Fire Pump Motor burning out on loss of phase

[CanuckEngineer]

Hello All,

I have a client I am working for who on two separate occasions (within about 6 months) has had to replace a burnt out Fire Sprinkler Pump.

The pump supplier technician said the motor burnt out on a loss of one phase for an extended period.

Reviewing the upstream ATS controller (TornaTech supplier) it sure enough shows a loss of phase for an extended period.

My questions before calling for an expensive power analysis study do you guys have any comments on what may have caused the loss of phase condition? Upstream transformer winding problem? utility problem?, etc.

Thanks again for your help.

Regards,

RK.

 

[electricpete]

Instead of expensive study, maybe you could adjust the relaying to detect the condition, trip the motor and generate an alarm or flag:
* On large machines fed from load center equipped with CT’s, a 46 relay is not uncommon.
* For smaller motor perhaps an undervoltage trip would work. I remember jraef has made some good comments about protecting motors from single phasing in the past.

=====================================
(2B)+(2B)' ?

 

[electricpete]

Sorry, I just realized that with fire sprinkler pump there may be codes to consider before tripping anything. At least you can alarm.

=====================================
(2B)+(2B)' ?

 

[CanuckEngineer]

Thanks electricpete.

Good points.

We are guided by CSA (Canadian Standard Association). ESA - Electrical Safety Association.

Thanks,

RK.

 

[waross]

Motor protection relays with phase loss and phase unbalance protection are common in the refrigeration industry. Unbalanced voltages may destroy a motor, particularly a motor loaded close to the maximum rating. Phase loss is unbalance taken to the extreme. A three phase circuit may have equal phase to neutral voltages but unequal phase to phase voltages. As there is no neutral connection to a standard three phase induction motor, phase to neutral voltages are unimportant. A phase angle error will cause unequal phase to phase voltages and may cause motor overheating. Phase angle errors and unequal phase to phase voltages are often seen downstream from voltage regulator banks on long distribution circuits with single phase loading. It is often difficult to keep the three phases equally loaded at all times.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

Typically fire pump motors are required to "run to destruction", tripping off line is usually not an option regardless of the cause. So if you are losing one phase "for extended periods" on a system feeding a fire pump, I'd say that you are in severe need of a very detailed study. Phase loss like that is typically not intermittent, meaning it is either there or not there, it would not return. The only possibility then is that somewhere up stream, who knows how far, a fuse blew on one phase. Eventually someone replaced the fuse so it returned. If that could not have happened within your facility (and it should not be possible for it to happen on a system feeding a fire pump by the way), then that means it happened on the utility side. Nothing you can do about that, except... buy a backup generator for your fire pump and if the utility loses a phase while you are fighting a fire, the ATS switches over to the generator and keeps the pump running. Since you mentioned having read the phase loss on your ATS, it implies this is already in place. So the next question would be, why did the generator not come on when the utility phase was lost? That might indicate improper settings in the ATS as it relates to having to feed a fire pump.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[wroggent]

Could an over sized delta-delta transformer be placed between the utility and motor to avoid problems associated with loss of a phase on utilities side?

Sounds like your client's bigger issue to solve is having less fires.

 

[waross]

A neutral connected wye:delta transformer will supply the third phase in the event of a phase loss, but you must interupt the lost phase to prevent backfeeding into the grid. The backfeed, if permitted, will overload the transformer bank and may result in the transformer bank either blowing a fuse or overheating and failing.
A reverse current relay on each phase and single phase contactors may do the job of identifying and disconnecting the lost phase. A normal phase loss relay can identify the return of the lost phase and reset the single pole contactor.
And I'll echo jraef's question; Why didn't the transfer switch go to back-up power on the loss of a phase?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

A power study is just going to tell you that you lost a phase.

Losing a phase is typically either a blown fuse or a poor connection.

And I agree with the others. Why didn't the transfer switch transfer to backup power on the loss of phase?

 

[CanuckEngineer]

Hello All,

Sorry for the delay in getting back to this. Work pulled me away.

Thanks to everyone for the invaluable feedback.

After further review I made a mistake in my posting and I apologize.

Fist off the failed pumps were not the fire pump but rather the building sumps pumps. The operators attached to me the Fire Pump ATS controller trend logs and the failed sump pump repair invoice in the same email and I assumed they were the same. My bad.

