Tag: Power systems
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Types of Insulators used in Power Systems
We have various types of overhead line and substation insulators. Generally they can be classified as: Post Insulators The post insulators comprise of pedestal posts and solid core cylindrical types. Pedestal post insulators The pedestal post insulator stacks employed in substations are available as single units with a range of lighting impulses withstand ratings (LIW)…
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How Ground Fault Interrupter (GFI) is used as a Safety Device
The function of a ground fault interrupter (GFI) is to disconnect the power if a current leakage to ground is detected. GFI is also termed to as Ground fault circuit interrupter (GFCI). We have two types of ground fault interrupters: those designed for life protection and those designed for equipment protection. GFI used for life…
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Single-phase and Three-phase Power Systems
Single-phase Power System To help us understand single-phase power system, consider the sine wave shown in figure 1(a) below of a 120 Vac single-phase power connected to a plug. We know very well that, voltage is the difference in potential between two points. Therefore the sine wave in figure 1(a) shows only the voltage difference…
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Alternating Currents and Voltages
Alternating current generator Let’s consider a signal turn coil rotating freely at a constant angular velocity symmetrically between the poles of a magnet as illustrated below: The ends of the loop are terminated in slip rings. As the loop rotates, side A will have an emf induced first in one direction and then in the…
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Switchgear Equipment
Switchgear can be defined as equipment used for controlling, regulating and switching ON and OFF power circuits. Switchgear units range from the small moulded-case unit circuit breakers in a household panel board to the huge, air break switches on 750 kV transmission lines. Switchgear equipment is generally divided into four groups, namely: Disconnect/Isolator Switches Disconnect…
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Power Measurement in AC Circuits (Single-phase & Polyphase Systems)
Introduction to AC Power Measurement In alternating current circuits, the instantaneous power varies continuously as the voltage and current varies while going through a cycle. In this case the power at any instant is given by: p(t) = v(t) x i(t) Where, p(t), v(t) and i(t) are the values of instantaneous power, voltage and current…
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Ideal Transformers
A transformer consists of several coils wound on a common core that usually consists of laminated iron (to reduce eddy-current loss). Transformers are usually used to adjust the values of ac voltages. A transformer can step up or step down voltage. Transformers are used in electric power distribution. To transport power over long distance, large…
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Single-phase vs. Three-phase Power Systems
Thomas A. Edison’s work on electric light led to the concept of a centrally located power station with distributed electric power for lighting. Edison’s work on dc systems expanded with the development of three-wire 220 V dc systems but transmission distances and loads continued to grow, voltage problems were encountered but with the development of…
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Power Measurements in DC Circuits
Measurement of electric power is essential in both commercial industrial applications and domestic applications. Prior estimation and subsequent measurements of instantaneous and peak power demands of any installation are mandatory for design, operation and maintenance of the electric power supply network feeding it. How Power Measurements in DC circuits are done using an Ammeter and…