Quality Of Electrical Energy Research Articles

LOSSES OF ELECTRICAL ENERGY DUE TO ITS LOW QUALITY AT PUMPING STATIONS OF HEATING NETWORK ENTERPRISES

The issue of increasing the reliability of the facilities in the energy system of Ukraine is considered. It is noted that Ukraine lacks sources of electric energy as a result of hostile actions. In addition, the level of electric energy losses is very noticeable. Even according to pre-war statistics, the level of losses exceeded 10 % of all energy produced. And this was a consequence of the wear and tear of both electrical equipment and insufficient quality of electric energy. And as a result of hostile actions, the destruction of energy equipment led to an even worse decrease in the parameters of the quality of electricity. The priority is to maintain the operability of the energy system, while quality indicators are relegated to the second place. For most electricity-consuming equipment, deterioration in the quality of electricity can have a multiplier effect. Manifesting itself as a sharp increase in losses. For enterprises whose work provides for the vital needs of the population, the quality of electric energy is not a criterion. The main goal is to maintain operability. Such enterprises also include enterprises of heating networks. Almost all devices and equipment of heating companies operate on electricity. Forced movement of the coolant in the network is created only by electric pumps receiving torque from asynchronous electric motors. Such motors are characterized by increased losses of electrical energy if its quality is poor. Measurements of the quality of electrical energy were made at two different heat supply enterprises. The article presents the results of the measurements. Despite the fact that the heat supply enterprises are very different (the first serves more than 30 thousand residents, the second – more than 8 thousand residents), the results of the measurements show the affinity of problems with the quality of electrical energy. The overwhelming majority of electrical energy quality indicators do not meet the requirements for the quality of electrical energy. The most critical deviations are in the values of average voltage and average positive sequence voltage, which may not meet the standard in 100 measurements out of 100. The deviation of the voltage asymmetry coefficient for zero sequence also exceeds the standard values. The authors draw attention to the presence of a deviation of the average coefficient of the n-th harmonic component of voltage in all phases. The specificity of the operation of heat supply enterprises' equipment is that their operating modes are continuous throughout the entire heating season. And losses in the network can accumulate. In addition, one of the consequences of using low-quality electricity is a reduction in the service life of electrical equipment. The authors propose general methods for correcting the situation and emphasize the need to conduct a study of electrical equipment of heat supply enterprises in order to develop measures to improve their operation and reduce energy losses.

Study on the Resonance Characteristics and Active Damping Suppression Strategies of Multi-Inverter Grid-Connected Systems Under Weak Grid Conditions

When a multi-inverter grid-connected system is influenced by the parasitic parameters of LCL-type inverters and the impedance of the connected system’s lines, its resonance characteristics become more complex and difficult to predict. For LCL-type multi-inverter grid-connected systems, a mathematical model that considers the effects of parasitic parameters and line impedance has been established, leading to the derivation of the system’s Norton equivalent circuit and a general expression for the inverter output current. The resonance characteristics of multi-inverter grid-connected systems composed of inverters with the same and different parameters were analyzed under the influence of parasitic parameters and line impedance. To suppress the resonance in multi-inverter grid-connected systems and address the issue of traditional PI control not meeting grid requirements for LCL-type grid-connected inverters, a strategy combining superhelical sliding mode control with active damping was adopted. To verify the practical performance of the adopted resonance suppression strategy in complex environments, a grid-connected system model containing two LCL-type inverters was constructed using the MATLAB/Simulink software platform, followed by simulation analysis. The simulation results strongly confirm the feasibility and effectiveness of the adopted resonance suppression strategy, considering the effects of parasitic parameters and line impedance. This strategy demonstrates significant suppression effects in addressing resonance issues caused by parasitic parameters and line impedance, effectively enhancing the quality of grid-connected electrical energy.

