8 common power quality issues

Power quality is a measure of how ‘clean’ the power supplied to an electrical network is. Deal power quality means power supply at a steady voltage where power and voltage supply frequency is as close to the rated supply as possible. The power flow should have a pure, undisturbed sinusoidal waveform and the supply should remain within the specified voltage and frequency limits.

Power quality is especially important for electronic devices and electronically controlled machines. Machines such as computers, air conditioners, and UPS systems are irregular loads. They could be the sources of power quality issues while also being very sensitive to bad power quality.

An unsteady voltage can affect the performance of electronically controlled machines while issues such as harmonic distortion can increase energy consumption and reduce machine lifespan. Poor power quality could thus slow down or hamper production while increasing energy bills. Identifying and eliminating power quality problems at the earliest is key to energy saving.

Consider these 8 common power quality problems to monitor for an efficient electrical network.

Voltage sags

What it is exactly? The normal voltage of the power supply falls, with the fall being anywhere between 19% to 90% of the nominal RMS voltage at the power frequency. This fall occurs for a duration of 0.5 cycles to 1 minute.

Why does it occur? Many times voltage sags can occur due to faults in transmission and distribution networks. However, they can also occur due to faulty installation practices at the consumer’s end. Faulty connections of heavy loads and the starting-up of large motors can lead to voltage sags.

What are its effects? Voltage sags can result in malfunctioning of microprocessor-based control systems such as PLC units and computers. It can also lead the relays to trip, leading the machines to be disconnected from power. Thus, this small fault for a short duration could hamper sensitive machinery and halt production for a certain time.

Voltage spikes 

What it is exactly? A considerable variation in voltage for a short duraction. A voltage spike can last between a few microseconds to a few milliseconds. However, the increase in voltage might be thousands of volts even in low-voltage networks.

Why does it occur? Switching of power lines or power factor correction equipment, disconnecting heavy equipment, lightning strike.

What are its effects? Voltage spikes cause significant electromagnetic interference in sensitive systems. This could in turn cause errors in data processing or even total loss of data. The spikes can completely destroy electronic components of machines and even the insulation of wiring.

Voltage swells

What is it exactly? Increase in voltage for a few movements,  at the power frequency, outside the normal tolerances. It occurs for a duration of more than one cycle and in most cases remains less than a few seconds.

Why does it occur? Fault in transformers, putting heavy loads on or off, poorly dimensioned power sources

What are its effects? A minor voltage swell can cause flickering of lights and screens. However, if the swell is very high, it could lead to data loss in IT and electronic systems

Supply interruptions

What is it exactly? The total absence of electrical supply. This could be for short durations for a few milliseconds or seconds, or long, as in more than 1-2 seconds.

Why does it occur? Insulation failure, insulator flashover or lightning can cause short-term interruptions whereas failure of protection devices or destruction of power lines due to natural calamities can cause long-term interruptions.

What are its effects? Short-term interruptions can cause protection devices to trip, and sensitive electronic devices such as PC and PLCs to abruptly shut down. Long interruptions can lead all equipment to shut down apart from those supported by batteries.

Voltage fluctuations

What is it exactly? The voltage value oscillates with amplitude modulated by a signal with a frequency of 0 to 30 Hz.

Why does it occur? Frequently powering on or off electric motors , operation of oscillating loads.

What are its effects? Flickering of lights and screens, under-voltage

Voltage unbalanced

What is it exactly? Voltage unbalance occurs when the RMS line voltages in a poly-phase system become unequal. The voltages are as closely balanced as possible, and there is always some imbalance, but when it crosses a certain limit, it could cause issues.

Why does it occur? Voltage unbalance occurs largely because of improper distribution of single-phase loads on a three-phase system. Large single-phase loads can also be a part of the problem.

What are its effects? Voltage unbalance is especially damaging for three-phase loads.

Harmonics

What is it exactly? Harmonics are voltages or currents that have frequencies that are  integer multiples of the fundamental power frequency. If the fundamental power frequency is 60 Hz, the second harmonic will be 120 Hz, third harmonic will be 180 Hz and so on.

Why does it occur? Harmonics arise when certain non-linear loads convert AC voltages into DC. Harmonics cause voltage or current waveforms to take on a non-sinusoidal form.

What are its effects? Harmonics cause neutral overload in 3-phase systems. Harmonics can lead to overheating of cables as well as equipment. They lead to electromagnetic interference in electronic and communication systems, nuisance tripping of thermal protections and even result in errors within the average power meters.

Noise

What is it exactly? High-frequency signals are superimposed on the power system frequency waveform.

Why does it occur? Noise occurs when radio waves emanate from devices such as TV, and other electronic equipment or radiations from welding machines and arc furnaces. Noise can also result from something as simple as improper grounding.

What are its effects? Noise disrupts sensitive electronic equipment including computer systems among others. It can cause disturbance in displays, data loss, inaccurate data readings, failure or reset of the equipment

A small step can earn big results to resolve these problems.

Power quality problems cause serious damage to sensitive electronic devices. The resulting loss of data and equipment failure can bring significant financial losses and downtime. Continuous and close monitoring of power quality is a simple step that could help quickly detect and resolve power quality issues.

A multifunction meter is capable of monitoring a number of power quality parameters. This includes the quality of current, voltage, power factor, as well as harmonics among others. Changes in key parameters of critical loads can be monitored and recorded quickly and effortlessly. These can then be transferred to a computer system to be analyzed by software to arrive at corrective action.

Explore the details of how a multifunction meter can help in power quality monitoring

Newtek Electricals has been designing, manufacturing and supplying multifunction meters to manufacturing facilities around India and abroad for over a decade. Innovations in manufacturing techniques have allowed Newtek to manufacture reliable and durable multifunction meters in a short time, thus significantly reducing the lead time for our customers.

Explore the product in detail here.