OPTIMAL STRATEGIES FOR SYSTEM-WIDE PROTECTION AND CONTROL REPLACEMENT PROGRAMS

SUMMARY The protection and control systems in the USA utility industry are still primarily composed of electromechanical relays and systems. For example, in substations of Michigan Electric Transmission Company (METC), 87 percent of the relays are still electromechanical, with only incremental upgrading to microprocessor technology carried out in recent decades. Maintenance costs of older equipment are high, and only limited non-operational fault data is accessed via modem from the scattered population of microprocessor relays. In 2004, METC embarked on a program to develop a sweeping business and technical strategy to replace the aging protection and control equipment. This paper describes how an aggressive investment and replacement strategy can be the most cost-effective solution for system-wide upgrading. This strategy and its benefits are described using as an example the METC program to completely replace the protection and control equipment in all 82 of its 345 kV and 138 kV substations. The implementation methodology, addressing impact on capital and operating costs, is described in more detail and is based on: • Integrating all relaying, control, monitoring, automation, and enterprise functions through Ethernet LANs in the substations and EPRI’s Common Information Model (CIM). • Introducing IEC 61850 LAN integration system and protocol as rapidly as is practical, to replace control wiring, and to simplify integration and data flow. • Organizing protective functions using the newest generations of relays to improve dependability and security, while drastically reducing the number of units required, and complying with or exceeding all agency design requirements.