Required fields are marked *. This discrimination between faults and over-currents may either be an inherent characteristic of the relay or may be achieved by connecting auxiliary devices like the minimum voltage relay. Duplication of tripping batteries and of circuit breaker tripping coils may be provided. The backup protection is essential for the proper working of the electrical system. AUTHORS The stored program in digital computer determines the correct switching operation as regard severity of faults, system stability etc. The primary protection is the first line of defense and is responsible to protect all the power system elements from all the types of faults. The backup protection is essential for the proper working of the electrical system. Protection must be sufficiently sensitive to operate reliably under minimum fault conditions for a fault within its own zone while remaining stable under maximum load or through fault conditions. You have entered an incorrect email address! What is Arc Chute? Example:  Restricted Earth Fault, Differential protection etc. This means first of all to clear the fault automatically if at all possible, even though this requires disconnection of a considerable portion of the Protection Systems. The Protection Systems is divided into protective zones as explained earlier, each having its protective relays for determining the existence of a fault in that zone and having circuit breakers for disconnecting that zone from the system. Reliability is a qualitative term. The backup protection is mainly used where the main protection of the adjacent circuit is unable to backup the main protection of the given circuit. Primary and Back-up Protection. loose contact or insufficient contact to reach the trip circuit. The backup protection provides the back up to the main protection whenever it fails in operation or its cut out for repairs. Primary and Backup Protection: The Protection Systems is divided into protective zones as explained earlier, each having its protective relays for determining the existence of a fault in that zone and having … can fail due to failure of one of the components in the protective system such as a relay, auxiliary relay. Failure is not confined to protective gear but may also be due to breaker defects. On the other hand relays should not be made extremely fast, i.e. The backup protection is the second line of defense which isolates the faulty section of the system in case the main protection fails to function properly. The main protection is provided in each section of an electrical installation. is given against short-circuit protection and generally not for other abnormal conditions. The backup protection provides the back up to the main protection whenever it fails in operation or its cut out for repairs. Protection systems in successive zones are arranged to operate in times that are graded through the sequence of equipment so that upon the occurrence of a fault, although a number of protection equipment respond, only those relevant to the faulty zone complete the tripping function. A station battery usually provides the circuit breaker trip current. Trip circuits should be continuously supervised. The main protection or primary protection is the first line protection which provides quick-acting and selective clearing of a fault within the boundary of the circuit section or element it protects. The current is measured at various points along the current path, e.g., at source, intermediate locations, consumer end..The tripping time at these locations are graded in such a way that the circuit-breaker/fuse nearest the faulty part operate first, giving primary protection. The system having central control can be provided with centrally controlled back-up. The backup protection comes into play only when the primary protection fails. The protection provided by the protective relaying equipment can be categorized into two types as: The primary protection is the first line of defense and is responsible to protect all the power system elements from all the types of faults. In interconnected systems, there will be power swings, which should also be ignored by the relay. The following compromises are typical: a) Separate current transformers(cores and secondary windings only) are provided. Relays backup protection: Single circuit breaker is used to for both primary and backup relays. D.C. tripping voltage supply-absence of DC tripping voltage. COPYRIGHT © 2014 TO 2020 EEEGUIDE.COM ALL RIGHTS RESERVED, Essential Qualities of Protection Systems, Earth Fault Protection or Leakage Protection, Hardware Systems Versus Microprocessor Control, Comparison of Various Systems of Transmission, Power Frequency Overvoltages in Power Systems, Switching Systems in Digital Communication, Directional Overcurrent Relays in Power Systems, Design of Current Carrying Capacity Systems, Circulating Current Scheme for Transformer Protection, Power System Protection Important Questions, Symmetrical T Network in Network Analysis, Voltage Source Inverter Fed Synchronous Motor Drive, Condition for Reciprocity of a Two Port Network, Half Subtractor and Full Subtractor Circuit. 2.Dakshata U. Kamble. -Centrally coordinated back-up: Here system is having central control and it can be provided with centrally controlled back-up. Examples of the former are differential protection and frame leakage protection, and of the latter current time graded protection and distance protection. The backup protection provides the back up to the main protection whenever it fails in operation or its cut out for repairs. Primary and Backup Protection Working Principle, Rate Of Change Of Frequency (ROCOF) Protection df/dt Working Principle, 7 Purpose of NGR Neutral Grounding Resistor Transformer & Generator, Summation Current Transformer Calculations, Electrical Panel & Types of Electrical Panels used In Industry, Plug Setting Multiplier & Time Setting Multiplier, What is Type 2 coordination & Type 1 Coordination, Transformer Fault Current Calculator With Calculation Formula, CT Ratio Calculator & CT Ratio Calculation Formula.

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