TRANSATLANTIC CABLE POWEK SYSTEM 159 



termination and power separation filter. This equipment and all the live 

 parts of the circuit, back to the common point to which the switches in 

 the individual regulator bays are connected, is enclosed in a high voltage 

 compartment. 



The paralleling control switches are mounted in high voltage compart- 

 ments in their respective regulating bays and must remain completely 

 enclosed, as their common cable connections are alive during cable 

 operation. These switches have an interrupting capacity of 1 ampere at 

 3,000 volts, thus providing a large safety factor over the 0.245 ampere 

 maximum load current. 



Fig. 11 illustrates some of the special design features built into the 

 equipment to facilitate maintenance. The high voltage compartment 

 shown open at the top is locked whenever the cable is in operation and 

 this protection feature will be described below. Pull-out drawers at the 

 bottom contain metering shunts, a test unit for adjusting voltage and 

 current protection limits, a voltage protection unit, a current protection 

 unit, and an alarm unit. While only one of these compartments is to be 

 pulled out at a time, they are arranged so as not to endanger personnel 

 or to affect service during adjustment when open. Doors are provided 

 on all bays to prevent accidental disturbance of adjustments and to 

 protect against damage to controls. 



Corona 



The high voltage ac elements of the complete regulator bays were 

 tested for corona with 4,000 volts ac applied, and furthermore, if corona 

 was observed on increasing the applied rms voltage to 5,000 volts, it was 

 required to extinguish when the voltage was reduced to 3500 volts. The 

 maximum acceptable leakage was 20 microamperes at 4000 volts across 

 the circuit (200 megohms) . A dc corona requirement of 4000 volts was 

 applied to the dc elements of the regulator bays and 5000 volts for the 

 common bay, with a maximum permissible leakage of 5 microamperes. 

 The higher corona requirements on the common bay were intended to 

 eliminate the necessity for turning down the entire system for repair. A 

 high standard of workmanship is required to provide such performance. 

 There can be no sharp projections and no loose strands of wire. Solder 

 must be applied in such a manner as to obtain a rounded smooth joint 

 and high voltage wiring must be dressed away from exposed grounded 

 metal, bus bars, etc., so that the outer braid (other than polyethylene) 

 does not come in contact with metal. 



