Siemens APT current transformer – the difference between the ratio on a current transformer and the ratio on a watt-hour meter

Create Date: 2024-8-30 12:03:23|Source: APT/Siemens Shanghai Ergong

1. Differences in use

The conversion ratio of the current transformer is inconsistent with the transformation ratio of the ammeter, which will lead to the inability to use the displayed value of the ammeter directly, and the proportional conversion must be carried out;

If the transformer of ratio 5 is used on the meter of ratio 1, the secondary current of CT will generally exceed 1A, so that the transformer of 5 is used on a meter of 1 ratio. The meter than 1 exceeds the range and damages the ammeter;

2. Difference in accuracy

If the transformer of ratio 1 is used on the meter of ratio 5, the measurement accuracy of the ammeter of ratio 5 will be greatly reduced because the current of the secondary CT is less than 1A.

If the 800/5 ammeter is broken and there is no ready-made one, you can use the 300/5 ammeter to replace it temporarily. However, the results of the measurement must be proportionally converted.

3. Differences in relay protection requirements

The short-circuit capacity at the outlet of the circuit breaker remains unchanged at the maximum and minimum operating modes;

The current transformer is a two-phase incomplete star wiring;

GL-11 overcurrent relay is used for overload and quick-break protection;

The operating power supply is DC 220V, and the circuit breaker is in the form of shunt tripping.

Siemens APT current transformer – the difference between the ratio on a current transformer and the ratio on a watt-hour meter

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