| MONITOR | 2/2018 12 When investigating the LVMD 2, the measuring results showed that, compared to the limit values defined in standard DIN EN 50160, the 15th order harmonic voltage was very high (approx. 56 %) (see Figure 1). Six lifts (61.5 kW), three ventilation systems (114 kW), a smoke extraction system (19 kW) and the general safety lighting system (10 kW) were all connected to outgoing circuits on the LVMD 2. These devices were deemed to be the main causal factors of the levels of harmonic measured. However, it was no longer possible to implement the recommended installation of a monitoring system (Power Quality & Energy Measurement) with detailed residual current monitoring. Three weeks after the measurement was carried out, and with the arrival of summer temperatures, the feared fire (see Figure. 2) in the safety power supply in the basement and/ or on the associated sub-distributor on the 2nd floor Furthermore, due to the use of energy-efficient devices that contain increasingly more power elec- tronics, and that therefore distort the current char- acteristics, the characteristics curves for current and voltage are no longer linear. Consequently, with a combination of this system type and the use of installed loads such as PCs, power units, electrical charging stations, inverters or frequency converters, various system reactions such as har- monic voltages, stray currents and additional load on the neutral conductor can occur. “As a result, computer systems can be destroyed, or entire installations can get destroyed by fire”, warns graduate engineer [Diplom-Ingenieur] Jörg Steffen, who also strongly recommends a retrofit. Fig. 1 15 th order harmonic tension: Limit value is 0.5%, measured value is 0.78% "To evaluate the power quality of a shopping centre, you need to have a true r.m.s. measuring device (True RMS) ..." Measurements with the PEM735 measuring case from Bender NEWSWORTHY | BUI LDING TECHNOLOGY Harmonic voltages standardised to limit value