User's Manual
Table Of Contents
- Introduction
- Product Description
- Operating Instructions
- Outputs
- Testing
- Installation and Removal
- Glossary
- Display
- Nameplate Information
- Wiring Diagrams
- Technical Specifications
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REX Meter
5 Testing Technical Manual
5-8 30 November 2006
Watthour constant. For transformer rated meters, the K
h
value is called the
secondary K
h
(Kh
sec
) since the transformer ratios are not included. When
instrument transformers are included, then K
h
is called the primary K
h
(Kh
pri
) and
is calculated with the following formula:
A REX meter that is being used with 400:5 current transformers would yield the
following Kh
pri
value:
Calculating meter accuracy. Meter accuracy (percentage registration) can
be calculated by comparing the meter pulse rate to the standard pulse rate and
by using the following formula:
Determining the power. The approximate power of the meter load in
kilowatts during a time period can be obtained by measuring the time it takes to
receive multiple test pulses (P). The test pulses can be counted from the test
LED or the K
h
pulse indicator on the meter LCD. The approximate power may
then be calculated using the following formula:
Note: If the primary load on a transformer rated meter is to be
calculated, the kW value obtained from the equation shown
above must be multiplied by the CTR and VTR.
Meter Testing
Since no field adjustments are required for the REX meter, meter testing is
primarily done to ensure operation within factory specifications. This is normally
done by simply checking the meter calibration. For precise test results, meters
should be tested at the same temperature as the testing equipment. Ideally, this
will be at 72 °F (22 °C).
Using the standard K
h
of 1.0 Wh/pulse, the number of pulses per minute that
the REX meter produces at rated voltage and test current depends on the meter
form, as shown in Table 5-4.
Table 5-4. K
h
pulses per minute based on meter form
VTRCTRKhKh
secpri
××=
pulseWh80
5
400
pulseWh1.0 Kh
pri
=×=
)Khp(
)KhP(
100Accuracy
std
meter
×
×
×=
1000t
60KP
kW
h
×
××
=
Form Test voltage Test current K
h
pulses per minute
1S 120 V 30 A 60 Wh/minute
2S, 200 A 240 V 30 A 120 Wh/minute
2S, 320 A 240 V 50 A 200 Wh/minute
3S and 4S 120 V 2.5 A 5 Wh/minute
3S and 4S 240 V 2.5 A 10 Wh/minute