Use the radio to locate underground cables

Underground cable is a buried power supply line, if damaged, it will directly affect the normal use of electricity. Generally speaking, several cores of a cable are not damaged at the same time. Therefore, one of them can be used to ground one end of the cable and the other end into a single-phase current with zero-line grounding, as shown in Figure (b). By slowly increasing the voltage regulator TA from zero to about 5A and repeatedly operating the knife switch S, the resulting pulse current will follow the direction of the cable, and through the lead envelope, sheath and surface of the cable, the corresponding electromagnetic waves which are very different from the surrounding electromagnetic interference will be generated. With a semiconductor radio as shown in the figure, along the general direction of the cable to be tested (tune the radio to the band without a radio station), you can hear the strongest click, click (when S is on or off) signals, but not far away from the cable. In this way, the actual buried position of the underground cable can be measured by determining the direction according to the strongest signal.