## Over Reach of Distance Relay

What is Meant by Over Reach? To understand the meaning of over reach, let us take an example of double circuit line in which one line is out of service and earthed at both end by Earth Switch. In the figure below, the distance relay is supposed to protect the line 1 due to its … Read more

## Equal Area Criterion and Out of Step Condition

Equal Area Criterion is the method of studying the Transient Stability of system of two machines or single machine connected to infinite bus. The study of Transient Stability tells us whether or not synchronism is maintained i.e. whether or not load angle δ settles down to steady state stable value after the clearance of fault … Read more

## How does Trip Circuit Supervision Work?

Trip Circuit Supervision Circuit senses any fault either in the trip coil of breaker or trip circuit. On sensing a fault, Trip Circuit Supervision Relay changes its contact status to window annunciation on the panel. Here fault in the circuit means any break or open circuit. In this post we will be discussing the working … Read more

## A Brief Introduction to PLCC Panels

Power Line Carrier Communication (PLCC) is used for the purpose of protection of line and communication between the two stations. Two different PLCC channels are used for the protection of a single line. This is the reason, you will notice that wave traps are normally installed in R and B phase of transmission line. The … Read more

## Theory of Arcing Ground-Ungrounded System

Ungrounded System is one where the neutral is not connected to earth. Thus, neutral of ungrounded system is isolated. Arcing Ground is an electrical phenomenon in which the voltage of faulty phase fluctuates due to capacitive charging current. This arcing ground phenomenon is prevalent in three phase ungrounded neutral system. Don’t worry I will explain … Read more

## Point on Wave Switch / Controller

What is Point on Wave Controller / Switch? Point on Wave Switch (PoW) , often called Point on Wave Controller is a high speed microprocessor based relay used for the controlled switching of circuit breaker of HVAC system. Controlled switching refers to open or close a breaker at a pre-determined point on the voltage waveform. … Read more

## What is Relay? – Definition and Types of Relay

What is Relay? “Relay is a device that detects the fault and initiates the operation of the circuit breaker to isolate the faulty element from rest of the healthy power system.” Protection of electrical equipment plays a vital role in Power System not only from the point of view of economy behind costly equipment but … Read more

## Design Basis for Electrical Protection

Electrical Protection is considered as the heart of power system. Protection system should be such robust to isolate the fault in minimum possible time to minimize the equipment damage. The design of electrical protection is based on the following basic considerations: Adequacy The selected protection should be adequate to cover all types of faults and … Read more

## Under Reach of Distance Relay

A distance relay is said to under reach when the impedance seen by relay due to fault is more than the relay setting value even though the fault point is within the protected zone of line. This means that reach of relay has decreased from the setting value. Therefore, percentage under reach can be defined … Read more

## Zero Sequence Filtering in Differential Protection

Zero sequence filtering is a concept used to eliminate zero sequence current component from the secondary current of Current Transformer used in Differential Protection of Transformer. This concept is useful in Transformer having earthed Star winding. What is the Need for Zero Sequence Filtering? Let us have a detailed discussion on this topic. For better … Read more