Effective overvoltage protection

More and more IP devices are used in outdoor applications, providing greater comfort and higher security. Powered over the data cable, they have become natural parts of the data network. Copper cables, however, that run from outside into a building, put the network at an enormous overvoltage risk which needs to be addressed.

The increasing number of IP devices in outdoor areas reflects the increased need for security, availability, and mobility in our society. IP video cameras monitor critical areas with high resolution and use the appropriate software to recognize faces and number plates. Wireless outdoor routers that work in license-free frequency bands are a cost-effective way to connect buildings and Wi-Fi outdoor access points offer  unprecedented levels of mobility and comfort through data access on the way. These devices are often powered by Power over Ethernet ofer the data cable, eliminating the need for electrical power sockets.

With all the advantages that such solutions offer, it is all too often overlooked that any metallic conductor that runs from outside into a building means an overvoltage risk that should not be underestimated.

Serious damage caused by overvoltage

Every year, more than 400,000 instances of overvoltage damage cost of over 300 million euros in Germany alone. In many cases, the insurance covers the damaged hardware. However, the time that is required to set up the equipment and the network again and hopefully to use existing backups, production losses and the costs arising from lost data are usually not covered.

Many companies are aware of the hazards of lightning and overvoltage and take appropriate action: external lightning protection outside and surge protection inside the building as well as appropriate earthing.

But what about the  data cables running into the building from outside? Very often, they have been installed after the lightning and overvoltage protection was installed and accepted and are not included in the protection concept.

And what about network protection from overvoltages that are not caused by the direct or indirect effects of lightning? Or with voltages that are induced by switching within the electric network, for example motors or fluorescent lights, or overvoltage due to grounding differences?

Overvoltage protection for data networks

Data networks operate with high-frequency, but relatively small signals. Overvoltage protection devices for data networks must be specially designed for this kind of applications, and must not interfere with the performance of the network. For future-proof systems, modern overvoltage protection modules should be used that fit in class EA links for data rates up to 10 gigabits per second. They must also be able to transmit dircect current for  the equipment that uses Power over Ethernet (PoE) according to IEEE 802 3af or Power over Ethernet Plus (PoE+) according to IEEE 802 3at.

At the same time, installation should be as easy as possible: incoming and outgoing lines should not be connected with terminals – the usual data technology RJ45 connectors should be used instead. RJ11 and RJ12 plugs of telephone and fax machines are often difficult to distinguish from RJ45 plugs by non-professionals at first glance. The RJ45 jack of the overvoltage protection module should therefore be equipped with an integrated contact overbending protection to prevent damage to the delicate outer contacts through incorrect mating.

The contacts should be designed for unplugging under load. With PoE+, up to 600 mA can nevertheless flow through the delicate RJ45 contacts. If a cable is unplugged under load, a spark can occur, which can damage the contacts. This problem can be solved by using RJ45 sockets, with which data transmission takes place in an area in no spark can occur. Secure data transmission is ensured, even in case of repeated unplugging under load.

 Kontaktberuehrungspunkte.jpgTelegärtner RJ45 connection contact points for data transmission (blue) and during unplugging (red). If the connector is unplugged under load with PoE+, a spark occurs in the red area; the area of the pin that is important for data transmission is further back (blue) and is not damaged.

RJ45-SPD_web.jpgThe RJ45-SPD Class EA overvoltage protection module offers full 10 Gigabit Ethernet performance, a patented, integrated contact overbending protection and an effective protection of contacts in the event of unplugging under load, even with Power over Ethernet Plus. It can be snapped onto a DIN rail for ease of assembly.

Overvoltage protection devices and coaxial cable systems

Overvoltage protection devices exist not only for four-pair data cables. If the components and assemblies of radio installations such as outdoor routers or wireless bridges are connected  with coaxial cables, it is recommended to use coaxial overvoltage modules to protect the sensitive electronics. The modules are inserted directly into the coaxial transmission path between the antenna and the electronics. The overvoltage protection modules must not only comply with the electrical regulations but also have to be suitable for the frequency range of the radio installation.


RF surge suppressors for coaxial cables with double-sided N connector, as used in radio installations to connect the electronics to the remote antenna.


Overvoltage protection devices are indispensable components of powerful data networks. Where IP devices like IP cameras, outdoor routers or wireless access points are used in outdoor areas, the copper data cables running into the building should be equipped with reliable overvoltage protection to protect the network from disruption and damage. The same applies to RF systems with coaxial cables between electronics and antenna. The cost of these measures is usually only a fraction of the cost of damage caused when the network and devices are not protected.