76/132kV Porcelain Bushing Type Outdoor Power Cable Termination

76/132kV Porcelain Bushing Type Outdoor Power Cable Termination

Product Description

The 76/132kV Porcelain Bushing Type Outdoor Power Cable Termination is a robust, high-voltage solution designed for terminating power cables in outdoor substations and overhead transmission systems. Combining a porcelain insulator with a precision-engineered metal fitting, this termination provides:

• Excellent electrical insulation – withstands high voltage stress without breakdown

• High mechanical strength – resists wind, ice, and seismic loads

• Superior resistance to harsh outdoor environments – UV, moisture, salt, and industrial pollutants

The porcelain bushing is glazed to enhance hydrophobicity (water repellency) and prevent pollution flashover, while the inner conductor connection features compression or bolted joints for low-resistance conductivity.

Engineered to operate at 76kV and 132kV, the termination incorporates stress control electrodes to manage electrical field gradients at the cable-insulation interface, significantly reducing the risk of partial discharge (PD). The porcelain housing is designed with multiple sheds to increase creepage distance, making it suitable for polluted areas with high levels of:

• Dust (desert regions, industrial zones)

• Salt (coastal and marine environments)

• Industrial fallout (chemical plants, refineries, cement works)

The metallic base is hot-dip galvanized to resist corrosion, ensuring long-term reliability in:

• Coastal zones (salt spray exposure)

• Industrial areas (chemical vapors, acidic rain)

• High-humidity environments (tropical and subtropical regions)

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Key Features

Superior Insulation Performance

• The porcelain bushing offers high dielectric strength and excellent thermal shock resistance

• Flashover voltage is 20% higher than composite alternatives in clean environments

• Material: High-grade alumina porcelain (≥ 85% Al₂O₃) per IEC 60672

• Test voltage withstand: 275 kV rms for 1 minute (132kV class)

Pollution Resistance

• Glazed surface minimizes contaminant accumulation

• Shed profile optimizes self-cleaning during rain

• Optional anti-pollution coatings available for severe pollution classes (IV–V), including:

• RTV silicone rubber coating (room temperature vulcanizing)

• Fluoropolymer coating (long-term hydrophobic protection)

• Creepage distance (pollution class specific):

Mechanical Robustness

• Wind resistance: Withstands wind speeds up to 300 km/h (hurricane force)

• Ice load capacity: Withstands ice thickness up to 50 mm

• Seismic withstand: Tested for horizontal acceleration up to 0.5 g (Richter magnitude 8+)

• Cantilever strength: ≥ 5,000 N (depending on flange design)

• Torsional strength: ≥ 2,000 N·m

Easy Installation

• Standardized flange interfaces comply with:

• IEC 60137 (Bushings for alternating voltages above 1,000 V)

• ANSI C57.19 (Bushings for power transformers)

• Allows quick integration with:

• Switchgear (GIS and AIS)

• Power transformers

• Busbars and disconnect switches

• Lightning arresters

Low Maintenance

• Porcelain's inert surface requires minimal cleaning

• Typical cleaning interval: Pressure washing every 5–7 years in polluted areas (vs 1–2 years for polymeric bushings)

• No UV degradation – porcelain does not age or chalk under sunlight

• No tracking or erosion – unlike silicone rubber, porcelain is immune to surface tracking

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Technical Specifications

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Comparison: Porcelain vs Composite Terminations

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Applications

Outdoor Substations

Terminates high-voltage cables connected to:

• Circuit breakers (SF6 and vacuum types)

• Power transformers (generator step-up, distribution)

• Lightning arresters (surge protection)

• Disconnect switches and busbars

• Capacitor banks and reactors

Suitable for regional and national grid substations at 66kV, 110kV, 132kV, and 150kV voltage levels.

