Protection for three phase power, one phase drops.

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mdakxotaz

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Have a situation with a condo building. The service coming in is three phase from utility company, what happen is one of the phases came loose from the line on the street. The motor starters and control board for the condos elevator were damaged. Utility company is not taking responsibility because they state that protection from this situation is needed after their service.

Has anyone come across a similar situation or could direct me to the article which would cover a problem of this type? Condo owners are out a great deal of money if it is their responsibility.

Leo.
 
I am going to leave this open for a short while, but we have to tread carefully. Forum rules forbid the use of information obtained herein from supporting one side or the other in a legal dispute. If the discussion starts heading in that direction, the thread will be removed completely (not just closed).

So please stay on topic, or please refrain from commenting. The topic is, what does the NEC say about protection from open circuit faults, such as the one described above?

I do not know the answer to the question. My guess is that the NEC is not going to help. I suspect that there is no NEC requirement that dictates the point at which a system shall be protected against any given possible failure scenario. But I may be wrong about that.

 
This is a relatively common situation. The responsibility of installing protection against "single phasing" may be found in your state's utility commission requirements.

I also do not believe this is addressed in the NEC.
 
mdakxotaz said:
Has anyone come across a similar situation
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Oh yeah. Importance of protective relaying is directly porportional to the cost of the equipment at risk

mdakxotaz said:
Condo owners are out a great deal of money if it is their responsibility.
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I can't tell you anything about the contract with the utility as to who is responsible. And my experience is generally industrial, not involved with whatever a condo is considered.

With that in mind:
Protective relaying and coordination is extremely important. Loss of phase is just one. One can protect against most any scenerio, it just costs money. As for how much the owners want to spend, well that depends on how much they are willing to loose and balancing the risk against the dollars.

mdakxotaz said:
or could direct me to the article which would cover a problem of this type?
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I'd probably start with the IEEE color series. The Gray is commercial buildings (I think - I don't have it). Buff is Protection and Coordination. Red is Electric Power Distribution

cf
 
It is a design issue only, and not regularly addressed in residential construction. In industrial applications, single phase protection of motors or the entire service itself is designed into the project to protect the owner.
There are many relays available on the market for service entry applications and locally installed at the varied motor starters.
 
BTW, the same situation happens in single family residential construction, where an overvoltage relay could be installed to protect from a lost neutral, but it is not generally cost effective.
 
As mentioned, phase protection is very common. I think it is a design issue, and not necessarily covered by the Code.
www.time-mark.com is one source. Square-D, ABB, etc, all make various types of phase relays. I would have thought that it would be part of the elevator controls.
db
 
mdakxotaz said:
Has anyone come across a similar situation or could direct me to the article which would cover a problem of this type? Condo owners are out a great deal of money if it is their responsibility.
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Leo as the other have said it is not an NEC requirement.

I suggest you go to the web site of the power company involved, look for a download of their "Service Requirements" it lays out all the rules.

Here is a bit from a local power company.

803. Motor Protection

A. Protective Devices GeneralNSTAR strongly recommends that all motor installations
be adequately protected to prevent improper operation,
equipment damage and personal injury which might result
from abnormal conditions occurring in NSTAR?s service
facilities or the customer?s wiring system.

B. Protection Against Single Phase Operation
Three phase motors shall be protected against the
possibility of loss of any phase of the supply circuit.
NSTAR does not provide protection against loss of phase
conditions.

C. Undervoltage Protection
All motors requiring protection against the application of
full voltage at starting, or motors that would endanger life
and/or property by restarting after a service interruption
and a return to normal voltage shall be provided with
undervoltage protection. Such protection devices should
ensure that, with either undervoltage or no voltage, the
motor will be disconnected from the line or the starter
will be returned to the ?off ? position.
NSTAR recommends the use of time-delay undervoltage
protection since instantaneous undervoltage protection
may operate on momentary voltage fluctuations.
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Thanks guys, very helpful. Have been looking in the NEC and can't find information regarding this situation. Happy to hear im not the only one :cool:.

I would agree that this is a design issue and protection for this type of situation should have been in place by the contractor.

Charlie this was not for me, overheard it at work. I was curious for an answer as I may be put in this situation some day down the road. I will be more careful on how I word questions in the future.
 
Any utility worth it's salt will have a clause in the paperwork that a property owner will sign upon starting up a new service stating their limitations of liability. It basically states that they will do their darnedest to keep the power operating properly, but they're not liable for damages if it doesn't.
Sometimes, state utility laws will mirror this clause.
 
iwire said:
Leo as the other have said it is not an NEC requirement.

I suggest you go to the web site of the power company involved, look for a download of their "Service Requirements" it lays out all the rules.
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I agree with Bob, here is a bit from IPL's Goldbook, Section 147:

It is the customer's responsibility to provide and maintain protection for multi-phase equipment that may be adversely affected by a loss of phase condition. The Company assumes no liability for equipment damaged by a loss of phase condition.

This is almost the same as Section 148:
​
It is the customer's responsibility to provide and maintain protection for multi-phase equipment that may be adversely affected by a phase reversal condition. The Company assumes no liability for equipment damaged by a phase reversal condition. :smile:​
 
Really there is noting in the NEC say anything about the 3 phase protection however many POCO did mention very clear in the regulation book as Bob and Charlie highlight it.

It the same way with my POCO's { both Wisconsin and EDF} they really highlighted that part.

It is common to buy a open phase protection relay which it is pretty common one to get and some industrail / commercal customer may get the undervoltage protection as well.

So it pretty much common sense there and I know there is a hidden golden rules with elevators must have phase loss / reverseing protection there.

Merci,Marc
 
A while back I installed three small relays with 120 volt coils, each connected to a "phase".
I connected the control voltage of a 200amp relay in series with the NO through the three relays.
The 200amp relay controlled a separate panelboard for the critical loads they wanted to prevent having a single phasing issue.
Crude but it worked.
 
jrannis said:
A while back I installed three small relays with 120 volt coils, each connected to a "phase".
I connected the control voltage of a 200amp relay in series with the NO through the three relays.
The 200amp relay controlled a separate panelboard for the critical loads they wanted to prevent having a single phasing issue.
Crude but it worked.
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I'm not sure how to word this correctly or even if what I'm wondering can be true, but here goes.

You see a lot of posts talking about an "open delta" and about the 3rd phase being developed when only using 2 phases and a neutral. Could you have a situation where a phase is dropped but there is enough potential being developed to keep the small relay coil energized thereby keeping the power on during a single-phasing issue?
 
hardworkingstiff said:
I'm not sure how to word this correctly or even if what I'm wondering can be true,
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I have all the same thoughts about his home brewed set up. :cool:

When I have had to do this I have just used line monitors like this

3UW89.JPG


or this

3UW91.JPG
 
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