DIAGNOSTIC METHOD FOR CABLE INSULATION UNDER HOTLINE

• Main Author: SHIRAHAMA OSAMU
• Format: Patent
• Language: English
• Published: 17.01.1987
• Subjects: MEASURING; MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES; PHYSICS; TESTING

PURPOSE:To correctly diagnose the insulation deterioration of a cable by constituting the DC circuit for DC based on the water tree generted on the insulator layer of a cable separating from the ground. CONSTITUTION:A DC measuring instrument 23 is directly connected with the neutral line 14 of the transformer 13 for ground and the leader line 22 of a mettallic shield layer and the connection point of the neutral line 14 thereof is earthed via an AC filter 26 and the transformer 13, bus 12 and cable conductor 18 are insulated from the ground as a DC circuit. And for the DC source 24 by water tree generated on an insulator layer 19 and measuring instrument 23 becomes in the state of being directly connected with the conductor 18 and metallic shield layer 21 and this DC circuit (loop) is separated from the ground. The current by the local battery 25 of the corrosion resistant layer caused by the insulation deterioration of the corrosion resistant layer 16 is therefore not passed to the loop including the measuring instrument 23. So only the DC current of the DC source 24 by water tree can be measured by the measuring instrument 23 thereafter and so the state of the insulation deterioration of the insulator layer 19 can be diagnosed correctly.