7–12 489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 7: TESTING
7.3 Additional Functional Tests
7.3.1 Overload Curve Accuracy
The specification for overload curve timing accuracy is ±100 ms or ±2% of time to trip.
Pickup accuracy is as per the current inputs (±0.5% of 2 × CT when the injected current is
less than 2 × CT and ±1% of 20 × CT when the injected current is equal to or greater than
2 × CT). Perform the steps below to verify accuracy.
Z In the
S2 SYSTEM SETUP ZV GEN. PARAMETERS menu, set:
GENERATOR RATED MVA: “1.04”
GENERATOR VOLTAGE PHASE-PHASE: “600”
Note that setting GENERATOR VOLTAGE PHASE-PHASE to “600” is equivalent to setting
FLA = 1000 A. For testing purposes ONLY!
Z In the
S2 SYSTEM SETUP Z CURRENT SENSING menu, set:
PHASE CT PRIMARY: “1000”
Z In the S9 THERMAL MODEL Z MODEL SETUP menu, set:
SELECT CURVE STYLE: “Standard”
OVERLOAD PICKUP LEVEL: “1.10 x FLA”
UNBALANCE BIAS K FACTOR: “0”
HOT/COLD SAFE STALL RATIO: “1.00”
ENABLE RTD BIASING: “No”
STANDARD OVERLOAD CURVE NUMBER: “4”
ENABLE THERMAL MODEL: “Yes”
Z In the S9 THERMAL MODEL Z THERMAL ELEMENTS menu, set:
THERMAL MODEL TRIP: “Latched” or “Unlatched”
Any trip must be reset prior to each test. Short the emergency restart terminals
momentarily immediately prior to each overload curve test to ensure that the thermal
capacity used is zero. Failure to do so will result in shorter trip times. Inject the current of
the proper amplitude to obtain the values as shown and verify the trip times. Motor load
may be viewed in the
A2 METERING DATA Z CURRENT METERING menu.
The thermal capacity used and estimated time to trip may be viewed in the
A1 STATUS ZV
GENERATOR STATUS menu.
Note
(EQ 7.4)
Average Phase
Current
Displayed
Pickup Level Expected
Time to Trip
Tolerance Range Measured Time
to Trip (sec.)
1050 A 1.05 × FLA never n/a
1200 A 1.20 × FLA 795.44 s 779.53 to 811.35 s
1750 A 1.75 × FLA 169.66 s 166.27 to 173.05 s
3000 A 3.00 × FLA 43.73 s 42.86 to 44.60 s
6000 A 6.00 × FLA 9.99 s 9.79 to 10.19 s
10000 A 10.00 × FLA 5.55 s 5.44 to 5.66 s
FLA
Generator Rated MVA
3 Generator Phase-to-Phase Voltage×
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Courtesy of NationalSwitchgear.com
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