Lightning & Surge Protection FAQ's

An Introduction to Lightning & Surge Protection

HV Power have the specialist skills to design and supply lightning and surge protection solutions to meet New Zealand Standard AS 1768.

With our international experience, we can also assist both manufacturers exporting to Europe or America, and consultants designing for European or American standards requirements (IEC 62305 series or UL/NFPA).

Structural protection solutions (External Lightning Protection) can be provided for all building and structure types. We have a range of solutions to suit design-build, or retrofit applications. In addition to buildings, protection can be applied to exposed equipment at process sites, substations, tank farms, communication masts and telecommunication sites.

Internal lightning protection (known as “surge protection” or “Transient Voltage Surge Suppressors” (TVSS’s)) can be applied to equipment within a facility, or exposed equipment cubicles such as road side cabinets, pole top devices, traffic signs or electronic bill boards.

Specialist designs can be applied to rail, telecommunication, cathodic protection and hazardous sites.

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The Evaluation Process

The first step is to evaluate the risk of lighting and surge damage to a given structure/facility (or subset thereof). If the risk is greater than a tolerable level, then an iterative approach is taken to find the most cost-effective application of protection products required to reduce the risk to less than the tolerable threshold.

New Zealand Standard AS 1768 is used to evaluate the risk. HV Power can also use the more exacting IEC 62305-2 standard where required.

The process of Risk Management is used to identify the lightning threats, evaluate the frequency of the risk, evaluate the consequences of the risk, and determine measures to reduce this risk. As an example, risks evaluated include:

• Risk of loss of human life
• Risk of loss of service to the public
• Risk of loss of cultural heritage
• Risk of loss of economic value

Lightning as a source of damage is then considered, specifically the potential effects of:

• Direct lightning strike to the structure
• Strike to the ground near the structure
• Strike to electrical service line
• Strike to ground near electrical service line

A correct Risk Assessment does not just evaluate the risk of structural damage, electrocution or fire caused by direct or indirect lightning, but the combination and possible effects. For example, in structures with large numbers of people, the risk of panic is considered should lightning damage lights or security/fire circuits.

To address high risk situations the Risk Management may not be limited to application of just lightning and surge protection products, but may also require measures to limit fire propagation.

The easiest way to evaluate your risk is to contact HV Power and let us assist you.

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Why consider the effects of direct and indirect lightning?

The power of a direct strike to a facility is easy to understand as we visualise the potential resultant damage. However, a near strike can also cripple most facilities.

• The massive amount of current in a typical lightning discharge (30,000-50,000 A), has a large magnetic field that can couple into low voltage circuits destroying nearby communication, control and fire/security systems.
• The voltage rise at the strike point can be several hundreds of thousands of volts higher than “remote earth”, causing current to flow in nearby circuits in an attempt to equalise voltages.
• A strike to a distant power or phone line can cause a voltage transient that enters into your facility, and damaging equipment.

A strike some kilometres from a NZ university raised the ground potential sufficiently that Ethernet circuits between buildings were damaged. The copper circuits between building became a path for the equalisation current. The correct application of surge protection could have prevented the resulting damage.

This is why an effective lightning protection system will include protection against the direct strike (i.e. an external lightning protection system), and protection against the indirect strike (i.e. an internal lightning protection system using Surge Protection).

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Do I need lightning protection in New Zealand?

Why lightning AND surge protection?

Effective lightning protection is actually a combination of a lightning protection system (LPS) and a surge protection system. These are sometimes referred to as external and internal lightning protection.

External lightning protection primarily protects the building from structural damage, while internal lightning protection protects the internal electrical and electronic equipment.

Installing structural protection to reduce the risk of damage or fire to the structure is of little value if surge protection is not installed. Chances are a nearby lightning strike may enter the facility via an unprotected electrical service, damaging equipment and potentially causing an electrical fire.

For most facilities, the risk of voltage transients on service lines from remote and nearby lightning is higher than the risk of a direct strike. Surge protection also provides protection against other electrical transients such those caused by network switching events.

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What standards are important?

“AS/NZS 1768:2007 Australian/New Zealand Standard Lightning Protection” details New Zealand requirements for lightning and surge protection.

NZS 1768 is based in part on IEC 62305 series of standards. The IEC 62305 series of standard are much more detailed and prescriptive, and provide for a higher level of protection. For critical sites, it is recommended to take a hybrid approach where IEC 62305 is used, but such a way that NZS 1768 is also complied with.

It is interesting that in NZ, a popularly-used propriety protection method is often seen on the top of buildings. However, this system is not compliant with NZS 1768 or IEC 62305. This system has been sold on its “track record”, ease of design/installation and low cost. HV Power only offers standards compliant systems, that meet requirements of both standards. Many products also meet USA standards UL 1449 and NFPA.

