H1: ANSI 55 Series Insulators – 55‑1 to 55‑6 for Low to Medium Voltage Distribution Networks

The ANSI 55 Series Insulators C29.5 comprises six classes of wet‑process porcelain pin‑type insulators – 55‑1, 55‑2, 55‑3, 55‑4, 55‑5, and 55‑6 – specifically engineered for low to medium‑voltage overhead distribution lines operating at 3 kV to 23 kV. Manufactured in full compliance with ANSI/NEMA C29.5 standards, these insulators offer progressively increasing creepage distances (from 102 mm to 381 mm) and flashover voltages to match light to moderate pollution environments. Whether installed in urban distribution networks, rural electrification projects, or industrial areas, the 55 Series delivers reliable electrical insulation, robust mechanical strength, and long service life. Their standardized pin‑type design ensures easy replacement and compatibility with existing ANSI Class 55 hardware.

H2: ANSI 55 Series Insulators Technical Specifications (55‑1 to 55‑6)

The following table summarizes all key dimensional, electrical, and mechanical parameters for each class. All values are verified per ANSI/NEMA C29.5‑2022.

Parameter	Unit	55-1	55-2	55-3	55-4	55-5	55-6
ANSI Class	—	55-1	55-2	55-3	55-4	55-5	55-6
Fig. No.	—	1	2	3	4	4	—
Diameter (D)	mm (in)	82.6 (3.25)	95.3 (3.75)	120.7 (4.75)	140 (5.5)	177.8 (7.0)	213 (8.38)
Height (H)	mm (in)	89 (3.5)	82.6 (3.25)	95.3 (3.75)	111.2 (4.38)	123.9 (4.88)	140 (5.5)
Spacing (h)	mm (in)	44.5 (1.75)	38.1 (1.5)	38.1 (1.5)	44.5 (1.75)	50.8 (2.0)	57 (2.25)
Pin Diameter (d)	mm (in)	25.4 (1.0)	25.4 (1.0)	25.4 (1.0)	25.4 (1.0)	25.4 (1.0)	25.4 (1.0)
Saddle Groove Radius (R1)	mm	—	16	14.3	25.4	25.4	—
Wire Groove Radius (R2)	mm	13	16	14.3	14.3	14.3	—
Neck Type	—	—	C	C	F	F	J
Creepage / Leakage Distance	mm (in)	102 (4.0)	127 (5.0)	178 (7.0)	229 (9.0)	305 (12.0)	381 (15.0)
Dry Arcing Distance	mm (in)	57 (2.25)	86 (3.38)	114 (4.5)	127 (5.0)	159 (6.25)	203 (8.0)
Min. Pin Length	mm (in)	102 (4.0)	102 (4.0)	127 (5.0)	127 (5.0)	152 (6.0)	190 (7.5)
Application Voltage	kV	3	7.2	11.5	13.2	14.4	23
Cantilever / M&E Strength	kN (lb)	13 (3,000)	11 (2,500)	11 (2,500)	13 (3,000)	13 (3,000)	13.3 (3,000)
Power Freq. – Dry Flashover	kV	35	45	55	65	80	100
Power Freq. – Wet Flashover	kV	20	25	30	35	45	50
Critical Impulse Flashover (+)	kV	50	70	90	105	130	150
Critical Impulse Flashover (–)	kV	70	85	110	130	150	170
Power Frequency Puncture Voltage	kV	50	70	90	95	115	135
RIV Test Voltage (to ground)	kV	5	5	10	10	15	22
Max. RIV at 1,000 kHz	μV	50	50	50	50	100	100
Net Weight (approx.)	kg (lb)	0.5 (1.1)	0.75 (1.65)	1.1 (2.4)	1.7 (3.7)	2.9 (6.4)	4.1–4.4 (9.0–9.7)

H2: ANSI 55 Series Insulators Material & Construction

Every insulator in the ANSI 55 Series is manufactured from high‑grade electrical porcelain using the wet‑process method, fired at high temperatures to ensure maximum density, mechanical strength, and near‑zero porosity. The porcelain body is protected by a smooth, hard‑glaze coating (available in brown or grey) that provides excellent self‑cleaning properties and resistance to tracking. The galvanized steel pin and hardware are hot‑dip galvanized for superior corrosion resistance, ensuring a service life exceeding 40 years under normal conditions. All metal parts are securely cemented with high‑quality Portland cement, providing stable performance under extreme temperature cycling and mechanical vibration. For more on porcelain manufacturing standards, visit the International Electrotechnical Commission (IEC).

