Study Of Key Theoretical And Technical Features Of The Dynamic Loading Of High Voltage Overhead Transmission Lines

In recent years, there has been an unprecendented increase in economic activitiesin China. This scenario has led to an increase in demand for more electrical energyuseage. Some existing high voltage overhead transmission lines have experiencedtechnical specification limitations, and this has had a negative impact on thetransmission capacity increase opportunities. Constructing a new transmission powerline is not only costly, but also time consuming and politically difficult to obtain theright of way for the new overhead line. Nevertheless, the power system engineers arefaced with a task to reliably increase the capacity of existing transmission lines. Thus,this thesis uses the mathematical models based on the heat balance equation toestablish the principles of dyna mic loading of high voltage overhead transmissionconductors. This provides an important basis for the safe and reliable operation of thepower network during dynamic loading of overhead lines.Based on the heat balance equation, this thesis establishes th e basic mathematicalmodels for the calculation of conductor sag during the power flows in overheadtransmission power lines. It also develops a computer program for the dynamic loadingof conductors based on weather patterns and conductor tension. This pr ogram can beused to calculate real-time conductor loadings by taking real-time weather data intoaccount. As load current flow increases, the sag between any two towers experiencesan increase too. This situation increases the amount of electromagnetic fi elds availableon the ground of the transmission corridor. This can compromise the externalinsulation integrity of the line, especially during dynamic loading. Hence, this thesisalso uses the Catenary model to explicate how conductor sag affects the safe ty of theline. Factors such as conductor weight, wind speed and conductor temperature aretaken into account in a MATLAB code analysis.The strength of the electromagnetic field on the ground determines the safetylevels of the overhead line. High values of voltage gradients on conductor surface canlead to corona dischare. Corona discharge doesn t only cause conductor heating, butalso causes radio noise and television interference. Increase in electric field betweenconductor spacings can cause short cir cuits. Based on these facts, this thesis uses themulti-segment charge modeling to analyze the conductor surface, conductor spacing,different tower structure, and ground level electromagnetic field distribution patterns.These patterns are then incorporated into the computer program in MATLAB for dynamic loading to see how the field values vary during a power flow. The computerprogram for dynamic loading was then applied to a case study500kV network ofHunan province. The calculated values and the measu red values were very consistedfor a capcity increase between10%and30%.The research in this thesis shows that the mathematical models for conductorsag, and the charge modeling for ground level electromagnetic field calculations, basedon weather data, can be the theoretical basis for dynamic loading of high voltageoverhead transmission lines. The developed computer program in MATLAB and ETAPcan be used to forecast hidden transmission capacity of the line. This is a goodreference for the power system operators.