Based on an Engerati co-sponsored webinar, S&C Electric Company’s Christopher McCarthy demystifies pulse closing technology.
S&C Electric Company first installed its IntelliRupter PulseCloser Fault Interrupters, which support pulse closing technology, in 2008. It has since deployed many thousands of the devices on systems around the world, primarily in North America, South America, and Australia.
With pulse closing Technology, a minor loop of current is created from the power system voltage that lasts five to 10 milliseconds, says McCarthy. Moreover, it uses about 95% less energy to test for faults than typical reclosers do, preventing damage to transformers and other expensive assets on the line.
S&C’s IntelliRupter fault interrupter has three magnetic actuators, similar to those found in a recloser or a breaker. But these close at a specific point on the voltage wave.
The actuators open a vacuum bottle, creating a very repeatable, low-magnitude pulse of current the IntelliRupter control can analyse to determine whether a line has faulted.
The original concept behind the IntelliRupter PulseCloser Fault Interrupter was to have a smarter way to determine whether a distribution line has faulted. From there, many different applications became apparent.
For example, with the introduction of two-way power flowing on a distribution line through renewable generation, pulse closing technology can prevent a scenario where every fault on a feeder knocks off 50% of the distributed generation, causing downtime and further complicating grid control.
As S&C’s Christopher McCarthy explains during the webinar, you can put pulse closing units at the beginning of a transition point to the overhead or underground system and position three, four, five, six, seven - or even more of these on the line.
When a fault occurs, the closest one will be the one that trips first. If the device is on the overhead system, it will pulse, realise the fault isn’t there, and then close and hold to restore. If it's on the underground system, it could still pulse once, twice, or three times to see whether the fault is still there.
“Eventually, one of those devices will lock out for a sustained fault, and that will tell you it's on the overhead or the underground system,” McCarthy says. “Basically, the type of circuit - whether it's overhead or underground - is not really an important factor when you're using pulse closing technology to do the protection.”
Pulse closing units have more capability than a standard recloser or breaker, so with any technology that has more capability, it is going to cost more. Using reclosing and closing practices, however, puts distribution equipment such as splices or connectors under thermal and mechanical stresses from the faults, making them more likely to fail sooner.
“If you look at what it costs to deal with that and compare it to the extra price for getting pulse closing technology up front, you can start to make a real compelling case,” says McCarthy.
Some customers want the advanced features and use just a couple of the IntelliRupter fault interrupters for a situation where reclosers wouldn't work. Other utilities have standardised on this product and say “this is the one we use for all of our distribution protection,” and they no longer use reclosers, says McCarthy.