Connector Mismatch Issues in Photovoltaic (PV) Modules

Have you experienced issues with the connectors on PV modules at your solar energy sites? In this discussion, Director of Operations Edward Trujillo and Project Engineering Manager Frances Plourde discuss the issues which can arise from using mismatched PV module connectors, how to identify connector mismatch, and how to prevent this concern from negatively impact your PV systems.

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Transcript

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Welcome to Power Bank, sponsored by NACE Renewables, where big ideas, bold conversations, and unstoppable energy collide. We're your hosts, Ann mc Broome and Francis ppl, and we're diving headfirst into everything you need to know, want to hear, and can't stop talking about in renewable energy. Let's get into it. Hello, and thank you for joining us on the Power Bank Podcast sponsored by NACE Renewables. My name is Frances ppl and I'm a project engineering manager here with NACE Renewables. Today I'm speaking with Edward Trujillo. He's our Director of Operations. We're very excited to speak with you today about photovoltaic connector mismatch and the issues that can cause in photovoltaic energy systems. Edward has extensive experience in addressing these issues and working to devise solutions to the problems that these can cause. Thank you so much for being here, Edward. Hello Francis. Thanks for having me on. It's a pleasure. Absolutely. Do you wanna provide a bit of context as to the issues surrounding PV module connectors and why these can cause such severe issues on site? I. Yeah, definitely. So first I guess we should talk about the actual solar modules themselves. Now, when we talk about the mc four connectors on these modules, I noticed a lot of times they're not standardized. So when you do get a solar module, they will have different types of connectors. Which is pretty interesting when you look at it like overall, the entire industry. How many different types of mc four connectors do we have? There are hundreds. So that's what I really wanted to focus on at least for the first part. Absolutely. Before we dive any deeper, can you clarify for our audience what an mc four connector is and what purpose they serve on a solar module? Yeah, definitely. Solar modules, they come with, two connectors, two tails. One is a positive connector, one is a negative connector, and the mc four is an interlocking device from solar module to solar module. That design is a wire with a pin and a boot over it, and the boots lock together and interlock the pins. So you have a good connection from wire to wire, from solar module to solar module. I see. So an MC four connector is essentially a type of connector similar to what we would call like a USB connector, where that's just the standard connector for a PV module. Yeah, correct. So why is it that different module manufacturers and different companies use different types of mc four connectors, and why don't they all fit interchangeably? I would imagine due to price is probably the overall reason. Pricing of these mc four connectors can vary depending on what the manufacturer wants to spend to create or design solar module, that base price goes into the overall cost of creating a solar module. That's really interesting. Are there specific manufacturers of these connectors that one should pay attention to when determining which connectors to use for which particular types of module? Definitely. And this goes to your overall design. When you're designing these things, what's the stability of the mc four? You know, has it had prior issues? Do you really wanna, they really do get into research. This may not have been happening. 8, 10 years ago, but it is today. There's a lot of engineering involved in actually picking one certain type of mc four connector. Certainly. So what are some of the available manufacturers that create these, and how can you tell when you're looking at a module or a module data sheet, which specific type of mc four connector is used? It's usually in the solar module data spec. And it'll give you a list of what type of mc four connectors, what type of wire they use. There's a lot of specific data that's used in those specs. So it's always good to have a copy of that spic, definitely. Can you share some of the names of the module connector manufacturers that our clients may be aware of? Oh, definitely. So we have stably there's Amphenol, biz link connectors. The names just vary also, if you look on just different type of platforms, there's cheaper ones that come from overseas China and these different countries that manufacture them. And that's kinda where the issue comes in. Yeah, it seems like this inconsistency is quite rampant within the industry. On our podcast. Before we've talked about how there's very little standardization in PV module characteristics at the module level, but it sounds like that that lack of standardization can continues into the connector level as well. Yeah. And I've seen this on many occasions. The devil is in the detail, right? If you get an mc four connection spec and you look at the actual sizes, that's where you really gonna look into the level of detail that you need to be looking into when you're actually designing the modules or having to install an overall site what are we actually going to use on the site, according to the specs of the solar module. Yeah, definitely. So can you explain what are some of the issues that can arise from having mismatched connectors? Why is this something that we care about and why do we think our clients should be aware of this? Yeah. Maybe I could tell you a couple stories of my findings on sites. Absolutely. If that's okay. Out here in Arizona, we do have large solar utility scale solar sites. And these were built back in 20 12, 20 13 and. What I imagine is there wasn't a lot of research going into, specifics. So we had a solar module that was used on a site. And looking at the data spec, which was some of the research that we do when we're looking into some of these sites and some of the site issues. There was two different types of mc fours that were specified in the data spec. When I pulled up the actual build of each of these mc fours there was very. Minute details, very small. Slight variations in each one. Now I could just imagine the EPC. When they went to install this solar module on the site, those two names were listed for those connectors. And what I think was that they thought they could interchange'em or they were, interchangeable or they were compatible to use together, and that was just not the case though. The spec did not specify that. So that's where the issue came in with the site. With the mismatched connector. When I was on site, I identified. What type of mc four was used on the solar module and what type of mc four was used on the home run conductor. And they were two different types. And this came after a lot of actual troubleshooting, being in the field, finding issues. When I started with this company I was a utility scale o and m technician. My first couple of weeks was to diagnose what's the problems that we're having on site. They would create work orders, we would go repair blown fuses and just different findings. What I found was a lot of blown fuses. And these are midget fuses that are in combine boxes which are usually 15 amp fuses 600 to a thousand volt dc. So I would start replacing these fuses as I found them. We have an outage. There's not a lot of production coming from this combiner. Please go check it. I would test with my multimeter, test the string, make sure we had voltage, check for ground faults. And then I would replace the on several occasions I did find a burden, MC four connection from the solar module to the home run conductor. Now looking at that, overall you would say, well, you found the issue immediately. Well, the issue was that those two connections were just burned massively. So you couldn't really tell what the actual issue was. So we'd replace those two connectors with the proper matching mc four connectors, install the fuse, test it, and then get it back online. Over doing this over time, over months, the issue that I found was there was still a lot of midget fuses being blown in the combiners. I would go replace test just as I had done before. You know, check for ground fault, test the voltage, document that replace the fuse. And this happened multiple times on the same strings. So that's where I did start to see a re a recurring issue of sorts. After time what I did find was that there was a lot more mc fours connections from the solar module to the home runs that were melted. We, I would fix those. Install the fuse. And I would move on over time as you could imagine being on these sites. I would drive around and as soon as I got onto the site, the site would be producing, I would start smelling fires. And that's where the concern came in. Okay. What's on fire? Why is it on fire? And that's kinda really where I started to dive into what was the issue here. Have you seen fires on sites and what kind of damage you can do? Unfortunately, I have, yeah. They are incredibly devastating both to the system, the equipment on site and the systems on site. But they can obviously then. Cause severe safety concerns, not just for the workers on site who we obviously want to be safe at all times, but if anything can spread, it can be devastating to the surrounding area as well. So any component of a system that can lead to this kind of fire should absolutely be addressed as soon as possible. Yeah, definitely. I felt the same. And due to the vegetation. So the vegetation was only annual. It was never semi-annual. But once a year they would come and cut all the weeds down after a year of dry brush being there, this was just a huge fat fire hazard. What it turned into after starting to do the repairs on this site. This site was 26 megawatts. It was a huge site. You could imagine how much dry brush is under these solar modules. You get a burned mc four connector from the module to the home run, starts to leak down, melting plastic that's on fire and it starts a fire. It started to be every week or every other week where we had fires on the site. It turned into months. two months I would, Ima I would get there at 6:00 AM by 7:00 AM when we had full production. We would start to either smell fires and go check the areas, or we would see evidence of a fire from the night before. My shift was usually six to three 30. Typically, and so we would have to document, really overall, what I started to do was I started to really just investigate things that weren't on fire with a blown fuse. I said, let's start here and see what we can see, and I started to find that I. Two different manufacturers were installed from the solar module to the home run. And, so that's where if you have that mismatch, just the slight variation, which the slight variation was the internal pins inside the boots. They weren't fully connecting, so you would get. Arcing overheating. And then after time these things would start on fire and then cause a fire on the site. So when I did find this, I started to document this. Where is it at and how far is this? Turns out about 80% of the site had this mismatch, which was just massive. It was a massive. Amount of issues that were being created on site. Of course I documented it. I ran it up the chain. And overall, what they had to do was an investigation after my findings. An engineering team had to go out there. You need to get engineering on site so they can look at what's installed, all the devices on site, what kind of issues are causing, and really give them an overall give the customer an overall layout of what the problem is. In turn, after about two months of putting out these fires, the third month, we got authorization to start replacing these mismatch