H2: ANSI 55 Series Insulators Applications & Installation

The 55 Series pin‑type insulators are the preferred choice for:

Low to medium voltage overhead distribution lines (3 kV, 7.2 kV, 11.5 kV, 13.2 kV, 14.4 kV, and 23 kV systems)
Urban and rural network extensions
Substation bus supports and riser poles
Industrial power distribution where reliable insulation is essential
Light to moderate pollution areas requiring standard leakage paths

Installation is straightforward: the insulator is mounted on a steel or wooden pole pin using the standard threaded pin (d = 25.4 mm / 1.0 inch). The top groove accommodates the conductor, which is secured with a tie wire or clamp. Standard dimensions ensure full interchangeability with existing ANSI Class 55 hardware. For live‑line maintenance, hot‑stick‑compatible designs are available upon request. Explore our full range of suspension insulators and transmission hardware for more options.

H2: ANSI 55 Series Insulators Quality & Performance Advantages

Progressive Creepage Distance – The stepwise increase from 102 mm to 381 mm allows precise matching to site pollution levels, reducing the risk of flashover and leakage current.
Superior Flashover Resilience – Dry flashover voltage ranges from 35 kV to 100 kV, and wet flashover from 20 kV to 50 kV, ensuring stable operation under rain, fog, and dew conditions.
High Impulse Withstand – Negative‑polarity critical impulse flashover reaches up to 170 kV (55‑6), protecting against lightning surges and switching transients.
Robust Mechanical Strength – Cantilever strength ranges from 11 kN to 13.3 kN across the series, providing reliable performance under wind, ice, and conductor tension.
Controlled Radio Interference – RIV values are strictly controlled at 50–100 µV at 1,000 kHz, meeting stringent electromagnetic compatibility (EMC) requirements for communication‑sensitive corridors.

Each insulator undergoes 100% routine electrical and mechanical testing – including visual inspection, dimensional checks, cantilever load tests, and high‑voltage withstand tests – before dispatch. Prototype tests per ANSI/NEMA C29.5 cover temperature cycling, thermal‑mechanical performance, and radio influence voltage. Full test reports and batch traceability are provided. Full testing procedures are detailed in ANSI C29.5, published by NEMA.

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 installation guidance, refer to our insulator string assembly guide.

H2: ANSI 55 Series Insulators Selection Recommendations

Application Environment	Recommended Model(s)	Key Selection Criteria
Low voltage distribution (3 kV)	55-1	Compact size (83 mm diameter), 102 mm creepage, lightweight (0.5 kg)
Medium voltage (7.2 kV)	55-2	127 mm creepage, 11 kN strength, economical
Medium voltage (11.5 kV)	55-3	178 mm creepage, 55 kV dry flashover
Medium voltage (13.2 kV)	55-4	229 mm creepage, 65 kV dry flashover
Medium voltage (14.4 kV)	55-5	305mm creepage, 80kV dry flashover
Higher voltage (23 kV) / moderate pollution	55-6	381mm creepage, 100kV dry flashover, 50kV wet flashover, 170 kV negative impulse withstand
High mechanical load applications	55-1, 55-4, 55-5, 55-6	13–13.3kN cantilever strength for maximum reliability

For detailed datasheets, CAD drawings, or competitive pricing on any ANSI 55 Series Insulator, please contact our sales team via the inquiry form below. We also offer OEM services and free technical consultation for distribution line design.

References & Authoritative Resources

For detailed certification, standard compliance, and procurement specifications, please refer to the following sources:

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 line applications.
👉 Suspension Insulators Collection
NEMA Standards – Official publications covering ANSI C29.5 and C29.6 insulator 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 pin‑type classes (e.g., 55‑7), please consult the ANSI/NEMA C29.5 standard document or contact your engineering representative with the above specification table.