Testing of single and multifunction energy meters
Until now, the usual method for testing of energy meters has been to use a stabilized, but not very accurate, power source, in combination with a high-precision reference meter. OMICRON’s approach significantly simplifies meter testing. By using state-of-the-art hardware technology, OMICRON provides test sets that are so accurate and stable, that the signal source itself becomes the reference and make a reference meter unnecessary.
The CMC test set – ideally a CMC 256plus or CMC 430 with its high-precision voltage and current outputs – not only provides the test signals, but also has inputs for the meter pulses allowing closed-loop testing. To this end, optical scanning heads for capturing pulses emitted by the meters (infrared LEDs) are available.
Meter allows for manual or automated testing of energy meters. Each line of the test table represents a test point, which can be run in one of the following modes:
- Load test: Accuracy of measurement unit (time power method)
- Mechanism test: Accuracy of entire meter including display
- Gated Mechanism test: Testing internal meter registers
- Injection test: Quick check (wiring, sense of rotation)
- No-load test: No start-up at zero load
- Creep test: Start-up at low loads
In the columns of the table the individual test parameters, the set assessment criteria (tolerance, nominal behavior), and the result of the test, including the assessment (passed or failed) are displayed. For multifunctional meters, or meters with two directions of rotation, a table per test function is available (multiple tabs). Test lines can be repeated several times. In this case the standard deviation is displayed together with the meter error, which allows conclusions of the correctness of the test itself. Single test steps (e.g. those assessed as failed) can be repeated after a test run is finished, without the need for repeating the whole test.
The test quantities are displayed graphically by means of the voltage, current and power phasor diagrams. The test can be performed with any balanced or unbalanced load for single-phase meters (or a single measurement element of a 3-phase meter), 3-wire meters, and 4-wire meters.
For testing the behavior of meters with harmonics or DC components, the following current signal waveforms are available: Sine, Sine + Harmonics, Sine + DC
In a detail view, all parameters can be specified independently for each phase. Apparent, active and reactive power is indicated for each phase and the whole rotary system.
Testing of the following meter functions is supported:
- Wh importing/exporting
- VArh importing/exporting
- I2h and V2h (load/no-load losses of transformers)
- Qh (quantity hour)
The results of an automatic test are clearly summed up in a tabular test report (one line per test point). For a manual test, generating any test quantities, without defining a complete test procedure, can quickly check the correct functioning of meters. In this mode the constant of a meter can also be determined, in case it is not known or if there are doubts about it.
Also operation in conjunction with an external reference meter is possible: When testing with a reference meter, the CMC is used as a current and voltage source. During a load test, the pulses of the meter under test as well as those of the reference meter are registered. The latter form the reference for error calculation.
Furthermore, testing against a 0.02 or 0.01 % reference before a test is run, using the same test points, can eliminate errors of the CMC by loading correction values.
This module is part of the Test Universe software. For more information please refer to the Test Universe website.