would be referred to the main reclosing circuit breaker at the power 

 generating plant. The circuit recloser would complete one, two, or three 

 reclosures before lockout to allow for transient conditions. The generator 

 would be kept in operation during the reclosing operation but would be 

 shut down at the time lockout occurs. The plant would also shut down 

 on loss of control power. Standard differential and overcurrent relay pro- 

 tection would be provided for the generator plant. The transmission cable 

 and load module faults would be referred by a carrier current scheme to the 

 main reclosing circuit breaker for isolation. 



The two modes of operation considered for the protection system 

 were cascade and selective tripping. The selective system was not considered 

 beyond a preliminary stage because of the added weight and space require- 

 ments. 



A cascade protective scheme was therefore selected for the transmission 

 system. Faults in the cascade system would be detected anywhere in the power 

 transmission system up to and including the load module transformer. Loads 

 connected on the secondary of the load module transformer would be pro- 

 vided with adequate protection with automatic, multiple-state reclosers. Both 

 the load protection and reclosing equipment have to be coordinated with the 

 transmission system for proper operation. 



An unattended load module and generating plant, as envisioned in the 

 study, would constantly display their condition and have a provision for 

 periodic inspection. Some form of control is also necessary to allow an 

 inspector or operator to operate (close or open) a circuit breaker remotely, 

 depending on conditions noted on the display board. An alarm system 

 connected to an established monitoring point is also required to alert plant 

 operators of trip functions and problem indicators (high water temperature, 

 low lubricating oil, etc.). A carrier system would be employed for this 

 purpose. 



In addition to providing a transfer trip function and indication, the 

 carrier system would provide an overall differential circuit around the entire 

 transmission line. Any faults in the cable would be detected by this differential 

 zone which would, in turn, trip a differential relay located at the generator 

 plant. Differential relays would be provided for the generator and transformer 

 at the generator plant. Activating the differential relay would trip the main 

 reclosing circuit breaker independent of the carrier system. 



Control power would be provided by a control power transformer 

 which would be connected ahead of the main breaker on the generator output. 

 Thus, control power would always be available regardless of fault conditions, 

 providing the generator is operating normally. The control system would 

 automatically switch to emergency control power source should loss of the 

 primary control power occur. A loss of both power sources would cause the 

 generator plant to shut down. 



70 



