In previous studies on operation planning of urban district heating and cooling plants, plans for operating the instruments are formed on one hour basis. However, it is important to consider operation planning by the smaller unit of time since the load on the plants rapidly increases in the morning. On the other hand, if the unit of time for planning is too small, the computational time for obtaining operation plans becomes huge due to the increase of the number of input data for prediction and the combinatorial number of plans available. Furthermore, it is needed to take account of the cost and time of switching instruments in order to derive more practical operation plans. In this paper, we propose a heat load forecasting method in which the number of input data does not explosively increase even when more detailed plans are made. And we propose several operation planning models based on various criteria and examine the efficiency of the proposed models through the comparison of the experimental results using actual data.