Phenomena ea Transformer Overvoltage le Mehato ea Tšireletso

Ka ntshetsopele e potlakileng ya dithekenoloji tse kang UHV le kgokelo ya keriti e ntjha ya eneji, di-transformer-sesebediswa sa mantlha bakeng sa phetiso ya motlakase le phetoho ya motlakase{1}}di bohlokwa ho tshepeheng ya digridi tsa motlakase le boleng ba phepelo ya motlakase. Leha ho le joalo, hangata li-transformer li tobana le tšokelo ea overvoltage nakong ea ts'ebetso: ha motlakase oa ts'ebetso o feta matla a mangata a amohelehang a sebetsang, ho etsahala ntho e fetang ea overvoltage. Ts'ebetso ena ea nakoana ea voltage anomaly ha e potlakise botsofali ba motlakase oa motlakase feela, empa hape e ka baka karohano ea insulation ka kotloloho, e lebisang ho hloleheng ha lisebelisoa kapa likotsi tsa grid. Tlhahlobo e phethahetseng ea mekhoa ea ho hlahisa overvoltage le ts'ebetsong ea mehato e lebisitsoeng ea tšireletso e bohlokoa ho netefatsa ts'ebetso e bolokehileng ea li-transformer.

 

 

 

 

Overvoltage tsamaisong ea matla e arotsoe ka mefuta e meraro ea mantlha ho latela nako le sesosa:overvoltage ya nakoana, ho fetoha ho feteletseng, lesepakapaka (atmospheric overvoltage), e 'ngoe le e 'ngoe e na le maemo a fapaneng a susumetsang le litšobotsi tsa kotsi.

 

 

 

 

 

 

(1) Switching Overvoltage: Transient Oscillation of Electromagnetic Energy

Ha u sa nke-moroalo oa ho fetola{{1}sefetoleli se tlase{2}}e leng boemo bo atileng haholo ho li-grid tsa motlakase-e le mohlala, karolo ea bobeli-ka matla a lehlakore e na le tšusumetso e fokolang haholo lehlakoreng la mantlha ha e fetoloa, kahoo e ka hlokomolohuoa. Maqhubu a mantlhamola-ho{1}}bokhoni ba fatše ()leinterturn capacitance ()e be li-parameter tsa bohlokoa. Ho tlohaho li-transformer tsa matla, phello ea bokhoni ba interturn e ka nolofalloa le ho feta bakeng sa tlhahlobo ea boleng.

Ha no-load transformer e tingoa, haeba che-load current e se{2}}zero, matla a khoheli a bolokiloeng ho "primary inductance" () le matla a motlakase a bolokiloeng ho () oscillate potolohong e bapileng e entsoeng kele. Oscillation ena, e nang le maqhubu a Hz a makholo a 'maloa ho isa ho likete tse' maloa 'me e tšoarella feela matla a -khafetsa, e fetolela matla a matla a khoheli ho ea ho matla a motlakase ha hona joale a fihla ho zero, ho phahamisa capacitor voltage ho ea holimo le ho etsa hore ho fetoloe matla a mangata. Maqhubu a phahameng a matsoelintsoeke le mothapo o tlase-ho-ho eketsa matla a lefatše ho eketsa bophahamo ba motlakase, e hlalosang hore na ke hobane'ng ha li-switching overvoltage hangata li sa fete makhetlo a 4.5 ho feta matla a rekiloeng.

 

(2) Atmospheric Overvoltage: Tlhaselo e Moepa ea Maqhubu a Lehalima

Maqhubu a lehalima a na le maqhubu a moepa (1–4 μs) le maqhubu a phahameng (ka holimo ho 100 kHz), a nang le moepa o fihlang ho 500 kV/μs. Motlakase ona o fetohang ka potlako o etsa hore ho be le phallo e kholo ho li-winding. Ha maqhubu a lehalima a namela ho li-transformerterminals, a sebetsa joalo ka matshwao a phahameng-a maqhubu a phahameng,{7}}e phahameng. Ka maqhubu a phahameng, matsoelintsoeke a inductive reactancee eketseha haholo, ha capacitive reactancee fokotseha haholo, kahoo e phalla haholo-holo ka har'a khefutso le mothapo{0}ho ea ho{1}matla a fatše.

