Search results for query: *

Instantaneous trip without jeopardizing coordination is possible by dedicated arc-flash protection, based on simultaneous sensing of arc-flash light and overcurrent. Very common in some countries, both in utility as well as industrial installations (MV and LV).

I agree with "jghrist" and "davidbeach". Some people seem to have serious attitude problems related to light & overcurrent based systems which provide the fastest protection and lowest incident energy. Because several major manufacturers are turning to this well-known technology, there is a...

IEC 62271-200: "Application of suitable current-limiting fuses in combination with switching devices can limit the short-circuit current and minimize the fault duration. It is well documented that the arc energy transferred during such tests is not predictable by I2t. In the case of...

"Arc flash is only relevant when someone is working on the energized gear." I strongly disagree. Don't you think about a) damage to the equipment and b) costs due to interrupted processes? Safety first, but it is definitely not the only issue. There are better solutions than maintenance switch.

Current limiting fuse is a good option only if you can guarantee that the current will be high. In low voltage systems the arcing current is often less than 50% of the bolted fault current. "In the case of current-limiting fuses, the maximum arc energy may occur at current levels below the...

Arc eliminators can detect (optical detection and very fast overcurrent detection) AND eliminate the arc within a few milliseconds. Manufacturers say that arc burning times of 2ms (LV) and 5ms (MV) can be reached. Thus a combination of a crowbar and a CL fuse would provide 1) very short arc...

At low voltage the arcing current is often less than 50% of the bolted fault current (can be less than 30%). No wonder an IEC standard puts it this way: "In the case of current-limiting fuses, the maximum arc energy may occur at current levels below the maximum interrupting rating." (IEC...

dpc wrote: "The optical systems promise faster response, but there are possible issues with retrofit of optical sensors on existing equipment." I would like to hear what kind of issues there are. As far as I know, retrofit of optical sensors is rather easy. Optical systems (often combined with...

Use either dedicated arc-flash protection relay or a numerical relay with arc-flash option. With trip initiation time of only a few milliseconds you increase safety and significantly mitigate damage to equipment and thus limit costs due to process interruption. Choose fast circuit-breakers...

I believe E.J. Coster has examined these issues.

Time to find out how optical sensor based arc-flash protection could help? It is de facto standard in some countries. If only a very short arcing time is allowed, the answer is arc eliminator. Manufacturers with a lot of experience: ABB and Vamp.

Current-limiting fuse is very fast IF the current is high, but if the current is lower than bolted-fault current, as it is often in arcing faults occurring in LV systems, ... You could consider dedicated arc-flash protection products to guarantee high speed protection --> low incident energy.

I believe VAMP has been on the arc-flash protection market more than 10 years, the first years with a different name. For special purposes both VAMP and ABB sell arc eliminators that can extinguish the arc within 2-5ms. With conventional optical sensing based protection the arcing time is the...

See IEC 62271-200. There you can find some information. In some European countries de facto standard in arc-flash protection is light and current based protection (optical sensors). This method is recognized by the IEC standard.

Has anybody studied how Ripple Control Signal behaves during power system disturbances, e.g. voltage dips? Does the signal totally disappear or attenuate very much? For my purposes, a continuous signal is needed.