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 [...]
Static relays are classified according to the type of the measuring unit or comparator as follows: 1. Electronic Relays 2. Transductor (Magnetic Amplifier Relays) 3. Rectifier Bridge Relays 4. Transistor Relays 5. Hall Effect Relays 6. Gauss Effect Relays. 1. Electronic Relays: These were the first to be developed in the series of static relays. Fitzgerald presented a carrier current [...]
Distance relays are characterised by having two input quantities proportional to the voltage and current at a particular point in the power system, referred to as the relaying point. Ideal static distance relays have characteristics independent of actual magnitudes of voltage and current but dependent only on their ratio and phase angle between them. The versatile family of distance relays [...]
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 [...]
In this article we will discuss about:- 1. Meaning of Circuit Breakers 2. Operating Principle of Circuit Breakers 3. Arc Phenomena 4. Arc Extinction 5. Resistance Switching 6. Ratings. Meaning of Circuit Breakers: Circuit breakers are mechanical devices designed to close or open contact members, thus closing or opening of an electrical circuit under normal or abnormal conditions. Automatic circuit [...]
In this article we will discuss about:- 1. Principle of Arc Extinction in Air-Blast Circuit Breakers 2. Types of Air-Blast Circuit Breakers 3. Features 4. Drawbacks. Principle of Arc Extinction in Air-Blast Circuit Breakers: The air-blast circuit breaker requires an auxiliary compressed air system which supplies air to the breaker air receiver. When opening is required, compressed air is admitted [...]