Alexander Novitskiy

Interaction of multi-circuit overhead transmission lines of different voltages located on the same pylons

The sharing of the routes for transmission overhead lines operated at different voltages and frequencies is a popular technical solution. Often the circuits of extra high and high voltage lines are installed on the same towers. This causes the electromagnetic interaction between corresponding power transmission systems. Earth fault currents and neutral point displacement voltages can be increased in electrical networks with resonant earthed neutral due to the electromagnetic influence from parallel located power transmission lines. Theoretical mechanism of the interaction, some practical examples based on investigations in German transmission networks and possible measures for the reduction of negative influences will be considered in the offered paper.

Identification of the dominant harmonic source in the LV network on the base of anomalous power flows considerations

The localization of the dominant harmonic distortion source in the electrical network is one of the practical tasks in the consideration of the power quality in electric power systems. The conventional methods of the estimating of the impacts of the utility and the customer to the harmonic distortion at the network node are the harmonic power flow analysis as well as the correlation analysis of the harmonic voltage and current phasors. The practical use of both methods is discussed below by means of the example of the identification of the dominant harmonic source in the LV supply feeder of an industrial consumer. Based on the analysis carried out it is shown that the direction of harmonic active power flows is a more common and reliable criterion in comparison with the correlation analysis for the identification of dominant harmonic sources in electric power systems.

Analysis and prediction of power and energy losses in distribution networks

A new approach for a correct estimation of power and energy losses in urban distribution networks is described in the paper. The method is based on a row of national directives for power and energy loss analysis as well as on authorpsilas investigation. The method allows the calculation of load-dependent (current-dependent) and load-independent (voltage-dependent) power and energy losses in an urban network and their separation between power nets of different voltage levels. On the base of the elaborated method it is possible to analyse and to predict the power loss profiles over time (for instance annual profiles) depending on the power delivered to the urban distribution network under study.

DC components in the AC networks containing AC/DC hybrid transmission lines

The use of hybrid AC/DC overhead transmission lines can help to increase the transport capacity of power lines. But the spatial proximity of DC and AC power circuits in the same right of way leads to the presence of additional DC components in the currents and voltages of the AC line. One of known effects caused by the presence of DC components in the AC networks is the DC saturation of transformers connected to the AC lines. The performance of power and instrument transformers under the influence of DC components may be altered. The influence of DC components on voltage and current transformers for a new planned AC/DC hybrid transmission line is considered in the paper. It is shown that the standard instrument transformers used in the AC power circuits are not significantly affected by the DC components caused by the operation of the DC line. The method for the estimation of the influence of the DC line operation on the instrument transformers in the AC power line is considered in the paper.

Constraints on the use of local compensation for the correction of neutral voltage displacement caused by the influence of nearby power lines

The use of the same right of way for several power lines is a popular technical solution nowadays. The drawback of this solution is the growth of interferences between nearby power circuits of transmission lines, especially in the case of multi-circuit lines positioned on the same pylons. Neutral voltage displacement in the network with resonant earthing caused by the influence of nearby power line is one of known effects of the interaction. The efficiency of the use of local compensation of neutral voltage displacement in the 110 kV resonant earthed network containing the 21 km segment of combined 380/110 kV overhead line is studied in the offered paper. It is shown that the voltage displacement influenced by the combined overhead line can be propagated over full 110 kV network containing several thousand km of overhead transmission lines. Taking into account the earth fault protection requirements it is shown that local compensation devices are not always capable to reduce the neutral voltage displacement down to the permissible level. Possible practical measures for the reduction of the influenced neutral voltage displacement are discussed in the paper.

Interactions by the use of common pylons for EHV transmission lines and electric railroad catenary system

The growth of the energy production from renewable sources causes the necessity of the transportation of significant power volumes over long distances. Due to the difficulties finding new corridors for the extra high voltage (EHV) transmission lines the use of the same right of ways (ROW) with other infrastructure objects like highways or railroads becomes more and more popular for the construction of new power lines. The electromagnetic interactions by the use of common pylons for EHV transmission lines and electric AC railroad catenary system over distance of 125 km are studied in the offered paper. Typical features of the interactions caused by the location of EHV AC and HVDC OHL in electric railroad ROW are considered in the paper. Different variants of the design of power lines are compared with respect to the produced interferences. Interaction effects and influencing factors are discussed in the offered paper.

Impact of distributed generation facilities on an urban network

Many of modern distributed generation plants are based on photovoltaic cells using power electronic units for energy transmission into the electrical network. This increases the emission of high-frequency currents into the network and affects the operation of power line communication devices and energy meters. A real LV network in Germany was investigated by the authors with the purpose to estimate the actual situation in the network with respect to high-frequency distortion and to characterize the possible impact of the presented distributed generation facilities on the network operation.

Some aspects of steady state simulations of AC/DC hybrid transmission lines

The use of hybrid AC/DC overhead transmission lines is an option to increase the power line transport capacities and to reduce the width of the right-of-ways. On the other side the proximity of power circuits of different rated voltages and frequencies on the same tower intensifies interferences between power circuits. One of undesirable effects of the proximity of AC and DC power circuits is possible penetration of DC components into AC power circuits. DC components can saturate the magnet systems of transformers and disturb the network operation. In the paper is shown that the neglection of some aspects of the transmission line steady state modeling can cause erroneous estimation of the DC components in the simulated AC power circuits of AC/DC hybrid transmission lines.

Flicker Propagation in Power Networks with Hybrid and Parallel Overhead Transmission Lines

The growth of the energy generation from renewable sources necessitates the construction of new overhead transmission lines for the energy transport over long distances. The use of common right of ways (ROW) for several overhead lines becomes more and more popular. The construction of combined AC/DC hybrid power lines is one of possible solutions. The spatial proximity of several power lines in the common ROW intensifies electromagnetic interferences between the lines. These interferences can cause deteriorations of power quality parameters in power grids containing parts with common ROWs. The influence of electromagnetic interferences on the flicker propagation in power networks with hybrid and parallel overhead transmission lines is considered in the offered paper.

Influence of 380 kV AC systems on the maintenance conditions of the HVDC system in a hybrid AC/DC overhead line

The growth of the energy production from renewable sources causes the necessity of the transportation of significant power volumes over long distances. Parallel operation of a bipolar high-voltage direct-current (HVDC) power transmission system with the 380-kV alternating-current (AC) power transmission systems on the same line route can be seen as one of the solutions for the increasing of the power transmission capability. One of possible realizations of this solution is the use of so-called hybrid AC/DC overhead transmission lines containing EHV AC and HVDC power circuits on the same pylons. Consequences of this are various AC/DC interaction phenomena. The paper deals with the AC impact on the DC power circuits switched off for maintenance purposes.