IEEE C37.97-1979 pdf free.IEEE Guide for Protective Relay Applications to Power System Buses.
IEEE C37.97 has been prepared to assist the reader in the effective application of relays for protection of power systemelectrical buses. The bus protection described refers only to protection at the bus location, independent of equipmentat remote locations.Common bus arrangements and some special arrangements used in the United States are covered.Not all bus protection systems or all possible bus arrangements are included.
A bus is a critical element of a power system, as it is the point of convergence of many circuits — transmission,generation, or loads.The effect of a single bus fault is equivalent to many simultaneous faults and usually, due to theconcentration of supply circuits，involves high current magnitudes. High-speed bus protection is often provided tolimit the damaging effects on equipment or system stability or to maintain service to as much load as possible. Withoutbus protection, the remote terminals of lines connected to a faulted bus must be tripped. This will result in the loss ofload tapped to these lines. Inadequate bus protection can result in catastrophic failures and present serious personnelhazards.
Factors such as bus configuration, relay input sources, operating time, sensitivity, and existing facilities are importantin selecting the type of bus protection system. Existing stations may not have the required relay input sources for busprotection. Technical and economic considerations determine whether additional facilities are to be installed.If acommon scheme cannot be used, consideration may be given to special bus protection methods.
Several methods of bus protection are available. Probably the most sensitive method employs the differential principle,in which the phasor summation of all the measured current entering and leaving the bus must be zero unless there is afault within the protected zone. For a fault not in the protected zone the instantaneous direction of at least one currentis opposite to the others.
Other bus protection schemes such as partial differential, directional comparison, and the fault-bus methods use eitheror both the magnitude and direction of fault current and are described in Section 3.IEEE C37.97 pdf download.