connectors. Now the problem was, I. The engineering team that went out there could, because I documented, because the major issue was on the positive home run, that this was where the issue was. Now if you've been to a solar site, a large scale utility solar site, you can see that all these connectors, all the home run wiring, they all run and they're protected, because. You know, the sun will just eat away at this wiring. So they put it's called Split loom, which is like a plastic covering. They zip tied those together. So unless you took it apart, could you actually see all the connectors? Now they didn't do this. We did start to replace the positive mc four mismatch connectors after these were replaced, after, I believe it was probably about$130,000 that they approved us to go in and do this. I'm talking about a crew of 20 people, and this was every day for, I would imagine about a month and a half. After those repairs were done, we still had fires. And those connections or that group of wires that was covered in the split loom was actually starting on fire. And this is due to the negative side that was not looked at, was also mismatched. So it was like a double whammy, right? Where you had double the issue. But because extensive research wasn't done and they didn't look at the complete layout, so we had double the issue. And I believe it took about seven to eight months to fix the overall problem and hundreds of thousands of dollars. And that's not even, that's not even accounting for the fire damage when the brush would catch on fire. You can imagine. I know you've seen this where the solar modules catch on fire and it just takes off, the fire, there's no stopping. I mean, it's DC power. So it was just, it was so massive. I mean, the amount of damage was just extensive. And then after those repairs, I mean seven, eight months, we started to have inverter issues after everything was repaired because of the mismatch, because of the fires. Yeah. So I believe these were central inverters. We had to replace several of them. To replace the essential inverter internal parts or the entire inverter. It's a massive undertaking as well. This site really didn't produce fully for about a year and seven months to where they got it to full capacity finally, after all the problems were fixed. Yeah, so it was pretty widespread. All of that site damage and all of that lost production just because of two different types of mc four connectors. Yeah, that's pretty staggering. Yeah. Something so small and so small of a detail caused so much damage and, if some research would've been done heavy research. Before the EPC installed or before assigning installation teams, it could have been totally avoided. But then now on the backend, what did it cost versus taking the extra time to really do some research. And that's really, I know you have experience in seeing these issues as well. I. I haven't seen connector issues probably as up close as you have, but I've seen several cases where site owners have become aware later on, after the entire site has been installed that the connectors they've used have not been consistent. And proactively before anything happens, they decide to. Deploy a team of technicians to go out there and they literally have to disconnect every single module. They have to pull out the connectors from every single module and completely reconnect them using the correct connectors. So even aside from any damage or any loss of production caused by connector mismatch just in order to address this concern before it becomes an issue. It still takes a huge amount of time and money to do. It's so much easier to pay attention to this before something goes to installation instead of trying to clean up after, especially in the case of thermal events or other safety issues. Yeah. You know what I thought was really funny is I put these two mc four, the specific mc four connector type two different types. And I asked Google, can this connector be used with this connector? And of course it said no. But something as simple as that would've changed the whole outcome of the site, which is just interesting. I don't know if it was. Available back then. Just something as simple as that would've saved, hundreds of thousands of dollars of damage. So I thought that was a little funny when you look at it, just, simply, talk to text into Google. Hey, can we do this? No, you can't. Yeah, absolutely. And. I think something that kind of undergirds this whole conversation that I don't know if we've explicitly talked about yet is that it's very sad that even though these connectors are. We believe incompatible and can lead to significant issues. They unfortunately do connect with each other. They physically interconnect even if they don't make full, proper electrical connection, which is really unfortunate, and in some cases it, it might feel like you're almost needing to force it in order to fit. It is the electrical version of the old adage. Just because it zips doesn't mean it fits, just because it physically fits together. Just because you can snap the two and zipp the connector together doesn't mean that they are actually compatible, and it doesn't mean you won't have issues down the road. A good rule of thumb with all electrical equipment is if anything is not fitting together naturally or is not coming apart naturally, be very careful with it and make sure you're taking proper precautions when connecting and disconnecting electrical equipment because anything that's supposed to be made to work well together will. And if it's putting up a resistance or putting up a fight to it, it probably means that something is wrong. So make sure to pay attention to that. Yeah, the funny thing is with the manufacturers, the different manufacturers is the exterior, which is the boot, right? The plastic boot that goes over the pin. They always make sure that those connections are exact match, which is interesting. On this instance, it was the