Wouldn't HK power read 380 between L1 and L2? The thread starter reports 220 L1 to L2. That's the part that seems bizarre to me.

omg, I actually heard of it too, now you remind me. but that's my reading, without loading. it read much higher when there's load though (if I leave all the circuit breakers on)

 

One of the first things I did in a industrial building or complex, was to seek out someone or somebody that looked after general day to day building maintenance, they may not have come with any kind of extraordinary technical ability, but at least they knew where everything was, and if there was a sub-station or at least a locked-off room where the high voltage came into for local distribution, or at least if there was any other anomaly happening in any part of the building/complex.
As already suggested, do you need 3phase? Also do you require a grounded neutral for the equipment?
Max.

Today I'll be able to make some calls, and yes when the neutral is provided we use it.

 

Of course it provides power, it is a 3rd phase, just that one is referenced to Earth ground.
Ignoring the grounded phase, it works like any other delta secondary.

@thom kurt
But the fact there is 3 breakers probably it is not this configuration this time.
If it involves a lot of red tape to find out, maybe just a call to the local provider may be possible to get an answer or at least a suggestion.
If a large industrial building, they are going to have their own sub-station, power house or room for all incoming power.
There are not typically individual 3ph breakers, one trips, the other two trip.
P.S. Where are you located?
Max.

Oh... if there's a delta secondary, would that be possible cause of the voltage dropping?

 

I already made some calls, hopefully they'll find someone to check the utility room soon enough. Or we'll just have to get power from the other two phase (which will lead to even more complicated communication with some other parties working in the other areas of the flat, oh my)

But what mostly interests me is that the 4V that I measured from L3 (to phase and neutral), I'm not quite worried about my project actually because providing power is not our responsibility (though we are expected to use it right and safely). I've read a considerable amount of articles up on this site, never did I really have the chance to run into an actual scenario, it's just fascinating.

 

Hello All,

As I try my best to describe the situation in the title, I have a project that I need to setup a A/V rack in an industry building. In the very beginning of my project I found one of the 3 phase circuit breaker boxes provides no power. Since it leads to the closest socket I can use I meant to find out why and gather more information before I talk to my client about the issue. I did some basic measurement, checked all the circuit breaker, and finally I turned off all the individual circuit breakers and focused on the main switch which has three leads and a ground connection. L1 to L2, L1 to ground, L2 to ground, all measured 220V, on the other hand L3 measure no voltage. That cable came directly from outside.

Q1. is it safe to say that there's problem from the floor's or building's former room?

Q2. My colleague suggests that we should just swap the cable to get power from one of the other two phase, as long as we're sure the power consumption is within safety range, do you agree?

PS. obviously i'm from the other planet and not a pro, thank you so much for bearing with me, and thank you so much for your advice, much appreciated. Let me know if you think I should provide more info.

 

It is a 3P+1N circuit breaker. It will have 6 contacts, 4 inputs and 4 outputs.

3 Phase + 1 Neutral.

Out of 3 Phases one Phase has failed. Maybe the fuse used for that phase has blown.

 

Hi: Caution Caution Caution!!!! Before you go about switching phases you need to understand that any 3P motors being powered from this system will change direction. If one phase is zero volts you should try to determine why it is so. Does the system contain fuses ? Often, the supply panel will have fuses and one of them may have failed. If a breaker is present, check the input side voltage to make certain the voltage is present at the line. You may need to go deeper in the system to determine why the phase is out. Most systems today are delta connected so that phase voltage equals line voltage. You should measure 220 volts between any two phases. Best regards,

Phranzdan

 

Hi: Caution Caution Caution!!!! Before you go about switching phases you need to understand that any 3P motors being powered from this system will change direction. If one phase is zero volts you should try to determine why it is so. Does the system contain fuses ? Often, the supply panel will have fuses and one of them may have failed. If a breaker is present, check the input side voltage to make certain the voltage is present at the line. You may need to go deeper in the system to determine why the phase is out. Most systems today are delta connected so that phase voltage equals line voltage. You should measure 220 volts between any two phases. Best regards,

Phranzdan

Yes, that's my intention, I'd love to find out what is happening exactly before I jump into conclusion. Though I mentioned L3 measured "Low" in the title, I accidentally misled everyone by providing wrong info in my first thread.

Anyway, as I expected, no one would answer to the problem any soon, the building office is acknowledged and is having me standing by the phone.

 

I just going to ask some stupid questions to check , and make sure this is not a "whoops" problem.

