2-34 L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
SPECIFICATIONS CHAPTER 2: PRODUCT DESCRIPTION
2
87LG operate time: 1.5 to 2.5 cycles
LINE CURRENT DIFFERENTIAL TRIP LOGIC
87L trip: Adds security for trip decision; creates 1 and 3 pole trip logic
DTT: Engaged Direct Transfer Trip (1 and 3 pole) from remote L90
DD: Sensitive Disturbance Detector to detect fault occurrence
Stub bus protection: Security for ring bus and 1½ breaker configurations
Open pole detector: Security for sequential and evolving faults
RESTRICTED GROUND FAULT
Pickup: 0.005 to 30.000 pu in steps of 0.001
Dropout: 97 to 98% of pickup
Slope: 0 to 100% in steps of 1%
Level accuracy:
0.1 to 2.0 x CT rating: ±0.5% of reading or ±1% of rated (whichever is greater)
>2.0 x CT rating ±1.5% of reading
Pickup delay: 0 to 600.00 s in steps of 0.01
Dropout delay: 0 to 600.00 s in steps of 0.01
Operate time: <1 power system cycle
PHASE/NEUTRAL/GROUND TOC
Current: Phasor or RMS
Pickup level: 0.020 to 30.000 pu in steps of 0.001
Dropout level: 97% to 98% of pickup
Level accuracy:
0.1 to 2.0 × CT: ±0.5% of reading or ±0.4% of rated (whichever is greater)
> 2.0 × CT: ±1.5% of reading > 2.0 × CT rating
Curve shapes: IEEE Moderately/Very/Extremely Inverse; IEC (and BS) A/B/C and Short Inverse; GE IAC Inverse,
Short/Very/ Extremely Inverse; I
2
t; FlexCurvesâ„¢ (programmable); Definite Time (0.01 s base
curve)
Curve multiplier: Time Dial = 0.00 to 600.00 in steps of 0.01
Reset type: Instantaneous/Timed (per IEEE)
Curve timing accuracy at 1.03 to 20 x pickup:
±3.5% of operate time or ±½ cycle (whichever is greater) from pickup to operate
Voltage restraint: Modifies pickup current for voltage in the range of 0.1 < V < 0.9 VT Nominal in a fixed linear rela-
tionship
PHASE/NEUTRAL/GROUND IOC
Pickup level: 0.020 to 30.000 pu in steps of 0.001
Dropout level: 97 to 98% of pickup
Level accuracy:
0.1 to 2.0 × CT rating: ±0.5% of reading or ±0.4% of rated (whichever is greater)
> 2.0 × CT rating: ±1.5% of reading
Overreach: <2%
Pickup delay: 0.00 to 600.00 s in steps of 0.01
Reset delay: 0.00 to 600.00 s in steps of 0.01
Operate time: <16 ms at 3 × pickup at 60 Hz (Phase/Ground IOC)
<20 ms at 3 × pickup at 60 Hz (Neutral IOC)
Timer accuracy: ±3% of operate time or ±1/4 cycle (whichever is greater)
NEGATIVE SEQUENCE TOC
Current: Phasor
Pickup level: 0.020 to 30.000 pu in steps of 0.001
Dropout level: 97% to 98% of pickup
Level accuracy: ±0.5% of reading or ±0.4% of rated (whichever is greater)
from 0.1 to 2.0 x CT rating
±1.5% of reading > 2.0 x CT rating
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