Load Curve Questions and Answers
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.
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.
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
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.
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.
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
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.
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.
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 umber 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.
What is mean by base load?
The unvarying load which occurs almost the whole day on the station is known as base load.
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.
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.
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 wastage’s or loses occur and suggest methods to avoid wastages or loss and also other consumption measures to ensure efficient use of energy.
What are the causes of low power factor?
The following are the causes of low power factor motors 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.
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.
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.
Define capacity factor.
It is the ratio of average demand to plant capacity
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.
What are the important types of power factor tariff?
(i) kVA maximum demand tariff
(ii) sliding rate tariff
(iii) kWh and kVAR tariff
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.
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.