Responsiveness matters. And in the case of managing the grid—doubly so. In this video, we’ll look at how latency affects operational safety and how to measure it accurately.
Hi, my name is Ryan Chatel and I’m a senior product manager for Sensus. I want to talk to you today about a really key topic for Distribution Automation, the effect of latency on grid operations. It’s not what you might think, so let’s continue. Let’s see what we have. So first when I say latency and I say operations, I mean the SCADA operator, and I’d like to offer you a different definition on the term latency.
I’d like to offer you the definition of what it really means to that SCADA operator. That is when they push a button until they see a point change. That’s what I mean, end-to-end latency. The SCADA operator goes to open something and it opens that’s the effect of latency on grid operations. So it turns out that that pings or hops or even direct messages to devices, they really don’t matter.
At the end of the day, what really matters is that point change experience to the SCADA operator. So let’s get down into the weeds a little bit. A SCADA operation can occur either as a direct operate or a select before operate. And so, as you see here in the slide, this is a select before operate, and there’s a lot of little transactions that can actually occur that are behind the scenes.
But again, none of those really, really matter to this SCADA operator. The SCADA operator cares when they push the button, did it happen or not? And so what you’re going to see here is that all of these things in gray, like the select act, the operate, the operate act, and maybe solicited responses are all nice. And of course we need them, but at the end of the day, when I pushed the button and when it changes is all that matters.
So how long do you think this should actually take on a wireless network? Again, it’s wireless? So the answer is certainly not milliseconds because well, physics. So you’re going to need to take a look at the total number of seconds that it takes. And you also have to consider the amount of time that a polling that SCADA will poll the end device. So it doesn’t support unsolicited report by exception, or is it polling? So all of these decisions are need to be taken into account when you’re operating a device and trying to really satisfy that end user.
The thing that I want to impress upon you is that latency should be measurable and consistent. And it turns out that measure measuring and consistency is really, really important. So why does latency even matter? Well, besides that we all want it fast and we all want it real time.
It turns out that there’s actually a safety component to the latency. That is if a SCADA operator pushes the button to close a recloser by the time it gets down there closes and comes back. If that SCADA operator is used to say five seconds, if after five seconds, what do you think that SCADA operator is going to do? The SCADA operator is going to push the button again, and that wreaks havoc, if it’s a toggle.
So if those and programmers and IED configurators have programmed to toggle, then the SCADA operator has just undone what he wanted to do all because latency was a problem. So latency is a safety consideration. The SCADA operator has this learned behavior. And also there’s a safety feature of commands need to have this notion of expiring because if the command lives on for a certain amount of time, that could be very dangerous.
If you have to send a field crew to a piece of equipment, you certainly don’t want any latent commands operating when the operator is, or when the field crew is there on the line. So latency also matters with respect to your industry metrics like MAIFI, SAIDI and CAIDI. Another hidden little trick that some vendors will do is they’ll play the time source game. It’s like, which one of these is going to be the time source. And it turns out that you can actually have different time sources and your latency might look a certain way if there’s two different sources of time source.
So making sure that everything is synced to the same time source and holding vendors accountable to that is also really, really key. The other reason why latency matters is in the case of an event, an under frequency event or a real life situation, where you have to shed load, you can’t have devices, retrying and hopping around and all of these different things.
When there’s a real situation on a line, it needs to happen and it needs to happen now, and it needs to happen consistently. And that is the difference. So, a couple of questions that I want you to think about as you explore your distribution automation offerings. re all the command types equal? How does the vendor manage the different types of commands? What about different types of outbound transmissions, like timesyncs or pings across the network for signal strength or whatever the case is. Are all of those equal?
There might even be the notion that operations has different fundamental needs than engineering. Engineering may need to change setting changes on a capacitor control, whereas the operator simply needs to open or close that cap bank. So you need to start to look at all of the offerings that a vendor offers with respect to all these different types of scenarios.
So can SCADA operators actually measure the latency? Can those SCADA systems actually measure them and can they be improved? So the time stamping we already talked a lot about, but it does play a key role. So my takeaways for today latency is the hidden hero or the villain. So you need to make sure that you’re investigating your networks and making sure that distribution automation is absolutely a key differentiation thing, when you’re thinking about which network to select.
And also it’s not measured all the same when you talk to different vendors there, there’s not a lot of clarity around how latency is measured, but again, I offer you the vendor neutral perspective of when I push the button, how long does it take for that operator to see that point change? Because at the end of the day, it does impact reliability and safety. So if you can improve latency, your MAIFI and your CAIDI will also improve, which means money is saved.
So with that, I leave you. Thank you so much for watching. My name is Ryan Chatel…come by and visit us at Sensus.