Author: John Mulindi
-
Electric Wiring Testing & Inspection Instruments Requirements
In order to carry out the verification process proficiently, the person conducting the inspection and test must be in possession of suitable test instruments. In this article, we look at some of the key requirements for electric wiring testing and inspection instruments. The commonly used instruments for electric wiring testing and inspection include: Nowadays we…
-
Protective Relays: Function, Features & Operation
A protective relay is basically an electrical device that detects a fault in a power system and initiates the operation of the circuit breaker to isolate the defective section or component from the rest of the system. In other words, the prime function of protective relays is the timely and discriminative clearance of system faults.…
-
SF6 Circuit Breakers: Features, Operation & Applications
Introduction Many modern designs of circuit breakers for use at transmission voltages utilize sulphur hexafluoride (SF6) gas both as an arc-interrupting/arc-quenching and a dielectric medium. At distribution voltages SF6 designs of circuit breakers are also used, however vacuum and bulk-oil circuit breakers still find a wide use as alternatives. The SF6 is an electron-negative gas…
-
5 Causes of High-Voltage Switchgear Failures
Switchgear is basically equipment used switch ON or OFF generators, transmission lines, distributors and other equipment under both normal and abnormal conditions. Switchgear consists of switching and protecting devices such as switches, fuses, circuit breakers, relays, and so forth. In other words switchgear can be defined as equipment used for switching, controlling and protecting the…
-
Main Types of Earthing Systems
Introduction The process of connecting the metallic frame i.e. non-current part of electrical equipment or some electrical part of the system such as the neutral point of the secondary side of the distribution transformers or the star point in a star connected system to the earth is called grounding or earthing. The potential of the…
-
Common Causes of Failures of Power Transformers
As with most of electrical equipment, the key causes of failure of power transformers are either due to electrical failure or mechanical failure. These failures don’t occur that often as compared with other failures in other electrical equipment like switchgear. Common failures of power transformers and their causes are discussed in the following sections. Typical…
-
Three-Phase Diode Bridge Rectifier: Function & Operation
In many high-powered applications, three-phase voltages need to be rectified to give rise to a single DC supply; such rectification can be accomplished using an extension of the bridge rectifier such as the three-phase diode bridge rectifier. Let’s consider the balanced three-phase circuit shown in Figure 1.0 below; the three-phase wye-connected source is connected to…
-
Testing Power and Distribution Transformers
The typical practice for testing power and distribution transformers is to carry out a comprehensive set of tests at the manufacturer’s works. The number and nature of the tests depend on whether the transformer is the first of a new design or not, additionally a few relatively simple tests are done after installation at site…
-
Causes of Ground Loops in Instrumentation & How to Avoid Them
Causes of Ground Loops In Instrumentation We may have situations in instrumentation and control systems, where the sensor and the signal conditioning unit such as an amplifier or current-to-voltage converter are located some distance apart and are connected by a cable. This can lead to several problems that can reduce the accuracy or in extreme…
-
Insulated Gate Bipolar Transistor (IGBT) – Structure, Operation & Applications
IGBT is a voltage controlled device. It has high input impedance like a MOSFET and low on-state conduction losses like a BJT. In other words, this power device combines the voltage control of the MOSFET gate with the superior conduction characteristics of the bipolar device. Nonetheless, the IGBT utilizes injected-charge modulation in the base region…