in differential protection?
To prevent the Differential Protection scheme from picking up under such conditions, a Percentage Differential Protection scheme is used. It improves security at the cost of sensitivity. In Percentage Differential Protection, we provide a slope feature to the Differential Protection Relay.
