Isolation switch and contactor -safety goalkeeper

2025-06-07 13:19:59

In the power distribution room of the chemical plant, Old Zhang was tightening the grounding bolt of the isolation switch and muttering to his disciple Xiao Wang, "This thing is like a 'gate' on the circuit. If we don't have it to disconnect and discharge during maintenance, we'll be in a barbecue!" Suddenly, a "click" sound came from the adjacent production line - the contact had completed its 200th switching. This seemingly ordinary combination of devices is actually the safety cornerstone of power control.   

1、 Functional positioning: a golden partner with clear division of labor

1. Isolation switch: Guardian of safety isolation

-Visible fracture design: After the knife switch is opened, an air gap of>5mm (12kV level) is formed, and the power-off state can be visually recognized to ensure the safety of maintenance personnel.   

-Zero current operation: It is only allowed to close the switch when there is no load, otherwise it may cause arc explosion (such as a chemical plant misoperation causing a switchgear explosion accident).    

2. Contactor: frequent switching executor

-Second level response: The opening time of vacuum contactors (such as JCZ5 type) is ≤ 45ms, and they can be operated more than a thousand times in a single day, suitable for frequent motor start stop.   

-Arc extinguishing black technology: The vacuum arc extinguishing chamber maintains a high vacuum of 10 ?? Pa, and the arc is extinguished within 0.1 seconds, which is 10 times longer than the lifespan of air contactors.     

2、 Selection and Installation Practical Guide

1. Matching rule

2. Install minefield warning

-Grounding taboos: The grounding wire of the isolation switch should not be connected in series with the contactor housing (it should be separately connected to the grounding grid).   

-Sealing points: Use BDM to clamp the sealing joint at the cable entrance, and the redundant holes must be metal sealed (explosion-proof box specification).   

-Space layout: The heating area of the contactor (temperature rise of 60K) should be kept away from the isolation switch insulator to prevent thermal aging.   

3、 Intelligent operation and maintenance: from fault repair to predictive intervention

1. State awareness upgrade

-Isolation switch: laser sensor monitors contact wear (>3mm warning), wireless temperature measurement patch guards against overheating at connection points.   

-Contactor: The vacuum arc extinguishing chamber integrates a vacuum degree sensor (threshold 10 ? Pa alarm) to prevent air leakage from causing arc extinguishing failure.   

2. Digital Twin Preview

A coal mine project imported equipment parameters into the simulation system, exposing two interlocking logic conflicts in advance to avoid underground short circuit accidents.   

3. Breakthrough in environmentally friendly materials

-Isolation switch: C5-FK gas replaces SF6 (GWP<1), which has been widely used in wind power projects in Europe.   

-Contactor: Encapsulated with bio based epoxy resin, biodegradable for scrap (pilot in 2024).   

conclusion

Isolation switch and contactor - the former is the "safety goalkeeper", and the latter is the "agile operator". Under the wave of intelligence and low carbonization, both are evolving from mechanical components to data nodes. In the future, with the deep application of digital twins and environmentally friendly materials, this combination will continue to safeguard the safe and efficient operation of the power system.