The reason why the maximum supply power is different between summer and winter is that a periodic test for the power stations is carried out in winter with less power demand in {HEAD ~ preparation} for {TAIL ~ summer} with more power demand 
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The reason why the maximum supply power is different between summer and winter is that a periodic test for the power stations is carried out in winter with less power demand in { HEAD ~ preparation } for { TAIL ~ summer } with more power demand
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH