Insulated Shorting Cables
There are 2 types of cables used in the electrical industry: grounding cables and insulated jumper cables. Insulated Temporary By-Pass Jumpers are used to temporarily connect a device or system to a hot power line. For this type of jumper, the insulation is of paramount concern. The end connectors are usually of a type designed to be installed and tightened using a hot stick with the appropriate attachment. Alternately the end connectors can be intended to be installed with gloved hands. The cable gauge needs to be sufficient to handle the expected load with the appropriate safety margin.
While ASTM F2321 (Standard Specification for Flexible and Rigid Insulated Temporary By-Pass Jumpers) does not recommend a specific time interval for testing these types of cables, OSHA and other agencies recommend annual testing.
We follow the practices listed in ASTM F2321 (Standard Specification for Flexible and Rigid Insulated Temporary By-Pass Jumpers) when doing insulated jumper testing. These cables are first cleaned. The insulation on the cables is wiped down with an appropriate cleaning agent to remove most grease and dirt. This will allow the cable part of the assembly to be examined for mechanical damage. Then the connectors are cleaned with a wire brush. This will remove dirt and oxidation from the jaws of the connectors. The cable is then hung in the high voltage tester, and the ends (the connectors) are connected to the high voltage points. The machine then takes over by closing and locking then enclosure, turning on the high voltage, and dipping the cable in the dielectric fluid. The voltage is applied for 1 minute. If no leakage occurs above the current limit during the one minute, the unit is considered to pass the test. It is removed from the high voltage testing machine, cleaned, dried, and marked as passed with the current date and the expected next test date and the voltage rating (based upon the applied high voltage). The jumper is then carefully packed for shipment prior to being returned to the customer.