What equipment is typically used to transform current from the primary circuit to a smaller proportional amount for protective relays?

• A. Series Capacitors.
• B. Current Transformers.
• C. Potential Transformers.
• D. Voltage reduction relays.

Answer: (B)

The equipment used to transform current from the primary circuit to a smaller, proportional amount for protective relays is the current transformer. Current transformers are designed to step down high currents to lower, manageable levels, allowing protective relays to monitor and respond to electrical currents safely and accurately.

These devices work by using the principle of electromagnetic induction. When the primary current flows through the primary winding, it generates a magnetic field that induces a lower current in the secondary winding, which is connected to the protective relay. This secondary current is proportional to the primary current and allows relays to measure the system's current without directly handling dangerous levels of electricity.

This setup is critical in power systems because it helps to ensure that the protective relays can operate effectively to detect abnormal conditions, such as overloads or faults, without being exposed to the high voltage and currents present in the primary circuit.