1 Abstract--A knowledge based trouble call system with colored Petri net (CPN) inference models is designed to identify the most probable faulted device for trouble call analysis (TCA) of distribution systems. The CPN model for inference engine considers two major parts: the traditional escalation method and the load comparison method. To identify the faulted device more accurately according to the outage reports by service customers, the searching procedures based on the improved escalation method are included in the best first search of the CPN. The most possible outage locations with corresponding blown out protective device are determined by applying parallel-like reasoning in the CPN to solve multiple fault events simultaneously. One of the distribution systems in Taiwan Power Company (Taipower) with 36000 customers is selected for computer simulation to demonstrate the effectiveness of the proposed methodology to enhance the function of distribution outage management. Index Terms— Trouble call analysis, Colored Petri net, Distribution automation system. I. INTRODUCTION With the advancement and application of computer control systems, unreliable power supply can be extremely costly to electric utilities and their customers. To improve system reliability and operation efficiency, a distribution automation system (DAS) has been implemented by Taipower since 1998. With TCA as one of ten functions, the outage duration of customers caused by system faults can be reduced by identifying the faulted device more accurately for repair crews to expedite power restoration. Besides, the outage information can be retrieved by distribution system operators so that proper load transfer can be taken for service restoration. With deregulation of power industry, it becomes important for utility companies to enhance service quality so that more customers can be kept in the competitive marketplace. With a fault on the primary feeder of an underground distribution system in Fig. 1, the feeder circuit breaker will be tripped by over-current relays. System dispatchers can diagnose the contingency by SCADA system according to the status change of the circuit breaker and protective relays at switches along the feeder. After detecting the fault H.-J. Chuang and C.-Y. Ho are with the Department of Electrical Engineering, Kao-Yuan Institute of Technology, Luzhu Shiang, Kaohsiung County 821, Taiwan C.-H. Lin and C.-S. Li are with the Department of Electrical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung 80709, Taiwan. C.-S. Chen and C.-C. Yun are with the Department of Electrical Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan. . location, the boundary load breakers of 4-way line switches are opened to isolate the fault section. The feeder circuit breaker is then closed to restore power service of upstream customers. After that, the proper switching operation plan is derived by considering the capacity reserve and operation constraints so that the downstream unfaulted but out of service area can be transferred to the other feeders. With the DAS system, the fault detection, isolation and service restoration (FDIR) can be completed within 3 to 5 minutes in Taipower. With more than 80% of faults in Taipower distribution system on the lateral or customer sides, the blown fuse at the source size of lateral or distribution transformers will interrupt power service of the affected customers. It is still not cost justified for system operators to identify this type of fault by DAS systems because so many fault indicators and communication systems have to be installed and the affected area is much serious faults on main feeders. After receiving phone calls from customers to report the power outage, repair crews are sent out to do the field check to locate fault locations. It is very difficult and time consuming to identify faulted devices and complete service restoration for an underground distribution systems. To solve the problem, a geographic based digital mapping system has been created for the DAS system to include system network connectivity and service customers with account number, Design of A Knowledge Based Trouble Call System with Colored Petri Net Models Hui-Jen Chuang, Chia-Hung Lin, Chao-Shun Chen, Chi-Chun Yun, Chin-Yin Ho, and Chung-Sheng Li Fig. 1. A typical underground distribution system of Taipower. To serve the load D S D S MTa Feeder i SWi1 Four-way line switch 3C500XP2 Power Fuse Lateral 1 3C#1XP To serve the load Four-way high voltage mold joint Lateral 3 Lateral 2 50~100A Customers SWi2 31~49A Customers 100~200A Customers Under 31A Customers N.O. 3C500XP2 Four-way line switch Feeder j SWj1 Power fuse Ij Ii SWj2 Lateral 4 N.O. MTb Pad-mounted transformer Circuit breaker 2005 IEEE/PES Transmission and Distribution Conference & Exhibition: Asia and Pacific Dalian, China 0-7803-9114-4/05/$20.00 ©2005 IEEE.