SafetyCut 3phase Protection?

[carlyai]

Again, without any data, my 3 phase SafetyCut may have saved some electrical/electronic equipment house equipment.

Early this morning we had some close lightning strikes. One tripped the SafetyCut and and I didn't reset it till the storm lightning had passed. I checked and one breaker in the outside CU had tripped and all the MOVs were shot.  

I still have the feeling that the SafetyCut tripping and removing power from the house, could have helped protect equipment from subsequent close strikes.

[bankruatsteve]

The EMP produced by a close-by lighting strike can and will affect electrics whether plugged in or not.  Whether connected to the mains or not.  The mains disconnect would help prevent surges from the mains getting any further and the trip is more likely to be the over-current breaker versus the RCD.  

[carlyai]

I would think the EMP would have to be much much bigger than caused by a lightning strike. We never had such a problem at our TV station on a mountain range, but struck many times by lightning. Now static electricity discharge into electronic components is another thing. 

[bankruatsteve]

A billion volts and a billion joules of electric energy can produce a big EMP.  ????

[maxpower]

The safety cut likely disconnected through imbalance detection or from a spike in the detection electronics. They don't always trip when presented with line spikes and when they do most damage is already done if nothing else is around to prevent surges reaching sensitive equipment.

 

Metal oxide varistor's (MOV) will begin clamping well before a safety cut has considered disconnection. It is the difference between milliseconds of breaker operation and microseconds or even nanoseconds of a MOV response time.

How much devastation is left behind is down to how much of the spike energy your protection device can dump before throwing in the towel.

Just before leaving data center support back in late 2019 a building services transformer secondary was hit by lightning causing earth leakage breaker trips deep into the service.

 

Most of the energy was lost through spark gaps with the remaining clamped by surge devices. The fire alarm power supply MOV's failed to catch the remaining spike and died.

 

Further investigation revealed poor grounding arrangement at the fire alarm panels.

[Crossy]

Hope you have spare MOVs or new ones on order at least.

 

The MOVs doing their thing and the Safe-T-Cut opening (possibly as a result) certainly saved you some grief but the exact mechanism is really unknown.

 

[carlyai]

My wife just told me that many houses around suffered electrical damage. Mainly fluro light damage.

My MOVs are expensive. Might have to find some cheaper ones with good specs. if I can. If I can remember they were about  B800 each. I think they were 4square brand but have to check.

[Crossy]

You've got to compare what the MOVs cost vs what replacing all the fried electronics would cost. I wouldn't skimp on the replacements.

 

We have big beasties on the front end and loads of the little blue chaps scattered around mostly in all the LED light fittings.

 

I also installed both AC and DC MOVs on the solar inverter. The DC units came from Lazada, definitely not cheap! The AC ones came from a shop in Shanghai recommended by a Chinese friend whilst I was there on business, I bought a box of replacement modules too.

 

 

[Brock]

Most lightning damaged is caused by the electrical surge traveling in through the ground system. Electricity flows faster through the copper wires than it does through the ground (soil). There is no way to protect against that.

I had an aircraft simulator and its large UPS system badly damaged by a lightning strike, power was off at the time (over the weekend). Lightning damage can take weeks to show up.

[UbonEagle]

Yeah have seen these MOVs in industrial but never knew their purpose.

For the price mentioned above 800bt I would have thought just replacing a fleuro light would be cheaper ?

However for (expensive) device protection I can see their usefulness...would you install in the wiring behind a power point for example to protect any attached device's ?

[carlyai]

21 hours ago, carlyai said:

My wife just told me that many houses around suffered electrical damage. Mainly fluro light damage.

My MOVs are expensive. Might have to find some cheaper ones with good specs. if I can. If I can remember they were about  B800 each. I think they were 4square brand but have to check.

Must have forgotten to post this comment.

Schneider DIN mounted Surge Suppressor is what I had. At over B2000 a pop makes it B6000 for 3 suppressor.

@crossy what front end beasts do you have? If I remember they were coloured racing red. Think they are a lot cheaper. I'd like to compare your MOV specs against the Schneider if you can give me the MOV number please.

[Crossy]

46 minutes ago, UbonEagle said:

However for (expensive) device protection I can see their usefulness...would you install in the wiring behind a power point for example to protect any attached device's ?

 

Lightning protection is a phased operation.

 

Big but relatively slow beasties on your incoming supply to take the majority of the energy then smaller ones in sub-boards if you have them and good quality plug-in ones at your sensitive kit to mop up the dregs.

 

You have to be a bit careful installing them in outlets etc. as they can fail in a somewhat pyrotechnic manner and we don't want to protect the TV but burn down the house. As I noted we have loads of the little cheap ones in our LED ceiling fittings, fixed units on the solar inverter and quality plug-in units on the TVs and computers.

 

Nothing is going to save you from a direct hit to the LV supply but you can save a lot of grief from "near" strikes.

 

Some years ago I was working on the PUTRA LRT in KL, the operations centre had a fancy "active" lightning protection system with huge buried earth mats. I had just finished some work in the communications room and was heading out to the car, it was belting down so I stood in the shelter waiting for it to ease off. There was a flipping great bang as a strike hit just outside the car park closely followed by a somewhat panicky PUTRA chap running out yelling "comms fail, comms fail" (this is a fully automatic railway). Entering the comms room I was greeted by an entire rack of red "fail" lights. We used all the spares getting essentials back up. Evidently the lightning protection system didn't.

