Research on the critical size of live working robots between busbars in 220 kV substations

Adopting live working robots to carry out live working can improve the safety of operators, which is especially true when performing live working in substations. This paper focus on the lowest discharge position and the critical size of live working robots between busbars under switching impulse. Finite element method (FEM) was used to calculate the electroquasistatic field. Based on the process of streamer and leader, the breakdown voltage of the phase-to-phase gap containing a robot is calculated. Between the busbars of 220 kV substations, the presented research shows that the lowest discharge position of live working robots locates in 61.5% of the phase-to-phase gap. Breakdown develops from d1 gap once d1 gap is less than 1.5 m. Moreover, presence of the live working robot results in a sharp drop to the breakdown voltage of the complex gap. Referring to the switching overvoltage and the risk of failure, the robot size should be designed less than 0.4 m for 220 kV substations.