Analysis of features of electric energy quality management and voltage regulation in housing and communal services

Subject of research: methods of improving the quality of electric energy in electric networks used for power supply mainly to municipal consumers in urban areas. The purpose of the study is to determine the most relevant methods for improving the quality of electric energy of municipal consumers, their advantages and disadvantages, as well as determining the direction of modernization. Methods and objects of research: the object of research in this material is the housing and communal complex in urban areas, in particular the electric grid complex. The work is based on such scientific research methods as analysis, synthesis, modeling and generalization. The main results of the study: the analysis of the features of electric energy quality management and voltage regulation in modern conditions. The importance and necessity of using modern intelligent systems to improve reliability, energy efficiency and quality of electric energy i s highlighted. The key prerequisites for the introduction of smart systems for monitoring the state of the electrical network are formulated. The tasks, the solution of which is necessary for the modernization of the complex, have been identified. A proposal has been made to use artificial intelligence-based systems as the main tool for modernization.

LABORATORY PLATFORM FOR DEMONSTRATING THE SYMMETRICAL COMPONENTS ȚUGULEA POWER THEORY APPLIED ON GRID MODELS WITH NEUTRAL CONDUCTOR

In the context of the ever-increasing complexity of modern power systems, optimizing consumers’ performance to improve electrical energy quality becomes paramount. This article thoroughly examines the power transfer effects in the context of distorting and non-symmetrical regimes in three-phase, four-wire power systems, focusing on heavily nonlinear and unbalanced consumer influence across the grid. Particular emphasis is placed on the impact of these regimes on the parasitic active and reactive powers affecting linear and balanced consumers due to distorting and unbalanced ones. An essential aspect of this analysis is including the neutral conductor in the experimental circuit, enhancing relevance and a more profound understanding of consumer interactions in modern networks. Quantitative aspects of the phenomena involved are assessed from the perspective offered by SCPT (introduced by Andrei Ţugulea), allowing us to identify the source of non-symmetry and residual powers through comprehensive power balance equations for the active and reactive powers.

Research of the distribution symmetrical components in an electrical system with a diesel generator at an unsymmetrical load

Purpose. Investigation symmetrical components of current and voltage in microgrid elements with an autonomous synchronous generator of limited power, which works in parallel with a network transformer under the condition of non-metric load. Methodology. During the research, visual programming methods were used in the Simulink/Matlab package, methods of electrical engineering theory in terms of determining symmetrical component currents and voltages in observation branches, methods of synthesizing schemes for replacing elements of electric power systems for symmetrical component currents, methods of data processing and construction diagrams using specialized software tools.. Findings. As a result the analysis known studies, it was established that under the condition of researching low-power generating systems in conditions of asymmetry, insufficient attention is paid to the nature of the asymmetric load. Using the well-known structure of a microgrid, which includes a synchronous generator, a machine load, and an external network transformer, its model was built, in which, by introducing asymmetric loads of various types, a series of experiments was implemented with the registration of voltages and currents of forward, reverse, and zero sequences in the branches of the network. The analysis of the results obtained during the research established that the positive sequence voltage in the case of a change in the active load does not change its level, under the same circumstances, in the case of an active-capacitive and active-inductive load, the voltage change has the opposite character. In the case of increasing asymmetry of an active-inductive nature, the positive sequence voltage decreases, and in the case of an active-capacitive one, it increases. The specified changes in some cases exceed 3%. Positive sequence currents in the case of active load imbalance differ slightly. In the case of a positive sequence current of the transformer, its continuous growth is observed, which in the case of active-capacitive and active-inductive loads exceeds the active one by an average of 1.5 times. Negative sequence currents in the studied model, which are formed by an asymmetrical load, are completely closed to the transformer, causing zero-sequence voltages, and the nature asymmetrical load significantly affects the value of these currents, a 61% increase was noted. Originality. It was established that in a microgrid, which includes a synchronous generator, a machine load, a symmetrical active load of comparable power to the generator, an external network transformer, in addition to the fact of asymmetry caused by an asymmetrical load, the character of an asymmetrical load (active, active-inductive or active-capacitive). Practical value. In the case of using in microgrids devices that provide an increase in the quality of electrical energy, for example, symmetrical devices, it is necessary, in addition to the asymmetry factor, to take into account the natural load that causes the latter.

