Over Current Relay and Its Characteristics

Protection schemes can be divided into two major groups: a) Unit schemes, and b) Non-unit schemes. a) Unit Scheme: Unit type schemes protect a specific area of the system i.e. a transformer, transmission line, generator or bus bar.The unit protection schemes are based on Kirchhoff’s Current Law – the sum of the currents entering an … Read more Over Current Relay and Its Characteristics

Measurement of Medium Resistance by Substitution Method

In Substitution Method, the Resistance whose value is to be measured is compared with the Standard Resistance by some technique which is described in this section. The connection diagram for Substitution Method is given below. Here, R is the unknown Resistance, S the Standard variable Resistance, A is Ammeter and r is Regulating Resistance. When … Read more Measurement of Medium Resistance by Substitution Method

Voltmeter Ammeter Method for Measurement of Resistance

Resistance is classified into three categories for the sake of Measurement. Different categories of Resistance are measured by different technique. That’s why they are classified. They are classified as Low Resistance:  Resistance having value 1Ω or below are kept under this category. Medium Resistance: This category includes Resistance from 1Ω to 0.1 MΩ. High Resistance: … Read more Voltmeter Ammeter Method for Measurement of Resistance

Schering Bridge – Measurement of Capacitance and Dissipation Factor

We will discuss how to measure Capacitance and Dissipation Factor. Capacitance is measured by using Schering Bridge. What is this Schering Bridge? First we will discuss how to balance a bridge.   As we know for balanced bridge, there should not be any current through the detector which means the potential difference across the detector … Read more Schering Bridge – Measurement of Capacitance and Dissipation Factor

Capacitance and Dissipation Factor

A Capacitor is a device which has the capability to store energy in its Electric Field. Therefore we can say that a Capacitor can store charge. There are many types of Capacitor but the most basic Capacitor is Parallel Plate Capacitor. We will consider this basic capacitor for getting idea of basic but important parameters … Read more Capacitance and Dissipation Factor

Dynamic Contact Resistance Measurement, DCRM

First question which strikes in our mind is that why do we need to do DCRM even though we already had Contact Resistance Measurement,CRM? Seems good question and this question will take you to the depth. So, first of all we need to know about the contacts of Circuit Breaker. Basically, a CB has two types … Read more Dynamic Contact Resistance Measurement, DCRM

DC Shunt Motor Charatersitics

Long Shunt and Short Shunt DC Compound Machine: In short shunt DC Compound Machine, shunt filed winding is connected across the Armature whereas in Long shunt connection it is connected across the line terminal. But there is no difference in operating characteristic in two types of machine. DC Shunt Generator Characteristics: There are four basic … Read more DC Shunt Motor Charatersitics