28 Olst, Inrush peak limiters (nation-wide afterwards)

Olst station was one of the first stations where LED lighting was commissioned in 2017. It turned out that more than 20 LED fixtures were switched on one group. Each LED fixture has its own driver (electronic transformer). And those drivers have a drawback, which is a high inrush current. During the first (tens of) milliseconds, it may be so high that the circuit breaker 'sees' the inrush current as a short-circuit current and will therefore trip. The more fixtures are connected on a single circuit breaker, the larger the peak grows and the likelier the circuit breaker will trip.

Some fixture suppliers specify as a guideline that only 10 fixtures can be connected to one circuit breaker. Just like in Olst, 20 or more fixtures are connected to a single circuit breaker at many of our stations.

The solution to this problem can be found in:

– Fewer fixtures on a single circuit breaker. But that demands a lot more power cables, making it an expensive solution.

– Including an inrush peak limiter in the power circuit. An inrush peak limiter attenuates the current during the first 300 milliseconds to a value that does not trigger the circuit breaker. After that time, the inrush effect of the drivers has diminished far enough and the inrush peak limiter can pass the current unattenuated once again.

We opted for prescribing the Camtec ESB101 inrush peak limiter.

By the way, an 'old-fashioned' fuse (fuse cartridge) is less affected by this, as it has a different tripping characteristic. A modern circuit breaker is more sensitive. For stations with fuses in the switchboard and little free space in the cabinet (such as at Eindhoven Centraal and Valkenburg stations), it was decided to keep the fuses and not go down the route of the peak limiter.

Fuse cartridges are not a bad solution, apart from the fact that, once triggered, a fuse is broken and has to be replaced. Furthermore, they need to be replaced periodically as they age and the tripping current value becomes less reliable.

In the control tower at Schiphol Airport, circuit breakers are even banned because they fail too quickly when electronics are switched on, posing unnecessary risks to continuity.

Tips and conclusions:

– Always apply an inrush peak limiter to circuits containing more than 20 LED fixtures.

– To prepare for expansion, use a peak limiter on every group with LED lighting.

– The inrush peak limiter consumes around 1W. This is easily compensated for by the use of LED.

– Do not place inrush peak limiters too close to each other as they will become too hot.

– In the case of fuses, an inrush peak limiter is not necessary as long as the relay is suitable for the inrush peak and contacts do not merge.