1. What color are the wires ?
2. Is the ground bare copper or does have a plastic wrapper ?
3. Did you check ground to the conduit / metal box ?

 

I just going to ask some stupid questions to check , and make sure this is not a "whoops" problem.

1. What color are the wires ?
2. Is the ground bare copper or does have a plastic wrapper ?
3. Did you check ground to the conduit / metal box ?

Also :
4. Did you check power to the metal box/ conduit ?

 

Also :
4. Did you check power to the metal box/ conduit ?

Can 3-P energy meter cause the problem if it is faulty ?

 

Can 3-P energy meter cause the problem if it is faulty ?

Depends on what you mean by "Faulty" , but sure why not ?

Right now we're still at the outlet box, so one thing at a time

 

I just going to ask some stupid questions to check , and make sure this is not a "whoops" problem.

1. What color are the wires ?
2. Is the ground bare copper or does have a plastic wrapper ?
3. Did you check ground to the conduit / metal box ?

- They're in old style color coding, Red, Yellow, Blue, Black & Yellow/Green
- Ground is wrapped black
- I'm not sure how to answer that, do you mean the ground and neutral are effectively grounded? (I'd say apparently yes, the terminal is quite noticeable, but I honestly didn't check them carefully)

There's no stupid questions, thank you for your input

 

Also :
4. Did you check power to the metal box/ conduit ?

I checked phase to ground terminal, and phase to neutral, single digit value towards L3, if that's what you mean.

 

The idea of grounding one phase of a delta transformer was new and confusing to me. The following paper helped make it a little clearer to me, so I'll share it in case it helps any other readers follow along (I'm not claiming that this is what's going on here - I have no clue what's going on. I'm just sharing this as a general reference.)

http://static.schneider-electric.us/docs/Electrical Distribution/Switchboards/QED-S/2700DB0202.pdf

 

It may be expedient to book a quick service call from an electrician and he should confirm everything for you in short order.
Max.

 

- They're in old style color coding, Red, Yellow, Blue, Black & Yellow/Green
- Ground is wrapped black
- I'm not sure how to answer that, do you mean the ground and neutral are effectively grounded? (I'd say apparently yes, the terminal is quite noticeable, but I honestly didn't check them carefully)

There's no stupid questions, thank you for your input

The neutral is grounded at the service panel , so , yes the neutral is grounded. What I mean is that , the metal conduit that the wires are housed in should also be grounded, that metal conduit is a more certain ground , then the black/yellow wire (we don't know where that goes yet , because the conduit can't be ungrounded. Measure between all of the wire and the metal box , with your multimeter, it should read 120 on three of the lines and zip (zero) on the last. Then check for continuity between the dead wire and the metal box, it should be 0 ohm's. If that is the case your good to go, and the dead wire is ground or neutral, and you have three 120 volt three phase wires , 240 between them .

My suspicion is that the black/yellow wire does nothing not even a ground, or you have two phase in the box, not three phase.

P.S. I am an electrician, in california

 

The neutral is grounded at the service panel , so , yes the neutral is grounded. What I mean is that , the metal conduit that the wires are housed in should also be grounded, that metal conduit is a more certain ground , then the black/yellow wire (we don't know where that goes yet , because the conduit can't be ungrounded. Measure between all of the wire and the metal box , with your multimeter, it should read 120 on three of the lines and zip (zero) on the last. Then check for continuity between the dead wire and the metal box, it should be 0 ohm's. If that is the case your good to go, and the dead wire is ground or neutral, and you have three 120 volt three phase wires , 240 between them .

My suspicion is that the black/yellow wire does nothing not even a ground, or you have two phase in the box, not three phase.

P.S. I am an electrician, in california

My colleague has a revised version of the reading:

L1-L2: 382
L1-L3: 212
L2-L3: 222

L1-N: 216
L2-N: 218
L3-N: 3

I don't know what has happened, but that certainly changed things right?

 

It may be expedient to book a quick service call from an electrician and he should confirm everything for you in short order.
Max.

If it is certain that the fault happens in the flat, my client will have to pay a technician to fix it. If it is not, he won't pay a dime to no one. The building management office will have to take care of it.

If I be able to suggest that the fault happens in house, everything will go much more smooth.

And my client would love it for us to just swap the cables to an un-used breaker from L1 / L2 to just get things going without bothering him. Because if it screw up the system, it's all on me.

 

We and client came to an understanding, eventually we did the swap, now using L1 and everything working just fine... for now lol

Thank you everyone for your inputs, thank you.