Teknolojia na Uchunguzi wa Vifaa vya Kufunga Mduara vya Kiwango cha Kutoka Chini kwa Kivuli Chandarua

1 Utangulizi​
Mbinu za msingi za kutengeneza mzunguko wa umeme wa kiwango cha 10kV (RMUs) zinazotumika ni gas, solid na air.
• Uzingatiliaji wa gas mara nyingi hutumia SF₆ kama chombo cha kutengeneza. Hata hivyo, moja ya molekuli za SF₆ ina athari ya greenhouse 25,000 mara zaidi kuliko moja ya CO₂, na SF₆ inapaa katika asili kwa miaka 3,400, ikisababisha hatari kubwa za mazingira. RMUs za kiwango cha ukoo ni zinazopatikana sana, kufanya kupunguza SF₆ kuwa ngumu na gharama ikiwa itakusudi kutathmini.
• Uzingatiliaji wa air unahitaji uzito mkubwa wa ukingo, kutosha kurekebisha upungufu wa ukubwa wa switchgear.

Kutokana na maendeleo yasiyofikirika ya mitandao ya umeme wa miji, matumizi kama vile majengo ya magereza na usafiri wa tume, yanahitaji RMU zinazofanikiwa zaidi - zinazohitaji eneo la chini, uhakika/wastani, huduma ndogo, na utambuzi wa mazingira. RMUs za solid-insulated za kiwango cha ukoo zinaenda kwa mwenendo mpya.

RMUs za 10kV za solid-insulated zinatumia teknolojia ya solid insulation badala ya SF₆ gas. Ukubwa wao ni tu 30% wa vifaa vilivyovunjwa kwa air, wanatoa ufanisi wa insulation zaidi na wanapokea uaminifu kutoka kwa watalii na watumiaji.

​2 Vifaa vya Insulation na Mfano​
Tathmini ya gharama inashuhudia kuwa muundo wa insulation unaishi zaidi ya 40% ya gharama jumla ya RMUs za solid-insulated. Kuchagua vifaa vya insulation vyenye ubora, kutengeneza muundo wa insulation mzuri, na kutathmini njia zinazozingatia ni muhimu kwa thamani ya RMU.

Tangu uundishwe kwa mara ya kwanza mwaka 1930, epoxy resin imekuwa inachanika kwa kutumia viunganisho. Iliukwa kwa nguvu ya dielectric, nguvu ya mechanical, upungufu wa ukubwa wakati wa curing, na rahisi ya kutumika. Kwa hiyo, tunatumia kama vifaa vya insulation kuu kwa RMUs za kiwango cha ukoo, kunawezesha kwa hardeners, toughening agents, plasticizers, fillers, na pigments ili kutengeneza epoxy resin yenye ubora. Maendeleo ya ukimbia, thermal expansion, na thermal conductivity zinaweza kutoa flame retardancy na ufanisi wa insulation bora kwa wakati mrefu na overvoltages.

Muundo wa insulation wa RMU wa kawaida unahifadhi electric fields zisizosawa. Kuongeza clearances tu haifai kuboresha nguvu ya insulation katika fields hizo. Tunaboresha muundo wa field ili kuongeza usawa. Nguvu ya electrical ya epoxy resin ina anga 22–28 kV/mm, inamaanisha kuwa tu milimita chache zinahitajika kati ya phases katika muundo ulio boreshwa, kusababisha kupunguza ukubwa la bidhaa.

​3 Mfano wa Utengenezaji wa RMUs za Solid-Insulated za Kiwango cha Ukuu​
Vacuum interrupters, disconnectors, grounding switches, na vitu vyote vya kusambaza umeme vinavyoingia katika molds. Epoxy resin yenye ubora inayotengenezwa kwa kutumia teknolojia ya automated pressure gelation. Arc-extinguishing medium ni vacuum, na insulation inatolewa na epoxy resin.

Muundo wa cabinet unatumia mfano wa modular kwa urahisi wa kutengeneza kwa kila kitu. Kila bay ya RMU inavunjika na metal partitions ili kutengeneza fault arcs kwenye modules tofauti. Integrated busbar connectors na integrated contact connectors zinatumika. Main busbar ina segmented, enclosed insulated busbars zinazoungwa na telescopic integrated connectors kwa urahisi wa kutengeneza na kutathmini. Cabinet door ina muundo wa internal arc-proof na inawezesha closing, opening, na grounding (three-position operation) wakati mlango umefungwa. Hali ya switch inaweza kuonekana kwa kutumia windows za kutazama, kuhakikisha utaratibu mzuri na uhakika.

​4 Faides na Tathmini ya Type Testing za RMUs za Solid-Insulated za Kiwango cha Ukuu​
​4.1 Faides Muhimu:​​
(1) Hutumia epoxy resin yenye ubora kwa insulation reliable na partial discharge ndogo.
(2) Muundo mzima wa insulation na sealed ambaye hakuna sehemu za umeme zenye kuonekana. Haupaswi na dust au contaminants. Inapatikana kwa mazingira mbalimbali (temperature juu/chini, altitude juu, mahali pa explosion/contamination). Hakuna shida kama SF₆ gas pressure fluctuations wakati wa temperature juu au liquefaction wakati wa baridi sana. Ina faides kamili katika maeneo ya coastline ya high-salt-fog.
(3) Hauna SF₆ na hazina gases hasara - ni bidhaa ya kijani. Muundo wa leak-proof huondokana na huduma ya kila wakati. Uhakika wa explosion unaboreshwa kwa mahali pa hatari. Muundo mzima wa three-phase unapunguza faults za phase-to-phase, kuhakikisha safety na reliability.
(4) Huuza tu 30% ya space ya air-insulated RMUs - ni suluhisho la ultra-compact.