So to answer people's questions the Fire Pump is back-fed by an ATS and the ATS did transfer upon loss of phase in every situation. So the Fire Pump is fine, however there is still a loss of phase issue.

I spoke with operations today and they told me that they did not fix any upstream fuses to clear the problem. Basically the loss of phase was there and then resolved itself.

Any thoughts here? Looks like a Utility issue right?

Thanks,

RK.

 

[jraef]

Phase loss and restoration without local intervention can only be attributed to something taking place up stream of your service drop, yes. You need a phase loss relay for your sump pumps if this happens often. If your ATS and generator only feed the Fire Pump, it would not engage on the utility phase loss unless the fire pump was being called for, ie a fire (signaled by a drop in sprinkler pipe pressure), if that's the reason they gave you the ATS logs.

But, here is the problem that still exists in my mind if the generator is for the entire facility. If there was a phase loss from the utility, the ATS should have called for the generator and switched over fast enough to have not allowed the sump pumps to be permanently damaged, even if they were running when the phase was lost. Single phase damage on AC 3phase motors is not immediate, it takes a while. I don't know what your system is, so this may or may not be the case, but it's worth checking into.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[CanuckEngineer]

Thanks Jraef.

There are multiple ATS' in the complex not just for fire pump.

I will see if I can get the logs for those as well and compare if their controllers saw a loss of phase and/or transferred.

Regards,

RK.

 

[itsmoked]

Time to get a thermal survey of [!]all[/!] your facility wire connections.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

See if you can determine if this was a complete loss of phase or a low voltage on one phase. I have had issues when the voltage on one phase went low enough for the transfer switch to ATS to transfer the load to the generator.
A low voltage on one phase will cause overheating of motors and can easily cause a motor loaded at or near capacity to fail.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[CanuckEngineer]

Hey Everyone,

Just as an update.

Our local utility company has agreed to install power monitors on the secondary side (here it is 600V l-l 3 phase).

I will let you know what we find out in about 2-3 weeks worth of monitoring.

Regards,

RK.

 

[waross]

If they are using an electronic KWHr meter, it may be just a matter of programming the meter.
I worked in an area where the electronic revenue meters were programmed by default to record demand, voltage per phase, current per phase, and a few other useful parameters. The values were recorded at 15 minute intervals. The maximum during the 15 minute window was recorded when applicable. Several times I was able to obtain a wealth of data by having the customer request a data dump. I would supply a floppy disk and a day or so later I would receive a spreadsheet with all the data for the previous two or three months, at 15 minute intervals.
The point is, no equipment had to be installed. The only expense to the utility was the technician's time to ravel to the site and back, and the time to plug in his lap-top and download the information.
Good luck. I am waiting for the results.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Artisi]

We are talking about fire sprinkler pumps aren't we? Interested to know why the pumps are running causing the motors to "burn-out" - fire pumps are supposed to run when there is a fire - not run hose systems to water the garden, wash your car of the floor. Suggest you overcome that problem to start with and the other problem becomes less of a problem.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[Sloss]

Nope, it's the Sump Pumps that have the problem.....

 

[Artisi]

Sump pump or pumps?

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[CanuckEngineer]

Hello All,

Sorry for the delay in getting back information on this.

What had happened this last month is that we had our Local Distribution Company (Utility-LDC) set up power monitors on the 600V side for 2 of the 5 buildings.

This is a large complex where we have 5 separate building comprising a centre, the buildings include, condos, hotel and a shopping centre.

We have the LDC bringing a single 27.6kV feeder to a 27.6kV switchgear, from there we have distribution feeders to each building and then they are stepped down through a single step down power transformer to 600V 3 phase. Each building then has its corresponding 600V switchboard feeding its corresponding building.

So we had the LDC provide a one month power monitoring for buildings A and B. I have attached the graphs and the summaries. They are reading Line to Neutral Voltage - 347V, Line currents and Neutral currents.

There were a couple of major interruptions on the LDC end due to a distribution transformer failure and I think maintenance.

My question, do you guys see any concern with the neutral currents shown? I know that the graphs are trended over a long period (the entire month) so it is hard to see specific information. I am working to get more detailed trends to submit.

Could the neutral currents be causing failures in the downstream equipment (i.e. sump pump issue which initiated this thread)?

Your input is greatly appreciated.

Thanks,

RK.