Investigation of Devices for Measuring the Quality of Electrical Energy

Investigation of Devices for Measuring the Quality of Electrical Energy

Development of airfield electrical power systems for military aircrafts

The article presents selected problems in the operation of airport power supply systems (LZE), resulting from the growing needs in terms of increasing power and ensuring the appropriate quality of electrical energy supplied to aircraft installations and receivers. The main stages of development of airport power supply systems for aircraft are reviewed. The basic technical structures of airport power supplies for aircraft were presented, divided into two groups: stationary (without the possibility of moving and with the possibility of moving) and mobile (placed on wheels that are an integral part of the LZE structure, including self-propelled with operator's cabin, self-propelled without operator's cabin, mobile but not self-propelled).The basic principles of cooperation of LZE systems with the aircraft's on-board electrical network and a description of the organizational and technical structure of military ground-based power supply systems are given. The main direction of current work is the results of technical analysis of selected damages to airport power supply systems and proposals to improve the situation on the example of airport control devices LUK-1 and LUK-2 built at ITWL, dedicated to diagnosing the technical condition of LZE systems.

Influence of the quality of electrical energy on the operation of the main elements of electric arc plasma systems for thermochemical fuel preparation

The work is devoted to the study of the influence of the quality of electrical energy on the service life of electrodes of plasma thermochemical fuel treatment systems used in thermal power plants running on coal fuel. The issues of moving the near-electrode plasma section using magnetic wave scanning are discussed in detail. The ANSYS Maxwell software was used as the main research tool. The computer simulation was performed with the following main experimental parameters: the coefficient of asymmetry in the zero sequence (K0U) is 2% and 4%; the coefficient of asymmetry in the negative sequence (K2U) is 2% and 4%; the voltage deviation dU(+) is 5% and 10%; the materials used for manufacturing electrodes: copper (Cu), a pseudo-alloy of tungsten, nickel and copper – (W + Ni + Cu), a pseudo-alloy of molybdenum, tungsten and copper – (Mo + W+ Cu). Based on the obtained simulation results, graphical representations of changes in the trajectories of the near-electrode plasma section under various distorting factors, dependences of changes in the values of specific erosion of various electrode materials, graphical dependences of changes in the service life of electrodes of plasma systems are constructed. The studies performed using computer modeling based on the ANSYS Maxwell software product made it possible to quantify the effect of voltage distortions on the trajectory of the near-electrode plasma section and, consequently, the service life of the plasmatron electrodes. In particular, in the course of the study, a detailed assessment and analysis of the degree of influence of the following indicators of electrical energy quality was performed: the coefficients of asymmetry in the negative and zero sequence, voltage deviations on the operation and technical condition of the electrodes of plasma systems. The results of the study were discussed, and recommendations were formulated for the use of plasma thermochemical fuel preparation systems used at thermal power plants to ignite the fuel of pulverized coal boilers.

Study of the State Primary Measurement Standard of the Unit of Phase Shift Angle Between Two Voltages

Phase measurements are necessary for determining main parameters of the oscillatory process in complex electrical networks. Most often, it is precisely the phase shift angle (PSA) between two oscillatory processes of the same frequency that is measured. An essential indicator of the quality of electrical energy is the coefficient of asymmetry in a three-phase electrical network, which depends on the load of consumers in this network. This indicator is affected by a short circuit between two phase voltages. Phase measurement standards, phase meters, and phase converters are included in the measuring equipment for phase measurements. They are widely used in such fields as radiolocation, radio navigation, non-destructive testing, radio engineering, telecommunications, acoustics, metallurgy, machine and aircraft industry, space industry, as well as in scientific research and defence. The State Measurement Standard of Ukraine of the PSA unit between two voltages in the frequency range from 0.01 Hz to 10 MHz is maintained at the State Enterprise “UKRMETRTESTSTANDARD”, Kyiv. It provides metrological traceability of phases measured in the country. The main components of the standard were calibrated at the PTB, the National Metrology Institute of Germany. In Ukraine, numerous measurement standards and measurement instruments for phase measurements (more than 500.000 units) are used, in particular, phase calibrators, phase meters, phase shifters, synchronoscopes etc. Regular study of metrological characteristics of the DETU 09-07-11 measurement standard is conducted both in the main (from 5 Hz to 200 kHz) and in the extended (from 0.01 Hz to 10 MHz) frequency range. The PSA values obtained as a result of the research in the main frequency range do not exceed 0.001° (which is maximum according to measurements at all calibration points 0.00015°), and in the extended frequency range – 0.01° (which is maximum according to measurements at all calibration points 0.0053°). To eliminate the systematic measurement uncertainty component of the phase measurement standard, a special calibration is regularly performed using a set of resistive and capacitive phase bridges.

