Luminaires failed after a thunderstorm: recognising surge damage

What you find the morning after

The call usually comes the morning after the storm: part of the site or street lighting is no longer working. A surge leaves a recognisable trail:

• Several luminaires on the same circuit have failed at once, often the columns furthest from the distribution board.
• The fuse in the column cut-out is intact. A spike lasting a few microseconds is over before a fuse can respond.
• The luminaire is dark, flickers or runs at half output.
• The LED module is intact. Inside the luminaire you see a discoloured or cracked varistor or a black mark at the driver input.

Other causes look different. A cable break takes out the whole circuit and trips the MCB. Water in a luminaire affects one lighting point and trips the RCD. A worn-out driver fails at random, spread over months, not three at once in a single night.

How to diagnose it on site

Work through the circuit in this order:

• Note the date, time and weather. Strikes in the area can be looked up afterwards in public lightning records.
• Isolate the circuit and check the fuse and the earth braid in every cut-out.
• Measure the insulation resistance of the cable with all luminaires disconnected. Never test at 500 V on a connected driver or SPD.
• Check the SPD module. If the SPD has failed and the driver is intact, the protection did its job.
• Test the driver. Mains voltage at the input and nothing at the output means a dead driver. If the SPD is undamaged as well, the spike exceeded the SPD rating or came in via the PE or the control line.

Put the pattern on a site plan: which columns, how far from the distribution board, which SPD rating. That points to the weak spot.

Replacing the SPD and the driver

An SPD is a wear part. Every spike it diverts wears the varistors further, until the module disconnects the luminaire. Replace per circuit, not just at the dark columns: the SPDs in the luminaires that still work have handled the same spike.

The street luminaires of VIA have 10 kV surge protection as standard, and on some versions the driver sits separately. You then swap only the driver and the SPD module and leave the housing and LED module on the column. Choose the same current setting and the same control protocol, otherwise the light level along the circuit will drift apart.

If you are replacing an older luminaire without an SPD or with 2 to 4 kV, fit the new 10 kV luminaire on the outermost columns first. Why 10 kV is the right rating for columns in open ground is explained in Surge protection: why 10 kV.

Earthing: where the spike goes

An SPD diverts energy, and that energy has to go somewhere. On a class I luminaire on a steel column such as TURRIS, the path runs through the PE core, the earth braid at the door opening and the cut-out. If one connection is loose or corroded, only the protection between L and N works.

So after every fault, check the earth braid and the PE terminal. The NEXUS cut-outs have earth braids and one or two fuses per column: the fuse protects against short circuit, the earth braid completes the SPD. If the same columns fail in every storm, the second stage is almost always missing: a type 2 SPD in the distribution board at the start of the circuit.

Warranty and insurance: who pays

The warranty on luminaires, up to 5 years at Lichtplein, covers material and manufacturing defects. Damage from an external cause such as a surge is excluded by almost every manufacturer, and an SPD that has done its job is not a defect but a worn part.

For the owner, insurance is the right route. Many buildings and business policies cover lightning strikes; damage from induction, a spike without a direct strike, is often a separate cover or excluded. Search the policy for the word induction. The insurer will typically ask for the date and time of the storm, a list of failed lighting points with photographs, a statement from the installer about the cause, and the invoice for the repair. Keep the failed parts until the claim is settled.

Prevention in new installations

Four measures prevent most of the damage:

• 10 kV in every column-mounted luminaire, standard on VIA. If you choose a floodlight on a column, for example from FLUX, check the SPD rating in the specifications. Indoors under a roof, such as an ATRIA high bay, a lower rating is usually sufficient.
• A type 2 SPD in the distribution board at the start of every outdoor circuit, or type 1 if the building has a lightning protection system.
• A closed earth path: a PE core in the cable, the earth braid connected and the connection tested at handover.
• Keep circuits short: the longer the cable in open ground, the higher the induced spike.

Record the SPD rating per lighting point in the installation file and plan an inspection round along the outermost columns after every heavy storm. With DALI-2 or D4i luminaires from the VIA range, combined with a lighting management system, you see straight away which lighting point has failed.

Frequently asked questions