Why IDMT relays are widely used for over current protection?
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Why IDMT relays are widely used for over current protection?
Inverse Definite Minimum Time Relay The operating time of the relay is maintained by adjusting the time delay setting. The IDMT relay uses the electromagnetic core because it can easily saturate for the current having larger magnitude than pick up current. The relay is used for the protection of the distribution line.
Which relay is preferred for distance protection scheme for long transmission line?
Mho relay
The relay which is selected for a long transmission line should be less affected due to power swings. Hence Mho relay is preferred.
Which of the following distance relays is better suited to protect short transmission lines?
A distance protection relay is a name given to the protection, whose action depends on the distance of the feeding point to the fault….4.6.
| Transmission line | Length & Operating voltage | Distance Relay |
|---|---|---|
| Short-line | (0-80) km (0-20) kV | Reactance relay |
| Medium line | (80-200) km (20-100) kV | Impedance relay |
What is distance relay protection?
A distance relay is a type of protection relay most often used for transmission line protection. Distance relays measure the impedance from the installation side to the fault location and operates in response to changes in the ratio of measured current and voltage.
Why do we need distance protection?
So during any fault, the current would rise and the voltage will decrease. This relay would detect the impedance according to the current and voltage. The impedance of the line will be proportional to the fault distance and that’s why it is called distance protection.
How does an IDMT relay work?
IDMT relay is inverse definite minimum time relay. It is one in which Time of operation is inversely proportional to magnitude of fault current near pickup value and becomes substantially constant slightly above the pickup value of the Relay.
Why is distance protection necessary?
Distance protection is comparatively simple to apply and it can be fast in operation for faults located along most of a protected circuit. It can also provide both primary and remote back-up functions in a single scheme. It can easily be adapted to create a unit protection scheme when applied with a signalling channel.
Why are distance relays used in transmission lines?
Introduction. A distance relay is a type of protection relay most often used for transmission line protection. Distance relays measure the impedance from the installation side to the fault location and operates in response to changes in the ratio of measured current and voltage.