Coastal Power Plants

The corrosion-resistant galvanized steel and glazed porcelain ensure longevity in salt-laden marine environments, including:

• Nuclear power plants (coastal locations)

• Thermal power plants (near seaports)

• Offshore wind farm onshore substations

• Desalination plants (coastal industrial facilities)

Industrial Substations

Used in steel plants, refineries, and chemical facilities, with specialized coatings to resist:

• Chemical vapors (H₂S, SO₂, NH₃, chlorine)

• Conductive dust (carbon, metal particles)

• Oil mist and hydrocarbon contamination

• High temperature (up to 70°C continuous)

High-Altitude Grids

Performs reliably at altitudes up to 4,000 meters above sea level, with increased creepage distance compensating for reduced air density. Derating factors apply:

• 1,000–2,000 m: no derating

• 2,000–3,000 m: 5% derating

• 3,000–4,000 m: 10% derating

Renovation Projects

Retrofits older substation infrastructure, replacing degraded terminations with maintenance-free porcelain solutions. Benefits include:

• Direct replacement for legacy porcelain terminations (same flange dimensions)

• Improved creepage distance (higher pollution class)

• Lower maintenance costs over 30+ year service life

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Installation Guidelines

Preparation

• Cable end preparation – remove outer sheath, armor, insulation screen per manufacturer's drawing

• Stress cone installation – apply pre-molded or taped stress cone (included or optional)

• Conductor connection – compression or bolted lug, torque to specification

Mounting

• Flange mounting – secure to equipment flange with stainless steel bolts (torque 50–80 N·m for M12)

• Gasket – ensure proper compression (rubber or silicone gasket included)

• Grounding – connect termination flange to station ground grid

Testing After Installation

• Power frequency voltage test – 1 minute at 80% of factory test voltage

• Partial discharge measurement – confirm < 10 pC at 1.5U₀

• Insulation resistance test – 5 kV megger, ≥ 10 GΩ

• Visual inspection – check for cracks, contamination, or damage

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FAQ (Expanded)

Q: What is the difference between normal and heavy pollution class terminations?

A: Heavy pollution class terminations have:

• Taller sheds (greater shed spacing)

• Increased creepage distance (e.g., 3,100 mm for 132kV normal, 3,750 mm for heavy pollution)

• Optional anti-pollution coatings (RTV silicone or fluoropolymer)

These features are suitable for areas with conductivity > 100 μS/cm (equivalent to:

• Coastal zones within 5 km of shoreline

• Industrial areas with high SO₂ or particulate emissions

• Desert regions with conductive dust

Q: Can the porcelain bushing withstand physical impacts?

A: While porcelain is brittle, the termination is designed with a shock-absorbing flange that:

• Dampens vibrations from nearby equipment (transformers, breakers)

• Absorbs minor impacts (tools, debris) without transmitting force to the porcelain

• Includes rubber gaskets at mounting interfaces to reduce stress concentration

For areas with high vandalism risk (e.g., urban substations), consider protective cages or composite terminations.

Q: Is the termination compatible with both oil-filled and XLPE-insulated cables?

A: Yes. The termination supports multiple cable types with adaptable insulation interfaces and sealing mechanisms:

Q: How is the electrical stress managed at the cable termination point?

A: A graded stress cone made of semi-conductive material (EPDM or silicone rubber) is installed at the insulation shield cut-off. The stress cone:

• Equalizes the electric field – eliminates stress concentration points

• Reduces tangential stress – prevents surface tracking

• Eliminates partial discharge – ensures clean PD levels (< 5 pC)

The stress cone is either:

• Pre-molded (factory-formed, ready to install)

• Tape-based (field-applied, for custom cable dimensions)

Q: What is the recommended torque for conductor connections?

A: Torque values depend on conductor size and terminal type:

Detailed torque values and compression die sizes are provided in the installation manual.

Q: What is the expected service life?

A: > 50 years for porcelain terminations under normal operating conditions, compared to:

• Composite terminations: 25–35 years

• Oil-filled terminations: 30–40 years

Porcelain's inert surface and UV resistance eliminate aging-related degradation, making it the preferred choice for long-life assets (substations, transmission lines, nuclear plants).

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Compliance and Certifications

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Packing and Shipping

Shipping methods:

• Sea freight – standard for large quantities

• Air freight – for urgent replacement orders

• Land freight – regional delivery

Documentation included:

• Packing list

• Commercial invoice

• Routine test report

• Installation manual

• Quality certificate

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