SMART Inrush Current Limiter: IE-T1 MODEL

 The inrush current is a phenomenon which occurs during transformers (TX) energisation. The inrush current could vary in magnitude each time the transformer is switched ON. This depends on the voltage phase angle and the residual flux angle in the core when de-energised. It lasts for several electrical cycles.

The inrush currents could reach up to 20 times the transformer current rating.

See graph.

- Voltage dips during switching which may affect the plant operation

- Inrush currents generates mechanical forces on transformer coils. While  transformers are designed to withstand inrush current, its design life time will be affected, and could lead to transformer failure

- Currents can induce voltage to near cables which causes nuisance tripping

- The HV CB will experience high current every time it is switched ON to energise the transformer

- Limited rates of energisation (e.g. switching on twice in an hour)

Transformer manufacturers usually provide the inrush current in multiple times of the rated current (e.g. 10 Ir). This usually represents the maximum inrush current a transformer may withdraw when energised. The inrush current magnitude depends on many factors such as:

1. Point of voltage phase at switching
2. Magnitude and polarity of residual flux
3. System inductance and transformer impedance

The above makes it challenging to limit the inrush current when switching the HV CB circuit breaker or switch gear ON.

IE-T1 advanced module monitors the core flux angle and polarity when HV CB trips or switched OFF. It then computes and coordinates the HV CB switching timing such that energisation flux angle is in phase with the transformer core residual flux. This as a result minimises and eleminates the inrush current.

For More Information Click here