H1: ANSI 57 Series Insulators Complete Guide for 57‑1 to 57‑6 Line Post Porcelain Insulators (11 kV – 69 kV)
ANSI 57 series insulator products are six classes of wet‑process porcelain line post insulators – 57‑1, 57‑2, 57‑3, 57‑4, 57‑5, and 57‑6 – engineered for overhead transmission and distribution lines from 11 kV to 69 kV.
Manufactured to ANSI C29.7 standards, these ANSI 57 series insulator units feature solid‑core construction with creepage distances ranging from 356 mm (57‑1) to 1,364 mm (57‑6), providing reliable performance from light to heavy pollution environments.
Available in Tie‑Top and Line Post styles, with long‑stud (L) and short‑stud (S) options, the ANSI 57 series insulator family is widely used across North American and ANSI‑adopting grids.
Whether for substation bus supports, rural distribution, or industrial power systems, this ANSI 57 series insulator range delivers consistent electrical insulation, mechanical robustness, and decades of service life.
H2: ANSI 57 Series Insulators Technical Specifications (57‑1 to 57‑6)
The table below compiles all key dimensional, electrical, and mechanical parameters for each ANSI 57 series insulator class, based on manufacturer datasheets and ANSI/NEMA C29.7.
| Parameter | Unit | 57‑1 | 57‑2 | 57‑3 | 57‑4 | 57‑5 | 57‑6 |
| ANSI Class | — | 57‑1 | 57‑2 | 57‑3 | 57‑4 | 57‑5 | 57‑6 |
| Figure No. | — | 1 | 2 | 3 | 4 | 5 | 6 |
| With Long Stud | — | 57‑1L | 57‑2L | 57‑3L | 57‑4L | 57‑5L | 57‑6L |
| With Short Stud | — | 57‑1S | 57‑2S | 57‑3S | 57‑4S | 57‑5S | 57‑6S |
| Creepage / Leakage Distance | mm | 356 | 559 | 737 | 1015 | 1145 | 1364 |
| Dry Arcing Distance | mm | 165 | 241 | 311 | 368 | 438 | 489 |
| Cantilever Strength | kN | 12.5 | 12.5 | 12.5 | 12.5 | 12.5 | 12.5 |
| Power Freq. – Dry Flashover | kV | 70 | 100 | 125 | 140 | 160 | 180 |
| Power Freq. – Wet Flashover | kV | 50 | 70 | 95 | 110 | 130 | 150 |
| Critical Impulse Flashover (+) | kV | 120 | 160 | 200 | 230 | 265 | 300 |
| Critical Impulse Flashover (‑) | kV | 155 | 205 | 260 | 340 | 380 | — |
| RIV Test Voltage (to ground) | kV | 15 | 22 | 30 | 44 | 44 | 44 |
| Max. RIV at 1,000 kHz | μV | 100 | 100 | 200 | 200 | 200 | 200 |
| Net Weight | kg | 5 | 9.8 | 12 | 16 | 18 | 20.5 |
All models: Standard ANSI C29.7 · Solid core wet‑process porcelain · Glaze: Brown / Grey
Source: Manufacturer catalogue
H2: ANSI 57 Series Insulators Material & Construction
Every ANSI 57 series insulator is produced from high‑grade electrical porcelain using the wet‑process method, fired at high temperatures to achieve maximum density, mechanical strength, and near‑zero porosity.
The body is coated with a smooth, hard glaze (brown or grey) that provides excellent self‑cleaning properties, tracking resistance, and erosion resistance. The solid‑core design ensures stable performance under extreme temperature cycling and vibration.
Metal fittings are made of malleable iron, ductile iron, or steel, with ferrous components hot‑dip galvanized per ASTM A153. The ANSI 57 series insulator operates reliably in high‑voltage environments and harsh climates, including high altitudes and heavy‑pollution areas.
For more on porcelain manufacturing standards, visit the International Electrotechnical Commission (IEC).
