Firefighters switch amd 4

An interesting tack! I have heard musings in the fire safety sector for many years about the desire for FRS to disconnect all sorts of equipment in the event of a fire situation. Things like PV, battery and EV installations getting specific attention. I am aware of several installations where the EV supplies are disconnected via the fire alarm panel. In ROI, emergency isolation is required for PV systems such that the supply from the PV modules is interrupted as close to the units as possible, with the system interlinked with the mains so that interruption of the main supply to the building also interrupts the supply from the modules and then re-connects when mains is restored. This would allow firefighters to operate the main switch to the building and be assured that the output from the modules would also be disconnected at a point as close to them as possible. Of course, which main switch are we talking about? Many installations, particularly in the domestic side might have several.

I know that there are a number of best practice guides, some from the insurance providers who, no doubt, will continue to require installations to go above and beyond what 7671 might demand. I guess those involved in design have to keep a close eye on developments in order to avoid expensive mistakes. 

Parents
  • In ROI, emergency isolation is required for PV systems such that the supply from the PV modules is interrupted as close to the units as possible, with the system interlinked with the mains so that interruption of the main supply to the building also interrupts the supply from the modules and then re-connects when mains is restored.

    Sounds like an interesting problem. Presumably the fire/main switch can't act on the PV cables directly, as that would leave them live al the way from the roof to the switch, so we're looking at some kind of remote control. I guess a active-to-switch-off approach (e.g. shunt trip on a circuit breaker) wouldn't fail safe (either because of a more general mains fail or because the interconnecting cable had burned though) so we'd be looking more like a contactor arrangement held closed by the mains (and spring open when switched off or loss of mains) - but you'd need a contactor with pretty good insulation to guarantee not only mains didn't sneak onto the d.c. side, but d.c. (at maybe 300 or 400V) couldn't get back into the mains (and upset non B-type RCDs not to mention DNO workers).

       - Andy.

Reply
  • In ROI, emergency isolation is required for PV systems such that the supply from the PV modules is interrupted as close to the units as possible, with the system interlinked with the mains so that interruption of the main supply to the building also interrupts the supply from the modules and then re-connects when mains is restored.

    Sounds like an interesting problem. Presumably the fire/main switch can't act on the PV cables directly, as that would leave them live al the way from the roof to the switch, so we're looking at some kind of remote control. I guess a active-to-switch-off approach (e.g. shunt trip on a circuit breaker) wouldn't fail safe (either because of a more general mains fail or because the interconnecting cable had burned though) so we'd be looking more like a contactor arrangement held closed by the mains (and spring open when switched off or loss of mains) - but you'd need a contactor with pretty good insulation to guarantee not only mains didn't sneak onto the d.c. side, but d.c. (at maybe 300 or 400V) couldn't get back into the mains (and upset non B-type RCDs not to mention DNO workers).

       - Andy.

Children
  • At work where we sometimes switch very high voltages indeed, we use compressed air to do it - loss of pressure causes a safe fail to power off, but there is no EMC concern .
    But to isolate just a kV or so of DC and keep it off the primary side using conventional contactor type methods, or even opto-isolator  solid state relay methods, is now quite practical with modern devices (though quite dear if you want lots of amps and lots of volts)

    If DC and mains are gettting entangled that will be more of a poor assembly matter.

    Mike.