What an SPDA is
An SPDA is the set of measures that reduces the damage caused by lightning to a structure. It does not stop lightning from striking: it provides a controlled path for the current to reach the ground and reduces the risk of fire, structural damage and danger to people.
Protection usually has two fronts. The external one conducts the lightning current to the ground. The internal one reduces the effects on electrical and electronic systems, with equipotential bonding and surge protective devices (SPDs).
The four parts of NBR 5419
ABNT NBR 5419 was published in 2015, in four parts that complement one another:
| Part | Subject |
|---|---|
| Part 1 | General principles |
| Part 2 | Risk management |
| Part 3 | Physical damage to structures and life hazard |
| Part 4 | Electrical and electronic systems within structures |
Technical standards are published and revised by ABNT, and ABNT NBR 5419 should be consulted in its current version. For this reason, every design should state the edition adopted.
Risk management: is an SPDA needed?
The decision to install an SPDA is not made by guesswork. Part 2 of the standard establishes an analysis method that considers, among other factors, the type and use of the structure, its occupancy, what is inside it and the surrounding environment. The result indicates whether protection is needed and which measure reduces the risk to a tolerable level.
When an SPDA is needed, the standard works with four protection levels, from I to IV. The level chosen guides the sizing of the system.
External SPDA: air termination, down conductors and earthing
The external system, covered in part 3, consists of three subsystems:
- Air termination: elements at the top of the structure that receive the strike, such as air terminals, rods or conductors
- Down conductors: conductors that carry the current from the air termination to the earthing
- Earthing: electrodes that disperse the current into the ground
The design defines the type, positioning and material of each element according to the protection level, and must provide for equipotential bonding of the metal parts and installations.
Equipment protection: SPDs and internal installations
Even without striking the structure, a nearby strike can cause surges in electrical, data and telecommunications networks. Part 4 covers protection measures for internal systems, such as SPDs, equipotential bonding and earthing.
This ties in with the electrical design: the SPDA and the low-voltage installation need to be designed in a coordinated way, especially distribution boards, earthing and surge protection.
Inspection and maintenance
An SPDA degrades over time: corrosion, loose connections, changes to the building and new roof installations can compromise the system. The standard provides for periodic inspection and maintenance, as well as keeping the design documentation and inspection reports.
The frequency and content of the inspection should be confirmed in the current version of the standard and in the design. At the end of each inspection, the responsible professional issues a report; inspection is a technical engineering service subject to an ART.
Checklist: what to ask for when hiring
- Risk management analysis in accordance with part 2 of the standard
- Design with plans and details of air termination, down conductors and earthing
- Descriptive specification stating the edition of the standard adopted and the protection level
- SPD and equipotential bonding design, where sensitive systems exist
- Design and execution ART registered with CREA
- Inspection report and earthing measurement at the end of the installation
- Periodic inspection plan
How EF Engenharia e Soluções works
EF Engenharia e Soluções works on electrical engineering designs and installations and issues an ART for the services it takes on. The SPDA is one of the topics that often falls within the scope of electrical designs for buildings and industrial plants.
Frequently asked questions
Are SPDA and lightning rod the same thing?
SPDA is the technical name for the complete lightning protection system. The lightning rod, in everyday language, usually refers to the air terminal at the top of the structure, which is just one part of the system.
Does every building need an SPDA?
There is no single answer. The standard requires a risk management analysis to indicate whether protection is needed. Requirements from local authorities and insurers may also apply.
How can I tell whether NBR 5419 has been updated?
Standards are revised by ABNT. Check the current edition in the ABNT catalogue before starting the design and state it in the descriptive specification.
Does an SPDA need an ART?
Yes. Design, execution and inspection are engineering services subject to an ART, under Law No. 6,496/1977.
Does the SPDA protect electronic equipment?
The external SPDA mainly protects the structure. For electronic equipment, the standard covers additional measures, such as SPDs and equipotential bonding, in part 4.
Need an SPDA design, an electrical upgrade or an inspection? Talk to EF Engenharia e Soluções.
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This content is for information only and does not replace the design, technical assessment or advice of a qualified professional. Standards may be updated; always check the version in force.