Frequency control and active power sharing among GTGs and STGs is very important and often referred to at P/f control. Implementation of DLN operation adds to the complexity of the P/f control algorithms. In order to reduce the NOx concentrations in exhaust gas, the air/gas mixture must be homogeneous. This can only be achieved when the turbine output exceeds a certain percentage of its nominal rating as a function of the air inlet temperature as shown in Fig. 5. The DLN limit and the maximum power output Pmax are both shown in % on the ordinate. The air inlet temperature is shown on the abscissa in °C. From Fig. 5 it can be seen from this typical diagram that the turbine output must generally exceed 60% of the nominal rating for DLN operation,. Since operation close to the DLN limit can result in instability, it is necessary to ensure that the turbine output is either well above or well below the DLN limit.