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The growing share of medium voltage cable lines in distribution networks challenges distribution network operators in terms of proper mode of operation of these lines. It is related to the reduction of energy losses in cable conductors and metallic cable screens. The article focuses on energy losses in metallic cable screens of cable lines and substation busbar bridges composed of single-core cables with metallic screens and possible ways of their reduction. Simulation and measurement analysis of the level of energy losses in the metallic screens of cables is presented together with the economic analysis of various variants of losses reduction through the change of the way these screens are operated in relation to the traditional bilateral earthing at both ends of cable. Technical problems and threats connected with the use of considered modifications of metallic screens operation during earth fault disturbances in distribution networks are also presented

Demand side response is becoming an increasingly significant issue for reliable power systems&rsquo, operation. Therefore, it is desirable to ensure high effectiveness of such programs, including electricity tariffs. The purpose of the study is developing a method for analysing electricity tariff&rsquo, s effectiveness in terms of demand side response purposes based on statistical data concerning tariffs&rsquo, use by the consumers and price elasticity of their electricity demand. A case-study analysis is presented for residential electricity consumers, shifting the settlement and consequently the profile of electricity use from a flat to a time-of-use tariff, based on the comparison of the considered tariff groups. Additionally, a correlation analysis is suggested to verify tariffs&rsquo, influence of the power system&rsquo, s peak load based on residential electricity tariffs in Poland. The presented analysis proves that large residential consumers aggregated by tariff incentives may have a significant impact on the power system&rsquo, s load and this impact changes substantially for particular hours of a day or season. Such efficiency assessment may be used by both energy suppliers to optimize their market purchases and by distribution system operators in order to ensure adequate generation during peak load periods.

Adequate power system protection plays crucial role in ensuring reliability of electricity supply, thus it is a key challenge for distribution system operators to increase the effectiveness of protection schemes operation and protection equipment itself. The main goal of the paper is presenting a multi-criteria protection algorithm that may boost effectiveness of power lines’ short-circuit overcurrent relays in medium voltage networks in case of various two phase faults. The idea of enhancing protection performance is based on fault current symmetrical components’ analysis and specifically on using negative and zero sequence currents as criterial values for overcurrent line protection used against such faults. The paper describes in detail the proposed solution and analyses its performance based on medium voltage network simulations carried out using DIgSILENT PowerFactory software. Promising simulation results can be observed for definite time overcurrent protection relays used in reactance-earthed networks, as introduction of the proposed method proved to increase the zone of effective operation twice comparing to the traditional phase current based solutions. Moreover, in the proposed solution, coordination of protection settings for small earth-fault current values, which are identified by other protection relays, is not necessary. The proposed solution may complement the traditional algorithms for short-circuit protection (I≫) used in modern protection relays monitoring the level of negative and zero sequence current, and therefore may significantly improve the effectiveness of detecting various phase-to-phase faults in the considered MV line protection zone.

The concept of price elasticity of demand has been widely used for the assessment of the consumers’ behavior in the electricity market. As the residential consumers represent a significant percentage of the total load, price elasticity of their demand may be used to design desirable demand side response programs in order to manage peak load in a power system. The method presented in this study proposes an alternative approach towards price elasticity determination for zonal tariff users, based on comparisons of load profiles of consumers settled according to flat and time-of-use electricity tariffs. A detailed explanation of the proposed method is presented, followed by a case-study of price elasticity determination for residential electricity consumers in Poland. The forecasted values of price elasticity of demand for the Polish households using time-of-use (TOU) tariff vary between −1.7 and −2.3, depending on the consumers’ annual electricity consumption. Moreover, an efficiency study of residential zonal tariff is performed to assess the operation of currently applicable electricity tariffs. Presented analysis is based on load profiles published by Distribution System Operators and statistical data, but the method can be applied to the real-life measurements from the smart metering systems as well when such systems are accessible for residential consumers.