Note that AS 3000 and associated standard provide further requirements for surge protection and equipment. Site with hazardous or explosive material have additional requirements.

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How does lightning protection work?

Lightning protection creates a preferred point for lightning to strike (avoiding strikes to sensitive rooftop equipment) using an air termination network, then conducts the energy to ground using downconductor(s) and injects the energy into a purpose designed earthing system.

In some cases, existing structure materials can be used as part of the lightning protection system, such as using reinforcing steel as downconductors. The items are referred to as “natural components”. The use of existing structure items is most applicable to situations where the lightning protection is included in the initial design and construction. For buildings where lightning protection is retrofitted, it is often difficult to use “natural components”.

There are many possible designs for air termination networks, and final selection is based on efficiency of performance, ease of installation/maintenance, cost, visual impact and compatibility with existing building materials. While the traditional lightning rod is well known, horizontal conductors, handrails, parapet flashings and conductive roofing materials may also be used.

Downconductors are selected to route the energy to ground and reduce the risk of side-flashing to nearby items. Routes are selected to reduce electromagnetic radiation and control risk of dangerous touch potentials being developed. The size and interconnection method of downconductors reduces the risk of heating and resultant structure fire during a lightning strike. For new concrete construction, the reinforcing steel within the building may be utilised.

The earthing system is designed to inject the energy into ground and reduce the risk of voltage-ground-potential-rise (step and touch potentials). Various positioning and layout options are evaluated to select the best choice.

Lightning protection systems are designed to:

• Reduce the presence of dangerous voltages (reduce step and touch potentials)
• Reduce the risk of flash-over’s (reducing the risk of the building catching fire)
• Reduce physical damage to buildings (stop holes being punctured in roofs, stop chucks of building materials being knocked out)
• Reduce the risk of equipment damage

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What is a protection zone?

To aid in the design of the lightning and surge protection system, the concepts of “zones” is used. For example zones are classified based on:

• Is the area vulnerable to a direct strike?
• Is the area exposed to the full or partial lightning current?
• Is the area exposed to the full or partial electromagnetic field?

By identifying the various zones around and within a structure, protection can be applied appropriately. For example, electrical services passing through a LPZ 0 zone will require surge protection where they enter into a LPZ 1 zone. Note that zones may not necessarily be physical boundaries of the structure.

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What is an isolated lightning protection system?

Lightning protection systems may be isolated or non-isolated.

Non-isolated systems electrically bond all conductive building materials together so they rise and fall at the same potential, eliminating potential differences and the risk of flash-over’s. This is the traditional lightning protection method.

However, with modern facilities containing a large amount of electronic equipment, and more critically, rooftop equipment (air handling units, lift motors, TV aerials and communication equipment), non-isolated systems can be difficult and costly to implement.

Isolated systems use special methods to capture the lightning strike and conduct this to ground without it contacting the structure. Isolated conductors are the main methods to achieve this. Isolated systems are ideal for:

• Highly flammable structures (grass/straw roofs)
• Locations with a high concentration of electronic equipment (communication towers)
• Structures where the cost of bonding all metallic items would be prohibitive

DEHN is a world leader in the development of isolated systems, and have a number of HVI conductors and isolated air-termination systems to cater for most applications.

Isolated systems are ideal to keep the dangerous lightning energy away from:

• Rooftop communication equipment
• Solar cells and other electrical/electronic equipment
• Explosion or gas hazard areas

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How do I select the right lightning protection system?

There is normally a wide range of options available for each situation. We recommend you contact us to discuss the application. HV Power can use our experience to guide you to the most appropriate solution.

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How does surge protection work?

Surge protection devices are non-linear voltage dependent devices that transition from high impedance state to low impedance state to divert overvoltages and overcurrent safely to ground. They are similar to a safety pressure value that stops dangerous pressures being built up in pressure vessels.

The correct selection and installation of surge protection is essential for reliable performance. Unfortunately there are a number of people selling these products with little knowledge of these issues. HV Power have specialist application knowledge to guide you.

It is important that:

• The right ratings are installed at the right locations
• That electrical safety is maintained by having the correct backup overcurrent protection
• That devices are installed in such a manner to ease inspection and replacement
• That the location and wiring to the SPD’s does not compromise the possible protection
• That surge protection is properly coordinated

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How do I select the right AC surge protection product?

AS 1768 gives guidance to the selection of surge ratings. However, this is only one of many considerations. The configuration (L-N, L-E, N-E)of the surge protection devices (SPD’s) is dependent upon location (MEN or downstream). Selection of ratings is also dependent upon the coordination method. HV Power's Easy Selection Guide gives some generic recommendations. (PDF, 1.6 MB)

We recommend you contact us to discuss your application.

