This ring core is designed for the Vigilohm insulation fault locators and the VigiPacT type A residual current protection and monitoring relays. It enables the monitoring of the supplied component from the Vigilohm insulation monitor and the measurement of a rated current of up to 250 A for VigiPacT monitoring and protection relays. The transmission ratio is 1/1000. The inner diameter of the toroid is 120 millimeters and it weighs 1.5 kg. The cables must be centered within the toroid, and the diameter of all these cables should not exceed 60 mm. The maximum cross-section per phase (R, S, T, N) is 240 mm² for a copper conductor.