​4.2 Tathmini ya Type Testing​
Kulingana na faides hizi, tathmini kamili ya type testing ilifanyika, ikiwa ni:

• Mipimo ya insulation (42kV/48kV withstand voltage)
• Measurement ya partial discharge (≤ 5pC)
• Mipimo ya temperature juu/chini (+80°C / -45°C)
• Mipimo ya condensation (Class II pollution)
• Mipimo ya internal arc (0.5s)
  Matokeo ya mipimo yalihakikisha kuwa bidhaa imekufanikiwa kwa kutosha, kuthibitisha faides zote zilizoelezwa.

Mipimo mingine ya national standards zilitathmini:

• Mipimo ya temperature rise
• Mipimo ya resistance ya main circuit
• Mipimo ya rated peak withstand current na short-time withstand current
• Mipimo ya rated short-circuit making capacity
• Mipimo ya rated short-circuit breaking capacity
• Mipimo ya electrical endurance
• Mipimo ya mechanical
• Mipimo ya earth-fault (phase-to-phase)
• Mipimo ya rated active load current switching
• Mipimo ya rated capacitive current switching
  Matokeo yote yanafanana na national standards.

​5 Sifa Muhimu za Kutengeneza​
① Wakati wa kuleta concrete, kuleta beams na columns kwanza, basi slabs. Kuleta layer-by-layer kulingana na direction ya formwork tubes (note: translation adjusted for clearer technical meaning), kuleta concrete kwenye CBM self-stabilizing formwork kabla ya kuhamisha chini. Kuleta layer ya kwanza ya concrete hadi height ya nusu ya formwork, kushindwa symmetrically kwa pande zote. Tumia vibrators ≤35mm diameter (maranyonyo 30mm) kwa penetration na vibration uniform. Angalia kwamba hakuna gaps, under-vibration, au contact na formwork. Spacing ≤25cm, duration ≤3s per point. Baada ya kukuthibitisha kuwa imetengenezwa vizuri, kushinda surface layer tena kwa screed vibrator kabla ya initial setting, basi kufanya leveling na compaction kwa kutumia wood float.
② Water/electricity conduits yanapaswa kusafiri kwenye ribs between CBM self-stabilizing formwork units. Ikiwa itakusudi kupita through unit, tumia size ndogo ya formwork. Wakati wa kutengeneza formwork na kuleta concrete, tunda working platforms. Weka supports za concrete pump pipe kwenye platforms hizi. Watu wasipoingia direct kwenye formwork, na materials wasipowekwa direct kwenye formwork.

​6 Performance ya Engineering ya CBM Self-Stabilizing Formwork​
① Increased Clear Height
Ingawa kwa beam-slab systems za kawaida, project mbili zinazotumia hollow-core slabs zimepunguza thickness ya structure kwa floor kwa 30–50cm, kuboresha clear height. CBM self-stabilizing formwork ni nzuri kwa structures za large-span, heavy-load industrial/public. Inaweza kubalance force distribution na kuboleza placement ya partition walls.
② Reduced Costs
System ya CBM hollow-core slab ina grid-like orthogonal "I"-shaped lattice na hidden closely-spaced ribs, inaweza kubalance transfer ya force. Ingawa kwa project mbili, ilipunguza reinforcement steel kwa 27%, volume ya concrete kwa 29%, na area ya formwork kwa 46% kwa RC frame structures za kawaida. Gharama za construction zimepungua kwa 26.3%.
③ Simplified Construction
CBM formwork ina nguvu, weight ndogo, impact resistance, na integrated support frames kwa urahisi wa kutengeneza. Na hidden beams, bottom ya slab inaweza kuwa flat, kuboresha operations za formwork/shoring.
④ Lighter Weight, Optimized Performance
CBM hollow-core slabs zimepunguza structural self-weight kwa 27.6% kulingana na calculations, kuboresha design ya beams, slabs, columns, na foundations.

​7 Discussion on CBM Formwork Construction Issues​
① Ensuring lower flange concrete compaction is challenging. Leakage in CBM hollow-core slabs is difficult to remedy.
Unlike conventional slabs where concrete is placed directly on a single surface, CBM slabs have upper and lower flanges. Achieving compaction in the lower flange requires meticulous vibration using small-diameter vibrators and external vibrators. After this, the hidden beams and top slab are poured, demanding great care and dedicated QC oversight.
Crack frequency in CBM slabs is comparable to or slightly lower than conventional slabs. However, leaks occurred in the basement roofs and roof slabs of both projects. Identifying the cause is difficult—potential sources include cracks in the upper flange, water seepage through adjacent formwork, or conduits within the ribs. Per leak, repair effort/cost is 5–8 times higher than for conventional slabs.
② Construction Joints & Expansion Strips Require Detailed Design
Structural expansion joint locations are typically specified by design codes. However, the dual-flange nature of CBM slabs complicates pouring if a joint abuts a formwork unit: ensuring bond between new/old concrete in the lower flange and containing grout is difficult. On-site, joint locations should be adjusted based on formwork layout to ensure joints fall within ribs between formwork units. Resizing adjacent units may be necessary.
With CBM slabs typically covering large areas, designers often overlook construction joint placement. To ensure proper bonding within the initial setting time, the site team must determine joint locations considering pour width limits and resource capabilities. Joints must meet code requirements and be placed within ribs.
③ Difficult Mitigation of Formwork Buoyancy
If formwork buoyancy occurs during pouring, the existing countermeasures (removing top reinforcement, clearing concrete, re-fixing formwork) are impractical and often ineffective. Currently, the only solution is breaking/removing the floated unit, placing additional reinforcement, and pouring solid concrete there. Rigorous onsite monitoring of formwork securing and anti-buoyancy measures is essential during construction.