Surge Protection & Outdoor Lighting Applications w/ Littelfuse

Introduction

Adam: This is the Wisconsin Lighting
Lab podcast. My name is Adam Rupp, and today my guest is Marc Hubbard. He's a
field applications engineer with a company called Littelfuse. Marc, welcome to
the podcast.

Marc: Thank you, thanks for having me.

Adam: Absolutely. Let's start out —
give me a few background details on Littelfuse, where you guys position
yourselves in the market, and your background in the industry.

Marc: Sure. Littelfuse is over a
90-year-old company, and we kind of grew out of circuit protection. We
currently have the broadest and deepest portfolio of circuit protection
products in the industry. We're also accelerating our growth in other
synergistic areas, including power semi, control products, as well as sensing
devices. From a circuit protection standpoint, because of the breadth of our
product line, we offer anything to protect anything that uses electrical energy
— applications that are connected to AC mains, DC power ports, as well as
telecommunication and datacom interfaces. We also cover several different
markets because of our breadth of product — anywhere from consumer to
industrial to automotive, medical, mil-aero, and of course lighting.

Adam: When I think about the
electrical grid and why a company like Littelfuse exists, I think oftentimes
it's misunderstood. We all use electronics products, whether it's at our homes,
in our businesses, pretty much anywhere. When you look at power generation,
power distribution, and then local power distribution panels — what is the need
for protecting circuits and for protecting products, in your mind?

Marc: There are several different
kinds of faults, and we're trying to protect against certain abnormalities that
can occur on the grid or on the line. We offer products that protect for
over-current situations — that's really more like a short-circuit fault or a
ground fault. But also on the grid there are surge events that can occur. A
surge event is essentially a short-duration release of electrical energy, and
this can cause large spikes on the line that result in high voltages. They
typically will last anywhere from a few microseconds to maybe several
milliseconds, but they can cause all kinds of issues or damage — anywhere from
a soft failure such as a latch-up or malfunction of the equipment, all the way
to component failure or even a potential safety issue for the user. So it's
important to ensure that you have the proper protection on the lines — one, to
keep your equipment operating, because anytime you have down equipment, that
becomes costly, as well as the cost of having to actually do the repairs.

Circuit Protection: Where to Start

Adam: All electronic products are
built to a certain electrical spec. They're designed to work with a certain
voltage, a certain amperage, within a certain tolerance. And in many cases, by
the time the power gets to the product itself it's out of tolerance — it might
be out for a brief second, or you might have certain instances where utility
transformers are out of their operating tolerance. When you guys are protecting
circuits and products, where do you start? Do you start at the distribution
panel within a building? I know we also use some of your products on board with
our fixtures — your breadth of products, where do they start in the circuit
itself?

Marc: It's a good question, and really
it starts at the service entrance — from the service drop from the utility down
directly into the building itself, as well as in the distribution panel for
both over-voltage and over-current. At the distribution panel you have branch
protection or over-current protection to protect against any type of ground
fault, which is really there to prevent fires or potential shock hazards, as
well as transient events that can occur. Having something at that service panel
or distribution panel is kind of the first line of defense into the facility.
Typically though, that's only going to protect you to a certain level — it's
designed to handle a large amount of energy, but even at that point there's
still going to be some let-through energy, because it's only going to protect
down to a particular level. So it's also important throughout the system itself
that you have protection at different points, whether it's at the distribution
panel or even at the end equipment. By the time it gets to the end equipment,
hopefully that energy has been knocked down to a good level, but you still want
to ensure your equipment is well protected against any let-through energy that
might occur.

Circuit Protection & LEDs

Adam: Over the last year our
engineering team has been doing a deep dive into surge protection — and really
power management in general — as lighting has transitioned from the legacy
technologies (HID, fluorescent) to solid-state technology. I think people are
starting to realize how much more susceptible those products are to transient
voltage events. What we've done is taken a holistic approach to it rather than
just focus on our lane, which is manufacturing product. If our products are
being plugged into complicated electrical systems, we really need to understand
everything from the panel all the way to the product that could be 80 feet up
in the air. When you talk about that cascading protection — it's panel, and
then for a sports application it would be the base of the pole, then on the
fixture itself, right?

Marc: Yeah, you bring up a good point.
Especially considering legacy lighting like high-pressure sodium — those types
of technologies are very robust.

