Monitoring electrical cables and joints for the ingress of moisture

摘要

Two detecting conductors such as moisture detecting tape 2 with two metallic conductors laminated to an insulating substrate are secured in or to the cable and terminated in a fixed resistance 6. The terminating resistor causes a small current to flow continuously through the detection conductors and should the line open resulting in a loss of protection, the absence of the monitoring current will signal an alarm indicating a system fault. The ingress of water into the cable system will result in an increased current in the monitoring line which is then detected by the remote electronics equipment and an alarm is activated. Coded signals are used to indicate the position of a faulty splice, and to effect isolation of a selected cable portion.