Research On The DC Current Distribution In AC Power System Caused By An HVDC System

During operating and testing on practical HVDC projects, the impact of ground current on power transformer appears quite distinct when the system is operating on monopole ground return mode. This paper focuses on the theoretical research on the DC current distribution in AC power system caused by an HVDC system.In this paper, firstly, Green's functions in a horizontal-layer or a horizontal-layer and vertical combined-layer soil structures are derived by equivalent complex image method, and the program for calculating the potential distribution is developed. The calculation results from the program are identical with those from reference home and oversea. Secondly, the field-circuit coupling method of calculating the dc current distribution in ac power system is presented by using electromagnetic field and circuit theory, and the resistance network algorithm is presented by using self-resistance and coupling resistance conception. Lastly, some main controlling factors of dc current distribution in ac power system caused by an HVDC system are analyzed, for example, tower and ground wire, soil structures, grounding resistance of transformer substation, trend of line and distribution of transformer substation , etc.. The main innovative achievements are as follows:(1) Analysis is taken on for the calculation method of dc current distribution in ac power system caused by an HVDC system, and it provides the theoretic method for the further study the influence of ground electrode current in HVDC on AC power network.(2)Analyze to some key controlling factors of the dc current distribution in ac power system caused by an HVDC system. The results provide a theory to research on measures of DC influenceground electrode current reducing on AC power network and can be utilized as a reference for substations selection near the HVDC ground electrode.(3) Despite the consideration limited of one dimension space(x axis or y axis) for simplifying the analyzing of controlling factors, the study brings some illuminations for future study, whatever.