OT: Aerials on substations

[sm_jamieson]

Round here (West Midlands) lots of the power distribution substations are having yagi array style aerials fitted (look just like TV aerials). Anyone know what these are being used for ?

[Harry Bloomfield]

sm_jamieson used his keyboard to write :

Probably telemetry.

[Bill Wright]

What's always puzzled me is that some of these aerials appear to be narrowband and tuned for approx 600MHz, where there isn't an allocation for that sort of thing.

Bill

[Robin]

I was told they need to find new ways to be sure of disconnecting fast enough when BT stop relying on copper wire. Seems to be supported by eg

[BobH]

When I was a serious Radio Ham operator I and many others used Yagi ariels forsending and receiving the signal from a specified direction.

[Huge]

I suspect he knows that. I also suspect that the query is more towards what the nature of the signals might be, rather than the direction they are going in.

[Brian Gaff]

I am beginning to think that allocations are being ignored most of the time. Lots of strange transmissions about all over the place that seem not to agree with the definition of the allocation. I suspect that Offcom are issuing NOVs all over the place to allow uses other than agreed to. NOV Notice of Variation.

Brian

[Brian Gaff]

Yes, but what signals. People are not in these locations normally so it has to be part of some kind of automated system. I suspect that it is indeed telementry of some kind for diagnostics and as somone else said, disconnection etc. Very little new copper is being put down these days.

Digital systems suffer from latency.

Brian

[Brian Gaff]

Well I'm not in his area, but I do have a very wide band scanning radio here. 100khz to 2Ghz with no gaps, so if sonone comes up with a frequency I can go look there, but if its just data, its not going to prove much. Brian

[John Williamson]

Depending on the application, that might not be important. For instance, waiting a few seconds for a fault report to get to HQ is only a small part of the time needed to get that fault fixed, so reporting at a few baud would be adequate. A delay of a second or more when resetting a remote circuit breaker could even be beneficial in some cases.

There are some very narrow band systems in use for remote weather stations that have so little transmitter power available that it takes well over a second to transmit a single bit.

It's not that long ago that ATMs used 300 baud lines to talk to the bank mainframes.

[Robin]

Brian was spot on about latency according to the link I posted.

While a delay before resetting a circuit breaker may be beneficial, a delay before breaking the circuit would not. They claim the power network needs to respond in less than 70 milliseconds which BT's network won't be able to guarantee.

[John Williamson]

Nor would most radio links, come to that. It would take a lot of transmitter power at both ends of the link to transmit a code to a remote beaker and verify things that quickly. I'd expect a breaker to trip under local control in an emergency, then phone home to say what had happened.

Under manual control, you're limited to taking a second or so by human reaction speed.

[mick]

From a controls designer perspective, you (virtually) never rely on anything such as radio or even PLC software for breaker tripping. It's hard-wired if at all possible.

Telemetry from pumping stations will include such things as pump(s) running/tripped status and water level. Probably not much else. There's probably no remote control because that leads to lazy "engineers" who just press the reset button instead of going to site and finding out what caused the fault.

[mick]

oops - I missed that the OP was on about subs in particular. :)

My comments are similar, but there will be more monitoring and probably a degree of remote control. They will probably be watching transformer temperatures and switchgear status. Once again, tripping is hard-wired and from its own tripping battery, usually.

[John Williamson]

Which is the way I heard about such systems being designed. I can't honestly think of a way to *guarantee* a 70 millisecond trip time if it is controlled from a remote location, other than, maybe, a dedicated wire. And even then, it'd not be easy if the wire was more than a few hundred yards long.

[mick]

Under fault conditions they aim to clear the fault in less than half a cycle - 10ms. Sometimes a lot less. :)

[tony sayer]

Telemetry and scanning telemetry have been around since, well for many years. They use, or used to use, maybe still do around the 457 Odd MHz area. I rather doubt Ofcom have reallocated any of TV band 4 and or 5 as we know if but I suppose they might if they gave them enough loot for the frequency;!..

Round here in Cambridge the Gas company have used appx 453 MHz for telemetry for many years too now, and as far as I'm aware they still do as does the water company.

They will, as others have commented, use multi element Yagi UHF aerials as they are in effect point to point links normally using Vertical polarisation 'tho not always..

I do know that our local water co have started using 5.8 Ghz for point to point comms in some locations.

[tony sayer]

In article , Brian Gaff scribeth thus

Sure your scanner isn't getting overloaded and responding to things it didna oughta;?....

[tony sayer]

Why do you say that, does the speed of radio transmission alter with power;?...

Sometimes..

Indeed or longer...

[tony sayer]

In article , Robin scribeth thus

It may well be as much to do with cost and reliability;)

Heres an article from Simoco formerly Pye Philips radio , look under Western Power of a utility who have now gone back to their own radio network the mobbie ones not being as good as sometimes cracked up to be...