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Digital Circuit Brakers

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In a recent article for Vox, energy and climate change journalist David Roberts makes a case for optimism with regards to our grids going green. You may be asking yourself what’s got old David so excited? Three words: digital circuit breakers. 

First off, he points out correctly, that old fashioned circuit breakers can be dangerous: “they’re slow enough that they still allow lots of short circuits and arc flashes, which can destroy property and even kill people. “Each year in the United States, arcing faults are responsible for starting more than 28,000 home fires,” says the non-profit Electrical Safety Foundation International, “killing and injuring hundreds of people, and causing over $700 million in property damage.”’ Digital switches on the other hand can “meter power, dynamically control amperage based on load, and prevent surges and faults by specifying instantaneous, short-time, and long-time trip settings”. 

However, David is most concerned with the carbon cutting potential of digital switches. The devices will better monitor energy flow and needs, seamlessly responding to needs and cutting back when possible. Digital switches are prohibitively expensive right now, but like technology, they’ll eventually get cheaper.  “Computer power,” says David, “which is always getting cheaper, will help determine how to maintain the same energy services with less labor and material, which are almost always getting more expensive. All analog systems will eventually go digital.”

I don’t necessarily disagree with David about any of this, but I feel like he conveniently leaves out some of the complications associated with the adoption of new switches and other digital utility tools. Namely, security risks. The more advanced a utility’s grid, the larger its attack surface becomes. Smart meters, for example, provide great benefits to utilities, customers, and the environment. They allow customers to take control of their energy consumption, raise reliability, enhance safety monitoring, and greatly facilitate demand response programs through increased data exchange. However, each unit contains the customer’s confidential information, making them targets for cyber criminals and sinister foreign actors. 

Of course, such risks can be mitigated by scaling up security measures. Utility security officers have learned to emphasize segmentation and credentials, and they’ve been pretty successful if the rarity of reported incidents is any indication. 

I’m happy utility issues and advances are getting coverage in the popular press—I just wish there was more nuance.


 

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Discussions

Roger Arnold's picture
Roger Arnold on Dec 1, 2019 8:56 am GMT

28,000 fires annually in the US caused by arcing foults? Wow! If that's true, it's a big problem. But I wonder how many of those can truly be attributed to the response lag in circuit breakers, as opposed to improper wiring? 

A problem with solid state power switching on residential service and distribution lines is that in the past, the devices that were used introduced about a 1.5V drop in voltage across the switch. That's at least a 2% loss of power across the switch, or substantially more for reactive loads. Aside from being wasteful, that's a lot of heat being dissipated within the breaker box. Not really practical.

Silicon carbide power FETs are now available, and they're much better than the IGBTs they're replacing. But they're still costly. And even if they were cheap, I don't think it makes engineering sense to just replace mechanical circuit breakers with fast acting digital counterparts. If one is going to the effort that would be needed to design and deploy digital circuit breakers, it would make sense to integrate power factor correction and signalling that would enable system control of a large numer of individual outlets. 

As to the security risk from deploying a large number of "smart" devices accessible from the internet, that's a real but stupid problem. It stems from the lazy and even inccompetent way that the "internet of things" has been implemented. The embedded processors that control the devices implement fully general internet protocol stacks and operating systems. It's easier to do that than it is to figure out what the device actually requires and strip away everything it doesn't need. But the result is an open invitation for hacking.

 

Matt Chester's picture
Matt Chester on Dec 2, 2019 2:27 pm GMT

28,000 fires annually in the US caused by arcing foults? Wow! If that's true, it's a big problem. But I wonder how many of those can truly be attributed to the response lag in circuit breakers, as opposed to improper wiring?

An important point-- making decisions based on data only makes sense when we know that the data is true and verifiable. Are those assigning blame all using the same criteria to determine and label the causes? 

Bob Meinetz's picture
Bob Meinetz on Dec 2, 2019 4:01 pm GMT

"The embedded processors that control the devices implement fully general internet protocol stacks and operating systems. It's easier to do that than it is to figure out what the device actually requires and strip away everything it doesn't need. But the result is an open invitation for hacking."

Agree Roger, and as I'm often forced to remind software clients: secure digital systems are neither cheaper nor more convenient.  It's what has made Microsoft operating systems less expensive and less secure than Apple ones for decades; it's what allows Thanksgiving hosts to ask "Alexa what's the best white wine with turkey?" from the dinner table, and Amazon to immediately post offers for wine on their Facebook pages; it's why passwords like "Scruffy2013" have been replaced by "8HdzA$x@".

Some argue the facility of open OSes and hardware architectures has facilitated the development of thousands of time-saving, useful apps. It's true, of course, and in the consumer realm "buyer beware" rules the day. But for public infrastructure (and let's face it, despite hype about "markets" and "choice" electricity remains public infrastructure) there is real security in eschewing digital solutions for well-maintained analog ones.

Sure, analog breakers can be hacked too, but it requires the hacker get off his fat a$$ and cut through a chainlink fence - too much work. 

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