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7–6
489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 7: TESTING
7.2.4
Neutral Voltage (Fundamental) Accuracy
The specification for neutral voltage (fundamental) accuracy is
±
0.5% of full scale (100 V).
Perform the steps below to verify accuracy.
Z
In the
S2 SYSTEM SETUP
ZV
VOLTAGE SENSING
menu, set:
NEUTRAL VOLTAGE TRANSFORMER:
“Yes”
NEUTRAL V.T. RATIO:
“10.00:1”
Z
In the
S2 SYSTEM SETUP
ZV
GEN. PARAMETERS
menu, set:
GENERATOR NOMINAL FREQUENCY:
“60 Hz”
Measured values should be
±
5.0 V.
Z
Apply the voltage values shown in the table and verify accuracy of the
measured values.
Z
View the measured values in the
A2 METERING DATA
ZV
VOLTAGE
METERING
menu.
7.2.5
Negative Sequence Current Accuracy
The 489 measures negative sequence current as a percent of Full Load Amperes (FLA). A
sample calculation of negative sequence current is shown below. Given the following
generator parameters:
Rated MVA (
P
A
) = 1.04
Voltage Phase to Phase (
V
pp
): 600 V
We have:
(EQ 7.1)
With the following output currents:
(EQ 7.2)
The negative-sequence current Ins is calculated as:
Applied Neutral Voltage
at 60 Hz
Expected Neutral Voltage
Measured Neutral
Voltage
10 V
100 V
30 V
300 V
50 V
500 V
FLA
P
A
3
V
pp
×
----------------------
1.04 10
6
×
3 600
×
--------------------------
1000 A
=
=
=
I
a
780 0
°
,
I
b
∠
1000 113
°
lag,
I
c
∠
1000 247
°
lag
∠
=
=
=
Содержание Multilin 489
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