Which is a directional distance relay?
The admittance relay is the most commonly used distance relay. It is the tripping relay in pilot schemes and as the backup relay in step distance schemes. Its characteristic passes through the origin of the R-X diagram and is therefore directional.
What is an impedance distance relay?
Definition: The relay whose working depends on the distance between the impedance of the faulty section and the position on which relay installed is known as the impedance relay or distance relay. The impedance relay continuously monitors the line current and voltage flows through the CT and PT respectively.
What is distance relay?
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.
What is the main function of numerical distance relay?
Distance relays are the protecting equipment that functions based on the distance of the fault point on the transmission line. The distance is calculated from the generating unit. Based on the distance, the impedance is calculated by evaluating the fault voltage and fault current.
Why mho relay is inherently directional?
A Mho relay measures a component of admittance |Y| ∠θ. It is inherently a directional relay as it detects the fault only in the forward direction.
Where is mho relay used?
Abstract: Mho distance relays are widely used for the protection of uncompensated and series compensated transmission lines in order to determine the presence and location of faults.
What is the difference between impedance relay and mho relay?
Impedance relay is a voltage restrained overcurrent relay. Reactance relay is an overcurrent relay with directional restraint. Mho relay is a voltage restrained directional relay.
Is distance relay and impedance relay same?
The working principle of distance relay or impedance relay is very simple. As the ratio of voltage to current is nothing but impedance so a distance relay is also known as impedance relay. The operation of such relay depends upon the predetermined value of voltage to current ratio.
Why distance relay is called as distance relay?
Distance protection relay is the name given to the protection, whose action depends on the distance of the feeding point to the fault. The relay operates only when the ratio of voltage and current falls below a set value. During the fault the magnitude of current increases and the voltage at the fault point decreases.
What is a distance relay 21?
The goal of a distance relay (ANSI/IEEE code 21) is to trip its circuit breaker(s) if a fault occurs within its programmed “reach” and to ignore both normal operating loads and faults lying outside its reach.
What is the principle of distance protection?
The basic principle of distance protection involves the division of the voltage at the relaying point by the measured current. The apparent impedance so calculated is compared with the reach point impedance.