Date Code 20001006
Close and Reclose Logic
6-31
SEL-351 Instruction Manual
With the shot counter at shot = 2, Relay Word bits SH0 (shot = 0) and SH1 (shot = 1) are both
deasserted to logical 0. This keeps the 51PT phase time-overcurrent element from tripping. The
51PT phase time-overcurrent element is still operative, and its pickup (51P) can still assert and
then deassert, thus continuing the sequencing of the shot counter to shot = 3, etc. The 51PT phase
time-overcurrent element cannot cause a trip because shot
≥
2, and SH0 and SH1 both are
deasserted to logical 0.
Note:
Sequence coordination can increment the shot counter beyond last shot in this example (last
shot = 2 in this factory setting example) but no further than shot = 4.
The following Example 2 limits sequence coordination shot counter incrementing.
The shot counter returns to shot = 0 after the reset timer (loaded with reset time 79RSD) times out.
Additional Settings Example 2
Review preceding Example 1.
Assume that the line recloser in Figure 6.8 is set to operate twice on the fast curve and then twice
on the slow curve for faults beyond the line recloser.
Assume that the SEL-351 Relay is set to operate once on 51PT and then twice on 51AT, 51BT, or
51CT for faults between the SEL-351 Relay and the line recloser. This results in the following trip
setting:
TR
= 51PT * (SHO) + 51AT + 51BT + 51CT
This requires that two open interval settings be made (see Table 6.2 and Figure 6.6). This
corresponds to the last shot being:
last shot = 2
If the sequence coordination setting is:
79SEQ
= 79RS * 51P
and there is a permanent fault beyond the line recloser, the shot counter of the SEL-351 Relay will
increment all the way to shot = 4 (see Figure 6.9). If there is a coincident fault between the
SEL-351 Relay and the line recloser, the SEL-351 Relay will trip and go to the Lockout State.
Any time the shot counter is at a value equal to or greater than last shot and the relay trips, it goes
to the Lockout State.
To avoid this problem, make the following sequence coordination setting:
79SEQ
= 79RS * 51P * SH0
Refer to Figure 6.10.
If the SEL-351 Relay is in the Reset State (79RS = logical 0) with the shot counter reset (shot = 0;
SH0 = logical 1) and then a permanent fault beyond the line recloser occurs (fault current I
F
in
Figure 6.8), the line recloser fast curve operates to clear the fault.
Содержание SEL-351
Страница 14: ...Courtesy of NationalSwitchgear com ...
Страница 16: ...Courtesy of NationalSwitchgear com ...
Страница 40: ...Courtesy of NationalSwitchgear com ...
Страница 74: ...Courtesy of NationalSwitchgear com ...
Страница 146: ...Courtesy of NationalSwitchgear com ...
Страница 186: ...Courtesy of NationalSwitchgear com ...
Страница 220: ...Courtesy of NationalSwitchgear com ...
Страница 304: ...Courtesy of NationalSwitchgear com ...
Страница 340: ...Courtesy of NationalSwitchgear com ...
Страница 380: ...Courtesy of NationalSwitchgear com ...
Страница 450: ...Courtesy of NationalSwitchgear com ...
Страница 506: ...Courtesy of NationalSwitchgear com ...
Страница 528: ...Courtesy of NationalSwitchgear com ...
Страница 534: ...Courtesy of NationalSwitchgear com ...
Страница 536: ...Courtesy of NationalSwitchgear com ...
Страница 550: ...Courtesy of NationalSwitchgear com ...
Страница 562: ...Courtesy of NationalSwitchgear com ...
Страница 570: ...Courtesy of NationalSwitchgear com ...
Страница 584: ...Courtesy of NationalSwitchgear com ...
Страница 602: ...Courtesy of NationalSwitchgear com ...
Страница 610: ...Courtesy of NationalSwitchgear com ...