This piece was originally published in the June 2016 issue of ei, the magazine of the electroindustry.
Gordon Belcher, Chair, ANSI C12 SC1 Subcommittee
Paul Orr, Program Manager, NEMA
The history of ANSI C12.1 American National Standard for Electric Meters—Code for Electricity Metering parallels that of NEMA, its secretariat.
Electrical metering standards were first developed in the U.S. by the American National Standards Institute (ANSI) C12 Committee in 1910, the same year that the Electric Power Club incorporated itself to improve the state of electrical manufacturing in the U.S., and six years before it merged with the Associated Manufacturers of Electrical Supplies to form NEMA.
There have been 12 editions of ANSI C12.1 since then. The preface to ANSI C12.1-1910 could have been written today:
In undertaking…to formulate a meter code, it was the ambition of the Meter Committee…to produce a reliable and up-to-date manual covering the many phases of electric meter practice as encountered by all companies, both large and small. …[S]uch a Code, if intelligently prepared, would prove of great value not just to those actually engaged in operating meters, but also to those interested in the practices of metering from other standpoints, namely, official, legal, etc….It is hoped that [the code] may find its place among reliable books of reference in the hands of those responsible for, and interested in, the purchase, installation, and operation of electric meters.
Currently, the ANSI C12 Committee for Electricity Metering develops and maintains electricity metering standards. It is chaired by a representative from the National Institute of Standards and Technology, and its members represent manufacturers, utilities, and general interest.
The ANSI C12 suite has been expanded over the years to include emerging technology and increasingly stringent requirements by suppliers and users.
The newly published version of ANSI C12.1 has been modified to respond to a changing industry and improve the clarity of some of the tests. This standard continues to form the basic requirement for all kilowatt-hour metering devices as the metering environment moves from its original electromechanical platform toward a fully solid-state one.
Even though many original specifications have been retained—primarily to maintain support for older electromechanical devices—changes have been introduced that better address the testing of solid-state equipment not covered within ANSI C12.20. Changes also reflect operating best practices that have been introduced as a result of newer technology, including
- new terms and definitions, including clarification of balanced voltages for various service configurations, instrument transformer, national metrology institutes, and even the meter itself;
- more concise testing procedures, including acceptable performance criteria for 0.5 class meters not already covered under ANSI C12.20;
- a move to update the temperature rise testing requirements to help align with similar requirements for meter sockets as described in ANSI C12.7;
- updated standards for new acceptance and in-service testing practices, including clarification of specified ANSI-defined sampling procedures as the referenced sampling routines;
- updated section to better clarify testing guidelines per equipment type; and
- an update to Appendix D to provide an informative table for periodic in-service testing schedules.
The changes incorporated in ANSI C12.1 reflect current operational and equipment trends within the utility industry. The benefits of these changes will be realized not only by equipment manufacturers and utilities but also by utility customers through the addition of clear and concise testing requirements for solid-state metering equipment now used in most homes as well as from efficiencies gained through industry best practices for in-service testing.
This collection contains all parts of ANSI C12 and NEMA SG-AMI 1. The NEMA Smart Meter Package is available in electronic and print versions for $1,227 on the NEMA Standards Store website.