ABB SRW Instruction Leaflet

ABB SRW Instruction Leaflet Manual pdf 1 page image

ABB Power T&D Company Inc.Power Automation and Protection DivisionCoral Springs, FL 33065Instruction LeafletAll possible contingencies which may arise during installation, operation or maintenance, and all details andvariations of this equipment do not purport to be covered by these instructions. If further information isdesired by purchaser regarding this particular installation, operation or maintenance of this equipment, thelocal ABB Power T&D Company Inc. representative should be contacted.Printed in U.S.A.41-252ASRWReverse Power Relaywith Adjustable TimerSupersedes I.L. 41-252. Dated April 1987( | ) Denotes Change Since Last Issue! CAUTIONIt is recommended that the user becomeacquainted with the information in this instruc-tion leaflet before energizing the equipment. Fail-ure to observe this precaution may result indamage to the equipment.1. APPLICATIONThe type SRW relay is a single phase directionallycontrolled timing relay used to protect ac generatorsfrom motoring. When such a condition occurs andpersists for a predetermined time interval, the gener-ator may be tripped or an alarm sounded. The SRWmay also be used to sense lagging power factor loadflow in an abnormal direction as shown inFigure 8.The directional unit has 30 degree maximum sensitiv-ity characteristics. The timer unit is adjustable from 2to 21.5 seconds, .2 to 2 seconds or 2 to 63 secondsdepending upon relay style. The range of the currentpickup settings is from 1 mA to 40 mA at the maxi-mum sensitivity angle.2. CONSTRUCTIONThe SRW relay consists of three printed circuit mod-ules and a front panel packaged in a FT-11 case. Fordetailed information on the flexitest case, refer to I.L.41-076.The photograph inFigure 1 shows the SRW relay inits case.2.1. Interface ModuleThe interface module, mounted at the bottom of therelay, contains a voltage transformer, a current trans-former, a reed relay and two miniature high powerrelays. This module also contains a dc power supplyand its dropping resistors.(1) DC Power Supply — Three dc input voltages,48, 125 and 250 volts, can be selected by con-necting a jumper to a suitable position which isprinted on the PC board’s left-hand side. Therelay is shipped with a setting of 125 volts.(2) Voltage Transformer — This transformer con-sists of one primary winding and one second-ary winding. The continuous voltage rating atprimary side is 150% of the rated line voltagebut the relay’s accuracy is designed between30% and 110%. The secondary voltage is fedto the SRW module as a phase angle refer-ence.(3) Current Transformer — this is a two-windingtransformer with a turns ratio of 20 to 400. Aload resistor of 20 ohms is connected acrossthe secondary winding. The secondary voltageis linearly proportional to the primary current ifthe input current is less than 5 amps. For cur-rent higher than 5 amps, the secondary volt-age is clamped to approximately peak-to-peakvoltage of 20 volts in order to void ct satura-tion.(4) Trip Relays — Two miniature high powerrelays are connected to the trip circuit. Eachrelay is equipped with a normally open contactEffective: December 1996