Since most elevators are located in high-rise buildings, the upper part of the machine room (core) is located at the top of the building, the control system is located in the elevator car and on each floor, and the cable lines of the power supply system and communication system run through the entire building. Elevators are at great risk of lightning strikes, lightning induction, lightning wave intrusion and electromagnetic radiation during lightning electromagnetic pulses. At present, the elevator machine room equipment and control system have been damaged by lightning strikes.
1. Direct lightning strike: Lightning strike on the elevator directly causes equipment damage or lightning strike on the cable directly causes cable damage. The damage caused by this lightning strike was severe, but there was little exposed equipment in the elevator. Cables are mostly buried and concealed, so the probability of occurrence is relatively small.
2. Lightning induction: divided into electromagnetic induction and electrostatic induction. When there is lightning in a nearby area, a strong transient electromagnetic field will be generated around the lightning implementation channel. Equipment and lines will generate a large electromotive force in the electromagnetic field, which is called electromagnetic induction; when a charged thunderstorm occurs, buildings and transmission lines under the thunderstorm will induce opposite charges. This phenomenon is called electrostatic induction. Equipment damage caused by induction lightning is smaller than direct lightning, but the probability of occurrence is higher, accounting for more than 80% of modern lightning accidents.
3. Lightning electromagnetic pulse: Lightning electromagnetic pulse is a source of interference. Refers to the impact of direct lightning strikes on lightning protection devices of buildings and nearby buildings. Direct lightning strikes as sources of interference and effects caused by nearby lightning strikes. Most of them are interference caused by connecting conductors, such as lightning current or partial lightning current, potential increase of the equipment struck by lightning and magnetic radiation interference.
4. Lightning intrusion wave: When metal cables are struck by lightning or induced by lightning, lightning waves invade the equipment along these metal conductors/conductors, causing high potential differences and equipment damage. In addition, long conductors such as long tracks, long wires, and long control wires in elevator equipment may also induce lightning to form strong currents, which can invade elevator equipment in the form of surges, damage electronic components, and cause elevator failure.
Elevator lightning protection measures first require that the lightning protection device of the building where it is located meets the requirements of national standards. The lightning protection of indoor elevators should be combined with the lightning protection device of the building. Lightning protection for outdoor elevators should fully consider factors such as the geographical environment, geological soil conditions, regional lightning activity patterns, and elevator data.
1. Direct lightning protection
Direct lightning protection devices in main buildings equipped with elevators should comply with regulations. Lightning protection strips should be used on the roof of the mechanical room of the building. The reserved grounding terminal in the elevator machine room shall not be used as a down conductor to be led out from the steel bars in the column. The safe distance between the electrical equipment in the elevator machine room and the down conductor should be maintained at more than 0.6m.
2. Lightning protection against electromagnetic pulse
The metal parts of the elevator car, guide rails and machine room should be equipotentially connected. The grounding down conductor of the elevator machine room adopts the building non-direct lightning down conductor. The two main bars of the structural column should be welded to each other to the elevator machine room. Elevator electrical and electronic systems should be equipped with SPD lightning protection electromagnetic pulse. The electrical system and electronic system lines are laid in metal trunking, and are grounded repeatedly every 20-30m, with both ends grounded.
3. Lightning protection in elevator machine room
All metal components in the elevator machine room, such as metal frames, metal devices, external conductors, electrical devices, communication devices, traction machines, metal wire ducts, etc. , connected with the equipotential connecting board to form an S-type equipotential connecting network to achieve voltage equalization and equal potential, preventing fire, explosion, life danger and damage to equipment that needs to be protected.
4. Lightning protection of power supply and control lines
The elevator control system is mainly composed of speed regulating system