Adam: Why is that the case? Is it
because the ballast was transforming the voltage and was able to handle more of
those transients? Why is that technology more robust?

Marc: It's just the way it was set up
because of the ratings or the levels of energy those types of technologies
could handle — either short duration or even handle certain low-voltage
situations. But when we start to move to solid state, solid state by nature is
more sensitive, and that's where the LED lighting comes in. That's what I think
a lot of people started to realize as we started to transition into LED
lighting. The benefits are great — you get lower power usage, you've got
long-term reliability — but especially in an outdoor application, to realize
that long-term reliability that you can get out of that fixture, you have to
make sure it's protected and can hold up under transient events. Because of the
greater sensitivity due to the solid-state nature of it, you are going to need
to start adding in some extra protection to make sure that you're going to
achieve the longevity you're trying to get out of this new technology.

Adam: It's funny too — historically, I
think when LED light fixtures have issues, a lot of people's knee-jerk reaction
is to blame the driver. “The driver has failed, it must be a bad driver, must
be overheating.” There's a whole host of reasons people thought it was failing,
and I never liked that explanation, because in my mind it's a symptom, not the
cause. You really have to go further upstream to understand why the driver is
failing. As we started to dive into it, our investigation didn't even stop at the
pole level — you went back to the distribution panel, then you realized that in
some cases people aren't measuring the output of the transformer. Especially
for mission-critical applications — sports lighting, high-mass lighting,
applications where the products are tough to service — having that holistic
approach is important.

Marc: It really is important, because
a lot of times that's where these issues are coming from. They're coming from
the grid, from the electrical system, and if you don't have a well-regulated or
reliable system, that's going to start to wreak havoc on the equipment that
you're attaching to it.

Indoor vs. Outdoor Circuit Protection

Adam: You talked about outdoor
applications being more susceptible. I think I look at indoor applications too
— when I walk through industrial plants, even hospitals, other types of
facilities that have had solid-state electronics for decades, you look at CNC equipment,
you look at robotics automation equipment — people in that business have known
for a long time that for this piece of 10-million-dollar machinery to operate
properly, it has to get good power. So did you guys learn a lot of your
expertise in those types of applications, and now it's getting applied to
lighting? What other types of jobs, indoor and outdoor, do you see where the
same type of tender loving care needs to be given, just like lighting products?

Marc: Yeah, it really did kind of grow
out of what we have experienced in the industry. It's funny when you talk about
indoor applications — like you said, those have been around for a long time,
we've been protecting those types of devices for a long time. But the exposure
level that you generally have in an indoor environment is a lot different than
you're going to have in an outdoor environment. One, it's in a building, it's
in an enclosure, which is going to help limit some of the transient events that
can be ingressed into the facility. Not to mention you have the upstream
protection at the service entrance, and then that propagates down into the
protection at the equipment level. So generally you don't need something as
robust as you might need in an outdoor application. When we start talking about
outdoor applications, now you're out in the environment and you have a much
higher exposure level. The other issue too is, generally you're going to have
long runs of cables. Maybe in a facility you only have a short run — 30 meters
or 30 feet — but when you get outdoor, now you're talking hundreds of feet of
cabling being run from the distribution panel to the pole, and then even up the
mast to the light fixture itself. That in and of itself becomes an exposure
point. When a lightning event occurs, the amount of large current flow that
goes through the lightning creates a large electromagnetic field, and that gets
coupled onto the cabling that's either above ground or below ground. So if
you're on a transmission line, that gets propagated into the facility where it
meets the primary protection and gets propagated down the line. Whereas in an
outdoor scenario it can even be propagated past the distribution panel into the
cabling that's running from the distribution panel to the light and even up the
pole. So it's even more important to have a level of protection at those
different locations.

Adam: So at the distribution panel,
you're making sure the incoming power is regulated between the transformer and
the panel itself. From there, let's say a sports application, between the
distribution panel and the light pole itself, you'd want another combination of
surge protection and fusing at the base of the pole, to protect that circuit
underground between the panel and the pole. And then on board at the fixture,
you'd want a layer to protect anything that happens between the base of the
pole and the top. Would that be a general architecture?

Marc: That's a general architecture.
Plus it's also the stuff that can occur within those locations — but also, if
it occurs on the mains, through the distribution panel, there's still some
let-through energy that gets through. So you're also trying to protect from a
mains event that gets propagated through the line. It's really twofold in the
way that you're trying to protect.

Adam: Got it. Do you guys do anything
with voltage sag, or is it pretty much on the surge part of the problem?

Marc: We really don't — that's an area
we don't really deal with: regulation or noise or voltage sag. There are some
impedance devices that can be used, or filters that are typically used to deal
with those types of events. We're really more focused on the transient or surge
event protection level.

Electrical Impedance Testing

Adam: When it comes to electrical
impedance, I know we've had some of our systems tested just to ensure that —
say there's a parallel-wired surge protector on board the fixture — we know
there have been some cases where if there is a transient event, it still will
affect the driver before it affects the surge protection device. What type of
testing do you do to make sure those impedance values are matched?

Marc: That's something we found too as
we were growing in this industry. We discovered there's a coordination issue
that can occur between the external module protection used in the fixture as
well as the protection that's used internal to the driver. The drivers
themselves have a certain level of protection — this can be anywhere from 4 kV
to 6 kV. Typically there are some that are looking at 10 kV, but usually 6 kV
is about as high as they will go, which is fine for an indoor lighting
application. But as you move that outdoors, that becomes insufficient to
protect against the type of events you might experience. That's why you use a
module on the outside. The problem is, depending on how those match up —
whether it's their voltage rating or the amount of impedance that's in between
— it could still end up that too much energy (not all of the energy, but too
much) still gets pushed through the driver itself. For instance, if the voltage
rating is slightly lower on the surge protection that's in the driver compared
to what's used as the module, it will turn on first and it will start to take
more of the energy. Therefore you're still dissipating some energy in the
module, but it's not limiting enough to protect the driver. There are things
you can do to try to help with that, and the main thing is to make sure there's
enough impedance between the two devices, or coordinating impedance or
inductance. It's not really practical to add an inductor in line, but sometimes
the cabling itself will offer that level. The other option is really just to
test it with the driver to ensure there is coordination between the module
you're planning to use and the driver you're planning to use. We've also done
some development where we've added in some extra electronics into the module to
reduce the amount of let-through voltage to help with that coordination issue.

Adam: What type of testing equipment
would you recommend for contractors who might test the panel surge protection
versus some of the other electronic components, and for factories that are
manufacturing product? Once they have their system architecture in place, if
they wanted to test and match the impedance values between the surge protection
devices and the drivers, what's available for factories to test those systems?
I know we do a hi-pot test, but I believe that doesn't necessarily test the
surge protector versus the driver — I believe that's testing just the ground
continuity in the system. What other equipment might be available?

Marc: Ground continuity is important
and helps, but a hi-pot is really more of a test of the insulation resistance
of a system. It doesn't really help test against transient events — lightning,
or EFT, or inductive switching events. To do those, you really need to test in
a lab, using things like a combination wave generator (which is designed to
simulate a lightning strike at different voltage levels), as well as an EFT
tester (which is designed to test switching of inductive loads on a system or
on a line), as well as some ring wave testers. And if you're going to do that
in a lab, typically you want to do it as it's connected to the AC mains,
because where it happens on the phase of the AC cycle can have an effect as
well. So typically you'll need a coupler/decoupler network to attach the power
to the fixture itself but isolate the transient from the rest of the electrical
system, so you don't cause any additional damage.

Adam: So it sounds like you have a
relationship with a good lab — it might be a little complicated if we try to do
all that on our own.

Marc: That's something we can help
with. We actually have a lab in Chicago, and we have a couple more globally,
where we can do this type of testing. If you can provide us with the fixtures,
the drivers, or things like that, we can help identify if there's going to be a
coordination issue with the particular topology or setup that you're using.

Adam: Very cool.

Surge Protection Best Practices: Sports Lighting

Adam: Rules of thumb — let's focus on
outdoor sports applications. We work on a lot of jobs. It could be a
recreational ball field where the electrical infrastructure has been there for
40 years; the transformer might be several decades old. If you are in charge of
specifying electrical protection equipment for that type of application, and
it's a customer that might be on a budget, a contractor that's in charge of
sourcing all the electrical hardware, what are the rules of thumb you would
use, starting at the panel itself?

Marc: I think it's probably best to
refer back to some of the standards that have been developed that provide
guidance.

