In connection with the reconstruction of equipment on the electric stations appears necessity of permanent calculation short circuit currents. In a number of cases calculation schemes are difficult enough and there is a necessity of automation of process of calculation for them currents of KZ. The purpose of work is perfection the software department "Electrical stations" associated with the calculation of short circuit currents.

Calculation of currents of KZ for the schemes of electric connections with dif-ferent classes of tension(to and higher 1 kV) on variable and on a direct current on a single computer technology with the use of matrix methods of nodal poten-tials

Modernization of methods and algorithms of the programs of calculation short circuit currents of KZ with the purpose of increase of their functional possibilities and reliability of calculations.

Subject matter are the software products having the opened algorithm, whose implementation is made in the automation package MathCad mathematical calculations

Methods and algorithms of calculating short circuit currents in electrical schemes alternating and permanent current.

The program "Astra"
Program "Astra" was developed at the Department of Electric Power Stations "Antonenko Georgi Vladimirovich in 1991. Intended for
1 calculating short circuit currents;
2 calculation of modes of motor load:
• automatic starting of pumping jacks
• launches
• group launches.
"Astra" is used in the design institute "YuzhNIIgiprogaz" since 1991.

National University "Lviv Polytechnic", Dept. ECM
Interactive Automated complex DAKAR-2002 - a NEW LEVEL of INFOR-MATIVE PROVIDING of the electroenergy systems
"Скрипник А.И., Коновал В.С., 2008
"Skripnik AI, Konoval VS, 2008
Interactive automated complex DAKAR-2002 was developed based on the Win-dows NT operating system and is designed to calculate and analyze the steady-state regimes and transients of electric power systems. The structure of the complex information is information database and software work with it.
Variety of calculation tasks which solves the dynamic model of the EEC, creates certain difficulties in forming the structure of data. All information is given and stored as parameters of physical equipment. To implement specific types of calculations necessary to create a scheme of calculation used by the respective modeled modules.
In the vast majority of the regime calculations are carried out on electric power systems with a fairly permanent structure, and almost the same list of basic equipment. Most operations are performed to change some parameters of the equipment, switching, changing the coefficients of transformation of transformers, regulators setpoints, etc. Given this, all basic information is divided into a constant topology and variable (operational). Separately chosen information at an ancillaries equipment (parameters of different regulators, automation, parameters of lines with a crown etc.), used the separate calculation modules comparatively rarely.
The basis of the concept of data model lie two data description:
• it is physical definition of data - determines how information is organized in databases from point of programmer,that is, as formed and operate various tables of models of data;
• it is definition of data of user - sets, as information appear an user for processing.
At the physical level, all data is organized in the form of two-dimensional tables.
Every object, formed plenty of elements with identical attributes, determines an own tables.
Such principles are fixed in basis of construction of model of data:
• any object, except for information, saves methods and properties of their treatments. Initial data for models for forming are the parameters of the physical equipment;
• all objects (tables) in a certain way are identified and accessible from any program
• lack of redundancy or dual-input single information. Replacement of any data should be carried out only in one place
• to facilitate the work with data, they are divided into operational, topological, equipment and reference books.
Software allows to decide the followings tasks:
• creation of graphic chart of network and interconnect schemes of substations with to display on them the results of calculation; ;
• calculation and analysis of steady regimes;
• study of static and dynamic stability;
• analysis of long-term transients;
• analysis of asymmetric, incomplete-modes and calculation of short circuit currents.
To provide for interaction with other complex computational program provides import and export information about the scheme and an established regime in the most common data formats, in particular, of the Centre in CDA format and the format of UCTE DEF.
Asymmetric and incomplete-modes are modeled are on the method of symmetrical coordinates. Implemented multiple asymmetry of three types: transverse asymmetry and the longitudinal asymmetry (nepovnofaznist) and asymmetry (nepovnofaznist) Shunt reactors.
Maintaining the balance. During ekvivalentuvannya maintain a balance of active power regime scheme. Added the equivalent branches between the nodes landfall. Conclusions:
1. Today the software package DAKAR-2002 is a powerful complex of Ukraine to solve many problems of research and analysis of various processes and modes of operation of modern power systems.
2. Offered in Dakar-2002 concept of data model has allowed to rise to and new level of information support of electric power in Ukraine. [4] .

