DETECTING METHOD OF OUTER DAMAGE OF CABLE

• Main Authors: SHIRAHAMA OSAMU, NINOMIYA NOBUO, UMEDA SUSUMU, NIIMOTO TAKASHI
• Format: Patent
• Language: English
• Published: 06.08.1990
• Subjects: MEASURING; MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES; PHYSICS; TESTING

PURPOSE:To detect a disconnection of a cable shield in the conductive state by connecting an end of said cable shield not connected to the ground with a choke coil thereby realizing the alternating not-earthing condition, and connecting a capacitor between an end of said cable shield connected to the ground and the ground. CONSTITUTION:A switch 56 is opened, thereby forming a shield disconnection detecting device 38 including a capacitor 36 between an end 16 connected to the ground of a cable shield 14 and the ground. This detecting device 38 is comprised of a direct current power source 40, an ammeter 42, a current adjusting resistance 44, a coil 46 and a capacitor 48 etc. The coil 46 and capacitor 48 together with the capacitor 36 constitutes a filter for blocking alternating components induced by the shield 14. An end 18 of the cable shield 14 not connected to the ground is connected to a choke coil 50 of a high impedance, so that the alternating not-earthing condition is secured. If the shield 14 is disconnected when a direct current is flowing in a loop circuit consisted of the shield 14, coil 50 and ground, the resistance value is increased and the current value is greatly reduced. Therefore, the disconnection of the shield 14 can be presumed in the conductive state while the characteristic of the one-end earthing method is maintained.