GE Power Quality Meter Series

4-40 PQM Power Quality Meter GE Power Management
4.5 S4 ALARMS/CONTROL 4 PROGRAMMING
4
•
VOLTAGE UNBALANCE DELAY:
If the voltage unbalance equals or exceeds the
VOLTAGE UNBALANCE
LEVEL
setpoint value and remains this way for the time delay programmed in this setpoint, a voltage unbal-
ance condition will occur.
•
VOLTAGE PHASE REVERSAL:
Under normal operating conditions, the PQM expects to see the voltages
connected with a 1-2-3 or A-B-C sequence. If the voltages are connected with the wrong sequence, 2-1-3
or B-A-C, a voltage phase reversal condition will occur. A minimum of 20 V must be applied to the PQM on
all voltage inputs before the phase reversal feature will operate.
A phase reversal condition is determined by looking at the phase angle at the occurrence of the peak sam-
ple of phase B voltage and subtracting it from the phase angle at the peak sample of phase A voltage
(phase A angle - phase B angle). This angle is averaged over several cycles before deciding on the condi-
tion to avoid any false triggering of the feature. Only two phases are required to detect phase reversal
because all phase reversal conditions can be covered without the use of the third phase. The angle to
detect phase reversal will vary depending on the connection being used as described below.
For 4-wire wye (3 VTs), 4-wire wye (2 VTs), 4-wire direct, and 3-wire direct connections, the phase reversal
function operates when the angle between phase A and B becomes
≤
–150° or
≥
–90° as shown below.
Figure 4–23: PHASE REVERSAL FOR 4-WIRE & 3-WIRE DIRECT CONNECTIONS
For the 3 WIRE DELTA (2 VTs) connection the phase reversal function operates when the angle between
phase A and B becomes
≤
30° or
≥
90° as shown below.
Figure 4–24: PHASE REVERSAL FOR 3-WIRE DELTA (2 VTs OPEN-DELTA) CONNECTION
When the SINGLE PHASE DIRECT connection is used the phase reversal feature will never operate.
•
VOLTAGE PHASE REVERSAL DELAY:
If a voltage phase reversal exists for the time programmed in this
setpoint a voltage phase reversal condition will occur.
Vb(c or n) + 30°
Va(b or n) = 0° (reference)
Vc(a or n) = –240°
Vb(c or n) – 30°
Vb(c or n) = –120°
shaded area = angle tolerance allowed
before phase reversal will occur
Vcb – 30°
Vab=0° (reference)
Vcb + 30°
Vcb = 60°
Vbc = –120°
shaded area = angle tolerance
allowed before phase reversal
will occur