Company I work for is using 3*63A or 3*32A (on smaller jobs) distribution systems. It happened to us a couple of times that neutral conductor was broken/intermittent upstream from our distribution. A lot of expensive magic smoke escaped when some devices got hit with full 400 volts. Is there a device that protects from this kind of failure?
Floating neutral
- Thread starter Primoz Vozelj
- Start date
The best protection is metering the venue's power before tying in. Be sure everything upstream is solid before getting your distort set. If there's any issue, the venue should be providing an electrician to resolve.
TJ Cornish wrote some articles on best practices around this.
TJ Cornish wrote some articles on best practices around this.
I always check voltages before pluging in any equipment. Problem is last time everything was OK at the beginning, all voltages around 230volts, some 4 hours after, smoke started escaping. After some detective work we found out that neutral contact in 63A CEE plug was intermittent. It was almost a showstopper situation, lucky we had enough backup to replace broken equipment.
Metering with a load connected can help identify these sorts of issues, as well as excessive voltage drop. You should see similar voltages with and without an unbalanced load connected. Here in 120V land, I like using 1000W PAR64 fixtures as loads (convenient, close to resistive, and ~8A).
Connecting all your equipment phase-to-phase can prevent damage in these sorts of scenarios (the voltage won't ever exceed the phase-to-phase voltage under miswiring conditions), but is likely not a viable option.
As far as protection devices, you could probably rig something up with a shunt-trip circuit breaker (or relay) and voltage monitoring on individual phases, but I'm not aware of any packaged devices that do this in a single unit at the voltages and currents of interest here.
Connecting all your equipment phase-to-phase can prevent damage in these sorts of scenarios (the voltage won't ever exceed the phase-to-phase voltage under miswiring conditions), but is likely not a viable option.
As far as protection devices, you could probably rig something up with a shunt-trip circuit breaker (or relay) and voltage monitoring on individual phases, but I'm not aware of any packaged devices that do this in a single unit at the voltages and currents of interest here.
A floating Neutral, lost Neutral or a high resistance Neutral is often a problem in the US type system. The Neutral is the center tap of a 240V supply, providing two 120V poles or legs. While it's common to call them phases, it's an incorrect label. Anyway if the Neutral has a poor connect, the voltages won't divide evenly. So inste of a 120V:120V split you may get something like 180V:60V.
An open neutral can energize a safety ground and equipment chassis if ground is bootlegged to neutral downstream of the open.
If ground is bonded to neutral inside the distro (don't) and neutral is open, you can do worse than release smoke, (release blood?),
JR
If ground is bonded to neutral inside the distro (don't) and neutral is open, you can do worse than release smoke, (release blood?),
JR
If you've lost neutral on multiple occasions, somebody or something is doing something very wrong. In the 45+ years that I have been doing this I have never seen that. Ground on the other hand is a different story. If your going to continue down the troublesome neutral path an iso transformer will solve that problem as it generates its own neutral at the transformers output.
I've seen it happen a long time ago but it was from a "T" cam lock between two distro's. The ME was under the stage and stepped on it. He saw the PD meters change, 2 went high and one went way low. Up on stage a power strip in the guitar rig with a MOV inside blew first, the opening acts DX7 was next, a bass amp and then off stage at FOH. A Harrison console PS went, and the supply inside the Clair Console for the meters. In a second all that was gone. They had a backup supply for the Harrison but it did not have Phantom power, so I proposed a solution. It turned out the mains were out and blew a fuse as soon as we turned it on, but the Phantom power was working. Jimmy from Clair took my advice and wired the phantom out of one PS and into the spare. It worked. Mike was without meters on the Clair console but was ok to go. All at one hour to doors no less.
I would suggest something like this to a disconnect. ICM-Controls-ICM450-ICM450-3-Phase-Line-Voltage-Monitor.
I would suggest something like this to a disconnect. ICM-Controls-ICM450-ICM450-3-Phase-Line-Voltage-Monitor.