This paper presents novel zero sequence current filter and earth fault protection relay, which utilize cable screens earthing current in protection algorithm. Different problems connected with state of the art of zero sequence current filters and protection relays are presented and compared with the proposed solution. The presented concept is verified in PowerFactory simulation software, experiment concerning modeling the earth fault current flow in medium voltage (MV) cable supplied from the low voltage (LV) network and measurements in the MV network in the Polish distribution system. The proposed solution is characterized by higher sensitivity and reduced number of erroneous trips. The presented solution is suitable for any MV cable lines. Biggest advantages are observed in power output lines from renewable energy sources, which are often operated under no-load conditions.

Price elasticity of electricity demand values are crucial for a proper design or retrofit of time-of-use electricity tariffs. The aim of this paper was to propose an alternative methodology for determination of self and cross price elasticity of demand with daily resolution for electricity customers changing their settlement to the time-of-use tariff. Progressing implementation of smart metering systems provides access to more accurate data reflecting the consumers’ electricity consumption with at least hourly resolution, which has been a motivation to use load profiles data to analyze customer’s price elasticity. The method is based on load profiles’ comparison of customers using flat and time-of-use tariffs. A case-study example is presented for residential consumers settled according to time-of-use tariff in the area of one of Polish distribution system operators and the resulting price elasticity values vary significantly over the year. Effectiveness of zonal tariffs is also evaluated, along with their impact on the power system’s load in the summer and winter peak load periods. The results may be used by supply companies and distribution system operators to improve efficiency of applied demand response programs based on time-of-use tariffs and thus influence the safety of the power system operation.

This article presents the issue of electricity consumption for space heating purposes. High share of fossil fuels used for space heating leads to high pollution emission. A solution for this problem may be encouraging customers to use electricity as an energy carrier for space heating, by proposing appropriate tariffs. Diverse electricity tariffs for households are described, differing in energy prices and distribution rates in certain periods of a day. Demand price elasticity is calculated by comparing energy increases in zones using standard load profiles of customers settled according to the flat tariff and the time of use tariff. The values of demand price elasticity are then used to create customers' load profiles based on price changes within newly proposed tariffs. A forecast of the consumption rise resulting from the new implemented anti-smog tariff motivating consumers to use electricity during the low load period in the Polish power system is presented.

This article analyses the potential of using electricity for supplementary heating purposes in households during low outside temperatures periods. Space heating using solid state fossil fuels, causes significant pollution of the local environment. In order to assess the potential of replacing fossil fuels with electricity for the supplementary heating purposes, the conditions determining financially reasonable exchanges of the main energy carrier consumption for heating purposes into electricity were analysed as a result of a change in price of this substitute. The concept of cross price elasticity of demand was used to reflect the current price conditions for energy carriers exchange and its values were determined for the energy contained in the most frequently used carriers for heating purposes, in relation to changes in electricity prices. The possible reduction in average electricity prices was considered, resulting from tariff change from a single zone to a two-zone tariff in the case of storage heater use, consuming electricity only in the off-peak zone. What is more, the potential of anti-smog tariff implemented in 2018 concerning the considered aspect was also analysed.

In this paper the issues related to the ability to modernize the neutral point of compensated MV grid and benefits associated with it are presented. In neutral point, one of two ways, introduces an additional voltage source that changes the conditions of the earth fault current and makes it easier to detect. This is particularly important when considering the work of fault current passage indicators. In the article also a new criterion of operation of this type of equipment, based on the estimation of faulty line admittance is proposed. In this paper theoretical analysis of described issues and results of laboratory tests are presented.

During the summer of 2015 the transmission system operator in Poland was forced to introduce limitations on electricity consumption to important industrial and commercial customers. In absence of sufficient generation reserve in power system this paper undertakes an analysis of the implementation of demand response program based on critical peak pricing for residential customers in a research of the resource that can prevent such shortages and resulting energy price increases. Making use of standard load profiles for customer group under analysis the critical price levels and the price discounts for program participants were designed allowing for the prospective efficient recruitment of program participants. In this way the demand response resource able to offer the important load reduction level comparing to the normal hourly load of participating customer group could be created in a manner financially neutral for the tariff system in force.

