9.1.3 Setting guidelines IP14979-1 v1M12915-4 v9The parameters for instantaneous phase overcurrent protection PHPIOC are set viathe local HMI or PCM600.This protection function must operate only in a selective way. So check all systemand transient conditions that could cause its unwanted operation.Only detailed network studies can determine the operating conditions under whichthe highest possible fault current is expected on the line. In most cases, this currentappears during three-phase fault conditions. But also examine single-phase-to-earthand two-phase-to-earth conditions.Also study transients that could cause a high increase of the line current for shorttimes. A typical example is a transmission line with a power transformer at theremote end, which can cause high inrush current when connected to the networkand can thus also cause the operation of the built-in, instantaneous, overcurrentprotection.Common base IED values for primary current (IBase), primary voltage (UBase)and primary power (SBase) are set in the global base values for settings functionGBASVAL.GlobalBaseSel: This is used to select GBASVAL function for reference of basevalues.Operation: Set the protection to On/Off.OpMode: This parameter can be set to 2 out of 3 or 1 out of 3. The setting controlsthe minimum number of phase currents that must be larger than the set operatecurrent IP>> for operation. Normally this parameter is set to 1 out of 3and willthus detect all fault types. If the protection is to be used mainly for multi phasefaults, 2 out of 3 should be chosen.IP>>: Set operate current in % of IB.IP>>Max and IP>>Min should only be changed if remote setting of operationcurrent level, IP>>, is used. The limits are used for decreasing the used range ofthe IP>> setting. If IP>> is set outside IP>>Max and IP>>Min, the closest of thelimits to IP>> is used by the function. If IP>>Max is smaller than IP>>Min, thelimits are swapped.StValMult: The set operate current can be changed by activation of the binary inputENMULT to the set factor StValMult.9.1.3.1 Meshed network without parallel line M12915-9 v8The following fault calculations have to be done for three-phase, single-phase-to-earth and two-phase-to-earth faults. With reference to Figure 249, apply a fault in Band then calculate the current through-fault phase current IfB. The calculationSection 9 1MRK 506 369-UEN BCurrent protection456 Line distance protection REL670 2.2 IECApplication manual
