Troubleshooting Facility Power Problems
For outages, repair or any power problems, contact your PGE representative or call the Business Services Team:
Portland: 503-228-6322
Salem: 503-399-7717
Elsewhere: 800-822-1077
Frequently asked questions
With lighting, HVAC systems, computers, refrigeration, machinery and motors all putting demands on your facility’s electrical system, it can be a challenge to maintain a reliable flow of power for smooth operations.
Sometimes, power problems happen externally, like when a storm knocks a tree onto a power line. But in many cases, the answer lies inside your facility. Your wiring and equipment, and how they interact, all play a role.
One of the 200-amp circuit breakers that serve a compressor has tripped several times. An electrician was unable to find any overload problems with the circuit breaker and thought it was probably due to harmonics. What can be done to fix the problem?
Harmonics is a complex subject and when it causes circuit breakers to keep tripping, it’s a nuisance. Harmonic currents are caused by certain types of equipment that draw current intermittently while running.
Harmonic currents flow from the load, through the circuit breaker, and into PGE’s system. If the circuit breaker is tripping because of harmonics, it may be defective, or you may require a different type of breaker that is not sensitive to harmonics.
Harmonics are sometimes blamed when a circuit breaker that is protecting a compressor trips. However, if a compressor is pulling more than 80 percent of its nameplate capacity for an extended period of time, it will, in fact, overload the breaker and trip. So a 200- amp circuit breaker should not have more than 160 amps per phase for any extended period of time.
We have a small standby generator that supports our critical systems when we have a power outage. We also have small UPS to support the loads until the generator starts. However, the UPS does not work correctly when the generator operates. Why not?
Not all UPS systems operate correctly when served by a generator. You can adjust the sensitivity of some UPS units so they work correctly with a small generator. Or it may be necessary to install better controls on the generator before the two can work together. Some generators do not have quality voltage and frequency regulation, while others cause too much voltage distortion. Each of these problems can cause some UPS systems to cycle their battery until it is depleted. Be sure to carefully review the specifications of any UPS you want to operate with a generator to ensure they will work together.
We recently lost some control cards in one of our machines that has surge protection. The repair technician told us the failure was due to surge damage. How can this be true?
Losing some control cards due to surge damage may indicate inadequate surge protection or improper installation. Another common cause of failure for control cards is inadequate or incorrect grounding of the control card system. Wiring errors can lead to failures even if you have surge protection. Contact your PGE representative or PGE Business Services (numbers on front).
One of our large three-phase motors keeps tripping. An electrician told us the motor is not drawing the same amount of current on each phase and something must be wrong with the service from PGE. What can be done?
The PGE specification for voltage imbalance measured at your main service is 3 percent or less. Generally, we are below 2 percent. If the voltage is imbalanced it causes current imbalance in three-phase loads. And if there isn’t an equal load on each phase, the voltage imbalance can increase at different locations within your facility. If you think the voltage imbalance is higher than it should be, contact your PGE representative or PGE Business Services.
We have several variable frequency drives that frequently trip during the week. This usually occurs between 5 a.m. and 6 a.m. Do you know why this is occurring and what we can do to prevent it?
If a VFD trips early in the morning, it may be that it is sensitive to capacitor switching transients. PGE turns the capacitor banks on and off at the substations to support our customer load requirements. Some brands of drives (15 HP and smaller) are sensitive to this one cycle disturbance; newer, larger drives are not as susceptible. The most cost-effective way to reduce this type of nuisance tripping is to install line reactors; contact your PGE representative or PGE Business Services for more information.
Every time a fault occurs our variable frequency drives trip off line. What can be done to prevent this?
Most faults are single-phase events, and most VFDs can handle single- phase sags even when the voltage drops to almost zero.
Unfortunately, the drive’s control circuit may not be able to handle such an event; a minor voltage sag on the control circuit can cause shutdown. There are many ways to solve this problem, but the two most cost-effective solutions are: support the control circuit with an uninterruptible power supply, and replace “weak link” control components with components that are less sensitive to sags. This may involve replacing only a few “ice cube” relays.
To find out more, contact your PGE representative or PGE Business Services.
We added variable frequency drives to some of our motors. Now they seem to be failing much sooner than expected. Can you explain this?
Adding VFDs to your existing motors is a good way to reduce your energy usage and have better control of your motors. However, it can lead to early failure of motors that are not designed to operate from a VFD. An inverter-rated motor is one that is designed to operate correctly with a VFD. Motors that aren’t can still be used with a drive, but additional mitigation steps are necessary to prevent early failure of the motor.
To find out more, contact your PGE representative or PGE Business Services.
Surge Protection
Understand power surges and surge protection options to help prevent equipment damage.
Backup generators
Generators can be a convenient backup during a power outage when used correctly. Review safety tips to protect yourself and our crews.