What is a impedance relay?

An impedance relay is a voltage restrained overcurrent relay. The relay measures impedance up to the point of fault and gives tripping command if this impedance is less than the relay setting Z.

What is the difference between impedance relay and MHO relay?

impedance is non-directional and used in medium transmission lines. mho relay is directional and used in long transmission lines.

What is the use of impedance relay?

The relay measures the impedance of the faulty point, if the impedance is less than the impedance of the relay setting, it gives the tripping command to the circuit breaker for closing their contacts. The impedance relay continuously monitors the line current and voltage flows through the CT and PT respectively.

What is the difference between impedance and MHO characteristic?

The mho relay is reliable because it combines both the directional and distance measuring functions in one unit. The impedance type relay is suitable for phase fault relaying for lines of moderate length. The arc affects the impedance relay more than the reactance relay but less than the mho relay.

What is an impedance relay explain its operating principle torque equation and operating characteristics for impedance relay?

Therefore from Torque Equation of Impedance Relay, it is clear that operating torque in Impedance Relay is produced by the current whereas restraining torque by voltage. Therefore, Impedance Relay is Voltage Restrained over-current Relay.

Why impedance relay is called distance relay?

As the ratio of voltage to current is nothing but impedance so a distance relay is also known as impedance relay. Hence, it can be said that the relay will only operate when the impedance of the line becomes less than predetermined impedance (voltage/current).

What is impedance protection?

A method of preventing burning damage when the motor is restricted from rotating; done by setting the motor winding impedance (AC resistance) to a value giving a temperature rise in the windings below the temperature at which burning occurs.

Is distance relay and impedance relay are same?

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. The relay will only operate when this voltage to current ratio becomes less than its predetermined value.

What is the difference between directional relay and non directional relay?

Directional relays are designed to locate or sense the fault in a particular direction only, it will not sense fault if fault occurs in opposite direction. While non directional relays don’t have directional features & will sense the fault in both directions.

What is a high impedance relay?

High-impedance bus differential relays are applied to the paralleled output of all CTs from each phase connected to a common bus. As the name implies, the high-impedance bus differential relay presents a very high impedance to the flow of current.

What are the characteristics of impedance relay reactance relay in RX diagram?

The operating characteristics of such relay is a straight line parallel to the x-axis i.e R-axis on R-X diagram. All the impedance vectors have their tips lying on the straight line representing constant reactance. The resistance component of the impedance has no effect on the operation of the relay.