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This close-up shows the bare terminals of each of the batteries, so they are no longer connected. But I certainly wouldn’t recommend touching one.

Why would Pyestock require this battery store? It’s far too small to run the site. My only suggestions would be for cold starting the turbine generator or for running the telephone system during a power cut.

Detail of the battery room.
23|05|07 © Simon Cornwell 2007

"The battery room might have had the functions you suggest, but it is much more likely that it was to drive the switchgear. The original switchgear would have been Oil-filled Circuit Breakers (OCBs). The will be rated to interrupt 200 A at 11kV in normal service, and possibly interrupting 10 to 50 kA in fault conditions. Yes, the switchgear will have been rated to interrupt 50 thousand amps at 11 thousand volts in an emergency. These things have big springs that open or close the contacts in the shortest possible time, because the resulting electric arc will cause the oil to explode if not extinguished promptly. Because of the risk it is preferred to operate these remotely if possible, hence the control room. The spring must be wound up between operations, and each breaker would have a motor that did this. The batteries would have provided power to do this in an emergency. More importantly the batteries provided a source of power to trip the breakers in an emergency and make sure that the 50 kA fault condition only lasted a few milliseconds so major damage was not caused."

"Breakers are used instead of fuses because 1. You need to open them as part of managing the network. 2. You can programme all sorts of current/time curves and voltage/time curves in to the protection relays, and get much better fault protection, a fuse is a fairly primitive device in comparison. But there must be power to the protection relays for it all to work, which is what the batteries were for in the last resort."

"In fact the standard way of identifying a buried high voltage cable prior to working on it is to "spike" it. You've checked the records, and you think you've got the right cable. You then clamp on a pyrotechnic chisel called a spiking gun onto the cable and trigger it by pulling the lanyard from a safe distance away. If you've got the correct cable nothing happens. If you have made a mistake and got an energised cable then the three phases will all be shorted to earth, causing that 50kA fault current. You RELY on the switchgear to successfully interrupt that current before damage occurs anywhere else apart from at the spiking gun." - Steve Dewey