Kaha sebaka sa -voltage winding se haufi le konokono, tsela ea eona e kholo-ho{2}}ground capacitance e batla e lekana le potoloho e khuts'oane, e etsa hore e theohe hantle. Kabo ea motlakase ea maqhubu a lehalima hammoho le matsoelintsoeke e khethoa ke karo-karolelano eaho: li-interturn capacitances tse haufi le theminale e kenang li nka nako e eketsehileng ka lebaka la ho tima, 'me li theha likhahla tse fetelletseng tsa motlakase moo thinyeho e 'maloa ea pele e ka bang le voltages makhetlo a makholo ho feta boleng bo reriloeng. Kabo ena ea motlakase e sa lekaneng ke sesosa sa mantlha sa ho putlama ha interturn insulation.

 

(3) Tekanyo e Feteletseng ea Nako ea Nako: Kokello ea Matla le Ho Oscillation Tlas'a Tsitsitseng-Litšitiso tsa Naha

Litšitiso tse fetelletseng tsa nakoana li hlaha ka lebaka la litšitiso tse - tse sa fetoheng, tse nang le maemo a mararo a tloaelehileng:

• Matla-a maqhubu a overvoltage: E bakoa ke-mohato o le mong o fosahetseng, ho hana thepa, kapa ho tjhaja mohala. Lisesetemeng tse theiloeng hantle, li-voltage tse phetseng hantle li nyolohela ho maemo a motlakase nakong ea{2}}mohato o le mong; Ho hana mojaro ka tšohanyetso ho eketsa lebelo la jenereithara le ho hlasimoloha ho sa fetoheng, ho phahamisa maqhubu a libese ho makhetlo a 1.5-1.8 ho boleng bo lekantsoeng ka metsotsoana e mengata.
• Resonance overvoltage: E etsahala ha inductance le capacitance li theha lipotoloho tse resontang ka lebaka la liphoso kapa ts'ebetso, e bakang phetoho ea motlakase-ea makenete. Ferromagnetic resonance, e tsamaisoang ke nonlinear transformer inductance, e baka maqhubu a maqhubu le amplitudes ea voltage ho fihlela makhetlo a 2-3 ho feta boleng bo lekantsoeng.
• Arc grounding overvoltage: E susumetsoa ke ho timela ha nako e itseng ha arc/ho rena ka nako e itseng-e nang le liphoso tsa mokhahlelo o le mong, e bakang ho sisinyeha ha motlakase. Arc extinction e lokolla matla a capacitive ho inductance, ha puso e eketsa pokello ea matla, e lebisang ho overvoltage makhetlo a 2.5-3 ho feta voltage e lekantsoeng.

 

 

 

 

 

Sistimi ea ts'ireletso e holileng e ntlafalitsoe ho sebetsana le likotsi le mekhoa ea ho phatloha ho feteletseng, ho kopanya tšireletso ea lehalima e otlolohileng ka ntle, ts'ireletso ea mapheo a ka hare, le mehato e khethehileng ea tlatsetso ho netefatsa polokeho ea transformer.

 

(2) Tšireletso ea Motšoaroa: Mekhoa ea Tšireletso ea Core

Li-grid arresters ke tsona tse ka sehloohongGapless metal oxide arresters (MOA)leli-valve tse nang le lekhalo{0}lithiba tsa mefuta, e nang le molao-motheo oa khetho e arolelanoang: motlakase o lekanyelitsoeng oa " arrester rated voltage" ha oa lokela ho ba ka tlaase ho matla a phahameng a nakoana sebakeng sa ho kenya, 'me motlakase o sa nke lehlakore-point arrester rated ha oa lokela ho ba ka tlaase ho matla a phahameng a motlakase a transformer.

• Haeba motlakase o rekiloeng o le tlase haholo: Lithako tse khaohileng li ka 'na tsa hlōleha ho tima li-arcs nakong ea-mohato o le mong, o bakang ho phatloha; Li-MOA li theoloa ke ho monya matla ho feteletseng.
• Haeba motlakase o lekantsoeng o le holimo haholo: matla a ho ntša motlakase le masala a eketseha, a fokotsa ts'ireletso ea ts'ireletso.