interior pin that was not correctly matched, but the exterior boots of the two connectors, they actually interlocked easily. So you would imagine, oh yeah. It connects properly just like you're saying. It connects properly, but it actually, the interior pins were the issue so that, that's a very interesting point you bring up there. It's exactly what you're saying, the boots fit, but the interior actually was the problem. So that's funny that you say that. That's exactly what happened. Yeah, absolutely. Do you have any additional things you've noticed regarding this issue or things that you think our clients should be interested in knowing? Oh, definitely. So there was another instance and, with these new sites, what we're seeing is this higher voltage, higher amperage, double strings. And that uses an eight A-W-G-U-S-C two wire. Now. When you are looking at these things, you definitely want to get the correct mc fours, but also the correct size wire mc fours. Because, on the older sites it was just you were having mc fours that were made for 10 a WG USC two, which is the wire size. It's a less voltage, less amperage. And when they started to move up to 1500 volt sites or 1500 volt strings on these sites, which are sometimes combined strings, then you started to have an issue with Mc four Mismatch here, where technicians in the field, or should I start at the top where they ordered mc fours that were designed for 10 a WG. You have these sites that now have eight a WG wire. Technicians are like, well, we gotta make it work. So they were removing this interior, it's like a little plastic seal. So when you connect the mc four and the boot, it has a plastic seal on there. You lock it tight. They were removing that so the wire would fit with the pin. And then we got water intrusion. This was a huge issue as well. Water going into the mc four moisture intrusion, it's gonna instantly cause rust. So now we had another instance of overheating because either water was in there and rust was starting to get into the pins and you had the loose connection to arcing. So this is another instance of. I would say it's also an MC four mismatch where you don't see that, you don't understand it unless you're really installing these things and reporting this to the engineering team. Like, Hey, you got the wrong mc four connections for the wrong wire size. That's starting to be a constant thing that we see as well it's really interesting the different types of mc four connection problems that are out there in the industry, and unless you really get in there with engineering team or do a case study, can you really find these problems? And that's really where we have to work together. Let's collaborate to make sure that we have all the data we need to find these problems for our customers to essentially save money, but also save this, save the, all the assets on site from a year away you don't address this problem and then it's gonna cost you hundreds of thousands of dollars to fix it. So that's really an issue that we see as well. Absolutely. When in the process of a site being, designed, constructed, commissioned, do you think is most essential to identify and go back through to ensure that you have consistent Mc four connectors used. Do you think it's most important to do that, during the design process or as it's being constructed? And how do you recommend clients going? Go about that in order to make sure that this issue gets addressed before it becomes problematic. Maybe a temporary setup of all the parts that were ordered, setting up an entire array from the solar module all the way through to the inverter, setting up like a template. And you test this thing and that really does go to like an r and d, research and development. Let's design one of these with all the parts that we ordered. Let's make sure that these are gonna interact with each other correctly. And then get a, get at least a couple weeks test to see, are we seeing overheating? And that comes into thermography, taking readings, taking thermography samples, really looking at the data that you're finding, that would be huge, before you go and, create this 14 megawatt or 26 megawatts site to make sure that all these components are compatible. Using standardized pro mc fours going from top to bottom. Here's our solar module, here's the mc four connector. We want to use this specifically over the entire site. And then just running that down the chain. Hey, we can't use anything else but this. This is our wire size. Here's the proper mc four. Here's what we're gonna do. And this actually happens, this also has happened with branch connectors. So do you want me to explain what branch connectors are? Please. Yes. Branch connectors, like I was talking about 1500 volt strings or home runs. So the branch connector will combine two sets of modules. So you have, for one array, you'll have 18 to. 26 modules, solar modules, those are all interconnected with each other. You'll have a branch connector, which connects these two strings together to combine them to run one home, run back to your combiner. What we've seen is these branch connectors, they'll have different mc fours from the solar module to the branch connector as well, which causes the same issue. Arcing fires, down strings blown, fuses in the combiner box. Then you have to go in and you have to replace all these, but you have to make sure that the manufacturer's going to use specifically your mc four on your solar module. Just another instance of seeing this type of issue on the sites, and this has been widespread. Even with these branch connectors, typically what you have at the end of the branch connector is a inline fuse, 30 amp. And you have to ensure that that is the same. Connector as what's on your branch connector and the same connector that's on your solar module. So that takes a little bit more research to make sure that, you're installing the proper devices that are all compatible. So a lot of