ACSR for substation jumpers

[Power0020]

A 400 kV SS contractor wants to use spared ACSR for equipment and bay jumpers, I have doubts that the ACSR will not be maneuverable as AAC for this purpose, is there any figure to make this feeling mathematically sensible? e.g. minimum bending radius, stiffness, lateral stiffness, birdcaging limit,...etc.

 

[prc]

ACSR conductor is usually used for jumper connections in substations. It is reasonably flexible and serve the purpose. AAC or AAAC conductor is used when the atmosphere is highly corrosive. But these being soft, care shall be taken in installation. Once bent, it cannot be taken to earlier shape.

Some precautions are required in jumper connections. Let me narrate two incidents.

Some 30 years back, HV (220 KV ) bushing failures were reported on a 600 MVA GSU bank. Upper porcelain cracked and bushing had to be replaced. These were RIP( resin impregnated condenser bushings, first time being used in India)Since these were dry type bushings with out oil, bushing failure did not cause a transformer fire. The cause of failure was that the jumper connection was without sag and connected to the middle of the conductor catenary. During wind or short circuit current flow, catenary jumped and oscillated, causing excessive pull on the bushing. When the jumper connection was shifted to one end of catenary problem disappeared.

In another case 400 KV bushing exploded in a large inter connecting auto- transformer (ICT). The jumper connection to bushing was made in hot summer at 45C with out sufficient sag. When winter came, one early morning, at 2C ambient, bushing failed tripping the transformer.

 

[Power0020]

I understand that the AAC can be bent tighter than ACSR without birdcaging issues, ACSR can go with bending radius 12 times conductor diameter while AAC can go with 10 times only. any thoughts?

 

[dpc]

ACSR is commonly used for substation jumpers. Like any other conductor, you need to stay within the bending criteria. I don't see an issue if properly installed. If you are forced to go with reduced bending radius, I'd consider a braided jumper.