9.1.2.2 Base quantities for CVGAPC functionThe parameter settings for the base quantities, which represent the base (100%) forpickup levels of all measuring stages, shall be entered as setting parameters forevery CVGAPC function.Base current shall be entered as:1. rated phase current of the protected object in primary amperes, when themeasured Current Quantity is selected from 1 to 9, as shown in table 168.2. rated phase current of the protected object in primary amperes multiplied by√3 (1.732 · Iphase), when the measured Current Quantity is selected from 10to 15, as shown in table 168.Base voltage shall be entered as:1. rated phase-to-earth voltage of the protected object in primary kV, when themeasured Voltage Quantity is selected from 1 to 9, as shown in table 169.2. rated phase-to-phase voltage of the protected object in primary kV, when themeasured Voltage Quantity is selected from 10 to 15, as shown in table 169.9.1.2.3 Built-in overcurrent protection stepsTwo overcurrent protection steps are available. They are absolutely identical andtherefore only one will be explained here.Overcurrent step simply compares the magnitude of the measured current quantity(see table 168) with the set pickup level. Non-directional overcurrent step willpickup if the magnitude of the measured current quantity is bigger than this setlevel. Reset ratio is settable, with default value of 0.96. However depending onother enabled built-in features this overcurrent pickup might not cause theovercurrent step start signal. Start signal will only come if all of the enabled built-in features in the overcurrent step are fulfilled at the same time.Second harmonic featureThe overcurrent protection step can be restrained by a second harmonic componentin the measured current quantity (see table 168). However it shall be noted that thisfeature is not applicable when one of the following measured currents is selected:• PosSeq (positive sequence current)• NegSeq (negative sequence current)• UnbalancePh (unbalance phase current)• UnbalancePh-Ph (unbalance ph-ph current)This feature will simple prevent overcurrent step start if the second-to-firstharmonic ratio in the measured current exceeds the set level.Section 9 1MRK 505 208-UEN BMultipurpose protection272Technical reference manual
