Petr Krejci

The periodical and continual PQ monitoring of selected distribution networks in Czech Republic

In the power company CEZ in the North Moravia Region (the Czech Republic) the monitoring of a number of selected parameters of the quality of electrical energy (harmonics, flicker and unbalance) is being carried out in cooperation with research laboratories of the Faculty of Electrical Engineering and Computer Science, VSB - Technical University of Ostrava. The monitoring is being carried out in a complex manner in 59 feeding points 400 V, always within one week intervals, and at the same time on all voltage levels (HV, MV and LV). In the paper, the results of the complex monitoring during 12 years will be summarized together with the comparison of the changes of parameters after three years. In addition the results of annual continual monitoring for one selected locality on MV level will be presented in the paper. In addition the possibility of utilization of intelligent electrometers for monitoring of some quality parameters will be referred.

Power quality complaints and monitoring of flicker in selected areas of northern Moravia

Electric power is the electrical appliances basic means for their functionality. In case that the electrical energy customer causes problems arise thereby complaints the power quality. In areas with frequent complaints of power quality measurements were made in order to resolve the reported complaints and also in order to investigate the cause of exceeding the compatibility level of power quality.

Long-Term Monitoring of Flicker and Some Other Parameters of Voltage Quality

In 1997 cooperation began between the Faculty of Electrical Engineering and Computer Science and the power company CEZ on a joint project that involved monitoring selected voltage quality parameters. Over the course of several years measurements were carried out at 59 points of the distribution system at a low voltage (LV) level and their power supply nodes at medium voltage (MV) and high voltage (HV) levels, which constituted more than 100 measured points. The measurements continued until 2012 (with a one-year break in 2009) and with a total scope of five cycles of three-year measurements. The last phase of the measurements was focused, inter alia, on the evaluation of 15th and 21st voltage harmonics. From 2013, the cooperation focused again on monitoring flicker in localities with the occurrence of elevated levels of this voltage quality parameter. At these sites, the monitoring of flicker was carried out for two weeks in spring and autumn for a period of three years. The basis for evaluating the quality parameters is the standard EN 50160.

Flicker Caused by Operation of Industrial Technology

There are more and more electrical devices operating in industrial plants which impact negatively on the distribution network. The EN 50160 standard defines the voltage characteristics of electricity supplied by the public distribution system and it is a problem for a distribution network operator when the voltage quality in the distribution network does not comply with the requirements of the EN 50160 standard because of complaints about voltage quality. Such a complaint is justified and the distribution network operator has to pay a penalty and has to remedy the situation. This paper describes a problem of flicker in the medium-voltage distribution grid when the flicker is produced by one customer operating a forging press. The remedies from the side of the distribution network operator and the customer with the aim of reducing the flicker level in the grid are described.

Undefined parameters and two-limit parameters in standard EN 50160 ED. 3

Standard EN 50160 ED. 3 was released in 2011 and despite the fact that this is the third edition of this standard, it still does not limit values for all parameters at all voltage levels. This article examines the various methods of evaluation variables with two levels and then presents some recommendations for amendments undefined parameters vvn network in EN 50160 ED. 3rd.

A power quality evaluating in autonomous system using virtual instrument tool

In recent years, the utilizing of intelligent technology in a classical distribution and transmitting system becomes more and more important in all energy-related topics. The development bring us to the new era of power electrical engineering, to the era of Smart-Grids. These intelligent grids allow us to operate the grid with a specific set of requirements, such as bi-directional power flows, maximal utilization of renewable energy sources using energy storage devices, grid desynchronization and re-synchronization up to individual energy object level - Autonomous systems or more precisely Off-Grid systems. In this case, Off-Grid system can be understood as a basic cell of the entire Smart-Girds. However, it should be noted that in the Off-Grid system operation can occur some disadvantages as well. Based on the authors experience, the disadvantages lies in e.g. rapid changes in power consumption or generation, changes in the short circuit power influenced the protection system as well as the power quality parameters. This paper presents a long-term evaluation of power quality parameters of the real-operated Off-Grid system in VSB - TU Ostrava campus, Czech Republic.

The analysis of the measured data of wind turbines Vestas V90 - 2.0 MW

Electricity and its deteriorating quality is increasingly becoming an important problem for the industry and service companies. A significant increase in the production of energy from renewable sources leads to the need to explore new ways of energy systems. It must be known reliability and responsiveness to changes in the network. Power quality and compliance with their parameters indicates the standard ČSN EN 50160. Renewable power sources are unstable and can they ensure a continuous supply constant power. Therefore a project must be connected and operated in such places the electrical system, which will have negative feedback effects on the characteristics of electricity and at the same time will be in accordance with standard ČSN EN 50160.

Monitoring of power quality parameters in the areas of complaints about the quality of electrical power

Electric power is the electrical appliances basic means for their functionality. In case that the electrical energy customer causes problems arise thereby complaints the power quality. Any complaints on the quality of electricity distribution companies must examine the best measurement at the point of complaint to power quality. In place of the complaint on the quality electric energy measurement is made of selected quality parameters of electricity.