Meters (Certification) Regulations (Northern Ireland) 1998

Margins of error

9.—(1) The maximum 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% for test numbers 1, 2, 3 and 4 in Table 2.

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

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

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

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

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 50Hz	± 0.5%
Voltage and current waveform	Sinusoidal form	Distortion factor <5%
External magnetic induction at the reference frequency	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
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.
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			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