H1: U300B Insulator — 300kN Porcelain Suspension Insulator for Overhead Transmission Lines
U300B Insulator is a high‑strength suspension insulator designed for medium‑ to high‑voltage overhead transmission lines, fully compliant with IEC, BS, and AS standards. This U300B Insulator delivers outstanding mechanical endurance and reliable electrical insulation even in harsh outdoor environments.
Its cap‑and‑pin construction ensures stable mechanical performance under extreme temperature cycling from -40°C to +105°C. Whether used in coastal salt‑fog zones, industrial pollution areas, or remote desert regions, the U300B Insulator offers unparalleled reliability and durability. For project engineers seeking a proven solution, the U300B Insulator provides a cost‑effective choice for long‑term service.
H2: U300B Insulator Technical Specifications
The U300B Insulator (also known as type XP‑300) has a rated combined mechanical and electrical (M&E) failing load of 300kN (67,400 lbf), making it suitable for extra‑heavy‑duty transmission applications, including areas with extreme ice loading, very long spans, and high wind conditions.
Its nominal creepage distance is 375mm, and the 50% impulse flashover voltage is 135kV (positive) and 140kV (negative), effectively preventing flashovers even in heavily polluted coastal or industrial areas. The disc diameter is 320mm (12.6 inches), and the unit spacing is 195mm (7.7 inches). The coupling hardware complies with IEC 120 standard 24 type, ensuring full interchangeability with standard fittings.
Standard glaze colors are brown, light gray, or blue. The porcelain body is manufactured by the wet process, and zinc‑sleeve pins are optionally available upon request.
Complete U300B Insulator Technical Data per IEC, BS, and AS Standards:
| S/N | Parameter | Value |
| 1 | IEC Class | U300B |
| 2 | Type / Model | XP‑300 |
| 3 | Glaze Color | Brown / Light Gray / Blue |
| 4 | Porcelain Disc Diameter, D (mm) | 320 |
| 5 | Unit Spacing, H (mm) | 195 |
| 6 | Standard Coupling to IEC 120 | 24 |
| 7 | Creepage Distance (mm) | 375 |
| 8 | Combined M&E Strength (kN) | 300 |
| 9 | Routine Test Load (kN) | 120 |
| 10 | Power Frequency Flashover Voltage – Dry (kV) | 90 |
| 11 | Power Frequency Flashover Voltage – Wet (kV) | 53 |
| 12 | 50% Impulse Flashover Voltage – Positive (kV) | 135 |
| 13 | 50% Impulse Flashover Voltage – Negative (kV) | 140 |
| 14 | Power Frequency Withstand Voltage – Dry (kV) | 80 |
| 15 | Power Frequency Withstand Voltage – Wet (kV) | 47 |
| 16 | Impulse Withstand Voltage (kV) | 125 |
| 17 | Power Frequency Puncture Voltage (kV) | 130 |
| 18 | Net Weight, Each, Approx. (kg) | 13.5 |
| 19 | Applicable Standards | IEC, BS, AS |
Note: Technical data are derived from standard specifications. Alternative creepage distances, diameters, or unit spacings can be provided upon request.
H2: U300B Insulator Material & Construction
Every unit of the U300B Insulator is made from high‑grade alumina porcelain, fired at over 1,300°C to achieve maximum density and near‑zero porosity. The cap is produced from malleable cast iron, and the pin from hot‑dip galvanised steel — both providing excellent corrosion resistance.
The cement bonding between porcelain and metal parts uses high‑quality Portland cement, ensuring stable mechanical performance under extreme thermal cycling from ‑40°C to +105°C. The hard, glossy glaze coating offers good self‑cleaning properties, reducing maintenance frequency. For more on porcelain manufacturing standards, visit the International Electrotechnical Commission (IEC).
H2: U300B Insulator Applications & Installation
The U300B Insulator is widely used on 69kV to 161kV AC overhead transmission lines, distribution networks, and substation entry towers, especially in regions with extremely heavy ice, very long spans, or high‑stress conditions. Its large diameter and long creepage distance provide outstanding pollution performance. Typical string configurations are:
- 69kV — 4 to 5 discs per string
- 115kV — 7 to 8 discs per string
- 138kV — 8 to 9 discs per string
- 161kV — 10 to 11 discs per string
It can be assembled into single, double, tandem, or V‑strings to meet various tension and suspension requirements. Whether for urban grid upgrades or rural electrification projects, the U300B Insulator offers a cost‑effective and durable insulation solution.
Standard coupling dimensions (24) ensure full compatibility with existing IEC fittings, sockets, and yokes. For live‑line maintenance, it allows easy hot‑stick handling, reducing outage time during replacement. Optional arcing horns and grading rings are available to optimise voltage distribution along the string.
Explore our full range of suspension insulators and transmission hardware for more options.
H2: U300B Insulator Quality & Performance Advantages
Compared to polymer alternatives, porcelain offers unmatched resistance to UV radiation, bird pecking, and scratch damage. Its hydrophobic glaze reduces continuous water film formation, significantly raising pollution flashover voltage.
Moreover, the U300B Insulator requires minimal routine maintenance and delivers a service life of over 50 years under normal operating conditions. Full testing procedures are detailed in IEC, BS, and AS standards, published by the International Electrotechnical Commission (IEC) and other recognised bodies. For installation guidance, refer to our insulator string assembly guide.
Every unit undergoes 100% routine electrical and mechanical testing before dispatch, including visual inspection, dimensional checks, mechanical load tests, and high‑voltage withstand tests. Prototype tests — such as temperature cycling, thermal‑mechanical performance, and radio interference voltage (RIV) — are also performed per applicable standards. Full test reports and traceability records are provided for each batch.
Each insulator is individually packed with foam cushioning and secured in sturdy wooden crates or corrugated cartons to prevent transit damage. We offer flexible shipping options (FOB, CIF, EXW) with lead times of 15‑30 days depending on order quantity.
For detailed datasheets, CAD drawings, or competitive pricing on the U300B Insulator, please contact our sales team via the inquiry form below. We also offer OEM services and free technical consultation for string assembly design.
H2: Why Choose Our U300B Insulator
When selecting a U300B Insulator for your transmission project, quality and reliability are paramount. Our U300B Insulator is subject to strict quality control at every production stage — from raw material inspection to final electrical testing. We understand that transmission line outages are costly, which is why each U300B Insulator is designed for long‑term durability.
With over a decade of experience in porcelain insulator manufacturing, we provide competitive pricing, fast delivery, and dedicated technical support. Whether you need a small sample batch or a full container order, our U300B Insulator is available with short lead times. Contact us today to learn how the U300B Insulator can enhance your grid reliability.
