The Power of Modern Relays Enables Fundamental Changes in Protection and Control System Design

Modern microprocessor relays are fundamentally different from protective relay technologies used in the past. Many paradigms that drove designs in the past are no longer valid. This paper describes many design concepts that can be used to improve the performance, reliability, robustness, and fault tolerance of protection and control systems. The design concepts that are presented in this paper are based upon experience gained in designing and commissioning many fully integrated protection and control systems currently in the field. If the design is approached from the beginning with consideration for integrating protection, metering, and control upon a foundation of modern multifunction programmable relays, we can create a system that has built-in continuous self-test features. We can extend the concept of continuous self-test that we have enjoyed in the relays themselves to the entire system. The design concepts discussed in this paper can make problems and failures that would be hidden in a traditional design, readily apparent so that they can be corrected before undesired operation can occur. These features generally do not require increased cost but are obtained by making use of the capabilities available in the powerful relays already being used