Altasuneko kableen metalikoa geruza baten errepasoa

I. Kableen Metala Ingurunearen Funtzioak eta Berreskurapenaren Anitzasuna

Tentsio altuena duen kableen metala ingurunea, isolamenduaren kanpoan kokatutako metalikoa da, plomo ingurune, aluminio ingurune eta arrazoi-arrasteko zulaitza motak barne. Bere funtzio nagusiak dira mekanikoak (kanporako eragin eta presio kontra), elektrokimikoen korrosioa saihesteko (higrosoila eta lur-zatiketa isolatzen ditu), elektrizitate magnetikoaren isurtzea (inguruari elektrizitate magnetikoaren eragin murriztea) eta lurrera erantsi duten bide bat eskaintzea (akidentuen elektrizitatea segurtasunez kendu). Ezabatua dagoenean, metala ingurunea isolamenduaren higrosoila sartu, elektrizitate lokalaren distorsio edo akidentu serioak gertatu daitezke, hala nola kableen ezabaketa eta kortokircuitua. Horregatik, ezabatuen mota desberdinetarako berreskurapen zehatzak kable sistema segurtasunez garatzeko oso garrantzitsuak dira.

II. Akidentuaren Diagnostika eta Ebaluazioa Berreskurapen Aurretik

(A) Ezabatuen Mota Identifikatzeko

• Ezabatu Mekanikoak: Dintsu, trinkadura edo kolpeak ingurunean agertzen dira, instalatzerakoan mekaniko rolaketak edo objektu zuzenen kolpeak edo oinarrizko ekuilibrioko urte luzeetan egindako tensioa emanda.

• Elektrokimikoen Korrosioa: Lurreko zerbitzuko elektrizitatea edo asidikoki/alkalineko inguruneak metala ingurunean korrosioa ekar ditzake, lokalki bulatzen, oxido egiten, kolpe egiten eta zurigorri/berdeko korrosio produktuak (aluminio ingurunea) edo beltza sulfuro (plomo ingurunea).

• Thermal Aging Damage: Arrazoian beharrezkoa da materialen embrittlement, horrek kolpeak eta delaminazioak sortzen ditu, gehienbat elkarketa edo kalor-solten espazio txikietan aurkitzen dira.

(B) Detektore teknologien aplikazioa

• Ikusmen kontuan: Erabil endoskopioak edo termografikoak ingurunearen gainazalari begiratzeko, kolpe evidenteak eta puntu heziek identifikatzeko.

• Ingurunearen Uztarte Testa: DC uztarte testa (10 kV minutu bat) ingurunearen isolamendu integritatea probatzeko. Legegatik igaro den korrontea (10 μA) kolpe bat adierazten du.

• Partial Discharge Detection: HFCT (High-Frequency Current Transformer) erabiliz kolpe puntuetako partial discharge signalak jaso, legegatik ±0.5 m tartearekin kokatu.

• Lurreko Korrosibotasuna Ebaluatzeko: Cablearen lurreraino doazen pH, kloroionen kontzentrazioa eta zerbitzuko elektrizitatearen dentsitatea probatzeko lagundu egiten du, berreskurapen materialen hautapentzat oinarria ematen du.

III. Berreskurapen Materialen eta Tresna Espetsializatuak

(A) Nukleo Berreskurapen Materialak

• Metala Ingurune Aldaketa Materialak:

• Aluminium Alloy Compression Sleeve: Aluminio inguruneen berreskurapentzat, ductility ona eta korrosio saihestu ona. Kablearen kanpo-diametroa bete behar da (tolerantzia ≤ ±0.5 mm).

• Lead-Tin Alloy Tape: Plomo inguruneen berreskurapentzat, eritze puntua (183°C inguruan), termikoki soldatu erraza, GB/T 12706.2 puritate eskatzen du (plomo Gehienez 99.9%).

• Stainless Steel Corrugated Tube: Arrazoi-arrasteko zulaitzaren kolpeentzat, 304 inoxidableko zulaitza, horma ≥ 0.8 mm, kolpe eta lurpresio saihestu.

• Insulation and Sealing Materials:

• Cross-Linked Polyethylene (XLPE) Heat-Shrink Tubing: Tsunama 120–140°C, shrink ratio ≥ 2:1, breakdown strength ≥ 25 kV/mm, hot-melt adhesive sealing required.

• Silicone Rubber Cold-Shrink Tubing: Elastic recovery for sealing, no heating required, suitable for confined spaces, Shore hardness 60 ± 5 Shore A, tanδ ≤ 0.003 (20°C, 50 Hz).

• Butyl Rubber Sealing Tape: Used as auxiliary sealing layer, tensile strength ≥ 3 MPa, elongation at break ≥ 400%, aging resistance retains ≥ 80% performance after 100°C × 168 h thermal aging.

• Corrosion Protection Materials:

• Zinc-Aluminum Alloy Sacrificial Anode: For high-corrosion soil environments, anode purity ≥ 99.5%, current density ≥ 15 mA/m², design life ≥ 20 years.

• Polyvinyl Chloride (PVC) Corrosion-Resistant Tape: Thickness ≥ 0.4 mm, tensile strength ≥ 18 MPa, environmental stress cracking resistance (ESCR) ≥ 1000 h.

(B) Specialized Tools

• Preparation Tools: Angle grinder (with 80-grit alumina grinding wheel), wire brush, anhydrous ethanol cleaner, stainless steel scraper (for removing corrosion products).

• Forming Tools: Hydraulic crimping tool (crimping range 60–200 mm²), heat gun (temperature range 50–600°C), lead sealing dedicated torch (flame temperature ≤ 300°C).