The detection and isolation of short circuits within the MV networks can be improved by the installation of disconnectors together with short-circuit flow passage indicators (FPI) inside the network. The proposed further improvements of FPI operation based on the change of operating criterion to the admittance one and the installation of zero-sequence resistive current forcing system (AWSCz). The operation of such system is analyzed considering the influence of high transition resistances at the place of fault, errors generated within the zero-sequence current measurement systems as well as the poor setting value divisibility of FPI. The proposed decision making system, placed in HV/MV substation, analyses the information obtained from substation measuring systems and from distributed earth fault FPI sensors to issue the proper decision which sectionalizing disconnectors should be open to isolate the faulted line section.

In this paper the effectiveness of demand-side management using zonal tariffs for households is analysed on the case of tariff offer proposed to customers in north-western Poland with the aim to widen the use of electricity for heating purposes. The price elasticity of customers settled according to two zonal tariff was determined using standard load profile of customers published by regional distribution network operator. The costs associated with the applied mean of demand side control were identified and the tariff effects assessment were made taking into account the benefits reached by energy supplier and network operators forming together the considered tariff offer. The analysis presented enabled to formulate some recommendations concerning TOU residential tariff restructuring to improve its feasibility and to create possible prospective income in result of peak load reduction.

The means of increasing the impact of time of use tariffs to reduce peak load in the power system caused by household consumers were examined. The introduced concept of TOU tariff elasticity for shifting the demand allowed the comparison of such tariffs offered in Poland by the biggest power sale companies. The estimate of the needed DSR volume to support the safe balancing of the Polish power system was based on the example of the year 2012 for the hours with the highest balancing market prices. To create a share in such DSR resource the implementation of the demand side program with the critical peak rate was proposed for household customers of one of the largest electric energy suppliers in Poland. Basing on the concept of tariff elasticity the possible effects of such a program were presented and the financial risks associated with its implementation were shortly discussed.

In this paper the modernisation of two coal boiler plants for district heating in Szamotuły near Poznań is described. This involved the first joint Polish-Dutch venture aiming at the protection of the natural environment and the efficient production of electric and heat energy. Energetyka Poznańska SA, represented by COGEN, a subsidiary acting on its behalf, the Management of the City and Commune of Szamotuly and Essent Duurzaam, a Dutch company, jointly adhered to this pilot programme of modernization of local coal boiler houses. Financial support was granted by SENTER, the Dutch government agency, in the framework of a JOINT-IMPLEMENTATION programme for the purpose of the global limitation of greenhouse gas emission.

Recent experience in the exploitation of Polish medium-voltage power networks shows that prevailing method used to determine distribution line earth faults, based on directional criteria, is often unreliable and poorly effective. This paper describes how current earth fault detection automation proves to be particularly ineffective during high resistance or arcing in the vicinity of the earth fault.

Evaluation of activity efficiency of regional power distribution units is nowadays one of the most important management tasks faced by a power distribution company. Regional power distribution units are responsible for performing basic functions of a distribution system operator as well as for correct spending of operational funds for efficient performance of these functions. One of the ways of approaching the above mentioned problem of funds allocation is the application of operational cost benchmarking methods. This approach was recently investigated and reported in numerous studies. Moreover, a regulatory practice for allowable revenue estimation was developed using various benchmarking models of distribution company operational expenditure (OPEX). The above mentioned methodology of operational cost allocation is applied in the presented paper to regional power distribution units of Enea S.A. This company was created in the beginning of 2003 in result of a merging process of 5 smaller companies situated in the north-west of Poland. The biggest company before merging included 10 basic regional distribution units. After consolidation this number increased to 32. The necessity to separate the distribution system operator functions from sales activity (resulting from 2003/54/EC directive) requires unification of the organization structure containing such units. The new structure is facing the budget allocation problem which implies the need for performing the benchmarking study. The aim of such a study is to develop a budget formation support system. It was undertaken by Power Distribution Department of Enea S.A. in cooperation with Computing Science Institute of the Poznan University of Technology.

The quality of electric energy depends not only on aspects concerning its generation, but also on its use, distribution and delivery. Each of the mentioned areas has a significant influence on power quality and as well on customers' satisfaction. It is obvious, that expectations of different users regarding the power quality are different and depend on requirements of equipment used by them. Usually bad quality of the delivered electric energy cause problems connected with equipment malfunctions or difficulties with supply voltage variations.