. American hydroelectric practice; a compilation of useful data and information on the design, construction and operation of hydroelectric systems, from the penstocks to distribution lines . ;P Sec. ^ -Overland Eelay - Eeverse Power Eelay Fig. 142.—Use of Reverse Power and Definite-Time Limit Relays on Parallel Feeders limit reverse-power relays must be used, and the time limit of each suc-cessive relay should be increased by a sufficient amount to allow time forthe circuit-breaker in the preceding substation to open. In the illustra-tion it has been assumed that one-third secon
. American hydroelectric practice; a compilation of useful data and information on the design, construction and operation of hydroelectric systems, from the penstocks to distribution lines . ;P Sec. ^ -Overland Eelay - Eeverse Power Eelay Fig. 142.—Use of Reverse Power and Definite-Time Limit Relays on Parallel Feeders limit reverse-power relays must be used, and the time limit of each suc-cessive relay should be increased by a sufficient amount to allow time forthe circuit-breaker in the preceding substation to open. In the illustra-tion it has been assumed that one-third second is a sufficient time to allowfor this purpose, but such a small setting cannot be used unless the relaysare Fig. 143.—Relay Layout for Ring System Systems Having More Than One Source of Power.—Such a system isshown in Fig. 143 with a generator placed at substation D. One difficultywould be encountered if the generator at A should be shut down and allthe load carried by the generator at D. In this case the entire relay sys-tem would have to be readjusted, as shown in Fig. 144. Although this SYSTEM OPERATION AND ECONOMICS 257 example is a simple one, it illustrates the condition which occurs whenevera complicated system of distribution is encountered. It also illustratesthe necessity for using relays whose adjustment can be quickly Feeders.—When parallel feeders are used, reverse-power relays Gn
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