Abstract-- Taiwan Power Company (TPC) has implemented an event-based special protection system (SPS) against extreme contingencies. The decision making mechanism of the event- based SPS is based on look-up tables. A huge number of contingency analyses are required for constructing and updating the look-up tables. In this paper, automation techniques are developed to increase the analysis efficiency for speeding up preparing a look-up table. Contingency selection algorithms including both the depth-first algorithm and breadth-first algorithm are used to search for contingency cases automatically. A preprocess interface is designed to provide a friendly user- machine interface between the power system raw data and simulation software. And a computer program is developed to integrate the search algorithm and preprocess interface for fulfilling the automation of contingency analysis for SPS. The techniques realized with programs demonstrate a great time- saving advantage compared to traditional man-made work. The automation of contingency analysis for SPS does not only speed up the simulation process but also improve the efficiency, which is well demonstrated in the paper. Index Terms—power system protection, power system faults, automation. I. INTRODUCTION n the latest five years, there have been several severe power blackouts experienced in Taiwan. These power events include the 729 incident which happened in July 29 1999, the 921 incident in September 21 1999 and the 410 incident in April 10 2004. These power contingencies have caused paramount economic loss in Taiwan. So how to avoid blackouts or lower the occurring probability of blackouts surely is the most important issue of power companies and the government. After the 729 incident [1]-[2], Taiwan Power Company (TPC) immediately investigated the cause and found that insufficient power infrastructure was one of the major Shih-En Chien is with the Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan (e-mail: d93921010@ntu.edu.tw). I-Ta Cheng is with the compulsory military service of Taiwan (e-mail: r93921020@ntu.edu.tw). Yi-Ting Chou is with the Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan (e-mail: r95921016@ntu.edu.tw). Chih-Wen Liu is with the Department of Electrical Engineering, National Taiwan University, Taipei, Taiwan (e-mail: cwliu@cc.ee.ntu.edu.tw). causes. In order to avoid similar power contingency from happening, TPC decided to strengthen the power system protection except implementing the power infrastructure establishment. Evaluating the feasibility of many power system protection strategies, TPC finally adopted the special protection systems (SPS) to improve the defense ability of Taiwan power system to disturbances or contingencies. A SPS is designed to detect abnormal system conditions and take predetermined corrective actions (other than the isolation of faulted elements) to preserve system integrity and provide acceptable system performance [3]. Fig. 1 illustrates the general structure of SPS. Fig. 1. General structure of a special protection system [3] There are many ways to categorize SPS, including input signal types, the level of influence to the power system, the action time length, contingency types responded by the SPS, etc. The most commonly used one is by input signal types comprising the response signal and event signal. Thus SPS can be categorized into the response-based and event-based SPS. For the response-based SPS, electric variables such as the bus voltage or frequency are measured and sent to the SPS to execute state estimation or other calculations. Then we match the calculation results with the normal values. If it is not normal, we take predetermined corrective actions. TPC has designed an event-based SPS through the help of Powertech Labs Inc. of Canada [4]. When an event happens, this event- based SPS will directly detect and judge the event to figure out whether the control signal needs to be sent to trigger one control action. The manner of judgment is based on a look-up table which relates an event with its control action. Because there are too many types of events, and load conditions also influence which control action will be taken, the event-based Shih-En Chien, I-Ta Cheng, Yi-Ting Chou and Chih-Wen Liu Automation of Contingency Analysis for Special Protection Systems in Taiwan Power System I