Power system studies conducted for the purpose of complying with NERC (North American Electric Reliability Corporation) standards address the issue of evaluating power system performance, following normal and contingency conditions. The results of these studies should ensure that transmission system performance meets NERC reliability standards and that upgrades to meet future system needs are developed in a manner that maintains reliable and safe operation of the transmission system.
Transmission Planning Standards (TPL) define reliable system performance after the loss of a single bulk electrical element, two or more bulk electrical elements, or after extreme events.
Loss of two elements has historically been done using the N-2 contingency analysis, which corresponds to the loss of two bulk electrical elements simultaneously.
An upcoming stricter NERC TPL standard also requires an N-1-1 contingency analysis, which corresponds to the loss of two items in a row. System adjustments must be made after the 1st N1 contingency, and can be made after the 2nd N-1 contingency in each N-1-1 contingency pair.
There is a growing need to provide system planners with a fast automated process to conduct NERC compliance studies effectively. The N11 and N2 contingency analysis framework must have the ability to perform the following calculations within a simulation run:
• Identify critical contingencies that cause violation of steady-state, thermal, and stress stability limits;
• Determine transmission system bottlenecks;
• Determines possible cascade modes;
• Calculate the minimum number of necessary system adjustments;
• If load shedding is required, minimize the amount of load shedding to maintain reliable power system operation;
• Provide automatic reporting capabilities.
System settings may include: MW dispatch, MVAr dispatch, transformer tap change, phase shifter adjustment, capacitor and reactor switching, line switching, and load shedding.
It is of the utmost importance to ensure that the analysis framework is based on AC analysis methodology that allows monitoring of steady-state, thermal and voltage stability limits.
Since a variety of N-1-1 scenarios can be implemented, the analysis tool must be highly flexible in order to be quickly and easily adjusted to the needs and specifics of a particular utility or ISO.
The strategy to carry out massive contingencies N 1 1 AC should focus on providing Planning engineers with a solution that has the following capabilities:
• Automatic creation of N 1 1 contingency lists;
• Automation of the contingency analysis process N 1 1;
• Allow the user to implement multiple sets of system settings within a single run;
• Incorporate the analysis of cuts in cascade;
• Provide easy and flexible reporting and post-processing in accordance with utility/ISO practice.
Additionally, this process should be used to help planners optimize transmission system expansion, which will reduce the risk of blackouts and improve transmission system reliability. Therefore, the solution must have the ability to perform massive contingency analysis (millions of thousands to millions of contingencies) per single run.
For more details on using the Physical and Operating Margins (POM) suite for N-1-1 contingency analysis, please visit http://www.vrenergy.com.
