Dim lights, correct voltage

[hillbilly1]

Agree,though the frequency control is probably not quite that close, the legal limit here in the UK is from 49.5 cycles to 50.5, and the normal range is from 49.8 to 50.2 cycles.

I would expect that rules in the USA would differ, but still be somwhat similar.

UK grid frequency may be viewed here
http://www.dynamicdemand.co.uk/grid.htm

So we are still at a loss on the problem here then? What would cause low light output on several buildings that are fed from different transformers? I would say my techs meter calibration could be off, but it was verified by the utility. If not voltage, not frequency, then what? I would have said lamp life, but when they came back bright an hour later, that was ruled out.

 

[broadgage]

A badly distorted waveform might be the cause.
Electronic ballasts contain a capacitor charged by means of a bridge rectifier.
With a sine wave, the peak voltage is about 1.4 times the RMS value, and the capacitor charges up to nearly the peak voltage.
With a 277 volt supply and a sine wave, I would expect the capacitors to charge up to about 380 volts DC, the rest of the circuitry in the ballast being powered from this voltage.

If the voltage waveform is badly distorted, and resembles a sqaure wave, then the peak voltage might be only 1.1 times the RMS figure, in which case the capacitors might only charge to about 300 volts instead of about 380 volts.
That would substantialy reduce the light output.

If desired, the peak voltage may be measured.
Obtain a small bridge rectifier, rated at at least twice line voltage, connect to the output of this rectifier a capacitor also rated at at least twice line voltage.
A resistor of about 1 megohm should be connected accros the capacitor.
The voltage accros the capacitor is easily measured with a DC voltmeter, it should be about 140% of the RMS AC voltage.

Proper care should of course be taken, and a 1 amp fuse would be prudent in the input to the rectifier in case anything fails.

 

[hillbilly1]

A badly distorted waveform might be the cause.
Electronic ballasts contain a capacitor charged by means of a bridge rectifier.
With a sine wave, the peak voltage is about 1.4 times the RMS value, and the capacitor charges up to nearly the peak voltage.
With a 277 volt supply and a sine wave, I would expect the capacitors to charge up to about 380 volts DC, the rest of the circuitry in the ballast being powered from this voltage.

If the voltage waveform is badly distorted, and resembles a sqaure wave, then the peak voltage might be only 1.1 times the RMS figure, in which case the capacitors might only charge to about 300 volts instead of about 380 volts.
That would substantialy reduce the light output.

If desired, the peak voltage may be measured.
Obtain a small bridge rectifier, rated at at least twice line voltage, connect to the output of this rectifier a capacitor also rated at at least twice line voltage.
A resistor of about 1 megohm should be connected accros the capacitor.
The voltage accros the capacitor is easily measured with a DC voltmeter, it should be about 140% of the RMS AC voltage.

Proper care should of course be taken, and a 1 amp fuse would be prudent in the input to the rectifier in case anything fails.

But why would the lights return to normal after a while? If the ballast were causing it, what would make it correct without any intervention?

 

[mivey]

It's been MANY years since I worked for our POCO, but I seriously doubt there to be a frequency problem. The entire USA is tied together. The generators are locked to the line ... there are angles of lag (not power factor concept) between rotating field and stationary coil which relate to excitation. If New York is low, San Francisco is low at the same time.

I would be very surprised to see an error as much as 0.1 Hz for a full second, or 0.01 Hz for a full minute. We've some real utility engineers here; perhaps they will hop in here.

It is not the frequency.

 

[mivey]

Actually the entire US is not tied together. There are 3 grids...east of the Rockies, west of the Rockies and Texas. The only ties between the grids use equipment to match the frequency.

I did not know that. Thanks.

 

[mivey]

A badly distorted waveform might be the cause.

That's what I'm wondering. I also wonder if the meter used was a TRMS meter. With the neighbor having the same issue, it must be an issue on the utility side.

A PQ recording meter is the way to find the answer.

 

[hillbilly1]

That's what I'm wondering. I also wonder if the meter used was a TRMS meter. With the neighbor having the same issue, it must be an issue on the utility side.

A PQ recording meter is the way to find the answer.

I would assume that the POCO's meters were TRMS, there meter also verified that my techs meter was reading correctly. Perhaps there is an industrial customer that was having issues causing the waveform problem, nothing had changed at the big box customer that would have caused the problem to act like it did. I had a customer that I installed a F/A system for, in which the flow switch would activate at midnite every night during the work week. Found out that a local plant would stop using a large amount of water at midnite, causing the cities water pressure to surge, moving the flow switch. turned up the delay slightly, no more prolem.

