Matatizo na Hatua za Upambanisho kwa Unganisho wa Kabeli wa 10kV SF₆ Gas-Insulated Common Tank Ring Main Unit (Ufugaji wa Ulaya)

Suluhisho na Hatari za Uhusiano wa Kabila 10kV SF₆ Gas-Insulated Common Tank Ring Main Unit (Aina ya Ulaya) na Msimbo wa Kamba​

Kwa kutumika kwa wingi vifaa vya msimbo wa kamba katika mitandao ya maeneo miji, 10kV SF₆ gas-insulated common tank Ring Main Units (RMUs) (Aina ya Ulaya) zinatumika sana kama vitambura vya mitandao kutokana na sifa zao za kuwa zenye insulation kamili, kukokotwa kamili, kutumika bila huduma, ukubwa mdogo, na uwezo wa kuinstalisha kwa urahisi. RMUs hizi za Aina ya Ulaya ni za kutosha kwa eneo la pwani ambalo lina mazingira ya maji mengi na kali, na inatoa uhakika wa kufanya kazi.

Matatizo yaliyotokea mara nyingi katika RMUs yanayoelezea kwamba yaliyotoka kutokana na matatizo kwenye mahusiano kati ya bushings za RMU na msimbo wa kamba wa 10kV. Hii ni hasa kwa RMUs za ndani na nje zinazohusiana na viwango vikubwa na msimbo wa kamba wa sekta kubwa. Waktu matatizo hutokea, inahitajika kutoa umeme kwa RMU nzima na kubadilisha, na kuhifadhiwa tena kujenga upya kwenye T-body connector. Hii huathiri usalama wa utambuzi wa umeme na kuongeza gharama za kiuchumi.

Uhusiano kati ya bushings za RMU na msimbo wa kamba wa 10kV ni sehemu muhimu ambayo inaweza kutoa matatizo. Maoni haya yanachambua matatizo hayo na yakusaidia kutoa suluhisho.

​1. Matatizo ya Common Tank RMUs na Uhusiano wa Kamba ya Tatu​

Sasa, 10kV SF₆ common tank RMUs (Aina ya Ulaya) na T-body connectors zao zinatumika sana kwa brand za Ulaya. Zinajengwa kwa ujumla kwa ajili ya kamba moja, ambayo zinaweza kufixiwa na kuiinstalisha rahisi, hazitosha torsion torque kwenye bushings, husaidia kufanya kitucho kwa kutosha kati ya terminal na bushing, na kuridhisha ukosefu wa matatizo ya joto. Ingawa, kuiinstalisha kamba tatu ni ngumu zaidi, na huwasilisha matatizo mengi ambayo hazitoke kwa kamba moja:

1. ​Sehemu ya kufixiwa ya kamba tatu ni outer sheath:​​ Vipengele vyenye phase vinaweza kufixiwa kwa kume. Hata baada ya kuunganishwa, uzito wao mwenyewe au nguvu za nje zinaweza kusafirisha torsion torque kwenye sehemu za bushings.
2. ​Ukakamilisha mfululizo wa phase unahitaji torsion:​​ Wakati wa kuiinstalisha kamba tatu, kufanya mfululizo wa phase mara nyingi hukuhitaji kutumia torsion kabla ya kufixiwa. Baada ya kuiinstalisha, stress ndani hupungukiwa kwa kutosha, kunaweka torsion ya kurudi kwenye bushings.
3. ​Urefu wa chumba cha kamba uliofikia:​​ Chumba cha kamba cha RMUs (lijengwa kwa ajili ya kamba moja) linapunguza urefu wa sekta ya kila core ya kamba.
4. ​Uwezo wa kubadilisha baada ya kufikia mwisho:​​ Mara tu lug iliokunzwa, urefu wa kuiinstalisha unafanikiwa. Na urefu wa sekta mtandaoni (kwa sababu ya mzunguko wa nchi) unaweza kuwa mgumu kupinduka, kusafirisha T-body connector kwenye nyanja inahitaji kutumia nguvu nyingi za kusafirisha, kusimamia, au kutumia mkono. Hii inaruhusu kugumuza bushings au kutofanya kitucho kwa kutosha.

​2. Suluhisho​

Kutokana na matatizo hayo, suluhisho yanaweza kutumiwa kuhusu RMU mwenyewe, T-body connectors, njia za kuiinstalisha, na misingi ya RMU.

