Sustained Over Voltage Long term effect 2

[NYedison]

Guys, Did anybody come across any study on the effect of Sustained over voltage in a 3 phase 4 wire 60 Hz electrical system?

The actual voltage of the system, when measured, was found to be above 500/290 volts. The nominal rating is 480/277 volts 60 Hz.
What long term (3 months, 1 year) effects the overvoltage will have on the Cables/wires, Ballasts and MVLamps or Metal Halide Lamps and Incadescent lamps.

 

[alehman]

500 volts is within the normal operating range of a 480 volt system and should not be a problem for most electrical equipment. Where in your system are you measuring the voltage? Voltage drop in your wiring will make the votlage at the fixtures lower than at the service entrance. Have you asked your utility company if they are able and willing to reduce your voltage?

Possible effects:
cables/wires: none
ballasts and MVLamps: will run hotter and may reduce lamp life
Metal halide lamps: higher output and shorter life
incandescent lamps: higher output and shorter life

 

[NYedison]

alehman
Thank you for your quick and valuable response. The volatge is measured at supply end.

Utility supply volatge is also more than 10%. Normal 4160Volts, measured 4300 volts.

You are right about cables because cable are rated for 600 volts.

marvin

 

[mc5w]

The East Palestine City Schools have this problem and it is blowing up electronic fluorescent ballasts among other things. Unfortunately, General Electric read cheap Chinese ballasts cannot handle exposure to 305 volts as advertised. See a report badnewsballasts.txt over at http:// home dot earthlink dot net /~mc5w for more details. I asked General Electric for inrush current data and I got a big, "We don't know," from them. I did an autopsy on a dead ballast from this school ( took several overnight soaks in 5 gallons of diesel fuel ) and found several design flaws.

If you have Kollmorgen 460 volt servo drives exposure to 500 volts **WILL** blow them up! Somehow, their engineers are firmly convinced that power plant voltage in th U.S. is only 460 volts +-20 volts.

You really only have to worry about electronic equipment and any HVAC stuff that runs overnight when the voltage is naturally high.

 

[alehman]

4300 is 3.4% above 4160. In the US, ANSI C84.1 requires the utility voltage to be within +-5% of nominal. In Europe, the tolerance is +-10%.

Can you adjust the taps on your transformer?

 

[NYedison]

Alehman
I agree that the 4300 voltage is within 5% . Actually the voltage is 4400 which is above 5 %. First I would like to have the meter calibration cheked and the data electronically recorded for over 3-4 days.
Before approaching utility I want to find out if other users had any problem with sustained high voltages or any study about this problem.
Transformer Tap change is the solution I am going consider if the over voltage continues longer than 4-5 days.

 

[NYedison]

mc5W
Thank you for the relevant information. I will visit the link and read the details. I really have to worry about electronic ballasts and other elctronic devices.
marvin

 

[stevenal]

Motors like high voltage. They tend to draw less current and run more efficiently and cooler at the higher voltage. In your zeal to correct what sounds like a non-problem, make sure you are not creating a low voltage problem when loads are high.

 

[dpc]

I've been in a lot of facilties where panic sets in when the 480 V system bus voltages hit the magic 500 V figure. I've had little success convincing them that it is not a problem.

On the other hand, when we note MCC bus voltages of 440 V, they don't see much problem with that because "it's always been like that". But in reality, the motors would be happier at 500V than at 440V.

110% of 480V is 528 V.

110% of 460V (motor nameplate) is 506 V.

As mentioned above, if you want voltage to be in nominal range at full load, you have to accept some increase in voltage at no-load or low load.

 

[mc5w]

However, high voltage increases the portion of motor magnetizing current that produces countervoltage, so I would be concerned about sustained high voltage for motors that have either very light load or very heavy load.

As I stated before, high voltage is more of a concern with electronic devices such as CNC, servos, and ballasts.

 

[NYedison]

Stevenal
Thanks. I agree with you. About motors. Motors have good insulation. Also are characterized by Inertia and also there is back emf to match the supply voltage. The speed is not going to be affected by higher voltage.
The devices I am worried about are solid state, electronic devices and lamps that are affected by higher voltages.

Here the voltage of 500 volts is not matter of concern. The voltage goes 510 & 520 volts for a good amount of Time. That may not be good for other devices.
Marvin

 

[NYedison]

dpc
Thanks for your reply. 500 volts at no load or light load is expected.

What about 510-520 volts at light load for other devices for 2-3 hours everyday?
Marvin

 

[NYedison]

mc5w

You are right Ballasts, UPS , incandescent lamps need to be addressed when overvoltage continues for appreciable time.
Not motors.
Marvin

 

[mc5w]

You also need to worry about power factor correction capacitors when the plant is at light load because these can boost the voltage during breaks and so forth. If your PFC is on timer control and people shut off the motors during lunch you could cook something. I would not apply a PFC unless it is switched by the same control circuit as the motor whose magnetizing current is absorbs OR an overvoltage relay is there to cut off a big central unit.

A lot of electrical utility primary line capacitors are either on line all the time or use timer control. This could be a bit of a problem at lunchtime of if the timers are off time due to a power failure.