radial distribution system question
radial distribution system question
(OP)
http://static.schneider-electric.us/assets/consult...
In the PDF linked above on page 3. they compare two different types of radial systems, figures 5-4 and 5-5, and say that:
"A more reliable and maintainable arrangement utilizing multiple primary feeders is shown in figure 5-5. In the
system of figure 5-5, each unit substation is supplied by a dedicated feeder from the service entrance switchgear"
I don't quite understand why Figure 5-5 is more reliable. Even though the only difference between the two systems is the addition of a switch before the transformer. Would some one care to enlighten me?
Thanks in advance.
Saad
In the PDF linked above on page 3. they compare two different types of radial systems, figures 5-4 and 5-5, and say that:
"A more reliable and maintainable arrangement utilizing multiple primary feeders is shown in figure 5-5. In the
system of figure 5-5, each unit substation is supplied by a dedicated feeder from the service entrance switchgear"
I don't quite understand why Figure 5-5 is more reliable. Even though the only difference between the two systems is the addition of a switch before the transformer. Would some one care to enlighten me?
Thanks in advance.
Saad






RE: radial distribution system question
RE: radial distribution system question
Figure 5.4 - Each Load Interrupter switch/fuse combination is physically located next to the substation transformer. Since the only overcurrent protection device upstream of the primary conductors for each transformer is the medium voltage circuit breaker, a fault on either of these two feeder sections will trip the MV CB and cause a system wide outage. This is specifically why 5.4 is less reliable than 5.5
Figure 5.5 - Each Load Interrupter switch/fuse combination is physically located at the medium voltage switchgear (though not apparent in the diagram). The substation primary isolation switch is located next to the transformer. The conductors between the upstream fuse and the isolation switch make up a dedicated feeder to each transformer (whereas in the previous arrangement, they were essentially two sections of the same feeder). A fault on any single feeder will cause a power outage only to the loads within the upstream fuse's zone of protection (1/2 the system). This is more reliable than 5.4 because multiple simultaneous feeder faults are required to take out the entire system.
As far as maintainability goes, having switches at both ends of a feeder allows for complete isolation.
RE: radial distribution system question
Regards
Marmite
RE: radial distribution system question
This probably belongs in the grammar forum - it's the text which is poorly written, not the drawings!