The two lines on the chart above show the daily voltage patterns for two separate intervals on an LV line belonging to a Victorian distribution business (Solaris). The improved curve, with lower voltage at night was probably achieved by Solaris reprogramming On Load Tap Changers (OLTC) or Line Drop Compensator (LDC) equipment at the zone substation. It seems likely that the four-night "experiment" was conducted by Solaris technical staff as a result (at least in part) of my complaint. I was never offered any technical briefing from Solaris as to how the voltage was so successfully adjusted, or why the system subsequently reverted to high-voltage mode. Please note that the data has been sorted by time-of-day, with midnight in the centre of the x-axis.
Solaris has demonstrated that it is technically possible to reduce night time voltages over a wide suburban area. This is just what should be happening every night at every zone substation in every jurisdiction of the proposed National Electricity Market.
The electricity market is a unique real-time market. Whoever controls the voltage dial has control of a considerable range of instantaneous customer demand. There is no valid technical reason why voltages for all franchise customers cannot be adjusted to average 240 volts or below (except for half of the customers during rare peak demand situations).