4–44 PQM POWER QUALITY METER – INSTRUCTION MANUAL
S4 ALARMS/CONTROL CHAPTER 4: PROGRAMMING
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 orn) = 0° (reference)
Vc(a orn) =–240°
Vb(c or n) – 30°
Vb(c orn) =–120°
shaded area = angletolerance allowed
before
hase reversal will occur
Vcb – 30°
Vab = 0° (reference)
Vcb + 30°
Vcb =60°
Vbc =–120°
shaded area = angletolerance
allowed before phase reversal
will occur
Courtesy of NationalSwitchgear.com
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