Turabin da tashin kula na mafi girma na gida da tattaunawa
A cikin Zafi
Maimaitaccen hanyar birnin da ke maimaita masana hanyar birnin da kuma wurare, su ne mutanen uku mai yawa.
A cikin ANSI C57.12.40 - 1982, ana kategorize masu hanyar birnin a matsayin zafin ko karamin shugaban zamfara:
Amma ana amfani da masana hanyar birnin a cikin gwamnati, musamman a cikin tafkin gwamnati. A nan, ana iya amfani da masana hanyar birnin a cikin zafi idan an yi aiki a kan tafki da kyau da kuma a sake ita. Ana iya zama da amfani da abubuwa mai tsabta da kuma abubuwa mai ruwa mai karshen tsabta.
Abubuwan Fanni
Ana haɗa masana hanyar birnin da na biyu mai fadada, wanda yake iya faɗi, kasa, ko kusan gabatarwa ta hanyar birnin zuwa talakawa. Mutanen fadada masu ƙananan ta su ne 216Y/125 V da 480Y/277 V. Tafarar 1 a nan ta bayyana abubuwan fanni na gargajiya.
Masana hanyar birnin da take da damar 1000 kVA ko kadan ne suka da takarda 5%; don masana hanyar birnin da damarsu ta fi 1000 kVA, takardinsu na gargajiya ce 7%.
Mushawarar X/R (reactance-to-resistance) yana cikin 3 zuwa 12. Masana hanyar birnin da suka da takarda ƙarin (kamar masana hanyar birnin da take da takarda 4%) suna da ƙarfin ƙarin da kuma ci gaba masu ƙananan fadada. (Ci gaba masu ƙananan fadada na ƙarfi don in baɓanta ƙananan a cikin hanyar birnin.) Amma ƙarfin ƙarin ta shafi ƙarfin da ke faruwa a cikin hanyar birnin da kuma baƙin lada ga masana hanyar birnin.
Masana hanyar birnin da take da damar 1000 kVA ko kadan ne suka da takarda 5%; don masana hanyar birnin da damarsu ta fi 1000 kVA, takardinsu na gargajiya ce 7%. Mushawarar X/R (reactance-to-resistance) yana cikin 3 zuwa 12. Masana hanyar birnin da suka da takarda ƙarin (kamar masana hanyar birnin da take da takarda 4%) suna da ƙarfin ƙarin da kuma ci gaba masu ƙananan fadada. (Ci gaba masu ƙananan fadada na ƙarfi don in baɓanta ƙananan a cikin hanyar birnin.) Amma ƙarfin ƙarin ta shafi ƙarfin da ke faruwa a cikin hanyar birnin da kuma baƙin lada ga masana hanyar birnin.
Hanyoyin Gabatarwa Talakawa
Dukkan masana hanyar birnin suna haɗa da delta - grounded wye. Wannan hanyo yana saukar ƙananan zero-sequence, wanda yake iya ƙara ƙarfin gabatarwa talakawa a kan kable masu ƙananan. Saboda haka, ana iya amfani da ground-fault relay mai ma'ana a kan circuit breaker masu substation. Saukan ƙananan zero-sequence ta kula ƙarfin da ke faruwa a kan kable neutrals da kable sheaths, kamar ƙananan harmonics, musamman harmonic na uku. Idan an samu ƙananan fadada zuwa talakawa a kan ƙananan masu ƙananan, circuit breaker masu feeder yake ci ƙarfin, amma masana hanyar birnin za su iya ci ƙarfin ƙananan fadada har zuwa lokacin da duk network protectors su yi aiki (da kuma wasu za su iya ƙungiyar).
A cikin hanyar birnin da ba a gabatarwa, ƙananan fadada zuwa talakawa yana ƙara ƙarfin neutral-point, wanda yake iya ƙara ƙarfin phase-to-neutral masu ƙananan da ba su samu ƙananan zuwa ƙarfin phase-to-phase. Abubuwan da suka amfani phase-to-neutral za su iya ƙara ƙarfin overvoltage. Wasu hanyoyin birnin suna amfani da hanyoyin grounded wye-grounded wye.
Wannan hanyo yana da ƙarfin da yake da kyau don feeders mai ƙarfin. Idan an samu ƙananan fadada zuwa talakawa a kan ƙananan masu ƙananan, circuit breaker masu feeder yake ci ƙarfin. Don ƙarfin backfeed zuwa ƙananan masu ƙananan, hanyoyin wye-wye yana bayyana reference point mai gabatarwa, wanda yake iya ƙara ƙarfin overvoltage. Hanyoyin grounded wye-grounded wye ta kula ƙarfin ferroresonance idan masana hanyar birnin yake yi single-pole switching.
Dukkan masana hanyar birnin suna da core type, inda tsohon core yana da either three-legged (three-phase, three-column) ko five-legged (three-phase, five-column). Core na biyar, bai ita core stacked ko wound core, yana da ƙarfin da yake da kyau don hanyoyin delta-grounded wye (amma ba don hanyoyin grounded wye-grounded wye saboda abubuwan tank heating). Core na baya yana da ƙarfin da yake da kyau don duka hanyoyin da aka bayyana a nan.
