After simulating the IEEE-39 Bus System Benchmark in EMTP-RV software, I introduced faults in the 500 kV transmission system at its various bus locations (one at a time). I am observing very high fault current magnitudes in the connected Transmission Lines . Can someone please specify how much increase in the magnitude of the fault current is deemed to be acceptable when compared with the current magnitude of the normal system operation? Thank you
Dear Sir,
you can consider that, for a 500 kV application, widely available circuit-breakers can clear 50 kA short-circuit currents. Circuti breakers with higher breaking capacity could be also considered; however an higher short circuit current (say 63 or 80 kA) has a large impact on the cost of all the station equipment (and grounding installation). As far as I know, the 50 kA limit is widely considered by utilities.
As far the load current is concerned, you can consider that the SIL current of a 525 kV transmission line is around 1.1 kA, therefore the rated load current could be limited at 3.15-4 kA (2800-3600 MVA).
Best regards, Giulio Santagostino.
Dear Sir,
you can consider that, for a 500 kV application, widely available circuit-breakers can clear 50 kA short-circuit currents. Circuti breakers with higher breaking capacity could be also considered; however an higher short circuit current (say 63 or 80 kA) has a large impact on the cost of all the station equipment (and grounding installation). As far as I know, the 50 kA limit is widely considered by utilities.
As far the load current is concerned, you can consider that the SIL current of a 525 kV transmission line is around 1.1 kA, therefore the rated load current could be limited at 3.15-4 kA (2800-3600 MVA).
Best regards, Giulio Santagostino.
Breaking capacity of breaker. Could be made economical by providing current limiting reactors. Burned transformer with open secondary could be utilized as reactor...
What are the values of your short circuit current calculations? Rated current for 500 kV lines depended on how many conductor per phase are installed, it can be between approximately 1000 A to 3000A. Short circuit current for metal three phase can be to 40 kA or even 50 kA. Those values are also rated values for high voltage circuit breaker, which are typically available on market. Other higher values for breaking short circuit current need to have special circuit breaker. Values above 40 kA or 50 kA have also impact on others elements in transmission system, like Mr. Giulio Santagostino mentioned. Higher values for SC current push you to implement special designed for other transmission elements, disconnectors, power and instrument transformer, busbar design, insulator, etc. Roughly, those values can be the limits for current calculations in your study work.
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