Research On The Geomagnetic Storm Disaster Risk Assessment Framework And System Of Large Power Grid

Geomagnetic storm disaster is a new challenge the power grid has to confront as it continues to expand. It has been a field for interdisciplinary research including geophysics, physics and power systems whereby previous studies have all got their certain limitations. In order to establish a solid framework of risk assessment theory for the power grid geomagnetic storm risk assessment, this paper takes the perspective of a power grid and investigates the factors influencing the power grid geomagnetic storm disaster, the interference effect in the power grid due to geomagnetic storm, the harm of geomagnetically induced currents (Geomagnetically Induced Current, GIC). Based on a large number of previous literatures of the risk assessment for geomagnetic storm disaster, our research work has achieved desired results.Main research work and innovations are as follows:Firstly, the factors and mechanisms are investigated from three aspects including storm intensity, soil resistivity and grid structure, in which mechanisms of the influence of different factors are analyzed both theoretically and practically. Furthermore, based on "GIC benchmark" proposed in 2012, levels of such influences are quantified and compared between different driving factors.Secondly, the dissertation depicts the key problems for disaster risk assessment of the power grid and made a summary of theoretical methodology and achievements in literatures on power grid GIC and GIC derivative interference. According to entropy theory and extreme value theory, evaluation method and indexes are proposed targeting at three key GIC derivative problems including reactive power loss, temperature rise and power grid fault severity. Disaster risk assessment for power grid stresses on three aspects:index for GIC reactive power loss, index for transformer temperature rise, and index for fault severity.Thirdly, the dissertation analyzes risk-related key factors, power grid GIC and its derivative effects. Considering GIC impact on China’s EHV and UHV power grid transformers, this paper establishes the concept and framework for risk assessment based on grid dynamic responses to geomagnetic information, GIC harmonics and reactive power fluctuation, and later forms the integrated model of geomagnetic storm-power grid dynamic response. In this way, the framework for power grid geomagnetic storm risk assessment is established, and the effectiveness of these indexes and the framework are tested and demonstrated through GIC Benchmark.This dissertation investigates and establishes the indexes and methodology for power grid geomagnetic storm risk assessment, which is significant to the theoretical analysis of geomagnetic storm disaster, disaster protection and device research and development. The research and conclusions of this paper set the foundation for risk assessment of power grid geomagnetic disturbance and the establishment of the index system.the communication process and response mechanism of power system fault induced by geomagnetic storm is dissected. The characteristics of the risk suffered by a bulk power system under the geomagnetic storm disaster are outlined. We categorized and summarized worldwide researches on all influence factors, including geomagnetic storm intensity and GIC in power grid and transformer interference. Comparative analysis is made on the mechanism and effect of various influence factors based on sensitivity analysis method. To reveal the key factors of power grid risk under a geomagnetic storm disaster, different effect of various influence factors are weighed based on the "GIC Benchmark" model proposed collaboratively by several international institutions in 2012.Secondly, the hazards of transformer harmonic, heating and reactive power fluctuation resulted from GIC and theirs derivative interferences are analyzed. The influence of transformer derivative interference and the characteristic as well as the feature of power grid fault distribution is summarized. On the base of GIC in power grids and the transformer derivative interference, the evaluating index system measuring the power grid disaster risk is proposed, which focuses on three aspects including transform reactive loss, transformer heating and the severity of power fault.Thirdly, the risk elements of power grid disaster and GIC as well as derivative effect are analyzed. To concentrate on the geomagnetic storm impact on the extra high-voltage and ultra-high-voltage power grid and transformer equipment, the concept and basic idea of the risk assessment for the geomagnetic storm disaster are presented based on the information about geomagnetic disturbance and the power grid dynamic response to derivative interference due to harmonic and reactive power fluctuation resulted from GIC. The causal chain from geomagnetic storm disaster to GIC to power system fault risk is developed. The framework of risk assessment theory for large power grids influenced by geomagnetic storm disaster is established in consideration of the controllable and uncontrollable factors about power grid disaster due to geomagnetic storm.This dissertation focuses on the need for evaluating the risk of power grids disturbed by geomagnetic storm disaster and establishes the theoretical framework of the risk assessment as well as the index for the risk. This research has an important meaning to the analysis method of the power grid under geomagnetic storm disaster, disaster prevention and management of equipment development. The conclusions of this paper lay a solid foundation for the risk assessment theory and index system of power grids under geomagnetic storm disaster.