The application of a particular relay is governed by its characteristics and other factors such as accuracy, operating time, reliability, burden, method of setting adjustment etc. The function of a protective relay is to sense any abnormal condition in the system and send a signal to the breaker which in turn isolates the faulty section of the feeder from the [...]
Amplitude comparator compares the amplitudes of two (or more) input quantities. The phase angle between the quantities under comparison (inputs) is not recognized or noticed by the amplitude comparator. If the two input signals are S1 and S2 (say S1 the operating and S2 restraining), the amplitude comparator gives positive output only if – S2/S1 < K. The function is [...]
Phase comparison technique is the most widely used technique for all practical directional, distance, differential and carrier relays. In a phase comparator, the operation of the relay takes place when the phase relation between two inputs S1 and S2 varies within certain specified limits. Both inputs must exist for an output to occur; ideally, operation is independent of their amplitudes, [...]
Distance relays can be either single phase or polyphase using multi-input comparators. Such multi-input comparators may be instantaneous or integrating type and compare either phase or amplitude or both. The characteristics of conventional two-input comparators are in the forms of straight lines, circles or sectors of circle on complex plane. Multi-input comparators may have elliptical, conical or quadrilateral characteristics on [...]
The following points highlight the four main types of electrical quantities. The types are: 1. Electric Charge 2. Electric Current 3. Electromotive Force and Potential Difference 4. Electric Field Strength. Type # 1. Electric Charge: Electrical energy transfer occurs because of the action of electrical charges. Electric charge is an indication of the quantity of electricity and is usually denoted [...]
SI is the latest form of metric system and absorbs in it the rationalized MKSA system. SI stands for "Systeme International d' Unites" in French. This abbreviation is now adopted by the International Standardising Organisation as the abbreviated name of this new system of units in all languages. The SI system is, in fact, simply the RMKSA system expanded by [...]
In this article we will discuss about:- 1. Introduction to Per-Unit (PU) Method 2. Selection of Bases for Per-Unit (PU) Method 3. Determination 4. Change of Base 5. Per-Unit Impedance 6. Advantages and Drawbacks. Contents: Introduction to Per-Unit (PU) Method Selection of Bases for Per-Unit (PU) Method Determination of Base Impedance in Per-Unit (PU) Method Change of Base in Per-Unit [...]