The main purpose of this paper is to discuss the basic
understanding of power quality in relation to the distributed gen-
eration. Due to considerable overlap between two technologies,
disturbances affecting the power quality, which are mainly cause
by the addition of Distributed Generation (DG) on the existing
power system network. Injection of the DG into an electric power
grid can affect the voltage quality. Distributed generation of dif-
ferent voltage levels when connected to the power system network
could influence the voltage regulation, sustained interruptions,
harmonics, sags, swells, etc. All the information given here is col-
lected from different references by keeping in mind the students at
the beginning level of the concerned topic.
—power quality, distributed generation, distrib-
uted generators, distributed resources, disturbances.
The demand of power is escalating in the world of electricity.
This growth of demand triggers a need of more power genera-
tion. DG uses smaller-sized generators than does the typical
central station plant. Distributed generators are small scale
generators located close to consumers; normally Distributed
Generators are of 1 kW to 100 MW .
Definition of DG 
Distributed generation in simple term can be defined as a
small-scale generation. It is active power generating unit that is
connected at distribution level.
IEEE defines the generation of electricity by facilities suf-
ficiently smaller than central plants, usually 10 MW or less,
so as to allow interconnection at nearly any point in the
power system, as Distributed Resources.
Electric Power Research Institute (EPRI) defines distributed
generation as generation from a few kilowatts up to 50 MW.
International Energy Agency (IEA) defines DG as “Power
generation equipment and system used generally at distri-
bution levels and where the power is mainly used locally on
The International Council on Large Electricity Systems
(CIGRE) defines DG as generation that is not centrally
planned, centrally dispatched at present, usually connected
to the distribution network, and smaller than 50-100 MW.
These generators are distributed throughout the power system
closer to the loads. The DG penetration in the grid poses new
challenges and problems to the network operators as these can
have a significant impact on the system and equipment opera-
tions in terms of steady-state operation, dynamic operation,
reliability, power quality, stability and safety for both customers
and electricity suppliers. However as we are only concerned
with power quality of the primary and secondary distribution
system, we will only consider generator sizes less than 10MW
Umar Naseem Khan is with the Faculty of Electrical Engi-
neering, Wroclaw University of Technology, Wroclaw 50-370,
Poland (e-mail: email@example.com).
. Generators larger than this are typically interconnected at