Ga wasu kisan Kafin Daukan Tsabta? Kyakkyawan Funtuka da Fadada
Funktsiya na Surge Arresters
Idan karshe kashi da shiga kungiyar karamin kashi na yamma zuwa birnin karamin kashi ko kuma tashar da ke gaba, zai iya haifar da kungiyar kashi ko kuma tukar hanyar karshen kayayyakin kashi. Saboda haka, idan ake fadada aiki – wanda ake kira surge arrester – a cikin karamin kashi (kamar yadda ake nuna a Figure 1), zai ya faru daga baya a lokacin da karshe kashi ya samu inganci da take sa.
Arrester yana fitar da kashi mai yawa, kuma ya kawo karshe kashi da kuma muhimmanci kayayyakin kashi. Idan kashi ta zama lafiya, surge arrester yana dogara da halayensa, kuma taimakawa masana kashi a kan yawan kashi na lafiya.
Aiki na surge arrester yana gudanar da uku abubuwa:
Koyarwa da kyau bayan volt-second characteristic na arrester da kyau bayan protected insulation.
Residual voltage na arrester yana da kyau bayan impulse withstand strength na protected insulation.
Protected insulation yana da kyau cikin protective distance na arrester.
Muhimmancin surge arresters:
Ba zai iya fitar da kashi a lokacin da yake aiki a kan yawan kashi na lafiya, amma ya kamata zai iya fitar da kashi da kyau da amanin a lokacin da karshe kashi.
Yana da kyau a yi self-recovery ba da damar fitar da kashi (ya ni bincika a kan high-impedance state da kuma hada da follow current).
Abubuwan da suka fiye-game da surge arresters:
Continuous operating voltage: Inganci na yawan kashi da ake kula a kan yawan kashi. Yana da kyau duba ko kuma mafi yawan kashi na phase-to-ground.
Rated voltage (kV): Mafi yawan kashi na short-time power frequency (ko kuma arc extinguishing voltage). Arrester zai iya aiki da kuma hada da arc under this voltage, amma ba zai iya aiki da damar a kan yawan kashi na wannan. Wannan shine parametar na asali don design, characteristics, da structure na arrester.
Power frequency withstand volt-second characteristic: Yana nuna kyau bayan metal-oxide (misali ZnO) arrester a kan yawan kashi da ke guda a kan yadda ake nuna.
Nominal discharge current (kA): Peak value na discharge current wanda ake amfani da ita don kategorize ratings na arrester. Don systems 220 kV da kadan, ba zai iya duba 5 kA.
Residual voltage: Kashi wanda yake cikin terminal na arrester idan an fitar da kashi. Ana iya tabbatar da shi a matsayin mafi yawan kashi wanda arrester zai iya aiki a kan yawan kashi na fitar da kashi.
Abunawa da Structure na Surge Arresters
Abunawa masu yawa na surge arresters sun haɗa da valve-type, tube-type, protective gaps, da kuma metal-oxide arresters.
(1) Valve-Type Surge Arresters
Valve-type arresters sun haɗa da conventional valve-type da magnetic-blow valve-type. Conventional type sun haɗa da FS da FZ series; magnetic-blow type sun haɗa da FCD da FCZ series.
Alamomin model designation suna nufin:
F – Valve-type arrester;
S – For distribution systems;
Z – For substations;
Y – For transmission lines;
D – For rotating machines;
C – With magnetic-blow discharge gap.
Valve-type arrester yana da flat spark gaps a cikin silicon carbide (SiC) resistor discs (valve blocks), wanda ake kwalla a cikin housing na porcelain, tare da terminal bolts na waje don aiki. Silicon carbide resistor yana da nonlinear characteristics: yana da high resistance a lokacin da yake aiki a kan yawan kashi na lafiya, kuma yana daɗe da damar a lokacin da karshe kashi.
A lokacin da yawan kashi na lafiya, spark gaps yana daɗe non-conductive. Idan karshe kashi na lightning yana faru, spark gaps yana kawo. Resistance na SiC blocks yana daɗe da damar, kuma yana bude lightning current zuwa ground. Ba da karshe, SiC blocks yana da high resistance a kan yawan kashi na lafiya, kuma spark gaps yana hada da yawan kashi, kuma yana dogara da aiki na system. Hakan yana nuna aiki da kyau – open for lightning current and closed for power frequency current – saboda haka ana kiran shi "valve-type" arrester.
