Modern Design Principles for Numerical Busbar Differential Protection Zoran Gajić, Hamdy Faramawy, Li He, Klas Mike Kockott Koppari, Lee Max ABB Inc. ABB AB Raleigh, NC, USA Västerås, Sweden
[email protected] Summary 6. Easy incorporation of bus-section and/or bus-coupler bays (that is, tie-breakers) with one or two sets of CTs into the For busbar protection, it is extremely important to have protection scheme. good security since an unwanted operation might have severe consequences. The unwanted operation of the bus differential 7. Disconnector and/or circuit breaker status supervision. relay will have the similar effect as simultaneous faults on all power system elements connected to the bus. On the other hand, the relay has to be dependable as well. Failure to operate Modern design for a Busbar Differential Protection IED or even slow operation of the differential relay, in case of an [10] containing six differential protection zones and fulfilling actual internal fault, can have fatal consequences. These two all of the above mentioned requirements will be presented in requirements are contradictory to each other. To design the the paper. differential relay to satisfy both requirements at the same time is not an easy task. Keywords Busbar protection shall also be able to dynamically Busbar Protection, Differential Protection, Dynamic Zone include and/or exclude individual bay currents from Selection. differential zones. Therefore it must contain so-called dynamic zone selection in order to adapt to changing topology of substation for multi-zone applications. The software based I INTRODUCTION dynamic zone selection ensures: 1. Dynamic linking of measured bay currents to the The bus zone protection has experienced several decades appropriate differential protection zone(s) as required by of changes.