28-06-2012, 01:38 PM
Trends in Power System Protection and Control
Trends in Power System .doc (Size: 837.3 KB / Downloads: 54)
Abstract
As a consequence of deregulation, competition, and
hand, the advanced measurement and communication
problems in securing capital outlays for expansion of the
technology in wide area monitoring and control, FACTS
infrastructure, modern power systems are operating at
devices (better tools to control the disturbance), and new
ever-smaller capacity and stability margins. Traditional
paradigms (fuzzy logic and neural networks) may provide
entities involved in securing adequate protection and
better ways to detect and control an emergency.
control for the system may soon become inadequate, and
the emergence of the new particip ants (non-utility
Better detection and control strategies through the concept
generation, transmission, and distribution companies)
of wide area disturbance protection offer a better
requires coordinated approach and careful coordination
management of the disturbances and significant
of the new operating conditions. The paper reviews the
opportunity for higher power
key issues and design considerations for the present and
transfers and operating economies. Wide area disturbance
new generation of SPS and emergency control schemes,
protection is a concept of using system-wide information
and evaluates the strategies for their implementation
introduction
System-wide disturbances in power systems are a
and measurement technologies, more "intelligent"
challenging p roblem for the utility industry because of the
equipment can be used at the local level to improve the
large scale and the complexity of the power system. When
overall emergency response.
a major power system disturbance occurs, protection and
control actions are required to stop the power system
Decentralized subsystems, that can make local decisions
degradation, restore the system to a normal state, and
based on local measurements and remote information
minimize the impact of the disturbance. The present
(system-wide data and emergency control policies)
control actions are not designed for a fast-developing
and/or send pre-processed information to higher
disturbance and may be too slow. Further, dynamic
hierarchical levels are an economical solution to the
simulation software is applicable only for off-line
problem. A major component of the system-wide
analysis. The operator must therefore deal with a very
disturbance protection is the ability to receive system-
complex situation and rely on heuristic solutions and
wide information and commands via the data
policies. Today, local automatic actions protect the system
communication system and to send selected local
from the propagation of the fast-developing emergencies.
information to the SCADA centre. This information
However, local protection systems are not able to
should reflect the prevailing state of the power system.
consider the overall system, which may be affected by the
disturbance
Angular stability
The ob jective of out-of-step pro tection as it is ap plied to
generators and systems, is to eliminate the possibility of
Outage of one or more power system elements due to the
damage to generators as a result of an out-of-step
overload may result in overload of other elements in the
condition. In the case of the power system separation is
system. If the overload is not alleviated in time, the
imminent, it should take place along boundaries which
process of power system cascading may start, leading to
will form islands with matching load and generation.
power system separatio n. When a power system separates,
Distance relays are often used to provide an out-of-step
islands with an imbalance between generation and load
protection function, whereby they are called upon to
are formed with a consequence of frequency deviation
provide blocking or tripping signals upon detecting an
from the nominal value. If the imbalance cannot be
out-o f-step condition.