Overcurrent and Earth-Fault Protection of Transmission Lines: The general practice is to employ a set of two or three overcurrent relays for protection against phase-to-phase faults and a separate overcurrent relay for single line-to-ground faults.
What are three methods of transmission line protection?
If we consider about the protection of transmission line there are three protection types are used to protect these lines .
- Differential Protection.
- Phase Comparison.
- Over Current Protection.
- Earth fault overcurrent protection (Use for protect from large residual current)
- Distance Protection.
Why do we need to protect transmission lines?
As you already know, the real purpose of transmission line protection is to detect faults or abnormal operating conditions and to initiate corrective action. Protective relays must be able to evaluate a lot of parameters to choose and establish right corrective action.
What is transmission line protection system?
Transmission Line Protection. Distance Protection. A distance relay measures the impedance of a line using the voltage applied to the relay and the current applied to the relay. When a fault occurs on a line, the current rises significantly and the voltage collapses significantly.
Which relay is used in transmission line protection?
Distance relays are generally used for phase-fault primary and back-up protection on subtransmission lines, and on transmission lines where high-speed automatic reclosing is not necessary to maintain stability and where the short time delay for end-zone faults can be tolerated.
What is the drawback of protection system?
Disadvantages: The downside was the challenge of installing and testing such a complicated scheme with the potential for mis-operation. I don’t recall any mis-operations occurring, but it was still a bit “dicey”.
Why is speed of protection so important?
Speed of operation is the ability of the protection system to operate in a short time after fault inception. Fast operation is important in preserving system stability, reducing equipment damage, and improving power quality.
Which is a line protection device?
Machines and production lines are monitored and controlled by electronic equipment programmed for specific purposes. SPDs are used for protection against surges from power lines, signal lines, feeder lines and other various line voltage surges, and can be used as class 1, 2 & 3 levels of protection.
What are the types of protection relays?
Basic classification of protective relays includes:
- Electromagnetic Relays: Armature. Induction cup / induction disc.
- Static Relays: Analog input signals are processed by solid state devices.
- Digital / Numerical Relays: Uses programmable solid state devices based on digital signal processing.
What is distance protection of transmission lines?
Distance Protection is a Non-unit System of Protection, which measures the Impedance between the Relay Location and the point where the fault is incident and compares it with the Set Value. If the measured Impedance is less than the Set Value , the Relay operates and Isolates the Faulty Section.