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What is coordinated protection?

With surge protection designs, the normal approach to apply a large “lightning rated” surge protection device on the main service entrance. This stops energy entering the facility via the Z0/Z1 boundary. These are referred to as “Lightning Current Arrestors” (IEC 61643-11 Type 1).

Secondary coordinated protection is then installed closer to the sensitive equipment to be protected. According to IEC 61643-11 these SPD’s are Type II devices, or “Surge Arrestors”. You cannot rely on a Surge Protection Device (SPD) mounted in the main switchboard to protect equipment 10-100’s of metres away, especially when other loads in your facility may also be generating transient voltages. Having two SPD’s ensures the massive lightning current/voltage is suitably reduced so as not to damage sensitive equipment. The term "coordinated-protection" is used as these two devices must be selected to work in a coordinated fashion.

This first of this two-pronged approach diverts the bulk of the energy away from the point-of-entry to the facility, thus:

• Stopping energy from entering into building and radiating/coupling into nearby low voltage data/communication circuits
• Stopping damage to electrical distribution boards (so power is not disrupted!)
• Providing effective protection to robust downstream equipment such as heating and lights

The second of this two pronged approach, provides “fine” protection to the sensitive electronic equipment, thus:

• Protecting sensitive equipment to a suitable low voltage
• Providing backup if the point-of-entry protection is damaged
• Protecting equipment from internally generated transients

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How to avoid common mistakes

There is actually a lot of theory, technology and application knowledge required to be skilled in surge and lightning protection, and HV Power are available to shield you from this. Leave the technical stuff to us, so you can concentrate upon your business.

The common problems we encounter are:

• Surge Protection installed without due consideration of backup overcurrent requirements – a potentially dangerous situation
• Surge Protection installed ineffectively – long connecting leads reducing the performance of the products, or layouts where “unprotected” wiring runs nearby “protected” wiring, allowing cross coupling
• Forgetting that lightning transients can enter facilities by the “back door” and not putting surge protection on circuits to external cameras or car park lighting circuits for example

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How do I select the right data protection product?

It is important that:

• The right ratings are installed at the right locations
• Devices are installed in such a manner to ease inspection and replacement
• The location and wiring to the SPD’s does not compromise the possible protection
• Surge protection does not affect the signalling system
• SPD’s are simple to install (i.e. connections match those of your system)

DEHN have available several hundred “Yellow Line” SPD’s products to suit a wide range of applications. Their innovative “Life Check” provides an industry-first method of determining operational status without having to remove products from service.

Products are available for protection of:

• 4-20 mA loops
• Temperature devices (PT100, NTC, PTC)
• Process control (including Hart, ADVANT, Bitbus, CAN Bus, C Bus, Control Net, Data Highway plus, Device Net, Dupline, E Bus, Fieldbus, Genius, Interbus, KNX, LON, MODBUS, Profibus, SIGMASYS, SINEC)
• RS 485, 232, 422
• Telecoms, POTTs, ADSL, E1/T1, G703, ISDN, HSDL, SDSL, VDSL
• Ethernet 10/100/1000, POE
• Antenna coax systems (AMPs, NADAC, BWA, CATV, GSM, PCS, TV, SATV, WiMAX)
• Security Systems (sensors, cameras etc)

We recommend you contact us to discuss your application.

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Why use DEHN products?

For nearly 100 years, DEHN has been serving the industry. Initially protecting buildings and personnel from the effects of direct lightning strikes, they now also protect electrical equipment and systems from the consequences of lightning currents and voltage surges. DEHN have developed many of the innovations commonly available on the market.

As electrical power systems became more complex, the electrical loads, such as process control, computer and telecommunication systems, solid state controllers and relays become more commonplace and sensitive to the aberrations that appear on these power sources. DEHN has continued to improve and develop new products and technologies for maintaining the integrity and reliability of these more modern and more sensitive systems.

DEHN’s close relationship with installers and industry has seen the continual development of new products to improve installation and effectiveness. DEHN have literally thousands of products, so should be able to offer a solution specific to your needs!

DEHN currently employs a staff of more than 1000 engineers, technicians, craftsman and administrative personnel. It partners with companies in more than 50 countries throughout the world. DEHN heavily invests in its own research and development, as well as contributing and exchanging information with others at international technical conferences and serving on technical Standards committees, to further the knowledge and technology in the fields of lightning protection and transient voltage surge suppression. DEHN manufactures its component products under an ISO 9001 certified Quality System.

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