The central issue of energy efficiency in industrial processes and products is one of the most discussed issues during the last few years. This is because of unexpected increases in electricity costs, in conjunction with the post-Covid economic recovery and the beginning of the Russo-Ukrainian war.

Energy, in fact, has become a vital strategic asset for a company: companies have always treated this aspect marginally, without adopting optimization or energy saving actions, and have certainly been affected the most by these fluctuations.

Energy monitoring and energy efficiency are two sides of the same coin if I do not know where to act to apply efficiency improvements, in fact, it is likely that the latter efficiency actions will not be able to have the desired effect or perhaps worse, they are uneconomic; thereby, aggravating the company’s energy balance even more (hence the need to monitor ). If no action is taken, monitoring remains an end unto itself and the intrinsic added value of data is lost.

Energy monitoring allows company management to be guided at all levels toward increasingly aware strategic choices. So, let’s try to understand, at various levels, how to intervene via energy monitoring:

• Top management (CEO, president, etc., etc.): supports strategic decisions relating to the company’s energy policy. Guides in choosing the energy mix that best integrates with the company’s long-term strategies.
• Top directors (vice presidents, directors): supports  energy management for the plant or in defining development plans for a specific product.
• Middle management (project manager, department heads, supervisors, product owners): supports and guides process and product innovations aimed at reducing costs and CO2 emissions.
• Non-managerial positions: greater awareness of one’s work and the sustainability policy undertaken by the company and the acquisition of a background aimed at continuous improvement which, thus, permeates even at the lowest levels.

But what is it specifically about?

For a company, energy supply is one of the greatest challenges of the 21st century, in fact, the right choice of supply contracts and the right energy mix to be adopted to cope with production is of vital importance to maintain the profitability of the company itself.

In this article, we will discuss the problems that can lead to an increase in energy costs within a plant.

In order to address these topics with the right means, we must first describe the main electricity distribution systems for what concerns the industrial and civil sectors, belonging to the low voltage category (lower than kV):

• Single-phase system: it is the simplest alternating current distribution system, with a voltage, in this case, equal to 220V. It is widely used in the last segment of electricity distribution for not particularly demanding applications and, for these reasons, it is widely used in the commercial sector.

The single-phase voltage has the following characteristics:

• Has a frequency of 50 Hz (in Europe)
• The voltage has a voltage peak at 90 ° and a minimum at 270 °
• Three-phase system: it is the most used type in the industrial field for powering machinery. In these more conventional electrical systems, the three-phase voltages satisfy the following characteristics:
  • they are of equal width;
  • they are of the same frequency, 50 Hz for the Italian system;
  • the phases are 120 ° out of phase from each other.

In this case the voltage is 380V. The three-phase system is able to combine 3 alternating current circuits (for production, distribution and use of electricity) having the same frequency and 120 ° out of phase, thus guaranteeing users greater availability of power.

Figure 1. The main energy distribution systems.

Choosing a more efficient system

To give you a practical example of high added data value, have you ever heard of phase imbalances and network harmonics? Most likely not if you are unfamiliar with electronic circuits But, if you are the owner or manager of a manufacturing company, it is very likely that you have heard these terms at least once during your career.

Based on the actual need for industrial machinery, only one of the two distribution models will be chosen. For example, motors used in the industrial sector are more energy-intensive than those used in the commercial sector and require both higher torque values ​​and greater continuity of the latter. In this sense, three-phase current guarantees a greater availability of energy, since there is a voltage peak (and therefore torque) every 120 °, unlike a single-phase where there is a peak every 360 °.

Further, the higher voltage with the same power output allows reduction of current inside the motor, thus reducing temperature and sections of the conductors in the motor itself, with excellent advantages for reducing the total energy requirement.

One of the most common power quality problems in three-phase electrical networks is voltage imbalance. The causes that originate this imbalance mainly relate to the connection of single-phase loads to the mains, since they absorb different current intensities in each phase producing, in turn, asymmetrical voltages. This is a very common case in industrial plants where the branches for civil use added after the first installation are obtained starting from the three-phase line.

Figure 2. Voltage imbalances in three-phase networks.

These imbalances can become the source of serious damage to electrical circuits and electronic equipment.

Suffice it to say, that a voltage imbalance of 2.3% on a 400V motor creates a current imbalance of almost 18%. Currents that dissipate inside the motor itself cause a series of problems such as:

• Overheating. The voltage imbalance considered in our example can lead to a temperature increase of at least 30 ° on the motor. The current flowing inside the conductors, in fact, increases and, with it, the temperature because of the Joule effect.
• Abnormal noise and excessive vibration, if these phase imbalances occur, the torque on the motor will not be steady, but will be higher at times and lower at others, thus, triggering vibrations and, therefore, anomalous noise throughout the motor body

However, voltage imbalance is not the only power quality problem that affects three-phase systems found in industrial plants. Another problem that occurs is related to network harmonics.

When electrical equipment is powered with alternating current it is expected that by providing a sinusoidal voltage, an equal sinusoidal current is obtained.

Figure 3.  Sinusoidal shape obtained from network harmonics.

This is true, but only for linear loads. Non-linear loads (such as those found in computers, motors equipped with inverters, etc.) have a relationship that is no longer respected, and harmonic distortions end up generating anomalies in   voltage values of the neutral line with respect to the potential. of ground causing:

• Overheating of the conductors: Depending on the order of the harmonic that is introduced into the network, the distribution of the current flow inside the conductorchanges with the flow concentrated in the outermost parts of the conductor.
• Reduction of power factors (inefficient use of electricity). The power factor is the ratio between active power (the one that is actually transferred to the grid loads) and apparent power. The effective value of the current depends on the harmonic content of the latter; the higher the harmonic content is, the higher the apparent power will be at the same effective voltage. This results in a decrease in power factors.
• Increase in network losses: The increase in the effective current value with an increase of the harmonic content induces greater network losses due to both the joule effect and the skin effect.
• Irregular operation of control and protection relays: In the presence of an important harmonic content, there is a tendency for protection relays to activate more slowly
• Onset of faults in electronic equipment: Harmonics in fact disturb parts of the circuit related to zero crossing
• Risk of measurement errors forOT equipment with all the safety and process control problems that would arise.

Additionally, network harmonics generate a strong economic impact on energy consumption:

• Higher costs due to increased network losses and the low power factor with an increase in the reactive part of power.
• The presence of harmonic currents in the network increases contractual power levels and consequently the cost of the subscription; not to mention that this tightening will be more severe overtime since energy distributors will tend to penalize those who produce harmonic disturbances.

Higher costs from component oversizing to try to reduce fire risks and network losses.

IoT technologies that support the monitoring process

IoT platforms are useful for complete monitoring of consumption related to production processes. If the company is able to extract data about the operation of its machinery,  it will also be able to understand which strategy to implement in terms of energy efficiency. Tracking the parameters related to voltage, harmonics, imbalance, etc. is essential for testing the reliability of the system and then deciding whether to make changes to the asset.

Thanks to the versatility of its platform, Zerynth allows the monitoring of consumption and some power quality parameters through instruments certified by experts in the electrical measurement sector.

Furthermore, Zerynth is able to attribute these data in a timely and limited manner even to a single area of ​​interest (machinery, production station, or building), making the data accessible on the network and creating a history, which can be consulted at any time and from any platform (PC, smartphone or tablet). This makes it available for integration with MES and ERP via an API.

If you found this interesting, and want to dive deeper into the subject and want to know the operation and benefits of the Zerynth IoT platform, you can find more information on our website.