Site Records

Invergarry Power Station

OS Grid Ref: NH 31916 013025
Date opened: 1957
Date closed : Operational

Invergarry power station, hidden away by the A82:

Looking down the access road to Invergarry power station:

An archive view of Invergarry immediately after completion, taken from Loch Oich, looking at the tailrace outfall:

This drawing clearly illustrates the general arrangement of the power station:

Walking through the entrance doors, there's a large open loading bay, with just the exciter of the alternator standing above floor level. Invergarry is mostly underground; everything below the windows and crane rail is below ground level:

Looking back across the loading bay from the area adjacent to the alternator. The blue object to the right is the cover for the small alternator at Loyne dam; it was just being stored at Invergarry whilst Loyne was being refurbished:

Looking down from the above viewpoint to turbine floor level:

On the turbine floor, looking back up at the alternator and loading bay. The doorway on the bottom left below the stair leads through to the inlet valve chamber. The black square beneath my feet is the access hatch to the relief valve:

The above picture was taken post-refurbishment. This image, taken during refurbishment back in 2003, shows the same area. The blue ventilation ductwork is all new:

For comparison, here's an archive shot of the alternator as built:

Another refurbishment picture: the alternator rotor removed:

The refurbishment provided the chance to see parts of the station that are normally inaccessible. Here we're looking down the axis of the disassembled machine. Past the stator windings (covered with protective plastic sheeting), through the white-painted alternator support structure, to the turbine spiral casing and the start of the draft tube (blue painted):

Closeup of the spiral casing:

Inside the spiral casing:

Inside the spiral casing, with Your Intrepid Correspondant giving scale:

Inside the spiral casing, looking towards the relief valve (which would normally be where the scaffolding is):

Turning round 180 degrees from the above shot, looking upstream to the (closed) MIV:

In the valve chamber, looking at the MIV from the outside:

Also in the MIV chamber is the access passage to the draft tube. Here the watertight door is open and the draft tube (normally full of water) is full of scaffolding:

From the draft tube, a short but large tailrace tunnel runs under the A82 and discharges into Loch Oich, which at this point is little more than a wide river. Normally full to the roof with water, the refurbishment provided a chance to fully explore it. This image is looking at the outlet to the tailrace - the big steel stoplog gates are in place, holding back the river water. Note the scaffold tower on the extreme left, giving access to the tailrace:

Turning left from the above viewpoint, the exit of the tailrace tunnel itself. It's normally totally submerged - see the obvious waterline on the concrete. Next we descend the scaffold tower...:

...and look into the tunnel itself. Short, but large:

Your Intrepid Correspondant gives an idea of scale. The large blue-painted area in the roof is the relief valve discharge duct. The relief valve itself is removed for refurbishment, so you can see through to the interior of the power station (with ladder etc.) and the end of the spiral casing where the relief valve is mounted. (What is a relief valve for? To relieve transient overpressure conditions which can arise in the spiral casing under certain flow and surge situations, such as when load is shed rapidly) The blue area behind me is the bottom of the draft tube:

Closeup of the draft tube bottom and splitter wall:

Standing in the very bottom of the draft tube, looking back up the tailrace, past the splitter wall:

Words and images © 2006 Michael J. Ross