Electric Vehicles

Abstract

This paper describes the protective relaying schemes employed by Georgia Power Company to protect synchronous generators from smgle-phaseto-ground faults. Three types of relays are connect¬ ed in the secondary of a distribution grounding transformer. These include a conventional electro¬ mechanical overcurrent relay with time overcurrent unit and instantaneous overcurrent unit, a solidstate overvoltage relay (with timing module) tuned to reject frequencies near 180 hertz, and a solid-state undervoltage relay (with timer) tuned to reject fre¬ quencies near 60 hertz present at the generator neutral. The proper method of selecting the genera¬ tor grounding components and protective relays is described, and detailed setting instructions for all relays are also included. This Paper was selected by the Power Systems Relaying Committee for reprinting in the Review because of its High Current Interest to the Power Engineering Society Member¬ ship. The paper was first printed in the PA&S Transactions Vol. 101 #12 December 1982, pp 4490-4501. to work with, inexpensive, light, has a very negative reduc¬ tion potential with three electrons per event, has good power and energy density, is easy to recycle, and there is a huge aluminum industry in place." The aluminum-air battery, he explains, is mechanically re¬ charged by removing the spent anode and inserting a fresh one, much as one refills a tank with gasoline when the fuel is used up. The anode is the aluminum and there is an air cathode, the space between filled with a concentrated solution of potassium hydroxide. As the aluminum dis¬ solves in the solution to produce alumínate, electrons flow through an external circuit to do useful work and then react with oxygen at the air electrode to complete the circuit. What happens that hampers the whole concept, he says, is "Homogeneous corrosion occurs on the aluminum surface and that is undesirable. You need to suppress this reaction so that when no power is being drawn from the battery, no corrosion occurs." And in this perhaps-undeclared race to come up with a new battery good enough to oust the internal combustion en¬ gine, who's the farthest ahead? "We are," grins Macdonald, "or at least I think so." When and if the alloy is found which lets aluminum more or less duplicate the corrosion per¬ formance of zinc? "Then I think we will have a technically viable product." How far, then, might it be to a practical, affordable, every¬ day electric auto which does what it's supposed to do? "Not soon. It is probably 25 years down the road," he admits, adding, "Don't expect any quick fixes or dramatic breakthroughs."