How Surge Protective Devices Function
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- เผยแพร่เมื่อ 11 เม.ย. 2024
- Did you know that inside of a surge protective device (SPD) specially designed components reduce voltage spikes to protect your electrical equipment from being damaged? To learn more, watch this video where Mike and the team explain just how SPDs do what they do!
This video is extracted from Mike Holt's Understanding Electrical Theory Library. For more information about this product, visit www.MikeHolt.com/Theory or call 888.632.2633.
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Hey Mike, I thought you might like to know, back in the mid to late 1970s I was working for Honeywell and I initially had a problem when I was working at the Federal Reserve Bank in Philadelphia, when the motor operated doors came to the end of their cycle, opening or closing, they caused an inductive kickback spike which would kill our solid-state circuitry. MOV’s, (relatively new at that time,) seemed like they may be an answer to our problem. So, I tried them and they worked amazingly well! Sometime later we also had some problems with another site that kept getting hit with lightning; MOV’s also proved to be the answer there. I'm glad that the National Electrical Code is starting to finally Implement MOV’s and I look forward to their continued protection on these systems. However, on signal lines, super-fast Bidirectional Zener diodes most likely work better than the MOV’s.
Thanks and keep up the good work.
Rick.
I have a UPS with built in surge protection. I have a surge protector on my computer equipment and peripherals. I have a surge protector for my television and digital recorder and radio and etcetera which also has surge protection for the coaxial cable. I use WIFI to connect my computer to the cable modem.
Lightening once struck inside the apartment complex and took out all the electronics in three buildings except for mine. I immediately went out and bought new surge protectors and replace the old ones.
I would just like to add that Metal Oxide (essentially a metal typed rust) is semi-conductive and not a semiconductor in the sense like the ones that are used by chip manufacturers. It's a metal powder between two plates that has poor conductivity until there's enough voltage to break down the resistance (heating the oxide and converting it back to metal); causing the two plates to "clamp" down and shunt voltage either to ground or a short circuit. Either way, once this occurs, the MOV must be replaced or removed before the circuit can operate again.
Wow, great information.
👍🏻👍🏻👍🏻
I was laughing, just like Eric and Mario, when the panel was in agreement about surge protectors cannot guarantee protection from surges. FYI, I have noticed older power strips with surge protection have been tripping arc-fault breakers when vacuum cleaners are turned on from other circuits.
Hum... I need to remember this. Thanks
I always get pumped when I hear the electric guitar on a new Mike Holt video
Interesting theory and explanation behind this. So there’s no guarantees that a surge protector will work after a strike?
Lol... exactly... it's called 'life.'
Excellent explanation, thanks🙏 for sharing
Open neutral can create sustained 240V on a receptacle. I've seen this damage all sorts of appliances. MOVs in surge protectors at the outlets will burn up, sacrificing themselves to protect the appliance.. A whole house surge protector may not do anything to alleviate damage from an open neutral on the power company side so, like you said, best to have surge protectors on all appliances. I recommend putting fire proof material, such as a piece of tile, between the surge protector and the carpet because I've seen some surge protectors with their plastic cases melted after an open neutral event.
You are 100% right about power strips with internal TVSSs protection. The revisions to the "standards' for what you remember as TVSSs to what we now call SPDs have internal overload protection so that they shouldn't catch on fire like you described.
Excellent information
I’ve had a few instances where a dropped neutral on the service causes the SPD to overheat and essentially blow up. SPDs are meant for very short transient spikes, I’m pretty sure the dropped neutral increases the time that SPD deals with the spike, and some of them just can’t handle it.
You are correct for the SPDs (TVSSs at that time) did not have continuous current flow protection. This was corrected with the second edition of UL 1449, Standard for Surge Protection Devices in 1998.
I understand that this is designed for general electrician consumption, but Mike's hand-waving explanation illustrates the difference between tradesmen and scientists. Mike may make fun of research engineers that they may call something a "light fixture" instead of a "luminaire", but similarly, I can't help but smile at this explanation.
What was the problem with his explanation? Made sense to me.
