GE PQMII Instruction Manual page 104

5–20
precaution until a valid CT value is entered. Ensure that the CT is connected to the
correct 1 or 5 A terminals to match the CT secondary.
• NEUTRAL CURRENT SENSING: Neutral current sensing can be accomplished by using
a separate external CT connection or by calculations. Select "Separate CT" when using
an external CT. If "Calculated" is selected, the PQMII calculates the neutral current
using the vector sum of Ia + Ib + Ic = In. If a residual connection is required using the
PQMII internal CT, the neutral CT primary must be the same as the phase CT primary to
ensure correct readings.
• NEUTRAL CT PRIMARY: This message is visible only if the neutral current sensing
setpoint is set to "Separate CT". Enter the CT primary current. For example, if a 50:5 CT
is installed for neutral sensing enter 50. One amp CTs can also be used for neutral
sensing.
• VT WIRING: Enter the VT connection of the system in this setpoint. The three possible
wiring configurations are Wye, Delta, and Single Phase.
If the system to be measured is a Wye connection, the selections are "4 Wire Wye
Direct", "4 Wire Wye / 3 VTs", and "4 Wire Wye /2 VTs". The "4 Wire Wye Direct" value is
used for systems that are 600 V or less and directly connected to the PQMII. The
NOMINAL SECONDARY VOLTAGE
external VTs (depending upon how many external VTs are used), the "4 Wire Wye / 3
VTs" or "4 Wire Wye / 2 VTs" value must be selected. Note that when using the "4 Wire
Wye / 2 VTs" value, only two voltages are measured; the third voltage is calculated on
the assumption that Van + Vbn + Vcn = 0. This assumption is valid only for balanced
system voltages.
If the system to be measured is a Delta connection, the values are "3 Wire Direct" and
"3 Wire Delta / 2 VTs". The "3 Wire Direct" value should be used for systems that are
600 V or less and directly connected to the PQMII. With external VTs, "3 Wire Delta / 2
VTs" must be selected.
The PQMII accepts input voltages from 0 to 600 V AC between any two of the voltage
terminals (V1, V2, V3, and Vn). These inputs can be directly connected or supplied via
external VTs. External VTs are required for input voltages greater than 600 V AC (line-
to-line). When measuring line-to-line quantities using inputs V1, V2 and V3, ensure
that the voltage common input Vn is grounded. This input is used as a reference for
measuring the voltage inputs.
All connections to the PQMII voltage inputs should be connected using HRC fuses
rated at 2 amps to ensure adequate interrupting capacity.
• VT RATIO: Enter the voltage transformer ratio. All three voltage inputs must be of the
same rating. For example, if 4200:120 VTs are used, the
35.0:1. This setpoint is not visible if
"Single Phase Direct".
• VT NOMINAL SECONDARY VOLTAGE: Enter the nominal secondary of the VTs. If the
voltage inputs are directly connected, enter the nominal system voltage that will be
applied to the PQMII. This setpoint is not visible if the
"4 Wire Direct", or "Single Phase Direct". This value is used to scale an analog output
that is assigned to display voltage as a percentage of nominal.
• NOMINAL DIRECT INPUT VOLTAGE: This setpoint is displayed only if VT WIRING is
selected as a direct connection. The nominal direct input voltage must be entered in
setpoint is replaced by
NOMINAL DIRECT INPUT VOLTAGE
is set to "3 Wire Direct", "4 Wire Direct", or
VT WIRING
VT WIRING
PQMII POWER QUALITY METER – INSTRUCTION MANUAL
CHAPTER 5: SETPOINTS
VT
. With
should be 4200 / 120 =
VT RATIO
is set to "3 Wire Direct",