Tim Benson, Chair of Powerful Thinking, shares his hard won advice on energy efficient outdoor lighting for winter wonderlands. Power providers with a penchant for low energy solutions can geek out on LED lighting learning curves, dealing with power factor fluctuations, why all brands of fixtures are not created equal, and how to avoid unfortunate Winter’s Tale Exits, pursued by squirrels and rabbits…
“Much of my last two and a half months were spent on a site managing power for a lighting trail. The environs were stunning, the production team dreamy and we had devised, what we thought anyway, was a highly energy efficient power management plan.
Those of you who know your Shakespeare will be familiar with his famously challenging stage direction in A Winter’s Tale – ‘Exit, pursued by a bear’. In our case, it was more ‘Exit, pursued by squirrels and rabbits,’ as for the first time in my 20+ year career, it was the local wildlife’s newfound taste for DMX and TRS cable that left us scratching our heads when random fixtures simply stopped working.
However, another new problem also reared its ugly head and took us completely by surprise: power factor fluctuations in LED fixtures. Having carefully calculated the LX loads by area, we were surprised to see the generators working so hard. On closer inspection, we observed massively irregular power factor readings on the DSE generator panels, with L1 dropping to 0.35pf (power factor) and L3 as low as 0.18pf on occasions.
Power factor is a complex beast. Cummins define it as ‘the relationship between the active real power required to do the job (kWe) and the consumed apparent power (kVA)’. The optimal situation is where current and voltage are in phase, which makes the power factor unity (1.0pf) but this is rare, particularly in relation to LED fixtures.
The alternators in rental generators are designed to operate safely between 0.8 and 1.0pf. However, when running high volumes of fixtures such as LED floods and pars that rely on capacitors to operate, the generator’s alternator can effectively be de-rated because the excitation system becomes overloaded. This problem is further exacerbated by the fact that the fixtures are generally constantly switched on in these kinds of scenarios, so there is no let up on the pressure applied to the alternator. We also observed problems with huge returns down the Neutral line, as the capacitors would draw their full current but use only a percentage of this, merrily sending the rest back down the Neutral line.
The more we investigated these spooky readings, the more apparent it became that not all LED fixtures are equal. We observed huge variations between different brands; both in terms of build quality and performance. In the end, we had to install larger size generators to ensure that the alternator de-rating was compensated for and we were hugely fortunate that the tech team on the ground were able to support us with modifying the heavy mains plan to resolve these problems.
Whilst this project presented some interesting challenges, it was also a huge learning curve. On the surface, what looked to be a relatively stable and low energy load, turned out to be something all together more complex. My advice to anyone embarking on similar projects next festive season would be:
- If you are planning to use a variety of different lamps from different manufacturers, run fixture tests using power analysers before installing on site to ensure any power factor anomalies are identified
- Mix up the generator loadings and apply linear loads to those with high volumes of LED fixtures, this will help balance out any power factor lead and lag issues
- Monitor the power factor closely through the relevant page in the control panel menu
- And, of course, watch out for squirrels and rabbits!!! “
This guest blog originally appeared in the January 2022 Vision: 2025 newsletter. Sign up to receive monthly event sustainability news, case studies and guest blogs direct to your inbox www.vision2025.org.uk