Nyob rau hauv tsab xov xwm koj yuav kawm txog qhov kev tiv thaiv txawv li cas, nws ua haujlwm li cas, nws muaj qhov zoo li cas. Nws tseem yuav tham txog dab tsi yog qhov tsis zoo ntawm qhov sib txawv ntawm kev tiv thaiv kab hluav taws xob. Koj tseem yuav kawm txog cov tswv yim siv los tiv thaiv cov khoom siv thiab cov kab hluav taws xob.
Hom kev tiv thaiv sib txawv tam sim no suav tias yog qhov ntau tshaj plaws thiab ceev tshaj plaws. Nws muaj peev xwm tiv thaiv qhov system los ntawm theem-rau-theem luv circuits. Thiab nyob rau hauv cov tshuab uas siv lub hauv paus ruaj khov nruab nrab, nws tuaj yeem yooj yim tiv thaiv qhov tshwm sim ntawm ib-theem luv luv circuits. Qhov sib txawv ntawm kev tiv thaiv yog siv los tiv thaiv cov kab hluav taws xob, lub zog hluav taws xob siab, transformers, generators.
Muaj ob hom kev tiv thaiv sib txawv hauv tag nrho:
- Nrog kev sib tw sib npaug.
- Nrog rau kev siv tam sim no.
Zaj lus no yuavob qho tib si ntawm kev tiv thaiv kev sib txawv no raug txiav txim siab txhawm rau kawm kom ntau li ntau tau txog lawv.
Kev tiv thaiv sib txawv siv cov dej ntws tawm
Lub hauv paus ntsiab lus yog qhov tam sim no piv. Thiab kom paub meej dua, muaj kev sib piv ntawm qhov tsis muaj nyob rau ntawm qhov pib ntawm lub caij, kev tiv thaiv uas tau ua tiav, nrog rau qhov kawg. Cov tswv yim no yog siv rau hauv kev siv ntawm cov longitudinal hom thiab transverse. Cov qub yog siv los xyuas kom muaj kev ruaj ntseg ntawm ib txoj kab hluav taws xob, hluav taws xob motors, transformers, generators. Longitudinal sib txawv kab kev tiv thaiv yog heev muaj nyob rau hauv niaj hnub fais fab kev lag luam. Qhov thib ob ntawm kev tiv thaiv kev sib txawv yog siv thaum siv cov kab hluav taws xob ua haujlwm sib luag.
Longitudinal sib txawv tiv thaiv kab thiab khoom siv
Txhawm rau siv cov kev tiv thaiv ntev ntev, nws yog ib qho tsim nyog yuav tsum nruab tib lub tshuab hloov tam sim no ntawm ob qho kawg. Lawv cov windings theem nrab yuav tsum tau txuas mus rau ib leeg nyob rau hauv series nrog kev pab los ntawm cov xov hluav taws xob ntxiv uas yuav tsum tau txuas nrog tam sim no relays. Ntxiv mus, cov tam sim no relays yuav tsum tau txuas mus rau lub thib ob windings nyob rau hauv parallel. Nyob rau hauv ib txwm muaj xwm txheej, raws li zoo raws li nyob rau hauv lub xub ntiag ntawm ib tug sab nraud luv luv Circuit Court, tib lub tam sim no yuav ntws nyob rau hauv ob qho tib si thawj windings ntawm lub transformers, uas yuav sib npaug zos rau theem thiab nyob rau hauv loj. Ib tug me ntsis tus nqi yuav ntws los ntawm electromagnetic tam sim no winding ntawm lub relay. Koj tuaj yeem suav nws siv tus qauv yooj yim:
Ir=I1-I2.
Xav tias tam sim no dependences ntawm transformers yuav tag nrho match. Yog li ntawd, qhov sib txawv ntawm cov lus hais saum toj no hauv cov nqi tam sim no yog ze rau lossis sib npaug rau xoom. Hauv lwm lo lus, Ir=0 thiab kev tiv thaiv tsis ua haujlwm rau lub sijhawm no. Cov kab txuas txuas txuas txuas txuas ntxiv ntawm cov khoom siv hluav taws xob hloov pauv tam sim no.
