5-266 L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUALGROUPED ELEMENTS CHAPTER 5: SETTINGS5Igd = abs(3 × 0.0333 + 0.05) = 0.15 pu, IR0 = abs(3 × 0.033 – (0.05)) = 0.05 pu, IR2 = 3 × 0.033 = 0.10 pu,IR1 = 1.033 / 8 = 0.1292 pu, and Igr = 0.1292 puDespite very low fault current level, the differential current is above 100% of the restraining current.Example 5: Internal low-current, high-load single-line-to-ground fault with no feed from the groundGiven the following inputs: IA = 1.10 pu ∠0°, IB = 1.0 pu ∠–120°, IC = 1.0 pu ∠120°, and IG = 0.0 pu ∠0°The relay calculates the following values:I_0 = 0.033 pu ∠0°, I_2 = 0.033 pu ∠0°, and I_1 = 1.033 pu ∠0°Igd = abs(3 × 0.0333 + 0.0) = 0.10 pu, IR0 = abs(3 × 0.033 – (0.0)) = 0.10 pu, IR2 = 3 × 0.033 = 0.10 pu,IR1 = 1.033 / 8 = 0.1292 pu, and Igr = 0.1292 puDespite very low fault current level the differential current is above 75% of the restraining current.Example 6: Internal high-current single-line-to-ground fault with no feed from the groundGiven the following inputs: IA = 10 pu ∠0°, IB = 0 pu, IC = 0 pu, and IG = 0 puThe relay calculates the following values:I_0 = 3.3 pu ∠0°, I_2 = 3.3 pu ∠0°, and I_1 = 3.3 pu ∠0°Igd = abs(3 × 3.3 + 0.0) = 10 pu, IR0 = abs(3 × 3.3 – (0.0)) = 10 pu, IR2 = 3 × 3.3 = 10 pu, IR1 = 3 × (3.33 – 3.33) = 0 pu, andIgr = 10 puThe differential current is 100% of the restraining current.5.7.12 Negative sequence current5.7.12.1 MenuSETTINGS GROUPED ELEMENTS SETTING GROUP 1(6) NEGATIVE SEQUENCE CURRENTThe L90 provides two negative-sequence time overcurrent elements, two negative-sequence instantaneous overcurrentelements, and two negative-sequence directional overcurrent elements. For information on the negative sequence timeovercurrent curves, see the Inverse TOC Curve Characteristics section earlier.5.7.12.2 Negative sequence time overcurrent (ANSI 51Q, IEC PTOC)SETTINGS GROUPED ELEMENTS SETTING GROUP 1(6) NEGATIVE SEQUENCE CURRENT NEG SEQ TOC1(2) NEGATIVE SEQUENCE CURRENT NEG SEQ TOC1See below NEG SEQ TOC2 NEG SEQ IOC1See page 5-267 NEG SEQ IOC2 NEG SEQ DIR OC1See page 5-268 NEG SEQ DIR OC2 NEG SEQ TOC1 NEG SEQ TOC1FUNCTION: DisabledRange: Disabled, Enabled
