TRANSATLANTIC CABLE POWER SYSTEM 145 



tials, when in the test position, in order to protect maintenance 

 personnel. 



h. The current regulator should be of the fail-safe type so that im- 

 pairment of any of the regulator components will not permit excessive 

 rise in cable current. In the event of component trouble, an aural or 

 visual alarm should occur. 



It was decided that a high speed electronic constant -current regu- 

 lator backed up by a slower speed ser\'o system, as shown in Fig. 2 and 

 discussed in detail later, would best meet the abo\-e requirements. In 

 this way, fast response with high gain is combined with wide regulating 

 range, yet the efficiency is high and the load-handling capacilities of 

 the various components are held to a minimum. With regard to sim- 

 pler alternatives, the electromechanical type of current regulator, using 

 relays and a motor-driven rheostat, is too slow to protect the repeater 

 tubes from a cable short circuit and its accuracy is insufficient to meet 

 the regulation requirements. The all-magnetic type of regulator is pos- 

 sibly most dependable but it does not readily provide either the speed 

 of response or the wide regulating range needed. 



GENERAL DESCRIPTION 



Prime and Standby Power Source 



Commercial service is considered the normal prime source of power 

 for the cable, although at the Clarenville terminal commercial power 

 was not available at the time of installation. Anticipating this condi- 

 tion, a reserve plant consisting of three 60-kw diesel alternators was 

 installed and the distribution circuits were arranged, as shown in Fig. 3, 

 to provide partial or total use of the commercial service. Initially all 

 cable power was supplied by diesel operation, alternating the prime 

 movers on a weekly basis. These sets are paralleled manually when they 

 are interchanged, to prevent an interruption in the 60-cycle supply. 

 It may be noted that Engine Xo. 1 is arranged as an automatic standby 

 whether prime power is provided by diesels or by commercial service. 



The switching and distribution arrangements are designed to be es- 

 sentially failure-proof. At Clarenville, for example, two ac distribution 

 cabinets, each capable of being fed from two sources, were provided in 

 separate locations. The normal source through Engine Xo. 1 control 

 bay can be readily by-passed directly to the manual diesels, should En- 

 gine Xo. 1 control bay be disabled. Furthermore, allocation of charging 

 rectifiers, control circuits, ac motors for continuity sets, etc., has been 



