2. The power system needs to be secured, we need
to protect it from the black out or any internal or
external damage.
The operation of the power system is set to be
normal only when the flow of power and the bus
voltages are within the limits even though there is
a profitable change in the load or at the generation
side.
3. Security function are of two type as follows:
Security control :- It determines the exact and
proper security constraint scheduling which is
required to obtain the maximized security level.
Security assessment :- It gives the security
level of the system in the operating state.
4. 1. System monitoring.
2. Contingency analysis.
3. Security constrained optimal power flow.
5. System monitoring provides the operator of
the power system with pertinent up-to-date
information on the current conditions of the
power system.
In its simplest form, this just detects violations
in the actual system operating state.
6. Usually a state estimator is used in the control
centre to process these telemetered data and
compute the best estimates of the system
states.
7. Contingency analysis is a mathematical
method for predicting equipment failure or a
specific line's failure and taking corrective
action before the system enters an unstable
state.
8. Insertion or removal of one or more elements in
an electrical network could be one of the
contingencies.
As a result of these adjustments, the power
system is no longer in the safe operating range.
Corrective action should be taken as soon as
possible; otherwise, the system may enter an
unstable region.
9. Major components of contingency analysis are:
Contingency definition
Contingency selection
Contingency evaluation
10. 1. Contingency definition – It comprise of set of
contingency that occur in the power system.
2. Selection – It is the process of selecting the
most severe contingencies from the contingency
list.
Thus this process removes the unimportant
contingencies and hence the contingency list is
shortened.
11. 3. Evaluation –
In this process it involves the necessary security
action or control to function in order to
remove the affect of contingency.
12. Preventive and corrective actions are needed to
maintain a secure operation of a system or to
bring it to a secure operating state.
Corrective actions such as switching of VAR
compensating devices, changing transformer
taps and phase shifters etc. are mainly
automatic in nature, and involve short duration.
13. Preventive actions such as generation
rescheduling involve longer time scales.
Security-constrained optimal power flow is an
example of rescheduling the generations in
the system in order to ensure a secure
operation.
14. In earlier days, security assessment in a power system
was mainly offline in nature.
Predefined set of rules or nomographs were used to
assist the operators in the decision-making process.
However, due to the highly interconnected nature of
modern power systems, and deregulated energy market
scenarios, operating conditions and even the topology
of a power system changes frequently.
15. Off-line techniques for security assessment are
therefore no- longer reliable in modern power
systems.
On-line security assessment techniques use
near-real-time measurements from different
locations in a power system, and continuously
update the security assessment of the system.
16. It is one of the easiest calculation way to
provide quick calculation of the possible
overloads.
The system security assessment is carried out
by calculating system operating limits in the pre
contingency and post contingency operating
states.
17. Pre contingency – It is the state of the power
system before the contingency has occurred.
Post contingency– It is the state of the power
system after the contingency has occurred.
It is assumed that this type of the contingency
has the security violations.
18.
19.
20. Power flow:
Determines the steady-state conditions of
the power system network for a specified
generation and load pattern.
Calculates voltages, phase angles, and
flows across the entire system.
21. Contingency analysis:
Assesses the impact of a set of contingencies
on the state of the power system and
identifies potentially harmful contingencies
that cause operating limit violations.
22. Optimal power flow:
Recommends controller actions to optimize a
specified objective function (such as system
operating cost or losses) subject to a set of
power system operating constraints.
23. Short-circuit analysis:
Determines fault currents for single-phase
and three-phase faults for fault locations
across the entire power system network.
