Site details:
The generating units within the powerhouse comprise four horizontal-axis Francis turbines directly connected to synchronous generators. Units 1 and 2 are single-runner units with generator ratings of 2,150 kVA. Units 3 and 4 are both double-flow units (which allows for a higher turbine design speed to be achieved with a similar water flow) with generator nameplate ratings of 5,250 kVA.

Before Upgrade:
Thus, the total nameplate capacity of the four generators is 14.8 MVA generated at 2,300 V, with an actual effective capacity of approximately 12.2 MW. The operating practice for the four generating units before the upgrade has been to alternate operating duty between the units, with typically two of the four units in production at any given time. In which one of the big units runs in isochronous mode and the one of small units in droop mode. This operating practice significantly enhances system reliability by providing unit redundancy.
Load requirements had changed over the years and called for operating different combinations of the units, but the old setup did not allow to run them in a stable manner.

After Upgrade:
After upgrading the units, the customer was able to run all four units in any combination enhancing system reliability and reduces electrical and mechanical loads on the individual machines and balances total service hours among all four units.