Li-valve tse nang le lekhalo-li sebelisa li-valve discs tse se nang moeli tse bonts'ang molumo o phahameng ka tlas'a maqhubu a maholo a lehalima (ho boloka motlakase o tlase) le motlakase o tlase ka matla a tloaelehileng (matla a fokotsang{1}}maqhubu a latela a hona joale). Gapless MOAs, leveraging zinc oxide valve discs, suppress late current ntle le likheo, tse fanang ka karabelo e potlakileng, resadual voltage, le matla a holimo{3}e leng se etsang hore e be tsona khetho ea mantlha bakeng sa ts'ireletso ea transfoma.

Ho latela GB311.1-1997Insulation Coordination for High-Voltage Transmission and Distribution Equipment, li-transformer tsa 6kV li na le matla a ho mamella voltage ea 60kV, le li-transformer tsa 10kV 75kV. Bakeng sa litsamaiso tsa 6kV, YH5WS-10/30 MOA e na le matla a setseng Ka tlase ho kapa ho lekana le 30kV, e fanang ka ntlha ea khokahano ea ho kenella.. Bakeng sa lisebelisoa tsa 10kV, YH5WS-17/50 MOA e fana ka lihlahisoa, ho finyella litlhoko tsa ts'ireletso ea ts'ireletso.Ka tloaelo E kholo ho feta kapa e lekana le 1.4 bakeng sa tšusumetso ea lehalima le E kholo ho feta kapa e lekana le 1.15 bakeng sa ho fetola maikutlo, ho nahanoa ka mofuta oa ho pata, kabo ea matla a mangata, le botsofali ba tikoloho.

 

 

 

 

(3) Insulation e Ntlafalitsoeng: Tšireletso ea Tlatsetso

Bakeng sa li-transformer tse mahareng le tse nyane (tse ka tlase ho kapa tse lekanang le 35kV), ho kenella ka matla ho matlafalitsoeng ke mokhoa oa bohlokoa oa tlatsetso: ho tiisa mapheo a phahameng-a matla le ho matlafatsa mohatsela ha li chenchana ho kena/terminal ho mamella likhahla tsa motlakase. Leha ho le joalo, mohatsela o motenya o sitisa ho qhalana ha mocheso 'me o fokotsa matla a ho phalla, e leng monyetla oa ho eketseha ha li-voltage -e leng se etsang hore sena se lokele feela bakeng sa maemo a tlase-ea motlakase, a theko{5}}a bobebe.

 

(4) Keketseho ea Boipheliso ba Matla: Phatlalatso ea Voltage e ntlafalitsoeng

Bophahamo bo phahameng ba interturne ntlafatsa ho tsamaisana ha motlakase: e kholoanyaneamanang lee fokotsa li-voltage gradients le kotsi ea overvoltage. Mekhoa e joalo ka li-winding le li-capacitor screens li sebelisoa, haholo-holo libakeng tse nang le lehalima{1}}tse tloaelehileng joalo ka liteishene tsa lithaba kapa liteishene tsa wind farm{2}}up station.

 

(5) Tšireletso e sa nke lehlakore-Point Overvoltage Protection

Bakeng sa liteishene tsa lehalima-libakeng tse tloaelehileng tse nang le mehloli e le 'ngoe ea matla,-ho na le ho kenella ha leqhubu la lehalima ka mekhahlelo e meraro, 'me ho hloka tšireletso e tsepameng{2}}ea ntlha. Tharollo ea mantlha keho se nke lehlakore{{0}point MOAs, e sireletsang khahlanong le lehalima le ho fetola li-overvoltages ka karabelo e potlakileng, matla a tlase a setseng, le matla a phahameng a hona joale. Liprofinseng tse tloaelehileng-tse kang Guangdong le Guangxi, litekanyetso tsa ho kenya{2}}point MOA li feta 90%. E entsoe ka litekanyetso tse phahameng tsa motlakase, e lula e tšepahala nakong ea ho fetoha ha maemo a manyane-'me e mamella matla a 1x-mohato oa maqhubu a motlakase nakong ea-mohato o le mong.

Bakeng sa li-fift shifts tse feteletseng-( overvoltage E kholo ho feta kapa e lekana le 2x power-frequency phase voltage), ho sebelisoa "arrester + horizontal rod gap" scheme: ba ts'oarang ba sebetsana le lehalima/switching overvoltage, ha likheo li fokotsa matla a phahameng{4}}frequency power{5}frequency arrest.