Scheme of longitudinal type differential protection
Qhov kev tiv thaiv kev sib txawv no tso cai rau koj kom tau txais cov txiaj ntsig sib npaug ntawm cov tam sim no uas ntws los ntawm lub voj voog thib ob ntawm transformers. Raws li qhov no, peb tuaj yeem txiav txim siab tias qhov kev tiv thaiv no tau muab npe vim yog lub hauv paus ntsiab lus ntawm kev ua haujlwm. Nyob rau hauv rooj plaub no, thaj chaw uas nyob ncaj qha nruab nrab ntawm cov transformers tam sim no poob rau hauv qhov chaw tiv thaiv. Nyob rau hauv cov kev tshwm sim uas muaj ib tug luv luv Circuit Court, nyob rau hauv lub tiv thaiv cheeb tsam, thaum powered los ntawm ib sab ntawm lub transformer, tam sim no I 1ntws los ntawm winding ntawm lub electromagnetic relay. Nws raug xa mus rau qhov thib ob Circuit Court ntawm lub transformer, uas yog ntsia rau sab nraud ntawm txoj kab. Nws yog ib qho tsim nyog yuav tsum tau them sai sai rau qhov tseeb tias muaj kev tiv thaiv siab heev nyob rau hauv qhov thib ob winding. Yog li ntawd, yuav luag tsis muaj tam sim no ntws los ntawm nws. Raws li txoj cai no, kev tiv thaiv kev sib txawv ntawm cov log tsheb, cov tshuab hluav taws xob, transformers ua haujlwm. Nyob rau hauv qhov kev tshwm sim uas I1 hloov tawm kom sib npaug lossis ntau dua Ir, kev tiv thaiv pib ua haujlwm, qhib kev tiv tauj pab pawg ntawm cov keyboards.
luv luv thiab tiv thaiv Circuit Court
Thaum muaj qhov luv luv hauv thaj chaw tiv thaiv, ob qho tib sisab, ib tug tam sim no ntws los ntawm electromagnetic relay, sib npaug rau cov sum ntawm cov tam sim no ntawm txhua winding. Hauv qhov no, kev tiv thaiv kuj tseem qhib los ntawm kev qhib cov kev sib cuag ntawm cov keyboards. Tag nrho cov piv txwv saum toj no xav tias tag nrho cov kev ntsuas ntawm cov transformers yog tib yam. Yog li ntawd, kuvr=0. Tab sis cov no yog cov zoo tagnrho tej yam kev mob, nyob rau hauv kev muaj tiag, vim me me sib txawv nyob rau hauv kev ua tau zoo ntawm magnetic systems ntawm cov thawj tam sim no, cov khoom siv hluav taws xob txawv ntawm ib leeg, txawm tias tib hom. Yog hais tias muaj qhov sib txawv ntawm cov yam ntxwv ntawm cov transformers tam sim no (thaum sib txawv-theem kev tiv thaiv ntawm cov qauv), ces cov tam sim no ntawm lub thib ob circuits yuav txawv, txawm tias lub hauv paus sawv daws yuav kiag li tib yam. Tam sim no peb yuav tsum xav txog yuav ua li cas qhov sib txawv tiv thaiv Circuit Court ua haujlwm nyob rau hauv cov xwm txheej ntawm ib qho luv luv Circuit Court sab nraud ntawm lub hwj chim kab.
Sab nraud luv luv
Nyob rau hauv lub xub ntiag ntawm sab nraud luv luv Circuit Court, qhov tsis sib npaug tam sim no yuav ntws los ntawm qhov sib txawv tiv thaiv electromagnetic relay. Nws tus nqi ncaj qha nyob ntawm seb qhov tam sim no dhau los ntawm lub hauv paus Circuit Court ntawm transformer. Nyob rau hauv ib txwm load hom, nws tus nqi yog me me, tab sis nyob rau hauv lub xub ntiag ntawm ib tug sab nraud luv luv Circuit Court, nws pib nce. Nws tus nqi kuj nyob ntawm lub sijhawm tom qab pib qhov txhaum. Ntxiv mus, nws yuav tsum ncav cuag nws tus nqi siab tshaj plaws hauv thawj ob peb lub sijhawm tom qab pib kaw. Nws yog lub sijhawm no uas tag nrho kuv luv Circuit Court ntws los ntawm cov thawj circuits ntawm transformers.
