National conference on power electronics and power systems 2008: Simulation of transient for power transmission lines

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National conference on power electronics and power systems 2008: Simulation of transient for power transmission lines

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Abstract

Switching operations, faults, lightning surges, and other intended or unintended disturbances cause
temporary high voltages and currents in power transmission lines. The system must withstand this high voltage with a certain probability or its effects must be reduced and limited with protective devices. The simulation of transient phenomena is therefore important for coordination of the insulation as well as the proper design of the protection schemes. Such simulation is also needed to analyze unexpected transient phenomena after their occurrence.. By nature these phenomena are combinations of traveling wave effects on overhead lines and cables, and of oscillations of lumped circuits of generators, transformers and other devices. It is practically impossible to study these electromagnetic transients using hand calculations except for very simple cases. This complexity led to the simulation of transients using computer.

Keywords: Pspice simulation, Telegrapher's equation Transient, Travelling Waves.

Abstract
Introduction
An overview of 'national conference on power electronics and power systems 2008'
Origin of transient in power system
1. Travellig waves phenomenon in analysis of transmission lines
2. The effect of short lenght of cable transmission line
3. Closing of reisistors for EHV lines
Conclusion
References

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[...] Understanding the transient behavior of the power networks during a fault or switching is of critical importance for power system protection, control and power quality analysis. So far, studies focus on accurate modelling of various power system components such as transmission lines, transformers, switching equipment, rotating machines as well as the control systems that interact with them. Significant work also exists in the area of simulation methods, most of which are developed to be used in the time domain. This paper analyzes simple cases of transmission lines such as line terminated to open circuit, short circuit and the two most well known protections for transients. [...]

[...] NATIONAL CONFERENCE ON POWER ELECTRONICS AND POWER SYSTEM 2008 RAJKOT The analysis of transient waves on a transmission line is frequently carried out by numerically integrating the ordinary differentialequations that describe a lumped RLC model of the line. This technique is practical for many purposes when implemented on a digital computer but requires the solution of a pair of differential equations for RLC section used to represent the line. In this work PSPICE software is used to simulate the lumped circuit model of transmission line. [...]

[...] TRAVELLING WAVES PHEONMENON IN ANALYSIS OF TRANSMISSION LINES: On an electrical transmission line, the voltages, currents, power and energy flow from the source to a load located at a distance propagating as electromagnetic waves with a finite velocity. Hence it takes a short time for the load to receive the power. This gives rise to the concept of a wave traveling on the line which has distributed line parameters l , g , c per unit length . The current flow is governed mainly by the load impedance, the line charging current at power frequency and voltage. [...]

[...] However since current transient recorders lack this classification capability it is imperative to develop an intelligent recorder, that has the ability to distinguish interesting or dangerous events from trivial events.i.e.To NATIONAL CONFERENCE ON POWER ELECTRONICS AND POWER SYSTEM 2008 RAJKOT machines and in some cases result in generalized blackout. Power system transients can be studied using mathematical models for the complete interconnected electrical network components. This is the usual off-line (non-real-time) approach where the simulation time can be much longer than the actual physical duration of the phenomenon. [...]

[...] NATIONAL CONFERENCE ON POWER ELECTRONICS AND POWER SYSTEM 2008 RAJKOT the rate of rise of voltage will reduce drastically. With this we can protect the equipment. A traveling wave can be represented by mathematically in a number of ways. The simplest and most commonly used representation is the infinite rectangular or step wave. This wave jumps suddenly from zero to full value and is maintained at that value there after. Such a wave is most dangerous to apparatus since it abrupt front causes maximum gradients and sustained tail produces maximum oscillations in machine windings. [...]

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