In this article we will discuss about induction type directional relays used in an electric circuit. Induction Type Directional Power Relay: The non-directional relay can operate for fault flow in either direction. In order to achieve operation for the fault flowing in a specific direction, it is necessary to add a directional element to the non-directional element. The directional (or [...]
Differential protective relaying is the most positive in selectivity and in action. It operates on the principle of comparison between the phase angle and magnitudes of two or more-similar electrical quantities. Comparing two electrical quantities in a circuit by means of differential relays is simple in application and positive in action. For example, in comparison of the current entering a [...]
It is noteworthy here that in electrical engineering, the term 'impedance' can be applied to resistance alone or reactance alone, or a combination of the two. In protective relaying terminology, however, an impedance relay has a characteristic that is different from that of a relay responding to any component of impedance and therefore, the "impedance relay" is very specific. An [...]
In this article we will discuss about:- 1. Meaning of Static Relays 2. Need for Static Relays 3. Essential Components 4. Advantages 5. Limitations. Contents: Meaning of Static Relays Need for Static Relays Essential Components of Static Relays Advantages of Static Relays Limitations of Static Relays 1. Meaning of Static Relays: A static relay refers to a relay in which [...]
In this article we will discuss about operation and mounting of circuit breaker. Operation of Circuit Breaker: Each circuit breaker is provided with an operating mechanism. The functions of this mechanism are: (i) To close the breaker contacts rapidly without hesitation at all currents from zero to rated making current capacity (ii) To hold the breaker contacts together against the [...]
Relative merits and demerits of different types of conventional circuit breakers (bulk-oil circuit breakers, minimum oil circuit breakers and air-blast circuit breakers) are given below: 1. Bulk-Oil Circuit Breakers: Merits: Simplicity in construction, high rupturing capacity, suitability for automatic as well as manual operation; possibility of locating CTs in bushings. Demerits: Larger size and greater weight, fire hazard, explosion hazard, [...]
The overcurrent relays, even though simplest of all types of electromechanical relays, are the most difficult static relays. This is because the induction disc characteristics of the overcurrent relays (inverse characteristics) are not amenable to simple mathematical analysis. The first static relays developed were the high speed differential relays and the distance relays. Fault current level detectors are termed overcurrent [...]
Here is a list of air-break circuit breakers: 1. Plain Break Type Air-Break Circuit Breaker 2. Magnetic Blow-Out Type Air-Break Circuit Breaker 3. Arc-Chute Air-Break Circuit Breaker. 1. Plain Break Type Air-Break Circuit Breaker: Plain break type air-break circuit breaker is the simplest one in which contacts is made in the shape of two horns. The air initially strikes across [...]
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 [...]
In this article we will discuss about:- 1. Construction of SF6 Circuit Breakers 2. Properties of Sulphur Hexafluoride Gas 3. Arc Extinction 4. Advantages 5. Problems Associated. Contents: Construction of SF6 Circuit Breakers Properties of Sulphur Hexafluoride Gas Arc Extinction in SF6 Circuit Breakers Advantages of SF6 Circuit Breakers Problems Associated With SF6 Circuit Breakers 1. Construction of SF6 Circuit [...]