Power Wheeling Pricing Considering Congestion in Power Network: A Review

Limited capacity of the power system infrastructure has a limiting effect on the quantity of electrical power that can be transmitted thereby resulting in the system been congested which also affects the quality of electrical energy supplied. Congestion is an undesired effect in power system with serious economic, reliability and security effect on power system infrastructure, which are yet to be adequately quantify in term of cost. Congestion occurrence and management on the power system network has been studied extensively, causes of congestion and various management techniques have been proposed which are at great financial consequences. While setting transmission wheeling prices, congestions are not adequately considered, nor are the management methods accurately financially compensated. Some wheeling pricing techniques however recognises the short coming and takes into consideration the financial cost of congestion and it’s management methods when setting their transmission wheeling costs. This paper is a review of wheeling methods that takes into consideration the cost of congestion and the management techniques when setting wheeling prices and makes a recommendation using financial and economic implication of the occurrence of congestion and the management techniques adopted in reducing the impact when setting wheeling prices, in order to encourage investment into the transmissions system infrastructures.

Use of reactive power compensation devices in implementation of distributed generation

In Ukraine, a gradual reduction of electricity production at thermal power plants is planned due to the development of renewable sources of electricity. Small hydraulic power plants are being restored, solar power plants and wind power plants are being built. This will allow solving the existing problems of the domestic energy industry regarding the shortage of fuel resources, energy security and reducing the level of harmful effects on the environment caused by the operation of traditional sources of electricity. There is a trend of transition from a purely centralized electricity supply to a combined one, when the number of local decentralized sources of electricity directly in distribution networks is increasing. In this way, distribution electric networks are gradually transformed into a network with features characteristic of a local electric system, which receives power both from its own distribution electric networks and from a centralized source - the electric power system. Renewable energy has a number of advantages compared to traditional energy, but there are also disadvantages. Among them, the complications of the functioning of electrical networks should be highlighted in the event of an increase in the capacities of renewable sources of electricity installed in them and the instability of generation due to their natural dependence on meteorological conditions, if we talk more specifically about technical shortcomings, then this concerns - sinusoidal of voltages and currents and voltage deviations, quality assurance of electricity, which directly depends on ensuring the balance of active and reactive power in the electrical system. Hence the need for coordinated power supply from renewable sources of electricity and substations of the power system. At the same time, there is a gradual transition from the wholesale electricity market of a single buyer to the balancing market of electricity and electricity supply under bilateral agreements, as well as the introduction of market management methods. This article discusses measures to reduce electrical energy losses, limit voltage deviation, improve the quality of electrical energy, and compensate for the reactive power of local loads due to the introduction of reactive power compensation devices together with renewable sources of electricity and facilitating their integration into the power grid.

