Written by Mark Lloyd, Product Marketing Manager, Power Supplies and Surge Protection

A few months back, I blogged that we had developed and released a complete family of new Surge Protection Devices specifically for Measurement Control and Regulation or MCR applications. In other words, protecting signal lines. The new range, called Termitrab Complete (henceforward referred to as TTC) was officially unveiled at The Hannover Fair this year, and despite the family not even having been on the market for a year, I am reliably informed that there are already an additional 30+ new articles in planning to be released in 2018. But that is for a future blog.

While protecting power systems from transient surges is relatively well established, I still detect a bit more reluctance to accept that signal lines also need to be protected.

So, why would you need to protect signal lines? Well, lightning discharges during storms are a frequent cause of transient surge voltages and even remote lightning strikes can have an effect on electronics due to the rise in potential in the ground due to the earth resistance and the lightning current. This increase in potential continues via the grounding system and the equipotential bonding conductors and can particularly damage the insulation of devices and cables. As well as that, the electromagnetic field produced by lightning can and does affect signal lines by induction and so components such as field instruments connected by cables laid over long distances in open spaces are particularly at risk. Even cables within buildings can be affected and ultimately whether SPD’s are fitted to signal lines is a decision based upon a financial consideration. Can the end user afford to lose an instrument, or an i/o card and the resultant downtime. It has to be said that it is not just lightning but also inductive and capacitive switching processes that can also lead to coupling of unwanted transients on signal lines.

In all cases of unwanted transients surge protection for MCR applications increases reliability and system availability and is now considered part of an innovative system.

Where Phoenix Contact is leading the market is by providing surge protection devices that offer more than just surge protection.

So what do I mean by that? Well my colleague Scott Mulholland won’t like this, but SPD’s for signal protection are more and more being used as fully fledged terminal blocks in cable distribution cabinets and marshalling cabinets. (I should have mentioned Scott looks after our range of terminal blocks.)

A space-saving, compact design is one of the strongest trends in process technology as you would expect and it is not uncommon for several thousand signals terminating in high-density marshalling cabinets. TTC now makes it possible to connect two signal conductors on an overall width of just 3.5 mm, thanks to its extremely narrow versions. As a result, on one meter of installation width, 572 signal conductors can protect against surge voltages.

Designed for Maintenance.

TTC includes versions with additional functions to provide support during maintenance and scheduled shut downs. Integrated knife disconnection allows separation of signals from the controller side and field side which allows loop resistance testing directly on the terminals of the SPD.  Because surge protection devices need to be tested at regular intervals there are pluggable versions. The plug components house the voltage-limiting components, and removal of the plug has no effect on the system availability while it is being tested. We even have a piece of test equipment called the Checkmaster 2, which can be purchased outright or rented whenever testing is required.

Finally, as if that isn’t enough some products within the TTC product range also offer integrated overload protection. If the protective function is triggered, this can be signalled via an integrated status indicator on the devices. One step further is the possibility to monitor the status of up to 40 surge arresters using the remote signalling modules which are installed at each end of a row of SPD’s. Any resulting error status can be forwarded to subsequent systems via a floating contact — consequently monitoring can be easily integrated into a control system.

So in summary, TTC offers a comprehensive range of products for the protection of signal circuits in process technology that goes far beyond basic surge protection requirements, including overload protection, status indication, and optional remote signalling. The market leading minimal overall width not only saves space in large systems, but also drastically reduces the number of control cabinets that are required in larger applications.

Discover more about TERMITRAB here

For more information on Termitrab or Surge Protection, contact Mark Lloyd on mlloyd@phoenixcontact.com