A full AC contingency analysis of
the post-contingency system is carried out for each contingency
and the results are stored for reporting and review. The functions
provide the same analysis capability as activity ACCC in PSS™E,
with greater flexibility in contingency modeling, load flow solution
and reporting results.
The MVA loading for monitored branches is calculated for pre-
and post-contingency conditions and PSS™MUST reports on
loadings greater than the MVA ratings selected in the PSS™MUST
options. Bus voltages can be monitored for high or low voltage
levels and for large voltage magnitude changes as a result of
contingencies. PSS™MUST will also indicate when voltage
collapse and non-convergence has been caused by contingencies.
The user may select the AC load flow solution parameters for each
AC contingency analysis study. The solution options include a
non-divergent load flow solution algorithm which offers insights
into low-voltage and voltage collapse phenomena for the case being
studied.
AC contingency analysis in PSS™MUST is performed on the
pre-shift case and does not directly calculate the AC contingency
results after a specified transfer or specified transaction(s).
The AC contingency analysis recognizes all contingency file formats
used in DC contingency analysis, including contingency with branch
closing, load throwover, various bus events, and dispatch commands.
This analysis recognizes all monitored element file formats; including
voltage deviations and changes, and flowgates.
Statistic functions summarize statistics
on all specified contingencies. This function classifies all contingencies
in several categories as shown in the figure below. This function
also shows the number of the currently excluded contingencies
according to the used EXCLUDE files and contingencies.
The figure below contains an example
of an AC Contingency Analysis Summary report. This AC report provides
summary information or branch overloads as well as bus voltage
violations. The number of voltage violations is provided along
with the magnitude and contingency number of the worst bus voltage
violations.
This function reports all contingencies
with violations among the user selected subset of contingencies.
Three reported columns contain contingency branch flow, total
number of violations caused by the reported contingency, and the
worst violation for the initial and final cases (see figure below).
This report provides summary information
(one line per contingency) for userselected contingencies. Also,
this report provides contingency indices that can be used by other
contingency analysis functions. Reviewing this report identifies
potential data errors and provides a convenient overview on selected
contingencies.
A Detailed Contingency report provides
the following information on selected contingencies:
Detailed contingency description including the listing of
all contingency events. For branch opening events, it will report
branch flow at initial and maximum study transfer levels. A
user has the option to suppress detailed reporting of dispatch
events.
List all the monitored elements with loading above user-specified
loading level threshold. Selecting 100% loading level will report
overloads only.
Island composition for contingencies that create buses, which
are not connected to the swing bus.
Bus voltage violations report.
The user may specify the loading percent cut-off for this report.
For example, if the user specifies 90%, PSS™MUST will report
monitored elements with loading greater than 90% of rating. The
low voltage and high voltage margins can be selected for the presentation
of voltage results. The margin is the amount to be subtracted
from the low voltage limit specified in the monitored element
file (or added to the upper voltage limit/voltage change limit
specified in the monitored element file). For example, if the
monitored element file specifies that bus voltages below 0.95pu
should be considered violations and the user enters a margin of
0.02 in the Vlow box, then PSS™MUST will report voltages
less than 0.93pu. If the user enters zero margin, the bus voltage
limits specified in the monitored element file apply for the report.
The user may also specify a listing of events involved in each
contingency as well as islanding and dispatch information (figure
below).
