LOAD CURVE QUESTION AND ANSWER

Q:What do you mean by Economics of power generation? 
The art of determining the per unit i.e. one KWh cost of production of electrical energy is 
known as Economics of power generation. 

2) Explain the term depreciation. 
The decrease in the value of the power plant equipment and building due to constant
use is known as depreciation. In practice, every power station has a useful life ranging from fifteen to thirty years. From the time the power station is installed, its equipment steadily deteriorates due to wear and tear so that there is a gradual reduction in the value of the plant. This reduction in the value of plant every year is known as annual depreciation. 

3) Define load factor. 
Load factor is the ratio of average demand to the maximum demand during a certain 
period of time and is applicable to both generating equipment and receiving equipment.
Load factor = Average demand/Maximum demand 

4) What is load curve? 
The curve showing the variation of load on the power station with reference to time is 
known as a load curve. 

5) Define diversity factor. 
Diversity factor is defined as the state of being dissimilar to one another. It is defined as 
the ratio of sum of the maximum demands of individual consuming units in a group during a specified period to the maximum demand of the whole group during the same 
period. 
Diversity factor = Sum of individual demands of different units in a group / Maximum 
demand of the entire group 
The value of diversity factor is always greater than one. If the diversity factor is higher, 
the cost per unit of generation will be lesser. 

6) What do you mean by utilization factor? 
It is a measure of the utility of the power plant capacity and is the ratio of maximum 
demand to the rated capacity of the power plant. It is always less than unity. 
Utilization factor = Maximum Demand on the power station / Rated capacity of the power 
station 
A low value of utilization factor indicates that the plant has been installed much in 
advance of need. A high value indicates that the plant is probably most efficient in the 
system. If its value exceeds unity, it means that the load has been carried in excess of 
rated capacity of the plant. 

7) Write short note on load duration curve? 
When the load elements of a load curve are arranged in the order of descending 
magnitudes, the curve thus obtained is called load duration curve. 
The load curve is obtained from the same data as the load curve but the ordinates are 
arranged in the order of descending magnitudes. In other words, the maximum load is 
represented to the left and decreasing loads are represented to the right in the 
descending order. Hence the area under the load duration curve and the load curve are 
equal. 
Load factor and diversity factor play a vital role in the cost of the supply of electrical 
energy. Higher the values of load factor and diversity factor, lower will be the overall cost 
per unit generated. 

8) Write the significance of load factor? 
Higher load factor means greater average load, resulting in greater number of units 
generated for a given maximum demand. Thus, the standing charges, which are 
proportional to maximum demand and independent of number of units generated, can be
distributed over a large number of units supplied and therefore overall cost per unit of 
electrical energy generated will be reduced. 

9) What is mean by base load?
The unvarying load which occurs almost the whole day 
on the station is known as base load.

 10) What are the methods for determining depreciation charges? 
The decrease in the value of the power plant equipment and building due to constant
use is known as depreciation. The cost of depreciation will depend on the size and type 
of equipment and on its estimated life. 
The reduction in the value of the plant every year is known as annual depreciation. Due 
to depreciation the plant has to be replaced by new one after its useful life. Therefore a 
suitable amount must be set aside every year, so that by the time the plant retires the 
collected amount by way of depreciation equals the cost of equipment. 
The methods commonly used for determination of annual depreciation charges are

11) What are the objectives of tariff? 
Electrical energy is sold at such a rate so that it not only returns the cost but also earns 
reasonable profit. Therefore, a tariff must cover the following items: 
 transmitting and distributing 
equipment. 
 equipment. 
costs etc. 

12) Define energy audit. 
Energy Audit means studying the energy consumption pattern in the utilities or
equipments by obtaining necessary data analyse the same to identify the areas where 
wastages or loses occur and suggest methods to avoid wastages or loss and also other 
consumption measures to ensure efficient use of energy.

13) What are the causes of low power factor? 
The following are the causes of low power factor 
otors are of induction type which have low lagging power factor. 
These motors work at a power factor which is extremely small on light load 0.2 to 0.3
and rises to 0.8 to 0.9 at full load. 
 heating furnaces operate at low 
lagging power factor. 
 during morning and evening and 
low at other times. During low load period, supply voltage is increased which increases 
the magnetization current. This results in the decreased power factor. 14) Define the term connected load factor. 
It is the sum of the continuous rating in KW of all electrical devices installed at the 
consumer’s premises and connected to the supply system. 

15) What are the important points to be taken into consideration while selecting the size 
and number of units? 
 variable demands from time to 
time. The nature of these demands can be seen from the load curve. The load variation 
is greater with a poorer load factor. 
units is per decided from the annual load 
curve of the station. The number and size of the units are selected in such a way that 
they correctly fit the station load curve. 
The capacity of the plant should be made 15% to 20% more than the maximum demand 
to meet the future load requirements. There should be a spare generating unit so that 
repairs and overhauling of the working units can be carried out. 

16) Define capacity factor. 
It is the ratio of average demand to plant capacity 

17) What is plant use factor? 
It is defined as the ratio of kwh generated to the product of plant capacity and number of 
hours for which the plant is in operation. 

18) What are the important types of power factor tariff? 
(i) kVA maximum demand tariff 
(ii) sliding rate tariff 
(iii) kWh and kVAR tariff 

19) What is three part tariff? 
The total charge comprised of fixed charge made during billing period, charge per kW of 
maximum demand and charge per kWh of energy consumed. 

20) What is the difference between base load and peak load? 
The unvarying load which occurs almost the whole day is known as base load. 
The various demands of load over and above the base load is the peak load.