Schweitzer Engineering SEL-351P, Быстрый старт

Страница: 269 / 674

Date Code 990215 Trip and Target Logic 5-7
SEL-351P Manual Técnico
Determining Three-Pole Open Condition Without Circuit Breaker Auxiliary Contact
If a circuit breaker auxilary contact is not connected to the SEL-351P Recloser Control, SEL
OGIC
Control Equation setting 52A is set:
52A = 0 (numeral 0)
With SEL
OGIC
Control Equation setting 52A continually at logical 0, 3PO logic is controlled
solely by load detection element 50L. Phase pickup 50LP is set below load current levels.
When the circuit breaker is open, Relay Word bit 50L drops out (= logical 0) and the 3PO
condition asserts:
3PO = logical 1 (circuit breaker open)
When the circuit breaker is closed, Relay Word bit 50L picks up (= logical 0; current above
phase pickup 50LP) and the 3PO condition deasserts after the 3POD dropout time:
3PO = logical 0 (circuit breaker closed)
Note that the 3PO condition is also routed to the permissive overreaching transfer trip (POTT)
logic (see Figure SECTION 5: .6) and the loss-of-potential (LOP) logic (see Figure 4.1).
Circuit Breaker Operated Switch-Onto-Fault Logic
Circuit breaker operated switch-onto-fault logic is enabled by making time setting 52AEND
(52AEND
≠
OFF). Time setting 52AEND qualifies the three-pole open (3PO) condition and
then asserts Relay Word bit SOTFE:
SOTFE = logical 1
Note that SOTFE is asserted when the circuit breaker is open. This allows elements set in the
SEL
OGIC
Control Equation trip setting TRSOTF to operate if a fault occurs when the circuit
breaker is open (see Figure SECTION 5: .1). In such a scenario (e.g., flashover inside the circuit
breaker tank), the tripping via setting TRSOTF cannot help in tripping the circuit breaker (the
circuit breaker is already open), but can initiate breaker failure protection, if a breaker failure
scheme is implemented in the SEL-351P (see Figure 7.25 example in
Output Contacts in
Section 7: Inputs, Outputs, Timers, and Other Control Logic ) or externally.
When the circuit breaker is closed, the 3PO condition deasserts (3PO = logical 0) after the 3POD
dropout time (setting 3POD is usually set for no more than a cycle). The SOTF logic output,
SOTFE, continues to remain asserted at logical 1 for dropout time SOTFD.
Close Bus Operated Switch-Onto-Fault Logic
Close bus operated switch-onto-fault logic is enabled by making time setting CLOEND
(CLOEND
≠
OFF). Time setting CLOEND qualifies the deassertion of the load detection
element 50L (indicating that the circuit breaker is open).
Circuit breaker closure is detected by monitoring the dc close bus. This is accomplished by
wiring an optoisolated input on the SEL-351P (e.g., IN104) to the dc close bus. When a manual
close or automatic reclosure occurs, optoisolated input IN7 is energized. SEL
OGIC
Control
Equation setting CLMON (close bus monitor) monitors the optoisolated input IN104: