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PROTECTIVE RELAYING INFORMATION SITE




Site Details
Current Rank: 43 (Technology & Computers)
URL: http://powersystemprotectiverelaying.blogspot.com/
Site Description: your power system's relaying information source
Date Joined: Nov 30, 2012


Latest Blog Posts

REMOTE TRIPPING OF CIRCUIT BREAKERS BASICS
on Dec 21, 2012 in Protection How to trip circuit breakers remotely?  Circuit breakersCircuit breakers directly actuated by a protective relay system are usually provided where it is desirable to isolate a faulted transformer with minimum effect on other segments o...



GENERATOR DISTANCE TYPE BACK UP BASICS
on Dec 21, 2012 in Protection Generator One zone of distance relaying with a mho characteristic is commonly used for system phase-fault backup. These relays are usually connected to receive currents from current transformers in the neutral ends of the generator phase windings and...



POWER TRANSFORMER FAULT CLEARING
on Dec 21, 2012 in Protection Fault Current Transformer A faulted transformer can be separated from its power source by devices such as circuit breakers, power operated disconnect switches, circuit switchers, and fuses, or by remote tripping of fault-interrupting devices.In addition to separatin...



AUXILIARY CURRENT TRANSFORMERS USED FOR CIRCUIT PROTECTION
on Dec 21, 2012 in Protection Transformer Auxiliary cts are used for the following reasons:a) Circuit isolation to permit independent groundingb) Change in ratio to match current requirementsc) To produce a phase shift in a three phase circuitd) To reverse polaritye) To limit main ct fault b...



OVER EXCITATION PROTECTION FOR POWER TRANSFORMER BASICS AND TUTORIALS
on Dec 21, 2012 in Protection Transformer Overexcitation of a transformer can occur whenever the ratio of the per unit voltage to per unit frequency (V/Hz) at the secondary terminals of a transformer exceeds its rating of 1.05 per unit (PU) on transformer base at full load, 0.8 pow...



TRANSMISSION LINE PROTECTION LENGTH CONSIDERATIONS BASICS
on Dec 17, 2012 in Transmission Lines Distance Relay Fault Current Short lines (SIRs > 4)Typical protection schemes and communication channels used are as follows:— Current differential (FO, PW, AT, MW)— Phase comparison (FO, PW, AT, PLC, MW, R)— POTT (FO, PW, AT, PLC, MW, R)— Directional comparison block...



DIRECTIONAL COMPARISON BUS RELAYING
on Dec 17, 2012 in Differential Relay Occasionally, it is desirable to add bus protection to an older substation where additional current transformers and control cable are too costly to install. In this instance, the existing current transformer circuits used for line relaying ...



MTBF DEFINITION AND BASIC INFORMATION
on Dec 16, 2012 in Relay WHAT IS MTBF?MTBF is used in calculating reliability. It is an acronym for mean time between failures (MTBF).Most manufacturers calculate the reliability of their systems in the same manner that is prescribed for military products. The process involv...



TRANSFORMER PHASE TIME OVERCURRENT RELAY PROTECTION
on Dec 13, 2012 in Relay Transformer Overcurrent Time overcurrent relays are inexpensive, simple, and reliable protective devices. Since sensitive settings and fast operation are usually not possible with overcurrent relays, they will provide limited protection for internal transformer fa...



GROUNDING TRANSFORMER DIFFERENTIAL RELAYING
on Dec 11, 2012 in Differential Relay Transformer ConfigurationTo establish a grounded system, a grounding transformer is frequently tapped on the low-side leads of the supply transformer and is thereby included in the transformer differential zone.ProblemZero sequence current supplied by the g...



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