Hissing Sound from High Voltage Power Transmission Line: Troubleshooting

Troubleshooting the hissing sound from cable termination just after energization of the high voltage transmission line.

Hissing sound troubleshooting for high voltage underground XLPE cable electrical power transmission line after successful commissioning test. The badly hissing sound coming from the cable termination port area into the panel. Due to the newly constructed line just energizing, so switch off immediately hearing the hissing sound. 

How Troubleshoot the Hissing Sound Problem Coming from High Voltage Terminal Port?

Troubleshooting in any field is not possible to list the troubles that will happen, any new problem may occur at any time. A good troubleshooter actually applies his previous experiences to probabilities. 

We were energizing the newly constructed 33kV underground XLPE cable transmission double circuits line after completing the successful pre-commissioning of all site tests. 

One circuit energized without any problem, but the second circuit made trouble- a hissing sound from the cable termination port panel situated at the power receiving substation. 

We cannot realize the hissing sound for a long time, the client's engineer instructed us to switch off the line without any delay to avoid any provable power interruption in the whole substation.

We actually don't know the cause of the sound and the source of the sound,  is it for faulty cable or cable accessories? or, another reason that is not cable lines related.

A similar problem happened in another 132kV power cable project after an energization hissing sound was coming from the cable sealing end termination at the gantry area, finally, we troubleshoot that there is no problem with cable lines or cable accessories, a simple problem is in cable sealing end support steel structure, there was a loose bolt on a structure that was vibrating due to energized line and generating hissing noise.

 So, we attempted to troubleshoot and the first step was to physically check. Our target is to find something that remains loose contact because if the cable or cable accessories like cable termination are faulty, it never gives time to switch off the line, it becomes shut down by itself immediately.

Opening the cable termination port panel and primary observation, we found that the technician made some mistake to earth the dummy plug connection. 

Look at the picture, you will find the difference between before troubleshooting and after troubleshooting. A green-yellow grounding conductor for the Blue Phase dummy plug at the right end is missing.

After connecting the grounding wire correctly as in the right side after-troubleshooting picture, we switch on the circuit again, and operating successfully.