 

(6) Tšireletso e Khethehileng bakeng sa-Li-Winding Transformers

Tse tharo-li- winding transformer (tse phahameng, tse mahareng, tse tlase) li tobana le likotsi tsa ho felloa ke matla ha electrostatic induction overvoltage, haholo ha li- windings tse tlase- li butse. Maqhubu a tlalima karolong e phahameng-ea fetisoang ka lehlakoreng la motlakase ho ea ho tse tlase-maemelong a maqhubu a motlakase ka ho kopana ha electrostatic coupling le electromagnetic induction, 'me matla a tlase a fatše a phahamisa motlakase oa electrostatic, ho ts'osetsa. Lits'oants'o tse nang le-voltage windings tse tlase li thibela ka kotloloho matla a fetang a matla.

Ho feta moo, zero-motlakase oa tatelano ho tloha ho asymmetric faults kapa breaker malfunctions o fetela ho tlase-voltage windings ka capacitive coupling. Ho fokotsa sena, ho sebelisoa li-breaker tse phahameng-synchronism breaker, 'me li-capacitor tse 3 tsa Y{5}connected capacitor li kentsoe marokhong a libese tse tlase{6}}ho eketsa bokhoni ba ho ea fatše, ho monya matla a mangata le ho fokotsa bophahamo/boemo.

 

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Mehala e melelele ea {{0}voltage feeder feeder line' a ka hlaseloang habonolo ke lehalima. Ha e otloa, maqhubu a lehalima a susumetsaphetolo e fapaneng ya phetolomaqhubung a phahameng{{0}motlakase oa motlakase (makhetlo a 2-3) ka ho kenella ka motlakase, ho ts'osetsa. Low{{4}voltage side MOAs e hatella impulse flux -voltage windings e tlase, e thibela phetiso e fetang matla. Li-transformer tse nang le lihlopha tsa khokahanyo tsa Y/Zn11 ka tlhaho li hatella phetolo e feteletseng, li fana ka tšireletso e matlafalitsoeng ha li tsamaisana le{8}}li-voltage arrester.

 

(8) Mehato e meng e Khethehileng ea Tšireletso

Bakeng sa maemo a khethehileng a overvoltage, mehato ea tlatsetso e kenyelletsa:

1. Arc Suppression Coils: Ho hatella Arc Grounding Overvoltage

Ka li-coil tse sa thekeseleng kapa tse sa thekeseleng{0}}li-grounds tsa kabo ea li-coil, li-arc suppression coil li lefella capacitive current ka nako e le 'ngoe{1}}ea liphoso tsa mohato, ho fokotsa phoso le ho thibela ho busa ka linako tse ling. -likhoele tsa ho lokisa li latela{4}}liphetoho tsa nako ea 'nete, ho lekanyetsa ho overvoltage ea arc ho Tlas'a kapa ho lekana le 2x rated voltage.

2. Reactors: Limiting Switching le Power-Frequency Overvoltage

Series reactor: Thibela motlakase oa motlakase oa motlakase oa hona joale le oa ho fetola motlakase ka ho eketsa inductance ea potoloho ho fokotsa litekanyetso tsa hona joale tsa phetoho. Ka mohlala, li-reactors tse mahlakoreng a tlase-voltage ea li-transformer tse kholo li lekanyetsa inrush ea hona joale ho 2–3x rated current.

Shunt reactor: Nka matla a capacitive reactive lithapong tse telele tse telele- tsa motlakase, ho fokotsa matla a -khafetsa ho tsoa ho lithapo tsa ho tjhaja. Methapong ea 500kV, li-reactor tsa shunt li fokotsa matla a ho feta ho feta kapa a lekanang le matla a matla a 1.3x, a sireletsang li-transformer ka tsela e sa tobang.

3. Tlhōlisano ea Tsamaiso ea Grounding: Ho Fokotsa Phallo ea Motheo ea Motheo

Li-grid tse ntlafalitsoeng (mohlala, li-electrode tsa koporo-li-clad steel poles) li fokotsa khanyetso ea fatše ho Ka tlase ho kapa ho lekana le 0.5Ω, ho fokotsa ho phahama ho ka bang teng nakong ea lehalima le ho thibela litlhaselo. Libakeng tse tloaelehileng tsa lehalima-, "independent grounding + equipotential bonding" e fokotsa liphapano tse ka bang teng.

4. Varistors le Surge Protectors (SPD): Tlase-Tsireletso ea Matla a Felletseng

Li-Varistors (MOV) kapa li-SPD tse tlase-li-voltage feeder outlets li hatella lehalima le ho feto-fetoha ha matla, ho thibela phetolo e feteletseng. Lisebelisoa tsena li fana ka karabelo ea nanosecond le residual voltage e tlase, e loketseng bakeng sa ts'ireletso e tlase-ea motlakase oa phepelo ea motlakase.

 

 

 

 

 

 

Lethathamo lena le sebetsana le litlhoko tsa ts'ireletso ea overvoltage ho pholletsa le maemo a motlakase le maemo, ho latela mohopolo oa mantlha oaTšireletso e tobileng ea lehalima + core voltage limiting + khatello e khethehileng + tsamaiso ea tsamaiso. E hokahana le likarolo tsa moralo oa SCOTECH, mehato ea ts'ireletso e ts'oanang le litharollo tse ikhethileng bakeng sa ts'ebeliso e tobileng moralong oa projeke, boitlamo ba bareki le khetho ea sehlahisoa.

 

Boemo ba Kopo	Maemo a Ts'ebetso a mantlha	Mehato ea Tšireletso ea mantlha	SCOTECH e Ikamahanya le maemo
Outdoor Substation/Wind Farm Step-Up Stations ( E kholo ho feta kapa e lekana le 35kV, lehalima-libaka tse tloaelehileng/lithaba)	Kotsi e phahameng ea lehalima e tobileng; lehalima le kopantseng / switching overvoltage; ho se nke lehlakore{0}likotsi tse ka bang teng tsa ho fetoha	1. Tšireletso e tobileng ea lehalima ka ntle 2. Li-MOA tse se nang maqhubu a phahameng{1}ka lehlakoreng le leng 3. E sa nke lehlakore{1}ntlha MOA + rod gap parallel protection 4. Optimized winding capacitance kabo	1. Tloaeloli-winding/capacitor skriniliteisheneng tse kenang tsa li-transformer ho ntlafatsa kabo ea motlakase; 2. SCOTECH-ea tlhophiso ea ho se nke lehlakore{2}}lintlha tsa MOA tse tsamaellanang le motlakase oa mokhahlelo oa transfoma; 3. Likhokahano tsa ho kengoa tse thibelang bohole-ho fokotsa ho phahama ha motlakase ho tloha boholeng ba motlakase; 4. Litlhahiso tsa ntlafatso ea marang-rang, tse kopantsoeng le lithupa tsa lehalima/lithapo bakeng sa ho koahela lehalima ka ho otloloha.
Liteishene tsa Kabo ea Litoropo (10/6kV, libaka tsa mantlha tsa litoropo, phetiso ea mojaro khafetsa)	Ts'ebetso ea ho chencha khafetsa; phetoa khafetsa overvoltage; ha ho na lehalima le tobileng empa kotsi e bakoang ke lehalima; kotsi e tlase ea resonance	1. High{1}}valve e nang le lekhalo le lehlakoreng{2}}ea mofuta/MOA 2. Series reactor bakeng sa inrush hona joale moedi 3. Low{1}}voltage side surge protectors (SPD) 4. Insulation ea terminal e ntlafalitsoeng	1. Mohatla o motenya oa interturn/ground insulationho litheminale tse kenang tse kenang{{0}tse nang le maqhubu a phahameng a matla ho thibela mokhathala o feteletseng; 1 3. Optimized transformer excitation inductance ho fokotsa monyetla oa ho resonance tlas'a ho fetoha khafetsa
Li-Transformer tsa Kabo ea Mahaeng (10/6kV, lehalima le lehole{2}}libaka tse tjametseng, hangata{3}}liphato tsa mohato o le mong)	Kotsi e phahameng e tobileng / e bakoang ke lehalima; matla a maholo a arc grounding overvoltage; mehala e melelele ea mahaeng, kotsi e phahameng ea phetoho e fetang matla	1. 2. Ho se nke lehlakore{1}}ka li-coil tsa arc 3. Tšireletso e tlase-ka lehlakoreng la SPD la surge 4. Inverse phetolo overvoltage khatello	1. PhahamisaLi-transformer tsa lihlopha tsa Y/Zn11ho hatella ka tlhaho ho feto-fetoha ho feteletseng; 3 3. Optimized neutral -point insulation to the auto{2}}tuning arc suppression coil; 4
