Electrical Power Systems

4 Electrical Power Systems
Domestic Load: Domestic load mainly consists of lights, fans, refrigerators, airconditioners,
mixer, grinders, heaters, ovens, small pumping motors etc.
Commercial Load: Commercial load mainly consists of lighting for shops, offices,
advertisements etc., fans, heating, airconditioning and many other electrical appliances used in
commercial establishments such as market places, restaurants etc.
Industrial Loads: Industrial loads consists of small-scale industries, medium-scale
industries, large-scale industries, heavy industries and cottage industries.
Agriculture Loads: This type of load is mainly motor pump-sets load for irrigation purposes.
Load factor for this load is very small, e.g., 0.15–0.20.
1.4 POWER ACTOR O VARIOUS EQUIPMENTS
Total kVA (or MVA) demand depends on the power factor of various equipments and lagging
power factor of some of the equipments are tabulated below:
Induction motors : 0.6–0.85
ractional HP motors : 0.5–0.80
luorescent lamps : 0.55–0.90
Neon signs : 0.40–0.50
ans : 0.55–0.85
Induction furnaces : 0.70–0.85
Arc welders : 0.35–0.55
1.5 BASIC DEINITIONS O COMMONLY USED TERMS
Connected Load: Each electrical device has its rated capacity. The sum of the continuous
ratings of all the electrical devices connected to the supply system is known as connected load.
Demand: The demand of an installation or system is the load at the receiving terminals
averaged over a specified interval of time. Here, the load may be given in kW, kVA, kiloamperes,
or amperes.
Demand Interval: It is the time period over which the average load is computed. The time
period may be 30 minute, 60 minute or even longer.
Maximum Demand: The maximum demand of an installation or system is the greatest of
all demands which have occurred during the specified period of time. Maximum demand
statement must express the demand interval used to measure it. or example, the specific
demand might be the maximum of all demands such as daily, weekly, monthly or annual.
Coincident Demand (or Diversified Demand): It is the demand of composite group, as
a whole, of somewhat unrelated loads over a specified period of time. It is the maximum sum of
the contributions of the individual demands to the diversified demand over a specific time
interval.
Noncoincident Demand: It is the sum of the demands of a group of loads with no
restrictions on the interval to which each demand is applicable.
Demand actor: It is the ratio of the maximum demand of a system to the total connected
load of the system. Thus, the demand factor (D) is given as:
D =
Maximum demand
Total connected load
... (1.1)