 

[carlyai]

47 minutes ago, UbonEagle said:

Yeah have seen these MOVs in industrial but never knew their purpose.

For the price mentioned above 800bt I would have thought just replacing a fleuro light would be cheaper ?

However for (expensive) device protection I can see their usefulness...would you install in the wiring behind a power point for example to protect any attached device's ?

@crossy is your man. From memory he installed them in power points, but you have to be a bit careful less you grab something exciting. I think he even had a picture.

Sorry. Must have nearly posted together.

Edited July 29, 2020 by carlyai
Addittion

[Crossy]

I'll dig out photos when I get home from work.

[RichCor]

23 minutes ago, Crossy said:

I'll dig out photos when I get home from work.

alright! Family photo time!

[Crossy]

As promised.

 

These are the units we have on our incoming supply.

 

 

These are the DC ones on the solar panels.

 

 

And we have these little guys scattered elsewhere but you must ensure they are in a fire-resistant enclosure - 11 Baht a pop at NPE http://www.mynpe.com/mynpe/more.php?data=116450101007

 

 

[UbonEagle]

Cheers @crossy supreme source of electrical know-how as always.

So the red surge protection devices substitute an RCBO ?

I will PM you some day re my current system...if I can get back over there...stuck in Oz at work but it's not the worst scenario atm, plenty of people in worse situations ????

 

[carlyai]

3 hours ago, UbonEagle said:

Cheers @crossy supreme source of electrical know-how as always.

So the red surge protection devices substitute an RCBO ?

I will PM you some day re my current system...if I can get back over there...stuck in Oz at work but it's not the worst scenario atm, plenty of people in worse situations ????

 

Nice place to be stuck in....and with a job. Good planning. ????

[sometimewoodworker]

3 hours ago, UbonEagle said:

So the red surge protection devices substitute an RCBO ?

No, no, no, no.
 

A surge protector does a completely different job to an RCBO you need an RCBO you probably want a surge protector, you should have both as well as an under over limit control.

 

main incoming supply includes surge protector 

 

main workshop CU includes RCCB and under/over limit control.

Edited July 29, 2020 by sometimewoodworker

[RichCor]

44 minutes ago, sometimewoodworker said:

4 hours ago, UbonEagle said:

So the red surge protection devices substitute an RCBO ?

No, no, no, no.

I don't think he meant "does the same thing as", but meant "fits in the same space as". Poor choice of wording me thinks.

[sometimewoodworker]

1 hour ago, RichCor said:

I don't think he meant "does the same thing as", but meant "fits in the same space as". Poor choice of wording me thinks.

It’s possible but even then for the main house surge protector I have you can fit 2 into the space of my RCCDs/RCBOs
 

With writing and the various levels of knowledge here we have to assume the what was written was what was intended. While UE may not have intended “substitute” it is what was written and another reader using this for guidance could make a nasty mistake.

[Crossy]

11 hours ago, UbonEagle said:

So the red surge protection devices substitute an RCBO ?

 

As others have noted, they don't do the same thing you should install both.

 

Space wise my big red chaps (100kA) are actually about 1.5 slots wide so 2 fit in 3 slots.

[carlyai]

12 hours ago, sometimewoodworker said:

No, no, no, no.
 

A surge protector does a completely different job to an RCBO you need an RCBO you probably want a surge protector, you should have both as well as an under over limit control.

 

main incoming supply includes surge protector 

 

main workshop CU includes RCCB and under/over limit control.

@sometimewoodworker Can you measure the width of your surge protector please? I can't find a profile diagram for them. 

I had Schneider QOSPD20 and the front width is 16mm. I'm not sure I can fit your Tomzn suppressor into the Schneider space. The Schneider are over B2000 each, so too expensive.

 

EDIT

Don't worry found a pic. About 5.5 cm for 3 phase so should fit.

Edited July 30, 2020 by carlyai

[maxpower]

29 minutes ago, carlyai said:

I had Schneider QOSPD20 and the front width is 16mm. I'm not sure I can fit your Tomzn suppressor into the Schneider space. The Schneider are over B2000 each, so too expensive.

Your distribution board is plug-on. You either buy replacement Schneider plug-on surge protectors or fit a separate din rail box to house the cheaper DIN rail devices.

[UbonEagle]

Cheers guys yes I get the drill, different devices with different functions. 

While our relatively new 3 phase system was put together with good quality components (and no issues with breakers tripping etc), it's definitely missing a few bits & pieces. Look forward to getting back and sorting out.

[carlyai]

22 minutes ago, maxpower said:

Your distribution board is plug-on. You either buy replacement Schneider plug-on surge protectors or fit a separate din rail box to house the cheaper DIN rail devices.

YES I remember now, plug on not DIN. Thanks.

I wonder if they still clamp at all even though the unit says replace?

 

 

 

 

[maxpower]

44 minutes ago, carlyai said:

I wonder if they still clamp at all even though the unit says replace?

There will be a safety device inside the surge protector to open the circuit when the MOV fails and begins to get hot. The indicator tells you that the safety device has operated and the MOV is disconnected.

 

Consider something like the device below mounted in a separate enclosure. It could share your existing 63amp 3 phase breaker using suitable size connecting cable.

400 - 1000 Baht depending on source.