Testing Smart Meter PART – I

The Smart Meter is an asset to the utilities that realises the revenue flow from the consumers to the power utilities and it is the revenue box for the utilities. The smart meter has two-way communication, which connects the consumer to utility. Smart meters are extremely critical components in the power network. Accuracy and reliable performance of smart meters and communication system between the smart meter and control centre are of vital importance. Also, high accuracy measurement is required in Smart Meter for accurate correct billing and to gain confidence of the customers. Testing of Smart Meters is a required activity to ascertain the quality and performance of the smart meters as per the relevant Standards. This article presents the test qualification requirements for Smart Meters...

Testing Smart Meter

Smart Meter comprises metrology elements, two-way communication module(s) and controlled load switches [1]. A smart meter has capability for measurement, computation, capturing of tamper events, storing, communication and connect/disconnect control. With the addition of two-way communication between the smart meter and the utility, the consumer will be provided with information about consumption pattern, time based tariff and alert messages. In case of time based tariff, the consumer will get benefit of smart usage of power with minimum possible tariff. The Smart meters shall be designed to comply with the relevant standards. Bureau of Indian Standards (BIS) is the first organisation to introduce standards for conformity of Smart meters viz., IS 16444 (Part 1) in the year 2015 & 16444 (Part 2) in the year 2017 globally. As per the guidelines of Central Electricity Authority all the utilities are making mandatory for the type testing of smart meters as per the relevant standards to ensure the stability, reliability, interoperability and accurate billing of supply lots. This will also ensure the safety of the personnel and equipment. Therefore, testing is a mandatory requirement by designers, manufacturers and utilities. Testing covers both meteorology testing and DLMS protocol testing.

The rollout of Smart meters in the country by various Utilities are on the fast track as per the guidelines of Ministry of Power, Govt. of India. Many utilities have implemented smart grid pilot projects across the country. In this regard, CPRI has established testing facilities to render testing services to the manufacturers and utilities.

Smart meter is one of the important components in implementation of smart grid. The smart meter shall provide the following minimum functionalities in the smart grid.

  • One of the prime requirements for implementation of smart grid is two-way communication between the meter and the control centre.
  • Automatic capture of meter readings and provide real time data and information.
  • Detect instantaneous tamper events and report to control centre real time and store the data.
  • Broadcast of scheduled load shedding to consumers.
  • Monitor remotely the load and consumption patterns and allow their consumers to use/schedule their consumption effectively and availability of power supply without interruptions.
  • For connect/disconnect of load switches for load management and non-payment of bill etc.
  • The Smart meter comprises following functional zones:

a. Metering,
b. Load switch,
c. Metering protocol, and
d. Communication modules.

The minimum features of smart meters are:

  • Measure and compute electrical parameters.
  • Store and communicate requested data as per programmed interval.
  • Detect, resolve abnormal & tamper events and store the data.
  • Inbuilt memory to store all relevant meter data, events for a required period.
  • Communication protocol as per open protocol standard (IEC 62056 DLMS/COSEM).
  • Prepaid and post-paid metering options.
  • Option for remote configuration.
  • Interface to HAN and compatible devices.
  • Remote firmware upgrade.
  • Support remote load management/load curtailment.
  • Load Reconnect / Disconnect switch.
  • NAN or WAN module as mandatory communication module for communication to DCU or HES respectively and with IHD optionally.

Communication requirement:

Communication technologies are critical elements for connecting thousands of meters from the field to the utility’s Metering Data Management Centre. The communication link is a very vital requirement for the success of the smart grid.

The smart meter requirement is NAN, WAN and IHD communication modules, which are required for establishing connectivity with Smart Meter by the external entities such as DCU and HES respectively – and optionally with IHD. The communication technology chosen by the utility shall be either wired or wireless depending on technical feasibility best suited for a given geographical area. The communication module(s) selected shall be:

  • for NAN:  PLC or RF and
  • for WAN: Cellular technologies or OFC technology.

This article highlights on the details of all tests mentioned in the relevant standards for Smart Meters.

Applicable Indian Standards for Smart Meters

IS 16444 consists of Two parts:

  • IS 16444 (Part 1): 2015 was adopted by the BIS in 2015 & subsequently Amendment No. 1, Feb. 2017 & Amendment No. 2, August 2019 were issued by BIS.

The above standard covers the general requirements and tests for a.c. Static Direct connected Watt-hour Smart Meter, Class 1 & 2. It applies to:

  • Static Watt-hour direct connected meters consisting of measuring element(s), time of use register (s), display, load switch and built in / plug in type bidirectional communication module all integral with the meter housing.
  • Smart meter for indoor use & capable of forward (import) or both forward (import) and reverse (export) energy measurement.

