Abnormal Voltage Hazards The possible over-voltages on the unearthed system may cause more frequent failures of equipment than is the system, if earthed. A fault on one phase of an unearthed or impedance- grounded system places a sustained increased voltage on the insulation of un-grounded phases in a 3-phase system. This voltage is about 1.73 times the normal voltage on the insulation. This or other sustained over-voltages on the unearthed system may not immediately cause failure of insulation but may tend to reduce the life of the insulation. Some of the more common sources of over-voltages on a power system are the following: a) Lightning, b) Switching surges, c) Static, d) Contact with a high voltage system, e) Line-to-ground fault, f) Resonant conditions, and g) Restriking ground faults. We, at Atul Casting and Metal Works manufactures all earthing related products such as G.I Strips, G.I plates, G.I Rods, G.I Pipes, C.I covers, Cable Trays, G.I Wire, Manhole Covers and Route Markers for past 50 + Years in heart of New Delhi. Call us at +91 9873361672 for best deals.