The increasing proportion of renewable energy and electric cars as well as new consumer services caused by the green and digital transition pose a challenge to the entire power grid. One of the major challenges is the increasing randomness and uncontrollability caused by renewable energy sources, which has the greatest impact on local low-voltage grids, as they were not designed to work in this way. The second challenge is greater price fluctuations in the electricity market, which will start to influence people’s consumer behaviour and create conditions for the shift in consumption to the widespread use of services. An uncoordinated shift of consumption may cause the overloading of low-voltage grids in particular. The third challenge is the ageing nature and timely upgrading of the power grid, which, if postponed, will intensify the power quality issues, including voltage issues. The latter causes equipment interruptions or reduces their lifespan, which in turn lowers consumer satisfaction.

Customer satisfaction and the factors affecting it

Researchers from the Tallinn University of Technology carried out a study among the owners of Estonian industrial enterprises and commercial properties, exploring their attitudes and experiences in regard to power supply. Based on the analysis, the primary causes of dissatisfaction were high electricity costs, the complexity of dealing with network operators and power quality issues. Short-term outages, supply voltage changes and power grid failures were considered the most significant power quality issues, which cause the stalling of production processes and malfunctions. The listed problems primarily arise from disturbances caused by weather conditions (wind, lightning), but also the condition of the power grid and substations, including natural deterioration, maintenance and reconstruction.

The actual cost of supply problems

According to Imre Drovtar, the decreasing lifespan and outages cost the industry and companies a great deal of money. In the European Union, the estimated damage caused by power quality issues exceeds 150 billion euros per year, and in the United States 80 billion dollars per year. Looking at various industrial sectors, the researchers of the Aalto University estimate that, for instance, the damage to the metalworking sector is 1.91 €/kW of peak power for a 1-second outage and in the case of a 15-minute outage, the damage is 12.68 €/kW. According to the same study, the economic loss borne by the timber sector is 1.49 €/kW and 6.67 €/kW respectively. In the study conducted by the Tallinn University of Technology, customers sensitive to short outages (i.e. less than three minutes) estimated that the average cost of an outage is around 40,000 euros. “In addition, the average cost of equipment damage caused by outages was estimated at 6000 euros,” notes Imre Drovtar.

Benefits of the new methodology for final consumers

According to Tarmo Korõtko, while the usual way of resolving power quality issues is to reconstruct power lines, it is economically unfeasible in certain areas due to the specificities of the installation or a negative demographic prognosis, and it may significantly increase the price of network services. The economic feasibility is questionable in areas where, for instance, the number of consumers is low, their number will decrease in the long term or the existing solution was projected improperly from the start. The drawback of the usual power grid reconstruction, where an outdated low voltage line is replaced by a new low or medium voltage line, is that the scope of the reconstruction does not take into account the specifics of the power quality issues, such as the duration, depth and frequency of voltage fluctuations, but rather solves it in a if-the-tyre-is-flat-buy-a-new-car manner.

According to Argo Rosin, in order to find a robust enough methodology to resolve the power quality problems in the low voltage grid, they had to:

• study the primary issues of final consumers and the economic impact which power quality has on them;
• find a new method to classify grid topologies;
• carry out measurements of grids of various topologies;
• study the technological and economic characteristics of traditional and alternative solutions;
• model and analyse the suitability of technological solutions for the different grid topologies and power quality issues; and
• draft a guide to solving issues, which takes into account techno-economic aspects.

According to Tarmo Korõtko, the significant advantage of the developed methodology is its robustness in terms of selecting a solution to resolve power quality issues. Namely, the new methodology allows us to save on costs both in the solution planning and construction stage. For instance, the methodology enables you to assess when it is more reasonable to invest in power grid reconstruction, invest in an energy storage device to improve power quality or to instead build a solution for off-grid electricity production. The methodology allows for a relatively short process to give a preliminary assessment of the economic feasibility of a project. To sum up, as the costs of electricity grid improvements are reflected in network charges, implementing this methodology will also make it possible to reduce the costs for final consumers.

The new methodology will be implemented in the development of the solutions of two pilot areas

The new methodology is currently being implemented and tested in the FinEst Centre for Smart Cities pilot project led by Tarmo Korõtko, which will demonstrate the use of energy storage devices and digital solutions in power distribution networks. The methodology for resolving power quality issues helps to prevent the quality problems caused by the increasing proportion of local production of renewable energy, as well as reduce the dependence on centralised power grids. The overvoltage caused by renewable energy solutions is a current reality in Germany, and the ever increasing popularity of micro-production among Estonian electricity consumers is a clear indicator that similar issues will soon manifest here as well.

The micro-grid pilot project is funded by the European Regional Development Fund and the Estonian Ministry of Education and Research. More information about the project is available at: https://www.finestcentre.eu/microgrids.