5-238 L30 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUALGROUPED ELEMENTS CHAPTER 5: SETTINGS5The negative-sequence time overcurrent element can be used to determine and clear unbalance in the system. The inputfor calculating negative-sequence current is the fundamental phasor value.Two methods of resetting operation are available; “Timed” and “Instantaneous” (see the Inverse TOC Curve Characteristicssection earlier for details on curve setup, trip times and reset operation). When the element is blocked, the timeaccumulator resets according to the reset characteristic. For example, if the element reset characteristic is set to“Instantaneous” and the element is blocked, the time accumulator clears immediately.Figure 5-120: Negative sequence TOC1 logic5.7.7.3 Negative sequence instantaneous overcurrent (ANSI 50Q, IEC PIOC)SETTINGS GROUPED ELEMENTS SETTING GROUP 1(6) NEGATIVE SEQUENCE CURRENT NEG SEQ OC1(2)The negative-sequence instantaneous overcurrent element can be used as an instantaneous function with no intentionaldelay or as a definite time function. The element responds to the negative-sequence current fundamental frequencyphasor magnitude (calculated from the phase currents) and applies a positive-sequence restraint for better performance:a small portion (12.5%) of the positive-sequence current magnitude is subtracted from the negative-sequence currentmagnitude when forming the operating quantity.I op = |I_2| - K x |I_1| where K = 1/8 Eq. 5-25 NEG SEQ IOC1 NEG SEQ IOC1FUNCTION: DisabledRange: Disabled, Enabled NEG SEQ IOC1 SIGNALSOURCE: SRC 1Range: SRC 1, SRC 2 NEG SEQ IOC1PICKUP: 1.000 puRange: 0.020 to 30.000 pu in steps of 0.001 NEG SEQ IOC1 PICKUPDELAY: 0.00 sRange: 0.00 to 600.00 s in steps of 0.01 NEG SEQ IOC1 RESETDELAY: 0.00 sRange: 0.00 to 600.00 s in steps of 0.01 NEG SEQ IOC1 BLOCK:OffRange: FlexLogic operand NEG SEQ IOC1TARGET: Self-resetRange: Self-reset, Latched, Disabled NEG SEQ IOC1EVENTS: DisabledRange: Disabled, Enabled
