What is Current Transformer accuracy class
IEEE/ANSI C57.13 | IEC61869-2 | IEC60044-1
Accuracy classes according to IEEE/ANSI C57.13
| Metering accuracy class |
Voltage transformers (at 90% to 110% rated voltage) |
Current transformers | ||||||
|---|---|---|---|---|---|---|---|---|
| At 100% rated current | At 10% rated current | At 5% rated current | ||||||
| Minimum | Maximum | Minimum | Maximum | Minimum | Maximum | Minimum | Maximum | |
| 0.15S | - | - | 0.9985 | 1.0015 | - | - | 0.9985 | 1.0015 |
| 0.15 | 0.9985 | 1.0015 | 0.9985 | 1.0015 | - | - | 0.9970 | 1.0030 |
| 0.15N | - | - | 0.9985 | 1.0015 | 0.9970 | 1.0030 | - | - |
| 0.3S | - | - | 0.9970 | 1.0030 | - | - | 0.9970 | 1.0030 |
| 0.3 | 0.9970 | 1.0030 | 0.9970 | 1.0030 | 0.9940 | 1.0060 | - | - |
| 0.6 | 0.9940 | 1.0060 | 0.9940 | 1.0060 | 0.9880 | 1.0120 | - | - |
| 1.2 | 0.9880 | 1.0120 | 0.9880 | 1.0120 | 0.9760 | 1.0240 | - | - |
IEC61869-2, Table 201
Limits of ratio error and phase displacement for measuring current transformers (classes from 0.1 to 1)
| Accuracy Class |
± Percentage current(ratio) | ± Phase displacement | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Minutes | Centiradians | |||||||||||
| 5% | 20% | 100% | 120% | 5% | 20% | 100% | 120% | 5% | 20% | 100% | 120% | |
| 0.1 | 0.4 | 0.2 | 0.1 | 0.1 | 15 | 8 | 5 | 5 | 0.45 | 0.24 | 0.15 | 0.15 |
| 0.2 | 0.75 | 0.35 | 0.2 | 0.2 | 30 | 15 | 10 | 10 | 0.9 | 0.45 | 0.3 | 0.3 |
| 0.5 | 1.5 | 0.75 | 0.5 | 0.5 | 90 | 45 | 30 | 30 | 2.7 | 1.35 | 0.9 | 0.9 |
| 1.0 | 3.0 | 1.5 | 1.0 | 1.0 | 180 | 90 | 60 | 60 | 5.4 | 2.7 | 1.8 | 1.8 |
IEC61869-2, Table 202
Limits of ratio error and phase displacement for measuring current transformers (classes from 0.2S to 0.5S)
| Accuracy Class |
± Percentage current(ratio) | ± Phase displacement | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Minutes | Centiradians | ||||||||||||||
| 1% | 5% | 20% | 100% | 120% | 1% | 5% | 20% | 100% | 120% | 1% | 5% | 20% | 100% | 120% | |
| 0.2S | 0.75 | 0.35 | 0.2 | 0.2 | 0.2 | 30 | 15 | 10 | 10 | 10 | 0.9 | 0.45 | 0.3 | 0.3 | 0.3 |
| 0.5S | 1.5 | 0.75 | 0.5 | 0.5 | 0.5 | 90 | 45 | 30 | 30 | 30 | 2.7 | 1.35 | 0.9 | 0.9 | 0.9 |
IEC60044-1, Table 11
Limits of current error and phase displacement for measuring current transformers (classes from 0.1 to 1)
| Accuracy Class |
± Percentage current(ratio) | ± Phase displacement | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Minutes | Centiradians | |||||||||||
| 5% | 20% | 100% | 120% | 5% | 20% | 100% | 120% | 5% | 20% | 100% | 120% | |
| 0.1 | 0.4 | 0.2 | 0.1 | 0.1 | 15 | 8 | 5 | 5 | 0.45 | 0.24 | 0.15 | 0.15 |
| 0.2 | 0.75 | 0.35 | 0.2 | 0.2 | 30 | 15 | 10 | 10 | 0.9 | 0.45 | 0.3 | 0.3 |
| 0.5 | 1.5 | 0.75 | 0.5 | 0.5 | 90 | 45 | 30 | 30 | 2.7 | 1.35 | 0.9 | 0.9 |
| 1.0 | 3.0 | 1.5 | 1.0 | 1.0 | 180 | 90 | 60 | 60 | 5.4 | 2.7 | 1.8 | 1.8 |
IEC60044-1, Table 12
Limits of current error and phase displacement for measuring current transformers for special application
| Accuracy Class |
± Percentage current(ratio) | ± Phase displacement | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Minutes | Centiradians | ||||||||||||||
| 1% | 5% | 20% | 100% | 120% | 1% | 5% | 20% | 100% | 120% | 1% | 5% | 20% | 100% | 120% | |
| 0.2S | 0.75 | 0.35 | 0.2 | 0.2 | 0.2 | 30 | 15 | 10 | 10 | 10 | 0.9 | 0.45 | 0.3 | 0.3 | 0.3 |
| 0.5S | 1.5 | 0.75 | 0.5 | 0.5 | 0.5 | 90 | 45 | 30 | 30 | 30 | 2.7 | 1.35 | 0.9 | 0.9 | 0.9 |
