Schweitzer Engineering Laboratories SEL-351-5, Инструкция по эксплуатации

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3.39
Date Code 20070117
Instruction Manual SEL-351-5, -6, -7 Relay
Overcurrent, Voltage, Synchronism Check, Frequency, and Power Elements
Synchronism Check Elements
Voltage Window
Refer to Figure 3.26 .
Single-phase voltage inputs V
P
and V
S
are compared to a voltage window, to
verify that the voltages are “healthy” and lie within settable voltage limits
25VLO and 25VHI. If both voltages are within the voltage window, the
following Relay Word bits assert:
59VP indicates that voltage V
P
is within voltage window setting limits
25VLO and 25VHI
59VS indicates that voltage V
S
is within voltage window setting limits
25VLO and 25VHI
As discussed previously, voltage V
A
(or V
AB
for delta-connected voltage
inputs) determines the frequency on the voltage V
P
side of the circuit breaker.
Voltage V
A
is also run through voltage limits 25VLO and 25VHI to assure
“healthy voltage” for frequency determination, with corresponding Relay
Word bit output 59VA.
Other Uses for Voltage Window Elements
If voltage limits 25VLO and 25VHI are applicable to other control schemes,
Relay Word bits 59VP, 59VS, and 59VA can be used in other logic at the same
time they are used in the synchronism check logic.
If synchronism check is not being used, Relay Word bits 59VP, 59VS, and
59VA can still be used in other logic, with voltage limit settings 25VLO and
25VHI set as desired. Enable the synchronism check logic (setting E25 = Y)
and make settings 25VLO and 25VHI. Apply Relay Word bits 59VP, 59VS,
and 59VA in desired logic scheme, using SEL
OGIC
control equations. Even
though synchronism check logic is enabled, the synchronism check logic
outputs (Relay Word bits SF, 25A1, and 25A2) do not need to be used.
Block Synchronism Check Conditions
Refer to Figure 3.26 .
The synchronism check element slip frequency calculator runs if both voltages
V
P
and V
S
are healthy (59VP and 59VS asserted to logical 1) and the
SEL
OGIC
control equation setting BSYNCH (Block Synchronism Check) is
deasserted (= logical 0). Setting BSYNCH is most commonly set to block
synchronism check operation when the circuit breaker is closed (synchronism
check is only needed when the circuit breaker is open):
BSYNCH = 52A (see Figure 6.1 and Figure 7.3 )
In addition, synchronism check operation can be blocked when the relay is
tripping:
BSYNCH =
... + TRIP
Slip Frequency Calculator
Refer to Figure 3.26 .
The synchronism check element Slip Frequency Calculator in Figure 3.26
runs if voltages V
P
, V
S
, and V
A
(or V
AB
for delta) are healthy (59VP, 59VS,
and 59VA asserted to logical 1) and the SEL
OGIC
control equation setting
BSYNCH (Block Synchronism Check) is deasserted (= logical 0). The Slip
Frequency Calculator output is: