The Meters (Certification) Regulations 1998

Margins of error

9.—(1) The error permitted for—

(a) single phase and polyphase whole current meters and

(b) single phase and polyphase transformer operated meters when tested with transformers connected

shall not exceed plus or minus 1.9 per cent. for test numbers 1, 2, 3 and 4 in table 2.

(2) The error permitted for both single phase and polyphase transformer operated meters, when tested without transformers connected, shall not exceed plus or minus 1.4 per cent. for test numbers 1, 2, 3 and 4 given in table 2.

(3) The error permitted for polyphase whole current meters and transformer operated meters, when tested with transformers connected, shall not exceed plus 2 per cent. or minus 3 per cent. for test numbers 5 and 6 given in table 2.

(4) The error permitted for polyphase transformer operated meters, when tested without transformers connected, shall not exceed plus 1.5 per cent. or minus 2.5 per cent. for test numbers 5 and 6 given in table 2.

(5) Where current and voltage transformers are intended to be used with meters and are not tested connected to a meter then the error of the transformers at any load point throughout the rated range shall not exceed 0.5 per cent.

TABLE 1

Influence quantities	Reference value	Tolerance
Ambient temperature	Reference temperature or, if not indicated, 23°C.	±2°
Meter position	Vertical	±3°
Voltage	Reference voltage	±1.5%
Frequency	Reference frequency of 50Hz	±0.5%
Voltage and current waveform	Sinusoidal form	Distortion factor <5%
External magnetic induction at the reference frequency (paragraph 5(5))	Zero	Induction value that does not produce a relative error variation of more than ±0.3%

TABLE 2

		Test load in terms of marked current
	Test number and load	Power factor	Basic/maximum	Maximum continuous	Long range	Short range	Meter type	Polyphase meter load
1 (high)	1	Imax	100%	100%–200%(Note 1)	100%–125% (Note 1)	Single and polyphase	Balanced
2 (intermediate)	1	Ib or 125%Ib	Any load between 25%–75% of the value specified for test number 1 (Note 1)			Single and polyphase	Balanced
3 (low)	1	5%Ib	1.67% (Note 2)	5%	5%	Single and polyphase	Balanced
4 (inductive)	0.5 (Note 3)	Ib or Imax	100%	The same value selected for test number 1		Single and polyphase	Balanced
5 (element)	1	Ib	100%	The same value selected for test number 1		Polyphase	One phase loaded in turn
6 (inductive) (element)	0.5 (Note 3)	Ib	100%	The same value selected for test number 1		Polyphase	One phase loaded in turn

Note 1 Where a range is given, any value within that inclusive range may be selected.

• Note 2 For maximum continuously rated prepayment meters, the low load test value may be twice the value shown.

• Note 3 For test numbers 4 and 6, the inductive power factor shall be between 0.45 and 0.55 inclusive.