function will, with a delay for example 10 s, detect the situation when the generatoris not connected to the grid (standstill) and activate the overcurrent function. Theovervoltage function will detect the situation when the generator is taken intooperation and will disable the overcurrent function. The overcurrent function willhave a pick-up value about 50% of the rated current of the generator. The trip delaywill be about 50 ms.6.1.3 Setting guidelines IP15009-1 v2GUID-F7AA2194-4D1C-4475-8853-C7D064912614 v4When inverse time overcurrent characteristic is selected, theoperate time of the stage will be the sum of the inverse time delayand the set definite time delay. Thus, if only the inverse time delayis required, it is important to set the definite time delay for thatstage to zero.M13088-237 v3The parameters for the general current and voltage protection function (CVGAPC)are set via the local HMI or Protection and Control Manager (PCM600).The overcurrent steps has a IMinx (x=1 or 2 depending on step)setting to set the minimum operate current. Set IMinx belowStartCurr_OCx for every step to achieve ANSI reset characteristicaccording to standard. If IMinx is set above StartCurr_OCx for anystep the ANSI reset works as if current is zero when current dropsbelow IMinx.6.1.3.1 Directional negative sequence overcurrent protection M13088-3 v5Directional negative sequence overcurrent protection is typically used as sensitiveearth-fault protection of power lines where incorrect zero sequence polarizationmay result from mutual induction between two or more parallel lines. Additionally,it can be used in applications on underground cables where zero-sequenceimpedance depends on the fault current return paths, but the cable negative-sequence impedance is practically constant. It shall be noted that directionalnegative sequence OC element offers protection against all unbalance faults(phase-to-phase faults as well). Care shall be taken that the minimum pickup ofsuch protection function shall be set above natural system unbalance level.An example will be given, how sensitive-earth-fault protection for power lines canbe achieved by using negative-sequence directional overcurrent protectionelements within a CVGAPC function.This functionality can be achieved by using one CVGAPC function. The followingshall be done to ensure proper operation of the function:1MRK 511 423-UEN A Section 6Multipurpose protectionBay control REC650 2.2 IEC 79Application manual
