Surge protection and lightning protection

Surge protection and lightning protection

Surge protection refers to the protection of systems and electrical devices against excessively high voltage peaks caused by switching operations and lightning strikes. An effective lightning protection strategy combines internal and external lightning protection. Protect the power supplies, data, and signals in your system. Use the reliable surge protection solutions available in our various product ranges as part of your internal lightning protection strategy.

Product Family

Types of overvoltages

Overvoltages occur, for example, as a result of switching operations or lightning strikes

Types of overvoltages

Various types of overvoltages can arise in electrical and electronic systems. Depending on the cause, an overvoltage can last a few hundred microseconds (referred to as a transient overvoltage), or for hours or even days (referred to as a temporary overvoltage). Overvoltages with very high amplitudes in the kilovolt range are generally transient overvoltages, which means they have a comparatively short duration ranging from a few microseconds to several hundred microseconds.

Lightning strikes are a particular cause of transient overvoltages with high amplitudes. Direct and indirect strikes can result not only in high voltage amplitudes, but also particularly high and sometimes long current flows, which then have very serious consequences. Studies have shown that lightning strikes within a range of up to two kilometers away can cause significant damage to electrical devices and systems. Direct lightning strikes cause so-called lightning currents in the object: in the absence of lightning protection equipment, lightning currents – which have a particularly high energy content – can even cause fires, mechanical damage, and explosions in the proximity of the point of strike. If surge protection is not present, even strikes some distance away can cause fires.

Overvoltages are also caused by switching operations, such as switching large motors on and off, and by short circuits. Furthermore, even low-magnitude overvoltages can cause significant interference and defects in electronic components and devices.

Protection against damage caused by overvoltages

Protection against damage caused by overvoltages

Protection against damage caused by overvoltages with internal and external lightning protection

The external lightning protection protects a building against damage. It consists of an air termination system, a down conductor system (collectively also referred to a lightning conductor), and a grounding arrangement, and safely discharges the lightning current to ground without posing a danger to people. A building whose roof and external walls are made of reinforced concrete and metal will act as a Faraday cage. Such an arrangement will, in addition to providing protection against damage, also have a shielding effect which minimizes inductive interference inside the building. The internal lightning protection protects electrical and electronic devices and systems against excessively high voltages and the resulting damage caused by overvoltages. The internal lightning protection system consists of the equipotential bonding system and electrical insulation by maintaining a sufficient distance from the external lightning protection system. The lightning protection equipotential bonding prevents dangerous potential differences and connects all electrically conductive parts together. This is achieved through equipotential bonding lines, isolating spark gaps, and surge protective devices. Active conductors are integrated into the equipotential bonding via surge protective devices, which, in the event of a transient overvoltage, establish the equipotential bonding and protect against damage.

Protective circuit principle

Protective circuit principle

Protective circuit principle and protection concept

A protective concept for lightning and surge protection should be planned so that all cables, devices, and systems are protected. The protective circuit principle is easy to illustrate:
Draw an imaginary circle around the object you want to protect. Surge protective devices must be installed at all points where cables intersect this circle. This ensures that the area within the protective circuit is protected in such a way that conducted overvoltages are prevented.

When planning the protection concept, consider the following areas of application:

  • Power supply
  • Measurement and control technology
  • Information technology
  • Transmitters and receivers

An effective protective circuit helps ensure seamless surge protection.

Protection zone concept and lightning protection zones

The installation locations of surge protective devices within a physical structure are determined using the lightning protection zone concept from Part 4 of lightning protection standard IEC 62305 [4]. It divides a physical structure into lightning protection zones (LPZ), from outside to inside with decreasing lightning protection levels. In the external zones, only non-sensitive equipment can be used. However, sensitive equipment can also be used in the internal zones.

The individual zones are characterized and designated as follows:

LPZ 0A: unprotected zone outside of a building where direct lightning strikes are possible. The direct coupling of lightning currents in cables and the undamped magnetic field of the lightning strike can cause hazards and damage.

LPZ 0B: zone outside the building that is protected from direct lightning strikes by an air termination system, for example. The undamped magnetic field of the lightning strike and induced surge currents can cause hazards and damage.

LPZ 1: zone inside the building where high-energy overvoltages or surge currents and strong electromagnetic fields are still to be expected.

LPZ 2: zone inside a building where overvoltages or surge currents and electromagnetic fields that have already been significantly weakened are to be expected.

LPZ 3: zone inside the building where overvoltages or surge currents are expected to be only extremely low or entirely absent, and electromagnetic fields are expected to be only very weak or non-existent.

Diagram of the lightning protection levels

The four lightning protection levels in accordance with IEC 62305-1 with corresponding minimum and maximum values of lightning current amplitude

Lightning protection levels

The normative classification of lightning protection systems is split into levels I to IV. They are based on a set of lightning current parameter values with regard to probability, whereby the largest and smallest rated values in the event of naturally occurring strikes cannot be exceeded and the strikes can be safely discharged. Lightning protection level I thereby corresponds to the highest rated values and the greatest probability of capturing a strike. The values decrease accordingly, down to lightning protection level IV.

Surge protection standards

Surge protection standards

When it comes to surge protection, which standards must be observed?

National and international standards provide a guide to establishing a lightning and surge protection concept as well as the design of the individual protective devices. They differ depending on region and field of application. The overarching standard is lightning protection standard IEC 62305. It describes protective measures against lightning events and an extensive risk analysis regarding the necessity, scope, and cost-effectiveness of a protection concept.

Fields of application

Use of a surge protective device

Use of a surge protective device

Surge protection for the power supply
Our type 1+2, type 2, and type 3 surge protective devices provide effective protection for your electronic devices. From feed-in through to the end device, we provide convenient, ready-to-install solutions for all applications.

Surge protection for measurement and control technology
A large number of signals are controlled and monitored in measurement and control technology (MCR technology) applications. Our protective devices prevent interferences and damage caused by overvoltages and provide you with the ideal solution for all applications.

Surge protection for information technology
Data interfaces are particularly sensitive to overvoltages, because they operate with low signal levels and high frequencies. Use our surge protection solutions for interference-free data transmission with the same bandwidth in your IT systems.

Surge protection for transmitters and receivers
Transceiver systems are particularly susceptible to overvoltages. Antenna cables that extend beyond the building and the antennas themselves are directly exposed to atmospheric discharges. Play it safe with our powerful, coaxial surge protective devices.

Surge protection for photovoltaic systems
String combiner boxes need to be used in order to provide optimum protection for PV systems against lightning strikes and overvoltages. Our ready-to-install string combiner boxes, which can be connected immediately, are reliable system solutions that protect the inverter directly from DC and AC voltage inputs. Surge voltage couplings are discharged directly to the ground potential.

Test and monitoring devices
Phoenix Contact provides a mobile test device so that you can perform regular checks to ensure that your surge protective devices are working correctly in accordance with the requirements of IEC 62305. This precautionary check enables you to prevent machine failure.

In addition, we provide the world's first intelligent assistance system for surge protection in the field of mains protection, enabling you to monitor your systems in real time. The system monitors the state of the relevant system and determines the state of health of the surge protective device so that you can prevent a failure in good time.

Isolating spark gaps for discharging overvoltages
When overvoltages occur for a short period (e.g., due to a lightning strike), isolating spark gaps connect metallic bodies together, which must not be permanently galvanically connected during operation. For example, protect sensitive insulating flanges in pipelines against sparkover and avoid failures, downtimes, and leaks.