Long Rod Insulators 3FL3 and 3FL4
Skip to Content
Long Rod Insulators 3FL3 and 3FL4
Long Rod Insulators 3FL
The 3FL insulator housing is a one-piece HTV1 silicone rubber housing made by the one-shot injection molding process. The HTV silicone is directly molded onto the core rod by overlapping the triple junction point and part of the metal end fittings. The design ensures a total enclosure of the most sensitive part of a silicone insulator - the junction zone (metal end fitting/FRP rod/silicone housing), where usually the highest electrical field strength is concentrated. This overlapping system eleiminates any need of traditional sealing systems while preventing any moisture ingress attacks.
The core rod is boron-free, corrosion-resistant ECR2 glass-fiber-reinforced plastic rod (FRP rod). Due to the extremely high hydrolysis and acid resistance of the FRP rod the risk of so-called brittle fracture is completely eliminated on 3FL insulators.
The end fittings, made of hot-dip galvanized forged steel or ductile cast iron, are directly attached to the FRP core rod by circumferential crimping process. Each crimping process is strongly monitored with a special control system. A complete range of end fittings according to the latest IEC and ANSI standards is available up to 210 kN of SML. The 3FL is 100% exchangeable and compatible with existing insulators and line hardware of all types.
The special design of the end fitting in the junction zone reduces the electrical field strength and partial discharge to a minimum, accordingly inside the junction zone as well as on the silicone housing surface by modeling an integrated grading ring. This relaibly prevents corrosion of the insulating material and eliminates the risk of subsequent failure of the insulator.
The excellent pollution layer characteristics of the HTV silicone rubber ensure maximum reliability of the 3FL insulator, even under extreme service conditions. The extremely hyrophobic housing prevents the formation of conductive film on its surface. Even the most severe ambient conditions, such as salt fog in coastal regions or dust-laden air in industrial areas, cannot impair the intrinsic hydrophobicity of the HTV silicone rubber. Surface currents and discharges are ruled out. Neither water nor dirt on the housing surface can cause insulator flashovers - a significant factor in insulator performance.
1HTV: High-temperature vulcanizing
2ECR glass: Electrical- and corrosion-resistant glass
The 3FL3 and 3FL4 long rod insulators for transmission power systems up to 550 kV
3FL3 and 3FL4 insulators are available with a SML of 100 and 120 kN.
|Highest voltage for equipement Um||kV||550||550|
|Nominal system voltage Un||kV||500||500|
|Standard rated1lightning impulse withstand voltage level|
(1.250µs, positive, dry)
|Standard rated2switching impulse withstand voltage level|
(250/2500µs, positive, dry), applies for Um > 300 kV
|Standard rated3short duration power-frequency withstand|
voltage level (1 min., wet), applies for Um up to 300 kV
|Specified mechanical load, SML class as per IEC||kN||100||120|
|Specified mechanical load, SML class as per ANSI||klbs||25||30|
|Max. available section lengths |
(with Socket & Ball end fittings)
|length increments app. 52 mm||mm||5553||5553|
|length increments app. 2.05 inches||inch||218.6||218.6|
1 Standard rated voltages according to IEC 60071-1
2 Switching impulse withstand voltage is not applicable for system voltages
with Um < 300 kV
3 Power-frequency withstand voltage is not applicable for system voltages
with Um > 245 kV
(Top End Fitting)
(Conductor End Fitting)
|245||None||Ø 210 (Ø 8.3)|
|300||None||Ø 330 (Ø 13)|
|362||None||Ø 330 (Ø 13)|
|420||Ø 210 (Ø 8.3)||Ø 330 (Ø 13)|
|550||Ø 210 (Ø 8.3)||Ø 420 (Ø 16)|