For many people thunder and lightning result in a mixture of fascination and concern;  fascination with the tremendous power unleashed during a storm, and concern about the dangers that it causes.

Residential and purpose-built buildings can be protected from lightning strikes with a lightning rod. However, lightning strikes that are some distance away may result in short-term surges/voltage peaks. These cause transient (temporary) leakage currents, which a residual current circuit-breaker cannot differentiate from an actual residual current. It trips.

Then the RCCB will usually have to be switched on again manually.  This is no problem in itself, but if the home-owner is on holiday or if the connected electrical devices are very sensitive or the electrical system is remote, then unwanted faulty tripping must be avoided if possible. After all, who wants to return from their holiday to defrosted ice in the freezer, to regularly have to call in a specialist for a remote charging point for electric vehicles throughout the summer or to put up with production downtimes because there has been a storm?

These problems can be avoided using short-time delayed residual current circuit-breakers. As the name suggests, they wait briefly when a residual current occurs. If it is still present after 10 milliseconds, then the RCCB trips. To put it slightly more technically: because they feature a response delay, short-time delayed residual current circuit-breakers only respond to residual currents that last longer than a half-period of the power frequency.

This short waiting time means that compliance with the tripping times required by standards is no problem since, depending on the level of the residual current, this is 40–300 milliseconds. In a nutshell, a short-time delayed residual current circuit-breaker can easily be used in the place of a standard switch.

The Doepke DFS type F residual current circuit-breaker (for mixed frequencies) and the AC-DC sensitive DFS type B and B+ are already short-time delayed and lightning-resistant. They are therefore marked with a ‘G’ on the housing. For the DFS type A, which is sensitive to pulsating currents, there is also a short-time delayed design designated with the code KV.  Doepke also offers the short-time delayed design for residual current operated circuit-breakers with integral overcurrent protection and arc-fault detection devices (AFDD).

Incidentally, the short-time delay is not only useful in preventing unwanted tripping during storms, but also in the event of high inrush currents for lights, IT systems, neon lamps and switched-mode power supplies.
Lightning-resistant and short-time delayed. The mixed frequency sensitive DFS type F reliably protects homes and offices from dangerous residual currents. It is largely immune to brief surge currents during storms or due to high inrush currents.