# How do you coordinate a protection relay?

Contents

## What is protection relay coordination?

A protective relay is a sophisticated device designed to calculate power measurements within large industrial circuit breakers, and to trip that circuit breaker when it senses abnormal conditions or faults before they occur.

## What is protection relay configuration?

Each protection unit comprises a definite-time delay overcurrent relay in which the operation of the current sensitive element simply initiates the time delay element. Provided the setting of the current element is below the fault current value, this element plays no part in the achievement of discrimination.

## What is power protection coordination?

Power system protection is a branch of electrical power engineering that deals with the protection of electrical power systems from faults through the disconnection of faulted parts from the rest of the electrical network. … The devices that are used to protect the power systems from faults are called protection devices.

## Why do we need relay coordination?

Relay coordination is an important aspect in the protection system design as coordination schemes must guarantee fast, selective, and reliable relay operation to isolate the power system faulted sections. Thus the relay coordination problem is formulated, for a real time distribution system is simulated using ETAP.

## Which relay is used for feeders?

A MHO relay is used for distance protection on a line, a translay relay is used for line differential protection via a pilot scheme, a Merz Price relay is used for generator differential protection, and a Buchholz relay is used for transformer protection.

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## Which relay is used in transformer?

Relays for Transformer Protection

SL Voltage Ratio and Capacity of Transformer Common Relays
9 400/220KV 315MVA Differential Relay Overflux Relay Buchholz Relay OLTC Buchholz Relay PRV Relay OT Trip Relay WT Trip Relay Over Load (Alarm) Relay

## How do you calculate protection relay?

Calculation of Over Current Relay Setting:

1. Over Load Current (In) = Feeder Load Current X Relay setting = 384 X 125% =480 Amp.
2. Required Over Load Relay Plug Setting= Over Load Current (In) / CT Primary Current.
3. Required Over Load Relay Plug Setting = 480 / 600 = 0.8.

## 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.