Back in 1994, a landslip at an opencast site in Lanarkshire caused a pylon to collapse. The upshot was, it took STV and C4 off air in Central Scotland for over 3 hours.
The basics were, STV was static, C4 was black and grey lines. BBC1 and BBC2 were off air, and returned in a minute. STV returned just after 6pm, initially showing films of scottish scenes with music and their logo in the corner. Eventually, a short Scotland Today was put on air, followed by a programme, and then another short Scotland Today. Both showed scenes from the landslip.
www.heraldscotland.com
Below is a copy of a post I put on the old TV Forum about the incident.
I posted this query onto the History of Scottish Television Facebook page, and Tony Currie, and others, have filled me in on some details.
The most important things are, firstly, if all four channels to Blackhill lost power, the BBC chain was more resilient. In addition, BBC Scotland have back up generators, which meant that they could continue transmitting. There's a reason I use that word, as opposed to broadcasting, which will become clear shortly. The BBC back up generators took a wee bit to start up, which would explain why BBC1 and BBC2 were off air for a minute or so, before coming back on.
With regards to STV and Channel 4, Robert Lyon Syme, on that facebook group, provided an explanation, which is quoted below:
"There were two power feeds to Blackhill, the main and auxilliary both going on seperate loops to come into the transmitter station from different directions. Unfortunately the failure occurred at the transformer junction point where the feed split into main and reserve routes. Unfortunately as a consequence all power was lost to both feeds."
Another member, Jim Keddie, who worked at STV, pointed out that as the power feed to the transmitter station was down, there was no point in STV trying to continue broadcasting, nobody was going to see it! Cowcaddens was still operational, power was fine, it was just the power to the transmitter, was not.
With regards to the post above, mentioning C4 being fine, when I got home from school, C4 was off air. On STV it was static, wheras on C4 we had black and grey lines moving up, but no picture. Bear in mind we're served by Craigkelly, so C4 could've taken longer to be restored than at Blackhill.
With regards to Steve in Pudseys question about why the filler material was played for so long, one theory I can think of is, once the power was restored on both circuits to Blackhill, STV decided to play filler material, as a sort of "test". What I'm meaning is, the electricity board, Scottish Power, would've still been monitoring the power supply, in case another fault occurred, causing loss of picture again. STV played out the filler material, until Scottish Power were satisfied that the supply was back to normal.
END OF TV FORUM POST
The basics are this. STV were able to broadcast from Cowcaddens, but they couldn't transmit, as there was power to the STV feeds at the transmitter. The BBC would also have had the RBS system in place.
One question I would ask is, had STV, during that period, been broadcasting a programme to network, say a sports quiz, and the issue above occurred, I imagine STV would still have been able to broadcast it to network with a clean feed, as it was only the feed to Blackhill which was affected, and other ITV companies, such as Tyne Tees, would have been getting a clean feed from Cowcaddens?