TYPES OF ELECTRICAL LOAD
Compiled By :
EET, MSEDCL, Nagpur
Load Demand defines requirement of load concern to particular category.
Load requirements depends upon its terrain, its population and living standard.
Following figures indicates utilization of the energy by different category of the loads.
Type of load
Utilisation of Energy %
Electricity is bought and sole on the basis of demand
Demand is in fact the average demand registered over a fixed time period.
Fixed time period is also known as integration period.
Integration period is usually 15 /30 /60 min.
30 min demand is recommended for –
There is no undue penalty for short duration
From consideration of thermal time constant of m/c.
Most of the meters having facility of 30 min integration
Demand factor = MD/CL
Load Factor :
Statement of the load factor is meaningless unless
Interval of time period of max demand
Time over which average is taken are specified.
e.g. Daily / Monthly / yearly
Load Factor = Units Consumed during given period /Max Demand X Hours in period
Ratio of sum of Max Demand of the consumer to Max Demand of whole system.
Diversity factor is always Greater than unity.
Diversity Factor = sum of individual MD / Total MD
Coincidence Factor is reciprocal of Diversity factor
Diversity factor at
Distribution T/F --- 1.00 – 1.5
------ 1.1 -- 1.60
------- 1.1 -- 1.25
Annual Diversity factors for five regions are -Northern Region
North Eastern region
Power factor : it is a Ratio of Active power to Apparent Power
Low PF means more current and greater loss in system
Less pf --- less efficient
PF = KWH / KVAH
KVAH = √ KWH ² + KVARH ²
System Load Diversity
Electrical load diversity factor is the probability that a particular piece of equipment will
start at the time when the load is at its peak.
To plan for peak power demand.
For ex.- During Summer season J&K state have lean power demands so they sell power to
Punjab & adjoining state as these state have larger Power demand.
And situation is reverse during winter.
Connected Load ::
Installed load of the consumer is the sum of rated inputs of the all electrical equipments
installed in the consumer premises.
Connected load is that part of the installed load which have been calculated by the
Definition of the connected load is different in different utilities.
Street Light : load of the street light is depend upon illumination required on road.
Small town --- bulb of 40w ---- 250V --- span 45-50m -- Height 7.5 to 9 m
Large town ---- lamp of 40 – 100 W -- – 30m-35m
Incandescent / Florescent / Mercury /SodiumVapour
Lightening Intensity depends upon Traffic speed , safety criteria
Lamps with better eff., longer life, good colour rendering index are available.
Water supply :
Load estimated from water requirement in a specified area such as -Rural
--- 50 ltr /day/person
– 70 ltr / day / person
– 90 ltr / day / person
Metropolitian city -- 120 ltr /day / person
As per WHO min water required per person per day 23 Liters in very small villages.
Irrigation Load : - Power requirement depends on ----Nos of watering required for each kind of crop
Area under the crop
Nature of the soil
Depth of the ground water level.
HP requirement for electric motor used for irrigation is on the basis of
average discharge of centrifugal hydraulic pump.
Efficiency of the pump is depends on --------Specific speed
Stuffing box friction
Size of pump
Internal running clearance
For efficient pump – water level should not be more than 5-6m below pump,
For level more than 15m – submersible pump are used.
Sensitive Load :
The load which is sensitive to the fluctuation of system parameter are called sensitive load.
e.g. Computer based product.
Thyrister controlled devices
Parameters to be within limits of ---Voltage unbalance
-- < 3 %
------ < +/- 0.5 Hz
Voltage waveform distortion -- < 5 %
Dirty Loads :
Dirty loads are known for the load which produce –
Large variation in reactive power demand
This phenomenon creates ----Extra system losses
Thermal over loading
control & protection relaying disturb
Dirty loads are ---Computer TV
Remedial measures against the dirty loads are ------to provide—
Filters, Delta – star T/F, U/G feeders --- Harmonics
Supply consumer on HV /EHV level / parallel transformer / conditioning equip.--Voltage
Thyristor controlled capacitors --- to reduce voltage fluctuation due to less pf.
Q 1 : A 50 MW Hydro generator delivers 350 million units during the year. Calculate the plant
Ans : PLF = Actual energy generated / max energy that could have been generated
= 350x 106 / 50x 103 x8760 = 0.8
Q 2 : A generating station has Max demand of 20 MW, plant capacity factor 48%, a load
factor of 60 % , Plant use factor of 80%
find -- a) daily Energy produced
b). The max
energy that could be produced daily if the plant run for all the time. C) the max energy that
could be produced daily if the plant when running as per operating scheduled were fully
LF = AD/MD = 0.6
hence AD = 20x0.6 = 12 MW
Daily Energy produced = 12 x 24 = 288 MWH
Installed capacity = AD/PCF = 12/0.48 = 25 MW
Energy per day as per plant capacity = 25 x 24 = 600MW
Max energy as per scheduled= Actual energy produced/PUF