During the renovation of the electrical installation in a soccer stadium, the floodlighting and emergency lighting were also replaced. There are 2 safety lights installed on each of the floodlight poles, which are intended to light up in case of emergency in order to be able to provide sufficient luminosity for evacuation of the stadium. In the event of a power failure, a battery system with inverter ensures operation.
During operation, it was found that the circuit breakers of the safety luminaires tripped even though their rated current was not reached according to the data sheet. Thus, the functionality of the system in battery mode was not guaranteed. For a more detailed investigation of the problem, PQ ENGINEERING Nosswitz GmbH was commissioned.
Figure 1 Emergency power supply for safety lighting (rectifier and batteries)
The network analysis showed that the current consumption of the luminaires for normal operation and battery operation differed greatly. While in normal operation the actual load current is shown, in inverter operation a massive superposition of the resonance current is added. The supply voltage was so distorted that the inverter did not operate stably. As the power quality measurement showed, the resonance point shifts with the connection of each luminaire. As soon as eight luminaires are powered by the battery network, a significant harmonic current flows, which heats up the circuit breakers and thus promotes premature tripping.
Figure 2 Voltages of the three phases without filter
Figure 3 Currents of the three phases without filter
A voltage-controlled active broadband filter PQE ABM represents the ideal solution for subsequent problem solving. In contrast to a conventional active filter with current measurement, the PQE ABM is able to respond to and efficiently attenuate resonances that build up with a response time of less than 20 microseconds.
The resonance point is damped in battery mode and thus the high resonance current (= harmonic current) is also reduced via the circuit breakers.
Figure 4 Voltages of the three phases with PQE ABM switched on
Figure 5 Currents of the three phases with connected PQE ABM
In both mains and battery operation, the levels of harmonic voltages are significantly reduced, and resonance effects are damped. The conditions are in accordance with the standards. The supply voltage shows the ideal course again.
Stable supply voltage in all operating states
Fully automatic operation – the filter responds directly to the voltage distortions
Very low losses of the filter, thus no additional load on the emergency power supply
Easy integration into existing plants – Only the three phases need to be connected!
Low maintenance of the filter system
Compliance with DFB and DFL requirements
As a result of this measure, the emergency lights can now be operated stably, both in normal mode and in battery mode, and a contribution is made to increasing safety in the soccer stadium.
In the sense of the 4A concept of PQ ENGINEERING the problem was analyzed, the solution was designed and delivered and supported in the after sales service – everything from one source!