Important Points about Economics of Power Generation and Interconnected System
- Connected load : Sum of continuous ratings of the machines and equipments corrected to the supply.
- Firm power : Theoretical value of power which a hydro power plant is supposed to produce throughout a year.
- Cold reserve : It is the generating capacity which is available for service but not in operation.
- Hot reserve : Reserve generating capacity which is available in operation but not.n service
- Spinning reserve : Generating capacity which is connected to the bus and is ready to take load
- Load curve : The load curve is a graph which represents loads on the generating station recorded to interval of half hour or hour against the time in chronological order.
- Load duration curve : The ordinates represent the maximum load and the decreasing loads we represented to the right in descending order area under load duration curve represents total number of units consumed in that time.
- Integrated duration curve : The curve representing total number of units generated to the given demand in kW is called as integrated duration curve.
- Average demand = kWH delivered by the station in 24 to day / 24 hours in a day
- Maximum demand : It is equal to maximum load on the station.
- Demand factor : Maximum demand factor = Average demand / Maximum demand.
- Plant capacity factor = Average demand on the station /Maximum Installed capacity of the station.
- Plant use factor = Station output in kWH / ∑ (kW1)xH1 + (kW2)xH2
+ (kW3)xH3 where kW1, kW2 etc. are kilowatt rating of each generator and H1, H2… are number of hours, for which they have been worked. - Diversity factor = Sum of maximum demands of each category / Maximum demand of the station
- Load factor = Average demand / Maximum demand
- Plant load factor = Station output in kWH / ∑ (Kw1)xH1 + (Kw2)XH2
+…… - Combined operation of power stations interconnected power system is required to direct different stations to operate for their best possible economic operation.
Advantages of Interconnection :
- Increased reliability of supply
- Reduction in total installed capacity
- Economic operation
- Base load and Peak load : Base load remains constant during 24 hrs of the day, while peat leads are momentary load, occurring for short duration of a day.
- Fixed cost : The cost of plant i.e. capital investment, interest on loans, tax paid, labour charges, salary of stat come under fixed charges.
- Variable cost : It depends upon the load supplied, losses in machines, transmission etc.
Load sharing and transfer of load between stations : It is carried out by
(a) Angular displacement between stations.
(b) Quadrature voltage boost.
(c) In-phase voltage boost.
Functions of power controller or load dispatcher :
- Loading of generating stations.
- Loading of units within generating stations.
- Control of system voltage and reactive power flow.
- Control of system frequency and active power flow.
- Loading of various interconnectors and transfer of power from one system to another.
- Maintaining continuity of service.
The centralized control, supervises the following :
- Reliability of service
- Quality of service
- Economy of production