1. I3P, input used for “Operating Quantity”.2. U3P, input used for “Voltage Polarizing Quantity”.3. I3PPOL, input used for “Current Polarizing Quantity”.4. I3PDIR, input used for “Operating Directional Quantity”.These inputs are connected from the corresponding pre-processing function blocks inthe Configuration Tool within PCM600.8.2.7.1 Operating quantity within the functionIf the function is set to measure zero sequence, it uses Residual Current (3I0) for itsoperating quantity. The residual current can be:1. directly measured (when a dedicated CT input of the IED is connected inPCM600 to the fourth analog input of the pre-processing block connected toEF4PTOC function input I3P). This dedicated IED CT input can be for example,connected to:• parallel connection of current instrument transformers in all three phases(Holm-Green connection).• one single core balance, current instrument transformer (cable CT).• one single current instrument transformer located between power systemstar point and earth (that is, current transformer located in the star point of astar connected transformer winding).• one single current instrument transformer located between two parts of aprotected object (that is, current transformer located between two starpoints of double star shunt capacitor bank).2. calculated from three-phase current input within the IED (when the fourth analoginput into the pre-processing block connected to EF4PTOC function AnalogInput I3P is not connected to a dedicated CT input of the IED in PCM600). In suchcase the pre-processing block will calculate 3I0 from the first three inputs into thepre-processing block by using the following formula (will take I2 from sameSMAI AI3P connected to I3PDIR input (same SMAI AI3P connected to I3Pinput)):If zero sequence current is selected,Iop 3I IL1 IL2 IL30= = + +EQUATION1874 V2 EN (Equation 47)where:IL1, IL2 and IL3 are fundamental frequency phasors of three individual phase currents.The residual current is pre-processed by a discrete Fourier filter. Thus the phasor ofthe fundamental frequency component of the residual current is derived. The phasormagnitude is used within the EF4PTOC protection to compare it with the set operationcurrent value of the four steps (IN1>, IN2>, IN3> or IN4>). If the residual current isSection 8 1MRK 502 048-UEN ACurrent protection192Technical manual
