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120kN U120BL High Voltage Cap and Pin Type Toughened Disc Suspension Glass Electric Insulator
The U120B glass insulator offers high strength, corrosion resistance, and a long service life. With stable mechanical performance, it can withstand an electromechanical load of 120kN, making it suitable for high-voltage transmission lines. Its glass material enables self-shattering upon failure, simplifying inspection, while its smooth surface resists contamination, ensuring safe and reliable power system operation.QOCI Electric‘s glass insulator products are of exceptional quality, manufactured using high-purity raw materials and advanced production techniques. They boast outstanding mechanical strength, weather resistance, and electrical performance. Rigorously tested, these insulators ensure superior anti-aging properties, excellent pollution flashover resistance, and long-term operational stability. Suitable for harsh environments, they provide reliable protection for safe and efficient power system operation.
Product Information

- Model:U120BL
- U Refers To Disc Suspension Insulator
- 120 indicates a rated Mechanical failing load of 120kN
- B For Ball And Socket Type
- L Stands For Long Steel Foot
- 146- indicates that the height of the insulator structure is 146mm, and there are also insulators with spacing of 127mm.
- 255- indicates that the diameter of the insulator disc is 255mm, and there are also insulators with disc diameters of 280mm, 300mm, 320mm, 380mm, 420mm, etc.
- 320- indicates that the creepage distance of the insulator is 320mm, and there are also insulators with creepage distances of 400mm, 450mm, 550mm, etc.
- Type: Standard profile Toughened Suspension Type
- Rated mechanical load: 120kn (about 12 tons)
- Purpose: Widely applicable as insulation support for medium and high voltage transmission lines and substation equipment, capable of stable operation under various climatic conditions.
- The product model is in accordance with IEC60383-1:1993,MOD / GB/T1001.1
- The connection structure is in accordance with GB/T4056-2008(IEC60120:1984,MOD) and BS 3288 part lll.
- According to customer requirements, the locking pin can be either W-pin or R-pin.
- lf there is no special instruction, W pin is used for U120BL
Product drawing

Product parameters
| IEC designation | U120BS/127 | U120BL/146 | |
| Mechanical failing load | kn | 120 | 120 |
| Diameter D | mm | 255 | 255 |
| Height H | mm | 127 | 146 |
| Creepage distance L | mm | 320 | 320 |
| Socket coupling | mm | 16 | 16 |
| Wet power frequency withstand voltage | kv | 40 | 40 |
| Dry lightning impulse withstand voltage | kv | 100 | 100 |
| Power frequency puncture voltage | kv | 130 | 130 |
| Radio interference voltage(10kV 1MHz) | μv | 50 | 50 |
| Corona visual test | kv | 18/22 | 18/22 |
| Power frequency electric arc voltage | ka | 0.12s/20Ka | 0.12s/20Ka |
| Impulse puncture voltage | P.U | 2.8 | 2.8 |
| Net weight per unit | kg | 4 | 4 |
Suspension insulator components

Suspension insulators consist of the following elements:
- - One dielectric made of toughened glass with the appropriate properties and shape for the environmental conditions in which it must function.
- - One hot-dip galvanized nodular or ductile malleable cast iron cap.
- - One hot-dip galvanized forged steel pin.
- - The cap and pin are assembled on the glass piece using aluminous cement with the appropriate properties to withstand the thermomechanical efforts.
Lastly, the insulator cap has a stainless steel or phosphor bronze locking device (split pin) which secures the coupling of the units.
Similarly, the pins may be protected using an anti-corrosion zinc sleeve (sacrificial anode), when requested. This zinc sleeve is strongly recommended for insulators which are going to be used in lines with heavy pollution.
Glass insulator shell Cross-section
under long-term electrical stress, contaminants can trigger local arcs, leading to insulator surface carbonization (electrocorrosion). Enough creep distance to disperse the strength of the electric field, reduce the risk of local discharge and extend the life.

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