Spatial analysis of electrical distribution system in obio-akpor local government area, rivers state, Nigeria

The distributions of quality electrical energy to end users and, achieving a reasonable level of customer’s satisfaction from the electricity distribution companies servicing most area are faced with divers’ spatial problems particularly with the use of dilapidated infrastructures and poor services. This study used spatial techniques to analyze the spatial characteristics of the electrical distribution system in Obio-Akpor Local Government Area, Rivers State. It also examined the ward pattern of Port Harcourt Electricity Distribution (PHED) customer’s satisfaction and also predicted the ward level of customer’s satisfaction within the study area. Primary and secondary data were used for the study. The primary data on customer’s satisfaction of PHED services was obtained from questionnaire survey. Purposive sampling method was used for this study and the population for the study is the entire customers of PHED in the study area. The secondary data consist of ward boundary map of the study area, satellite image, PHED network spatial data and attribute data of all the 3200 (three thousand two hundred) transformers (11/0.415KVA and 33/0.415KVA) within the study area as at the time of this study. Geospatial analysis such as clip analysis, buffering were carried. The data attribute were analyzed using average nearest neighbor analysis, kernel density, zonal statistics, inverse distance weighting and geographical weighted regression to obtain the desired aim of the study. The result show that, the location pattern of PHED transformers are clustered. Result further reveal that the ward pattern of customer’s satisfaction are geography dependent with either positive, negative or mixed relationship.

Analysis of Dynamic Parameters of the Switching-On Process of Electromagnetic Relays Powered by Harmonic Polluted Voltage Source

The article incorporates an analysis of the switching-on process of alternating current (AC), low-voltage (LV), and electromagnetic (EM) relays energized by harmonically polluted voltage sources. In the undertaken research, the dynamic parameters of relays actuated by electromagnetic drive were examined for shape and supply voltage waveform distortion levels as described by different THD factor values. During the research, diverse supplying voltages were delivered to drive electromagnet coils at a variety of phases so as to reflect the stochastic nature of the energizing procedure. The performed analysis allowed for determining the most influential and decisive factors dictating the basic parameter values of the switching-on process. As an outcome, time-related parameters of relay moving armature movement were obtained, and the frequency of disorder occurrences during the switching-on was examined. For experimentation needs, an experiment stand was developed, and dedicated software for measurement results analysis was elaborated. Based on the study results, EM relay switching-on operation reliability was evaluated in view of electric energy quality.

A Systematic Investigation into the Optimization of Reactive Power in Distribution Networks Using the Improved Sparrow Search Algorithm–Particle Swarm Optimization Algorithm

With the expansion of the scale of electric power, high-quality electrical energy remains a crucial aspect of power system management and operation. The generation of reactive power is the primary cause of the decline in electrical energy quality. Therefore, optimization of reactive power in the power system becomes particularly important. The primary objective of this article is to create a multi-objective reactive power optimization (MORPO) model for distribution networks. The model aims to minimize reactive power loss, reduce the overall compensation required for reactive power devices, and minimize the total sum of node voltage deviations. To tackle the MORPO problems for distribution networks, the improved sparrow search algorithm–particle swarm optimization (ISSA-PSO) algorithm is proposed. Specifically, two improvements are proposed in this paper. The first is to introduce a chaotic mapping mechanism to enhance the diversity of the population during initialization. The second is to introduce a three-stage differential evolution mechanism to improve the global exploration capability of the algorithm. The proposed algorithm is tested on the IEEE 33-node system and the practical 22-node system. The results indicate a reduction of 32.71% in network losses for the IEEE 33-node system after optimization, and the average voltage of the circuit increases from 0.9485 p.u. to 0.9748 p.u. At the same time, optimization results in a reduction of 44.07% in network losses for the practical 22-node system, and the average voltage of the circuit increases from 0.9838 p.u. to 0.9921 p.u. Therefore, the proposed method exhibits better performance for reducing network losses and enhancing voltage levels.