H2: ANSI 57 Series Insulators Applications & Installation
The ANSI 57 series insulator is the preferred choice for:
High‑voltage overhead transmission lines (11 kV to 69 kV)
Urban and rural distribution networks
Substation bus supports and riser poles
Industrial power distribution requiring dependable insulation
Heavy‑pollution areas (coastal, industrial, desert) needing extended leakage paths
Two stud configurations are available:
Long Stud (L) – for extra mounting height
Short Stud (S) – for compact installations with standard clearance
Installation is simple: mount the insulator on a support structure using the standard stud base. Standardized dimensions ensure full interchangeability with existing ANSI Class 57 hardware. Hot‑stick‑compatible designs for live‑line maintenance are available on request.
Explore our full range of suspension insulators and transmission hardware for more options.
H2: ANSI 57 Series Insulators Quality & Performance Advantages
Progressive creepage distance – from 356 mm to 1,364 mm, allowing precise matching to site pollution levels and reducing flashover risk.
Superior flashover resilience – dry flashover 70‑180 kV, wet flashover 50‑150 kV, ensuring stable operation in rain, fog, and dew.
High impulse withstand – positive‑polarity critical impulse flashover up to 300 kV (57‑6), protecting against lightning and switching surges.
Consistent mechanical strength – all models share a uniform 12.5 kN cantilever strength, performing reliably under wind, ice, and conductor tension.
Controlled radio interference – RIV values strictly maintained at 100‑200 μV at 1,000 kHz, meeting stringent EMC requirements.
Long service life – porcelain resists UV, bird pecking, and scratches, with a service life exceeding 40 years under normal conditions.
Each ANSI 57 series insulator undergoes 100% routine electrical and mechanical testing – visual inspection, dimensional checks, cantilever load tests, and high‑voltage withstand tests.
Design tests per ANSI C29.7 cover dry/wet flashover, critical impulse flashover, radio influence voltage, and thermal‑mechanical performance. Full test reports and batch traceability are provided. Testing procedures are detailed in ANSI C29.7, published by NEMA.
Packaging: each unit is individually packed with foam cushioning and secured in sturdy wooden crates or corrugated cartons. Flexible shipping options (FOB, CIF, EXW) with lead times of 15‑30 days.
For installation guidance, refer to our insulator string assembly guide.
H2: ANSI 57 Series Insulators Selection Recommendations
| Application Environment | Recommended Model(s) | Key Selection Criteria |
| Medium voltage distribution (11 kV) | 57‑1 | 356 mm creepage, 70 kV dry flashover, lightweight (5.0 kg) |
| Medium voltage (15‑24 kV) | 57‑2 | 559 mm creepage, 100 kV dry flashover, 9.8 kg |
| Medium voltage (24‑34.5 kV) | 57‑3 | 737 mm creepage, 125 kV dry flashover, 12.0 kg |
| High voltage (34.5‑46 kV) | 57‑4 | 1,015 mm creepage, 140 kV dry flashover, 16.0 kg |
| High voltage (46‑69 kV) | 57‑5 | 1,145 mm creepage, 160 kV dry flashover, 18.0 kg |
| Extra‑high voltage / severe pollution | 57‑6 | 1,364 mm creepage, 180 kV dry flashover, max impulse 300 kV, 20.5 kg |
For detailed datasheets, CAD drawings, or competitive pricing on any ANSI 57 series insulator, please contact our sales team via the inquiry form below. We also offer OEM services and free technical consultation for transmission line design.
H2: ANSI 57 Series Insulators References & Authoritative Resources
For certification, standard compliance, and procurement specifications, refer to:
- International Electrotechnical Commission (IEC) – global standards for electrical insulators and porcelain manufacturing.
👉 IEC Homepage - Full Range of Suspension Insulators – explore our complete product portfolio for transmission and distribution lines.
👉 Suspension Insulators Collection - NEMA Standards – official publications covering ANSI C29.7 and related specifications.
👉 NEMA Store - Insulator String Assembly Guide – installation best practices, string design, and torque specifications.
👉 Assembly Guide
For project‑specific inquiries or cross‑referencing to other ANSI line post classes, consult the ANSI/NEMA C29.7 standard document or contact your engineering representative with the above specification table.
