New SPD Model

Started by Kent0, March 06, 2014, 02:10:11 AM

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Kent0

As good at the Midnite SPDs are there is a serious gap in the product line when it comes to protecting items connected to a sub-panel where neutral and ground are not connected. This is particularly an issue when the sub-panel is in a remote building with its own grounding electrode. I'd really like to see a SPD for protecting L1, L2, and neutral; it could also be used in the main panel for a three-phase system. The attached sketch shows where the unprotected wire is located and how to correctly provide surge protection at a 120/240 split phase panel.

Halfcrazy

Kent
That is the 3 phase model and it is at ETL right now. Has 3 legs so we can protect L1, L2 and Neutral

Ryan
Changing the way wind turbines operate one smoke filled box at a time

Kent0

That's excellent news! I hope after it is approved the instructions for the existing SPD models will say that they should not be used in sub-panels where the neutral and ground are not connected together or will show how two (non-three-phase) SPDs can be used to protect L1, L2, and neutral.

boB


OR, L1, L2 and L3

hi Kent !
K7IQ 🌛  He/She/Me

niel

being it is for surge suppression, would it matter what ground it gets diverted to? i see nothing wrong in grounding that spd to the ground rod at that building.

vtmaps

Quote from: niel on April 30, 2014, 11:35:30 PM
being it is for surge suppression, would it matter what ground it gets diverted to? i see nothing wrong in grounding that spd to the ground rod at that building.

It could matter (with lightning, anything can matter).   

In the event that lightning strikes the ground near your system, the two ground rods could have 1000s of volts difference.   The SPDs become conductors at relatively low voltages, and would allow current to flow from one ground rod to the other through any of the current carrying conductors. 

If you want to 'crowbar' your ground rods, IMO it is better to do it with a non current carrying conductor.

--vtMaps

niel

so what it'll present voltage differencials between grounds as it is a surge current being grounded out and it's not creating a ground loop on the main power wires. don't try to school one who made you aware of ground loops in the first place.

Halfcrazy

Quote from: vtmaps on May 01, 2014, 05:49:46 AM
Quote from: niel on April 30, 2014, 11:35:30 PM
being it is for surge suppression, would it matter what ground it gets diverted to? i see nothing wrong in grounding that spd to the ground rod at that building.

It could matter (with lightning, anything can matter).   

In the event that lightning strikes the ground near your system, the two ground rods could have 1000s of volts difference.   The SPDs become conductors at relatively low voltages, and would allow current to flow from one ground rod to the other through any of the current carrying conductors. 

If you want to 'crowbar' your ground rods, IMO it is better to do it with a non current carrying conductor.

--vtMaps

VTMaps
I think I agree if there are multiple ground rods they really need to be bonded together. Induced voltage from lightning is a nasty thing and I have had several paid (By me) educations on this subject as I live on a rock at a high elevation.
Changing the way wind turbines operate one smoke filled box at a time

niel

#8
it has nothing to do with the function of the spd as it could still send a surge to ground to that 1 rod.

i was always the advocate of the bonding of ground rods, if close enough in proximity and this is a separate issue from that of the spd functioning to that ground rod as it matters not if it's a bonded or unbonded group of rods or even a separate rod dedicated to the spd. it will function. more rods tied does lower the resistance to ground and may allow it to perform better, but this is not required for the spd.

vtmaps

Quote from: Halfcrazy on March 06, 2014, 06:24:20 AM
Kent
That is the 3 phase model and it is at ETL right now. Has 3 legs so we can protect L1, L2 and Neutral

Ryan

I don't see the specs for the new 3 phase SPD on your website, but previously you wrote:
Quote from: Halfcrazy on September 15, 2012, 12:24:50 PMWe are working on a 3 phase version. The downside is there will be less protection per phase as we can not fit any more MOV's in the case. I prefer on wind turbines to use 2 of the SPD's to get max protection.

--vtMaps

niel

btw ryan, i should add that you may benefit from a faraday cage type of arrangement in addition to many rods in the circumstance of being more prone to lightning as an spd or even many spds will only do so much.

Robin

The SPD products have been at ETL for about 7 months now. We sent the three original SPD's as well as three new versions. 208 3PH, 480V 3ph and 1000VDC.
ETL has been messing around and costing us tons of money for a long time now. I finally stopped all testing on the three new versions due to costs. We are now up to about $80,000 in ETL testing and they are not done. They are not communicating very well either, so to limit our expenses, we are only finishing the three original SPD's at this time. When ETL gets more reasonable on costs we will finish the new three versions. If that never happens, we may send them to another agency such as UL, TUV or MET or CSA.
We are in the process of sending our Birdhouse to UL now. We have been using ETL exclusively since the beginning, but now feel we need to expand our agency testing to others.
I agree that the three phase will be nice to protect the neutral also. The present devices are stronger though. We do a great job of protecting equipment according to reports from the field. We have had only a few SPD's destroyed in the last few years. We tried to make them indestructible and it appears that has been working quite well.
The UL standards have some test requirements that will require series breakers to protect the SPD's from burning up. These tests are anything but reality, but we have to pass the tests regardless in order to put the ETL label on them. We will have more on this subject when and if ETL ever finishes their testing. In the mean time they do continue to send invoices on a regular basis.
Robin Gudgel

boB

Quote from: vtmaps on May 01, 2014, 05:49:46 AM
Quote from: niel on April 30, 2014, 11:35:30 PM
being it is for surge suppression, would it matter what ground it gets diverted to? i see nothing wrong in grounding that spd to the ground rod at that building.

It could matter (with lightning, anything can matter).   

In the event that lightning strikes the ground near your system, the two ground rods could have 1000s of volts difference.   The SPDs become conductors at relatively low voltages, and would allow current to flow from one ground rod to the other through any of the current carrying conductors. 

If you want to 'crowbar' your ground rods, IMO it is better to do it with a non current carrying conductor.

--vtMaps


The reason you should connect the SPD ground close to the E-panel and electronics is because the SPD's basic clamping protection function is to keep the system component's insulation from arcing-over.

If the SPD's ground is connected thousands of volts away form the E-panel and component chassis grounds, then the electronic components run the risk of breaking-over and hurting the units.  i.e.  the system electronics ground can be momentarily MUCH higher than the ground rod while the lightning stroke and their high induced electric fields are active.

Each listed component should be tested at the factory (Hipot) to make sure it can withstand a certain breakdown voltage between its chassis ground terminal and all of the other wires and connections in the unit.
Adding an SPD between the chassis ground and the hot wires, tries to keep the common mode lightning induced voltages below that hipot test voltage.  The Classic, for instance, is hipot tested up to around 2,270 volts DC.
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niel

bob,
that's a good argument for putting another leg of another spd from neutral to ground, but all spd legs must be able to go to ground. it doesn't change what i said as he can put it to that ground rod and putting it to neutral instead of ground will leave all at the potential to be far above ground in volts. spds work against ground as that's where the surge is supposed to go to.

boB

One problem/question is "what is ground" ?  Ground isn't always where it should be or the voltage you think it might be compared with other points in the circuit.  And AC neutral is grounded too but I'm not sure if the NEC will allow SPDs to connect to neutral ?

But yes, the lightning current is trying to get to ground and it will get back there through the
ground line.  The situation that the SPD tries to prevent is to keep that current from going through
the sensitive non-ground circuitry on its way back to real ground.
K7IQ 🌛  He/She/Me