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.

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.

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