PSL691U Line Protection and Control Device

Guodian Nanzi PSL691U Line Protection and Control Device

1. Overload Alarm
When the current of any phase exceeds the set value, after a delay, the device issues an alarm signal.
2. Reclosing
When all three conditions are met—reclosing function enabled, circuit breaker in closed position for 15 seconds, and spring not charged contact open—the reclosing charging is completed (i.e., the reclosing is ready to operate). After reclosing charging is completed, the operation light flashes; if reclosing is not ready, the operation light remains steady and does not flash.
After reclosing charging is completed, once a protection trip or unintended trip occurs, the reclosing is initiated after the reclosing delay.
After reclosing is initiated, it operates based on the selection of no-voltage check, synchronism check, or no-check.
a) Synchronism check reclosing condition: | ∠Ux －∠Uab － ∠φ | ≤ synchronism check closing angle
Note: ∠Ux is the line voltage angle;
∠Uab is the busbar voltage Uab angle;
∠φ is the angle by which Ux leads Uab under normal conditions due to phase differences or system wiring.
b) No-voltage check reclosing condition: Ux ≤ no-voltage check set value
If Ux is greater than the no-voltage check set value, it automatically switches to synchronism check reclosing.
c) No-check reclosing: No judgment is made on the magnitude or phase angle of Ux, and the circuit breaker is closed directly.
If reclosing cannot be completed within 10 seconds after initiation, the reclosing process is automatically terminated.
When manual tripping, remote tripping, overload, underfrequency load shedding, or undervoltage load shedding occurs, the device automatically blocks the reclosing function.
3. Synchronism Check Manual Closing
When the relationship between Ux and Uab meets the synchronism check reclosing condition and synchronism check manual closing is enabled, contacts 4X19 and 4X21 of the device close. Users can connect contacts 4X19 and 4X21 in series into the manual closing circuit to achieve synchronism check for manual closing.
4. Closing Acceleration Protection
During manual closing, remote closing, or reclosing operation, if a fault is encountered, the device is equipped with acceleration protection to quickly clear the fault. This protection monitors the current within 3 seconds after the circuit breaker changes from open to closed position. If the current of any phase exceeds the set value, the device trips after a short delay. After 3 seconds, the acceleration protection is automatically disabled.
5. Underfrequency Load Shedding
When the system frequency is below the set value, after a delay, the device trips.
The underfrequency load shedding function can include undervoltage blocking or rate-of-change-of-frequency (df/dt) blocking to prevent maloperation.
Undervoltage blocking criterion: When Uab, Ubc, and Uca are all below the undervoltage blocking set value, underfrequency load shedding is blocked.
Rate-of-change-of-frequency blocking criterion: When Δf/Δt exceeds the rate-of-change-of-frequency blocking set value, underfrequency load shedding is blocked.
6. Undervoltage Load Shedding
When all three line voltages are below the set value, after a delay, the device trips.
The undervoltage load shedding function is blocked if any of the following conditions is met:
a) Any line voltage < 30V
b) ΔU/Δt > voltage rate-of-change blocking set value, where ΔU/Δt is the change in voltage per second for any phase. When the line voltage is below the set value, the voltage rate-of-change is maintained. When the line voltage exceeds the set value, the voltage rate-of-change is updated in real time.
c) All three-phase currents < 0.1In
d) Circuit breaker in open position
e) PT circuit broken
f) Negative-sequence voltage > 5V