Farkon Kirki na Tsawo (TRV) a Kofin Kirki na Tsawo Duk Daidai da Circuit Breakers
Amfani da Tatsuniyar Masu Zama a Tsarin Daɗi Daga Iyakokin Daɗi ta Amfani Da Ƙanƙanta Superposition
A cikin amfani da tatsuniyar masu zama na gida saboda iyakokin daɗi a tsarin daɗi, ƙanƙanta superposition yana daya daga budekuka. Ta haka, tushen kiyasin daɗi da ke faruwa aiki a lokacin da iyakokin daɗi ya faru zuwa da ayyukan da suka samu da ita saboda sarkunan daɗi mai tsari da shi da sarkunan daɗi mai tsari da shi, da kuma in duba ita da take daɗe a kan takalma takalma, ana iya samun bayanin daɗi mai kyau game da iyakokin daɗi.
Tatsuniya na Gida A Cikin Iyakokin Daɗi
A lokacin da iyakokin daɗi, ita daɗe da za su faruwa zero ba daɗe a lokacin da iyakokin daɗi. Saboda haka, ita daɗe da za su faruwa sama da ita daɗe da ke faruwa a kan takalma takalma abin da iyakokin daɗi. Idan takalma takalma suna faruza da fadada, yanayi na zama transient recovery voltage (TRV) yana faruwa a kan takalma takalma. TRV yana faruwa idan ita daɗe ya faru zero, kuma yana ci gaba da lamarin daɗi a cikin tsari mai gina. A cikin tsari mai gina, matsayinta TRV yana da muhimmanci wajen aiki da inganci waɗanda suke daɗe.
Muhimmancinta Transient Recovery Voltage (TRV)
Fahimtar daidai na tatsuniyar masu zama a cikin aiki na waɗanda suke daɗe a cikin tsari mai gina yana iya haɗa karin al'adu da inganci waɗanda suke daɗe. Manzarta sun nuna halayen ma'aikata don ƙarfin TRV, wadannan sun taimakawa mahaɗin ƙarfin da kuma aiki na waɗanda suke daɗe.
Tsunukan Tsari Mai Daɗe
Zabubbukan da na biyu ne sun nuna TRV a kan takalma waɗanda suke daɗe a lokacin da ita daɗe ya faruwa zero a cikin tsari mai gina. Har yanzu yana faruwa bayanan daɗi, kamar yadda ake daɗe:
Resistive Load: Don loads mai resistive, ita daɗe ya faruwa zero jin daɗe, wanda yake faruwa TRV mai kyau.
Inductive Load: Don loads mai inductive, voltage a kan inductor yana faruwa maximum idan ita daɗe ya faruwa zero. Saboda inductor yana da energy, wanda yake buƙata da ita a kan components bala (kamar capacitors), yana faruwa oscillations. Wadannan oscillations sun faruwa saboda ƙarfin energy daga inductor zuwa capacitor.
Capacitive Load: Don loads mai capacitive, ita daɗe ya faruwa jin daɗe, kuma voltage yana faruwa jin daɗe. TRV yana faruwa pulse mai voltage mai kyau.
Iyakokin Ita Daɗe Da Kuma Phenomenon Current Chopping
A cikin tsari mai gina, iyakokin ita daɗe yana iya haɗa da phenomena da ake kira current chopping da virtual chopping. Wadannan phenomena suna haɗa da TRV da kuma overvoltage da reignition.
Iyakokin Daɗe Na Adalci Da Kuma Current Chopping
Iyakokin Daɗe Na Adalci: Idan ita daɗe ya faruwa zero natural, wanda yana zama iyakokin daɗe na adalci. A wannan lokaci, TRV yana faruwa within specified limits, kuma ba zan faruwa overvoltage ko reignition ba.
Current Chopping: Idan ita daɗe ya faruwa jin daɗe idan ba ta faruwa zero, wanda yana zama current chopping. Yawancin ita daɗe yana haɗa da overvoltage, wanda yake faruwa high-frequency reignition. Wannan type na iyakokin daɗe na adalci yana haɗa da bahaushe waɗanda suke daɗe da kuma tsari.
Bahaushe na Current Chopping
Idan waɗanda suke daɗe ya faruwa ita daɗe a lokacin da ita daɗe ya faruwa peak, voltage yana faruwa jin daɗe. Idan overvoltage yana faruwa da dielectric strength na waɗanda suke daɗe, reignition yana faruwa. Idan wannan process yana faruwa multiple times, voltage yana faruwa jin daɗe saboda high-frequency reignition. Wannan high-frequency oscillation yana kontrola da electrical parameters na tsari, configuration na tsari, da kuma design na waɗanda suke daɗe, wanda yana faruwa zero crossing before the actual power frequency current reaches zero.