Adam: Is that NEC code, or standards
above and beyond?

Marc: NEC is sort of the base-level
standard, but a lot of times we'll reference different standards when it comes
to certain aspects of the electrical event and how to test for it. For
instance, IEEE C62 is one of the primary standards used for developing a simulation
waveform or test for lightning or other types of transients. Usually they'll
pull from that to say, okay, here are the test levels, here's the waveform, and
these are the types of things that you could experience. If you meet that,
you're in a much better position to be able to survive these types of events
once you hook them up to the field. Granted, in the field it's all over the
place — they've done a lot of studies of systems and grids, whether it's
lightning activity or switching, and that's how they've developed these
simulation standards or guidelines on how to test to ensure that your equipment
will hold up.

Adam: In terms of the product itself —
say it's an off-the-shelf surge protection device — what should a contractor
look to source if they want to take care of all those potential issues? Would
that end up being a Type 2 or a Type 1 surge protection device that gets hooked
in parallel at the panel? If you had to cut through all the noise and just say,
this is the part that you would need, and assuming it's installed properly it
should take care of 80% of the issues, what type of device would that be at the
panel?

Marc: At the panel itself, primarily
I'm going to be looking at a Type 2 SPD. That's anything that's going to be
connected on the output or the load side of the distribution panel — it'd be a
Type 2, per the UL 1449 standard.

Adam: Perfect.

Marc: The Type 2 device though can
have different levels of capability. For instance, if you look at the standard
from a surge aspect, it can range anywhere from 5,000 amp capability all the
way up to 20,000 amp capability. So if you're unsure of your system and how
well regulated or how well protected it is, then you may want to go to the
higher end of that level to ensure you have the best level of protection. If
you know that it's a pretty well-controlled line, then maybe you can go down to
the lower-rated SPD. Type 1 is actually at the service entrance, so that's
really kind of in front of the distribution panel or the meter. So that's a
different sort of aspect, and those are typically going to be either 10kA or
20kA-rated devices.

Adam: And then at the base of the
pole, what type of device would that be?

Marc: You can also look at a Type 2
protection there, or you could even potentially look at something that's more —
these are considered Type 4. These are modules; generally they're used in the
fixture. You could also consider using them at the base of the pole for some
added protection. At that point it doesn't necessarily have to be a Type 2 or
Type 1 rated device, because that's really more what's required at the
distribution panel. The standard calls out that once you go beyond 10 meters or
30 feet, then it starts to become a Type 3 protection device. There are some of
those available too that you might consider using at the base of the pole,
which is more of a Type 3 level — a lower rating. But given that this is an
outdoor application, you still might want to consider a higher surge level,
probably in the 5kA to 10kA minimum.

Adam: Bigger is better.

Marc: Yeah.

Littelfuse Solutions

Adam: Do you have a suite of products
— bolt-on products — or are your components going into other products?

Marc: A little bit of both. As we
talked before about Type 1 SPDs, that's really a piece of equipment, and an SPD
has different aspects to it. One is its ability to protect against surge;
another is it has over-current capabilities, whether it's an intermediate
current or short-circuit current level. We provide the components that go into
those devices. So primarily you're going to find something like a metal oxide
varistor (MOV) product — this is going to be the primary surge protection
device used in an SPD.

Adam: Or surge protection device
that's inside that module, correct?

Marc: And that's also what's used
inside these as well. They're also the type of devices used inside Type 1 and
Type 2 surge protection devices. Then we also offer sort of assembled devices,
which are more what you see here, designed specifically for the lighting
industry for outdoor fixtures. These also include suppression components as
well as some other mechanisms — a mechanism for thermal protection, and in some
cases (like with the coordination issues) we'll add in some TVS diodes or GDTs
for isolation. So it really just depends on what the requirement is of the
system.

Adam: Do you do anything with power
monitoring — surge or spike counters, or other types of voltage and power
monitoring?

Marc: We really don't. There are power
system analyzers that can be used to measure not just spikes but also power
quality — whether there are variations in frequency or voltage, or sags or
swells. You can collect that data in real time. Surge events are a little more
tricky because they're more infrequent, so they don't happen quite as often.
Usually something like a data logger can be used that will take measurements
over a long period of time, and then you can analyze that data and see what
your transient activity looks like. That could give you a much better idea of
what level of protection you might need for that system.

