Guhertina lê dibeşa derbasên bê sînî yên dergahî yên berz bike
Dua parçeyan ji elektrikî taybetmendiyê ve li ser hevdemîn berdewamkirinên hêz û vekirin da, wan divê phase displacement switching pêşbendi bike jeger hevdemîn virazên wan phase angles-yan di navbera wan de ya biniyên an her du phase-yan 180° derbas bibin. Li demê operasyonê, circuit breaker bi virazên hevdemîn phase angles-yan di navbera wan de hatiye wereşin, ku ji bo connection da phase-displaced currents pêşde dike. Wan currents-yan divê bi tevihatiyê ji circuit breakers-yan li her du tarafta connection-ê wereşin.
Xasî, phase angle difference li navbera rotating vectors-yan ku hevdemîn virazên werazandinê nîşan dide, instantaneous voltage waveforms-yan li ser out-of-sync reşike, ku li demê hêz û vekirin da transient currents û voltage stresses-yan rastî yên bine. Ji bo transient recovery voltage (TRV), ev hêz û vekirin task-ê bi active power sources-yan li her du tarafta circuit breaker-ê re hatine şîne, ku complexity û challenges-yan li ser hêz û vekirin ê zêdetir bikin.
Wekî çawa li Figure 1 de nîşan did, îtin dikarin bi S1 û S2 power sources-yan li navbera wan phase angles-yan din derbas bibin. Li demê circuit breaker li navbera wan hêz û vekirin da, phase angle difference divê transient current-ê li ser zêdetir bike, ku breaking demands-yan li ser circuit breaker-ê bine. Belkî, circuit breaker divê yeterî kapasiteyê bike bi bo handling high-stress conditions-yan, ku safe û reliable switching operations-yan bine.
Key Points Summary
Phase Displacement Switching: Li demê hêz û vekirin da li navbera dua source-yan ku phase angles-yan din derbas bibin pêşbendi bike.
Transient Currents: Transient currents-yan li ser zêdetir bike ji bo phase angle differences-yan.
Transient Recovery Voltage (TRV): Hêz û vekirin task-ê bi active power sources-yan li her du tarafta circuit breaker-ê re hatine şîne, ku complexity-ya zêdetir bike.
Circuit Breaker Requirements: Circuit breaker divê yeterî kapasiteyê bike bi bo handling high-stress conditions-yan ji bo ensure safe û reliable switching operations-yan.
Li fault switching tasks-yan de ku ewle serhildan, Transient Recovery Voltage (TRV) component-ê li load side-ê li ser zero decay bike. Lakin, li phase displacement switching-ê, TRV component-ê li S2 side-ê gradually decay bike bi power frequency recovery voltage (RV) of the S2 source-ê. Wekî çawa li Figure 2 de nîşan did, îtin dikarin bi voltage phase difference-ê li navbera dua source-yan 90° be, û short-circuit reactors-yan impedance-yan ekuvalant bikin.
Belkî, primary feature-ê li phase displacement switching operation-ê TRV peaks-yan li ser zêdetir bike, lakin Rate of Rise of Restriking Voltage (RRRV) û current-ê li ser moderate bine. Ji bo TRV peak-ê li phase displacement conditions-yan li ser zêdetir bike, ew bi cerabî li ser evaluate other complex switching conditions-yan, wek clearing faults on long-distance transmission lines û handling faults on series-compensated lines, bikar anîn.
Key Points Summary:
Load-side TRV: Li hemî cases-yan, TRV component-ê li load side-ê li ser zero decay bike. S2-side TRV in Phase Displacement: Decay bike bi power frequency recovery voltage (RV) of the S2 source-ê.
TRV Peak: Li phase displacement switching-ê li ser zêdetir bike.
RRRV and Current: Li ser moderate bine.
Reference Standard: TRV peak-ê li phase displacement conditions-yan li ser zêdetir bike, ku ew bi cerabî li ser evaluate other complex switching conditions-yan bikar anîn.
