This seminar paper presentation provides an overview of power system stability, including a proposed definition and classification. It discusses rotor angle stability, voltage stability, and frequency stability. Rotor angle stability refers to synchronous machines remaining in synchronism after a disturbance. Voltage stability means maintaining steady voltages at all buses after a disturbance. Frequency stability is the ability to maintain steady frequency following a severe imbalance between generation and load. Flexible AC transmission systems (FACTS) are also introduced as a means to enhance stability, security, and power transfer capacity.

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A
Seminar Paper Presentation on
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PRESENTED BY:-
HARENDRA KUKNA
4th year, EE
PCE/EE/11/043
DEPARTMENT OF ELECTRICAL ENGINEERING
POORNIMA COLLEGE OF ENGINEERING
ISI-6 RIICO INSTITUTIONALAREA,
JAIPUR -302022
SUBMITTED TO:-
Mr. Nitin Goel
Dept. Of Electrical Engg.
2011-15

2. Contents
 Power System Stability Overview
 Power System Stability: A Proposed Definition
 Need of Stability Classification
 Power System Stability Classification
 Rotor Angle Stability
 Voltage Stability
 Frequency Stability
 Fact Devices
 References
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3. Power System Stability Overview
 Power system is defined as a network of one or more
generating units, loads and power transmission lines
including the associated equipments connected to it.
 The stability of a power system is its ability to develop
restoring forces equal to or greater than the disturbing
forces to maintain the state of equilibrium.
 Power system stability problem gets more pronounced in
case of interconnection of large power networks.
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4. Power System Stability: A Proposed
Definition
• Power system stability is the ability of an electric power
system, for a given initial operating condition, to regain a
state of operating equilibrium after being subjected to a
physical disturbance, with most system variables bounded
so that practically the entire system remains intact.
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5. Need of Stability Classification
 Stability analysis is easier. Also it leads to proper and
effective understanding of different power system
instabilities.
 Key factors that leads to instability can be easily
identified.
 Methods can be devised for improving power system
stability.
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6. Power System Stability Classification
 Rotor angle stability.
 Small disturbance angle stability.
 Transient stability.
 Voltage stability.
 Small disturbance voltage stability.
 Large disturbance voltage stability.
 Frequency stability.
 Short term frequency stability.
 Long term frequency stability.
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7. Stability Classification at a Glance
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8. Rotor Angle Stability
 Rotor angle stability refers to the ability of synchronous
machines of an interconnected power system to remain
in synchronism after being subjected to a disturbance.
 Rotor angle instability occurs due to angular swings of
some generators leading to their loss of synchronism with
other generators.
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9. Voltage Stability
 Voltage stability refers to the ability of a power system to
maintain steady voltages at all buses in the system after being
subjected to a disturbance from a given initial operating
condition.
 A system is voltage instable if for atleast one bus in the system,
the voltage magnitude decreases as reactive power injection is
increased.
 Voltage instability results in progressive fall or rise of voltages
of some buses.
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10. Frequency Stability
 Frequency stability refers to the ability of a power system to
maintain steady frequency following a severe system upset
resulting in a significant imbalance between generation and
load.
 Frequency instability leads to tripping of generating units
and/or loads.
 Frequency stability may be a short-term phenomenon or a
long-term phenomenon.
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Facts
• Flexible AC Transmission System (Facts) is a new integrated
concept based on power electronic switching converters
and dynamic controllers to enhance the system utilization
and power transfer capacity as well as the stability, security,
reliability and power quality of AC system interconnections.

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• Steady state voltage stability
• Power flow control
• Damping of power system oscillations
• Reducing generation costs
• HVDC link application
• Deregulated power systems
• Interconnection of renewable, distributed generation and
storages.
Applications Of FACT

13. References
 “Definition and Classification of Power System Stability”, IEEE
TRANSACTIONS ON POWER SYSTEMS, VOL. 19, NO. 2, MAY
2004
 Khan, Asfar Ali, “Determination of reactive power limit for
voltage stability study in a grid system”, September 1999,
M.Tech Dissertation, AMU, Aligarh
 Kundur, P., “Power System Stability and Control”, McGraw Hill,
1994.
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14. Thank You
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