Risk Assessment of DC Component Generated by Single-phase Switch Reclosure

In transmission lines, in order to ensure reliable power supply and safe operation of the system, single-phase switch reclosure is widely used in morden power systems due to its simple logic and mature technology. For long-term or permanent faults, the current flowing through the switch before and after reclosing cannot suddenly change, resulting in the generation of DC component. The amplitude or dacay time of the DC component being too large may delay the zero crossing time of the current flowing through the switch, leading to the failure of the switch tripping, and ultimately causing serious consequences and incalculable losses. The existing national standards only propose short-circuit current calculation methods that consider DC components, and do not involve the calculation and risk assessment methods for DC components generated by single-phase switch reclosure in transmission lines. This article analyzes the mechanism of the DC component generated by single-phase switch reclosure, proposes a practical engineering algorithm, and put forward a risk assessment method. The study case proves the practicality and convenience of proposed method.