Does SF6 degrade with number of CB operations
Does SF6 degrade with number of CB operations
(OP)
I have jus had an 11kV SF6 Circuit Breaker flash on our plant in a manner that suggests that either there was loss of SF6 the quality of th gas had deteriorated therefore loosing some of its critical properties. Because the tests showed that there was no loss of SF6 I would like to assume that there was deterioration. Is this a correct assumption and if so what are the facts relating to SF6 degradation with Circuit Breaker operations?






RE: Does SF6 degrade with number of CB operations
RE: Does SF6 degrade with number of CB operations
However water and air molecules in the gas can combine with the contamination and eventually lead to a dielectric breakdown.
Jasjit Khangura P.E.
Electric Distribution Engineer
RE: Does SF6 degrade with number of CB operations
You may try posing the question to an operation like that at www.actiinc.com. They conduct a number of procedures for SF6 evaluation in electrical environments, including decomposition and dielectric tests.
RE: Does SF6 degrade with number of CB operations
DanDel - We confirmed that the tank had SF6 by checking the tank gas pressure before removing the gas from the tank to enable us gain access to the CB contacts.
busbar - I have sent a querry to ACTI. I'm yet to hear from them. Thanks.
The CB manufacturer's representative on site has indicated to us that the CB may have done its expected number of operations. They are yet to confirm the expected number of operations and what deterioration is expected.
RE: Does SF6 degrade with number of CB operations
RE: Does SF6 degrade with number of CB operations
If there has been leakage, there could enter moisture inside, many CB manufacturers of HV CBs use dew-point meters for evaluation of gas contamination (with moisture).
RE: Does SF6 degrade with number of CB operations
You guessed right. Our minds were in some kind of auto pilot: "Something has mechanically gone wrong with this CB, lets open it and check what we shall find."
We took the gas out and opened the tank only to find a flash and a general layer of carbon. Mechanically, the internals, including the contacts, were okay apart from the carbon layer.
The switchgear manufacturer has since taken the CB away for rehabilitation so I cannot do any more tests. I will just have to wait for their report. Any thoughts and pointers will still help a lot
Thanks
RE: Does SF6 degrade with number of CB operations
RE: Does SF6 degrade with number of CB operations
RE: Does SF6 degrade with number of CB operations
Who was the manufacturer and what is the model of the C/B?(if you don't mind sharing that info)
RE: Does SF6 degrade with number of CB operations
RE: Does SF6 degrade with number of CB operations
RE: Does SF6 degrade with number of CB operations
1. SF6 insulating deterioration while the voltage was within the circuit breaker design basis
2. The voltage experienced a spike or surge that caused the flash.