Protocol modification between substation and control center with IEC 60870-5-104

Electricity Generating Authority of Thailand (EGAT) has developed an in-house Supervisory Control And Data Acquisition (SCADA) system for a decade. The EGAT-SCADA system has been implemented in all regional control centers and substation. Ratchaburi 3 (RB3) is a substation, which was built in year 2000, serving a 4,346.75 MW Ratchauri Power Plant. It is one of a few substations using SCADA system imported from foreign supplier. RB3 uses ABB IED bay controller with Micro SCADA 8.4.3 SYS 500 at bay level and EGAT-SCADA system at station level. Previously, the communication between ABB system and EGAT-SCADA needed to convert the protocol from ABB ANSI X3.28 to CDC Type II and vice versa. CDC Type II was a common protocol used for the communication between substation control system and control center of EGAT. However, as technology trend moves toward to IP based protocol, EGAT has been planning to implement IEC 60870-5-104 and IEC 61850 for its control system. In 2010, EGAT-SCADA was modified to serve IEC 60870-5-104. The control system at RB3 was also scheduled to move to IEC 60870-5-104. This paper describes how EGAT migrated the communication protocol between RB3 control system and the control center to IEC 60870-5-104. Four steps of the migration were identified: Analyzing the gap of the system between the current and the prospective, Modifying the system to reach the target, Testing the system to meet the requirement, and Implementing the updated system. Two problems were found during the process. One is the dependency of CDC Type II protocol causing some functions of IEC 60870-5-104 needed to refer to the old protocol. Another is due to some interrogation functions of the local control system. However, all the problems were solved and the modification process was completed. The updated system has been tested and in service since March 2011.