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...

Inductance of Single Conductor of Transmission Line

Inductance is the property of a conductor due to which it opposes a sudden change in current through it and a basic electrical parameter like resistance and capacitance. Inductance is defined as the total flux linkage per unit current. To analyse the electrical behavior of...

Calculation of Multiplication Factor of Energy Meters

Energy Meters are one of the important instrument to account for energy imported / exported in an industry. In Power Generating Stations, the cumulative reading of such energy meters are used for the calculation of total Million Units (MUs) of energy exported. On the basis...

Ring Main Unit (RMU) – Introduction

Ring Main Unit,RMU is a compact, enclosed and sealed type of Switchgear used for medium voltage power distribution. It is a complete Switchgear in itself. A complete Switchgear means, assembly of required switching devices, protection device as well as metering device. RMU of different voltage...

How to Disable Full DR Alarm in Numerical Relay?

These days mostly Numerical Relays are used for protection purpose instead of conventional Electromechanical Relays. In fact, Numerical Relays offer a variety of protection as well as trouble shooting features. A single Numerical Relay can provide many protection unlike conventional Electromechanical Relays. A single Numerical...

Strain Gauge and Gauge Factor

Strain Gauge is basically a sensor used for the measurement of various physical parameters like stress, strain etc. The working principle of strain gauge is based on Piezoresistive Effect. This is why it is also often called Pizoresistive Gauge. When a metal conductor is stretched...

Accuracy Limit Factor of Current Transformer

Accuracy Limit Factor of Current Transformer is a very important factor while selecting a CT for protection purpose. A current transformer chosen for protection purpose are defined by protection class āPā. The whole and sole requirement of a protection class CT is to maintain its...

HSV / NSV Rating of Electric Equipment

You might surprise to hear about HSV & NSV Rating of Electric Equipment. If you ever get a chance to visit a EHV Switchyard, you will notice that HSV / NSV rating is mentioned on every equipment connected to the Switchyard. I was also wondering...

Instrument Safety Factor of Current Transformer

Instrument Safety Factor Instrument Safety Factor (ISF) is defined as the ratio of CT saturation current to its rated current. Suppose the CT ratio is 2000/1 and the CT gets saturated if there is flow of 10 kA current through its primary, then Instrument Safety...