Load factor and demand factor

Thermal Power Station

1. ELECTRICAL POWER GENERATION Load curve and Important terms By D. N. Thakkar RCTI, Ahmedabad

2. Connected load The sum of continuous ratings of all the electrical equipments connected to the supply system is called the connected load

3. Demand Factor. T he word “demand” itself says the meaning of Demand Factor. Demand Factor = Maximum demand / Total connected load For example, an over sized motor 20 Kw drives a constant 15 Kw load whenever it is ON. The motor demand factor is then 15/20 =0.75= 75 %. Demand Factor is express as a percentage (%) or in a ratio Demand factor is always < =1 . The lower the demand factor, the less system capacity required to serve the connected load.

4. Load factor Load Factor = Actual Load / Full Load OR Load Factor = Area under the curve / Area of the rectangle OR Load Factor = Units generated / (Maximum demand x hours)

5. Load factor It is the ratio of actual kilowatt-Hours used in a given period, divided by the total possible kilowatt -hours that could have been used in the same period at the peak KW level. Load Factor = ( energy (kWh per month) ) / (  peak demand (kW) x hours/month ) The Load factor is always <=1.

6. Load factor Higher the load factor is GOOD and it will more Output of Plan, lesser the cost per unit which means an electricity generator can sell more electricity at a higher spark spread, Fixed costs are spread over more kWh of output. A power plant may be highly efficient at High load factors. Low load factor is a BED.  A low load factor will use electricity inefficiently relative to what we could be if we were controlling our peak demand. A power plant may be less efficient at low load factors.

7. Connected load factor Connected load factor = Average load / connected load = (Average demand / Maximum demand) x (Maximum demand / connected load) = Load factor x Demand factor

8. Diversity factor Diversity Factor = Sum of Individual Maximum Demands / Maximum Demand of the System. The diversity factor is always >= 1.

9. Coincidence factor The reciprocal of diversity factor is coincidence factor Coincidence factor = Maximum demand / Sum of individual maximum demands The Coincidence Factor is always <=1.

10. Load diversity Load diversity is the difference of sum of individual maximum demands of two or more consumers and their combined maximum demand

11. Loss factor Loss factor = Average power loss / Power loss at peak load

12. Plant capacity factor Plant capacity factor = Average demand / Installed plant capacity OR Plant capacity factor = Units generated in a year / Installed plant capacity x 8760

13. Utilization factor Utilization factor = Maximum demand / Plant capacity

14. Plant use factor Plant use factor = Units generated / ∑kWh = Units generated / kW 1 h 1 +kW 2 h 2 +….

15. Load curve Load curve is the variation of load with time on a Power Station. As the load on a Power Station never remain constant rather it varies time to time, these variations in load is plotted on half hourly or hourly basis for the whole day. The curve thus obtained is known as Daily Load Curve.

16. Importance of Load Curve From the daily load curve we can have insight of load at different time for a day. The area under the daily load curve gives the total units of electric energy generated.           Units Generated / day = Area under the daily Load Curve in kW The peak point on the daily load curve gives the highest demand on the Power Station for that day. The average load per day on the Power Station can be calculated using the daily load curve. Average load = Area under the daily Load Curve (kWh)/ 24 hrs. Load curve helps in deciding the size and number of Generating Units. Load Factor = Avg. Load / maximum Load =  Avg. Load x24 / 24xmaximum Load                    = Area under daily Load Curve/Area of Rectangle having Daily Load Curve Load curve helps in the preparing the operation schedule of the generating units.

17. Load Duration Curve Load Duration Curve is the plot of Load versus time duration for which that load was persisting.

18. Base load & Peak load Base load  is the minimum level of  electricity demand  required over a period of 24 hours. It is needed to provide  power  to components that keep running at all times (also referred as continuous  load ).  Peak load  is the time of high  demand .

19. Base load & Peak load

20. Base load & Peak load

21. Characteristics of Base load station Operating throughout the year Load factor is high Efficiency is high Cost of unit generation is less Capital cost is high Capacity is high Difficult to start and stop

22. TPS in Gujarat