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 [...]
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 [...]
There are two methods of arc extinction in circuit breakers. They are: 1. High Resistance Method 2. Low Resistance or Current Zero Interruption. 1. High Resistance Method: In this case the arc is controlled in such a way that its effective resistance increases with the time so that the current is reduced to such a value that the heat produced [...]
The circuit breakers may be subjected to widely varying stresses under different operating conditions. The current may vary from a few amperes due to no-load magnetizing current of a transformer to the heaviest short-circuit currents amounting to a hundred kilo-amperes. The circuit impedance may also change within the first 10–4 to 10–3 second because open lines or cables connected to [...]