Characteristics of TRV in Phase Displacement Switching
Li fault switching scenarios-yan de ku ewle serhildan, Transient Recovery Voltage (TRV) component-ê li load side-ê li ser zero decay bike. Lakin, li phase displacement switching-ê, TRV component-ê li side-ê decay bike bi power frequency recovery voltage (RV) of the source-ê. Ev behavior-ê li Figure 2-ê nîşan did, ku îtin dikarin bi voltage phase difference-ê li navbera dua source-yan 90° be, û short-circuit reactors-yan equal-yan dikarin.
Refined Description
Li fault switching scenarios-yan de ku ewle serhildan, Transient Recovery Voltage (TRV) component-ê li load side-ê always decay bike bi zero. Lakin, li phase displacement switching-ê, TRV component-ê li side-ê decay bike bi power frequency recovery voltage (RV) of the source-ê. Wekî çawa li Figure 2 de nîşan did, îtin dikarin bi 90° phase difference-ê li navbera dua power sources-yan û equal short-circuit reactors-yan.
Belkî, key characteristics-ê li phase displacement switching operation-ê:
Very High TRV Peaks: TRV-yan li ser zêdetir bike bi navbera other switching modes-yan.
Moderate RRRV and Current: Rate of Rise of Restriking Voltage (RRRV) û current levels-yan li ser moderate bine, jeger TRV peaks-yan li ser zêdetir bike.
Ji bo TRV peak-ê li phase displacement conditions-yan li ser zêdetir bike, ev scenario bi cerabî li ser evaluate other special switching conditions-yan, wek:
Clearing faults on long transmission lines
Handling faults on series-compensated lines
Key Points Summary:
Load-side TRV: Always decay bike bi zero li hemî fault switching scenarios-yan.
-side TRV in Phase Displacement: Decay bike bi power frequency recovery voltage (RV) of the source-ê.
TRV Peak: Li phase displacement switching-ê li ser zêdetir bike.
RRRV and Current: Li ser moderate bine.
Reference Standard: TRV peak-ê li phase displacement conditions-yan li ser zêdetir bike, ku ew bi cerabî li ser evaluate other complex switching conditions-yan bikar anîn.
Figure 3 two scenarios-yan nîşan did ku phase displacement conditions-yan pêşde bike. Li first scenario-ê (left image), generator bi grid-ê bi circuit breaker-ê bi incorrect phase angle-ê hêz bike. Li second scenario-ê (right image), different parts-ê li transmission network-ê synchronization-ê hilbike, zevahê li ser short circuit-ê li ser network-ê.
Li both cases-yan, phase-displaced currents-yan bi network-ê flow bike, ku divê bi tevihatiyê ji circuit breakers-yan wereşin. Ev situations-yan challenges-yan li ser power system-ê pêşde bike, ji bo phase displacement-ê divê high transient currents û voltages-yan pêşde bike, ku circuit breakers-yan divê effective-yan handling-ê bikin.
Key Points Summary:
Scenario 1 (Left Image): Generator bi grid-ê bi incorrect phase angle-ê hêz bike, ku phase displacement-ê pêşde bike.
Scenario 2 (Right Image): Different parts-ê li transmission network-ê synchronization-ê hilbike, zevahê li ser short circuit-ê, ku phase displacement-ê pêşde bike.
Phase-Displaced Currents: Li both scenarios-yan, phase-displaced currents-yan bi network-ê flow bike.
Circuit Breaker Requirement: Circuit breakers-yan divê reliably-yan interrupt-ê bike phase-displaced currents-yan bi maintain system stability û safety-yan.
Switching Between Generator and System
Li demê step-up transformer-ê bikaranîn, switching-ê li navbera generator û power system-ê bi high-voltage (HV) side-ê û medium-voltage (MV) side-ê re bikar anîn. Ev switching-ê bi navbera system faults û power plant trips-yan û li synchronization û desynchronization events-yan pêşde bike.
The severity of out-of-phase conditions depends on:
Phase Angle Difference: Ji bo phase angle difference-ê li navbera generator û grid-ê zêdetir bike, out-of-phase condition-ê zêdetir bike.
