ABB REL-300 Instruction Leaflet

Also see for REL-300: Instruction manual Instruction manual

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ABB REL-300 Instruction Leaflet Manual pdf 50 page image

I.L. 40-385.1B(5/92) 3-5ed within 150 ms after LOP has been set up. Thislogic has no effect on the conditions:• if ∆I signal occurs ahead of LOP, or• if LOP and ∆I signals occur simultaneouslyNOTE: The LOPB setting detects a blown fusecondition.The distance units are designed to beblocked under the loss-of-potential con-dition, but the high set (ITP and ITG) andground backup (GB) are functional andconverted to non-directional automati-cally (see also 3.4.6).3.4.4 Loss of Current Monitoring (LOI)The ac current monitoring circuit uses IoM (and notVo) as criterion, as shown in Figure 3-12. Under ctshort circuit or open circuit condition, IoM (and notVo) satisfies AND-23; the output signal of AND-23starts the 500/500 ms timer. The timer output turns“ON” the non-memory LOI indicator, which is shownin the Metering mode, and drops out the AL1 relay(Failure Alarm). If the LOI condition exists and LOIBis set at YES, the trip will be blocked after the 500 mstimer times out.3.4.5 Overcurrent SupervisionFor MDAR, as shown in Figure 3-13, the distanceunits do not require overcurrent supervision; be-cause the relay normally operates in a backgroundmode, they will not start the Zone 1 and pilot imped-ance computation until a phase current or a phasevoltage disturbance is detected. This approach canminimize the load problem when setting the phaseovercurrent units. However, the 3-phase units aresupervised by the load restriction logic, and the 21BIunit is restricted by the setting of IL units, conse-quently, the 3-phase units are supervised by the ILsetting. For increasing the security. The applicationof LOPB supervision function is also normally rec-ommended.For coordination purposes the ground trip units(Z1G, Z2G, Z3G, PLTG, and FDOG) are supervisedby the medium set ground overcurrent unit (IoM).The Ios setting and RDOG are used for carrier sendin a Pilot Blocking system.3.4.6 Instantaneous Forward Directional Over-current Trip/Highset Trip LogicThe instantaneous overcurrent units (IAH, IBH, ICHand IOH) are normally set forward directional andhigh to detect those faults which occur in the Zone 1area, therefore, their tripping will occur via OR-2 forHST, as shown in Figure 3-14. These high set tripfunctions can be disabled by setting the ITP (phase)and/or ITG (ground) to the OUT position. The direc-tional unit (ITP and ITG) will be automatically con-verted to non-directional protection if the LOPcondition occurs and the setting of LOPB = YES.3.4.7 Close-Into-Fault Trip (CIFT) andStub-Bus Protection (SBP)There are three low voltage units (LVA, LVB andLVC) in MDAR. Each unit senses the phase voltagecondition in the background mode. The unit can beset from 40 to 60 volts, in 1.0 volt steps. For anyphase voltage below its preset value, the LV logicwill produce a logic “1” output signal. The low voltageunits are used in CIFT and weakfeed logic in MDAR.In order to supplement distance unit operation, whenthe circuit breaker is closed into a fault and line sidepotential is used, the Close-Into-Fault Trip (CIFT)circuit operates as shown in Figure 3-15. It includeslogic AND-22, OR-3 and 100/180 ms and 16/0 mstimers. If any overcurrent unit (IAL, IBL, ICL or IOM)operates OR-11, at the same time as one of thephase voltages (VA, VB,VC) is below the preset lev-el of the LV units. Then logic AND-22 is satisfied andproduces a trip signal (for 180 ms) after circuit break-er closes (52b contact opens). Tripping will be viaOR-3, with RB and CIF targets.The stub bus protection feature protects a line termi-nal with the potential device on the line-side. Withthe line disconnect switch open, the distance unitswill lose their reference voltage, and may not func-tion correctly when a fault occurs on the short part ofthe bus between the ct location and the opened dis-connect switch. The logic for stub bus protection isindependent of the operation of the circuit breaker(s)and the line voltage condition. Also, it requires theinformation from the disconnect switch (89b). Thestub bus protection logic, as shown in Figure 3-15,includes the contact convertor for the 89b switch andAND-22E and OR-22B logic.