The Impact Electrical Interference Has On Efficiency & Wasted Power

Businesses are constantly under pressure to be energy efficient and ensure they do not waste electricity. However, while most of us know that this means more than simply turning off devices and equipment when not in use, many are not aware of the impact electrical interference has on efficiency and wasted power. Here, Steve Hughes, managing director of power quality specialist REO UK, explains how businesses can stay safe from interference.

Power quality is a term that many people use but few fully understand. Typically associated with a stable supply of mains electricity, power quality covers a range of problems, including the continuity of the supply of electricity, fluctuations and spikes in voltage and current, as well as transients or harmonic currents.

We are often warned of the dangers of electrical interference. As an increasing number of businesses become reliant on a constant power supply, it is becoming more important that power is stable and reliable.

However, electrical interference itself is a blanket term that refers to any power quality problem that negatively impacts and disrupts a power supply. In order for businesses to protect their systems adequately, they must first identify and understand the specific risks they face.

Voltage spikes and fluctuations

Every electrical engineer knows that voltage spikes are an often unpredictable and unavoidable nuisance. Spikes occur when there is a sudden, unexpected and substantial transient voltage that lasts for less than two nanoseconds.

If lightning were to strike a power line or a data centre, for example, this would result in a high-voltage spike that interferes with power flow and can damage components.

However, spikes should not be confused with current fluctuations. While spikes are brief leaps of voltage, fluctuations in power supplies include both surges and dips that last longer than three nanoseconds.

Typically, these are deviations from the normal voltage range that are significantly smaller than spikes, often around five per cent higher or lower, but the impact they have is equally important to address.

The main impact of current fluctuations is that they adversely effect the performance of equipment connected to the power supply. While most devices are designed to maintain operation within a specific range of nominal voltage, there are many industrial applications where this is not the case.

In security systems, for example, it is vital that the power supply is stable and reliable. If there were voltage surges or dips in a security systems’ power supply, there is a risk that the system would malfunction, even if only temporarily. Likewise, unstable voltages in medical environments lead to the risk of critical equipment failure.

In order to keep sensitive equipment fully functional and safe from current fluctuations, it is important that businesses use power filters in their systems.

Filters provide an easy way of eliminating the harmful currents in order to regulate power supplies and prevent performance failures. Depending on the power filter used, it can also provide protection against other disruptive problems such as harmonic currents.

Harmonic currents

For years, power quality was a problem almost exclusively reserved for industrial applications. When manufacturers began using non-linear, switched, devices like variable speed drives (VSDs) to control the speed of a motor driving a conveyor belt, they had to pay attention to the effect these devices have on the mains supply.

Harmonic currents are an example of the effect these devices can have. Harmonic currents are significantly more troublesome for electrical engineers than fluctuations.

They regularly occur when non-linear loads — such as a variable speed drive (VSD) used to control the speed of a motor — induce a non-sinusoidal current on the supplied load. This results in a higher amplitude current, which increases energy consumption and accelerates the rate of component degradation.

While harmonics have long been an issue across the electrical industry, it is becoming increasingly important that electrical engineers use technology to limit the impact of harmonics. Widespread use of electronics, as well as a trend towards renewable energies, has meant that we have seen a higher number of non-linear loads in recent years.

Harmonics are caused by non-linear electrical loads such as many switch-mode power supplies (SMPS) that are commonly used in power electronics including computers and chargers. An SMPS allows the device to be more lightweight and compact. Unfortunately, the process of high frequency switching causes harmonics.

In small doses, harmonics do not cause too much damage to systems. However, in large quantities, such as in data centres where many PCs are used simultaneously, harmonics cause distortion that can wreak havoc on electrical systems.

In a best-case scenario, businesses will find that their energy costs will go up. The worst case is that key components in electrical systems, including the insulation of power transformers, can overheat and degrade quicker.

In HVAC applications, for example, poor power quality can damage HVAC components including heat exchangers, fans, pump motors, condensers and furnaces, reducing their lifespan and raising energy costs.

Combined with the fact that most buildings, offices and residential and commercial facilities have some form of heating, ventilation and air conditioning (HVAC) it is easy to see the scale of the problem of harmonic currents.

Likewise, parallel inverters that connect power lines from renewable energy sources to the main electrical grid are prone to harmonic resonance. While harmonics in plant environments can have adverse effects, the disruption to the power grid is more substantial and can result in anything from minor instability to blackouts.

[Fortunately, engineers can address harmonics in a number of ways. The most cost- efficient of these is by using a passive filter to mitigate harmonics in a system to an acceptable level of total harmonic distortion (THD), typically under five per cent. This can lead to significantly reduced operating costs depending on the amount of harmonic currents in a power network.

In fact, REO UK recently set up an online energy saving calculator to help facilities managers and plant engineers identify the cost and energy savings of integrating a passive filter into their systems. This is a step forward in helping businesses realise the hidden costs of harmonic currents.

Electromagnetic Interference (EMI)

Most electrical engineers are at least acutely aware that their systems should comply with electromagnetic compatibility (EMC) directives, such as 2004/108/EC in the EU. The reason for this is that electromagnetic interference (EMI) is a big problem in power systems that, like harmonics, can lead to inconsistent power and damaged components.

EMI is a particularly big issue for the renewable sector. Most renewable energy is generated in DC form, which must then be converted to AC before it can be used in the electrical grid. This is done using inverters that work efficiently but lower the power quality.

This affects many critical components in devices, including the SMPS and transformer windings.

To improve power quality, EMC filters can be used to limit the interference. These low- pass filters are designed to stop the flow of EM noise and reflect it back at the original source.

This requires the filters to be able to handle the power dissipation, so it is advisable that electrical engineers work closely with power quality specialists to ensure they choose the right solution.

The power quality problems we face in our electrical systems can appear daunting at first, but luckily, most can be easily addressed with the right equipment and planning. By keeping systems safe from interference, electrical engineers can ensure that all machinery and equipment stays cost-efficient and eco-friendly during use.