Schweitzer Engineering Laboratories SEL-351A, Руководство пользователя

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3.47
Date Code 20080213
Instruction Manual SEL-351A Relay
Overcurrent, Voltage, Synchronism Check, and Frequency Elements
Synchronism Check Elements (Not in SEL-351A-1)
3. Refer to Reclose Supervision Logic on page 6.5 .
Refer to the bottom of Figure 6.2 . If timer 79CLSD is set
greater than zero (e.g., 79CLSD = 60.00 cycles) and it times
out without SEL
OGIC
control equation setting 79CLS (Reclose
Supervision) asserting to logical 1, the relay goes to the
Lockout State (see top of
Figure 6.3 ).
Refer to the top of Figure 6.2 . If timer 79CLSD is set to zero
(79CLSD = 0.00), SEL
OGIC
control equation setting 79CLS
(Reclose Supervision) is checked only once to see if it is
asserted to logical 1. If it is not asserted to logical 1, the relay
goes to the Lockout State.
Refer to the top of Figure 3.29 . Ideally, circuit breaker closing
is initiated when V
S
* is in phase with V
P
(Angle Difference = 0
degrees). Then when the circuit breaker main contacts finally
close, V
S
is in-phase with V
P
, minimizing system shock. But
with time limitations imposed by timer 79CLSD, this may not
be possible. To try to avoid going to the Lockout State, the
following logic is employed:
If 79CLS has not asserted to logical 1 while timer
79CLSD is timing (or timer 79CLSD is set to zero and
only one check of 79CLS is made), the synchronism
check logic at the bottom of
Figure 3.28 becomes less
restrictive at the “instant” timer 79CLSD is going to
time out (or make the single check). It drops the
requirement of waiting until the
decreasing Angle
Difference (V
S
* approaching V
P
) brings V
S
* in phase
with V
P
(Angle Difference = 0 degrees). Instead, it just
checks to see that the Angle Difference is less than
angle settings 25ANG1 or 25ANG2.
If the Angle Difference is less than angle setting
25ANG1 or 25ANG2, then the corresponding Relay
Word bit, 25A1 or 25A2, asserts to logical 1 for that
“instant” (asserts for 1/4 cycle).
For example, if SEL
OGIC
control equation setting
79CLS (Reclose Supervision) is set as follows:
79CLS =
25A1 + ...
and the angle difference is less than angle setting
25ANG1 at that “instant,” setting 79CLS asserts to
logical 1 for 1/4 cycle, allowing the sealed-in open
interval time-out to propagate on to the close logic in
Figure 6.1 . Element 25A2 operates similarly.
Synchronism Check
Applications for
Automatic Reclosing
and Manual Closing
Refer to Close Logic on page 6.2 and Reclose Supervision Logic on page 6.5 .
For example, set 25ANG1 = 15 degrees and use the resultant synchronism
check element in the reclosing relay logic to supervise automatic reclosing,
e.g.,
79CLS = 25A1 + ... (see Figure 6.2 )
Set 25ANG2 = 25° and use the resultant synchronism check element in
manual close logic to supervise manual closing (for example, assert
IN106
to
initiate manual close), e.g.,
CL =
IN106 * (25A2 + ... )
(see Figure 6.1 )
Courtesy of NationalSwitchgear.com