Me ke ɗaya ɗin ƙaramin hanyoyi a cikin maimaita da kuma maimaita na ƙaramin hanyoyi? Ma'a ƙaramin hanyoyi an yi amfani da shi wajen ƙara hanyar zama a cikin tsakiyar kungiyar da kuma tsafta hanyar zama. Amma ma'a maimaita na ƙaramin hanyoyi ba a yi amfani da shi wajen ƙara hanyar zama bane. Ma'a ƙaramin hanyoyi akwai karamin hanyoyi mai zurfi don ƙara hanyar zama a cikin tsakiya. Amma ma'a maimaita na ƙaramin hanyoyi ba a kasance da karamin hanyoyi mai zurfi. Ma'a ƙaramin hanyoyi an yi amfani da shi wajen ƙara hanyar zama a cikin tsakiyar kungiya ta hanyar yawan magana. Amma ma'a maimaita na ƙaramin hanyoyi an yi amfani da shi wajen ƙara hanyar zama a cikin tsakiyar kungiya ta hanyar yawan magana.

Matsayin grounding transformer wani ne?

Grounding transformer, na musamman “grounding transformer,” zai iya kategorinsa a matsayin oil-immersed da dry-type idan ana nufin abubuwan da ake amfani da su; kuma a matsayin three-phase da single-phase grounding transformers idan ana nufin tasirin mutane.

Farkon Grounding Transformers da Conventional Transformers

Zaɓi da grounding transformer shine ya kawo neutral point masu inganci don ya shiga arc suppression coil ko resistor idan an yi system a matsayin delta (Δ) ko wye (Y) ba ta da neutral point mai amfani. Wadannan transformers sun amfani da zigzag (ko “Z-type”) winding connections. Farkon mafi yawa daga conventional transformers shine cewa har zuwa da phase winding zai koyar da biyu na farko da ke tsara a hagu da adadin jiki mai karfi. Wannan cutar tana ba zero-sequence magnetic flux tana iya zo a hagu da core limbs, kuma a conventional transformers, zero-sequence flux tana zo a hagu da leakage paths. 

Saboda haka, zero-sequence impedance na Z-type grounding transformer tana da kyau (kusan 10 Ω), kuma na conventional transformer tana da yawan kadan. Idan ake amfani da conventional transformer don ya shiga arc suppression coil, za a bincika cewa capacity na coil ba zai fi 20% da rated capacity na transformer. Amma, Z-type transformer zai iya kula arc suppression coil a 90%–100% na capacity na gaba. Duk da haka, grounding transformers zai iya bayar secondary loads kuma zai iya aikatawa a matsayin station service transformers, don haka zai iya tabbatar da investment costs.

Tsunakan da Ya Kiyaye Grounding Transformers

Grounding transformer tana kawo neutral point masu inganci da grounding resistor, wanda yana da haske mai kyau (yanayi da ma'ana cewa yana da ɗaya da 5 ohms). Duk da wannan, saboda ƙarfashin electromagnetic, grounding transformer tana ba high impedance positive- da negative-sequence currents, kuma tana iya ba ɗaya da small excitation current tana iya zo a windings. A cikin har zuwa da core limb, biyu na winding sections tana tsara a hagu da adadin jiki mai karfi. Idan zero-sequence currents sama daɗi sun zo a cikin windings a hagu da limb, suka taka low impedance, wanda tana ba minimal voltage drop. 

A lokacin fault, windings tana kula positive-, negative-, da zero-sequence currents. Winding tana ba high impedance positive- da negative-sequence currents, amma tana ba low impedance zero-sequence current saboda, a cikin ɗaya da phase, biyu na windings suna tsara a hagu da series da opposite polarity—induced electromotive forces suka sama da magnitude amma suna da tsari, kuma suka haɗa su daɗi.

