Section 4 1MAC309294-MB FProtection functions172 RER620Technical Manual4.1.6 Negative phase-sequence current protection 464.1.6.1 Identification4.1.6.2 Function blockFigure 76: Function block4.1.6.3 FunctionalityThe negative sequence current protection 46 is used for increasing sensitivity to detectsingle phasing situations, unbalanced loads due to, for example, unsymmetrical feedervoltages.The function is based on the measurement of the negative sequence current. In a faultsituation, the function picks up when the negative sequence current exceeds the set limit.The trip time characteristics can be selected to be either definite time (DT) or inversedefinite minimum time (IDMT). In the DT mode, the function trips after a predefined triptime and resets when the fault current disappears. The IDMT mode provides currentdependent timer characteristics.The function contains a blocking functionality. It is possible to block function outputs,timers, or the function itself, if desired.4.1.6.4 Operation principleThe function can be enabled and disabled with the Operation setting. The correspondingparameter values are Enable and Disable.The operation of negative phase-sequence current protection can be described by using amodule diagram. All the blocks in the diagram are explained in the next sections.Function description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberNegative sequence current protection NSPTOC I2> 4646 can also be used for detecting broken conductors.
