Lightning, which is categorised into distant, nearby or direct lightning strikes, may cause transient over voltages. Even if the point of strike is several kilometres away, the energy entering the buildings via the conductors might still destroy electrical and electronic consumers. Lightning current arresters provide protection by safely conducting this high electric energy to the ground via the equipotential bonding system of the building. Transient over voltages are not only caused by lightning strikes. Switching operations in high, medium and low-voltage systems are a more frequent cause. They electromagnetically inject interferences into data lines such as those of measuring and controlling equipment. This means that failure may occur even if the conductors are not directly or galvanically connected. These interferences do not present a problem for surge protective devices, which reliably discharge these over voltages.

As with all electrical and electronic devices, components of surge protective devices are also subject to ageing. In information technology systems, faulty surge protective devices normally interrupt information transmission and the availability of the system to be protected is immediately compromised. Therefore, it is vital to monitor the status of surge protective devices to ensure protection and availability of the systems and to reduce maintenance expenditure.

Future-oriented surge protection technologies in conjunction with adequate testing and monitoring strategies are an important factor for efficiency.

Event based maintenance

This maintenance strategy accepts failure of surge protective devices. The relevant measures are only taken after the device has failed. This is therefore called event-based maintenance or in some sectors, corrective maintenance. To prevent long system downtime, it is important that surge protective devices have the following three features.

• Fail-safe

Fail: If a surge protective device is damaged by ageing or overload effects; it typically causes a short circuit and thus interruption of the signal transmission.
Safe: Although information transmission is interrupted and system availability is limited, the system is protected.

• Separable surge protective device consisting of protection module and base part

A separable surge protective device consists of a pluggable module comprising all protection components, and a base part establishing the connection between the protection module and the data lines.

• Make-before-break switch contact in the base part

If no protection module is plugged into the base part, the integrated switch contact connects the input side of the base part to the output side. Thus, data transmission is also possible without a plugged-in protection module.

Periodic inspection with LifeCheck

The surge protective devices are inspected at regular intervals to detect imminent faults, thus preventing system downtime. Surge protective devices already previously damaged are recognised and can be replaced.

Condition monitoring

The highest degree of protection and permanent availability of systems and installations is indispensable where a relatively high threat to the life or physical condition of persons and high economic risks are present (e.g. nuclear power plants, chemical plants, railway systems, air traffic control, highly modern production facilities)

The following selection criteria for testing and monitoring can be used when choosing protective measure devices:

The more complex and important companies are, the more protected and reliable should the technology be. Whatever testing and monitoring devices you will use, surge protective devices from DEHN + SÖHNE provide all the protection and thus a higher degree of availability for systems.

The market leader DEHN, a globally active family-owned electrotechnical company with more than 1600 employees worldwide, offers innovative products and solutions as well as comprehensive services in the field of surge protection, lightning protection and safety equipment. DEHN focuses on the protection of system and building technology, the transportation, telecommunication and process sector, photovoltaic systems, wind turbines, etc. The company's continuous growth is based on more than 100 years of tradition and experience as well as highest quality standards and consistent customer and market orientation throughout the world.