Plot Of Characteristics Curves for Generating Stations

Theory

Usually in case of Thermal Generating units’ Major concern is Fuel consumption per Kwh and it depicts Major part of station production costs. In defining the characteristics of steam turbine units, the following terms will be used

H = Btu per hour heat input to the unit (or MBtu/h)

F = Fuel cost times H is the p per hour (Jt/h) input to the unit for fuel

Generally, the minimum load at which a unit can operate is influenced more by the steam generator and the regenerative cycle than by the turbine.

There are three type curves used for study of characteristics of thermal generating station.

X-tics of Thermal Unit

1.     Heat Rate Curve (Input/output Curve)

The input to the unit is shown on the ordinate may be either in terms of heat energy requirements [millions of Btu per hour (MBtu/h)] or in terms of total cost per hour (Jt per hour). The output is normally the net electrical output of the unit in (MW).

In other Words, This curve shows relation of Heat consumption rate per Kwh to Load Supplied by Generating Station.

Where  

2.     Incremental Heat Rate Curve

Incremental heat rate characteristic is the slope (the derivative) of the input-output characteristic (∆H/∆P or ∆F/∆P). The data shown on this curve are in terms of Btu per kilowatt hour (or Rs per kilowatt hour) versus the net power output of the unit in megawatts. This characteristic is widely used in economic dispatching of the unit.

3.     Net Heat Rate Curve

This characteristic is H/P versus P (KW). It is proportional to the reciprocal of the usual efficiency characteristic developed for machinery.

MATLAB Program

a)    Input-Output Curve

Code

clc
clear all
disp('Plot of Characteristic Equations');
p=input('Generator Total Power Capacity (MW) = ');
x=p*[1 0.8 0.6 0.4 0.25];
Pmin=min(x);
Pmax=max(x);
P=Pmin:5:Pmax;
c=input('Value of p1(2nd Degree Coefficient) =');
b=input('Value of p2(1st Degree Coefficient) =');
a=input('Value of p3(3rd Degree Coefficient) =');
y=[c*P.^2+b*P+a];
y1=[(2*c*P)+b];
y2=[c*P+b+a*P.^-1];
subplot(1,2,1),plot(P,y,'r')
title('Input-Output Characteristics');
xlabel('Power');
ylabel('Heat rate (MBTU/hr) ');
subplot(1,2,2),plot(P,y1)
title('Incremental Heat rate Characteristics');
xlabel('Power');
ylabel('MBTU/Kwah ');
hold on
subplot(1,2,2),plot(P,y2,'g')
title('Input-Output Characteristics');
xlabel('Power');
ylabel('MBTU/Kwah');

Resulting Curves