Vipi ni Insulation Coordination katika Mipango ya Umeme?

Ni ni Nini Insulation Coordination katika Mipango ya Umeme?

Insulation Coordination Imeulizwa

Insulation coordination ni mazingira ya kifaa ya insulation ya umeme ili kurekebisha udhaifu wa mfumo na kuhakikisha kuwa marafiki ya kupata ushauri zinaweza kufanyika ikiwa kuna matatizo.

Volts za Mfumo

Kuelewa volts za nominal na maximum za mfumo ni muhimu kwa kutengeneza insulation ya mipango ya umeme ili kusimamia tofauti za masharti ya kazi.

Nominal System Voltage

Nominal System Voltage ni voltage ya phase kwa phase ya mfumo ambayo mfumo unatumika kulingana nayo. Kama vile 11 KV, 33 KV, 132 KV, 220 KV, 400 KV systems.

Maximum System Voltage

Maximum System Voltage ni voltage ya power frequency ya juu zaidi ambayo inaweza kutokea kwa muda mrefu wakati system yako bila mzigo au mzigo dogo. Inametathmini kwa njia ya phase kwa phase.

Orodha ya tofauti za nominal system voltage na maximum system voltage zao zinapatikana chini kwa rujukan,

NB – Inaonekana kutoka kwenye meza hii kwamba mara nyingi maximum system voltage ni 110 % ya nominal system voltage yenye sambamba hadi kiwango cha 220 KV, na kwa 400 KV na zaidi ni 105 %.

Earthing Factor

Hii ni uwiano wa rms phase kwa earth power frequency voltage chache kwenye phase sahihi wakati kuna fault ya earth na rms phase kwa phase power frequency voltage ambayo ingeweza kupata kwenye eneo lolote lisilo na fault.

Uwiano huu huonyesha, kwa umma, masharti ya earthing ya mfumo kama inavyoonekana kutoka kwenye eneo la fault lililochaguliwa.

Effectively Earthed System

Mfumo unatafsiriwa kama effectively earthed ikiwa factor of earthing haijiwezi kupanda zaidi ya 80 % na non-effectively earthed ikiwa haijafanya hivyo.

Factor of earthing ni 100 % kwa mfumo wa isolated neutral, na ni 57.7 % (1/√3 = 0.577) kwa solidly earthed system.

Kiwango cha Insulation

Vifaa vyenye viwango vya umeme vinapaswa kuzingatia tofauti za transient over voltage isiyotumaini kwa muda wa kazi wote wake. Vifaa vilivyopaswa kukubalika kuchelewa lightning impulses, switching impulses na/au short duration power frequency over voltages. Kulingana na kiwango cha juu zaidi cha impulse voltages na short duration power frequency over voltages ambazo component moja ya mfumo wa umeme inaweza kukubalika, kiwango cha insulation cha high voltage power system linatumika.

Wakati wa kutathmini kiwango cha insulation cha mfumo unaorated chini ya 300 KV, lightning impulse withstand voltage na short duration power frequency withstand voltage zinachukua hatua. Kwa vifaa vya rated more or equal 300 KV, switching impulse withstand voltage na short duration power frequency withstand voltage zinachukua hatua.

Lightning Impulse Voltage

Matatizo ya mfumo yanayotokea kwa sababu ya lightning ya asili, yanaweza kuonyeshwa kwa tatu tofauti za wave shapes. Ikiwa lightning impulse voltage inazunguka umbali fulani kwenye transmission line kabla ya kupata insulator, shape yake inapata full wave, na hii wave inatafsiriwa kama 1.2/50 wave. Ikiwa wakati anazunguka, lightning disturbance wave inachelewesha flash over kwenye insulator, shape ya wave inakuwa chopped wave. Ikiwa lightning stroke inahit directly insulator, lightning impulse voltage inaweza kukata steepest hadi ikapata flash over, kucha voltage very steep collapse. Tatu waves hizi ni tofauti sana kwa muda na shape.

Switching Impulse

Wakati wa kufanya switching operation, inaweza kutokea uni-polar voltage. Wave form yake inaweza kuwa periodically damped au oscillating one. Switching impulse wave form ina front steep na long damped oscillating tale.

Short Duration Power Frequency Withstand Voltage

Short duration power frequency withstand voltage ni prescribed rms value ya sinusoidal power frequency voltage ambayo vifaa vya umeme vinapaswa kukubalika kwa muda specific wa kawaida 60 sekunde.

Vifaa vya Protection

Over voltage protective device like surge arrestors au lightning arrestors zimeundwa kubalika kiwango fulani cha transient over voltage zaidi ya ambacho devices hazinaenergy surge energy kwenye ground na kwa hivyo kukabiliana na kiwango cha transient over voltage hadi kiwango fulani. Hivyo basi transient over voltage haikawezi kupanda zaidi ya kiwango hilo. Kiwango cha protection cha over voltage protective device ni highest peak voltage value ambayo si lazima kumpanda zaidi kwenye terminals ya over voltage protective device wakati switching impulses na lightening impulses zinatumika.

Using Shield Wire au Earth Wire

Lightning surges kwenye overhead transmission lines zinaweza kutokana na direct lightning strikes. Kutengeneza shield wire au earth wire chini ya top conductor kwenye kiwango cha height kinaweza kuhakikisha protection ya lines hizi. Ikiwa shield wire hii imeunganishwa vizuri kwenye transmission tower na tower imewekwa vizuri, inaweza kupunguza direct lightning strikes kwenye conductors yoyote kwenye protective angle ya earth wire. Shield wires pia hupunguza electrical substation na vifaa vyao kutokana na lightning.

Conventional Method of Insulation Coordination

Kama ilivyodhibitiwa, components katika electrical power system zinaweza kuchelewa na varying levels za transient voltage stresses, including switching and lightning impulse voltages. Kutumia vifaa vya protection kama lightning arrestors inaweza kukabiliana na maximum amplitude ya transient over voltages hizi. Kwa kutengeneza insulation levels zaidi ya protection level ya vifaa vya protection, ukubwa wa insulation breakdown unaweza kupunguzika. Hii husaidia kuwa chochote transient over voltage kilichopata insulation ni chini ya safe limits zilitengenezwa na protection level.

Kwa ukuaji, impulse insulation level inatumika 15 hadi 25 % zaidi ya protection level voltage ya vifaa vya protection.

Statistical Methods of Insulation Coordination

Katika transmission voltages zisizidi, length ya insulator strings na clearance katika air hayajarudi linearly na voltage lakini approximately to V1.6. Idadi ya disc ya insulator inayohitajika kwenye suspension string kwa different over voltages inaonyeshwa chini. Inaonekana kuwa increase in the number of disc ni tu kidogo kwa 220 KV system, na increase in the over voltage factor kutoka 2 hadi 3.5 lakini ina ongezeko kasi kwa 750 kV system. Hivyo, ingawa itaweza kuwa economically feasible kuhakikisha protection ya low voltage lines hadi over voltage factor wa 3.5 (kama), hakikika si economically feasible kuwa na over voltage factor zaidi ya about 2 hadi 2.5 kwenye high voltage lines. Katika high voltage systems, ni switching over voltages zinazokuwa predominant. Lakini, zinaweza kukabiliana na proper design ya vifaa vya switching.

Economic Efficiency

Insulation coordination lazima lizungumze na technical requirements na economic feasibility, hasa kwenye high voltage levels.