The protection and control systems in the US utility industry are still primarily composed of electromechanical relays and systems. Over 80 percent of the relays are still electromechanical at Michigan Electric Transmission Company (METC), with only incremental upgrading to microprocessor technology carried out in recent years. Maintenance costs of older equipment are high, and limited non-operational fault data is accessed via modem from the microprocessor relays.

METC embarked on a program to develop a business and technical strategy to replace the aging protection and control equipment. This paper describes how an aggressive replacement strategy can be the most cost-effective solution for system-wide upgrading. This strategy and its benefits (from both reliability and financial perspectives) are described using the program to completely replace the protection and control equipment in all 82 of its substations. METC is developing enterprise-level processing of the masses of data to improve operational and business efficiency.