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# Arc Quenching Device for Arc Flash Mitigation

## Arc Quenching Device for Arc Flash Mitigation

(OP)
Does anyone have any experience or knowledge with the use of arc quenching devices in LV switchgear to reduce incident energy levels?

I am vaguely familiar with them being installed in new LV switchgear applications and advertised to quench arch in less than 4ms without having to rely on breaker opening time thus significantly reducing incident energy levels.

All though the application seems fairly straight forward I have not seen or heard of many of these being installed in switchgear applications. Perhaps because it is a new technology or maybe because there is another reason they prevent them from being a viable solution for AF mitigation in certain applications?

Based on the basic principles and application of these I would expect to see them more widespread instead of some of the other techniques I’ve seen implemented for mitigation (IE moving main breakers, AF relays etc...) but I have not seen many of these applied?

### RE: Arc Quenching Device for Arc Flash Mitigation

Can you provide a link to what you're looking at? No sense in everyone guessing.

### RE: Arc Quenching Device for Arc Flash Mitigation

Are you talking about a device that shorts out the 3-phase power? If so, it still needs all the arc detection equipment that tripping a breaker needs. From what I've seen, it more or less uses a re-purposed power circuit breaker to close and short the bus bars together.

### RE: Arc Quenching Device for Arc Flash Mitigation

Dear Mr rockman7892
It is a standard practice to use an ACB with sufficient short-circuit capacity to short out the busbars to earth as an earthing switch.
Note: This ACB is NOT installed with any over-load, instant trip or direct-acting release. The intention is to close and remain closed, once it is activated.
Che Kuan Yau (Singapore)

### RE: Arc Quenching Device for Arc Flash Mitigation

Typically not a circuit breaker but a much less expensive high speed grounding switch. The most expensive aspect of a circuit breaker is its fault interrupting capability. These ground switches never need to interrupt anything.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

### RE: Arc Quenching Device for Arc Flash Mitigation

Dear Mr davidbeach

1. It is typically constructed identical to an ACB; where the poles are covered by heavy arc-chute. The closing speed and force is identical to an ACB. It can close electrically by shunt release or manually when it is used as an earthing switch. It is due to the fact that very heavy arc occurs when closing; shorting all three poles to earth.
2. By definition, a switch does NOT close electrically. Normally, it is NOT expected a switch (without) heavy arc-chute and manually operated, would suit the application/requirement.
Che Kuan Yau (Singapore)

### RE: Arc Quenching Device for Arc Flash Mitigation

davidbeach - It would be a grounding switch in LV switchgear, which implies < 600VAC applications?

### RE: Arc Quenching Device for Arc Flash Mitigation

(OP)

Below are some links to the product I was referring to with each of these manufacturers making a similar product. The solution and operating principle is based on the arc quenching device initating a controlled 3-phase fault in order to shunt out the arcing fault and clear the arcing fault in less than 4ms. They all appear to use a combination of light and current sensing via arc flash relay in order to iniate arc quenching device.

My biggest question here is the need or consideration for an upstream circuit breaker to clear controlled 3-phase fault that the quenching device initiates. If we're talking about an application with the arc sensing and quenching in LV Switchgear on secondary side of a LV unit substation is there a need for a breaker upstream of switchgear on secondary side of transformer, or can the fuse or breaker on primary of transformer be relied on for clearing controlled fault initiated by quenching device?

https://new.abb.com/medium-voltage/apparatus/arc-f...

https://www.arcteq.fi/products/aq-1000-arc-quenchi...

https://www.eaton.com/us/en-us/catalog/low-voltage...

### RE: Arc Quenching Device for Arc Flash Mitigation

One obvious issue is the space required in the LV switchgear for the device. This could be an issue for retrofits. Adding a LV breaker upstream of the switchgear would seem to negate some of the advantages of the arc quenching switch. You could install an arc-flash detection relay in the switchgear and just trip this breaker. It would be a couple of cycles slower than the claimed speed for the arc quencher, but this generally shouldn't be an major issue. Also if you add a LV breaker upstream, it will then have its own incident energy issues. You are probably relying on fuses already for all types of system protection. I don't see that as a constraint. But imposing a bolted three-phase fault for any detected arcing fault could result in additional through-fault stress on your transformer.

