Ferro-Damp

About this product

The Ferro-Damp is Orion EE's active ferroresonance protection device for MV networks with isolated or resonant neutral earthing where voltage transformers are installed on live busbars. Ferroresonance is a non-linear resonance phenomenon that occurs when the inductive impedance of a voltage transformer interacts with the capacitance of an isolated MV network — particularly when single-phase switching, cable connections or specific network configurations create conditions for sustained overvoltage oscillation. Left unprotected, ferroresonance can cause rapid insulation damage and thermal destruction of voltage transformers, switchgear and connected equipment within seconds. The Ferro-Damp detects the characteristic voltage and current signatures of ferroresonance as it develops and immediately inserts a damping resistance into the VT secondary circuit to dissipate the resonance energy. Unlike passive solutions such as fixed loading resistors — which create continuous power loss — the Ferro-Damp is inactive under normal operating conditions and only activates when ferroresonance is detected, minimising energy consumption while providing continuous protection. Typical applications include isolated-neutral MV networks where electromagnetic voltage transformers are installed on busbars in ring main units, secondary substations and medium-voltage switchboards, particularly in cable-rich urban networks where high cable capacitance increases ferroresonance risk. It is especially important in networks where single-phase cable switching operations — such as for routine maintenance or fault isolation — are routine operating procedures.

Technical Specifications