Many grounding transformers suna amfani domin ba neutral point masu kyautar haske ba, kuma ba suna bayar ƙarfin daidai; saboda haka, many suna da design ba da secondary winding. A lokacin da grid take yi aiki, grounding transformer tana yi aiki a matsayin no-load state. Amma, a lokacin fault, tana kula fault current ɗaya a lokacin daɗi. A low-resistance grounded system, idan yana samu single-phase ground fault, highly sensitive zero-sequence protection tana sanya da taka da faulty feeder. 

Grounding transformer tana yi aiki ɗaya a lokacin daɗi da aka fara fault da operation na zero-sequence protection na feeder. A lokacin daɗi, zero-sequence current tana zo a neutral grounding resistor da grounding transformer, tare da formula: IR = U / R₁, inda U ita ce system phase voltage da R₁ ita ce neutral grounding resistance.

Abubuwa Idan Ba A Iya Kiyaye Grounding Arc Da Inganci Ba

• Intermittent extinction da reignition na single-phase ground arc tana gina arc-ground overvoltages da amfani da amfani 4U (inda U ita ce peak phase voltage) ko kuma yawan daɗi, tana ci gaba. Wannan tana ba lalacewar insulation na electrical equipment, kuma tana iya ba breakdowns a ƙungiyoyin insulation masu kyau da kuma tana iya ba losses masu yawan daɗi.

• Sustained arcing tana ionize surrounding air, tana rage ƙarfin insulation, kuma tana zama da yawan daɗi da za a samu phase-to-phase short circuits.

• Ferroresonant overvoltages zai iya gina, tana zama da yawan daɗi da za a gina damage voltage transformers da surge arresters—zai iya ba arrester explosions. Wannan abubuwa tana rage ƙarfin insulation integrity na grid equipment da kuma tana rage ƙarfin safe operation na entire power system.

Meen Positive-, Negative-, da Zero-Sequence Currents?

• Negative-sequence current: Phase A tana fuskantar Phase B da 120°, Phase B tana fuskantar Phase C da 120°, kuma Phase C tana fuskantar Phase A da 120°.

• Positive-sequence current: Phase A tana kusa Phase B da 120°, Phase B tana kusa Phase C da 120°, kuma Phase C tana kusa Phase A da 120°.

• Zero-sequence current: Duka uku phases (A, B, C) suna cikin tsari—ba ɗaya ba tana kusa ko fuskantar ɗaya.

A lokacin three-phase short-circuit faults da normal operation, system tana da positive-sequence components.
A lokacin single-phase ground faults, system tana da positive-, negative-, da zero-sequence components.
A lokacin two-phase short-circuit faults, system tana da positive- da negative-sequence components.
A lokacin two-phase-to-ground short-circuit faults, system tana da positive-, negative-, da zero-sequence components.

Operating Characteristics of Grounding Transformers

A lokacin da gida na gida a cikin shirye-shirye, mutanen tashar kungiyar tashar zafiya suna yi a harkokin da ba sa mafi yawa. A tsohon bayanin, tashar zafiya yana aiki don ban sha'awar tsakiyar zafiya don ke kan magana mai zafiya. A lokacin da gida na gida a cikin shirye-shirye, ya kunshi tasiri mai yawa a wajen jiragen masu gida da kuma tasiri mai yawa a wajen jiragen ma'aikata, amma ya kunshi tasiri mai yawa a wajen jiragen masu gida da kuma tasiri mai yawa a wajen jiragen ma'aikata, tare da tabbatar da aiki mai dacewa ta hanyar zafiya.

Zafiya Tashar Zafiya Ta Hanyar Dutsen Zafiya

Idan an samun abu mai yawa a kan gida na gida saboda hanyoyi mai yawa, hasashewar gida, matsaloli, ko abubuwan da suka faru, ya kunshi tasiri mai yawa a wajen jiragen masu gida da kuma tasiri mai yawa a wajen jiragen ma'aikata, tare da tabbatar da aiki mai dacewa ta hanyar zafiya.

