Calculation And Influence Factor Analysis Of Reactive Power Of Transmission Line Based On Poynting Vector

With China’s growing electricity load, the construction of underground powercables and UHV transmission lines with high voltage level has undergone a rapidprogress. Because high voltage transmission lines have the characteristic of longdistance and large transmission capacity, it is of significance that the reactive powercompensation to stablize the operation of AC high voltage transmission lines. However,the equivalent parameter of transmission lines will change when overhead transmissionline is icing and underground power cable tunnel is destructive, at this time, thechanging of electrical parameters of the transmission line should be considered whenreactive power of transmission lines is computed and analyzed.The traditional method to analyze the transmission power is from the circuitperspective, which is based on the calculation of equivalent parameters of transmissionline. However, considering the icing of transmission line and the de-normalized cableinstallation, the equivalent parameters are changed and power of transmission line willbe more complicated to calculate by circuit method.Hence, this paper proposes the power transmission model of transmission linebased on Poynting vector to solve the problem. the model is based on field method.Firstly, this paper has derived the numerical expression of electromagnetic power byPoynting vector. Then, proposed the calculation model of3D electromagnetic powerflow around transmission line based on method of FDFD, and the ribbon simulationcharge is porposed in the model to calculate the electric field on original section. Themodel can calculate the power transmission situation of the irregularly iced overheadline and less standard cable.The paper has used the proposed model to calculate thepower transmission under the situations of the sag and icing of transmission line, thecable eccentric, the air gap in cable and water in cable tunnel. The calculation resultsindicate that:1. The sag lead to the capacitive and inductive reactive power of transmission lineincreace. There is a large increace of capacitive reactive power loss and a smalldiscreace of the inductive at the lowest point of transmission line. While at thesuspension point, the capacitive and inductive reactive power loss both increace a little.2. The capacitive reactive power loss increase as the icing thickness increase. Andin same icing thickness, comparing the value of capacitive power loss under different icing shapes, the result is: circle <oval <crescent and oval <eccentric oval <D style.The regular conform that the icing more irregularty and the capacitive power lossincreace more.3. The total reactive power loss of cable is capacitive. The water makes thecapacitive power loss increase49.89%. The cable capacitive power loss increacementincreace with the increace of eccentric displacement, following quadratic function rule.This paper has analyzed the relationship between relative permittivity andenvironment temperature and relative humidity by fitting the data of the measuredelectric value in different environment temperature and relative humidity. Thetransmission line power loss in various environment temperature and relative humiditysituations has been calculated by the proposed model, and the influence of temperatureand relative humidity to the equivalent circuit parameter of transmission line has beencalculate and analyzed in the view of power.