Lightning can damage a site in two different ways. The first is a direct strike on a building or structure. The second is a surge: a transient overvoltage that travels into a site through its power, data and telecommunications lines. A surge lasting microseconds can destroy switchgear, servers, control systems and communications equipment, and the downtime and data loss that follow can cost more than the hardware itself.
Each risk needs a different kind of protection. A lightning protection system deals with the strike. Surge protection devices deal with what travels along the cables. Most critical sites need both, and this guide explains how they fit together.
What a Lightning Protection System Does (and Does Not Do)
A lightning protection system does not prevent lightning from striking. It gives the discharge a controlled, low-resistance path to earth, so the current does not pass through parts of the structure that cannot carry it, such as wood, brick, tile or concrete.
A conventional lightning protection system, such as the flat tape system supplied by NPS, is built from three main parts:
- Air termination network: captures the strike at a preferred point so the current can be directed safely to the earthing system.
- Down conductors: provide a low-impedance path from the air termination to earth. Routes should be as direct as possible, avoiding sharp bends to reduce the risk of sideflashing.
- Earthing system: each down conductor needs its own earth, with a way to disconnect it for testing. Individual lightning earths should be bonded together, and bonded to the surrounding facility earths, to limit the rise in earth voltage.
The manufacturer’s guidance for this type of system is that the resistance to earth, measured at any point, should be less than 10 ohms. A lightning protection design is a site-specific job, so it starts with a survey rather than a catalogue. See the conventional lightning protection system for the components in detail.
Surge Protection Devices: Why One Device Is Not Enough
Effective surge protection is not a single device. It is a cascade of surge protective devices (SPDs) installed at different points across a site, each rated for a different level of energy:
- Type 1 (main switchboard): handles the high-energy partial lightning currents produced by a direct or nearby strike. It is needed where a structure has a direct lightning protection system or an exposed overhead supply.
- Type 2 (distribution boards): handles the residual energy that passes the first stage, plus the switching transients created on site by motors, drives and heavy machinery.
- Type 3 (point of use): sits close to the equipment and clamps the last of the residual voltage to protect sensitive electronics directly.
Examples from the NPS range, and where they sit:
| Product | Where it fits | Key details |
|---|---|---|
| Eaton SPD3200 | Point of entry, three-phase | Class I and II, 200kA per phase, built-in surge counter and failure alarm relay, 5 year warranty |
| LPI Spark Gap Power Protection Module | Main switchboards and distribution boards | Class I spark gap surge diverters in a metal enclosure, single-phase and three-phase ranges |
| Eaton SPD50NGI | Boards remote from the MEN point | Compact neutral-earth protection, compatible with most switchboards |
| NPS Industrial Surge Filters (10A and 16A) | Point of use | Surge protection with EMI/RFI filtering, IP24 enclosure, suited to plug-in UPS systems, servers, instrumentation and POS systems |
Power Boards and Hardwired Surge Protection Are Not the Same
A plug-in surge protector or power board gives basic protection to the equipment connected to it. It does nothing for the incoming supply, the switchboard or any equipment that is not plugged into it. For commercial and industrial sites, hardwired SPDs installed at the switchboard and distribution level divert much larger transients before they reach your equipment, and point-of-use protection then deals with what remains.
The same applies to a UPS. A UPS protects against loss of supply and poor power quality, but it is not rated to absorb the energy of a lightning-induced transient. Equally, a surge protective device does nothing during a blackout. Critical sites need both, specified together. For more on the difference, read UPS vs Surge Protection.
Data and Telephone Lines Need Protection Too
Power is only one way in. Lightning-induced overvoltage can also arrive on signal, data and telephone cabling, and it can damage network equipment, security systems and communications infrastructure at the point where those cables enter a building.
The LPI range supplied by NPS covers this entry path. The D-Series signal and data protectors suit RS-232, RS-422, RS-423 and RS-485 interfaces and 20mA and 50mA instrumentation loops, while the D3 TA and D3 T protectors cover ISDN, ADSL, PCM and analogue telephone lines.
Early Warning: Lightning Warning Systems
Protection hardware limits damage to equipment. A lightning warning system helps people make decisions. The LPI Lightning Warning System MKIII is a non-directional detector that indicates nearby lightning strikes and significant changes in the local electrostatic field. Its listed features include:
- Early detection of lightning activity within approximately 25km
- An alarm when lightning approaches within approximately 8 to 10km
- An all clear indication once the storm has passed
- Wireless communication between the console and multiple sensors
Five Questions to Ask About Your Site
- Is the structure exposed enough to need direct lightning protection?
- Is the incoming supply overhead or otherwise exposed?
- What equipment sits at the main switchboard, the sub-boards and the point of use?
- Which data, telephone and signal lines enter the building?
- What would an hour of downtime cost, and is a UPS already protecting the load?
If you are unsure what is reaching your equipment today, a power quality audit logs voltage, including sags, swells and transients, so protection can be matched to what is actually happening on site.
Frequently Asked Questions About Lightning and Surge Protection
Does a lightning protection system stop lightning from hitting a building?
No. A lightning protection system does not prevent a strike. It captures the discharge at a preferred point and carries the current safely to earth through down conductors and an earthing system, so it does not pass through the structure.
What is the difference between lightning protection and surge protection?
A lightning protection system protects the structure from a direct strike. Surge protection devices protect the equipment inside from transient overvoltages that arrive through power, data and telephone lines. A site often needs both.
What are Type 1, Type 2 and Type 3 surge protective devices?
They are three stages of protection. Type 1 sits at the main switchboard and handles high-energy lightning currents. Type 2 sits at distribution boards and handles residual energy and switching transients. Type 3 sits at the point of use and protects sensitive equipment directly.
Is a surge protector power board enough for commercial equipment?
A power board protects only the equipment plugged into it and does not protect the incoming supply or the switchboard. Commercial and industrial sites use hardwired surge protection devices at the switchboard, with point-of-use protection closer to the equipment.
Do data and telephone lines need surge protection?
Yes. Surges can travel in on data, telephone and signal lines as well as on power. Data line protectors safeguard network equipment, security systems and communications infrastructure where those cables enter the building.
What is a lightning warning system?
A lightning warning system detects nearby lightning activity and signals when a storm is approaching and when it has passed. It does not protect equipment itself. It gives site managers the information to make decisions about people and operations.
Talk to NPS About Lightning and Surge Protection
NPS designs, supplies, installs and maintains lightning and surge protection systems across Australia and New Zealand, with offices in Sydney, Melbourne, Brisbane and Perth and more than 30 years of power protection experience. Solutions are designed to meet the relevant Australian and New Zealand standards and installed by qualified technicians.
Explore the full lightning and surge protection range, see how NPS approaches power protection in mining, transport, security and communications, or contact the team to discuss your site.