Testing And Inhibition Of The Voltage Third Harmonic In Substation

With the continuous development of economy and the constant expansion of powersystems, power quality has gradually become a hot issue of power supply enterprises and themajority of users. The electrical energy is a form of energy which is economical andpractical, convenient, easy to transport, control and convert, also is a special commoditywhich provided by the power supply enterprises to the electricity users by for both sides toensure the quality. As the process of market-oriented electricity as a commodity, also has aquality requirement, so power quality has become the problem which the power supplyenterprise and power users need to face.By testing, this paper analysis the existence and distribution of the grid voltage harmonicof Foshan district; by collecting the basic data of the Foshan grid, the main wiring, Devicetype, user type and the Dedicated distribution of the high third harmonic voltage Transformersubstations, based on decision tree analysis method to establish a simulation model of thesubstation, the simulation analysis on the impact of various factors. In November2010, weconducted a field test on110kV Heshui substation, in the test results of110kV Heshuisubstation, we found the three-phase asymmetric third harmonic, so we add the theoreticalcalculation and simulation analysis of asymmetric three harmonic to the simulation model.Between May to July2011, according to new simulation models and results oftheoretical analysis, we conducted further field test on110kV Jizhou substation and110kVManin substation. By analyzing the combination of simulation results and field testresults,we found out the main reason of the generation of third harmonic voltage, proposedthe method to find the harmonic pollution source and the means and strategies to solve thethird harmonic voltage problem. Established a simulation model of the PT resonanceeliminator at the same time, analysis on the characteristics of the PT resonance eliminator;proposed method to eliminate the voltage harmonics, and be verified by simulation.This paper carried out a great deal of theoretical analysis, simulation and field tests onthe causes of third harmonic, based on decision tree analysis method to find the reason of thethree voltage harmonics from the user side, the system side and the measurement system,Proposed the specific solutions to the three voltage harmonic problems, both from the user side and the measurement system against the situation of Foshan power grid, by combiningthe simulation results and field test results, innovatively proposed a method to find theasymmetric third harmonic pollution source which is based on the direction of harmonicpower. This method can effectively find the third harmonic pollution sources, provide thebasis for monitoring and evaluation the pollution user which want to take an access to thepower system and avoid the pollution of these users.