Adam: Where do you see things going in
the lighting industry with your product suite? Are you guys developing more
products to solve these issues, or are you comfortable where things are at
right now? What does the next few years look like from a product standpoint?

Marc: It's been kind of a growing
process for us. This was kind of our first entry into the lighting protection
system where we integrated into a module like this. As we've grown with the
industry, we've come across different needs. For instance, that was primarily
just an MOV-type protection, but as we started to look into the European
territory, you can't connect MOVs to ground in certain systems, so we were
adding in GDTs to provide that isolation. As well, with the coordination issue,
we're adding in TVS diodes and some inductors to try to cut down that voltage
level, so we're limiting the amount of energy that goes into the system. The
industry is also very price sensitive, so we're doing other things for
customers depending on the need — that may be a shrink-wrap version, not as
much functionality, but still provides the protection requirements that are
needed. We're adding in indications, so one of the questions we keep getting
is, well, how do we know that the module has failed, or how do we know if it's
the driver? So we've added in some LED indications that provide an indication
of whether the module itself is still functioning or if you've lost surge
protection.

Adam: So in that case, if the light is
out, it would mean the module is no longer functioning, correct?

Marc: Typically, if the light is on,
the module is functioning. If the light is off, the module is bad and needs to
be replaced.

Parallel vs. Series Wired Surge Protection

Adam: I know there's a big debate on
parallel versus series wired surge protection. The best system from a
protection standpoint, I believe, would be series wired, where if the surge
protection device fails, it protects everything downstream. But if it happens
on day one after an install, that might not be a good thing either. Where do
you guys see customers headed from that standpoint, or what do you typically
advise customers to do?

Marc: It depends on the school of
thought and what the customer is looking for, because there are advantages and
disadvantages of each. In a parallel connection, if for some reason the module
goes out and you don't have surge protection but your light stays on — for some
customers, that's important. They want that light to be on as long as possible
under any circumstances. You're exposed to the next transient that's going to
come down the line, but that transient may not occur for some period of time,
therefore it may not be an issue. Whereas other customers are okay with: if I
don't have surge protection, I want to protect the driver, and I want to know
that it's out so I can service it. That's where a series module really comes
in, because if it goes offline, it takes the entire fixture offline. Therefore
it's protected from another transient because it's isolated from the AC mains,
and the light goes out so you have the indication that, okay, there's a
problem, we need to have it serviced. It's really just a matter of what the
customer wants — the preference. That's what we've seen in the industry too; we
kind of get both schools of thought from the customers we talk to.

Adam: It would make sense if you guys
are handling the over-voltage events to possibly look into the under-voltage
events or some of the other sag situations. We had an issue recently with a job
where there was a fixture being mounted to a crane, and every time the crane
would move, the voltage would dip and the fixture would go out. I would imagine
those are less common, but do you see getting into power conditioning, where
you're taking care of both of those issues?

Marc: Our forte has been in protection
for so long, I have not gotten an indication that we're going to look at more
power conditioning or power quality type of products. That doesn't mean that we
won't. We're doing a little bit of that more on the very low-power handheld
devices. We have some filter components and things like that, but nothing yet
to the degree that would be needed for a lighting system like this.

Closing Thoughts: The Future of Littelfuse

Adam: Anything else you'd want to
touch on?

Marc: I think we covered it pretty
well. Just a couple more points on Littelfuse. We talked a lot about circuit
protection, and we have the broadest portfolio in the industry. The nice thing
about that is we get to really provide the optimal solution for our customers
because we have multiple technologies that we can offer, so we can really
provide what's needed for the application. In addition to circuit protection,
we're really growing in other synergistic areas as well. I mentioned power semi
before. We did recently complete an acquisition of IXYS Semiconductor, which
provides high-power semiconductor power devices — MOSFETs, IGBTs, modules, as
well as some gate drivers and things like that. We also have a line of magnetic
and temperature sensing devices, and we're going to continue to try to expand
and grow that product portfolio as we move forward. So I think you're going to
see a lot of changes over the next few years — a lot of increase in product
offering that Littelfuse is going to offer beyond the circuit protection side.

Adam: Cool — all good stuff to help
the customer protect their investment.

Marc: Exactly.

Adam: Alright, well Marc, thank you
very much. I appreciate the chat.

Marc: Thank you Adam, I appreciate
you.