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Low Voltage Concern
Mark Hannah:
I found a few posts about low voltage but they do not completely cover the information I'm looking for. Posts such as opinions on what is too low and too high and what the utility company is legally obligated to provide at the closest and furthest point.
This is almost more of a request on how to go about addressing the issue. I have been voicing the concern with the "venue" for a few years so... Your responses will help me decide if the chain of emails I already have is good enough to cover me if we were to have show stoppage.
I'm uncertain how much detail to provide so I'll start out with a few bullets and answer any of your questions.
* Without a load, the voltage is between 112 to 114 (G-H and N-H) and 198 (H-H).
* With a load, I have seen the voltage drop to 100-104.
* Incoming power from provider is 460v measured by facilities' electrical contractor.
* Amp meter on distro isn't very accurate (doesn't show anything below 5A). Educated guess = constant 30-35A when using lights. Audio is probably 5-10 of that.
* 100amp service. Panel not labelled so I don't know what else might be on it.
* UPSes will drop to battery. Typically for only short durations
* Self powered mains/monitors (Meyer). No complete loss of audio.
* Keyboard with less forgiving PSU has shutdown once in the past.
* Reference PDF (link below) for RMS Voltage and Current from utility provider.
Thank you in advance.
https://drive.google.com/file/d/1TKRe0qEkQmk6nYvn4iJ9b5pn4xEP9ZGL/view?usp=sharing
TJ (Tom) Cornish:
--- Quote from: Mark Hannah on June 04, 2018, 08:58:56 AM ---I found a few posts about low voltage but they do not completely cover the information I'm looking for. Posts such as opinions on what is too low and too high and what the utility company is legally obligated to provide at the closest and furthest point.
This is almost more of a request on how to go about addressing the issue. I have been voicing the concern with the "venue" for a few years so... Your responses will help me decide if the chain of emails I already have is good enough to cover me if we were to have show stoppage.
I'm uncertain how much detail to provide so I'll start out with a few bullets and answer any of your questions.
* Without a load, the voltage is between 112 to 114 (G-H and N-H) and 198 (H-H).
* With a load, I have seen the voltage drop to 100-104.
* Incoming power from provider is 460v measured by facilities' electrical contractor.
* Amp meter on distro isn't very accurate (doesn't show anything below 5A). Educated guess = constant 30-35A when using lights. Audio is probably 5-10 of that.
* 100amp service. Panel not labelled so I don't know what else might be on it.
* UPSes will drop to battery. Typically for only short durations
* Self powered mains/monitors (Meyer). No complete loss of audio.
* Keyboard with less forgiving PSU has shutdown once in the past.
* Reference PDF (link below) for RMS Voltage and Current from utility provider.
Thank you in advance.
https://drive.google.com/file/d/1TKRe0qEkQmk6nYvn4iJ9b5pn4xEP9ZGL/view?usp=sharing
--- End quote ---
Voltage dropping below 105-108v is too low. 110+ is better.
Practically speaking, the shortest path is probably bringing a boost transformer and billing your client for it. You can let them know that this is necessary because the venue power is inadequate, and their choice is to fix the power issue - whether it's theirs or the POCO's - or continue paying you to work around the low voltage. Your datalogger chart should be very helpful in making your case to venue management.
Stephen Swaffer:
There are 2 separate issues here-and 2 separate correct solutions-though TJ's solution might be the only one you can use.
First-and potentially the easiest to fix is the low voltage. Line to neutral voltage on 460 volts (as opposed to 480-though often used interchangeably) is 265 v nominal. In that case your readings, as recorded, look fine. However, there will be a customer owned transformer somewhere on premises-probably close to the 120/208 panel. If that is a 480 to 208/120 transformer, that would explain the low voltage. There are most likely taps on that transformer that are intended to adjust the voltage. They should have been adjusted by the installer to provide 120 volts nominal at the 120 volt panel-though it is conceivable (but not at all likely) that they are set where they are on purpose. It should take a good commercial or industrial electrician less than an hour to correct this and get the voltage where it should be.
The second issue is the voltage drop from loaded to unloaded. If this is consistent across all three phases, then it indicates something is undersized-maybe the transformer, more likely wire somewhere in the circuit. The wire is probably large enough "by the tables" ampacity wise-but the designer (be they electrician or engineer) did not allow for voltage drop over the length of the wire. This is obviously much more difficult and expensive to correct. The "hack" work around in this case would be to set the taps on the transformer a little high-maybe 122-123 volts-so that the voltage still stays high enough to avoid drop out under load.
Mark Hannah:
Tom & Stephen,
Thank you for your responses.
Tom,
The datalogger is actually from the Utility company sent to me via the venue.
I work for the federal govt. It is their gear and the venue is free. The federal govt would most likely need to cover the cost of renting or purchasing a transformer.
Stephen,
I did suggest the facility re-tap the transformer. Your verbiage is much better than mine so I hope you do not mind if I cut and paste some of it.
I thought I might add the utility company's response that came along with the log.
Regards,
Mark
--- Quote ---Good Afternoon. Per our discussion, the standard voltage class that we provide at the level specified below is 265/460V. We are allowed nominal voltage ranges between 238/414V and 278/483V by COMAR. However, we make sure to maintain voltages close to the voltage class that we commit to our customers.
I reviewed the readings taken from the facility and don't see any issues related to abnormal voltage drops. Please see attached file. In this case, Pepco typically refers it back to the customer to make amends on their end.
High temperatures typically lead to higher use of air conditioning which can increase the demand on the system. This may affect the voltage level. However, this is included during our planning process, and we compensate to ensure that our voltage levels are still maintained through high stress situations.
--- End quote ---
TJ (Tom) Cornish:
--- Quote from: Mark Hannah on June 04, 2018, 12:55:11 PM ---Tom & Stephen,
Thank you for your responses.
Tom,
The datalogger is actually from the Utility company sent to me via the venue.
I work for the federal govt. It is their gear and the venue is free. The federal govt would most likely need to cover the cost of renting or purchasing a transformer.
Stephen,
I did suggest the facility re-tap the transformer. Your verbiage is much better than mine so I hope you do not mind if I cut and paste some of it.
I thought I might add the utility company's response that came along with the log.
Regards,
Mark
--- End quote ---
This suggests distribution difficulties in the venue as Steve called out if the voltage is considered acceptable at the service entrance. Sounds like you're on the right track working with the venue.
The POCO's minimum of 238/414 corresponds to about 104v after step-down, so while the measured is a lot better than that, it sounds like if the POCO wanted to be difficult, they have a lot of latitude in their policies to point to to avoid fixing the problem if it ever did measure that low.
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