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. Continue reading →