​2.1 Ring Main Unit (RMU)​​

2.1.1 ​Ongeza Urefu wa Chumba cha Kamba Kwa Kutosha:​​
Chumba cha kamba cha SF₆ common tank RMU ni dogo (H: karibu 600mm, W: karibu 350mm). Hii inafaa kwa kamba moja lakini inafanya kuiinstalisha T-body connectors, hasa kwa kamba za sekta kubwa (240mm² au 300mm²), ngumu sana kwa kamba tatu. Trifurcating sleeve ya T-body connector pia inahitaji nyanja, akasema kuwa urefu wa core za kamba unaenda karibu 400mm. Core za sekta kubwa ni magumu, na pamoja na mikakati ya eneo, kufanya T-body connector kwa kutosha ni ngumu.

• ​Suluhisho:​​ Ingawa RMUs za common tank zinajengwa kwa kijamii, urefu wa kuiinstalisha unaweza kuongezeka kwa kutumia base ya extension. Kuongeza urefu wa chumba hadi karibu 800mm na kutahidi urefu wa vertical distance kati ya cable clamp na center point ya HV bushing ≥750mm kunaweza kutetea urefu wa core za kamba wa karibu 600mm. Hii inafanya kwa urahisi kuiinstalisha T-body connector. Msingi wa extension huo unaongeza urefu wa single-phase cores baada ya kamba tatu kugawanyika, kufanya kuiinstalisha kama kamba moja.
• ​Faida:​​ (1) Kuridhisha torsion torque kwenye bushings; (2) Ongeza tolerance ya kuiinstalisha, kuridhisha hitaji wa kutumia nguvu; kuridhisha hatari ya leakage ya gas; (3) Fanya kwa urahisi positioning ya lugs na stress cones.

2.1.2 ​Kumbuka Conductivity ya Bushing Wakati wa Kuchagua RMU:​​
RMUs za standard 630A mara nyingi zina bushings za bolt-type na outer copper tube diameter ya 25mm na threaded inner hole kwa M16 bolts (conductive area ~289.6mm²). Eneo la contact halisi linaweza kuwa chache zaidi kutokana na fit tolerances. Wakati stainless steel bolts zinatumika (kwa sababu ya soft copper), conduction linategemea tu kwa end contact. Ndani ya sealed insulation, heat dissipation ni duni. Ikiwa contact ya lug-to-bushing linaweza kuwa chache kwa viwango vikubwa (>400A), thermal faults zinatokea.

• ​Suluhisho:​​ Kwa RMUs zinazotumia 240mm² au 300mm² kamba zinazotumia viwango vikubwa (>400A), chagua models na bushings zinazorated 800A (outer copper tube Ø 32mm) ili kuridhisha hatari ya thermal fault.

2.1.3 ​Imara Monitoring ya Joto ya Bushing ya RMU:​​
Common tank RMUs zisizoweza kufunguliwa kwa ajili ya kutathmini. Standard IR thermography haiona temperature ya joints. Kutumia inspection ports kunaweza kuboresha IP rating.

• ​Suluhisho:​​
• Mstari wa kawaida: Kuthibitisha temperature ya panel ya mbele ya chumba cha kamba kwa kinyume kwa mikono ili kudhibiti overheat ya T-body.
• Units muhimu: Kutoa umeme mara kwa mara baada ya initial high-current operation ili kutathmini connections kwa alama za overheat.
• ​Mstari mzuri (Teknolojia):​​ Instala sensors za joto moja kwa moja kwenye bushings za RMU au T-body connectors kwa monitoring ya joto ya real-time.

​2.2 Cable T-Body Connector​

2.2.1 ​Thibitisha Ubora wa Conductive Components:​​
Kubadilisha kwa stainless steel bolts kunaweza kufanya conduction kunategemea tu kwa end contact, kuboresha hitaji wa structure/material quality ya lug. Matatizo mawili yanayopatikana:

Eneo la contact la lug ni chache/safi la hole ni chache → urefu wa contact unaondoka.

Ubora wa material ya lug ni chache, plating ni isiyosawa.

Mismatch kati ya taper ya lug hole na double-ended bolt → lug haitegemi kushikana na bushing vizuri → conduction kunategemea tu kwa bolt.

Copper washer ni chache/dogomdogo → haitegemi parallel contact kati ya lug na bushing.

Yote huathiri current capacity na hatari ya thermal fault.

• ​Suluhisho:​​ Thibitisha conductive components za T-body connector kwa kutosha:
• Width ya surface ya lug: 25mm au 32mm (match bushing conductive area).
• Material ya lug: T2 copper (>99.9% Cu, electrolytic, molded, annealed). Tin au silver plating.
• Washer: Surface kubwa, ≥3mm thick ili kutegemi pressure contact nzuri.