Rotor Excitation State: Level-ê li rotor excitation-ê li generator-ê bi navbera severity-ê li out-of-phase condition-ê re hatine şîne. Typically, excitation control system-ê divê rapidly-yan reduce-ê bike rotor-ê magnetic field strength-ê bi minimize-ê impact-ê li out-of-phase condition-ê.
Li demê address-ê li these challenges-yan, power plants-yan bi various protective û control devices-yan pêşdest kirin:
Out-of-Step Protection Devices: Îtin detect-ê û prevent-ê bike generator-ê ji loss-ê synchronization-ê bi grid-ê.
Synchronism Check Devices: Îtin ensure-ê bike generator-ê bi grid-ê li correct phase angle-ê hêz bike, ku out-of-phase conditions-yan prevent-ê bike.
Synchronization Control Equipment: Îtin help-ê bike achieve smooth synchronization-ê li navbera generator û grid-ê.
Figure 4 typical layout-ê nîşan did, ku connection-ê li navbera step-up transformer, generator, û power system-ê, û configuration-ê li associated protective û control devices-yan nîşan did.
Key Points Summary:
Switching Location: Switching-ê li navbera generator û power system-ê bi high-voltage (HV) side-ê û medium-voltage (MV) side-ê re bikar anîn.
Out-of-Phase Conditions: Severity-ê li out-of-phase conditions-yan bi phase angle difference û rotor excitation state-ê re hatine şîne.
Protective and Control Devices: Power plants-yan bi out-of-step protection, synchronism check devices, û synchronization control equipment-yan pêşdest kirin bi ensure-ê safe û reliable switching operations-yan.
2-Switching between Two Systems:
Switching-ê li navbera dua power systems-yan typically-yan pêşde bike li ser power unbalance û system instability-yan. Examples-yan refer to large system disturbances, situations-yan li ser system restoration, û due to the mis-operation-ê li protection systems-yan.
The more important transmission lines-yan may be equipped-yan bi out-of-phase blocking-ê li protection system-ê û/or special system-wide protection-ê li apply-ê bike bi prevent-ê separation-ê li systems-yan li severe out-of-phase conditions-yan.
Conclusions of out-of-phase phenomena:
Rated out-of-phase currents-yan proposed-yan bike 25% of the rated short-circuit current. For economic û statistical reasons, minimum peak values-yan li TRV analyses-yan proposed-yan bike: RV of 2.0 p.u. û overshoot of 25% .
As system separation-ê goes with cascading tripping-ê li overhead lines-yan û thus increase-ê li system impedance, maximum value-ê li 25% of the rated short circuit current seems to be reasonable, even today. Maximum value-ê li out-of-phase current-ê important parameter-ê li high voltage circuit breaker capabilities-yan.
Large disturbances-yan show-yan out-of-phase angles-yan much larger than the 105 degree to 115 degree values-yan associated-yan li TRV peak values-yan li standards-yan. This applies-yan both to radial û meshed networks; however, historical events-yan have shown-yan that large out-of-phase angles-yan may occur at the same time as low operating voltages. The combination-ê li large out-of-phase angle û low operating voltage yields-yan TRV peak values-yan similar-yan li those-yan mentioned-yan li standards-yan for situations-yan li relatively low out-of-phase angle û rated voltage (maximum operating voltage).
Transmission system circuit breakers-yan used-yan bi connect-ê û disconnect-ê conventional power plants-yan may be subjected-yan bi out-of-phase switching-ê as well. To disconnect-ê power plants-yan during unstable power swings, same considerations-yan as for system separation-ê applicable-yan albeit with care-yan for possibility-ê that transformer limited fault test condition-ê has to be specified.
To disconnect-ê power plants-yan due to faulty synchronization, similar-yan conditions-yan û requirements-yan as described-yan li medium voltage generator circuit breakers-yan applicable-yan, û simulations-yan necessary-yan bi judge-ê whether design-ê can fulfill-ê duty. Simulations-yan of such events-yan should include-yan response time-yan li protection systems-yan, depression phenomenon-yan li generator voltage, û acceleration/deceleration-yan li rotor-ê bi identify-ê whether out-of-phase current û TRV after false synchronization-ê li generators-yan cover-yan conditions-yan prescribed-yan li user-ê, for instance, 180 degree.
