Design and development of a line voltage detector

A voltage detector to determine whether a line is energized or not was designed and developed into a prototype. A voltage proportional to the line-to-neutral voltage is filtered through a third order bandpass filter, to obtain the triggering signal for the detector. The prototype was tested in the laboratory using a 1.5 kVA, 120/7200 V, single phase distribution transformer. the low voltage side of the transformer is connected through an autotransformer to a 120 V source. This gives a voltage magnitude of between 0 and 7.2 kV (RMS), depending on the input voltage. The detector is attached to one of the output terminals of the transformer and the neutral wire is attached to the other terminal of the transformer simulating line to neutral voltage. A light bulb is used to simulate the sunlight that is needed to power the circuit. The development of this line detecting circuit is discussed