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Introduction to Power Quality

In recent years, we have become increasingly dependent on electricity. Along with this, there has been an increasing emphasis and concern for the quality of power delivered to factories, commercial establishments, and residences.

Power quality is generally described as the power grid’s ability as an available power supply to deliver a safe and reliable power flow. The power flow should consist of a pure sinusoidal waveform that stays within the required voltage and frequency limit. 

Due to rising nonlinear and other loads affecting the grid, deviations to the ideal conditions are frequent in today’s electrical networks. With new players and technologies joining the industry, which used to be a fairly stable operating environment, power generation is becoming more challenging. All of these bring new issues to power grid operators.

The effects of inadequate power quality can lead to significant losses for business and the economy. In the worst-case scenario, in critical operations and highly sensitive settings, such as hospitals, it could pose a danger to human life.

What is Power Quality?

Power quality is generally defined as the analysis of electronic power and grounding systems to maintain the quality of the power supplied to the system. This is the analysis of electronic power and grounding equipment that is acceptable for the operation of that equipment and compatible with the wiring system of the premises and other connected equipment.

However, good power quality is difficult to describe since what is good power quality might not be good enough for today’s personal computers and other sensitive loads for a refrigerator motor.

Indications of Poor Power Quality

Poor power quality threatens the efficiency, continuity and safety of electrical installations. It increases the risk of malfunction and damage associated with higher maintenance costs and unnecessary energy losses. 

Poor quality of electricity can be experienced in the form of flashing lights or humming noises from the plant, but may also go unnoticed and eventually have costly consequences. Poor Power quality may lead to the shutdown of production, self-igniting cables and premature aging of the plant and electrical equipment.

Power Dips

The power dip is a brief decrease of 10 to 90 percent of the nominal line voltage in the Root Mean Square (RMS) line-voltage. A dip has a length of 0.5 cycles to 1 minute. The start of big induction motors and utility faults are common causes of sags.

Power Swell

This is a brief increase in the RMS line-voltage of 110 to 180 percent of the nominal line-voltage for a duration of 0.5 cycles to 1 minute. Sources of voltage swells are line faults and incorrect tap settings in tap changers in substations. 

Impulsive Transient

A brief nonlinear change in voltage, current, or both on a power line is an impulsive transient. Transients can also originate in lightning strikes, switching of inductive loads, or switching in the power delivery system. If the disruption level is high, these transients may lead to equipment shutdown or damage. 

Oscillatory Transient 

A brief, bidirectional change in voltage, current, or both on a power line is an oscillatory transient. This may occur due to the changing of transformer ferroresonance or power factor correction capacitors.

Power Interruption

Power interruption is characterized as a reduction to less than 10 percent of the nominal line-voltage or current, not exceeding 60 seconds in duration. Another common event of power-quality is “notching,” which can be generated by finite line inductance rectifiers.

Voltage fluctuations

There are relatively minor differences (less than 5%) in the line-voltage of RMS. Cycloconverters, arc furnaces, and other devices that draw current, not synchronized with the line frequency, may cause these variations. Due to an effect known as “flicker” that is noticeable to the end-user, such fluctuations can result in variations in the lighting intensity.


Power quality has a strategic importance to continuity, reliability and energy efficiency. Today, electrical networks are affected by various factors which leads to damage in sensitive equipment, and a halt in the industry works. As a result, many businesses are facing financial loss because of power quality problems. 

Sydney Eastern Suburb Electrician is here to ensure that your premises are receiving good power quality. With our high quality and affordable service, our level 2 electricians are here to help you with installation, repair and electrical inspection.

Call us at (02) 8378 2827 to get a free quote today or book online.

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