research, you really have to dive in deep when you're designing these systems and making sure that everything's compatible. So it's a lot of information to take in. It really is. Yeah, it sounds like there's a lot of due diligence that needs to be performed at throughout all the stages of a PV system being constructed. So when we at NACE renewables come into a site, we're usually coming into a site that's post COD, that has already been constructed and is potentially dealing with issues that we're being asked to solve. In the case that you were discussing before where you had a site that was having repeated thermal issues, inverter issues, what really helps you narrow down the conclusion that this is a connector issue, and then where do you go in the documentation of the site to really determine that the connectors are in fact mismatched. So there is. Just a slew of tests that you really have to run to find these problems. And that's really, that's where you have to dive in with both feet. From testing the string to testing for ground faults, to mega testing, to thermography reports to IV curve testing. And, what I found was hands-on IV curve testing just outweighs thermography. It really does. And that's really where you're gonna have your findings. A lot of these IV curve testing units, they have, mega testers within the report. So when you run an IV curve test on your string, you're gonna see what is the ohms that's coming back from your string, and that's gonna be balanced out. If you have a balanced string, it's gonna show it. If you don't, if you have an imbalance, especially in the Ohms, you're gonna see that instantly. So that's where you really wanna get hands on with something of this type. You really wanna, get it there and be really, be wise, but also. Smart spending. And that's really where, a lot of our team comes in where you don't wanna spend hundreds of thousands of dollars for testing. You want to take a portion and you want to test that and really dive in deep and see, with the service reporting, where's our major issues? Where is this located? And get a map and an idea of onsite, where are we having the most problems? On this site. Okay, let's dive in deep on this section and let's see really what's happening here. And that can be done, and that's where the collaboration has to come in because you have to you have to get with an engineering team to make sure that all the data that's coming in is correct, but also that we can read it. And then also field services, they have to get out there, they have to get boots on the ground to do an investigation and see just like I'm talking about Ivy Curve testing, thermography doesn't hurt to have as well. That does show you where some of the issues are. I know a lot of these, different companies are getting more complex with the thermography reports, but hands-on IV curve testing. We'll definitely beat any type of thermography that you may have on site. It's specific for the data that you need. Should I say? So thermography with Ivy Curve testing is definitely a good start to the investigation, but also there's other techniques that you can use as far as troubleshooting areas and finding out issues. So it has to be a collaboration. It really does. Yeah, absolutely. It sounds like it. Can you provide a bit of context as to why specifically IV curve tracing and thermography help with finding connector issues. How does, how do those testing methods help identify the fact that it's a connector issue as opposed to some other form of module issue leading to a hotspot or failed IV curve test? Yes, definitely. So the thermography will show you what strings are down. And this goes if you get a thermography report over the entire site, you'll see what areas are down. Sometimes it's widespread, and you can't really focus on one area. It's like, okay, this problem is happening for every other table or. Solar array. And then if you get boots on the ground and you get IV curve testing, you can match up, is it a solar module issue? Is it a string issue? You can weigh out the evidence on those two scales. And then also. A visual inspection. If you're there and you're doing an IV curve test, plus the visual inspections, are you inspecting every connector? Are you looking for those details? And that's really where you're gonna see some of the issues. These issues vary. It's not just mc four connectors, but a lot of times. It is. So really boots on the ground and those three steps are really important to an investigation of this type. Wonderful. Thank you so much Edward. This has been incredibly enlightening and I think we'll provide our clients with a lot of great information to truly understand the importance of ensuring connector continuity at a PV site. Do you have any final comments or suggestions for clients potentially facing these issues? Actually we specialize in this. We're special projects, a director of operations for NACE special projects. And this is something that we specialize in to really increase the money you're gonna spend on investigation. That's something we are really we're really invested in, is to make sure that our customers dollars are spent wisely. And that's, we really want to make sure that each customer is taken care of properly and the issues vary. So with a smart inspection, we really want to detail what your issues are on site. Thank you so much for having me on. I think this has been a great chat, especially on these issues and just a growing problem. So I'm really happy to be a part of it. Thank you. Wonderful. Thank you so much Edward. Thank you. Thank you so much for joining us on today's episode of The Power Bank, sponsored by NACE Renewables. If you have any questions regarding the topic of our discussion today, or you would like to reach out to us about special projects for photovoltaic sites, we would absolutely love to talk with you. You can send us an email at Power bank@nace.com. Thank you and keep powering on.