Engineering features of the 230-kv Boulder-Chino transmission line

Eric T. B. Gross (Ithaca, N. Y.): Appreciation is due to Messrs. A. A. Kroneberg and E. M. Hunter for publishing their paper, which contains some new and very important data, and seems to me to be one of the most interesting in the field of the application of earth-fault coils, published recently in this country. Although earth-fault coils have been used on 220-kv lines for the past ten years on the lines of the R.W.E., connecting the water-power stations in the region of Vorarlberg in Austria with the steam power stations in northwest Germany, by a double-circuit line not far from the French and Belgian border, no data concerning tests or practical experience have been published by the R.W.E. (Rheinisch Westfaelisches Elektrizitaetswerk) so far. But as I am somewhat familiar with these questions, I want to report that the results were satisfactory and that nothing unexpected has been observed, besides perhaps the necessity of cleaning the insulators more often in the misty coal-mine district near the Belgian border. The length of said double-circuit line is more than twice that of the Boulder-Chino line, but the in-phase component of the fundamental wave of the compensated earth-fault current of one circuit is only about 70 amperes or seven per cent of the whole capacitive earth-fault current. It may be worth mentioning, that earth faults on one of the circuits of the double line do not influence the other circuit, as decoupling coils are also in use.¹