Tips
Have circuit breakers and fuses in your facility ruptured or blown up instead of tripping?
These devices can fail to interrupt due to poor maintenance or because the available short circuit current is too high.
Suggested Studies and Services:
Short Circuit Study
Protective Device Coordination Study (Device Settings)
Have circuit breakers and relays in your facility experienced so-called "Mystery Trips"?
Many circuit breakers trip due to lack of maintenance, incorrect device settings, improper grounding, or harmonic currents.
Suggested Studies and Services:
Load analysis
Protective Device Coordination Study (Device Settings)
Power Quality Investigation
When an automatic transfer switch operates, does it sometimes trip out the circuit breaker feeding it?
This can be caused by the motor loads downstream being out of phase with the new source. Incorrect protective device settings can also cause this problem.
Suggested Studies and Services:
Protective Device Coordination Study (Device Settings)
Load Analysis
Does your utility bill contain a sizeable power factor penalty charge or kVA demand charge?
This is caused by the distribution system operating at a poor power factor (i.e., < 0.95-0.98). Adding capacitors or synchronous motors can raise the power factor to avoid the penalty.
Suggested Studies and Services:
Load Flow Analysis
Power Factor Correction Study
Does your facility experience low voltage during peak load periods?
This can be caused by the distribution system operating at a poor power factor, by transformer taps set incorrectly, or by the utility. Also the meter could be defective.
Suggested Studies and Services:
Load Flow Analysis
Power Factor Correction Study
Does your emergency or co-generation generator experience poor regulation?
This can be caused by the distribution system operating at a poor power factor, by harmonics, by a poor generator control system, or by too small of a generator/prime mover.
Suggested Studies and Services:
Load Flow Analysis
Power Factor Correction Study
Power Quality Investigation
Is your telephone system noisy or is there interference with the power line carrier systems?
This can be caused by harmonics generated in the distribution system. The harmonics cause electromagnetic coupling between the electronic power and communication circuits.
Suggested Studies and Services:
Power Quality Investigation
Harmonic Analysis
Power Factor Correction Study / Filter Study
Has more than one breaker opened due to a short circuit?
Many circuit breakers trip due to poor maintenance or incorrect device settings.
Suggested Studies and Services:
Power Quality Investigation
Harmonic Analysis
Power Factor Correction Study / Filter Study
Has your facility main breaker tripped due to a ground fault instead of the downstream 20 ampere circuit breaker?
The device ground fault setting may be set incorrectly. Ground fault devices are very sensitive. They can trip for very low values of current. Ground loops can cause false ground fault sensing. Several additional layers of ground fault protection may also be needed.
Suggested Studies and Services:
Power Quality Investigation
Protective Device Coordination Study (Device Settings)
Do you have capacitors that fail and capacitor fuses that blow?
This is a typical sign of a harmonic resonance condition. The capacitor sizes must be changed or a filter must be installed.
Suggested Studies and Services:
Power Quality Investigation
Harmonic Source & Filter Study
Load Analysis
Short Circuit Study
Do you have 15kV cable shields that burn up and fail?
This could be caused by ground circulating currents.
Suggested Studies and Services:
Grounding Study
Load Flow Analysis
Have you ever had a catastrophic equipment failure?
Suggested Studies and Services:
Protective Device Coordination Study (Device Settings)
Load Flow Analysis
Short Circuit Study
Harmonic Source & Filter Study
Power Quality Investigation
Has your electrical system undergone multiple plant expansions since the original installation?
This usually results in loss of protective device coordination. Increased available short circuit current can cause the older equipment to be underrated for the available short circuit current.
Suggested Studies and Services:
Protective Device Coordination Study
Load Flow Analysis
Short Circuit Study
Do you have overheated or noisy transformers even though they are not carrying full load?
This is usually due to harmonics circulating in the primary delta winding, which can generate heat.
Suggested Studies and Services:
Power Quality Investigation
Load Flow Analysis
Harmonic Source & Filter Study
Do you have motors that overheat at no load or below rated load?
This can be caused by a voltage imbalance or a distorted voltage waveform. The distorted voltage waveform is usually caused by harmonic sources.
Suggested Studies and Services:
Power Quality Investigation
Load Flow Analysis
Harmonic Source & Filter Study
Does your electronic equipment frequently mis-operate?
