Line Post Insulators
ANSI 57 Series
High-strength wet-process solid-core C-130 porcelain body with hot-dip galvanized steel hardware. Tie top, clamp top, and gain base configurations. Engineered for distribution and sub-transmission lines from 15 kV to 69 kV.
ANSI C29.7 — Full Series Data
Standard Series — Tie Top (Short Stud S / Long Stud L)
| Class | Creepage | Dry Arc | M&E | Dry FO | Wet FO | Impulse+ | Impulse− | Weight |
|---|---|---|---|---|---|---|---|---|
| 57-1S / 57-1L | 356 mm | 165 mm | 12.5 kN | 70 kV | 50 kV | 120 kV | 155 kV | 5.0 kg |
| 57-2S / 57-2L | 559 mm | 241 mm | 12.5 kN | 100 kV | 70 kV | 160 kV | 205 kV | 9.8 kg |
| 57-3S / 57-3L | 737 mm | 311 mm | 12.5 kN | 125 kV | 95 kV | 200 kV | 260 kV | 12.0 kg |
| 57-4S / 57-4L | 1,015 mm | 368 mm | 12.5 kN | 140 kV | 110 kV | 230 kV | 340 kV | 16.0 kg |
| 57-5S / 57-5L | 1,145 mm | 438 mm | 12.5 kN | 160 kV | 130 kV | 265 kV | 380 kV | 18.0 kg |
| 57-6S / 57-6L | 1,364 mm | 489 mm | 12.5 kN | 180 kV | 150 kV | 300 kV | — | 20.5 kg |
Clamp Top Series (57-11 to 57-16 / 57-21 to 57-26)
| Class | Creepage | Dry Arc | M&E | Dry FO | Wet FO | Impulse+ | Weight |
|---|---|---|---|---|---|---|---|
| 57-11 / 57-21 | 356 mm | 165 mm | 12.5 kN | 70 kV | 50 kV | 120 kV | 6.8 / 7.5 kg |
| 57-12 / 57-22 | 559 mm | 241 mm | 12.5 kN | 100 kV | 70 kV | 160 kV | 10.0 / 10.5 kg |
| 57-13 / 57-23 | 737 mm | 311 mm | 12.5 kN | 125 kV | 95 kV | 200 kV | 11.8 / 12.7 kg |
| 57-14 / 57-24 | 1,015 mm | 368 mm | 12.5 kN | 140 kV | 110 kV | 230 kV | 15.9 / 16.8 kg |
| 57-15 / 57-25 | 1,145 mm | 438 mm | 12.5 kN | 160 kV | 130 kV | 265 kV | 18.6 / 19.5 kg |
| 57-16 / 57-26 | 1,346 mm | 489 mm | 12.5 kN | 180 kV | 140 kV | 300 kV | — / — |
Gain Base Series (57-31 to 57-36)
| Class | Creepage | M&E | Dry FO | Wet FO | Weight |
|---|---|---|---|---|---|
| 57-31 | 256 mm | 12.5 kN | 70 kV | 50 kV | 9.5 kg |
| 57-32 | 559 mm | 12.5 kN | 100 kV | 70 kV | 12.5 kg |
| 57-33 | 737 mm | 12.5 kN | 125 kV | 95 kV | 15.7 kg |
| 57-34 | 1,016 mm | 12.5 kN | 140 kV | 110 kV | 18.8 kg |
| 57-35 | 1,143 mm | 12.5 kN | 160 kV | 130 kV | 21.5 kg |
| 57-36 | 1,800 mm | 12.5 kN | — | — | — |
※ 57-36: Dry flashover, wet flashover and weight data subject to project-specific confirmation. Contact our engineers for GA drawing review and detailed specifications.
IEC 60383 / AS 2947.2 — Representative Models
| Model | Standard | Min Leakage | Cantilever | Wet (kV) | Lightning (kV) | Weight |
|---|---|---|---|---|---|---|
| 11005 | IEC 60383 | 530 mm | 12.5 kN | 50 | 150 | 9.8 kg |
| 11006 | IEC 60383 | 500 mm | 12.5 kN | 65 | 150 | 9.4 kg |
| 11002 | AS 2947.2 | 565 mm | 12.5 kN | 50 | 150 | 7.5 kg |
| 11007 | IEC 60383 | 610 mm | 12.5 kN | 50 | 150 | 13.3 kg |
Also manufactured to DIN and SA standards. Contact us for specific standard requirements and custom configurations.
Where Line Post Insulators Are Used
Distribution Lines
11 kV – 33 kV overhead distribution networks. Urban, suburban, and rural electrification. The most common application for ANSI 57-1 and 57-2 classes.
Sub-Transmission
34.5 kV – 69 kV sub-transmission lines connecting substations to distribution networks. Typically ANSI 57-3 to 57-6 with extended creepage for pollution zones.
Rural Electrification
Long-span rural lines where reliable, low-maintenance insulators are critical. Gain base mounting (57-31 to 57-36) eliminates crossarm cost on compact pole-top designs.
Line Post Insulator FAQ
Tie top insulators use wire ties to secure the conductor in a top groove — this is the traditional method used by most utilities. Clamp top insulators use a metal clamp bolted on top, providing higher mechanical security and reducing maintenance labor. Both configurations have identical electrical ratings for the same ANSI class number. The choice depends on your utility's installation practices and maintenance preferences.
For a 34.5 kV system, ANSI Class 57-3 is the minimum requirement (95 kV wet flashover, 737 mm creepage). However, in polluted environments — coastal, industrial, or desert — you should specify Class 57-4 (110 kV wet flashover, 1,015 mm creepage) to ensure adequate pollution performance. The rule of thumb: your wet flashover voltage should be at least 2× your maximum phase-to-ground operating voltage.
Yes. While standard ANSI 57 classes have fixed creepage distances, our production base can manufacture custom creepage configurations for specific pollution severity requirements. Provide your IEC 60815 pollution level classification and required creepage ratio (mm/kV), and our engineers will recommend the optimal design. Custom creepage may require minimum order quantities.
Standard configurations: 8–12 weeks from order confirmation and drawing approval. For urgent EPC projects, expedited scheduling may be available depending on current production capacity. Lead time is always confirmed before order placement — no surprises.
Yes. ANSI C29.7 type-test reports are available for all 57 series classes. Our line post series has been independently type-tested by KEMA (Netherlands). Additionally, every shipment includes routine test reports — 100% ultrasonic tested — along with material traceability certificates and dimensional inspection records. Third-party inspection is welcome at any stage of production.
Get a Technical Proposal for Line Post Insulators
Specify your ANSI class, quantity, and mounting type. Our engineers respond within 6 hours with pricing, lead time, and applicable test reports.