What IEC 62305 covers for a display structure
The standard replaced the older national and regional lightning codes and now sets the general principles for protecting structures and the systems inside them. It is written in parts: general principles, risk management, protection of the structure itself, and protection of electrical and electronic systems.
For a display the two parts that matter most are the structural protection and the system protection. Structural protection deals with the path lightning would take through the mast, frame and building. System protection deals with what the surge does to the power supply, the drivers and the control links once it reaches the cabinet.
The standard does not prescribe one fixed solution for every site. It sets a method: assess the risk, choose a protection level, then build the air termination, bonding and surge protection to match that level.
How the risk assessment decides the level
The assessment weighs how often lightning is expected at the site, what the structure is made of, how exposed it is, and what would be lost if it failed. A tall mast in an open field scores differently from a screen set against a larger building that already carries its own protection.
The outcome is a lightning protection level, from the highest level down through lower levels, each associated with a tolerable flash severity. A higher level means a more robust air termination and tighter bonding, and it is chosen where the consequence of a strike is highest.
This is why the level belongs on the project specification as a result, not as a copied number. A screen relocated from a sheltered city roof to an open coastal site can move to a different level without any change to the panel itself.
Protecting the structure around the display
Structural protection gives lightning a controlled path. An air termination sits above the structure to intercept a strike, down conductors carry the current to earth, and the earth termination dissipates it. The geometry of the air termination is set by the rolling sphere method, which defines the volume the termination must cover.
Bonding is the part that fails quietly. Metal frames, masts, cable trays and adjacent structure must be bonded so that a strike does not jump across a gap and arc through the display. Where the display is mounted on a building that already has protection, the display and its supports are tied into that existing system.
Separation distance matters for the parts that are not bonded. Cables run too close to a down conductor without enough spacing can be damaged by the induced field, so the routing of power and signal is part of the protection design, not an afterthought.
Protecting the drivers and the power
Even with good structural protection, a nearby strike sends a surge along the supply and the data lines. Surge protective devices at the incoming power and at sensitive points clamp that surge before it reaches the drivers and the power supplies.
For a display, the vulnerable items are the switched-mode power supplies, the receiving and sending cards, and any long signal runs to a control room. Each of those paths is a candidate for coordinated surge protection sized to the protection level.
Coordination is the key word. A single large protector at the entry and smaller ones close to the equipment work together so the surge is stepped down in stages, never dumped all at once. Protection that is not coordinated can still let damaging energy through.
Verifying lightning protection on a real project
The specification should state the lightning protection level the design was assessed against and name IEC 62305 as the basis, so the level can be checked against the actual site, not assumed.
Ask where the surge protection is fitted and whether it is coordinated, because a protector drawn on a diagram and a protector actually installed at the cabinet are different things. The driver and power supply models should be confirmed to tolerate the clamped surge level.
Tie the protection to the structure, not to the panel alone. A display is only as protected as the mast, the bonding and the earthing it shares, so the review covers the whole installation, not just the screen.
A rooftop wall with no surge path
An outdoor wall on a roof had no surge protection on its power feed. A nearby strike took out the drivers; adding coordinated surge devices would have spared them.
Risk level set by location
Two sites bought the same wall, but one sat on a hill with tall structures nearby. The IEC 62305 assessment demanded a higher level there, changing the protection spec.
How to apply this
- Run the risk assessment Apply IEC 62305 risk assessment for the structure's height and location. The result sets the protection level; do not assume a fixed grade.
- Protect the structure around the display Provide a controlled path for lightning on the mast, frame and building so the strike goes where it is designed to, not through the screen.
- Shield drivers and power Fit surge protection on the power and signal lines feeding the drivers. The damage from a strike rarely starts at the panel itself.
- Verify on the real project Confirm the assessment level, the structural path and the surge devices are installed and documented at handover, especially for towers and rooftops.
Common misconceptions
“One surge protector is enough.” — Lightning protection is layered: structural path plus coordinated surge protection on power and signal. A single device leaves the drivers and lines exposed.
“Only tall towers need protection.” — Any outdoor display exposed to open sky carries strike risk; the level follows the IEC 62305 assessment of the site, not just height.
Key takeaway
IEC 62305 protects a display through a risk assessment that sets the level, a structural path that controls where lightning goes, and surge protection that shields the drivers and power. The level follows the site, so it is confirmed in the specification as a result of the assessment and tied to the whole structure, not copied as a default.