A new high-frequency multilevel inverter effecting cables weight and energy efficiency of aircraft

Purpose Static inverters are very important for the emergency energy distribution system of aircraft and similar machines. At the same time, the electrical energy produced at high frequency for electrical devices is used to reduce the weight of the cables in the aircraft and spacecraft because of the skin effect. In the high-frequency system, a thinner cable cross-section is used, and a great weight reduction occurs in the aircraft. So, fuel economy, less and late wear of the materials (landing gear, etc.) can be obtained with decreasing weight. This paper aims to present the development of a functional multilevel inverter (FMLI) with fractional sinus pulse width modulation (FSPWM) and a reduced number of switches to provide high-frequency and quality electrical energy conversion. Design/methodology/approach After the production of FSPWM for FMLI with a reduced component, which, to the best of the authors’ knowledge, is presented for the first time in this study, is explained step by step, and eight operating states are given according to different FSPWMs operating the circuit. The designed inverter and modulation technique are compared by testing the conventional modular multilevel inverter on different loads. Findings According to application results, it is seen that there is a 50% reduction in cross-section from 100 Hz to 400 Hz with the skin effect. At 1000 Hz, there is a 90% cross-section reduction. The decrease can be in cable weights that may occur in aircraft from 10 kg to 100 kg according to different frequencies. It causes less harmonic distortion than conventional converters. This supports the safer operation of the system. Compared to the traditional system, the proposed system provides more amplitude in converting the source to alternating voltage and increases the efficiency. Practical implications FSPWM is developed for multilevel inverters with reduced components at the high frequency and cascaded switching studies in the power electronics of aircraft. Social implications Although the proposed system has less current and power loss as mentioned in the previous sections, it contains fewer power elements than conventional inverters that are equivalent for different hardware levels. This not only reduces the cost of the system but also provides ease of maintenance. To reduce the cable load in aircraft and create more efficient working conditions, 400 Hz alternative voltage is used. The proposed system causes less losses and lower harmonic distortions than traditional systems. This will reduce possible malfunctions and contribute to aircraft reliability for passengers and cargo. As technology develops, it is revealed that the proposed inverter system will be more efficient than traditional inverters when devices operating at frequencies higher than 400 Hz are used. With the proposed inverter, safer operation will be ensured, while there will be less energy loss, less fuel consumption and less carbon emissions to the environment. Originality/value The proposed inverter structure shows that it can provide energy transmission for electrical devices in space and aircraft by using the skin effect. It also contains less power elements than the traditional inverters, which are equivalent for different levels of hardware.

ANALYSIS OF REACTIVE POWER COMPENSATION MEANS IN ELECTRIC NETWORKS OF AZERBAİJAN

The article analyzes the existing reactive power compensation in the electrical systems of Azerbaijan, and also examines the problems and shortcomings that arise in the reliable supply of electrical energy to consumers and provides information about the sources of RP that are produced in the industry of the republic. The most important task that requires solving the problem of improving the quality of electrical energy in the country's networks, both at the design stage and at the operation stage of electrical power supply systems, is reactive power compensation. Based on this, it is necessary to select RP sources, their favorable placement, regulation and calculation of their power in accordance with the existing power supply system. Benefits RP in industrial electrical networks include many issues, the solution of which is aimed at increasing the effective power factor and stability of electrical devices, their efficiency, improving the quality of electricity and, in general, the reliability of the electrical system. Currently, there are still issues that have not been resolved and require a special approach for their implementation. Such important issues include: determining the installation of compensation devices, choosing their number, type, safe operation and protection. In the industrial power grids of Azerbaijan, issues of automatic control of RP are at the development stage and for this development, adequate mathematical models of a rational RPK system with minimal losses are being considered. To solve the above, targeted scientific methods are created. The problem of RPK in modern electrical systems of Azerbaijan is important for the following reasons: 1) the consumption of reactive energy increases due to an increase in loads with the consumption of reactive current in the country’s electrical networks; 2) the growth of RP consumption is accelerating compared to active consumption in many sectors of industrial production; 3) there is an increase in reactive energy consumption not only in large urban power grids, but also in small rural ones. Keywords: reactive power, compensating devices, electrical devices, energy, system, quality, synchronous compensator, static capacitor.

