Dust flux, Vostok ice core

Dust flux, Vostok ice core
Two dimensional phase space reconstruction of dust flux from the Vostok core over the period 186-4 ka using the time derivative method. Dust flux on the x-axis, rate of change is on the y-axis. From Gipp (2001).

Sunday, November 18, 2012

Another exciting day

Saw something I hadn't seen before (but knew was theoretically possible).

The power went out early this morning. But it wasn't completely out--my computer reported it was still charging, and the lightbulbs in the kitchen were flickering dimly. So I got out the multimeter and measured the  voltage coming out of the wall. It came in at a grand 18 V, less than one-tenth normal. But there were little transient flickers of higher voltage, so I unplugged the computer.

The power came back--sort of. Some things started to run, although the lights seemed unusually bright and the fans were spinning much faster than normal.

When I measured the voltage in one of the kitchen outlets, I measured about 370 V. Again, with transient flickers of much higher voltages. But there were other outlets only producing about 20 V.

Theoretically I knew such a thing was possible. The power coming into the building was three-phase, and many electricians here have hands-on experience without any theoretical knowledge of what they are doing, so after we had the building wired and connected to the grid, the first thing I did was to check the voltage output everywhere possible.

For three-phase power you have a ground and three active terminals. In Ghana, the voltage between the ground and any active terminal is 230-240 V (ideally--although on most days it is considerably less). The voltage across two active terminals will be around 370 V. If the house is wired properly, one-third of the outlets will run off each one of the active terminals and a ground. If the house is wired improperly, it is possible that one-third of the outlets will be run off two active terminals, giving you a voltage at that outlet of 370 V.

In our case I knew the house was wired properly. So the only explanation was that after the first power outage, the electrical workers must have connected their wiring improperly, crossing the ground with an active terminal, blowing up appliances from Bortianor to Kokrobitie.

You'd like to think that electrical utility workers would be better than that. Yes, you'd like to think that.

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