• Testing Tools: Megohmmeter (2500 V, range 0–10000 MΩ), double-arm bridge (contact resistance measurement, accuracy ±0.1 μΩ), ultrasonic thickness gauge (resolution 0.01 mm).

IV. Detailed Repair Procedures by Damage Type

(A) Mechanical Damage Repair (Aluminum Sheath Example)

• Damage Area Preparation

• Use an angle grinder to cut open the damaged sheath axially, with cut length 5 times the damage diameter (minimum ≥ 100 mm), exposing clean insulation shield.

• Remove burrs from sheath edges with a stainless steel scraper, sand to metallic luster, clean oil with ethanol, and dry for ≥ 15 min.

• Metallic Sheath Restoration

• Select an aluminum alloy compression sleeve with inner diameter 1 mm larger than cable outer diameter, uniformly coat inner wall with conductive grease (nickel-based filler, volume resistivity ≤ 5×10⁻⁴ Ω·cm).

• Slide the sleeve over the damaged area, use a Staggered Crimping method, crimp from center to ends. After crimping, hexagonal opposite-side deviation ≤ ±0.1 mm, contact resistance ≤ 20 μΩ.

• Sealing and Anti-Corrosion Treatment

• Wrap butyl rubber sealing tape with 50% overlap, forming a sealing layer ≥ 3 mm thick, extending ≥ 50 mm beyond undamaged sheath on both ends.

• Install heat-shrink tubing, heat gradually from center to ends (120°C → 140°C) to avoid bubbles. After cooling, check uniform shrinkage (post-shrinkage wall thickness ≥ 2 mm).

• Wrap PVC corrosion-resistant tape externally in a half-overlap spiral, secure ends with stainless steel straps (torque 15–20 N·m).

(B) Electrochemical Corrosion Repair (Steel Armor + Lead Sheath Composite Sheath)

• Corrosion Product Removal

• Use sandblasting (quartz sand 80–120 mesh, pressure 0.4–0.6 MPa) to remove rust from steel armor, exposing gray-white metal base, surface roughness Sa2.5 grade.

• Trim lead sheath corrosion area with a lead plane, forming a smooth transition with slope ≥ 1:5 to avoid stress concentration.

• Sacrificial Anode Protection

• Symmetrically install 2 zinc-aluminum alloy anodes (100 mm × 50 mm × 10 mm) on both sides of the repair section, connected to steel armor via copper braid (cross-section ≥ 16 mm²), welded (lap length ≥ 30 mm, welding current 120–150 A).

• Fill gap between anode and cable sheath with petroleum jelly, encapsulate externally with high-density polyethylene (HDPE) housing to ensure full soil contact.

• Dual Sealing Structure

• Inner layer: cold-shrink silicone rubber tubing, inner wall coated with semiconductive water-blocking gel (volume resistivity 10–100 Ω·cm). Maintain at room temperature for 24 h after recovery for curing.

• Outer layer: pour epoxy resin (E-51 type, curing agent T-31, ratio 100:25), mold sealed at 0.2 MPa pressure, cure ≥ 48 h at 25°C. Post-cure Shore hardness ≥ 85 Shore D.

(C) Thermal Aging Cracking Repair (XLPE Insulated Cable)

• Crack Area Reinforcement

• Cut a V-groove along the crack direction (depth 1/3 of sheath thickness, angle 60°), fill with heat-resistant silicone rubber (temperature rating ≥ 180°C, tear strength ≥ 15 kN/m), level with scraper, cure at room temperature for 2 h.

• Wrap glass fiber cloth (0.2 mm thick, 16×16 threads/cm), impregnate with epoxy resin (solid content ≥ 70%) to form a reinforcement layer. Tensile strength ≥ 200 MPa after curing.

• Heat Dissipation Optimization

• Install aluminum heat sinks (1.5 mm thick, fin spacing 5 mm) externally on the repair section, bonded to sheath with thermal grease (thermal conductivity ≥ 1.5 W/(m·K)) to reduce local temperature rise (≤ 5°C).

• Monitor operating temperature with infrared thermal imager, ensuring temperature difference from undamaged section ≤ 2°C.

V. Quality Control and Acceptance Standards

(A) Key Parameter Testing

• Electrical Performance: Sheath insulation resistance ≥ 1000 MΩ (2500 V megohmmeter), partial discharge ≤ 5 pC (at 1.73U₀ voltage).

• Mechanical Performance: Impact resistance of repair section ≥ 10 J (at -30°C), bending radius ≥ 20 times cable outer diameter (no obvious deformation).

• Sealing Performance: After immersion test (room temperature, 24 h), sheath leakage current change rate ≤ 10%, no bubbles or water ingress.

(B) Long-Term Reliability Verification

• Accelerated Aging Test: Place repair sample in thermal aging chamber (135°C × 1000 h), after removal insulation resistance retention ≥ 80%, tensile strength degradation ≤ 20%.

• Soil Burial Test: Simulate actual laying environment, buried depth 1 m, duration 1 year, check for no corrosion perforation or seal failure.

VI. Safety Operation Regulations

• Power-Off Work Requirements: Follow "power-off - voltage test - grounding wire installation" procedure before repair. Hang "Do Not Close" warning signs on cable terminations, set safety barriers (distance ≥ 8 m) within work radius.

• Hot Work Management: When using torches or welding, equip dry powder fire extinguishers (ABC type, capacity ≥ 4 kg), clear flammable materials within 3 m, assign a dedicated supervisor.

• Personal Protective Equipment (PPE): Wear insulated gloves (35 kV rating), goggles, flame-resistant workwear. Use safety harness (static load test force 2205 N, hold 3 min without break) for work at heights (≥ 2 m).