
Lightning protection systems
Lightning is a natural electrical discharge of high voltage and short duration that occurs between a cloud and the ground or within a cloud. There are different types of lightning, including staccato, forked, ribbon, and bead lightning, each with unique characteristics.
Classes of Lightning Protection Systems (LPS) are categorized into Classes I, II, III, and IV based on lightning protection levels (LPL). These classes have specific construction rules to protect structures from lightning strikes and related risks. An effective lightning protection system comprises external and internal components, such as air-termination systems, down conductor systems, earth-termination systems, separation distances systems, and lightning equipotential bonding systems.
A lightning surge occurs when there’s a rapid increase in voltage caused by lightning strikes. Surge protectors, also known as Surge Protection Devices (SPDs), are designed to safeguard electrical devices from voltage spikes. When selecting an SPD, factors like clamping voltage, discharge current capacity, load current, and line voltage need to be considered.
What is meant by Lightning?
Lightning is a natural electrical discharge of very short duration and high voltage between a cloud and the ground or within a cloud, accompanied by a bright flash and typically also thunder.
Types of cloud-to-ground lightning include staccato, forked, ribbon, and bead lightening.
Staccato lightning is a strike which is a short-duration stroke that often, but not always, appears as a single very bright flash and often has considerable branching.
Forked lightning is a name, not in formal usage, for cloud-to-ground lightning that exhibits branching of its path.
Ribbon lightning occurs in thunderstorms with high cross winds and multiple strokes. The wind will blow each successive stroke slightly to one side of the previous stroke, causing a ribbon appearance.
Bead lightning appears to break up into a string of short, bright sections. It is relatively rare.
Classes of Lightning Protection System (LPS)
Classes of LPS I, II, III and IV are defined as a set of construction rules based on the corresponding lightning protection level (LPL). Each set comprises level-dependent (e.g. radius of the rolling sphere, mesh size) and level-independent construction rules (e.g. cross-sections, materials).
Surges – underestimated risk
The function of a lightning protection system is to protect structures from fire or mechanical destruction and to prevent that persons in buildings are injured or even killed. An overall lightning protection system consists of external lightning protection (lightning protection/earthing) and internal lightning protection (surge protection).
Elements of a lightning protection system
According to the EN/IEC 62305 standard, a lightning protection system consists of the following elements:
Air-Termination System
Down Conductor System
Earth-Termination System
Separation Distances System
Lightning Equipotential Bonding System
Advantages of an external lightning protection system
Air-Termination System avoids direct striking of lightning & protect from damage of lives and facilities
Down-Conductor System discharges lightning current safely to earth
Earth-Termination System distributes lightning current in the ground
Lightning Equipotential Bonding System reduces the potential differences caused by lightning currents.
What is lightning surge?
When electric charges are built up in thunderclouds to such level that could break atmospheric insulation, an electric discharge eventually occurs between these clouds or between the clouds and the ground. Electric current reaches 20-150 kA. An abnormally high voltage generated by direct lightning discharge applied to electric power cables or communication cables at that instance is called ‘direct lightning surge’
Surge protector selection
Maximum surge voltage (clamping voltage)
Discharge current capacity
Maximum load current
Maximum line voltage
Surge Protection Device (SPD)
Surge Protection Device is an appliance or device designed to protect electrical devices from voltage spikes. A surge protector attempts to limit the voltage supplied to an electric device by either blocking or shorting to ground any unwanted voltages above a safe threshold.
Types of SPD’s
Type 1 SPD
Iimp: Impulse current
This is the peak value of a current of 10/350 µs waveform that the SPD is capable of discharging 5 times.
This is the current (50 Hz) that the SPD is capable of interrupting by itself after flashover. This current must always be greater than the prospective short-circuit current at the point of installation.
Type 2 SPD
Imax: Maximum discharge current
This is the peak value of a current of 8/20 µs waveform that the SPD is capable of discharging once.
Type 3 SPD
Uoc: Open-circuit voltage applied during class III (Type 3) tests.