It is very clear that we cannot place sensitive electrical equipment (operating at low voltage / current) in a high current / voltage circuits. Therefore, we use an interface transformer for this purpose to reduce the current or voltage.
For voltage above 240 V and current more than 100 A using the CT (Current transformer) is necessary.
CT types:
- Wound
- Bushing, Window or Donut
- Bar
Our discussion here is about Metering CT which used to supply the suitable current for measuring devices of electrical panel. The basis of its operation is that by analysing the voltage and current changes in the primary and secondary windings, the desired values can be measured.
CT parameters:
- I1 (Primary current): It must be minimum 25% more than maximum load current.
- I2 (Secondary current): Normally 1A and 5A
- Rated voltage or insulation level
- Burden: Must be at least 25% of the total power of the measuring equipment connected to the secondary part of the transformer.
- Accuracy: According to IEC or IEEE
- Type: Wound / Window / Terminal
- Size: It must be suitable for the conductor being monitored
- Installation type
CT shapes:
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