Cross reference Indian Standards for IS 16444 (Part 1): 2015

  • IS 13779: 1999 (RA 2014) – a.c. Static watt-hour meters, Class 1 & 2.
  • IS 15884: 2010 (RA 2016) – Alternating current direct connected Static Prepayment Meters for Active Energy (Class 1 & 2).
  • IS 15959 (Part 1): 2011 (RA 2016) – Data exchange for electricity meter reading, tariff and load control: Companion Specification. Part 1 Static Energy Meter
  • IS 15959 (Part 2): 2016 – Data exchange for electricity meter reading, tariff and load control – Companion Specification Part 2 Smart meter.
  • IS 16444 (Part 2): 2017 was adopted by the BIS in 2017 & subsequently Amendment No. 1, 2019 was issued by BIS.

The above standard covers the general requirements and tests for a.c. Static Transformer operated Watthour & VAR-Hour Smart Meters, Class 0.2S, 0.5S & 1.0S. It applies to:

  • Transformer operated static watt-hour meters & VAR-Hour meters consisting of measuring element(s), time of use register(s), display, load switch and built in / plug in type bidirectional communication module all integral with the meter housing.
  • Smart meter for indoor use & capable of forward (import) or import and export energy measurement.

Cross reference Indian Standards for IS 16444 (Part 2): 2017

  • IS 14697: 1999 (RA 2019) – a.c. Static Transformer operated Watthour & VAR-Hour meters, Class 0.2S, 0.5S & 1.0S.
  • IS 15959 (Part 1): 2011 (RA 2016) – Data exchange for electricity meter reading, tariff and load control: Companion Specification. Part 1 Static Energy Meter.
  • IS 15959 (Part 3): 2017 – Data exchange for electricity meter reading, tariff and load control – Companion Specification Part 3 Smart meter (Transformer operated kWh and kVARh, Class 0.2S, 0.5S & 1.0S).

Test Requirements for Smart Meters [1] [2]

Smart meter shall be subject to

  • Metrology tests
  • Load Switch capability test
  • Data Exchange Protocol and
  • Smart meter Communicability test (Optional test)

Tests for Metrology include:

  • Type tests including Construction requirements, Clearance and Creepage distances, Display of values, Output device and Marking.
  • Acceptance tests (Subset of Type test)
  • Routine tests (Subset of Acceptance test)

Type Test [3] [4]:

Series of tests carried out on meters of the same type having identical characteristics, selected by manufacturer to prove conformity with all the requirements of standard for the relevant class of meter. These are intended to prove the general qualities & design of a given type of meter.

Acceptance Test [3] [4]:

Tests carried out on samples taken from a lot for the purpose of acceptance of the lot.

Routine Test [3] [4]:

Tests carried out on each meter to check conformity with the requirements of standard in aspects which are likely to vary during production.

Number of Samples and Criteria for Conformity

  • As per IS 16444 (Part 1), Type test shall be made on minimum one or more specimens (1st Set) selected by the manufacturer and test sequence shall be as given in Table 1 [1]. All the specimen shall comply with all the tests given in Table 1 [1]. In case of one test specimen failing to comply in any respect further testing shall be stopped. Further same number(s) of specimen(s) (equivalent to 1st set) shall be taken for testing, all of which shall comply with requirements of standard given in Table 1 [1].

In addition to the above, one additional sample shall comply with load switch requirement of UC1 category and another sample shall comply with data exchange protocol requirement of the standard. For UC2 and UC3 category of meters, the number of samples for load switch requirement shall be as per Annexure G of IS 15884 [5].

Minimum number of Samples required for conformity with the standard are:

For Utilisation Category UC1 type of Smart Meter: 1 Sample for Type test + 1 Sample for Load Switch test + 1 Sample for Test for Data Exchange Protocol and Tests for Smart Meter Communicability.

For Utilisation Category UC2/UC3 type of Smart Meter:

1 Sample for Type test + 4 Samples for Load Switch test + 1 Sample for Test for Data Exchange Protocol and Tests for Smart Meter Communicability.

For acceptance test, recommended sampling plan and the criteria for acceptance of the lot are given in relevant Annex H of IS 13779[3].

  • As per IS 16444 (Part 2), Type test shall be made on minimum one or more specimens (1st Set) selected by the manufacturer and test sequence shall be as given in Table 1 [2]. All the specimen shall comply with all the tests given in Table 1[2]. In case of one test specimen failing to comply in any respect further testing shall be stopped. Further same number(s) of specimen(s) (equivalent to 1st set) shall be taken for testing, all of which shall comply with requirements of standard given in Table 1 [2].

In addition to the above, one additional sample shall comply with data exchange protocol requirement of this standard [2].

Minimum number of Samples required for conformity with the standard are:

1 Sample for Type test + 1 Sample for Test for Data Exchange Protocol and Tests for Smart Meter Communicability.

For acceptance test, recommended sampling plan and the criteria for acceptance of the lot are given in relevant Annex E of IS 14697[4]….to be continued.


Authors

V Suresh

 

 

 


Suresh
holds Bachelor’s degree in Electronics & Communication Engineering and Master of Business Administration in Finance from Bangalore University. He is with Central Power Research Institute for 30.5 years and presently working in Metering & Utility Automation Division.

V. Harinath Babu holds Bachelor’s degree in Electronics. He is having experience of 35 years in academic and Central Power Research Institute and is heading Metering & Utility Automation Division there.

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