Sel SEL-421 - Page 232

R.2.64
SEL-421 Relay Reference Manual Date Code 20111215
Auto-Reclosing and Synchronism Check
Synchronism Check
Synchronism-check element output 25W1BK1 in Figure 2.31 operates the
same as in Figure 2.30. Element output 25W1BK1 is unaffected by relay
settings 25SFBK1 and TCLSBK1, and by whether system conditions are
slipping. Element 25W1BK1 follows normalized synchronism-check voltage
source V
S1
.
Figure 2.31 “Slip—With Compensation” Synchronism-Check Element Output
Response
Element 25A1BK1 follows V
S1
. With setting 25SFBK1 (maximum slip
frequency) set to other than OFF, the relay calculates V
S1
derived from V
S1
.
Phasor V
S1
leads V
S1
by an angle described by Equation 2.3:
Equation 2.3
V
P
(a)
(b)
(c)
(d)
V
S1
V'
S1
V
P
V
S1
V
P
V
S1
V
P
V
S1
Response of synchronism-check
element outputs (Relay Word Bits):
25W1BK1 = logical 1
25A1BK1 = logical 1
25W1BK1 = logical 1
25A1BK1 = logical 0
25W1BK1 = logical 0
25A1BK1 = logical 0
25W1BK1 = logical 0 (follows V
S1
)
25A1BK1 = logical 0 (follows V'
S1
)
A
N
G
1
B
K
1
A
N
G
1
B
K
1
A
N
G
1
B
K
1
A
N
G
1
B
K
1
A
N
G
1
B
K
1
A
N
G
1
B
K
1
A
N
G
1
B
K
1
A
N
G
1
B
K
1
V'
S1
V'
S1
V'
S1
Slip (asynchronous systems—not paralleled).
Max slip frequency setting 25SFBK1 other than OFF
angle
f
S1
f
P
– slip cycle
s
60 cyc
s
-----------------
•
---------------------------------------------------
360
slip cycle
------------------------
TCLSBK1 (cyc)• • =