1.0. Introduction
Modern electric power system consists of several elements such as generators, transformers, station bus-bars, transmission lines and other associated equipments. These equipments in themselves are very costly. For power system operation, a high degree of reliability is required.
In order to protect the system (lines and equipment) from damage due to undue currents and/or abnormal voltages caused by faults (such as short circuits) the need for reliable protective devices arises.
Protection system is an extremely important part of the power system. Power System Protection deals with the protection of electrical power systems from faults through the isolation of faulted parts from the rest of the electrical network.
The objective of a power protection scheme is to detect the presence of faults and their locations and keep the power system stable by isolating only the components that are under fault, whilst leaving as much of the network as possible still in operation.
1.1. Components Of Protection Systems
Protection systems usually comprise five components:
- Current and voltage transformers to step down the high voltages and currents of the electrical power system to convenient levels for the relays to deal with.
- Relays to sense the fault and initiate a trip, or disconnection.
- Circuit breakers to open/close the system based on relay and auto-closer commands.
- Batteries to provide power in case of power disconnection in the system.
- Communication channels to allow analysis of current and voltage at remote terminals of a line and to allow remote tripping of equipment.
Failures may occur in each part, such as insulation failure, fallen or broken transmission lines, incorrect operation of circuit breakers, short circuits and open circuits. Thus, protection devices are installed with the aim of protection of assets, and to ensure continued supply of energy.
While the operating quality of these devices, and especially of the protective relays, is always critical, different strategies are considered for protecting the different parts of the power system. Very important equipment may have completely redundant and independent protective systems, while a minor branch distribution line may have very simple low-cost protection. Thus, protection schemes must apply a very pragmatic and pessimistic approach to clearing system faults. This is the main thrust of this work.
This material contains electrical diagrams, circuits, illustrations and more (Very detailed)
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