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Dear everyone,

First, I want to apologize for any misused power system terms in my question because I am not a power system major.

My question might seem silly to you as professional power system engineer. Anyway, let me try to describe my question in a simple way.

What I have: I have a hourly RAW data file for a real power system.

What I want: I want to simply test all N-1 contingency on this system. My current method: I simply use "readrawversion" module to load the RAW hourly data, and generate my .sub, .mon, .con and .dfax files in PSSE GUI (I import the same RAW data in PSSE), then I call "acccwithdsp_2" module to run all the contingency analysis

Where I am stuck: The problem is that I got an error saying "largest mismatch exceeds mismatch tolerance". I am using 0.6MW as the mismatch tolerance. So I eventually have to increase this tolerance until 200MW to get my AC contingency run properly.

Suggested Solution from some power system engineer: Some expert told me that the problem is that I didn't run power flow (I use FNSL(i.e.Full Newton-Raphson method) ) first on the data before I run contingency analysis.

Now comes the question: I kind of understand what he meant-- contingency analysis step needs to use the solution of power flow as a starting point. But as far as I know, the AC contingency analysis only requires input including mismatch tolerance, a bunch of parameters/options and fours files (i.e. .sub, .mon, .con, and .dfax) as necessary arguments. On the other side, module "FNSL" dosen't return solution in any form. So how ACCCWITHDSP_2 module gonna benefit from running a power flow?

My guess: I will just simply run FNSL before ACCCWITHDSP_2 with a small desired mismatch tolerance of 0.6 to see what happens. If problem solved, then I guess PSSE just somehow knows that a power flow has been run for that contingency analysis process.

Could anyone explain to me the underlying mechanism for this to work? Thanks very much for your generous help and time!

Best regards,

Yaping