When you buy tickets to a festival, you’re anticipating good eats, drinks, live music and entertainment, vendors, and perhaps, even some dancing. Certainly, an electrical malfunction is not on your radar. Unless you’re an electrician. Perhaps, you do think about these things? Who knows?
Anyways, things took an unexpected turn for partygoers at Huntington Beach’s Oktoberfest celebration last Saturday night when a transformer exploded at Old World Village restaurant. Que, large fires, immediate evacuation, and mass-chaos. It was not good. Unfortunately, two firefighters and three festival attendees were injured in the explosion. Local news reports have indicated that while most of the injuries were minor, the owner of Old World Village, Bernie Bischof, suffered major injuries from the explosion. Fortunately, with continued treatment, he is expected to recover in the next few weeks.
So, what exactly happened?
Well, according to the Los Angeles Times, at about 8’oclock on Saturday night, a server at the restaurant noticed a strange smell coming from the underground vault below the patio that housed three transformers. Bischof acted fast– immediately contacting the fire department and blocking off the patio area to guests.
Oddly enough, weeks earlier Bischof and his sister had contacted their power company (Southern California Edison) to investigate strange noises and a funky smell coming from the transformer vault, but they were given the all clear. Hmm, that’s a little fishy, right? It gets worse. Almost a decade ago (in 2010), one of their transformers below the restaurant exploded early in the morning. What is going on? Is this a common issue? We will get into that.
So, back to our story. There were actually two blasts, the first of which blew off the vault’s 50-pound door. The second explosion came moments after. We can’t even imagine how terrifying this must have been for everyone in the vicinity.
The aftermath had a wide reach, as well. Almost 1,700 Edison customers lost power, as a result of the initial explosions. Worse, over 300 residents were left in the dark all night, not re-gaining power until 9 am the next day. Things are not all bad though. Overnight, Edison replaced all three transformers in the vault and opened an internal investigation into the cause of the explosions. Great work – we love to see it.
Why would a transformer explode though?
Aha, we found ourselves asking the very same question after learning about the Oktoberfest incident. At this moment in time, we cannot say for certain what caused the aforementioned explosions, so we are just talking about transformers in general. Got it?
Let’s first look at the basic breakdown of a transformer. If you read last week’s blog, then you have a head start, but we will review it again just in case you are behind on your reading. Transformers use electromagnetic induction (think: a changing magnetic field) and two (or more) coils of wire to transfer electricity. Sounds pretty simple, yes? It’s also important to note that transformers can either increase or decrease the AC voltage, and like all of us, they can come in many shapes, sizes, or varieties. Neat.
So back to the main question – why are these things exploding on us? Well, we know for certain that if a transformer is suddenly hit with an unexpectedly high level of electricity, it can explode. However, transformers are programmed to shut down automatically with a spike in energy. Unfortunately, it could take up to 60 milliseconds to power off, which seems very quick to us, but is turtle-speed for the transformer. At this speed, it may be too slow to prevent an imminent overload catastrophe.
Wait, there’s more. Our good friend, insulation, can also trigger an explosion. If the transformer’s insulating materials lose their ability to insulate, it’s not good news. Insulation can be made from oil or cellulose (paper/pressboard). Cellulosic insulation will help store electric charge when a transformer is energized, isolating components of the transformer with varying voltages. Cellulose can also be used to create ducts for the oil, protecting the transformer from excessive heat and thermal damage.
We mentioned oil, so we should probably talk about that. Inside of a transformer are a couple of gallons of mineral oil to keep the circuits nice and cool. You can imagine though, if too much electricity enters the circuit, things begin to heat up pretty quickly. Then, of course, you factor in the fact that oil is flammable! That is just a recipe for success, right here. The coils of wire can literally “fry” off, releasing sparks, and setting the oil on fire. Not good, guys. In the case of the Oktoberfest explosion, all of the injuries reported were attributed to burns from the hot mineral oil.
How can we prevent this?
Well, there are a lot of considerations to make when it comes to your transformer’s health, since there are electrical, mechanical, magnetic, and thermal mechanisms working together. These include windings, insulation, and the transformer’s core. There are other accessories, as well, but we are trying to keep things simple right now. With each component comes a recommended suite of electrical tests.
It’s like bringing your transformer to the doctor for an annual check-up and getting a full bloodwork panel, a physical exam, a vision test, a skin check, a mental health screening, and a dental cleaning. By itself, one of these tests may give you a quick snapshot of your health, but together, you have a comprehensive panoramic view of your health and wellness.
Now, don’t panic, but there are a lot of tests you can (and might need to) perform on your transformer. However, the nature of the test is important. Is this a commissioning and installation of a transformer? Is it a routine screening? Or are you performing a diagnostic analysis? The answers to these questions matter.
When it comes to preventing transformer failure and explosions, routine screenings are necessary. However, unlimited testing is not a practical use of budget or time, so choosing the right tests in the right situations is vital. If specific “symptoms” are present, specific tests can be “prescribed”. However, if there is no reason to be concerned, it is not practical to run an electrical test anyways. In case you’re curious, these tests may include (but are not limited to): winding resistance, dielectric breakdown of oil, transformer turns ratio, power dissipation factor, exciting current, or bushing CT ratio.
Next week, we are going to get into the specifics, depending on your testing situation. We’ll also explain, in great detail, the list of tests we just threw at you. We know you’re dying to learn more but sit tight. We’ll be right back.
-Meredith Kenton, Digital Marketing Assistant, Megger – Valley Forge