POWER-FEED SYSTEM — NEWFOUNDLAND-NOVA SCOTIA LINK 279 



328 



en 324 

 ^322 



LU 



I 320 

 < 



=! 316 



Z 

 .3 12 



LU 



a. 308 



D 

 O 



D 304 



CL 



300 

 296 



0.5 



1.0 1.5 2.0 



OUTPUT IN KILOVOLTS 



2.5 



3.0 



Fig. 1 — Output-current versus output-voltage characteristics, (a) Master. 

 (6) Slave, (c) Master versus master shut-down. 



equipments at both ends of the link. Any equipment can operate with 

 any of the characteristics (a), (h) or (c). 



Normally the choice between characteristics (a) and (b) is made auto- 

 matically by the equipment. If the output voltage does not reach 80 

 per cent of the full link voltage (approximately 2 kv) , the unit will have 

 the slave characteristic (6) (DCAB). If the output voltage reaches or 

 exceeds 2 kv, the unit automatically switches to the master characteristic 

 (a) (EAF) . Once having switched to the master characteristic the equip- 

 ment does not automatically change back to the slave characteristic 

 even if the output voltage falls below 2 kv. 



When the link is energized, the first equipment switched to line will 

 come on as a slave unit ; its output voltage will then pass 2 kv and it will 

 automatically be switched to the master characteristics and the complete 

 link will be energized from one end. The second unit switched to line 

 will come on as a slave unit, and having a higher output current, will 

 drive down the output voltage of the master unit at the other end until 

 the current of the slave unit has become equal to that of the master 

 (DCA in Fig. 1). The output voltage of this equipment will not exceed 

 2 kv and it will not switch to master. The cross-over point of the two 

 characteristics. A, will determine the potential fed from each end, and 

 this can be adjusted as indicated by the dotted lines near C. 



In an emergency, an equipment can be taken out of service by switch- 

 ing off the ac supply, and the links will then be powered from the dis- 



