8.6 Case studies: busbar layouts8.6.1 Busbar with just two bays GUID-A322EEC3-FA60-4348-A484-B80D797A2ABA v1Bay 2BusbarI BBay 1I B12000134-IEC18000280-1-en.vsdIEC18000280 V1 EN-USFigure 26: Busbar with two baysAssuming a fault on the CT secondary of bay 1 or 2 (CT open or short-circuit), false tripping canbe prevented by settings that satisfy the inequality IKmin > IB.8.6.2 Busbar with several bays GUID-9F16091E-4456-492A-B652-B0C17FA684AB v1Bay 2 Bay 3BusbarI B1 = 2 kABay 1(infeed)I B2 = 1.7 kA I B3 = 0.3 kA12000135-IEC18000281-1-en.vsdIEC18000281 V1 EN-USFigure 27: Busbar with three bays8.6.2.1 Case a: CT circuit fault on Bay 1 GUID-F53F7BC0-9440-495B-A700-F85EE7AAF4E4 v2The CT circuit fault simulates a fault on the busbars with a currentΔI = IB2 + IB3 = 2 kA. Falsetripping can be avoided by settingIKmin > 2 kA, for example, the next higher setting 2.1 kA.8.6.2.2 Case b: CT circuit fault on Bay 2 GUID-A1C8858B-11D5-4694-9EDC-6DEED0A66F6A v1The CT circuit fault in this case simulates a fault on the busbars with a fault currentΔI =IB2 − IB3= 1.7 kA andk becomes:1 31 31.7 kA 0.742.0 kAB BB BI IIk I I I IECEQUATION18094 V1 EN-US (Equation 20)False tripping can thus be avoided by settingIKmin> 1.7kA and/ork > 0.74.8.6.2.3 Case c: CT circuit fault on Bay 3 GUID-B5016D5C-8CD2-4E33-9FD7-E12DCA536C4B v1This case corresponds to the previous case, but the values forΔI andk are lower:Section 8 1MRK 505 399-UEN BBusbar protection48 Distributed busbar protection REB500Application manual© Copyright 2019 ABB. All rights reserved
