Zaɓe da kofin current transformers don air-insulated switchgear (AIS CT) suna nufin masu shaida ga bayanai, ingantaccen tashar gaba, da kuma ingantaccen yadda ake amfani da wasu. Yana da kyau a tabbatar da muhimmanci ga mutanen abubuwa, tsari na system, da kuma yanayin al'adu. Abubuwan da suka fi sani ne sun hada da:
1. Muhimmancin Zaɓe
1.1 Kammalawa da Tsarin Karamin Kirkiro
Karamin kirkiro mai karfi: Zaka iya zama daga cikin adadin karamin kirkiro mai karfi wajen kula da koyar da take. Amma a lura, ana zaɓi a matsayin 1.2-1.5 karamin kirkiro mai karfi wajen bincike ba ta haifar da koyar ko kula da koyar a lokacin da take yi waɗanda. Misali, idan karamin kirkiro mai karfi na ƙungiyar 10kV shine 400A, za a iya zaɓi CT ta 500A/5A.
Karamin kirkiro mai tsakiyar: Yana buƙata da kammalawa da karamin kirkiro mai tsakiyar (misali, kayan aiki, relays, etc.), kafin da ma'anar 5A ko 1A (1A yana da ma'anar da ya kamata da koyar da kula da koyar a lokacin da ake amfani da ita).
Class da kammalawa da kammalawan karamin kirkiro (ALF):
CTs da ake amfani da su don bayanai musa kammalawa (misali, 0.2, 0.5) don in bincike masu shaida ga bayanai.
CTs da ake amfani da su don tashar gaba yana da kyau a nemi kammalawan karamin kirkiro (misali, 5P20, 10P30) don in bincike cewa karamin kirkiro mai tsakiyar yana da takamta a cikin adadin da aka tabbatar da shi a lokacin da kula da koyar (5P20 yana nufin cewa idan karamin kirkiro mai kula da koyar shine 20 karamin kirkiro mai karfi, takamta ta ≤5%).
Karamin kirkiro mai karfi: Yana buƙata da karamin kirkiro mai karfi na AIS equipment (misali, 10kV, 35kV, 110kV) da kuma in bincike masu shaida ga hanyar rarrabe (misali, hanyar rarrabe mai yara, hanyar rarrabe mai kasa).
1.2 Kammalawa da Tsarin Form
Yadda ake amfani da ita: Za a zaɓi post-type, through-wall type, ko busbar type saboda yanayin kula da koyar na AIS equipment. Post-type yana da ma'anar wajen amfani da ita a kan waje; through-wall type yana amfani da ita don kula da koyar har zuwa kofin da kuma kofin da ke amfani da ita; busbar type yana da ma'anar da ake amfani da ita a kan busbar, tare da tsari mai kwayoyi.
Adadin windings: Za a zaɓi single-winding (don bayanai ko don tashar gaba faɗa) ko multi-winding (don in bincike abubuwan da suka fi sani don bayanai, tashar gaba, da kuma bayanai, tare da windings da suka da kammalawa da dama) saboda tsarin kula da koyar mai tsakiyar.
Abubuwan da aka amfani da su don kula da koyar: Don waje, za a zaɓi abubuwan da suka da damar tsarin al'adu (misali, silicone rubber, porcelain); don kasa, za a iya amfani da epoxy glass fiber, etc., don in bincike cewa ba sa samu rust ko lafiya da ya haifar da hanyar rarrabe.
1.3 Kammalawa da Yanayin Al'adu
Tsarin al'adu: Don waje, za a duba abubuwan da suka fi sani misali, yanayin dole (idamar -40℃~60℃), tsarin ruwa, yanayin faduwar (hanyar rarrabe yana da kyau a faduwar masu yawan yanayin, misali, hanyar rarrabe yana da kyau a faduwar 3000m, hanyar rarrabe yana da kyau a faduwar 20%), da kuma yanayin tsirrai (za a zaɓi abubuwan da suka da damar tsirrai a kan yanayin da suka da tsirrai, tare da tsirrai ≥25mm/kV).
