4–22
PQM POWER QUALITY METER – INSTRUCTION MANUAL
S2 SYSTEM SETUP
CHAPTER 4: PROGRAMMING
If A AND B ONLY, A AND C ONLY, or A ONLY connection is selected, the
neutral sensing must be accomplished with a separate CT.
•
PHASE CT PRIMARY:
Enter the primary current rating of the phase current
transformers. All three phase CTs must have the same rating. For example, if 500:5 CTs
are used, the
PHASE CT PRIMARY
value is entered as
500
. The
PHASE CT PRIMARY
factory default is
OFF
. While set to
OFF
, the PQM is forced to an alarm state as a safety
precaution until a valid CT value is entered. Ensure that the CT is connected to the
correct 1 A 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 PQM calculates the neutral current
using the vector sum of
I
a
+
I
b
+
I
c
=
I
n
. If a residual connection is required using the
PQM 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
selections 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 PQM. The
VT
NOMINAL SECONDARY VOLTAGE
setpoint is replaced by
NOMINAL DIRECT INPUT
VOLTAGE
. With external VTs (depending upon how many external VTs are used) 4
WIRE WYE (3 VTs) or 4 WIRE WYE (2 VTs) 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
V
an
+
V
bn
+
V
cn
=
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 PQM. With external VTs, 3 WIRE DELTA (2
VTs) must be selected.
The PQM accepts input voltages from 0 to 600 V AC between any two of the voltage
terminals (V
1
, V
2
, V
3
, and V
n
). 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 V
1
, V
2
and V
3
, ensure that
the voltage common input V
n
is grounded. This input is used as a reference for
measuring the voltage inputs.
All connections to the PQM 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
VT RATIO
should be 4200 /
NOTE
NOTE
Содержание Multilin PQM
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