BS 7856:2013 pdf download – Code of practice for special design and other features of alternating current watthour meters for active energy (MID accuracy classes A and B) for use in the UK
1 scope
This British Standard gives recommendations for special design and otherfeatures of newly-manufactured alternating current watthour meters withratings up to and including 100 A lm.. for installation in domestic and smallcommercial/industrial premises within the United Kingdom.
2Normative references
The following referenced documents are indispensable for the application ofthis document. For dated references, only the edition cited applies. For undatedreferences, the latest edition of the referenced document (including any amendments) applies.
BS 6004:2012,Electric cables – PVC insulated and PVC sheathed cables forvoltages up to and including 300/500 V, for electric power and lightingBS 7647.Radio teleswitches for tariff and load control
BS EN 50470-1:2006,Electricity metering equipment(a.c.) – Part 1: General
requirements, tests and test conditions – Metering equipment (class indexes A,Band c)
BS EN 50470-2,Electricity metering equipment (a.c.) – Part 2: Particularrequirements – Electromechanical meters for active energy (class indexes Aand B)
BS EN 50470-3:2006, Electricity metering equipment (a.c.)- Part 3: Particularrequirements – Static meters for active energy (class indexes A,B and C)
BS EN 62052-21,Electricity metering equipment(a.c.) – General requirements,tests and test conditions – Part 21: Tariff and load control equipment
BS EN 62055-31:2005,Electricity metering – Payment systems – Part 31: Particularrequirements – Static payment meters for active energy (classes 1 and 2)
IEC 60502-1,Power cables with extruded insulation and their accessories forrated voltages from 1 kv (Um = 1,2 kV) up to 30 kv (Um = 36 kV)-
Part 1: Cables for rated voltages of 1 kv (Um = 1,2 kV) and 3 kv(Um = 3,6 kV)
3Terms and definitions
For the purposes of this British Standard the terms and definitions given inBS 7647,BS EN 50470,BS EN 62052-21,BS EN 62055-31 and lEC 60502-1 apply.
4Mechanical features
4.1 For a single-phase,two-wire meter:
a) the overall dimensions of the meter and spacing of fixing holes should be in
accordance with the appropriate values given in Table 1; and
b) the dimensions and spacing of the terminal should be in accordance with
the appropriate values given in Table 1 and shown in Figure 1.
For polyphase meters, the current terminals of directly-connected meters havingrated currents up to and including 100 A should be in accordance with
dimensions K,Land P given in Table 1.
4.2 All conductors connected to the main and load terminals should be clamped effectively. For a screw-fitted terminal, as indicated in Figure 1, there should be two screws in each terminal.
NOTE However, other cable clamping arrangements are permissible. When tested in accordance with Annex A:
a) all main and load terminals, irrespective of design and construction, should resist the movement of any connected cable due to axial and or rotational forces applied to the cables;
b) all main and load terminals, irrespective of design and construction, should not allow slippage of a cable within a connection block;
c) the meter case should not fracture, break or distort to the extent that any hazard is created.
4.3 Auxiliary terminal(s) for single-phase, directly-connected meters should preferably be provided on the right-hand side of the terminal block, enabling auxiliary wiring to clear 18 mm to the right of the centreline of the meter. The auxiliary terminal for switching a two-rate register should be located in accordance with Figure 1 and Figure 2.
4.4 There should not be a facility in single-phase, directly-connected meters for the disconnection of the voltage terminal from the input current terminal. NOTE Polyphase meters can be fitted with such links at the purchaser’s discretion.
4.5 The figure height of a register display should be not less than 4.5 mm.
5 Electrical features
5.1 For single-phase and three-phase meters for use where the neutral is available, the external control of rate change should be achieved by connecting the rate change terminal(s) to neutral. For multi-rate meters, the rate switching logic should be in accordance with Annex B.
5.2 For single-phase import meters, the import register should not decrease under energy flows in the reverse direction to that of intended measurement. For static meters of this type, an indication of this reverse energy flow should be fitted. For single-phase import/export meters, no register should decrease under energy flows in the reverse direction to that of intended measurement.
5.3 The basic and maximum rated currents for different types of meters should be as given in Table 2.