With all meters expected to be smart prepaid meters in the next three to four years, the role of metering in India is expected to evolve significantly. From energy accounting and revenue administration, smart meters will be critical to AT&C loss reduction, renewable energy integration, demand forecasting, load management and energy conservation. Hence, testing the quality and reliability of energy meters is of utmost importance.
Standards for meters
The Indian metering industry is a heterogeneous one with multiple communication protocols, which often pose interoperability issues, making meter testing an even more complex task. However, the Bureau of Indian Standards (BIS) has defined metering standards to help undertake a comprehensive assessment of meters. The BIS standards for meters include IS 13779 for single-phase and three-phase conventional whole current meters; IS 15884 for single-phase/three-phase prepaid whole current meters; IS 14697 for three-phase transformer-operated meters; and IS 15959 Part 1 for data exchange protocol. In addition, tests for solar radiation and ingress protection, namely, IP54, need to be performed for outdoor meters.
In the case of smart meters, testing is done as per IS 16444 Part 1 (2015) Amendment 1 and IS 15959 Part 2 (2015) Amendments 1 and 2 for whole current single-phase and three-phase meters, and IS 16444 Part 2 (2017) and IS 15959 Part 3 (2017) for transformer-operated smart meters. The communicability test is done on smart meters as per IS 15959 Parts 2 and 3. Further, IEC 62056 is already being adopted by many countries and is now finding a place in many tenders floated by utilities in India as well. IEC 62056 is the only open standard that can be tested using a conformance test tool (CTT) maintained by DLMS UA. The purpose of the CTT is to verify that the device implementation conforms to the standard and, if not, to show which parts of the standard are not correctly implemented. The DLMS UA regularly maintains the conformance test specifications and the CTT to allow testing of new features and to increase the depth of testing. The Central Power Research Institute (CPRI) has the CTT to test meters with DLMS compliance.
Types of tests
Meter testing is undertaken at various stages of the meter development, right from the designing of meters to their installation in the field. Both meter manufacturers and procurers are responsible for the quality of meters. While the former need to expand their testing facilities and undertake research and development (R&D) to improve meter design, the latter need to identify reliable manufacturers with a proven track record for quality procurement.
The key meter tests include development tests, type tests, routine tests and acceptance tests. The development test is undertaken to ensure that the meter design complies with the established standards. The type test helps ensure that the meter complies with product standards and secure type approval. Two other important tests are routine tests, undertaken at the factory, and acceptance tests, undertaken at the time of the acceptance of the meter.
As per the CEA’s guidelines, smart meters are required to undergo type tests and test certificates, and routine and acceptance tests. Smart meters are tested for all the type tests as per IS: 16444 (latest version) in a third-party independent laboratory. The number of samples for testing and the criteria for conformity is as per IS 16444. The factory acceptance and routine tests are carried out as per IS 16444. Meters are also tested for all functional requirements through communication as a part of the acceptance test. Besides, meters may undergo other tests, which include metrology testing, to assess the insulation properties, accuracy, electromagnetic compatibility, climatic influences and other electrical and mechanical requirements. The load switch capability test assesses the performance of the load switch used for remote connect/disconnect. The DLMS protocol verification is the last stage of meter testing.
Challenges and the way forward
The key concerns pertaining to meter testing are the lack of adequate testing facilities and the long duration of tests that leads to delays in procurement.
In India, currently four laboratories are ready for testing smart meters as per IS 16444-Part 1 at the CPRI, Bengaluru; CPRI, Bhopal; Electrical Research and Development Association (ERDA), Vadodara; and Yadav Measurements Private Limited (YMPL), Udaipur. According to government estimates, the total capacity assessed by these facilities is approximately 300 models/makes per year. CPRI Bengaluru is also ready for testing smart meters as per IS 16444-Part 2. Other facilities are expected to be ready with IS 16444-Part 2 shortly.
Various measures are being taken to reduce the duration of meter testing. These include the use of different samples for different tests, and simplification of meter specifications in tenders and anti-tamper requirements. The BIS process for granting certification to meter manufacturers after type testing at the accredited labs is also being streamlined.
Net, net, with the central government targeting to deploy 250 million smart meters for all consumers over the next few years, a larger number of testing facilities across the country will be required.
Nikita Gupta