Performance Parameters in Power Plant are utilized to analyse the effective & efficient running of the machine while ensuring a degree of compliance with the statutory regulations. These include targeting factors like Power Generation, Economies of Power Generation, Load Curve, Load Duration Curve, Demand Factor, Diversity Factor, Load Factor, Connected Load, Maximum Demand, Average Load, Power Systems, Plant Capacity Factor and Plant Use Factor. In this article we will be covering the various performance parameters in power plant including Load Curve, Connected Load, Load Factor, Load Duration Curve & more in detail.

Variable load

The load on power station varies from time to time due to uncertain demands of the consumers and it is known as variable load on power station.

Effects of variable load

• Need of additional equipment
• Increase in production cost

 Load Curve

• The curve showing the variation of load on the power station with respect to time is known as a load curve.
• The load variations during a whole day are recorded half-hourly or hourly and are plotted against time on the graph. The curve obtained is known as daily load curve as it shows the variations of load during the day.
• The monthly load curve can be obtained from the daily load curves of that month. For this purpose average values of power over a month at different times of the day are calculated and then plotted on the graph. The monthly load curve is generally used to fix the rates of energy.
• The yearly load curve is obtained by considering the monthly load curves of that particular year. It is generally used to determine the annual load factor.

Importance of Load Curve

• The daily load curve shows the variations of load on the power station during different hours of the day
• The area under the daily load curve gives the number of units generated in the day

Units generated in a day = Area (in kWh) under daily load curve

• The highest point on the daily load curve represents the maximum demand on the station on that day.
• The area under the daily load curve divided by the total number of hours gives the average load on the station in the day.
• The ratio of the area under the load curve to the total area of rectangle in which it is contained gives the load factor.
• The load curve helps in selecting the size and number of generating units.
• The load curve helps in preparing operation schedule of the station.

Connected load: It is the sum of continuous ratings of all the equipment connected to supply system.

Maximum Demand: It is the greatest demand of load on the power station during a given period.

Average load: The average of loads occurring on the power station in a given period is known as average load or average demand.

Yearly average load = No of units (kWh) generated in a year/ 8760 hours

Demand factor

It is the ratio of maximum demand on the power station to its connected load.

Demand factor = Maximum Demand / Connected load

The value of the demand factor is usually less than 1. It is because maximum demand is always less than the connected load. The knowledge of demand factor is vital in determining the capacity of the plant equipment.

Diversity factor

The ratio of the sum of individual maximum demands to the maximum demand on power station is known as diversity factor.

• A power station supplies load to various types of consumers whose maximum demands generally do not occur at the same time. Therefore, maximum demand on the power station is always less than the sum of individual maximum demands of the consumer. Hence diversity factor is always greater than 1.
• The knowledge of diversity factor is vital in determining the capacity of the plant equipment.
• The greater the diversity factor, the lesser is the cost of generation of power. Because greater diversity factor means lesser maximum demand. Now, lower maximum demand means lower capacity of the plant which reduces the cost of the plant.

Load factor

The ratio of average load to the maximum demand during a given period is known as load factor.

Load factor = average load/maximum demand

If the plant is in operation of T hours

• The load factor may be daily load factor, monthly or annually if the period considered is a day or month or year.
• Load factor is always less than 1 because average load is smaller than maximum demand
• It plays a key role in determining the overall cost per unit generated.
• Higher the load factor of the power station, lesser will be the cost per unit generated. It is because higher load factor means lesser maximum demand. The station capacity is so selected that it must meet the maximum demand. Now, lower maximum demand means lower capacity of the plant which reduces the cost of the plant.

Plant capacity factor

It is the ratio of actual energy produced to the maximum possible energy that could have been produced during a given period.

The plant capacity factor is an indication of the reverse capacity of the plant. A power station is so designed that it has some reserve capacity for meeting the increased load demand in future. Therefore, the installed capacity of the plant is always somewhat greater than the maximum demand on the plant.

Reserve capacity = Plant capacity – Maximum demand

If the maximum demand on the plant is equal to plant capacity, then load factor and plant capacity factor will have the same value. In such case, the plant will have no reserve capacity.

Plant use factor

It is the ratio of kWh generated to the product of plant capacity and the number of hours for which the plant was in operation.

Capacity factor = Load factor × plant use factor

Load Duration Curve

When the load elements of a load curve are arranged in the order of descending magnitudes thus obtained is a load duration curve.

• The load duration curve gives the data in a more presentable form. In other words, it readily shows the number of hours during which the given load has prevailed.
• The area under load duration curve is equal to that of corresponding load curve. It gives the number of units generated in a period of time.

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