Author: John Mulindi
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Air-Blast Circuit Breakers: Features, Operation & Applications
Air-blast circuit breakers utilize a blast of compressed air typically at a pressure of 25–75 bar, which is directed across the path to cool and eliminate the ionized gas, in other words the air-blast is employed as the quenching medium. The air-blast cools the arc and sweeps away the arcing products to the atmosphere. This…
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Testing & Commissioning Protective Schemes
Generally protective equipment testing may be divided into three stages: Factory and commissioning tests confirm the performance of equipment during its development and fabrication, and its operational environment. Periodical maintenance ensures that this performance is maintained. For example, the relay manufacturer must provide sufficient testing of protective gear before it is accepted and commissioned. The…
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Digital Multimeter: Principle of Operation and How it is used
A Multimeter or volt-ohm-milliammeter (VOM) is an instrument used to measure current, voltage, and resistance. It can be used for measuring dc as well as ac voltages and currents. The two common types of multimeters include the analog multimeter and the digital multimeter. Analog multimeters employs a moving pointer mechanism that swings a long a…
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The Principles of Power System Protection
The Function and Principles of Power System Protection The objective of power system protection is to detect faults or abnormal operating conditions and initiate corrective action. Principles of Power System Protection There are different principles used in accomplishing power system protection, we have discussed them in the following sections: Discrimination by Time In simple radial…
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Overvoltage Protection Techniques & Equipment
Overvoltage Protection – Objective, Methods & Equipment The purpose of the protective equipment in a power system is to isolate the faulty section from the healthy system by initiating tripping for appropriate circuit breakers. This whole process must be carried out with minimum of delay and disturbance. Overvoltage, switching and other phenomena like lightning produce…
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Single-Ended vs. Differential Amplifiers
Most often than not, the signal from the sensor in a measurement and control or monitoring system is very small (one millivolt or less) and a key step in signal conditioning is amplification. Therefore, the sensor is often connected to the input terminals of an amplifier. The amplifier in this case can either be single-ended…
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What is Corona Discharge in Power Transmission Conductors?
Corona and its Effects in Power Transmission Systems What is Corona? Corona is the term used to describe the violet glow or ‘brush’ discharge around conductors when the air is stressed beyond the ionization point without flashover developing. When an alternating potential difference is applied across two conductors whose spacing is large as compared to…
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6 Types of Machine Guards
What is Machine Guarding? Most machines have cutting blades or rotating/moving parts that can cause bodily harm if they come in contact with plant workers operating the equipment or working nearby. To protect workers from hazards related to machinery, machine guards are used. Machine guarding is a safety mechanism that typically comprises of a shield…
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Air Circuit Breakers: Features, Operation & Applications
Air Circuit Breaker Features & Operation An air circuit breaker employs atmospheric air as its interrupting medium. The arc is drawn between its contacts and extended via arc runners on to an arc chute where it is presented with a large cooling surface of arc splitter plates. These break the arc into a number of…