Years since I did it but I have a BTEC in ELECTRTCAL&Electronic engineering. Hours of fun was had with power factors and phase diagrams 😁.
The thing is though, most of that is to do with load rather than frequency. It seems to me that the national grid is normally very good at managing load but not so good at managing frequency now they have so much unregulated Green stuff coming in as it just syncs to and follows the supply its connected to.
In the past if the load went down the frequency would tend to go up because the physical load on the generators would go down so they would spin faster and vice versa.
As Drax point out they can fix that just by altering the amount of steam they use, they are effectively driving the frequency of the grid rather than following it.
.
