Modern power analyzers cover the frequency range above the classical harmonics up to 2.5 kHz, while the measurement of supraharmonics is simplified with the universal broadband module PQE UBM from PQ ENGINEERING.
Our new case study shows how resonances can be controlled even in unstable island grids.
The active broadband filter ABM is THE tool for resonance damping and supraharmonic compensation.
Emergency lighting must work – even in the event of a power failure
Sports stadiums must have a backup power supply system that maintains the operation of safety-related systems and equipment in the event of a power failure. This is particularly important for lighting and floodlighting systems when they serve as emergency lighting. Emergency lighting must function under all circumstances. Especially in an emergency, fuses must not blow. This case study demonstrates the high voltage distortion that can occur with modern ballasts when powered by an emergency battery system. Increased currents caused by resonance lead to a fuse blowing. An active broadband filter eliminates the interference and protects the emergency lighting.
Task
During the renovation of the electrical installation in a football stadium, the floodlights and emergency lighting were also replaced. Two emergency lights are installed on each floodlight mast, designed to illuminate in an emergency and provide sufficient light for evacuating the stadium. In the event of a power failure, a battery system with an inverter ensures operation.
During operation, it became apparent that the circuit breakers of the emergency lights were tripping, even though their rated current was not being reached according to the data sheet. Thus, the functionality of the system in battery mode was not guaranteed. PQ ENGINEERING Nosswitz GmbH was commissioned to conduct a more detailed investigation into the problem.
Figure 1: Emergency power supply for emergency lighting (rectifier and batteries)
The grid analysis revealed that the current consumption of the lights differs significantly between normal operation and battery operation. While the actual load current is shown in normal operation, a massive resonance current is added during inverter operation. The supply voltage was so distorted that the inverter was not operating stably. As the power quality measurement showed, the resonance point shifts as each light is connected. As soon as eight lights are powered from the battery grid, a significant harmonic current flows, which heats 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
Solution
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 react to oscillating resonances with a response time of less than 20 microseconds and to dampen them efficiently.
The resonance point is dampened during battery operation and thus the high resonance current (= harmonic current) via the circuit breakers is also reduced.
Figure 4: Voltages of the three phases with PQE ABM switched on
Figure 5: Currents of the three phases with PQE ABM switched on
In both mains and battery operation, the levels of harmonic voltages are significantly reduced and resonance effects are dampened. Standard-compliant conditions are present, and the supply voltage once again exhibits its ideal curve.
Advantages
- Stable supply voltage in all operating conditions
- Fully automatic operation – The filter reacts directly to the voltage distortion
- Very low losses of the filter, thus no additional load on the emergency power supply
- Easy integration into existing systems – only the three phases need to be connected!
- Low maintenance of the filter system
- Compliance with the requirements of the DFB and DFL
This measure now allows the emergency lights to operate stably both in normal operation and in battery operation, thus contributing to increasing safety in the football stadium.
In keeping with PQ ENGINEERING's 4A concept, the problem was analyzed, the solution was designed and delivered, and after-sales service was provided – all from a single source!
