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INJECTED
CURRENT 1A
UNIT, APPLIED
VOLTAGE (Ia is the
reference vector)
Ia = 1 A ∠0°
Ib = 1 A ∠120°
Ic = 1 A ∠240°
Va = 120 V ∠342°
Vb = 120 V ∠102°
Vc = 120 V ∠222°
Ia = 1 A ∠0°
Ib = 1 A ∠120°
Ic = 1 A ∠240°
Va = 120 V ∠288°
Vb = 120 V ∠48°
Vc = 120 V ∠168°
7.3.3
Unbalance Test
7–12
S2 SYSTEM SETUP
CURRENT SENSING
S2 SYSTEM SETUP
VOLTAGE SENSING
S2 SYSTEM SETUP
VOLTAGE SENSING
Inject current and apply voltage as per the table below.
Verify accuracy of the measured values.
View the measured values in:
A2 METERING DATA
INJECTED
EXPECTE
CURRENT 5A
UNIT, APPLIED
VOLTAGE (Ia is the
reference vector)
QUANTIT
Ia = 5 A ∠0°
Ib = 5 A ∠120°
Ic = 5 A ∠240°
+ 3424 kW
Ia = 120 V ∠342°
Vb = 120 V ∠102°
Vc = 120 V ∠222°
Ia = 5 A ∠0°
Ib = 5 A ∠120°
Ic = 5 A ∠240°
+ 3424
Va = 120 V ∠288°
kvar
Vb = 120 V ∠48°
Vc = 120 V ∠168°
The 469 measures the ratio of negative sequence current (I
(I
). This value as a percent is used as the unbalance level when motor load exceeds FLA.
1
When the average phase current is below FLA, the unbalance value is de-rated to prevent
nuisance tripping as positive sequence current is much smaller and negative sequence
current remains relatively constant. The derating formula is:
POWER SYSTEM
CONVENTION
Ic=1000A
@ 247°
FIGURE 7–2: Three Phase Example for Unbalance Calculation
Symmetrical component analysis of vectors using the mathematical vector convention
yields a ratio of negative sequence current to positive sequence current as shown:
PHASE CT PRIMARY:
VT CONNECTION TYPE:
VOLTAGE TRANSFORMER RATIO:
POWER METERING
TOLERAN
D LEVEL
CE RANGE
OF
OF POWER
POWER
QUANTITY
Y
3329
to
3519
kW
3329
to
3519
kvar
I
I
2
avg
--- -
×
-------- -
×
100%
I
FLA
1
VECTOR
Ia=780A
@ 0°
Ib=1000A
@ 113°
469 MOTOR MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 7: TESTING
"1000"
"Wye"
.
MEASURE
EXPECT
MEASURE
D POWER
ED
D POWER
QUANTIT
POWER
Y
FACTOR
0.95 lag
0.31 lag
) to positive sequence current
2
MATHEMATICAL
VECTOR
CONVENTION
Ic=1000A
@ 113°
Ia=780A
@ 0°
Ib=1000A
@ -113°
"10.00:1"
FACTOR
(EQ 7.1)
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