Subject Re: beginappend() Problem Fixed From Mervyn Bick <invalid@invalid.invalid> Date Tue, 11 Jul 2023 10:34:46 +0200 Newsgroups dbase.getting-started On 2023/07/10 21:40, Tom wrote: > Hi Mervyn, > > Out of curiosity, I notice on your chart there are several examples > where power off times overlap. Is this correct? > > Lower chart: > Monday: > Line 2: > Power off 6:00 to 8:30 am > Next line down: > Power off 8:00 to 10:30 am > > Must be really dark between 8:00 and 8:30 am :-) :-) Load shedding is scheduled in 2hour slots.  At up to level 4 no area will be off for more than 3 2hour slots in 24 hours.  If power has been off for more than an hour it is almost inevitable that more load will be switched back on than was shed.  This is because water heaters normally switch on for a few minutes every so often to replace heat losses. After an hour it almost a cast iron certainty that the thermostat in every water heater in the area has switched on. To lessen the "bump" on the system, which does drop dramatically as water heaters switch off, load is restored a section at a time in the area and an extra 30 minutes is added to each slot for this.  As an example, this morning we were off at 06:00 and the power came back at 08:02.  On occasion though power has only come back close to the 30 minute mark as City Power tries to spread the burden. Once the load shed level is higher than 4, consecutive slots, resulting in up to 4 hours and 30 minutes without power, can be allocated. The screen shot attached to the previous message shows two versions of the program.  The old version at the bottom shows the actual slots.  One needs to apply one's mind to determine if any outage will be for 4 hours and if the 4hour slot spans midnight.  The top version shows consecutive slots combined into 1 4hour slot with the appropriate start and end times combined with a bit of colour coding.  One can immediately see which slots are 2 hours and which are 4 hours. Initially I showed the actual start and end times where a 4 hour slot is centered on midnight.  I then changed to only showing the times which fell within the actual day.  The jury is still out on which is preferable. Combining slots and adjusting start and end times is done in a Firebird stored procedure.  To do this using .dbf tables would mean either creating a temporary table or using an arrayRowset object. Mervyn.