This can be caused by a distorted voltage waveform. The distorted voltage waveform is usually caused by harmonic sources. Some types of electronic equipment look for a zero crossing of the sine wave. A distorted wave can contain many zero crossings.
Suggested Studies and Services:
Power Quality Investigation
Load Flow Analysis
Harmonic Source & Filter Study
Do you have motors fed by VSDs that trip off line or fail more often than usual?
This can be due to a destructive reflected voltage wave on the cable feeding the motor. This reflected voltage wave stresses the motor insulation and causes premature winding failures. This can also be caused by utility capacitor switching.
Suggested Studies and Services:
Power Quality Investigation
Do you have motors fed by VSDs that have bearing failures more often than usual?
This can result from harmonic currents being induced in the motor rotor and the motor frame.
Suggested Studies and Services:
Power Quality Investigation
Motor Study
Harmonic Source & Filter Study
Do you have computers and other electronic equipment fail or mis-operate more often than usual?
This can be due to "dirty" power with a high voltage distortion being supplied to the equipment. Poor grounding practices can also cause this problem.
Suggested Studies and Services:
Power Quality Investigation
Harmonic Source & Filter Study
Do you have boiler controls that frequently mis-operate or fail?
Some modern boiler controls monitor the phase and current unbalance and will trip the boiler off line.
Suggested Studies and Services:
Power Quality Investigation
Load Flow Study
Do you have frequent service calls on electrical equipment and are you told "No problem found" or "It's due to dirty power"?
Many of these unexplained problems can be traced to poor facility power quality or grounding practices.
Suggested Studies and Services:
Power Quality Investigation
Has the utility recently increased the size of your main service transformer?
Some of your equipment may be underrated due to the increased short circuit current. The devices may suffer extreme damage for faults on the distribution system.
Suggested Studies and Services:
Short Circuit Study
Did you have a lighting retrofit done at your facility and are now experiencing (a) Mis-operation or high failure rate of sensitive electronic equipment and/or (b) High failure rate of electronic ballast and lamps?
Some new electronic ballast can create high harmonics and generate high frequency noise, which can affect the operation of electrical equipment.
Suggested Studies and Services:
Power Quality Investigation
Do you have overheated or discolored neutral conductors feeding electronic equipment?
This is usually due to triplen (3rd, 9th,...) harmonics that do not cancel in the neutral.
Suggested Studies and Services:
Power Quality Investigation
Load Flow Analysis
Harmonic Source & Filter Study
Do you have main breakers that trip off line or lose utility power when elevator or UPS tests are conducted late at night or during periods of light load?
This is sometimes caused by reverse tripping of the utility network protector relays.
Suggested Studies and Services:
Power Quality Investigation
Load Flow Analysis
Protective Device Coordination Study
Does your electronic equipment experience operational problems when only fed by an emergency generator?
This can be caused by the harmonic-generating loads and the higher generator impedance that distorts the voltage waveform and raises the voltage THD%.
Suggested Studies and Services:
Power Quality Investigation
Load Flow Analysis
Harmonic Source & Filter Study
Do your generators or co-gen facility become uncontrollable and unstable when internal or utility faults occur?
This can be due to improperly adjusted voltage regulators, governors, or incorrectly set protective devices.
Suggested Studies and Services:
Transient Stability Study
Load Flow Analysis
Protective Device Coordination Study
Do you have motors that trip off line unexpectedly?
This can result from overload or inrush. The tripping device could be defective, set incorrectly, or the motor could be defective.
Suggested Studies and Services:
Motor Starting Study
Load Flow Analysis
Protective Device Coordination Study
Do your switchgear or switchboard meters display incorrect readings?
This could be due to harmonic voltages and currents and the use of non-true RMS meters.
Suggested Studies and Services:
Power Quality Investigation
Load Flow Study
Do you experience blinking of incandescent lights (flicker)?
This is usually caused by a large motor or group of motors starting.
Suggested Studies and Services:
Power Quality Investigation
Motor Starting Study
Load Flow Study
Do you have problems with corroded pipes or conduits? Do you experience pin hole leaks in boilers or sterilizers?
Many of these problems can be traced to incorrect grounding practices on separately derived systems.
Suggested Studies and Services:
Power Quality Investigation
Do your computer monitors have flicker or wavy screens?
Many of these problems are caused by electromagnetic fields that can be created by transformers, power lines, MRIs, and other electromagnetic devices.
Suggested Studies and Services:
Power Quality Investigation