Ing. Radek Hanuš, Ph.D.

The contribution deals with probabilistic approach to distribution system analysis. This method is suitable for the development and planning of the system with decentralized renewables sources and electro mobility etc. The transition to a probabilistic approach can lead to higher quality of analysis and increase the predictive ability of power flow computation and provides reliable information for decision-making processes.

This paper shows some opportunities offered by new approaches to processing planning and distribution network management data. The increasing amount of phenomena that are difficult to predict (e.g. decentralized sources, electromobility etc.) decreases the informative value of currently used calculation methods. These methods also require accurate input data. Using methods from the probability theory allows us to describe the reality more accurately in the conditions with increased amounts of uncertainty.

The paper shows the possibilities of new approaches to the calculations for planning and management of the distribution grid. Increasing amount of less predictable phenomena (such as decentralized sources, electric mobility, etc.) reduces the explicitness of existing computational methods which require precise input data. The use of advanced methods of a manage ment theory allows obtaining a more accurate description of reality in terms of increased uncertainty.

Paper deals with the process of implementation of AMM in the distribution network. Emphasis is placed on the use of the most synergistic effects for building distribution system Smart Grid. Requirements are summarized distribution of the AMM, the theoretical possibility of AMM and intersection of these requirements and options in real projects undertaken now PREdistribuce.

In case of the ground fault, the earth-wire is use as the return ground path of the fault current. In past it was automatically assumed that, most of the current flowing backward by ground path during the ground fault is flowing through ground, which was more conductive than earthwire (Fe 50, Fe 70). Nowadays more conductive earth-wires AlFe are installed and hence have hanged the distribution of current in the return ground path. Due to the increase of the share of return ground current through earth-wire to that of earth, dramatically changes the shape of magnetic field of the faulted path. This has impact on the parameters of the equipment and losses in the transmission lines. This paper is trying to cover the main interdependency between individual values.

The article contain analysis of the negative specific influences, which have great influence for reliable distance protection. Specifically, some negative influences are: Impedance non-symmetry, which is caused by inconsistent transposition conductors, operation of parallel lines, influence of fault resistance.

Series connection of n-port circuits can be easily solved using hybrid parameters of the circuits and corresponding H-matrices. Homogenous transmission lines can be then read as series connection of chosen number of parts of the same H-matrix description. If a fault (or illegal current consumption) occurs, the resulting H- matrix is the product of n-th power of H-matrix describing a regular section, H matrix describing the fault and m-th power of H-matrix describing a regular section. Because it is possible to know the phasors of the currents and voltages at the ends of the line and the fact that matrix product is not commutative, developed optimization methods allow to determine the position and character of the fault.

The article show new princip of the fault localization of the cable network 110kV. The new method of the fault localization operate with the H parameters of protected equipment. This method has high precision.

The earth-wire forms the common part of so called return ground path of the fault current in case of ground fault. Early due to the low conductivity of earth-wires (Fe 50, Fe 70) it was automatically assumed that most of the current flowing backward by ground path during the ground fault will flow through the ground, which was more conductive than earth-wire. With installation of more conductive earth-wires AlFe it has changed the distribution of current in the return ground path. The cardinal increase of the share of return ground current through earth-wire to the prejudice of earth dramatically changes the shape of magnetic field of the faulted path. This has impact on the parameters of the equipment and losses in the distribution lines. The paper has tried to look on the interdependency between individual values.

Provided that electrical power system doesn't have enough reactive power for securing stability of the voltage profile then there is a chance of voltage collapse. The paper adverts to special methods, which are able to identify instability in the electrical network. The development of analytic tools enables effectively detection of symptoms for the hazardous condition of operation. The emphasis is laid chiefly on the method of predicting voltage collapse.

The paper deals with the application of the description of a line by using H parameters. Main stress is laid on problems connected with the localization of failures in 110 kV cable networks. The method of describing the line by means of H parameters enables us to respect any existing nonhomogeneities. The influence of grounding the sheath of the cable along its route is mainly examined. The accuracy of localizing the failure with a standard locator and with that based on the description of the protected equipment by using H parameters is compared. The contribution of this method to localizing concrete short-circuits on 110 kV cables in the network of PRE, a. s. is also discussed.

Series connection of n-port circuits can be easily solved using hybrid parameters of the circuits and corresponding H-matrices. Homogenous transmission lines can be then read as serious connection of chosen number of parts of the same H-matrix description. If a fault (or illegal current consumption) occurs, the resulting H- matrix is the product of n-th power of H-matrix describing a regular section, H matrix describing the fault and m-th power of H-matrix describing a regular section. Because it is possible to know the phasors of the currents and voltages at the ends of the line and the fact that matrix product is not commutative, developed optimization methods allow to determine the position and character of the fault.

Series connection of n-port circuits can be easily solved using hybrid parameters of the circuits and corresponding H-matrices. Homogenous transmission lines can be then read as series connection of chosen number of parts of the same H-matrix description. If a fault (or illegal current consumption) occurs, the resulting H-matrix is the product of n-th power of H-matrix describing a regular section, H-matrix describing the fault and m-th power of H-matrix describing a regular section. Because it is possible to know the phasors of the currents and voltages at the ends of the line and the fact that matrix product is not commutative, developed optimization methods allow to determine the position and character of the fault.

The chapter describes distance protection systems on high voltage distribution level.

The paper focuses on Electric Arc Furnace Busbare protection systems. Key differences between conventional systems and systems with EAF are explained. Protection possibilities are shown on case study containing complex system with both the furnace and connected transformer.