Electricity and Control April 2020

SAFETY OF PLANT, EQUIPMENT + PEOPLE

Holger Heckler, born in 1965, graduated from the University of Applied Sciences of Bielefeld (Germany) with a diploma in Electrical Engineering (Dipl.-Ing.). With Phoenix Contact, the focus of his work is on lightning and surge protection, electromagnetic compatibility and electrical safety. He has written scientific papers and has authored and co-authored books which have been published internationally. Holger conducts training seminars on surge protection and other technical topics in different countries. He also participates in a number of standardisation projects for German, European and international standards organisations. IEC standards - IEC 62305-4 (2010): Protection against lightning - Part 4: Electrical and electronic systems within structures - IEC 61643-11 (2011): Low-voltage surge protective devices - Part 11: Surge protective devices connected to low-voltage power distribution systems - Requirements and testing methods - IEC 61643-12 (2008): Low-voltage surge protective devices - Part 12: Surge protective devices connected to low-voltage power distribution systems - Selection and application principles - IEC TR 62066 (2002): Surge overvoltages and surge protection in low-voltage ac power systems - General basic information Summary - State-of-the-art L/N spark gaps are encapsulated, triggered, fast-acting and entirely free of follow current. - The course of the residual voltage of modern L/N spark gaps – during the conduction phase – is significantly lower than the course of the residual voltage of voltage limiting components (MOVs). - For longer-duration surges, the protection effect of modern L/N spark gaps is much better than the protection effect of voltage-limiting surge protective components (MOVs). Spark gaps are therefore the best choice for the first stage of protection – when lightning- induced surges are expected. □

where prospective short-circuit currents are negligibly low. Commercially available Type 1 N/PE spark gaps can discharge high-energy long-duration lightning currents (10/350 µs) with amplitudes of up to 50 kA or 100 kA. Gas-discharge tubes Gas-discharge tubes (GDTs) are fully encapsulated single- stage spark gaps without triggering electronics. Because of their relatively low arc-burning voltage they are not suitable for installation directly between L and N conductors. GDTs are therefore mainly installed between N and PE conductors, or in series with voltage-limiting components (that is, varistors).

Commercially available Type 1 GDTs can discharge high-energy long-duration lightning currents (10/350 µs) with amplitudes of up to 50 kA or 100 kA.

Gas-discharge tubes.

Parallel connection of a spark gap and a varistor Sometimes it is favourable to connect different kinds of surge protective components in parallel. Such surge

protective components are specially designed to be connected in parallel and the individual components work in a coordinated way (see Figure 4 ). With this combination of different surge- protective components, it's possible to achieve an optimised protection effect. Figure 4: Parallel connection of an encapsulated and triggered Type 1 spark gap and a Type 2 varistor.

Triggered Type 1 spark gaps are the best choice to divert high- energy long-duration lightning currents, and Type 2 varistors are the best choice to divert man-made short-duration switching overvoltages. A triggered Type 1 spark gap and a Type 2 varistor – connected in parallel right at the service entrance – provide a good solution for the efficient diversion and mitigation of short-duration and long-duration surges and the mitigation of man-made switching overvoltages.

Type 1 SPD with parallel connection of triggered and encapsulated Type 1 spark gaps and Type 2 varistors between L and N, for the protection of three-phase five wire systems (230/400 V ac).

For more information contact Tony Rayner at Phoenix Contact South Africa: tonyr@phoenixcontact.co.za or visit: www.phoenixcontact.com

26 Electricity + Control APRIL 2020