The programmatic complex ENERGYCS for designing power systems Ivanovo State Power University
The model, which is used to calculate the short circuit current, satisfies the most stringent requirements for the calculations to select the settings of relay protection. Currents of branches are brought to its nominal voltage. This takes into account the exact values of the coefficients of transformation of transformers and change in resistances of transformers winding when switching branches RPN and MSDSCalculation of the nodal voltages of a short circuit is produced by the method of Gauss, on tensions of knots are calculated currents in branches. For a calculation the emf at the initial moment of short circuit for the system, for generators, for synchronous and asynchronous motors are used in the program voltage in the steady state preceding the emergence of a short circuit, - the results of the calculation of the steady mode, taking into account of voltage regulators and the mode of active and reactive power. Actually, a complete calculation of the steady mode is produced for every calculation of currents of short circuit. The module of ENERGYCS TKZ is unconnected with the module of ENERGYCS UR and can be used quite independently. To obtain comparable results can turn on the program, in which the emf is calculated at nominal parameters - the results are consistent with obtained by other means (eg, manually or using other programs). However thus possible to get the overpriced or understated values of currents of short circuit. For today a programmatic complex ENERGYCS allows to decide the followings tasks within the framework of calculations of currents of short circuit:
• a calculation of initial values of currents of three-phase short circuits is in difficultly reserved networks;
• calculation of initial values of currents of single-phase to earth short circuit;
• calculation of initial values of currents of diphasic on earth short circuits;
• calculation of initial values of currents of diphasic without earth short circuits;
• calculation of currents in the cables of lines at short circuits on earth and estimation of their thermal firmness;
• calculation of capacitive currents of single-phase earth fault in networks with isolated neutral;
• calculation of shock of short circuit currents at three-phase the short circuit in accordance with GOST 27514-87 [4];
• calculation of values periodic and aperiodic constituents of current of KZ at a given time;
• calculation of virtual value of current of three-phase KZ in the moment of disconnecting;
• calculation of integral of Joule in the moment of disconnecting, and also thermally equivalent and equivalent onesecond currents of short circuit;
• construction of vector diagrams of currents and voltages for arbitrary nodes and arbitrary branches network.
The program allows for a given point of the short circuit to consider the distribution of currents and voltages in all branches of the circuit, bring in the tables or on the schemes values of the maximum values of short circuit currents the phases, the currents in all phases of currents on symmetrical components, as well as to construct a vector diagram of currents for the chosen branch and vector diagram of voltages for the selected node.
During the calculation of asymmetrical short circuit at a given point the chart of a zero sequence is formed automatically. Forming of scheme is carried out on is based
• topological structure of a design scheme;
• information about the scheme groups connections the windings of the transformer and its mode of neutral;
• information about mutual influence of VL, passing in general corridors taking into account geometry of pendant of wires on support;
• information on the availability and method of grounding, grozozaschitnykh wire.
The results of calculations can be shown out directly on a chart or in tables. Final documents can be formed with the use of MS Word on the basis of the beforehand provided templates.
The program provides several options for presenting the results of the calculation of TDF(токов кз)
The first version determines the node, in which should consider the possibility of short circuit. get as a result, currents is a short-circuit currents in the site for three-phase, two-phase, one-and two-phase short circuit on the ground, and the importance of surge current and constant decay time of the free component. For every type of KZ distributing of currents is determined in all branches, and for all knots are remaining tensions (Fig 7.1).

In the second variant the program executes the calculations of TKZ for the great number of the indicated a nodal points of the scheme. In this case on a scheme can be shown out only values of currents in the selected knots, and in a table are currents in all selected knots and joinings to them branches. Except for the initial values of currents of KZ for all types of damages, in the table displays the regime parameters for the evaluation of the thermal and dynamic actions of the three-phase short circuit currents, ie for each branch adjacent to the node to the CP displays the results of the calculation of surge current, the Joule integral, thermally equivalent and equivalent odnosecond currents ( Fig 7.2).

For the calculations of currents of KZ with the purpose of determination of setpoints of relay protection a foreseen the calculation of currents,flowing through a given branch of a short circuit in a given set of nodes. The example of table is resulted on a fig 7.3.

The calculations of currents of earth-fault for networks with isolated neutral are produced a topological method in the same module and can be shown out on a chart or in tables along with the results of calculations of TKZ.
The example of calculation of TKZ for the system of own needs of thermal elektrostan-cii is rotined on a fig 7.4.

At power plants and large power systems, power industry design schemes can achieve significant size and have a complex topology. Figure 8.1 shows the electrical circuit supplying one of the mines of Donbass.

where Uu - vector of nodal voltages, Yu - a square matrix of nodal conductivities, Iu - vector of nodal currents.
Matrix Yu at the following

where P - the matrix of connections of nodes with branches , diagonal matrix of conductances of branches, Zv - vector resistance, branches, which must be obtained from the input matrix V.
Vector Iu from of EMF can be found as

where Ev - vector EMF branches.
The matrix of connections R in the case of numerical numbering of nodes, her can be created using the following user function FormP

In the case of symbolic indexing of nodes in the above functions FormP will be changed conditional statements on the followings:

In the operators (5) is used function Poz for to determine the node number site for its symbolic notation in the vector Uzl.

Vector of Uzl in the case of one level of tension of the nodes of a design scheme, for example in the schemes of alternating and permanent current by tension less than 1 kV, formed automatically from these denotations of knots of matrix of description of branches V by dint of the next function of Formuzl