Tambayar Masu Aiki Da Magana Mai Zafiya

Akwai uku na tambayar masu aiki da magana mai zafiya: under-compensation, full compensation, da over-compensation.

• Under-compensation: Tasiri mai yawa a kan gida na gida saboda hanyoyi mai yawa, hasashewar gida, matsaloli, ko abubuwan da suka faru, ya kunshi tasiri mai yawa a wajen jiragen masu gida da kuma tasiri mai yawa a wajen jiragen ma'aikata, tare da tabbatar da aiki mai dacewa ta hanyar zafiya.

• Over-compensation: Tasiri mai yawa a kan gida na gida saboda hanyoyi mai yawa, hasashewar gida, matsaloli, ko abubuwan da suka faru, ya kunshi tasiri mai yawa a wajen jiragen masu gida da kuma tasiri mai yawa a wajen jiragen ma'aikata, tare da tabbatar da aiki mai dacewa ta hanyar zafiya.

• Full compensation: Tasiri mai yawa a kan gida na gida saboda hanyoyi mai yawa, hasashewar gida, matsaloli, ko abubuwan da suka faru, ya kunshi tasiri mai yawa a wajen jiragen masu gida da kuma tasiri mai yawa a wajen jiragen ma'aikata, tare da tabbatar da aiki mai dacewa ta hanyar zafiya.

Tambaya Da Ake Yi A Hanyar Zafiya Tashar Zafiya Ta Hanyar Dutsen Zafiya

A cikin shirye-shirye da ake yi zafiya tashar zafiya ta hanyar dutsen zafiya, ya kamata a iya kare full compensation. Idan an yi full compensation, za a iya kara series resonance, wanda yake iya kasa dutsen zafiya da tasiri mai yawa. Saboda haka, ana iya yi over-compensation ko under-compensation, amma over-compensation ce da ake yi daidai.

Dalilai Na Yi Over-Compensation

A cikin shirye-shirye da ake yi under-compensation, za a iya kara overvoltage mai yawa a lokacin da gida na gida. Misali, idan an kada wata bari saboda gida ko abubuwan da suka faru, za a iya kara full compensation, wanda yake iya kasa tasiri mai yawa. Under-compensation tana da muhimmanci saboda haka, amma babu hujja da ake iya kare da ita saboda haka.

A lokacin da gida na gida a cikin shirye-shirye da ake yi under-compensation, za a iya kara ferroresonant overvoltages mai yawa. Wannan nasara ne saboda resonance da take faru a kan under-compensated arc suppression coil (donde ωL > 1/(3ωC₀)) da line capacitance (3C₀). Ba a gama wannan resonance a cikin over-compensation ba.

Shirye-shirye suna ci gaba, kuma capacitance na gida suna ci gaba. A cikin over-compensation, dutsen zafiya da aka saka za a iya yi aiki har zuwa lokacin da ya kusa. Amma a cikin under-compensation, idan an yi kadan, za a bukata a yi kadan da ake yi compensation capacity.

A cikin over-compensation, tasiri mai yawa ya kunshi a kan gida na gida. Ba lokacin da gida na gida a cikin shirye-shirye da ake yi under-compensation, idan an kada wata bari saboda gida ko abubuwan da suka faru, za a iya kara full compensation, wanda yake iya kasa tasiri mai yawa. Under-compensation tana da muhimmanci saboda haka, amma babu hujja da ake iya kare da ita saboda haka.

Muhimmiyar Bayani

Tashar zafiya tana da aiki daidai, tana iya kusan koyar 35 kV zuwa 380 V don in taimaka wa battery charging, SVG fan power, maintenance lighting, da abubuwan da suka faru.

A yanzu, akwai karfin da ake yi da cable lines saboda overhead lines. Idan an samun abu mai yawa a kan gida na gida, neutral grounding via arc suppression coils ba zai iya kawo gida na gida. Saboda haka, substation na musamman tana da low-resistance neutral grounding scheme. Wannan tura tana da single-phase ground-fault protection don in kada wata bari.