It will be interesting to see if these devices catch on. I think the concept of deliberately creating a bolted fault is not the most appealing solution, at least at the superficial level. They have been around for several years, but I've never seen one actually in service.

### RE: Arc Quenching Device for Arc Flash Mitigation

If you don't want a secondary breaker and have a fused primary, suggest putting your arc-quencing device on the primary side. The primary fuse will operate too slowly to provide a benefit otherwise.

If primary protection is a breaker, use the arc detection relay on the secondary side to trip the primary breaker.

### RE: Arc Quenching Device for Arc Flash Mitigation

I would agree that it doesn't seem like a good idea to purposely short the secondary of a power transformer to clear the primary protection during an arc flash. Do the shorting on the primary side.

### RE: Arc Quenching Device for Arc Flash Mitigation

The one I saw was made by GE in an MCC, prior to the ABB purchase. This was a "vault", similar to an explosion proof enclosure, inside of which a bolted fault Arc Flash was purposely initiated to essentially draw most of the available energy into it and away from the initiating event down stream, until the upstream breaker could clear the fault. To make that happen, it had the light sensing arc fault detection systems woven throughput the MCC lineup, tied to a relay that initiated the arc inside of the vault and signaled the breaker to trip. GE's claim was that because this device "sucked up" the available arc flash energy, the MCC structure did not need to be modified to contain an arc flash event and no special certification was necessary. It was an interesting concept.

The vault was a one-time use device and I was told by a user who had them that the replacement vault was about $30k if you ever had an event. That was about 5 or 6 yeas ago now, so it's probably more than that. The claim was that this$30k option was LESS than buying Arc Resistant gear. That turned out to not be the case on the MCCs I was working on at that time.

OK, after typing this I looked at the links and they seem to indicate the same thing, so it appears to have moved out of GEs realm and into being separate stand-alone devices like the Arqtec (or it always was and Arqtec now sells it to Eaton and ABB). I do notice though that they claim it can be used TWICE, not once.

" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

### RE: Arc Quenching Device for Arc Flash Mitigation

(OP)
Thanks for all the feedback.

Let me give a basic example here to help explain my question above about need for upstream device tripping.

Lets assume a basic 480V service entrance where 480V Transformer and primary fuses are utility owned (metering on secondary)that then have service entrance cables that feed into a 480V Service entrance Switchboard with a main breaker.

Obviously in this case the Incident Energy level at the line side of the Switchboard main (and load depending on construction) is extremely high. In order to mitigate this AF Incident Energy Level lets suppose one of these Arc Quenching devices is located on the load side of the main breaker in the switchboard.

For an arcing fault occurring on load side of main I' suspect the Arc Quenching device to engage and thus eliminate the arcing fault as well as trip the main breaker in the switchboard as a result of the intentional 3-phase fault created by the arc quenching device.

But in this application what if the arcing fault occurs on the line side of the main breaker in the Switchboard. I'm assuming the same sequence of events would take place as mentioned above with the arc quenching device initiating 3-phase fault and the main breaker tripping. But what happens to the initial arcing fault on the line side of the main breaker that wont be cleared by main in switchboard? Would this re-develop into an arcing fault once the main breaker cleared the 3-phase fault (assuming the utility fuses did not clear)? Would this continue to be an arcing fault with a high incident energy associated with it until the utility fuses cleared?

Yes.

### RE: Arc Quenching Device for Arc Flash Mitigation

Yes, none of the detection and tripping schemes help protect the TX to line side of the breaker connection. You need an arc flash rated main breaker cell.

If you could put the arc quenching device ahead of the main breaker then it'd help, but I doubt it rated to do the arc quenching for the amount of time required to open the primary protection on the TX.

### RE: Arc Quenching Device for Arc Flash Mitigation

(OP)
LionelHutz

Good point about the need to connect it to line side of breaker in this application for it to be effective.

In looking at the Arcteq AQ-1000 device it says it has a rating of short circuit withstand (IEC rating) of 100kA for 200ms, 50kA for 1s.

Assuming in the typical application I described above I don't believe that utility fuses on primary would clear in less than 1s. It appears that when applying these devices you need to consider it in short circuit / coordination analysis to see how its rating compares to upstream device (similar to any other equip damage curve vs protective device)?

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