Difafin Daga Current Chopping Da Virtual Chopping
Current Chopping: Yana faruwa idan ita daɗe ya faruwa jin daɗe, wanda yana haɗa da overvoltage da high-frequency reignition.
Virtual Chopping: Yana faruwa idan ita daɗe ya faruwa just before it reaches zero, kuma ita daɗe ya faruwa very close to zero. Wanda yana haɗa da minor overvoltage da reignition.
Koyarar Voltage na Load-Side Da TRV
Zabubbukan da na biyu ne sun nuna koyarar voltage na load-side da TRV a lokacin da scenarios da biyu:
Iyakokin Daɗe at the Current Zero Point: A wannan lokaci, voltage na load-side yana faruwa steadily, da TRV yana faruwa within specified limits, ensuring normal system operation.
Iyakokin Daɗe Before the Current Zero Point (Current Chopping): A wannan lokaci, voltage na load-side yana faruwa jin daɗe, da TRV yana faruwa significantly, potentially leading to overvoltage da reignition. Duk da wannan misali, wanda na biyu yana zama more severe.
Muhimmancinta Fahimtar Current Chopping
Don fahimta daidai na impact of current chopping, consider ignoring the effects of load-side losses. After the current is interrupted at the zero point, the energy stored on the load side is primarily in the capacitors, where the voltage reaches its maximum value. However, if the current is chopped before reaching zero, the energy in the capacitors cannot be fully dissipated, leading to a rapid voltage rise and subsequent overvoltage and reignition issues.
(a) Equivalent Circuit. (b) Arc Interruption at Current Zero Point. (c) Arc Interruption Before Current Zero Point.
Current Chopping and High-Frequency Transient Phenomena
In the case of current chopping, the instability of the arc near the current zero point can lead to high-frequency transient currents flowing into adjacent network components. This high-frequency current overlays on the smaller power frequency current, which is effectively chopped to zero. Specifically:
Arc Instability Near Current Zero: As the current approaches zero, the arc may become unstable, generating high-frequency transient currents. These currents superimpose on the already small power frequency current, further complicating the system's transient response.
Impact of High-Frequency Transient Currents: The presence of high-frequency transient currents can cause overvoltage and reignition, especially in inductive loads. Due to the rapid changes in these currents, they can produce extremely high voltage peaks in a short time, posing a threat to the insulation materials in the system.
Virtual Chopping and Its Effects
In the case of virtual chopping, the arc instability is exacerbated by oscillations with adjacent phases, leading to the generation of high-frequency currents even before the current reaches zero. Specifically:
Mechanism of Virtual Chopping: Virtual chopping typically occurs when the current is close to but has not yet reached zero. At this point, the arc may interact with oscillations from adjacent phases, resulting in high-frequency current generation. This further destabilizes the system and increases the risk of reignition.
Observed Phenomenon: Virtual chopping has been observed in gaseous arcs in air, SF6, and oil. Vacuum arcs are also highly sensitive to current chopping because the arc in a vacuum environment is more susceptible to external conditions, leading to increased instability.
Causes of Chopping and Reignition
The phenomena of chopping and reignition, along with associated high-frequency oscillatory overvoltages, are primarily attributed to the design of the circuit breaker. Specifically:
Design for High Fault Currents: Circuit breakers are typically designed to handle high fault currents. If the design focuses solely on the effective performance for high currents, it may also be equally effective for small currents, attempting to interrupt them before their natural zero crossing.
Adverse Consequences: This design approach can lead to current chopping and reignition, resulting in overvoltage and other undesirable effects. For example, overvoltage can damage the system's insulation, leading to equipment failure or shortened lifespan.
Optimizing Circuit Breaker Design
To effectively address both small and large currents, circuit breaker design should incorporate multiple features to ensure reliable performance under various conditions. Specific recommendations include:
Balancing Performance for Small and Large Currents: Circuit breaker design should consider both small and large currents, avoiding over-optimization for one type at the expense of the other. For instance, adjusting contact materials, arc extinguishing chamber design, and control strategies can help balance performance across different current levels.
Reducing High-Frequency Oscillations: The design should aim to minimize high-frequency oscillations, especially near the current zero point. This can be achieved by introducing appropriate damping elements or optimizing circuit parameters to suppress high-frequency transient currents.
Enhancing Insulation Performance: To handle potential overvoltages, the circuit breaker's insulation design should have sufficient dielectric strength. Selecting high-performance insulating materials and optimizing the insulation structure can ensure reliable insulation even under extreme conditions.