2.2.2 ​Chagua Soft-Material T-Body Connectors ili Kurekebisha Installation:​​
EPDM au rigid plastic/rubber T-bodies ni magumu/brittle, ngumu kubadilisha wakati wa kuiinstalisha (hasa kwa cores kubwa/stress cones/insulation), na ngumu kuthibitisha positioning. Elasticity chache/radial force chache kunaweza kusababisha separation ya interface na tracking ya muda mrefu.

• ​Suluhisho:​​ Chagua Silicone Rubber T-body connectors kwa common tank RMUs. Faida: Soft, elastic → rahisi kubadilisha positioning; Radial force nzuri na uniformity → sealing nzuri, kuridhisha tracking; Mechanical strength suficiente kwa chambers za RMU.

​2.3 Site Installation Practices​

2.3.1 ​Secure Cable Entry Point:​​
Securu kamba tatu inayofika kwenye RMU chini kwa chini ya HV bushings kutumia cable clamp. Ridhisha tilting au unsupported cable entry. Kamba zisizosecuru zinaweza kusafirisha torsion/pulling forces, inaweza kubovu integrity ya bushing/seal → SF₆ leakage, bushing cracks, HV faults.

• Position cores vertically na symmetrically; ridhisha twisting.
• Weka branch glove na cable clamp chini sauti (≥750mm vertical distance kwenye bushings).
• ​Site Process:​​ Baada ya kupiga kamba chenji kwenye foundation kwenye chumba, gonga off sehemu ya kamba yenye damage. Thibitisha mfululizo wa phase. Align angle ya kamba entry ili cores ziwe straight kwenye bushings. Ikiwa angle ni ngumu, rudia kamba chenji kwenye trench/pit, sarisha angle, basi re-insert na securu firmly. Double-fixing:​​ Ingawa inaweza, ongeza point ya pili ya kufixiwa (mfano, fixing beam kwenye cable pit chini) ili kusecura outer sheath zaidi.

2.3.2 ​Cable Phase Separation and Preparation:​​

1. Fix cable branch glove kutumia clamp bafore kutrim core lengths.
2. Align B phase kwenye B bushing.
3. Slightly bend A/C phases outward at the root before vertically aligning them with their bushings.
4. Place termination bolt into bushing, hang lug loosely on it.
5. Cut core ends to exact required length after verifying alignment.

• ​Crucial:​​ Fix cable before final trimming.​​ Failure to do so results in inconsistent core lengths → bushing stress and poor contact.
• ​Peeling/Cleaning Process:​​
• Follow T-body manufacturer's peeling dimensions exactly.
• Avoid damaging inner layers while peeling outer layers.
• Absolutely prevent longitudinal scratches on core insulation → prevents internal tracking.
• Use manufacturer-supplied cleaning paper. Avoid other solvents like industrial alcohol.
• Use polyfluoroether-based lubricant (compatible with silicone rubber). Avoid silicone grease → mutual dissolution → interface drying → tracking risk.

2.3.3 Stress Cone Installation:​​

• Ensure stress cone matches cable size → correct interference fit. Too tight: hard install, risk splitting. Too loose: poor sealing, risk surface discharge.
• Position strictly per T-body manufacturer’s instructions (positions relative to insulation and cable core affect stress control/sealing). Minimal tolerance.
• Position stress cone on the vertical section of the cable if possible → ensures best seal.
• Prevent sharp objects from scratching silicone rubber surfaces.
• Apply uniform coating of compatible lubricant on interference fit surfaces.

2.3.4 Ensure Sufficient Conductor Contact Area:​​
Conductor connection inside the insulation sleeve is invisible/hard to check. Must ensure:

• Lug surface is parallel to bushing conductive surface → minimized stress on bushing.
• Excellent contact to prevent heating.
• Crimping:​​ Crimp lug to core per procedure. Ensure lug face orientation is parallel to bushing plane. After crimp dies close fully, hold pressure for 10-15 seconds. Deburr surfaces. Clean lug and core insulation.
• Connection:​​ Place lug onto bolt, push T-body into bushing → ensure parallel lug-to-bushing contact before tightening.

2.3.5 Ensure Reliable Grounding:​​
Shielded T-body connectors must be properly earthed using dedicated grounding rings/wires connected to the RMU ground grid. Failure risks: Static charge build-up on surface → shock hazard.

Surface discharge to nearby ground → material electrical erosion.

​2.4 Requirements for RMU Civil Foundation​

• RMU base typically 300-500mm above ground level.
• Cable pit depth below base should be ≥800mm; strive for 1000mm if site permits.
• Purpose:​​ Provides adequate bending radius for cable entry (especially large sections), allowing near-vertical entry → reduces stress on cable/connection.