Transcript Introduction to Electric Power System Definition

Introduction to Electric Power System
Definition: An electric power system is a network of electrical components used
to supply, transmit and use electric power.
An example of an electric power system is the network that supplies a region's
homes and industry with power.
For sizable regions, this power system is known as the grid and can be broadly
divided into the generators that supply the power, the transmission system that
carries the power from the generating centres to the load centres and
the distribution system that feeds the power to nearby homes and industries.
Smaller power systems are also found in industry, hospitals, commercial buildings
and homes. The majority of these systems rely upon three-phase AC power - the
standard for large-scale power transmission and distribution across the modern
world.
Schematic of a Typical Electric Power system
Main Components of a Standard Electric Power System
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Power supply: Thermal, hydro, nuclear, wind or solar power plants.
Transformer: To step up or step down of the electric power.
Substation: Transition from higher to lower voltages of power.
Loads: Inductive, resistive and capacitive loads with certain voltages,
currents, phases or frequencies.
Conductors: Transmission (> 69 kV) and distribution (.69 kV) conductors
either overhead or underground.
Capacitors and reactors: To improve power factor and regulate the
voltages in power system.
Power electronics: For high voltage and current rectifiers and switching.
Protective Devices: Fuse, switch gear, circuit breaker, relay etc.
SCADA System: Supervisory Control and Data Acquisition (SCADA) is used
for switching on generators, controlling generator output and switching in
or out system elements for maintenance.
Introduction to Transmission and Distribution
Significance of One-Line Diagram
In power engineering, a one-line diagram or single-line diagram (SLD) is a
simplified notation for representing a three-phase power system.
Features
• The one-line diagram has its largest application in power flow studies.
• Electrical elements such as circuit breakers, transformers, capacitors, bus
bars, and conductors are shown by standardized schematic symbols.
• Instead of representing each of three phases with a separate line or
terminal, only one conductor is represented.
• It is a form of block diagram graphically indicating the paths for power
flow between entities of the system.
* Red boxes represent circuit
breakers,
* Grey lines represent 3-phase
bus
and
interconnecting
conductors,
* Orange circle represents
an electric generator,
* Green spiral is an inductor,
Fig. A typical one-line diagram showing
power flows.
* Three overlapping blue circles
represent
a
doublewound transformer with a
tertiary winding.
History of Electric Power in Pre- and Post-our Country
In 1947: Total generation capacity: 21 MW, generating voltage: 6.6kV
No transmission system
In 1948: Electricity Directorate was created.
In 1959: Water and Power Development Authority (WAPDA) was created.
In 1960: Electricity Directorate was merged with WAPDA.
Siddhirganj, Chittagong and Khulna power plant established. (highest plant
size was only 10 MW Steam Turbine at Siddhirganj). Later Kaptai Dam was
constructed (40 MW) and Dhaka-Chittagong 132 KV transmission line was
made.
In 1972: Bangladesh Power Development Board (BPDB) was created.
In 1977: Rural Electrification Board (REB) was created.
In 1991: Dhaka Electric Supply Authority (DESA) now DPDC was created.
Present Features:
BPDB has total installed capacity of 8716 MW at 120 units
(BPDB 4910 MW at 60 Unit and IPP (Independent Power Producers) ,
SIPP & Rental at 60 units).
The transmission network is 8616 km long comprising 230, 132 and 66
KV lines.
The total numbers of grid sub-stations are 114 and the total capacity is
17,717 MVA.