How Do Underground Power Line Detectors Work?
The basic principle on which, the underground power line locators work is very simple. A cable that has AC power passing through it generates signals of its own in the frequency level of 50 to 60 hertz, jointly with greater frequency signals; this concept provides a foundation for finding the buried lines with the help of a passive receiver.
The earth is filled with power frequencies circulating between the earth connection spots and cables. These currents follow the path of the underground metallic conductors automatically providing minimum resistance. They are also united with them by making use of induction and capacitance. Thus, a range of 50-60 Hz waves and their harmonics up to around 3 KHz are there on the underground cables as well as on the surface of most conductors in the vicinity. This means that lines that carry power frequency waves can be located, but they cannot be identified by inactive signal location. The signals may be from a live wire, concrete reinforcing bars or a pipe, but the presence of a conductor is confirmed.
Single phase cables normally radiate clear waves, but with the case of three phase power cables, there is difference between the phase loads; this unbalance is due to the tendency of balanced currents to cancel their fields. As the balance improves, it becomes more difficult to detect the power lines. High voltage loadings like the ones for street lighting are better balanced; these can be easily detected by utilizing the option of passive search in ‘P’ (power) mode.
However, sometimes live unloaded cables may be present; such cables do not radiate any power signals. To detect such cables, there is a radio mode option on the detectors which adds up as a great complement to the power mode. The radio frequency signals in this mode helps in detecting the existence of a conductor. Hence, detectors can be used in radio mode for detecting dead power cables which may go undetected in the power mode.