Line mounted apparatus for measuring line potential

A self contained hot stick mounted radio transmitting module may be permanently mounted on or temporarily pushed against the power conductor of electrical transmission line (3). The module is capable of measuring the potential difference between the conductor and ground. The module digitizes and transmits the value of the potential difference to a ground receiver. The module is donut shaped and opens like a pair of jaws. The contact with the power line is accomplished via a resilient conductive elastomer that covers the surfaces in contact with the power conductor. The potential difference between ground and the power conductor is measured with an operational amplifier (19) in an integrating configuration to convert the leakage current from the module to ground into a proportional voltage from a low impedance source. The integrator outputs a voltage proportional to the current flowing into the equivalent capacitance formed by the outer surface of the module and ground. The current is generated by the voltage difference between the power conductor and ground. The power conductor (3) is engaged by a pair of jaws inserts comprising two concentric conducting rings separated by a thin insulating layer forming a large capacitor. The electronic components within the unit are protected by a signal conditioning network to preclude destruction of components in the event of lightning strikes or other overvoltage conditions.