Nws tseem tsim nyog sau cia tias thaum xub thawj kuv luv Circuit Court muaj ob hom tam sim no - ncaj qha thiab hloov pauv. Lawv kuj hu uaaperiodic thiab periodic Cheebtsam. Cov cuab yeej tiv thaiv kev sib txawv yog xws li tias qhov muaj cov khoom siv aperiodic nyob rau hauv tam sim no yuav tsum ib txwm ua rau ntau dhau saturation ntawm transformer magnetic system. Yog li ntawd, lub unbalance tej zaum yuav sib txawv nce sharply. Raws li qhov luv luv Circuit Court tam sim no pib txo, qhov tsis sib npaug ntawm qhov system kuj txo. Raws li lub hauv paus ntsiab lus no, kev tiv thaiv sib txawv ntawm lub transformer yog ua tiav.
Kev nkag siab ntawm cov qauv tiv thaiv
Txhua yam kev tiv thaiv kev sib txawv yog ua tau sai. Thiab lawv tsis ua hauj lwm nyob rau hauv lub xub ntiag ntawm sab nraud luv luv circuits, yog li ntawd nws yog tsim nyog los xaiv electromagnetic relays, coj mus rau hauv tus account lub siab tshaj plaws tau unbalance tam sim no nyob rau hauv lub system nyob rau hauv lub xub ntiag ntawm ib tug luv luv Circuit Court. Nws yog ib qho tsim nyog yuav tsum tau them sai sai rau qhov tseeb tias hom kev tiv thaiv no muaj qhov tsis tshua muaj rhiab heev. Txhawm rau nce nws, koj yuav tsum ua raws li ntau yam kev mob. Ua ntej, nws yuav tsum tau siv tam sim no transformers uas tsis saturate lub magnetic circuits thaum lub sij hawm tam sim no ntws los ntawm lub hauv paus Circuit Court (tsis hais nws tus nqi). Qhov thib ob, nws yog ntshaw kom siv cov khoom siv hluav taws xob ceev ceev. Lawv yuav tsum tau txuas mus rau qhov thib ob windings ntawm lub ntsiab kom tiv thaiv. Ib qho hluav taws xob relay txuas nrog lub tshuab hluav taws xob nrawm nrawm (tam sim no kev tiv thaiv kev sib txawv yuav ua tau raws li qhov ua tau) nyob rau hauv parallel nrog nws qhov thib ob winding. Qhov no yog li cas lub tshuab hluav taws xob lossis qhov sib txawv ntawm kev tiv thaiv transformer ua haujlwm.
Nyob sensitivity
Xav tias muaj qhov luv luv sab nraud tau tshwm sim. Nyob rau hauv cov ntaub ntawv no, ib tug tej yam tam sim no ntws los ntawm lub hauv paus circuits ntawm kev tiv thaiv transformers, muaj xws li aperiodic thiab periodic Cheebtsam. Tib yam "cov khoom" muaj nyob rau hauv qhov tsis sib npaug tam sim no uas ntws los ntawm cov thawj winding ntawm lub nrawm-saturating transformer. Nyob rau hauv cov ntaub ntawv no, lub aperiodic feem ntawm tam sim no ho saturates lub core. Yog li ntawd, kev hloov pauv ntawm qhov tam sim no mus rau hauv lub voj voog thib ob tsis tshwm sim. Nrog rau attenuation ntawm lub aperiodic tivthaiv, ib tug tseem ceeb txo nyob rau hauv lub saturation ntawm lub magnetic Circuit Court tshwm sim, thiab maj mam ib tug tej yam tam sim no tus nqi pib tshwm nyob rau hauv lub thib ob Circuit Court. Tab sis qhov siab tshaj plaws ntawm qhov tsis sib npaug tam sim no yuav tsawg dua li qhov tsis muaj qhov hloov pauv sai. Yog li ntawd, koj tuaj yeem ua kom qhov rhiab heev los ntawm kev teeb tsa kev tiv thaiv tam sim no tus nqi tsawg dua lossis sib npaug rau qhov siab tshaj plaws ntawm qhov tsis sib xws.
qhov zoo ntawm kev tiv thaiv sib txawv
Thaum thawj lub sijhawm, lub tshuab hluav taws xob sib nqus yog saturated heev, kev hloov pauv tsis tshwm sim. Tab sis tom qab lub aperiodic tivthaiv decays, lub periodic ib feem pib hloov nyob rau hauv lub thib ob circuits. Nws yog tsim nyog them sai sai rau qhov tseeb tias nws tseem ceeb heev. Yog li ntawd, lub electromagnetic relay ua haujlwm thiab hloov tawm qhov kev tiv thaiv Circuit Court. Ib theem qis heev ntawm kev hloov pauv rau thawj zaug kwv yees li ib thiab ib nrab ntawm lub sijhawm qeeb qeeb ntawm qhov kev txiav txim ntawm kev tiv thaiv Circuit Court. Tab sis qhov no tsis ua lub luag haujlwm loj hauv kev tsim kho cov tswv yim tiv thaiv circuits.
