Power System Protection

Anti Pumping Relay is used in a Circuit Breaker to indicate the spring failure of TNC i.e. Trip Neutral and Close (TNC) switch. TNC switch is used to manually Open and Close the Circuit Breaker either from Local or Remote. This is called TNC switch as it has three positions ...
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Relay is a switch which senses fault in a system and once fault is sensed by the Relay, it issues trip command to the Circuit Breaker, CB to isolate the faulty section of the network from the healthy section.The Relay detects the abnormal condition by continuously monitoring electrical quantities which ...
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The length of the Transmission Line at its voltage level decides its classification as Short / Medium /Long Transmission Lines. A typical transmission line circuit looks like as shown below.We can see that there are infinite numbers of cascaded units in a Transmission Line. If we want to analysis, it ...
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The majority of faults on a power system occur between one phase and ground or two phases and ground. These are known as shunt faults and arise from lightning discharges and other over voltages which initiate flashovers. Alternatively, they may arise from other causes such as birds on overhead lines ...
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Before going into the calculation part of Stabilizing Resistor, I will first explain the purpose of Stabilizing Resistor in High Impedance Differential Protection. Stabilizing Resistor in High Impedance Differential Protection is used to prevent the operation of Relay in case of through fault. Through fault is a fault outside the ...
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We are now aware of the concept of Sequence components of current / voltage. If you have miss this concept, please read Concept of Symmetrical Components.   Now we are at a stage to calculate the zero, positive and negative sequence components of current / voltage. As already discussed any three ...
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Generator, Generator Transformer and Unit Transformer protections have been classified into Class-A, Class-B and Class-C. Class-A tripping is further classified into Class-A1 and Class-A2. Class-A, Class-B and Class-C Tripping Classification of Generator is based on the need of isolation of Generator on the basis of type of fault. In this post we ...
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MCB stands for Miniature Circuit Breaker which is widely used in home and industries. A Miniature Circuit Breaker (MCB) is a small circuit breaker that is used for residential and industrial applications.       Like every circuit breaker, it has both a switching function (it allows the connection / ...
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Electrical Faults can be classified into two categories: 1) Shunt Faults and 2)   Series Faults   Shunt faults include power conductor or conductors to ground or short circuit between the conductors.   Series type of fault is basically unbalance in system. Suppose we have used Fuse / Breaker to protect ...
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The concept of Subtransient, Transient and Steady State arises in case of fault in an Alternator. Let us assume a sudden short circuit in three phase of alternator. The fault current will flow in all the three phases of alternator and its waveform will be as shown in figure below ...
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Being an Electrical Engineer, it is very important to have clear concept of Symmetrical Components used for the analysis of fault or unbalance in a Power System. Basically Symmetrical Components are mathematical modeling used to simplify the calculation while maintain the physical significance of components.   The concept of Symmetrical ...
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Dead Machine Protection of Generator ensures that Generator is not energized accidentally in standstill condition or when the Generator is on Turning Gear. Accidental energization of Generator when the machine is not running can cause severe damage to the machine, thus Dead Machine Protection becomes important to consider. (How? You will ...
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An isolator is a switch used in power lines, to completely open (physically) a specific section of line, when maintenance or modification work is to be done. The isolator can be operated manually, or in some cases, opened by energizing a motor. With a three-phase system, the isolator opens all ...
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Relays are electro-mechanical switches that have coil and two types of contacts that is NO & NC. But a Programmable Logic Controller, PLC is a mini computer which can take decision based on the programme and its input & output. Thus a PLC can perform many functions with the same ...
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Generally earth faults are Single Line to Ground (SLG) and Line-Line to Ground (LLG) faults. Earth faults are characterized by the presence of Zero Sequence Curren I0. Since, except for unbalance, normal system operation is not having Zero Sequence Current I0, much more sensitive pick-up is possible for earth fault ...
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