Industrial Plant inehetseng Transformers (10/35kV, -matsoho a mangata, phallo e phahameng ea thepa)	Multi{{0} winding electrostatic induction overvoltage; ho fetola overvoltage ho tloha ho fetola mojaro; kotsi-ea tatellano ea matla a khokahanyo; low{{2}voltage inverse transformation overvoltage	1. Batšoantšisi ba ikemetseng bakeng sa leqhubu le leng le le leng 2. Low-voltage side shunt capacitor bakeng sa ho monya overvoltage 3. Series reactor bakeng sa inrush / overvoltage moedi 4. Matlafatso ea insulation ea lera	1. Insulation e matlafalitsoeng e ikemetsengsebakeng se seng le se seng sa matsoelintsoeke: optimized capacitance distribution on high-mahlakoreng a feberu, a teteaneng a fatang fatše ka mahlakoreng a -tlase; 2) 3. Li-reactor tse tloahelehileng tse etselitsoeng ho laola maemo a feto-fetohang{1}}a bakoang ke inrush current; 4. Litafole tse tsamaellanang tsa khetho ea bahapi bakeng sa maemo a mangata-a maqhubu a motlakase
-Li-Transformer tsa Khale ea Khale (E kholo ho feta kapa e lekana le 110kV, likhoele tsa phetiso E kholo ho feta kapa e lekana le 50km)	Matla-maqhubu a fetelletseng a ho tjhaja mohala; phetoho e kholo ea overvoltage ho tloha ho feto-fetoha ha mohala; leqhubu la leqhubu la lehalima le hlabang	1. Li-MOA tsa{1}tse phahameng haholo mahlakoreng{2}a matla a phahameng 2. Linea{1}}li-side shunt reactor tsa capacitive reactive power absorption 3. Leqhubu la lehalima le hatellang moepa 4. Sehlopha se ntlafalitsoeng sa li-transformer insulation	1. Tloaelomatla a phahameng a mamella li-transformere ikamahantse le-moepa o molelele oa lehalima; 2. Optimized transformer excitation litšobotsi ho fokotsa resonance le melapo reactor; 3. Li-MOAs tse phahameng{{1}hajoale{2}}tse holimo{3}}mahlakoreng a phahameng, tse sebetsanang le{4}}frequency/switching overvoltage; 4. Lisebelisoa tsa leqhubu la leqhubu la lehalima liteisheneng tse kenang ho fokotsa moepa oa maqhubu
Liteishene tsa Compact Substations/Seteishene sa Transformer se seng se entsoe (10/6kV, libaka tsa literopo/paka, sebaka{2}}se haelloang)	Ha ho na tšireletso e tobileng ea lehalima e ikemetseng; ho kopanya lisebelisoa tse phahameng, libaka tse nyenyane tsa motlakase; lehalima le susumelitsoeng + ho feto-fetoha ha ka hare ho overvoltage	1. Li-MOA tse kopantsoeng ka hare ho khabinete 2. Varistor (MOV) tšireletso ea tlatsetso 3. E tlang mola surge khatello 4. Tšireletso ea bonding ea equipotential	1. Maemo a kopantsoeng a ho ts'oarabakeng sa zero-distance transformer-kopano ea mots'oari; 2. E hahiloe-ka tlase{2}}li-voltage side varistors ho hatella overvoltage ea kahare; 3. Equipotential bonding moralo ka hare ho lik'habote ho fokotsa fatše monyetla oa ho counterattack kotsi; 4. Sebopeho se ntlafetseng sa matsoele bakeng sa libaka tse kopanetsoeng, ho fokotsa ho se leka-lekane ha matla a motlakase.

 

Tlatsetso Notes

• Litharollo tsohle li tšehetsaKhokahano e kopaneng ea li-transformer tsa SCOTECH le likarolo tsa ts'ireletso, ho fokotsa khetho ea bobeli ea bareki le litšenyehelo tsa ho kenya.
• Bakeng sa maemo a feteletseng (mohlala, libaka tse matla tsa lialuma, bophahamo bo phahameng, tšilafalo e matla), likhetho tse ntlafalitsoeng joalo katse thibelang-pollution insulation coatings,{1}lits'oants'o tse phahameng tsa hona joale, le litheminale tse ikemetsenglia fumaneha.