Operation: CP1SD/T/L Version
CENTRON® Polyphase Meter Technical Reference Guide
85
If the meter is being tested using single phase test methods, a coil factor must be included in
the calculations. See the table below for the appropriate factor.
Meter Coil Factors
Form
Series
A Phase Only
B Phase Only C Phase Only
9(8)
1
, 16(15,14)
3
1
1
1
1 When testing under true polyphase conditions, Forms 9 and 16 can only be tested as a 4-Wire
Wye. These forms cannot be tested as 4-wire deltas because of present limitation inherent in the
test equipment.
If accuracy or repeatability is poor, the Kh may be incorrect or the “settling time” in
the test bench must be adjusted. (Itron recommends a 4–5 second settling time.)
Testing Using the Load Indication Annunciator
The CENTRON Polyphase meter is capable of visually being tested by using the load
emulation annunciator shown in Load Indication/Direction Annunciator. As further
discussed in the load emulation annunciator section, the load emulation annunciator scrolls
at a rate proportional to the programmed energy constant.
Testing Using the Energy/Time Method
As an alternate to the above methods, the energy accumulated by the registers and a
reference standard can be read directly from the display and compared over a period of time.
Energy readings displayed while the meter is in the Test Mode are in floating decimal
format. This will result in maximum resolution for short duration tests.
Recommended Energy Testing Procedures
Testing solid-state meters on test boards designed primarily for electromechanical meters
may sometimes give unexpected results. Erroneous readings could occur on light-load (LL)
tests when the test sequence calls for a light-load test following a full-load (FL) or power-
factor (PF) test. In some cases, PF readings could also be in error when following a FL test.
The errors are always positive and may be a few percent for PF and even greater for LL.
The problem is aggravated on lower voltages and when using large test constants, Kt,
similar to the typical Kh values of comparable induction meters. This problem does not exist
on modern test boards with their latest software.
Test Description
A typical meter test sequence consists of:
1
The voltage and current ramp up at unity power factor to the FL level.
2
A pulse from the meter starts the FL test and another pulse ends it.
3
The phase angle then changes for the PF test. The current may stay at the FL level or
ramp down to zero and back up for the phase angle change.
4
A pulse from the meter starts the PF test and another pulse ends it.