@@R900DZ It was a high-school level introduction skipped the role of inductors and capacitors and how resistance to voltage change forces the lines to heat. and how some also shorten to ground. honestly for sparks he should have just shortened it and said. A spd has a specialized circuit that opens to ground or absorbed the voltage as heat. the important bits for electricians is:
1 Ideally you need a layered defense. Service, panel, and device. The further upstream the more time it has to react.
2 the types of devices at each location. and what size you want in each region of the country
3 communication spa's LOL. VCR?! what's that? I have an internal 5G box that just plugs in. There are zero wires coming into my personal house. I only installed the intersystem bonding bridge because it's required.
Antenna I have has a coax and plasma shunt to a second ground run to the main.
@@R900DZ if the surge protector creates a “short” and the two lines are “shorted” through it, how come there is still 330V left to go to the device in parallel? If it really was a short, there should be zero, no? Mike was close to explaining it but didn’t quite manage. Again: close enough for a hand-waving explanation and to be honest: electricians don’t need to understand how semiconductors work to be successful. My point is that this quiet hostility between tradesmen and engineers is unnecessary and I’m pointing it out because it usually goes the other way: tradesmen will look down on engineers and scientists because they use different lingo, and may sound amateurish when they speak in the DIY context…
@@yarekkmy assumption for the 330v goes back to the prefix SEMI in semiconductor. That is to say it is not a true short, it’s a SEMI short, it dissipates some not all of the voltage.
@@R900DZ my point proven.
CNC machines and data centers, all need surge protection.
Great! thanks
Sometimes these MOVs are built-in certain sensitive devices. They're in commercial Overhead Door operator boards to protect the motor and drive system.
I did not know that. Thanks for the teaching.
As a service Electrician very often I find the breaker feeding/protecting the surge protector is tripped. Even though the indicator LED is off the customer is unaware. The service call is never related to a “surge”.
Good point!
Is there any research on ferrite core chokes vs. MOVs ? Yes frequency is a big factor.
Is there anything in NFPA 70B about checking MOV indicator lights ? Power panels are often in a boiler or mechanical room where they are no checked. As for the home? I doubt people will look at them.
I'm sorry but I don't know...
I wish i could take your courses
You can, call 352.360.2620!
@@MikeHoltNECit just cost too much for me to afford at the moment. Im still grinding tho trying to study when I can to perfect my career!
Just took my test again got a 66% I am only on page 131 of the electrical exam preparation. I feel like in connecticut they make the test difficult and tricky because the questions are misleading and lacking absolutism. They could make the test difficult as well as being cut and dry just saying. Will keep at it!
There can be sinister behavior up here. Installations designed to trick other electricians maybe this is the reason idk, I’d never do some of the things I see but I sure have come across vindictive things. Some to code some not
Hum... you got to page 131 in my exam prep book which has a total of 496 pages and you failed the exam. Then you think that the exam is flawed... actually if you complete my program, by answer all of the 3,000 plus questions and you watch all of the videos, you'll 'kill the exam' the next time.
Sinister behavior and vindicative things? Really...
Creates a false short circuit during surge conditions, shunts extra current away from load, can even cause OCPD to open to put an end to the problem.
And saves the other devices as a result
Transients are crud that doesn't belong. Nobody will guarantee that it is AC, nor will anyone guarantee it's anything like a sine wave. So the expression "RMS" ought not be applied to transients.
RMS means root mean squared. It certainly doesn't need to be a perfect sin wave, you can perform an RMS calculation on any wave form, including a transit
Thank you, RMS is just a calculation of the square of the instant values, then we get the mean, and then the square rood. It really should be SMR...
RMS is a calculus operation, that squares each instantaneous value, integrates, divides by the time interval, and then square roots the result. You can have an RMS voltage of any voltage signal, doesn't have to be an AC sine wave.
For instance, if the surge were shaped like a parabola, V(t) = 1000*t*(2 - t), from 0 to 2, the RMS voltage would be found as follows:
Step 1, pull the 1000 out in front, and put it back on at the end.
Step 2, square the function. t^2*(2 - t)^2
Step 3, Expand: t^2*(2 - t)^2 = t^4 - 4*t^3 + 4*t^2
Step 4: Integrate: (1/5*t^5 - t^4 + 4/3*t^3, evaluate from 0 to 2: 16/15
Step 6: Divide by the time interval to find the average: 8/15
Step 5: square root: 2*sqrt(2/3)
Step 6: recall the 1000 factor, to get 2000*sqrt(2/3) = 516 Volts
@@carultch Excellent!