Kev tiv thaiv qhov sib txawv ntawm qhov sib txawv tsis ua haujlwm thaum muaj kev puas tsuaj rau hluav taws xob hluav taws xob sab nraum qhov chaw tiv thaiv. Yog li ntawd, lub sijhawm ncua sijhawm thiab kev xaiv tsis tas yuav tsum tau ua. Lub sij hawm tiv thaiv teb yog los ntawm 0.05 mus rau 0.1 vib nas this. Qhov no yog ib qho txiaj ntsig loj ntawm hom kev tiv thaiv kev sib txawv. Tab sis muaj lwm qhov zoo dua - qib siab ntawm rhiab heev, tshwj xeeb tshaj yog thaum siv lub tshuab hloov pauv sai. Ntawm qhov zoo me me, nws tsim nyog sau cia xws li kev yooj yim thiab kev ntseeg siab heev.
Neegative properties
Tab sis ob qho tib si longitudinal thiab transverse sib txawv tiv thaiv muaj qhov tsis zoo. Piv txwv li, nws tsis tuaj yeem tiv thaiv hluav taws xob hluav taws xob thaum raug hluav taws xob luv luv los ntawm sab nraud. Tsis tas li ntawd, nws tsis tuaj yeem qhib hluav taws xob hluav taws xob thaum raug lub zog dhau.
Hmoov tsis zoo, kev tiv thaiv tuaj yeem ua haujlwm yog tias lub koom haum pabcuam raug puas tsuaj, uas txuas nrog cov winding thib ob. Tab sis tag nrho cov txiaj ntsig ntawm kev tiv thaiv kev sib txawv nrog kev ncig tam sim no cuam tshuam cov teeb meem me me no. Tab sis lawv muaj peev xwm tiv thaiv cov kab hluav taws xob ntawm qhov luv luv, tsis pub ntau tshaj ib mais.
Lawv feem ntau siv rau hauv kev siv ntawm kev tiv thaiv ntawm cov xov hlau, nrog kev pab los ntawm ntau yam khoom siv tsim nyog rau kev ua haujlwm ntawm cov chaw nres tsheb fais fab thiab cov tshuab hluav taws xob. Yog hais tias qhov ntev ntawm lub hwj chim kab yog loj heev, piv txwv li, nws yog ob peb kaum kilometers, kev tiv thaiv raws liQhov Circuit Court no nyuaj heev rau kev ua, txij li nws yog ib qho tsim nyog yuav tsum tau siv cov xov hlau uas muaj cov hlaws loj heev rau kev sib txuas cov hluav taws xob hluav taws xob thiab cov hluav taws xob thib ob ntawm cov hloov pauv.
Yog tias koj siv cov xaim hluav taws xob, ces qhov thauj khoom ntawm lub tshuab hloov tam sim no yuav loj dhau, nrog rau qhov tsis sib xws tam sim no. Tab sis hais txog qhov rhiab heev, nws hloov tawm mus rau qhov tsawg kawg nkaus.
Tsim kev tiv thaiv relays thiab thaj tsam ntawm circuits
Hauv cov kab hluav taws xob ntev heev, ib lub voj voog siv nyob rau hauv uas muaj kev tiv thaiv relay ntawm tus qauv tsim tshwj xeeb. Nrog nws, koj tuaj yeem muab cov qib ib txwm muaj kev nkag siab zoo, thiab siv cov qauv txuas txuas. Kev tiv thaiv kev sib txawv ua haujlwm los ntawm kev sib piv cov tam sim no hauv ob kab hauv theem thiab qhov loj.
