"Modelling of transients on electric  power plant in the time of  disturbances  in electric systems"

INTRODUCTION

The rapid development of computers contributed to the development of new methods of mathematical modeling and calculation of steady and transient modes of operation of electric power systems. This allowed a new approach to many issues of design and operation of various facilities. In general, the processes in an object can be described by analytical dependencies that are based on a system of nonlinear algebraic and differential equations. In this case, if there is information about the system parameters and topological relationships between its elements then, a mathematical model of the object can be created which shows the analysis of its behavior in various modes.

Relevance of the topic.

Currently, the aim is  to develop a mathematical model of the power station, which allows to analyze the transient processes arising from single-and multiphase short-circuit on the outgoing transmission lines, on the  bus bars, on the  transformers and their outputs, by phase failure, as well as on incomplete switching of  breakers of  high voltage. This information is used to optimize the design and management of electrical facilities. Currently, there are of this type of model, though they allow us to calculate the effective values ​​of currents and voltages, whereas for the relay protection and automation, as well as for the selection of equipment requires knowledge of the instantaneous values ​​of the parameters of the above modes.
The purpose of
The aim is to create a mathematical model of the main circuit of a power station based on differential equations. To create a universal mathematical model requires a complete mathematical description of all the main elements of the scheme.

Aim of the research :

- The choice of mathematical models and parameters of the basic elements of power plants;
- Development of the basic algorithm for calculating the steady-state and transient;
- Analysis of the behavior of elements of main circuit of the power station during starting and offing  of  symmetrical and asymmetrical short circuit of varying duration.
- To use in the model, the node voltage method for determination of voltage in the multi-node systems.

Research methods.

Theoretically, the research is  based on the main principle of the theory of electricity and modes of operation of power plants and systems, theory of stationary and transient of  ac machines, numerical analysis methods and computer technology in the electrical system.

Scientific novelty of the results

In recent years, due to the rapid development of computer technology, as well as due to increased demand for precision modeling in the design and creation of highly reliable power supply systems and other reliable installations  with large induction motors and synchronous motors, has a great increased interest in models of multimachine power systems. Urgently there is need for  the establishment of a universal model, which allows to investigate both short and long processes in the group of machines. The mathematical model was created with MathCAD 2001.

The practical value

The mathematical model allows us to analyze the transient, to sketch the characteristics for induction motors, to analyze the behavior of synchronous turbine generators in the disturbance (asynchronous course, non-synchronous starting, etc.), to deduce the dependence of the the speed of  engines and generators from time to time, analyze the processes of running-out - self-starting motors and also have wide application not only in power stations, but in any enterprise that uses a large number of induction motors, non-stop work which should provide trouble-free production, which is especially important for large enterprises.
CONTENTS


 


Figure 3 - Animation of the equivalent scheme of the given electrical system. (Animation is made up of : 4 frames, 7 cycles, and 136 kb)

Calculation of transient during short-circuit in one branch of the network


Asynchronous mode power

Asynchronous mode occurs when there is a loss of excitation of  generators due to damage to the excitation system or faulty control boards, as well as a roll of the machine out of synchronism as a result of short circuits in the network. Modeling asynchronous mode in MathCad is produced by changing the frequency of one of the generators, for example 3% or 5%.





б) Frequency difference of  one the generators is 5%





CONCLUSION

In the result of research work, we have been able to collect and studied the materials on issues related to the topic of master's work. We analyzed the transient processes arising in single-and multi-phase short circuits on the outgoing transmission lines, the bus bars, transformers and their outputs. To create with guidelines for improved the reliability of modern thermal power plant requires a deep study of transients in power plants, which in turn requires the development of methods for determining the equivalent circuits and mathematical models.

REFERENCES

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