AS 62054.21:2018 pdf free.Electricity metering (AC)-Tariff and load control Part 21: Particular requirements for time switches (IEC 62054-21:2017 (ED.1.1), MOD).
7.5 Functional requirements and tests — accuracy
7.5.1 Time setting and programming
7.5.1.1 Time switches with mechanical analogue dials
On a day dial, it shall be possible to set the time with an accuracy better than ±7,5 mm. It shall be possible to programme the switching operations with a resolution of 15 mm or smaller and it shall be possible to programme a minimum of two successive switching operations at least within 60 mm.
On a week dial, it shall be possible to set the day of the week and the time with an accuracy better than 1 h. It shall be possible to programme the switching operations with a resolution of 2 h or smaller and it shall be possible to programme a minimum of 2 successive switching operations at least within 8 h.
On a year dial, it shall be possible to set the date and time with an accuracy better than 2 days. It shall be possible to programme the switching operations with a resolution of 4 days or smaller and it shall be possible to programme a minimum of 2 successive switching operations at least within 16 days.
7.5.1.2 Time switches with digital displays
It shall be possible to set the date and time (day, month, year, hours and minutes) with an accuracy of 5 s. The setting of the time shall reset the seconds to zero. If setting of the seconds is also available, then the setting of the time shall not reset the seconds to zero, but to the intended value.
NOTE In this case, it is preferable to display also the seconds.
If a daylight saving function is available, the time switch shall display the official time
according to the regulations.
It shall be possible to set the switching operations with a resolution of 1 minute, 1 hour, 1 day,
1 month and 1 year.
7.5.2 Time-keeping accuracy
7.5.2.1 Requirements for synchronous time switches
Synchronous time switches shall have a time-keeping accuracy under normal operating conditions better than ±5 s/30 days assuming that the supply frequency keeps its average on the nominal value.
On operation reserve, at reference temperature, the time-keeping accuracy shall be better than ±120 s/day, if operation reserve is provided by a spring and better than ±1 s/day if operation reserve is provided by a supercapacitor, rechargeable battery or primary cell.
7.5.2.2 Requirements for crystal controlled time switches
At reference voltage and reference temperature, crystal-controlled time switches shall have a time-keeping accuracy better than ±0,5 s/day. The variation of the time-keeping accuracy with the temperature shall be less than (±0,15 s/°C/24 h).AS 62054.21 pdf download.