Kev tiv thaiv kev kub ceev yog siv rau hauv cov kab hluav taws xob uas qhov hluav taws xob ntws hauv thaj tsam ntawm 3-35 txhiab volts. Qhov no muab kev tiv thaiv txhim khu kev qha tiv thaiv theem-rau-theem luv luv Circuit Court. Kev tiv thaiv kev sib txawv yog nqa tawm raws li ob-theem vim qhov tseeb tias lub zog hluav taws xob nrog cov kev khiav hauj lwm voltages saum toj no tsis yog grounded los ntawm nruab nrab. Txwv tsis pub, qhov nruab nrab txuas rau hauv av los ntawm txoj kev arc chute.
Pab xaim nyob rau hauv kev tsim ntawm kev tiv thaiv circuits
tam sim no transformers nyob rau hauv cov txheeb ze ze rau ib leeg. Yog li ntawd, cov hlua txuas txuas yog luv luv. Thaum siv cov kab me me rau ntawmtransformers yuav raug rau ib tug kuj tsawg load. Raws li rau qhov tsis sib npaug tam sim no, nws kuj yog me me. Tab sis qhov degree ntawm rhiab heev yog siab heev. Nyob rau hauv cov kev tshwm sim ntawm ib tug disconnection ntawm ib tug kab, qhov sib txawv kev tiv thaiv ua tam sim no, tsis muaj sij hawm ncua sij hawm thiab xaiv. Txhawm rau tiv thaiv kev ceeb toom tsis tseeb, kab pab cuam cuam tshuam lub voj voog.
Straverse circuit sib txawv tiv thaiv
Kev tiv thaiv kev hla yog dav siv hauv kev txhim kho cov kab ke ua haujlwm ua ke. Cov keyboards tau nruab rau ntawm ob sab ntawm txoj kab. Cov kab hauv qab yog tias cov kab no nyuaj heev los tiv thaiv nrog cov kab hluav taws xob yooj yim. Yog vim li cas yog hais tias nws yog tsis yooj yim sua kom ua tau ib tug ib txwm theem ntawm selectivity. Txhawm rau txhim kho kev xaiv, lub sijhawm ncua sijhawm yuav tsum tau ua tib zoo xaiv. Tab sis nyob rau hauv cov ntaub ntawv ntawm kev siv ib tug transversely qhia txawv kev tiv thaiv, lub sij hawm ncua tsis xav tau, lub selectivity yog heev. Nws muaj lub cev loj:
- Kev taw qhia lub zog. Ob-acting fais fab kev taw qhia relays feem ntau siv. Qee lub sij hawm ib khub ntawm kev tiv thaiv kev tiv thaiv ib leeg yog siv los ua haujlwm nrog cov lus qhia sib txawv.
- Pib - raws li txoj cai, kev kub ceev relays nrog qhov siab tshaj plaws tam sim no tau siv rau hauv nws lub luag haujlwm.
Tus tsim ntawm lub kaw lus yog xws li cov tam sim no transformers nrog ob peb windings txuas rau hauv ib lub voj voog tam sim no tau nruab rau ntawm cov kab. Tab sis tag nrho cov tam sim no windings yog switched nyob rau hauv series, tom qabdab tsi lawv txuas nrog kev pab ntawm cov xov hlau txuas ntxiv rau cov transformers tam sim no. Txhawm rau kom qhov sib txawv-theem tiv thaiv ua haujlwm, qhov hluav taws xob tau nkag mus rau lub relay siv cov busbars ntawm kev teeb tsa. Nws yog nyob ntawm lawv tias tag nrho cov khoom siv tau nruab. Yog tias koj saib ntawm lub voj voog rau kev hloov ntawm lub voj voog thib ob ntawm cov hloov pauv thiab cov kev tiv thaiv relay, peb tuaj yeem txiav txim siab vim li cas nws thiaj li hu ua "qhia yim". Tag nrho cov system yog ua nyob rau hauv ob pawg. Muaj ib txheej ntawm txhua qhov kawg ntawm kab, uas muab kev tiv thaiv sib txawv tam sim no rau cov kab hluav taws xob.
Ib-theem relay circuit
Voltage rau kev tiv thaiv relay yog nkag rau theem rov qab mus rau qhov xav tau los txiav ib txoj kab nrog kev puas tsuaj. Nyob rau hauv ib txwm ua haujlwm (xws li nyob rau hauv lub xub ntiag ntawm ib tug sab nraud luv luv Circuit Court), tsuas yog lub unbalance tam sim no ntws los ntawm lub relay windings. Txhawm rau kom tsis txhob muaj kev dag ntxias, nws yog ib qho tsim nyog uas qhov pib relays muaj qhov kev mus ncig tam sim no ntau dua li qhov tsis sib xws tam sim no. Xav txog txoj haujlwm tiv thaiv ob kab.
