Paragraph 9 Margins of error
The maximum error permitted for single and polyphase whole current meters and for single and polyphase transformer operated meters, when tested with transformers connected, shall not exceed plus or minus 1.9% for tests 1, 2, 3 and 4 given in Table 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 tests 1, 2, 3 and 4 given in Table 2.
For polyphase whole current and transformer operated meters, when tested with transformers connected, the maximum error shall not exceed plus 2% or minus 3% for tests 5 and 6 given in Table 2.
For polyphase whole current and transformer operated meters, when tested without transformers connected, the maximum error shall not exceed plus 1.5% or minus 2.5% for tests 5 and 6 given in Table 2.
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%; unless by matching transformers to meters enables the total error of meter and transformers to meet the requirements of paragraphs 9(1), 9(2), 9(3) and 9(4) above.
TABLE 1
| Influence quantities | Reference value | Tolerance |
|---|---|---|
| Ambient temperature | Reference temperature or, if not indicated, 23°C. | >15°C to <30°C |
| 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 (paragraph 5.4) | 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 No. & 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 no. 4 & 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 & polyphase | Balanced |
| 2 (intermediate) | 1 | Ib or 125%IB | Any load between 25%–75% of the value specified for Test No. 1 | Single & polyphase | Balanced | ||
| 3 (low) | 1 | 5%Ib | 1.67% (note 2) | 5% | 5% | Single & polyphase | Balanced |
| 4 (inductive) | 0.5 | Ib or Imax | 100% | The same value selected for Test No. 1 | Single & polyphase | Balanced | |
| 5 (element) | 1 | Ib | 100% | The same value selected for Test No. 1 | Polyphase | One phase loaded in turn | |
| 6 (inductive) (element) | 0.5 | Ib | 100% | The same value selected for Test No. 1 | Polyphase | One phase loaded in turn | |