Basler Electric BE1-50/51B-218 - Manual (Page 37)

curve E (extremely inverse) selected (SW3-3 set to OFF) and the TIME DIAL set to 2.0. The feeder
reclosing relay is set for two reclose attempts at 3 and 15 seconds after the initial trip. If a permanent fault
occurs (magnitude ten times pickup), calculate the feeder breaker trip time for each of the three
operations. Refer to Section 1 for characteristic curve constants.
From the time characteristic curve equation.
K BD
C M
AD
T
N
Trip
 


 
028 0 2 02758 . 0
1 10
2 7624 7
0938 2
.
.
.
  



028 0 05516 . 0
1 10806 124
5248 15
.
.
.
 


seconds 0.209

From the reset characteristic curve equation.
1 M
RD
T
2
Reset


seconds 15.5
1 0
2 7.75
2
 



M = 0 if current goes to zero.
Negative result indicates reset time.
Results: Full trip = 0.209 seconds and full reset = 15.5 seconds if current goes to zero.
In Figure 4-5,
T
A
= 0.209 seconds (relay was at reset).
T
B
= value < T
A
because rewind has not gone to zero.
T
C
= value < T
A
because rewind has not gone to zero.
9252000995 Rev H BE1-50/51B-218/-228 Installation 4-5
Figure 4-5. Coordination Timing Diagram