TABLE OF CONTENTS John B.Dagenhart, P.E.
Professional Engineer, Clapp Research Associates, P.C.
In the early days of electrical usage, standard electric service, along with its associated shortcomings, was usually adequate for operating most electrical equipment. Some of the most sensitive users in the earlier days (those with continuous industrial processes) would sometimes go to the length of posting a thunderstorm sentry to warn of nearby lightning; they would shut down the machinery until the storm passed. Lightning rod protection systems did an adequate job of lightning protection under most circumstances. Although long-term electrical outages were an inconvenience and occasionally caused economic loss, most electrically operated equipment operated without serious problems.
Digital electronic devices, specifically digital clocks and other microprocessor-controlled devices (industrial controllers and personal computers), began appearing in the mid to late 1970s. As those devices became more widely used, it became clear that the old standards of electric power were not adequate for their reliable operation. In addition to the initial problems experienced by large computer operations with dirty power, users found they could not keep their digital clocks set because brief interruptions in the power supply were causing them to reset. Later, residential users found they could not get digital timers on their home videotape recorders to maintain time and record their favorite television shows. The next wave of complaints came with the more widespread use of personal computers, microprocessor-controlled industrial equipment, and adjustable-speed drives.
There are two major...
