Hello panzo,
If the station's ID is the same for the relay as it is for the source, then its as simple as setting up an interval playlist on the source and set it to 60 minutes.
However, If you need the relays to play a different ID that is a bit more complicated. Of the top of my head you can set the ondemand or fallback function on each relay to play the ID and then set a cronjob to disconect them every 60 minutes using the XML API from Centova Cast. It'll take some doing but it can be accomplished.
Hope this helps.