Requirements and Main Indicators for the Quality of Electrical Energy

From the calculated results, it can be seen that the to different levels in different facilities differs to a certain extent. In this case, these differences are smaller for the 10-second period and larger for the 60-second period. In addition, the shape of the histogram and the character of the parameters of the deviation are the same for all facilities. In the case of a time period of 10 seconds, the value of the mathematical deviation differs from each other by ±0.5%, and in the period of 60 seconds, ±0.7%. However, the differences of the standard deviations do not exceed ±0.1%. Thus, when using the information obtained by the statistical analyzer of the quality of deviation, it is necessary to draw all the characteristics obtained by means of this facility: the shape of the histogram, the probability of falling into different levels, the average value and the standard deviation. As a lawyer, the most stable information about the road network is standard. Taking this into account, this quantity should be used when determining the quality of the change.
 The following main results were obtained: The quality indicators of electric energy are determined by the distribution of voltage, waves, the symmetrical characteristic of the three-phase periodicity and the non-sinusoidal characteristic of the voltage. The proposed control system allows real-time monitoring of energy quality.

Quality of power energy from wind power plant

The aim of this paper is to measure the quality of power coming from the wind power plant to the electrical distribution network. The quality of electrical energy includes many parameters but the main thesis target is to measure a harmonic frequency of current. I used the program Matlab for the simulation of the connection between the wind power plant and the electrical network. I simulated startup of the wind turbine and changes of wind flowing. Obtained data were plotted on graphs which show harmonic frequencies of current based on these changes.

ENERGY RESISTANCE OF MEDICAL FACILITIES DURING TRANSIENT OPERATION MODES OF THE ENERGY SYSTEM

The question of increasing the reliability of the operation of objects in the energy system of Ukraine is under consideration. It is shown that the issue of energy supply of public facilities received new requirements during the war. Especially such requirements now apply to medical facilities. The main types of energy for medical institutions are the supply of electrical and thermal energy. For Ukraine, on the basis of climatic features, the consumption of thermal energy is much larger than that of other types of energy. Therefore, one of the important steps to reduce energy consumption is thermal modernization of buildings. This paper considers the general energy supply system, which includes not only heat supply but also electricity supply. It is necessary not only to have the electricity itself in the network, but also to meet the quality requirements. Medical electrotechnical complexes are one of the most critical to the quality of electrical energy. Correct diagnosis and maintenance of vital activity of the patient's organism depend on their work. It is proposed to assess the state of energy supply through the model of mutual dependence of energies. Therefore, qualitative changes in thermal energy indicators cannot be compensated for by network solutions. Maintaining the temperature in the premises is possible precisely due to the use of other heat sources. In terms of the energy connectivity model, the only way to equalize the "body of energy consumption" is the mutual replacement of one energy by another. Variants of equalization of the "body of energy consumption" for medical institutions are defined. A presentation of the "body of energy consumption" is proposed, with a reflection of the qualitative limits of the shape of the "body of energy consumption" in relation to thermal energy. The concept of the limit of energy sustainability according to qualitative indicators is introduced. A number of measures to support energy sustainability have been identified. In order to achieve the longest compliance with energy supply quality indicators, it is proposed to disconnect part of the premises from the energy supply system while preserving the energy supply group for those premises that will remain. It is noted that using the criterion of energy sustainability, it is possible to analyze construction structures and technological processes in the buildings themselves in order to develop measures to increase energy sustainability with a given direction.

Power Quality of Supply Characterization in the Portuguese Electricity Transmission Grid

REN – Rede Eléctrica Nacional S.A., as the concessionaire of the Portuguese National Electricity Transmission Grid (RNT), has an important role in electrical energy quality to the final customer. Continuity of supply general/individual indicators and parameters are defined in accordance to the regulatory legislation stated in the Portuguese Quality of Service Regulation (RQS). Voltage quality assessment is done by REN and is based on a monitoring plan that includes voltage characteristics measurement at selected delivery and internal points. A study was conducted in order to characterize all the bus bars that were monitored between 2010 and 2011. It was used a simple methodology based on labeling the power quality. On this paper, it will be shown this methodology and the results obtained in characterizing the delivery points of the Portuguese Electricity Transmission Grid (RNT) for the period 2010-2011, as well as other REN quality of supply results in the last years.