changes the voltage at that given location will change proportionally as a result when a predetermined amount of change in the coating voltage is determined it can be assumed that a current to the bus bars is discontinued or there is a reduction of current through the bus bars due to increased resistance of the bus bars the increased resistance can be due to a discontinuity i e break in the bus bar or a crack in the conductive coating in this manner the electric field detector 170 operates to detect a break in the bus bars and or conductive coating by monitoring the voltage in the coating 62 at the position of the sensor 170 although not limiting in the present invention for the purpose of the following discussion the current flows through the coating 62 from the bus bar 68 to the bus bar 66 so that the voltage drop within the coating 62 is from the bus bar 68 to the bus bar 66 in the particular non limiting embodiment illustrated in fig8 and 10 a reference voltage is provided to the comparator 171 from the power source 72 through the wire 174 the current flows through the bus bar 68 and through the coating 62 to the bus bar 66 a circuit of the comparator 171 monitors the voltage of the coating 62 the comparator 171 continuously compares the reference voltage from the power source 72 to the measured voltage of the coating 62 via the detector wire 172 when the measured voltage from the detector wire 172 differs from the reference voltage by a predetermined amount an output signal from the comparator 171.