PSL 691U Line Protection and Control Device

Guodian Nanzi PSL-691U Line Protection and Control Device

1 Functions
1. Three-stage overcurrent protection (can be initiated by composite voltage, with directional option)
2. Three-stage zero-sequence overcurrent protection (with directional option)
3. Overload alarm
4. Reclosing
5. Manual closing with synchronization check
6. Closing acceleration protection
7. Underfrequency load shedding
8. Undervoltage load shedding
9. Small current grounding line selection
10. I, U, P, Q, Cosφ, active energy, reactive energy, 14 channels of switch status acquisition
11. GPS time synchronization (minute pulse, second pulse, or IRIG-B method)

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., reclosing is ready to operate). After reclosing charging is completed, the running light flashes. If reclosing is not ready, the running light remains steady and does not flash.
After reclosing charging is completed, once a protection trip or unintended breaker trip occurs, reclosing is initiated after the reclosing delay.
After reclosing is initiated, it operates based on the selection of no-voltage check, synchronization check, or no check.
a) Synchronization check reclosing condition: | ∠Ux －∠Uab － ∠φ | ≤ synchronization check closing angle
Note: ∠Ux is the line voltage angle;
∠Uab is the bus 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 synchronization check reclosing.
c) No-check reclosing: Does not evaluate the magnitude or phase angle of Ux, directly closes.
If reclosing cannot be completed within 10 seconds after initiation, the reclosing process automatically ends.
Reclosing is automatically blocked during manual tripping, remote tripping, overload, underfrequency load shedding, or undervoltage load shedding actions.
3. Manual closing with synchronization check
When the relationship between Ux and Uab meets the synchronization check reclosing condition and manual closing with synchronization check is enabled, contacts 4X19 and 4X21 close. Users can connect contacts 4X19 and 4X21 in series into the manual closing circuit to achieve manual closing with synchronization check.
4. Closing acceleration protection
During manual closing, remote closing, or reclosing actions, if a fault is encountered, acceleration protection is provided to quickly clear the fault.
This protection monitors the current within 3 seconds after the switch changes from open to closed position. If the current of any phase exceeds the set value, after a short delay, the device trips. After 3 seconds, the acceleration protection automatically exits.
5. Underfrequency load shedding
When the system frequency is below the set value, after a delay, the device trips.
Underfrequency load shedding 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.
Undervoltage load shedding 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 any voltage per second. When the line voltage is below the set value, the voltage rate-of-change is held. When the line voltage is above 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 broken wire
f) Negative sequence voltage > 5V