Protection Coordination of AC/DC Intersystem Faults in Hybrid Transmission Grids
Jonas Prommetta, Jakob Schindler, Johann Jaeger, T. Keil, Christoph Butterer, G. Ebner
Abstract
The new characteristics and phenomena of hybrid AC/DC transmission grids challenge the conventional protection concepts. In hybrid AC/DC overhead line systems, AC and DC systems are located on the same support structure. As a result, electromagnetic and galvanic interactions between the AC- and the DC-line influence the AC-protection and the DC-control in a novel and complex way. This paper presents key findings and solutions from a current 400-kV-hybrid AC/DC overhead line project in Germany. The focus is on AC/DC intersystem faults, i.e. galvanic contact between DC and AC systems. Fault detection and fault response of the AC-protection and the DC-control as well as a proper AC/DC protection coordination are discussed. The paper illustrates the challenges of a secure and dependable fault clearing and indicates solution methods. The findings of this paper are based on EMT simulations with detailed PSCAD-models of the hybrid AC/DC overhead line and the VSC-converters. Laboratory protection tests have been conducted and confirmed the results.