Thaum pib ntawm qhov luv luv, qee qhov tam sim no ntws hauv thaj chaw tiv thaiv ntawm kab thib ob. Nws yog tsim nyog them sai sai rau qhov tseeb tias:
- Pib relay qhib.
- Ntawm ib sab ntawm ib lub chaw nres tsheb, lub hwj chim kev taw qhia relay qhib lub Circuit Court breaker hu.
- Los ntawm sab ntawm lub chaw nres tsheb thib ob, txoj kab tseem raug txiav siv cov keyboards.
- Nyob rau hauv lub hwj chim kev taw qhia relay, lub zog torque yog qhov tsis zoo, yog li cov neeg tau qhib.
Nyob rau hauv windings ntawm thawj kab tiv thaiv relaycov kev taw qhia ntawm kev hloov pauv tam sim no (xws li thawj kab) thaum lub caij luv luv. Lub hwj chim taw qhia relay khaws cov pab pawg neeg nyob rau hauv lub xeev qhib. Lub Circuit Court breakers nyob rau sab ntawm ob lub substations qhib.
Tsuas yog cov kab sib txawv tiv thaiv tuaj yeem ua haujlwm tau zoo tsuas yog thaum ob txoj kab khiav hauv qhov sib npaug. Nyob rau hauv cov kev tshwm sim uas ib tug ntawm lawv raug muab tua, lub hauv paus ntsiab lus ntawm kev khiav hauj lwm ntawm qhov sib txawv tiv thaiv yog ua txhaum. Yog li ntawd, kev tiv thaiv ntxiv ua rau tsis muaj kev xaiv kaw ntawm kab thib ob thaum lub caij luv luv sab nraud. Nyob rau hauv rooj plaub no, nws dhau los ua ib qho kev taw qhia tam sim no, thiab nws tsis muaj sijhawm ncua sijhawm. Txhawm rau zam qhov no, kev tiv thaiv kev tiv thaiv kev tiv thaiv yuav raug kaw thaum lub sijhawm kev sib txuas ntawm ib txoj kab los ntawm kev rhuav tshem lub voj voog nrog kev sib tiv tauj.
Kev tiv thaiv ntxiv
Cov kev tawm mus ntawm qhov pib relays yuav tsum muaj ntau dua li qhov tsis sib haum xeeb tam sim no thaum lub caij luv luv sab nraud. Txhawm rau kom tsis txhob muaj qhov tsis zoo thaum ib qho ntawm cov kab raug txiav thiab qhov siab tshaj plaws thauj khoom tam sim no dhau los ntawm qhov seem, nws yog ib qho tsim nyog uas nws yuav tsum muaj ntau tshaj qhov tsis sib xws ntawm qhov sib txawv. Yog tias muaj hom kev tiv thaiv kev sib txawv ntawm txoj kab, yuav tsum tau muab qib ntxiv.
Lawv yuav tso cai rau ib kab los tiv thaiv thaum lub sijhawm sib npaug raug kaw. Feem ntau lawv yog siv rau kev tiv thaiv overcurrent thaum lub sij hawm ib tug luv luv Circuit Court (nyob rau hauv cov ntaub ntawv no qhov sib txawv tiv thaiv tsis hnov). Tsis tas li ntawd, kev tiv thaiv ntxivyog thaub qab rau qhov sib txawv (yog tias tom kawg ua tsis tiav).
Kev tiv thaiv kev taw qhia thiab tsis yog kev tiv thaiv tam sim no, kev txiav tawm, thiab lwm yam. feem ntau siv Kev tiv thaiv kev tiv thaiv kev sib txawv yog qhov yooj yim hauv kev tsim, txhim khu kev qha thiab tau siv dav hauv kev sib txuas hluav taws xob nrog qhov hluav taws xob ntawm 35 txhiab volts lossis ntau. Qhov no yog li cas kev tiv thaiv kev sib txawv ua haujlwm, nws txoj cai ntawm kev ua haujlwm yog qhov yooj yim heev, tab sis koj tseem yuav tsum paub tsawg kawg yog cov hauv paus ntawm hluav taws xob engineering txhawm rau nkag siab txhua qhov tsis sib xws.
