Development of cable locators for control cables

摘要

In power stations and substations, central control panels are connected to other equipment by thousands of cables. These cables go through the walls and the floors by several hundred meters from several meters long. Under such conditions, a cable locator that can locate cables among thousands outside the control room is desirable. Usually electromagnetic induction-types, or electrostatic coupling-types (a pulse wave-type and a sinusoidal wave-type) are used as the cable locator. But both are not applicable when the far-end of the cable is not accessible. The cable can not be located by the electromagnetic induction-type when the conductor is not connected at the far-end by the ground or the conductor of the adjoining cable and a loop is not formed. With the electrostatic coupling-type {sinusoidal wave-type), if the conductor is grounded at the far-end the cable can not be located. If the length of the cable is fully long, it can be located with the pulse wave-type regardless of the condition at the end of others. However, it can not be located with the short cable, because a signal is denied by the negative reflection pulse wave from the far-end. To overcome these problems, we have developed a cable locator, which can locate a cable when the conductor of the cable, is either grounded or released at the far-end. The cable locator is used with an electromagnetic induction-type and an electrostatic coupling-type together. It can locate without switching from electrostatic coupling to the electromagnetic induction.