Ivo Palu

Harmonic levels of domestic and electrical vehicle loads in residential distribution networks

Purpose of the present paper is to provide the results of the study performed in order to assess current distortion of domestic and electrical vehicle (EV) loads and corresponding voltage distortion in the residential distribution networks. For the study harmonic current amplitudes and phase angles of different home appliances were measured and afterwards the corresponding models were composed in DIgSILENT Power Factory. The focus of the study was to analyse the characteristics of the residential distribution network with and without the EV charging. The results of the study showed an extensive harmonic distortion in residential load current and considerable voltage distortion at the substations busbar. The results presented in this paper are especially important when dispersed generation (DG) and EVs are going to be connected in bulk into the distribution networks.

Residential load harmonics in distribution grid

Purpose of the present paper is to provide the results of the study performed in order to assess current distortion of domestic loads and corresponding voltage distortion in the residential distribution networks. For the study harmonic current amplitudes and phase angles of different home appliances were measured and afterwards the corresponding models were composed in DIgSILENT Power Factory. The focus of the study was to analyse the characteristics of the residential distribution network with different amounts of real nonlinear loads. The results of the study showed an extensive harmonic distortion in residential load current and considerable voltage distortion at the substations busbar. The results presented in this paper are especially important when dispersed generation (DG) and electrical vehicles (EV) are going to be connected in bulk into the distribution networks.

Electricity consumption analysis and power quality monitoring in commercial buildings

The results of the analysis of the electricity consumption and power quality indicators in two office buildings are presented. It comprises electricity consumption and power quality during work days and weekends. The consumption data analysed is from a one year period and the power quality analysis is based on a one week measuring period. The aim of this analysis is to determine the current situation in these buildings in order to study the possibilities and limitations to implement different energy efficiency measures. In addition to the energy efficiency point of view, the problem is also addressed together with the power quality aspects.

Preventing Bird Streamer Outages Using Alternative Tower Configurations

This paper presents methods for mitigating the destructive impact of bird excrement contamination on 110 kV power lines. In addition to the typical retrofitting techniques (cover-ups and perch management), focus is mainly on reconfiguration and alternative tower designs aimed at eliminating streamer outages. Advantages and disadvantages of existing designs are assessed and novel ideas are presented by the authors.

Verification of wind parks and their integration into small-interconnected power system

Continuously increasing percentage of wind power that is integrated into power system is causing additional challenges to system operators, especially in the case of small-interconnected power system. Estonian power system is an excellent example of that situation due to its configuration and load characteristics. Therefore, adequate requirement for connection of wind parks are needed. In this paper, the present situation of wind power development in Estonia and probable future scenarios and their influence to power system operation and development are discussed and analyzed. Moreover, comprehensive clarification of requirements (e.g. P, Q and V regulation, fault-ride-through and power quality criterions etc.) and legislation for connection of wind parks, considering system security and operational aspects, are discussed and compared with different requirements specified by other system operators. An example of integration of wind park into Estonian power system is presented. Adequate requirements will assure permissible operation of the Estonian power system in steady-state and in different contingencies.

Assessing demand side flexibility with renewable energy resources

In the perspective of network operators, demand response (DR) is a form of shaping of the overall consumption in the system by peak clipping and shifting. Bearing the necessity and importance and the role of DR in the overall system in focus, the objective of the paper is to extend an analysis on the flexibility of the demand. The potential and the corresponding cost for demand flexibility of different levels in private households is determined from literature. Following that, consumption in a residential house in Nordic Europe climatic conditions was measured. In order to identify the patterns and categorize the consumption, a clustering algorithm is implemented on time-series load demand based on the trend using Wards agglomerative hierarchical clustering to formulate classifications. Using the classifications, a model was simulated in GAMS based Balmorel platform, which chooses optimal operation scheme for categorised loads. Two distinct models were created. One as in grid integrated, where market price acts as an incentive and second as islanded mode, where the resource availability is the motivation. The resulting consumption profiles and the decision making economic stand-point of flexibility offered by means of DR are discussed. The dendogram of the associated individual devices in the consumption pattern confirms that the weekend and weekday pattern of consumption are of different construct. However, same devices provide different flexibility whether operating on workdays or weekends. Modelling results indicate an overall increase in the efficiency of energy consumption with a demand-shifting possibility. In analysis, no attention was paid to type nor price of devices that allow to control individual appliances.

Experiences with dynamic PMU compliance testing using standard relay testing equipment

This paper presents the results of dynamic compliance testing of phasor measurement units (PMUs) from three different vendors in a laboratory environment. Testing is performed by providing three phase voltage and current injections to the VT and CT inputs of the PMUs through Freja-300 stand-alone protection relay test set. Testing is performed according to the standard “IEEE C37.242-2013 - IEEE Guide for Synchronization, Calibration, Testing, and Installation of Phasor Measurement Units (PMUs) for Power System Protection and Control”. The paper discusses the test setup, testing process, calculation of performance evaluation parameters and overall test results of this project.

Impulse characteristics of 24 kV overhead line pin insulators

One of the main characteristics of the distribution grid is the reliability of medium voltage overhead lines which can be improved by appropriate insulation coordination. This paper assesses common insulator types in Estonia. Old glass pin insulators and newly installed porcelain pin insulators were tested against different lightning overvoltages (impulse flashovers) in order to determine their volt-time characteristics. Test results show convincingly that the new porcelain pin insulators can be easily physically broken when stressed by lightning impulses. This can lead to the numeral increase of outages in medium voltage overhead lines in the distribution grid.

Dimensioning of electricity storage according to small wind turbine power generation and household load patterns

This paper analyzes wind speed data measured in the Tallinn-Harku Aerological Station (Estonia). Dimensioning of a wind turbine and electricity storage for a typical household is discussed. The final part describes electricity storage dimensioning based on a combination of Nord Pool Spot (NPS) prices and grid connected household wind turbine generation.

Analysis of electricity meters under distorted load conditions

Due to the rapid growth of non-linear loads in power systems in recent decades, harmonic pollution is becoming more and more serious. Energy measurement devices are commonly designed for working at sine wave. In this paper the results of an analysis on different electricity meters used in distribution network under different load conditions are presented. Study shows that error of energy meters reading depends on the type of the meter, harmonic distortion, reactive energy and direction of reactive power. Measured errors were higher than 6% under some conditions.