SEEKS, SEcurity Evaluation Knowledge-based System, is designed to assess
voltage security problems. This software selects the worst case single
and double outage contingencies based on network structure and operating
points and evaluates them for voltage violations. A brief description
of the process follows.
The network branch structures analyzed include radials, loops, and clusters.
A radial branch is a collection of single branches in series such that
any branch outage isolates the branches downstream of the outage. A loop
branch is a collection of single line branches in a loop configuration.
Should an outage occur on one of the transmission line branches it could
then create a series of radial branches or smaller loop branches. A cluster
branch is a collection of loop branches connected by low impedance transmission
lines. If a low impedance line should fail it could create a series of
loop branches.
Weights are assigned to the branches to reflect the impact of each branch outage
based on topology and operating points.
The highest weight means that the branch could cause voltage violation during an outage.
Worst case scenarios eliminate secure branches from further consideration, thereby increasing the
level of accuracy and performance of the system analysis.
Here are some rules from SEEKS:
- If radial contains both load and generation, and an internal branch has
larger flow than all other internal branches, then increase its weight by one.
- If a radial's boundary branch is the largest generation source in the system
,then increase its weight by two.
- If a branch carries the largest real/reactive flow away from a net generation
bus, then increase its weight based on the flow.
Single and double outage scenarios are then analyzed for worst case situations.
SEEKS accepts data from both text files and manual input. Using results
from a power flow algorithm, SEEKS evaluates the branches and assigns
branch weights to each. Branches range in complexity from the simple two
line buses described in this presentation to the IEEE 14-bus diagram shown earlier.
The user then must make a decision as to how to alter the system to again
place it in a position of stability. For example, shunt capacitance may
be added or adjusted. As shown earlier, different choices of shunt capacitance
will alter ß and the shape of the PV curves for the transmission
lines, and thus will alter the entire system.
All of the necessary files for Security Assessment are avaliable in the
Download Files link.
