ICS 91.140.50                          ETD 13

1. Scope

1.1 This standard (Part 2) specifies ac static transformer operated watthour and var-hour smart meters of accuracy class 0.2S,0.5S and 1.0S for the measurement of alternating current electrical active and reactive energy of frequency in the range 50 Hz for single phase and three phase balanced and unbalanced loads. It applies to their type tests, routine tests and acceptance tests.

1.2 It applies only to transformer operated static watthour and var-hour meters consisting of measuring element(s) and register(s) enclosed together in the meter case. It also applies to operation indicator(s) and test output(s). It also applies to multirate tariff meters and meters which measure energy in both directions.

1.3 Some versions of static reactive energy (var-hour) meters may deemed to be covered by this standard as if these are active energy (watthour) meters of appropriate accuracy class with necessary adjustment to power factor. Although it is possible to achieve Class 0.2 S accuracy in static var-hour meters, it is of general opinion that accuracy attainable for var-hour measurement is one level inferior to that in the case of kWh measurement with identical design of measuring elements. Therefore, it is possible for this standard to cover static var-hour meter, Class 0.2 S, and 0.5 S for reactive energy measurement in all transformer operated applications. Only ‘power factor’ wherever it has appeared in this standard, shall be read as ‘sin Ø inductive’ or ‘sin Ø capacitive’. Where Ø is respectively the lagging or the leading power factor angle

1.4 It applies to,

a) transformer operated static watt-hour meters consisting of measuring element(s), time of use of register(s), display and built in type bidirectional communication module all integral with the meter housing.

b) Alternately, the bi-directional communication module could be plug-in type on a dedicated slot with suitable sealing arrangement. The plug-in module shall be field swappable with suitable integrated communication module as agreed between the buyer and the seller.

1.5 The smart meter types as specified in 1.4 (a) and 1.4 (b) shall be suitable for indoor usage and capable of ‘forwarded only’ or ‘import and export’ energy measurement.

1.6 It does not apply to,

a) watthour meters and var-hours meters where the voltage across the connection terminal exceeds 600 V (line to line voltage for meters for poly phase systems), and

b) portable meters, and outdoor meters.

1.7 For rack-mounted meters, the mechanical requirements are not covered in this standard.