Effect of polymer ablation gas on arc quenching properties around current zero

Abstract

The influence of polymer ablation on arc properties such as the temperature distribution and arc conductance in the current decay process was investigated by numerical approaches. A numerical thermofluid model was developed for a simplified circuit breaker with POM or PTFE ablation. In this model, thermal plasma-polymer solid coupling phenomena such as melting and evaporation were taken into account without any empirical model based on measurements, unlike other existing numerical thermofluid models. The dominant process for the decay of arc conductance was examined by changing the thermodynamic parameters such as the melting and boiling temperatures of solid polymers, or the thermal conductivity and electrical conductivity of the ablation gas. It was found that the gas density, thermal conductivity, and electrical conductivity of the ablation gas were more effective for decaying arc conductance than any other thermodynamic parameters.

A study on thermal‐interrupting performance improvement of SF6 gas circuit breaker by promotion of nozzle ablation

“…Refs. investigate Nylon polymers such as POM (Polyacetal) and PA6, as well as numerous polymer resins such as polyethylene (PE), as ablation materials for circuit breakers. One characteristic of these polymer resins is that hydrogen atoms (H) are contained in the polymer composition.…”

“…At the time of current interruption, air decomposes into nitrogen atoms (N) and oxygen atoms (O). When the ablation material vapor containing H atoms is mixed with this high‐temperature gas containing N and O atoms, it facilitates gas cooling due to the high thermal diffusivity of H atoms, resulting in an improvement of thermal interruption performance of the circuit breaker .…”

“…As a means to enhance the arc plasma‐extinguishing capability of circuit breakers, it is possible to evaporate a polymer due to the energy of the arc (ablation), resulting in an arc cooling effect and pressure increase in the arc extinguishing chamber. In low‐pressure air circuit breakers, such as low‐voltage circuit breakers, ablation of polymer resin in the vicinity of the arc extinction chamber is actively used for arc plasma extinction . The ablation of these polymer resins changes the gas composition inside the circuit breaker and the pressure configuration around the arc and consequently affects the current interrupting performance.…”

Ablation-assisted current interruption in medium voltage switchgear – Development and prospect

“…The processes governing the arc parameters around current zero are extremely fast and difficult to observe. Onchi et al [14] have performed a theoretical investigation of the effect of polymer ablation on arc quenching properties around current zero. The calculations of change in temperature and electric conductivity were performed with PTFE, POM and a range of fictitious polymers in a cylindrical tube.…”

Medium-Voltage Load Current Interruption in the Presence of Ablating Polymer Material

“…One approach is modelling the decay in temperature and electric conductivity around the current zero (CZ) [9]. However, these models cannot give accurate results without the inclusion of non-equilibrium effects [10].…”