Rogowski Coil Against Iron Core Current Transformer

No Core, No Saturation

The coil is wound on a non magnetic former, so there is nothing to saturate. Through a fault, the output stays proportional to the current when an iron core would already be in saturation and lying to the relay.

The Output Needs Integrating

The coil produces a voltage proportional to the rate of change of current, which is 90 degrees ahead of the current itself. An integrator turns that into a current signal. Coils are supplied with a raw mV output for instruments that integrate internally, or with a G1 or G2 integrator giving 333 mV, 0-5 V, or four switchable ranges.

Where The Coil Wins

• Irregular bus, laminated bar and cable bundles
• Very high currents, up to 100 kA
• Wide bandwidth work: 2 Hz to 100 kHz, frequency range 10 Hz to 10 MHz
• Anywhere weight matters or nothing rigid will fit

Where The Iron Core Wins

• Revenue metering, where Class 0.2S is required
• Driving a 5 A panel instrument directly with no electronics
• Installations with no auxiliary supply for an integrator
• Standard switchboard ways where a moulded case frame simply fits

Position Sensitivity

Conductor position sensitivity is quoted at ±2 % maximum and the influence of an external field at ±2 %. In practice that means keeping the conductor near the centre of the loop and closing the coil properly, and keeping the loop away from a heavily loaded adjacent phase.