[Info-vax] VMS and the Internet of Things (IoT)

[John E. Malmberg]

On 9/13/2016 6:14 AM, Chris wrote:
> On 09/12/16 18:55, johnwallace4 at yahoo.co.uk wrote:
>
>> The smart meters being rolled out in the UK are required to
>> have, as well as the remote metering stuff, a remotely
>> controlled power-off switch. No UK law currently permits use
>> of this off switch, but that can be changed at a few hours
>> notice when the state of emergency arises.
>
> Forgot to mention that, but does raise an interesting
> question from an engineering pov. They need to be able to
> switch a 60-100 amp load, the usual incoming fuse rating
> here in the uk. They can either use an electromechanical
> contactor / relay, or a solid state switch. A relay of
> that rating is physically bulky, with large silver or silver
> alloy contacts That solution would drop insignificant
> voltage, but would need to be always on, wasting ~10Va each.

There are electro-mechanical switching systems that consume no
power in their steady state.  It increases the cost of the switch slightly.

One solenoid turns the switch on, one turns it off.

In the case of something just used for an emergency power off, you only 
need a solenoid to turn it off and have a human operated reset switch 
turn it back on.

Regards,
-John
wb8tyw at qsl_network