Background

PROTECT YOURSELF
Integrated protection and control systems with continuous self-testing
MODERN MICROPROCESASSOR RELAYS ARE fundamentally different form protective relay technologies used in the past. Many paradigms that drove designs in the past are no longer valid. This article describes many design concepts that can be used to improve the performance, reliability, robustness, and faulttolerance of protection and control systems. The design concepts that are presented in this article 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 multifunctionprogrammable relays, we can create a system that has built in continuous self-test enjoyed in the 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 article can make problems and filatures that would be hidden in atraditional design readily apparent so that they can 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.

BACKGROUND
A power system can be operated without automation and remote control. It cannot be operated without protection, thus, theprotective relays form the logical basis for any integrated protection and control system. To build an integrated system, we need to have a foundation to build upon. That foundation is the protection system.
Modern protective relays allow us to improve the reliability of the protection and control system. Design concepts that eliminate single points of failure for critical protection and controlfunctions reduce the urgency and consequences of failures. A properly design integration system can leverage the capabilities of the protective relays.
We want to build in continuous self-test features that will allow the system to detect failures and alarm so that corrective action can be taken before undesired operation occurs.
This article covers concepts that will enable you to designfault-tolerant, robust, integrant system. The concepts cover a number of diverse, but related, topics. To build a robust and fault-tolerant system, we need to use an architecture that will eliminate single points of failure. To make the system easy to operate and maintain, we should design continuous self-test features into the integrated protection and control system. If we agree that these concepts should beincluded in our design, we can make a case using dual systems.
To further improve reliability, we need to use dc control-circuit design concepts that take advantage of the characteristics design concepts that take advantage of the characteristic of numerical relays. These are subtle suggestions that can enhance the reliability of the design. Finally, it is important that the design documentationpackage be up to the challenges presented by this new technology.
INTEGRATED SYSTEM ADVANTAGE
The integration of powerful multifunction devices allows us to save initial cost by eliminating unnecessary devices that only duplicate functionality that is currently available in necessary devices (the protective relays).
Alternatively, it allows us to have advanced functionality on systems where wecould not have previously justified the cost of that functionality. Such functionality includes advanced metering, telemetry, and load data recording, remote control, automatic controls, and interlocking, and system monitoring, equipment monitoring, and maintenance data recording.
Integration allows us to save ongoing maintenance and operating cost by reducing device counts, automating many...