Distribution73
Electrical
- Mar 18, 2015
- 40
I am having certain difficulty to understand how the delay Line of the TRV envelope curves specified in standards such as IEEE Std C37.04 is to be interpreted against a prospective TRV for a breaker in a substation.
In the standards ( for example IEEE C37.04) it is explained that this line "establishes a lower boundary for the initial delayed build-up of the TRV wave" and that TRV applied in tests "must be either tangent to or above the delay line to be a valid test stress on the circuit breaker according to its rating".
It is my understanding that the above statements apply to the testing of the circuit breakers, but when we need to assess a prospective TRV curve (for example simulated using PSCAD or ATP-EMTP) against the TRV shapes stablished in the breaker standards I am not so sure how the delay line needs to be considered.
I might be wrong but in principle I cannot see any issue in having a TRV build-up slower than the delay line. In a very interesting reference (https://www.qualtecheng.com/docs/overvoltage-protection/QT-628.pdf) I have found that the prospective TRV (in this case for a reactor limited fault) "should cross the specified delay line, defined by td, u’, and t’, close to zero voltage but should not recross it later". Other than this, I haven´t been able to find much info on how to compare the td line against prospective TRV.
I would appreciate any feedback on how this parameter needs to be considered. Thank you!
In the standards ( for example IEEE C37.04) it is explained that this line "establishes a lower boundary for the initial delayed build-up of the TRV wave" and that TRV applied in tests "must be either tangent to or above the delay line to be a valid test stress on the circuit breaker according to its rating".
It is my understanding that the above statements apply to the testing of the circuit breakers, but when we need to assess a prospective TRV curve (for example simulated using PSCAD or ATP-EMTP) against the TRV shapes stablished in the breaker standards I am not so sure how the delay line needs to be considered.
I might be wrong but in principle I cannot see any issue in having a TRV build-up slower than the delay line. In a very interesting reference (https://www.qualtecheng.com/docs/overvoltage-protection/QT-628.pdf) I have found that the prospective TRV (in this case for a reactor limited fault) "should cross the specified delay line, defined by td, u’, and t’, close to zero voltage but should not recross it later". Other than this, I haven´t been able to find much info on how to compare the td line against prospective TRV.
I would appreciate any feedback on how this parameter needs to be considered. Thank you!