Inventor Turns to S&C to Perform Temperature-Rise Testing on a Prototype Circuit Bypass Tool.

Jack Jumper with attached thermocouples.

Larski Corporation recently asked S&C’s Power Systems Services to perform laboratory testing on a prototype of their Jack Jumper Cutout Bypass Tool. This tool was developed to provide a convenient means for temporarily bypassing a fuse tube or disconnect blade prior to its removal from the cutout, thus eliminating a power outage to the load served from the cutout.

What tests were performed?

The purpose of the testing was to verify that the test sample could continuously carry 100 amperes of load current without exceeding the allowable 40°C temperature rise permitted by IEEE Standards.

Seven thermocouples were cemented to the tool at various locations from the upper ferrule to the lower ferrule to monitor temperature. The tool was then positioned across the S&C Loadbuster® Tool attachment hook and the hinge of a 15-kV cutout mounting fitted with a disconnect blade.

After energizing the circuit, the disconnect blade was removed from the mounting and temperature readings from the thermocouples were recorded. The initial test current of 40 amperes was maintained until temperature-rise stabilization occurred as defined per IEEE Standard C37.41, i.e., until three successive half-hour temperature-rise readings were stable within 1°C at each location. After temperature-rise stabilization occurred, the current was increased by an appropriate increment. This current was again maintained until temperature-rise stabilization occurred. This process was repeated until a maximum temperature rise of approximately 40°C was achieved.

Additional testing was performed to determine the capability of the tool at higher currents and for shorter durations.

Results

Six current levels of 40, 60, 80, 100, 140, and 150 amperes were applied to the sample and temperature readings recorded every ten minutes. It was found that the test sample performed well at currents in excess of 100 amperes and slightly above.

Conclusion

Since completion of S&C’s testing, the bypass tool has been approved for use at over sixty electric utilities throughout the US. In addition, Larski Corporation has turned to S&C to perform similar testing on a prototype of their 25-kV Jack Jumper.