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In the design and operation of the power industry, large-scale factories and mines, whether in the design of the need to select electrical equipment such as circuit breakers, or in the operation of the power system to carry out the relay protection setting calculation, the short-circuit current must be carried out in advance Calculation, verification of electrical power and thermal stability of electrical equipment and requirements for the protection settings of individual electrical equipment. If it is calculated by hand, it is time-consuming and labor-intensive, especially for the ring network system, and it is easy to cause errors to be calculated by computer, which can greatly reduce the workload and improve the calculation accuracy. At present, most departments use the short-circuit current calculation software of DOS operating system. Because it has no graphical interface, the node number can not be automatically followed, and the operation is more complicated when modifying the network, so that the operator is not willing to use it to a certain extent. On the basis of limiting the promotion of the software and the application of the DOS version of the short-circuit current calculation software applied in several power industry bureaus, the visualized short-circuit current calculation under the Window 98/2000 platform was re-developed with VisualBasic6 language. The software, including system connection diagram drawing and short-circuit current calculation, can select the icons of each electrical equipment provided by the software, quickly draw a one-line diagram of the system connection line with the mouse, and then directly input the nameplate parameters of the equipment from the diagram. The software will automatically calculate its corresponding impedance value and convert it into the standard value. When calculating the short-circuit current, the user can use the mouse to randomly point out the location of the short-circuit fault on the system connection diagram, and select the fault type, the software can Automatic calculation, the voltage and current calculation results of each sequence are marked with the famous value in the knot On, and can be printed out in the list. When the system operation mode changes, it can be modified by the knot diagram drawing software. Because the node number is automatically tracked, it is convenient to re-run the short-circuit current calculation of the new operation mode. 2 Software structure visualizes the short-circuit current. The calculation software is divided into two interrelated and relatively independent parts, namely the knot diagram drawing and the short-circuit current calculation, and the two are connected through the network data. The user first applies the knot diagram drawing software, draws the knot diagram with the mouse, and saves the knot diagram and the data in the same file format. After inputting the device parameters from the map, the short-circuit current calculation software can be used to call up. The file of the knot diagram has been drawn, and the short-circuit current calculation is performed. 3 Main functions of the software 3.1 Main function of the knot diagram drawing software The following graphic components are provided for the user to select: transmission line, bus, generator, double winding Transformers, three-winding transformer circuit breakers, isolating switches, reactor capacitor loads, T-junctions, Chinese and English symbol marking, component direction arrows, line and busbar length adjustment, etc.
The various graphic components are respectively represented by an icon. When drawing, the user can apply the ruler as coordinates, select the graphic component with the mouse, and click the mouse on the drawing area, and the component appears at the mouse position. In order to make the connection diagram beautiful and reasonable, the user can select the direction arrow icons (up, down, left, and right directions) of the component to be drawn in advance, and then draw the system to draw the system connection diagram, then you can enter each The parameters of the component. The user simply double-clicks the selected component with the mouse, and the corresponding data input window of the component is popped up. Enter the nameplate parameters of the device according to the prompts, such as the generator rated capacity S positive sequence and zero sequence reactance, transformer rated capacity, voltage and The percentage of short-circuit voltage, the cross-section of the transmission line, the length, the geometric distance, and so on. Components that have entered parameters will automatically change color to alert the user.
When drawing, you can use the movement, copy, flip and delete functions of the primitives for quick drawing, and the graphic block operation function can be applied to copy, move and delete the block diagram. The length and direction of the transmission line and busbar on the diagram can be adjusted at will. The voltage level of each device can also be marked on the knot diagram. The voltage level of each device can be selected according to the user's requirements to distinguish the connection method of the transformer winding. Y midpoint grounding can also be marked on the map. After drawing the knot diagram and inputting the parameters, it can be saved in the form of a file to prepare the short-circuit current calculation. 3.2 The main function of the short-circuit calculation software After entering the short-circuit current calculation software, the user first The system connection diagram file that has been drawn is called up, and the voltage levels of the components on the diagram have been separately colored according to user requirements. The user can select one of the following methods to calculate a short circuit at a certain point within 90%; a short circuit at a certain point within 90%; automatically calculate step by step, automatically calculate the three-phase short circuit and two-phase short circuit grounding before all the bus bars are respectively calculated one by one For the three calculation methods, the user should first select the short-circuit point. Just double-click the corresponding position on the graph, and the short-circuit fault type selection window will pop up. The types of faults that can be calculated at present are: In addition, for each type of short-circuit You can also select the short-circuit current calculation at 0 second, 0.2 second or 4 seconds. After the calculation is completed, the sequence currents of each bus line can be selectively marked on the map. The sequence currents of each transmission line are well-known in kilovolts and kiloamperes. The value is marked. If necessary, the knot diagram marked with the calculation result, the sequence voltage of each bus line, and the sequence current list of each line can be printed and archived.
When the operation mode is changed, the following operations can be performed with the mouse on the diagram: the branch opening and closing operation includes the input and cutoff of the generator transformer, the transmission line, and the reactor components, thereby changing the network structure and converting it into the user's needs. System operation mode Transformer neutral point opening and closing operation will cause changes in the zero sequence network, changing the distribution and size of the zero sequence current.
For large-scale factories and mines with a voltage level of 35kV and below, because the line section is small and the wire resistance is large, the impedance of the line should take into account the resistance. The software has function keys that take into account the resistance and do not take into account the resistance calculation, which is chosen by the user.
98/2000 multi-window graphical operating system platform, using VisaualBasic 6 visual programming language and Access database as a development tool, has the advantages of simplicity, easy to use, high development efficiency; full graphics operation, all operations including drawing input parameters, calculation The result output, modify the network, query, print, etc., can be completed with the mouse only, the user is convenient to use; the graphics and the database are bundled together, the graph and the data coexist, the graphics modification and deletion are synchronized with the corresponding data modification and deletion, After deleting the graphic, switch the interface to find the database for deletion; when the fault occurs, the flow direction of each sequence current on the connection diagram can be dynamically displayed, and the distribution of the short-circuit current in the system is visually observed, especially zero. The sequence current flow is related to the wiring of the transformer winding. When the transformer winding is grounded at YA or Y, the different distribution of zero-sequence current can be clearly distinguished. The data management function can be used to find the original of all electrical equipment. Nameplate parameters can also be queried and printed; when added individually or in pieces In the standby time, the node number is automatically tracked and processed without human intervention. When calculating the impedance of each electrical device, the name value and the standard value conversion are executed by the program. The user only needs to input the famous value of the device parameter, and the calculation result will use the named value. Output.
5 Conclusion 1 Shout 4 branch opening and closing and transformer neutral opening and closing are used in the figure ublis and factories and mines to use the future 1 bookmark1 to expand the function to the operating system on the short-circuit current calculation software. It can realize the functions of inputting electrical equipment on the drawing system diagram and performing 0 second, 0.2 second, and 4 second short-circuit current calculation on the graph. Easy to operate and easy to use. And there is a multi-window graphical interface, it can also simulate the short-circuit current calculation after the branch and transformer neutral point on the graph is a kind of calculation and analysis research tool with wide practical value, and has been in Guangdong Province and Parallel mutual inductance and complex faults of double-circuit lines of several power industry bureaus in Shanxi Province, further perfecting this practical software
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