When the word “meter testing” popup anywhere in the metering community, most of the time this issue is taken quite lightly. Despite that, this activity plays very significant role in the consumer satisfaction, revenue protection, quality control, compliance with regulatory requirements and image building.
Complexities of the modern meters which includes the several parameter measurement & recording at the same time, power quality related measurements, communication technique and additional functionalities related to billing & tariff etc. has increased the importance of meter testing while manufacturing, accepting or testing at site.
The poor quality meters which are available plenty in the market, has increased the role & responsibility of meter testing division many folds, to ensure that basic energy measurement are done properly at least.
To understand the meter testing world lets first understand who test, when, why and how….
Worldwide energy meters are being tested at the several places in the chain starting from manufacturer to consumer to serve the various objectives. The survey reveals the further useful information and practices are used around the world.
Who test | Meter Manufacturer | Electric Utilities in Laboratory | Electric utilities at site |
Objectives |
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When | At the production stage, after assembling the meter | While receive the meter from the supplier
OR, while sending the meter for installation at consumer places |
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Rate of testing | 100% of manufactured meters | There is no common but following practices revealed from the survey
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There is no common concept but following practices revealed from the survey.
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Testing Practices & Methods | Using Stationary meter test benches to meet large testing volume | Using stationary meter test benches to meet the large testing volume | Using portable phantom load and reference standard. See details in onsite testing practices & methods |
Energy meters are being tested in laboratory by manufacturer before shipping to utilities and by utilities before installing the meters. As mentioned above both the parties have more or less same objectives and use the stationary test benches. It seems to be simple but still offers the great challenge in doing laboratory testing. Mainly are as follows:-
On-site meter testing is gaining in importance among electric utilities around the world. The reasons are to ensure the revenue, comply with regulations and improve customer satisfaction. All the reasons are primarily centered on the correct recording of energy consumption. Correctness of energy recording is in turn dependent on meters instruments transformers.
The onsite testing methods differ from country to country. The methods are mainly influenced by
The onsite testing methods are mainly as follows:-
In this method the tester connects the reference meter to the meter under test, i.e. voltage in parallel and current in series using clamp on CT. This is a quick & economic method but tester has to rely on running consumer load. The objective of such testing is to check the connection and any existing tamper condition and to get a fair idea of the accuracy of the installation.
In this method operator disconnects the meter under test and connect it with electronic phantom load. There are two kinds of phantom loads available to cater for different needs and practices
Automated and uniform testing on all meters is possible by using these modern phantom loads along with a reference standard and software. The result achieved by the uniform testing can be further systematically utilized.
This method is a bit time consuming and requires a phantom load compared to online testing method, but it is closer to laboratory testing. This method is currently used in the European countries which have developed their standard & regulation accordingly.
Testing intervals do vary from country to country. Survey reveals the following information.
Name of country | Interval information | Remarks (additional information) |
Germany | Once in 16 years for electromechanical meters
Once in 8 years for electronic meters |
If pass then both type of meters will be reused for another 4 years
When such testing performed on sample basis then whole population of meters will be accepted if samples pass the acceptance criteria, if not then whole population will be replaced Testing generally performed in Laboratory |
Austria | Once in 20 years for electromechanical meters
Once in 8 years for electronic meters |
If pass then both type of meters will be reused for another 4 years
Testing generally performed in Laboratory |
Denmark | Once in 16 years for electromechanical meters
Once in 8 years for electronic meters |
If pass then both type of meters will be reused for another 4 years |
India | Once in 2 year for bulk consumer, and once in 5 years for domestic consumer
Before installation |
On site testing as per CEA guidelines
Laboratory testing |
Israel | 2-8 years depend on metering mode, meter type and experience | Mainly Laboratory testing |
Hong Kong | No planned testing | Meters only tested when installed and annual maintenance of meters for large customers |
Kenya | Once in a year for large customer | On site testing |
Ukraine | Once in 6 year | Also depend on meter type, manufacturer |
Croatia | No planned testing | |
Colombia | Vary from utility to utility | |
Singapore | Once in a year for large customer | On site testing |
Thailand | Once in a year for large customer | On site testing |
Russia | Once in a year for large customer (at the field condition)
Once in 8 years at laboratory condition |
100% of the billing meters (but not always fulfilled due to lack of infrastructure)
100% of the meters |
Romania | Once in 10 years | Laboratory testing |
Following standard defines the tests, test conditions, and acceptance criteria for meter testing in laboratory according to meter type and class of accuracy.
Apart from international standard most of countries either have adopted the IEC standard as it is or modified to suit the local conditions. For example Indian standard IS 13779, 14697,
There is no international standard exist for such testing. Generally same limit as defined for laboratory testing or with some concession for environmental influence are used.
For example in Australia class 0.5 meter should be with 0.7% limit for on-site testing. In Kenya 3% error is allowed for class 2 electromechanical meters. In Hong Kong +2.5% to -3.5% error is allowed for class 2 meters
Several attempts are being made to define the tests and tests conditions. For example
The power quality has decreased drastically due to several reasons like pollution in power supply due to SMPS, rectifier loading etc. In these circumstances the conventional meter will not be able to record the energy accurately. Studies conducted in the recent years reveal that
Latest design of test benches offer the highest degree of process automation which includes the facilities beyond conventional testing (i.e. accuracy testing and other test as per standard) like automatic handling-connection of meters, pulse i/o testing, adjustment, parameterization, other functional testing. These types of benches are useful for volume testing.
In the recent years, scope of onsite meter testing has been expanded beyond simple accuracy testing. This trend has seen often in European countries. Now Onsite testing also includes the following task/testing/analysis.
The simple word “meter testing” can do significant value addition for both manufacturer as well utilities. The maximum and long term beneficiary will be electrical utilities provided they integrate this activity properly and systematically in their distribution management system. The meter testing at utilities can do following value additions.
“The revenue for a utility will come only via meter and measuring component CTVT, hence its proper & accurate working for a long term will be challenging & interesting for a utility.” Y.K.Nama