 

[mivey]

I would assume that the POCO's meters were TRMS, there meter also verified that my techs meter was reading correctly.

Some linemen carry cheap meters. No one has taught them any better.

 

[charlietuna]

I had a problem like this and recorded the service entrance power with a certified Metrosonics Data Logger. Florida Power and Light denied anything and had their men check it. The problem had been on and off for three days.
We called a meeting with them -- they still denied any problem. We gave each a copy of the recorders findings -- after looking at the charts for a few minutes --they asked to be excused for a brief "out in the hall" meeting and they made a few phone calls. Came back in and admited the building was placed on an old abandoned feeder three days earlier. The reason was they were shifting grid areas due to a major feeder blow up. They said the building would be back on it's normal feeder within 24 hours. They are not going to admit anything without proof.

 

[hillbilly1]

I had a problem like this and recorded the service entrance power with a certified Metrosonics Data Logger. Florida Power and Light denied anything and had their men check it. The problem had been on and off for three days.
We called a meeting with them -- they still denied any problem. We gave each a copy of the recorders findings -- after looking at the charts for a few minutes --they asked to be excused for a brief "out in the hall" meeting and they made a few phone calls. Came back in and admited the building was placed on an old abandoned feeder three days earlier. The reason was they were shifting grid areas due to a major feeder blow up. They said the building would be back on it's normal feeder within 24 hours. They are not going to admit anything without proof.

I had a church that was having surges and sags that would put them in the dark during services frequently. (HID lighting, original contractor installed non-time delay emergency lighting) The poco installed a power monitor on their end, we installed one on our end, but while this was being arranged, they were supicously working on the lines near the church and the nearby substation. All of the sudden the church did not have any more problems, and the poco denied doing anything.

 

[mivey]

I had a problem like this and recorded the service entrance power with a certified Metrosonics Data Logger. Florida Power and Light denied anything and had their men check it. The problem had been on and off for three days.
We called a meeting with them -- they still denied any problem. We gave each a copy of the recorders findings -- after looking at the charts for a few minutes --they asked to be excused for a brief "out in the hall" meeting and they made a few phone calls. Came back in and admited the building was placed on an old abandoned feeder three days earlier. The reason was they were shifting grid areas due to a major feeder blow up. They said the building would be back on it's normal feeder within 24 hours. They are not going to admit anything without proof.

But didn't you show a lower voltage with the old feeder?

 

[mivey]

I had a church that was having surges and sags that would put them in the dark during services frequently. (HID lighting, original contractor installed non-time delay emergency lighting) The poco installed a power monitor on their end, we installed one on our end, but while this was being arranged, they were supicously working on the lines near the church and the nearby substation. All of the sudden the church did not have any more problems, and the poco denied doing anything.

I just find it odd they would willfully deny it. I see no liability on their part. Maybe you were not able to get to the person "in-the-know".

I have found that to be true with the phone company. The office claims "no problem". If you can get the right tech, he will find the problem. The denial was just out of ignorance.

 

[hillbilly1]

I just find it odd they would willfully deny it. I see no liability on their part. Maybe you were not able to get to the person "in-the-know".

I have found that to be true with the phone company. The office claims "no problem". If you can get the right tech, he will find the problem. The denial was just out of ignorance.

This was a brand new building of a large church in an affluent area, we met with five representatives (including two engineers) of the poco, after that meeting, was when the poco put it into full gear. I was putting in additional parking lot lighting our CFO donated, and watched them changing lines around. They did have some damage, as they fried two fire alarm panels and the manufacture was no longer going to replace it under warranty.

 

[mivey]

This was a brand new building of a large church in an affluent area, we met with five representatives (including two engineers) of the poco, after that meeting, was when the poco put it into full gear. I was putting in additional parking lot lighting our CFO donated, and watched them changing lines around. They did have some damage, as they fried two fire alarm panels and the manufacture was no longer going to replace it under warranty.

Sounds like a bunch of goof-balls if you ask me.

 

[charlietuna]

The recorder recorded out of spec supply power !

 

[mivey]

The recorder recorded out of spec supply power !

If you have to deal with some goofy folks at the POCO, a PQ recording meter is a good equalizer.