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Bayanan Maimaita na Tsari da Tashin Pre-Strike a Switchgear
A switchgear, musamman a circuit breakers (CB) da load break switches (LBS), maimaita na tsari yana nufin yanayin faruwa da tsari ne lokacin da takalma suka faru. Wannan yanayi ba ta faru ba a lokacin da takalma suka shiga kawai, amma zai iya faru zuwa mutane da dama daidai saboda tashin pre-strike. Daga baya ita ce bayanin wannan tashin da ma'anaicinsu.
1. Pre-Strike: Yanayin Faruwa da Tsari A Bisa Da Takalma Su Shiga Kawai
•    Dielectric Breakdown: Lokacin da takalma suka shiga kawai a lokacin da suka faru, mediumin insuliya (kamar hawa, SF6, ko vacuum) wanda yake da suka faru a kan biyu su ke canza. Wannan yana faru saboda field din karamin jiki a kan gap da ke da shi a kan takalma suke so. Idan karfiyar field ya fi yawa da dielectric strength da ke da mediumin insuliya, gap ya faru, kuma arc ya faru.
•    Build-Up na Electrical Field: Field din karamin jiki a kan takalma su ke so a lokacin da suka shiga kawai. Wannan field ya dogara da voltage da ke da shi a kan takalma su da kima da distance da ke da biyu su. Idan field ya fi yawa, ya yi ionization ga gas molecules a kan gap, kuma ya faru conductive path da tsari ya faru.
•    Arc Initiation: Arc ya faru a baya da takalma su shiga kawai, zuwa mutane da dama daidai. Wannan faruwar arc a baya da shiga kawai ana kiranta pre-strike. A lokacin da pre-strike, arc ya faru a kan gap mai kafin, kuma tsari ya faru a kan arc, ba a bata da takalma su shiga kawai ba.
2. Ma'anaicin Pre-Strike
•    Excessive Melting of Contact Surfaces: Idan energy da ke da shi a pre-strike ya fi yawa, zai iya canza surface da ke da takalma su. Wannan yana da muhimmanci a cikin tushen short-circuit, inda tsari ya fi yawa. Metal mai kafin a kan surface da ke da takalma su zai iya canza welding da takalma su, inda biyu suke fuse.
•    Welding of Contacts: Welded contacts zai iya ba sauka da switching device da take faru daidai a kan next opening command. Idan operating mechanism da ke da switchgear ba ta ba da force da ya fi yawa don canza welded points, device zai iya canza fail to open properly, kuma zai iya canza safety hazards da damage na equipment.
•    Short-Circuit Current Characteristics: Short-circuit currents suna da DC component, wanda zai iya canza peak value da ke da tsari ya fi yawa da pure AC short-circuit current. Wannan increased peak current zai iya canza effects da pre-strike, kuma zai iya canza contact damage da welding da yawa.
•    Arc Voltage Dependence: Voltage da ke da arc (arc voltage) yana da muhimmanci da interrupting medium da ke da switchgear. Hatta a lokacin da arc length ya fi kadan, zai iya canza significant voltage drops a kan electrodes. Wannan shine saboda arc resistance ba da uniform along its length, kuma regions a kan electrodes suna da higher resistance saboda concentration of heat and ionized particles.
3. Making Under Short-Circuit Conditions
•    Circuit Breakers (CB): A circuit breakers, making operation under short-circuit conditions yana da abubuwa. High current levels da presence of a DC component zai iya canza intense arcing da contact damage. Modern circuit breakers suna da advanced materials and cooling mechanisms don canza wannan effects, amma pre-strike ba suka cika ba.
•    Load Break Switches (LBS): Load break switches suna da abubuwa da pre-strike a lokacin da suka faru, musamman a high-current applications. Amma, LBS devices suna da use a lower-voltage and lower-current applications compared to circuit breakers, kuma risk of severe contact damage yana da yawa.
4. Stages of the Making Operation in Switchgear
Making operation of switchgear zai iya canza zuwa several stages, kamar yadda aka nuna a figure:
•    Stage 1: Initial Approach of Contacts: Takalma suka faru a kan biyu su, kuma electrical field da ke da biyu su ke so. A wannan stage, ba tsari da faru, amma potential for pre-strike ke dogara.
•    Stage 2: Pre-Strike Arc Formation: Lokacin da takalma suka shiga kawai, electrical field ya fi yawa da dielectric strength da ke da insulating medium, kuma dielectric breakdown ya faru. Pre-strike arc ya faru, kuma tsari ya faru a kan arc a baya da takalma su shiga kawai.
•    Stage 3: Contact Touch and Arc Transfer: Takalma suka shiga kawai, kuma arc ya transfer from the gap between the contacts to the contact surfaces. Tsari ya faru a kan now-closed circuit.
•    Stage 4: Steady-State Operation: Ba a bata da takalma su suka shiga kawai, system ya faru a steady-state operation, kuma tsari ya faru a kan closed contacts without any arcing.
5. Mitigation Strategies
Don canza effects da pre-strike da contact welding, several design and operational strategies zai iya amfani da shi:
•    Use of High-Dielectric-Strength Insulating Mediums: Amfani da insulating mediums da high dielectric strength, kamar SF6 gas ko vacuum, zai iya canza likelihood of pre-strike by requiring a higher electrical field to initiate breakdown.
•    Advanced Contact Materials: Amfani da contact materials da high melting points and good thermal conductivity zai iya taimaka canza contact damage during pre-strike. Materials like copper-tungsten alloys suna da amfani a high-voltage switchgear.
•    Cooling Mechanisms: Incorporating cooling mechanisms, such as puffer systems or forced gas flow, zai iya taimaka canza heat from the arc and reduce the temperature of the contact surfaces, minimizing the risk of welding.
•    Mechanical Design Enhancements: Ensuring that the operating mechanism provides sufficient force to break any welded points during the opening operation zai iya canza switchgear from failing to open properly.
•    Protection Systems: Implementing protection systems, such as overcurrent relays and fault detection mechanisms, zai iya taimaka detect and respond to short-circuit conditions more quickly, reducing the duration and intensity of the arc.
Conclusion
Tashin pre-strike, inda arc ya faru a baya da takalma su shiga kawai, yana da muhimmanci a making operation in switchgear. Yana iya canza excessive contact damage, welding, and potential failure of the switching device. Fahimtar factors da ke canza pre-strike, kamar build-up na electrical field and characteristics of the insulating medium, yana da muhimmanci don designing and operating reliable switchgear. By employing appropriate mitigation strategies, such as using high-dielectric-strength insulating mediums, advanced contact materials, and cooling mechanisms, effects of pre-strike zai iya canza, ensuring safe and reliable operation of switchgear in both circuit breakers and load break switches.