Synchronization of on-line PD detection and localization setups using pulse injection

The development of an on-line PD detection system has its main challenges in the area of sensors and signal processing techniques. If localization is included by means of simultaneous signal detection at both cable ends, the problem arises of synchronizing the measuring systems at both sites accurately. One method, already successfully applied in off-line PD measurements, is the use of GPS. Besides its high costs, this system has one main disadvantage: it requires an external antenna in the line of sight of several satellites. This requirement may be a problem for on-line measurements because of the long measuring time. Another option to perform the synchronization is the injection of high-frequency pulses into one cable end and detecting them at the other end. Taking the propagation time along the cable length into account, this results in accurate synchronization of the measuring sides, without being dependent on any other system. This paper discusses several aspects of the pulse injection technique. The obtained resolution realized during field experiments with the method of pulse injection is within the resolution obtainable by means of GPS (100 ns).