Dukkantar mekaniki: Yana da kyau a nemi dukkantar mekaniki misali, earthquakes da kula da koyar mai hawa, hasisensu don post-type CTs da ake amfani da su a waje a faduwar masu yawan yanayin, yana da kyau a bincike masu shaida ga tashar gaba.
2. Muhimmancin Kula da Koyar
2.1 Duba A Bincike Masu Shaida Ga Bayanai Ta Kula da Koyar
Duba tsarin kula da koyar da hanyar rarrabe: Duba cewa kula da koyar da hanyar rarrabe babba da kusa, da kuma tsarin hanyar rarrabe ya da kyau; mafi girma hanyar rarrabe ta 2500V megohmmeter, yana da kyau a bincike ≥1000MΩ (a lokacin da take).
Kammalawa da bayanai: Tabbatar da cewa model, karamin kirkiro, class da kammalawa, da kuma abubuwan da suka fi sani na CTs suka daidai da drawing, da kuma nameplate ya da kyau da kyau.
Rahotonin bayanai: Ya kamata a bayyana rahotonin bayanai (misali, transformation ratio test, volt-ampere characteristic test, polarity test) don in bincike masu shaida ga aiki.
2.2 Tashar Gaba
Polarity daidai: L1 (mai kula da koyar) da K1 (mai kula da koyar) na CTs yana da kyau a bincike cewa suka da polarity daidai (subtractive polarity) don in bincike cewa ba ta haifar da tashar gaba ko kula da koyar mai karfi. Polarity yana iya canzawa da DC method ko instrument testing.
Tashar gaba:
Shell yana da kyau a nemi tashar gaba (single-point grounding) tare da tashar gaba ≤4Ω don in bincike cewa ba ta haifar da tashar gaba mai karfi.
K2 end na winding mai tsakiyar yana da kyau a nemi tashar gaba don in bincike cewa ba ta haifar da tashar gaba mai karfi (winding mai tsakiyar ba ta haifar da kula da koyar mai karfi; winding mai tsakiyar yana da kyau a nemi tashar gaba a lokacin da kula da koyar).
Yanayin kula da koyar:
Yana da kyau a kula da koyar a kan circuit breaker ko disconnector don in bincike cewa ba ta haifar da kula da koyar mai karfi.
Ba ta haifar da kula da koyar a kan abubuwan da suka da damar tsirrai (misali, reactors) don in bincike cewa ba ta haifar da tashar gaba.
Tashar gaba: Terminal mai karfi yana da kyau a nemi tashar gaba (meeting torque requirements) don in bincike cewa ba ta haifar da tashar gaba mai karfi; adadin wire mai tsakiyar yana da kyau a bincike ≥2.5mm², da kuma wiring yana da kyau a bincike cewa ba ta haifar da tashar gaba mai karfi.
2.3 Tashar Gaba
Tashar gaba: A lokacin da kula da koyar ko kula da koyar, winding mai tsakiyar yana da kyau a nemi tashar gaba (with a special shorting piece). Ba ta haifar da kula da koyar mai karfi (winding mai tsakiyar ba ta haifar da kula da koyar mai karfi, winding mai tsakiyar yana da kyau a nemi tashar gaba a lokacin da kula da koyar).
Bayanai: Mark the polarity, transformation ratio, and winding purpose on the CT body and the secondary circuit end cover to avoid wrong wiring.
2.4 Calibration After Installation
Transformation ratio review: Confirm that the primary and secondary current transformation ratios are consistent with the design through tests.
Insulation test: Measure the insulation resistance again after installation to ensure that the insulation is not damaged during the installation process.
Overall debugging: Conduct linkage tests with AIS equipment and secondary protection devices to verify the correctness of protection actions (such as overcurrent protection, differential protection).
3. Subsequent Maintenance Points
Regularly clean the insulation surface (especially for outdoor equipment) to remove dirt, bird droppings, etc., to prevent flashover.
Check whether the grounding connection is loose and whether the shell is rusted or leaking oil (oil-immersed CT).
Conduct preventive tests (such as dielectric loss test, partial discharge test) every 3-5 years to evaluate the degree of insulation aging.
By strictly following the selection standards and installation specifications, AIS CT can achieve accurate measurement and reliable protection in the power system, and extend the service life of the equipment.
