# How Does Distance Protection Work?

## How do distance relays work?

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.

This ratio is nothing but impedance..

## What is the purpose of back-up protection?

5], backup protection is intended to operate when a power system fault is not cleared or an abnormal condition is not detected in the required time because of failure or inability of other protection to operate or failure of the appropriate circuit-breaker(s) to trip.

## Which is the pilotless protection method for line?

Explanation : 18. Which is the pilotless protection method for feeder line ? Differential protection.

## What is arc resistance in transmission line?

The arc resistances occurred due to. fault at the point of fault and rely on the length and fault current during the fault. Meanwhile, ground resistance represented the resistance that touches the live conductor. to the ground. In phase to phase fault, fault is due to arc resistance.

## What is overreach in distance protection?

This is called Over Reach. Mind the word over reach, the word itself means that the relay has actuated beyond its reach setting. “Thus a distance relay is said to over reach if the impedance measured by the relay is less than the apparent fault impedance.” Over reach is often expressed in percentage as below.

## 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.

## What is step distance protection?

Step distance schemes can provide transmission line protection without the use of communication. … The distance elements are supplemented with ground overcurrent protection to provide sensitivity to high-resistance ground faults. The sensitive overcurrent elements are typically used with an inverse timing curve.

## What are the different types of distance relay?

Distance RelaysImpedance Relay. The impedance relay has a circular characteristic centered at the origin of the R-X diagram. … Admittance Relay. The admittance relay is the most commonly used distance relay. … Reactance Relay. The reactance relay is a straight-line characteristic that responds only to the reactance of the protected line.Nov 12, 2010

## 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.

## What is broken conductor in distance protection?

In Broken Conductor Protection, it is assumed that broken conductor do not touch the ground that is why, it is also known as the Open Jumper Protection. … Another type of unbalanced fault which can occur on the system is the series or open circuit fault.

## Where is distance protection applied?

Distance protection schemes are commonly employed for providing the primary or main protection and backup protection for AC transmission line and distribution line against three phase faults, phase-to-phase faults, and phase-to-ground faults.

## 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 are zones of protection?

“Zones of protection” is one strategy that can be used to provide the level of security demanded today. Protective relay engineers keep utility grids and equipment safe from faults and system unbalances by dividing the grid into zones, each with a unique protection scheme. Overlapping zones provide backup protection.

## What is out of step protection?

Protect the power system during unstable or out-of-step conditions. When two areas of a power system, or two interconnected systems, lose synchronism, the areas must be separated from each other quickly and automatically in order to avoid equipment damage and shutdown of major portions of the power system.

## What is distance relay?

The distance relay is a distance protection element designed to measure the faulty point. The operation of this relay depends on the value of the impedance. It trips the circuit breaker and closes the contacts when the impedance of the faulty point is less than the impedance of the relay.