(2) Protective Gaps and Expulsion (Tube) Arresters
Protective gaps suna da muhimmanci a kan protection na lightning. Suna da main gap da auxiliary gap. Main gap yana da angular configuration da kuma horizontal mounting don taimakawa arc extinction. Auxiliary gap yana da series connection da main gap don taimakawa tsabta da kungiyoyi. Saboda arc-quenching capability na biyu, protective gaps suna amfani da automatic reclosing devices don taimakawa aiki na system.
Expulsion (tube-type) arrester yana da spark gap a cikin gas-generating tube, wanda ake kira rod and ring electrodes. Yana da internal da kuma external gaps. Arrester tube yana da materials kamar fiber-reinforced phenolic resin wanda yana daɗe da gas da yawa a lokacin da yake gida. Idan karshe kashi na lightning yana faru, internal da external gaps yana kawo, kuma yana bude lightning current zuwa ground. Power frequency current yana da arc da yake gida, kuma yana bude tube wall da kuma yana daɗe da gas da yawa a cikin end, kuma yana hada da arc. External gap yana dogara da insulation, kuma yana kawo arrester daga system, kuma yana taimakawa aiki na lafiya.
Saboda expulsion arresters suna da kyau a yi gas da yawa don arc extinction, short-circuit currents da yawa zai iya bude gas da yawa, kuma zai iya kawo tube da mechanical strength, kuma zai iya kawo rupture ko kuma explosion. Saboda haka, expulsion arresters suna amfani da su a outdoor installations.
(3) Gapless Metal-Oxide (Zinc Oxide) Surge Arresters
Wadanda ake kira varistor arresters, wadanda ake buƙata a 1970s. Daga silicon carbide valve-type arresters, gapless metal-oxide arresters ba suna da spark gaps, kuma suna amfani da zinc oxide (ZnO) instead of silicon carbide. Suna da ZnO varistor discs da nonlinear voltage-current characteristics: a lokacin da yake aiki a kan yawan kashi na lafiya, yana da high resistance, kuma a lokacin da karshe kashi, yana daɗe da damar, kuma yana bude surge current da kyau.
Metal-oxide arresters suna da protection characteristics da yawa, high discharge capacity, low residual voltage, compact size, da kuma easy installation. Suna da yawa a kan protection na electrical equipment na both high- da kuma low-voltage.
(4) Gapped Metal-Oxide (Zinc Oxide) Surge Arresters
Wadanda sun haɗa da ZnO resistor discs da spark gap a cikin composite housing. Gap unit yana da two disc-shaped electrodes enclosed in a ceramic ring. Su ne da yawa a kan non-effectively grounded neutral systems. A lokacin da single-phase-to-ground faults ko kuma arc grounding, transient overvoltages da yawa zai iya faru, wadanda gapless ZnO arresters ba zai iya da yawa. Gapped ZnO arresters suna da yawa: a lokacin da moderate overvoltages kamar single-phase grounding ko kuma low-level arc grounding, series gap yana daɗe inactive, kuma yana kawo arrester daga system.
Idan overvoltage yana daɗe mafi yawa, gap yana kawo, kuma nonlinear characteristics na ZnO blocks yana kawo residual voltage across the arrester. Follow current yana da yawa da yake daɗe, kuma yana daɗe da damar, kuma yana taimakawa insulation protection na transformers da kuma equipment da ke gaba.
Test Items and Standards for Surge Arresters
(1) Insulation Resistance Measurement
Amfani da megohmmeter na 2500 V ko da yawa. Don arresters rated 35 kV da kadan, insulation resistance yana da kyau duba 2500 MΩ; don wadanda da kadan 35 kV, yana da kyau duba 1000 MΩ.
(2) Measurement of DC Voltage at 1 mA and Leakage Current at 75% of This Voltage
Apply a DC voltage to the arrester. As the voltage increases, the leakage current gradually rises. Record the voltage value when the current reaches 1 mA. Then reduce the voltage to 75% of this value and record the leakage current, which should not exceed 50 μA.
(3) AC Leakage Current under Operating Voltage
Measure the total current, resistive current, or power loss under operating voltage. The measured values should show no significant change compared to initial values. If the resistive current doubles, the arrester must be de-energized for inspection. If the resistive current increases to 150% of the initial value, the monitoring cycle should be appropriately shortened.
These tests can detect defects such as moisture ingress or aging of arrester valve blocks, surface cracks, and insulation deterioration.
