by Eric Udren, Quanta Technology, USA
This issue has memorialized George D. Rockefeller, originator of the computer-based protective relay. Separately, it presents the vision of future PAC based on digital substations with virtualized and distributed functionality. It is exciting to contemplate the trajectory of PAC technology from its origins.
In 1967 when IEEE Transactions published Rockefeller’s landmark computer relaying proposal, relays were long-lived electromechanical workhorses evolved from the inception of the electric age. They were produced from basic raw materials in huge vertically integrated factories by thousands of employees with specialized machines. Utilities bought these essential products with little concern for cost. With hindsight we can observe the shocking expense – by 2000, settable multifunction microprocessor transmission line relays could be delivered in a few days at a cost of between 2% and 4% (in constant currency) of the cost of a 1970 electromechanical line protection terminal, custom-built and delivered 48 weeks after ordering. On cost alone, electromechanical technology was ultimately unsustainable. .
Computers were not exotic to industry in 1967. Businesses already ran on large mainframe computers with rooms full of magnetic data storage media. A decade before the first simplistic Intel 4004 microprocessor appeared, small integrated-circuit computers were already serving in critical process control applications – even running some utility generators. Still, protective relaying developers and users were worried about reliable protection, not yet paying attention to the digital evolution around them. It was only after Rockefeller’s demonstration that the industry saw transformative benefits, igniting interest and creativity even before economics caught up. Gradually over the next two decades users accepted digitization as the tool to manage demands of stressed-grid functional needs, performance data communications, and affordability.
We see a parallel situation today. We are critically dependent on component microprocessor relays, only beginning to adopt newer technology that has already transformed industry and commerce around us. Wide-area networking with robust cloud redundant processing is already executing mission-critical financial, defense, and high-speed business applications. The networking and computing infrastructure has short technical life, so engineers have created sustainable installations around standard generic platforms, easy upgrading, remote configuration and monitoring, and big-data analytics for asset management.
Fortunately, capabilities of IEC 61850 and related standards have evolved in parallel. Logical nodes with standardized function-level information exchanges enable platform-independent system designs and flexible function locations. The PAC design and its grid application are virtualized in a large-scale utility operational architecture that can be managed and upgraded in flight.