Study On The Treatment Of Transformer Bias With The Effect Of Geomagnetic Storm And Ground Pole

As the size of the power grid increases,the impact of ground electrodes on the power grid and its governance have become a concern.The construction of many DC projects needs to deal with the influence of ground electrodes,but the current treatment projects do not consider the impact of the geomagnetic induction current(GIC)on the power grid.It is necessary to consider the influence of ground pole bias magnetic treatment on the GIC of the power grid and the effects of comprehensive ground pole and geomagnetic storm.Taking±800kV Baihetan-Jiangsu UHVDC transmission project as the object,this paper considers the combined effects of geomagnetic storms and ground electrodes,studies the risks of Jiangsu power grid,and proposes a biased magnetic management plan.The main research contents and results are as follows:Based on the finite element method,the three-dimensional resistivity modeling and ground potential calculation of the near area of the stepped ground are completed.Reveals the law of non-uniform attenuation of ground potential in complex earth structures.The results show that the ground currents of the common ground electrodes 5000A and 8000A have a greater impact on the ground potential within a radius of 200km.Combined with the actual measured potential values of the project,it shows that the ground potential algorithm based on the three-dimensional earth model has higher accuracy.Based on the GIC-Benchmark standard example,a bias current model of Jiangsu 220-1000kV power grid was established.Based on the field-circuit coupling iteration method,the calculation of the bias magnetic current of the Jiangsu 220-1000kV power grid under the influence of the DC ground electrode was completed.The results show that the level of bias current caused by the ground electrode is related to the distance between the ground electrode and the line length.Combined with the actual measured bias current value,the accuracy of the ground pole bias current algorithm is verified.The geomagnetic storm data of Beijing Geomagnetic Station in March 1989 was used to calculate the induced geoelectric field in Jiangsu based on the local plane wave method.It reveals that the characteristics of the induced geoelectric field in low-latitude and multi-water areas are generally less than 1V/km.Among them,the value of the induced geoelectric field in Taizhou has the largest change,0.78V/km.Given the high-risk sites for GIC bias faults in Jiangsu 500kV and above substations,this indicates that the risk of GIC accidents in UHV systems with long distances and large sections is greater.It proposes a global optimization method for switching resistance-capacity devices based on non-dominated sequencing genetic algorithm(NSGA-II).Optimizing the treatment plan according to this method can avoid the mutual influence between the ground electrode and the geomagnetic storm.It gives the biased magnetic stations of Jiangsu 220-1000kV power grid that need comprehensive management,which can be used as a reference for project management.The models and algorithms established in this article are not only of great significance for the bias management of the power grid,but also provide reference and technical support for the operation and maintenance of power grid management devices.This paper considers the combined effects of ground poles and geomagnetic storms,and can be used to guide the construction of Baihetan-Jiangsu DC bias magnetic treatment.