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Post Insulator Busbar Support Insulator 12kV 24kV 40.5kV
Post insulator and busbar support insulator series are epoxy resin insulation components engineered for 12kV, 24kV, and 40.5kV medium voltage switchgear. Manufactured using APG casting technology, these post insulators feature a high-density, void-free epoxy matrix with deep alternating creepage skirts for high flashover resistance. Embedded brass threaded inserts on both ends provide secure and standardized busbar mounting. Available in multiple sizes and heights to support KYN28, HXGN, RMU, and GIS-type panels, these busbar support insulators deliver reliable dielectric performance in high-humidity, salt-laden, and extreme temperature environments common in Middle Eastern installations.
- Overview
- Applications
- Technical Data
- Services
- Quality Control
- Recommended Products
Epoxy Resin Post Insulator - 12kV / 24kV Busbar Support
Post insulators mechanically support medium voltage busbars while electrically isolating them from the earthed steel enclosure. They carry the weight of the copper busbar run continuously, and must also withstand the violent electromagnetic forces generated during a short circuit without cracking or allowing the busbar to move. MOLDVOLT manufactures 12kV and 24kV post insulators using APG casting, to IEC 60168 and IEC 62217.
APG CASTING - WHY THE PROCESS DETERMINES SERVICE LIFE
Automatic Pressure Gelation injects resin into a heated mould under pressure and gels it progressively from the mould surface inward. The result is a void-free, high-density matrix with consistent mechanical properties.
Voids are the enemy. A gas-filled void inside cast epoxy sits in a region of concentrated electrical stress, and at operating voltage it begins to discharge internally. Each discharge erodes a little more of the surrounding resin. The insulator tests perfectly on delivery and fails five or ten years into service - long after the warranty, and usually taking the busbar and panel with it. This is why every insulator we produce is partial-discharge tested, typically below 10 pC at 1.1 times rated voltage, rather than being visually inspected and shipped.
CYCLOALIPHATIC EPOXY - MATERIAL CHOICE FOR HARSH CLIMATES
We specify cycloaliphatic epoxy rather than general-purpose bisphenol resin. Cycloaliphatic resin resists surface tracking and UV degradation far better, which is what allows the same component to serve a 55 C salt-laden Gulf coastal substation, a humid West African installation and a -45 C Siberian panel across a -40 C to +105 C service range. Bisphenol resin is cheaper and is entirely adequate in a clean, dry, temperate switchroom - and entirely inadequate in the environments our markets actually operate in.
MECHANICAL RATING
Rated cantilever load runs from 1000N to 2500N depending on type. Selection is driven by busbar weight, support spacing and prospective short-circuit current, since the electromagnetic force between adjacent phases during a fault can be many times the static load. Specifying by voltage alone, without checking cantilever strength against the fault level, is a common error.
SUPPLY
Available as OEM production to customer drawings with customer part numbering, and as direct-replacement spares for KYN28, HXGN, RMU and GIS panels. Standard mounting is M10 or M12 stud, customisable. Standard colour RAL 7035 grey; red and other colours available.
PRIMARY APPLICATIONS
- Main busbar support in KYN28-12 and KYN28-24 metal-clad switchgear busbar compartments.
- Branch and riser busbar support within switchgear panels.
- Busbar support in HXGN ring main cabinets and compact substations.
- Support insulation in fixed-type switchgear and distribution panels.
- Isolating support for disconnectors, earthing switches and instrument transformer mountings.
- Busbar support in LV distribution boards and motor control centres, using the appropriate LV rating.
- Replacement spares for aged switchgear across the installed base in Africa, CIS and the Middle East, where the original part is often no longer available from the panel manufacturer.
- Panel builder and switchgear workshop production stock.
WHY THIS IS A HIGH-DEMAND SPARE
Post insulators are damaged during panel maintenance, cracked by short-circuit forces, and degraded by pollution in coastal and industrial environments. Because they are structural, a cracked insulator takes the panel out of service until it is replaced. Limited spare parts availability is consistently identified as a leading barrier in Middle East and African electrical markets, so we hold standard types in stock and supply single-piece emergency replacements as well as bulk production volumes.
SELECTION GUIDANCE
Specify by four parameters together, not by voltage alone: rated voltage and BIL, rated cantilever load against the prospective short-circuit force, mounting interface and height, and pollution level of the installation environment. For coastal Gulf and West African sites, specify extended creepage.
REGIONAL FIT
- Middle East: high UV, high temperature and coastal salt fog make cycloaliphatic resin and extended creepage the correct specification.
- Africa: humid coastal and industrial pollution environments; high replacement demand across an aged installed base.
- Russia and CIS: -40 C to -60 C service requires verified low-temperature mechanical performance, since epoxy embrittles as temperature falls.
- Eastern Europe: standard IEC 60168 service in temperate conditions.
NOT SUITABLE FOR
Outdoor unprotected installation unless specified with outdoor creepage and UV-stabilised formulation. Loads exceeding rated cantilever strength. Systems above the rated voltage of the selected type.
TECHNICAL DATA - Epoxy Resin Post Insulator
| Parameter | 12 kV Type | 24 kV Type |
| Compliance | IEC 60168, IEC 62217 | IEC 60168, IEC 62217 |
| Rated Voltage | 12 kV | 24 kV |
| Power-Frequency Withstand Voltage (1 min, wet) | 42 kV | 50 kV |
| Lightning Impulse Withstand Voltage (BIL) | 75 kV peak | 125 kV peak |
| Partial Discharge | < 10 pC at 1.1 × Uₙ | < 10 pC at 1.1 × Uₙ |
| Rated Cantilever Load | 1000 / 1500 / 2000 / 2500 N | 1000 / 1500 / 2000 N |
| Rated Tensile Load | To specification | To specification |
| Rated Torsion Load | To specification | To specification |
| Safety Factor | Min. 2.0 against rated cantilever load | Min. 2.0 against rated cantilever load |
| Material | Cycloaliphatic epoxy resin, APG cast | Cycloaliphatic epoxy resin, APG cast |
| Filler | Silica, controlled ratio | Silica, controlled ratio |
| Colour | RAL 7035 light grey (standard); red / custom available | RAL 7035 light grey (standard); red / custom available |
| Inserts | Brass or steel threaded inserts, cast in | Brass or steel threaded inserts, cast in |
| Mounting | M10 or M12 stud, top & bottom; customisable | M10 or M12 stud, top & bottom; customisable |
| Height Range | 60 – 240 mm (depending on type) | 60 – 240 mm (depending on type) |
| Surface Profile | Smooth or shedded (per creepage requirement) | Smooth or shedded (per creepage requirement) |
| Standard Creepage Distance | ≥ 16 mm/kV (light pollution) | ≥ 16 mm/kV (light pollution) |
| Extended Creepage | 20 mm/kV / 25 mm/kV (medium & heavy pollution) | 20 mm/kV / 25 mm/kV (medium & heavy pollution) |
| Operating Temperature | −40 °C to +105 °C | −40 °C to +105 °C |
| Altitude | Up to 1000 m standard; up to 2000 m on request | Up to 1000 m standard; up to 2000 m on request |
| Humidity | Suitable for tropical & high-humidity service | Suitable for tropical & high-humidity service |
| Flame Retardancy | UL94 V-0 grade available | UL94 V-0 grade available |
OPTIONS
Extended creepage for coastal and heavy-pollution sites | custom height, diameter and mounting interface | customer part numbering and packaging | flame-retardant UL94 V-0 formulation | low-temperature verified formulation for GOST 15150 climatic service | red or custom colour | OEM production to customer drawing
SPECIFICATION AND SOURCING
- Send a drawing, a sample or a photograph with the existing part number and we will identify the equivalent and confirm fit before you commit to an order.
- Reverse engineering from a physical sample where the original part is obsolete or the OEM no longer supplies it - common for aged KYN28, HXGN and imported panels still in service across Africa, CIS and the Middle East.
- OEM and private-label production to your drawings, with your part numbering and packaging.
- Material and plating selected for the destination environment: silver plating for lowest contact resistance indoors, tin plating for coastal and industrial atmospheres where salt fog and sulphides attack silver.
WHY THIS MATTERS COMMERCIALLY
Limited local technical expertise and difficult spare parts supply are consistently identified as the main barriers in Middle East and African electrical markets. A panel is out of service for as long as it takes the part to arrive. We hold consumable items in stock and quote fleet spares lists against your installed base so the part is on the shelf before it is needed.
QUANTITY AND LEAD TIME
- Stock items dispatched from inventory; typical production lead time 15-25 days for standard specifications.
- Low minimum order quantities on standard parts - we supply single-piece emergency replacements as well as bulk production volumes.
- Air freight for breakdown situations, sea freight consolidation for planned restocking.
TESTING AND DOCUMENTATION
- Routine testing per applicable IEC standard with results supplied per batch.
- Material certificates, plating thickness reports and dimensional inspection records available on request.
- Certification support for SONCAP, KEBS PVoC, SABER and GOST R submissions where the component ships as a standalone consignment.
AFTER-SALES
- Technical response within 24 hours; application engineering support for fit, assembly torque and maintenance intervals.
- Warranty against manufacturing and material defects: 12 months from delivery.
- Framework and call-off agreements available for panel builders, utilities and switchgear service workshops.
MATERIAL CONTROL
- Copper verified as T2 grade electrolytic copper or specified copper-silver alloy, with mill certificates retained per batch.
- Epoxy resin verified as cycloaliphatic grade with documented gel time, viscosity and filler ratio; general-purpose bisphenol resin is not accepted for outdoor or high-humidity service because of its poorer tracking and UV resistance.
- Plating thickness measured by X-ray fluorescence and recorded per batch - typically 8-12 microns of silver on contact surfaces. Under-plating is invisible on delivery and only shows up years later as a thermal fault, so this is measured rather than assumed.
PROCESS CONTROL
- APG (Automatic Pressure Gelation) casting under controlled mould temperature, injection pressure and gel time, producing a void-free matrix. Voids initiate partial discharge, and partial discharge is what eventually punctures an insulator in service.
- Vacuum degassing of resin before injection to eliminate entrapped air.
- Controlled post-cure cycle to relieve internal stress and stabilise dimensions.
- Contact finger spring force calibrated and verified against specification, ensuring uniform current sharing across all fingers.
ROUTINE TESTING - EVERY PIECE OR EVERY BATCH
- Partial discharge test on insulation components, typically below 10 pC at 1.1 times rated voltage.
- Power-frequency withstand voltage test.
- Contact resistance measurement on current-carrying parts.
- Dimensional inspection against drawing, with critical fit dimensions 100% checked.
- Visual inspection for cracks, voids, plating defects and surface finish.
- Mechanical load testing on insulators against rated cantilever strength.
TYPE TESTING
- Insulators verified to IEC 60168 and IEC 62217; contacts and conductive parts verified for temperature rise within the 70K limit of IEC 62271-1 at rated current.
- Thermal cycling and, for parts destined for coastal service, salt-spray corrosion testing.
TRACEABILITY AND SYSTEM
- ISO 9001 quality management system.
- Batch numbering linking finished parts back to raw material certificate and process records.
- Certificates of conformity, material certificates and test reports issued with each shipment.
- Retained samples held per production batch for future reference in the event of a field query.
