Power Quality and Symptoms 101

Most amateurs would have trouble recognizing power quality problems from electrical distribution systems or equipment connected to circuits. More often than not, these problems would be viewed as just faulty old equipment that needs replacing or a one-time inconvenient reset.

To get to the root of the problem, you might look at types of loads on the system and monitor for harmonics, unbalance or disturbance patters.

There are two types that can determine the area where the common problems in power quality occur: Harmonic Distortion Issues and Voltage and Current Anomalies. For the latter, problems may still be correct before the equipment is damaged.

Here’s a quick rundown on power quality symptoms and causes:

Dips or Sags

Voltage dips or sags are a reduction of voltage of 10% or more below the normal or recommended usage. They have a ripple effect across equipment and can be caused by starting large loads, having similar operations in neighboring facilities, or severe weather.

You might experience dimming of lights, computer lockups, relay and contactor chatter, or complete dropout. Your equipment and system may also shutdown or produce random deceptive alarms.

Swells

Voltage swells are the complete opposite of dips. They are surges in voltage of 10% or more above normal or recommended usage. Overvoltage is a swell that lasts longer than a minute.

If you’re getting failed power supplies and overvoltage shutdowns and alarms on variable frequency drives (VFDs), you might be experiencing this issue. Potential causes include fault on a single phase of a three-phase system, sudden load decrease, or capacitor bank switching.

Transients

Transients, also known as Voltage Spikes, are dangerous for people working with electrical systems. They are short bursts of energy that are typically caused by switching of capacitors. They can also be created by lightning strikes, reenergizing systems after a power failure, sudden stoppage of large equipment, or dirty or worn contactors.

Some symptoms you might experience include flashover and arcing effects in distribution equipment, damaged insulation, failed electronics and computers lockups.

Interruptions

Interruptions are mostly caused by momentary loss of utility power. Symptoms include equipment shutdowns.

Unbalance

In a balanced three-phase system, the phase voltages should be equal or close to equal. If the measurements of the phase voltages are far and wide, they are considered unbalanced.

If you’re experiencing overheated three-phase motors and transformers, you might have an unbalance issue. This is due to unbalanced loads across individual phases of three-phase panel boards, unbalanced utility supply, operation of single-phase welders, or open-delta transformers.

Harmonics

Harmonics are currents or voltages with frequencies that are integer multiples of the fundamental power frequency. While any electronic load can generate harmonics, you may experience inefficiencies, which can be an issue.

Some symptoms of this issue include overheated neutral conductors, transformers, and inductive motors. The electronic equipment may also produce artificial and unexplained alarms, and shutdowns.

A potential cause for this issue is non-linear loads such as switching power suppliers, converter sections of uninterruptible power supply (UPS), VFDs, and battery chargers. Welders and arc furnaces are also identified as possible sources.

Identifying power quality issues can help protect your equipment from damage. Invest in high-quality test and calibration tools, and be confident with your measurement results. Presidium is the official distributor of Fluke Industrial Group and Fluke Calibration products in the Philippines. For inquiries, call +632 464 9339 or email us at info@presidium.ph.