Composite Insulator Type Tests & Verified Ratings: FXBW 10-110 kV (XIHARI Reports)

When a utility or EPC engineer specifies a composite insulator, the single most important document behind the procurement is the type-test report. It is the independent proof that the insulator will survive its mechanical load, withstand the system overvoltages, and keep its pollution performance for 25-30 years. This article walks through what XinNeng’s XIHARI type-test reports actually verify, and lists the as-tested ratings for the FXBW suspension-insulator family from 10 kV to 110 kV.

1. Why the Type-Test Report Is the Buying Decision

Composite insulators look similar on a warehouse shelf. What separates a 30-year service life from a 5-year failure is invisible: the crimp quality, the core/housing bond, the hydrophobicity of the silicone rubber. The type-test report is the only independent evidence that those hidden properties meet the standard. For a procurement specification, the report is not a nice-to-have — it is the acceptance criterion.

XinNeng commissions its type tests at XIHARI (Xi’an High Voltage Apparatus Research Institute), a nationally recognised high-voltage laboratory in China. Every report in this batch carries the laboratory stamp and the signature block of the editors, checkers and approvers required for validity.

2. The FXBW Family: Verified Ratings (10-110 kV)

The following ratings are quoted directly from the XIHARI prototype/type-test reports for the FXBW series, client XinNeng High Voltage Electric Co., Ltd. All values are the specified (design) ratings confirmed by test, not catalogue marketing figures.

Two facts stand out. First, the 120 kN SML is common across the whole family, so the same mechanical interface and crimp design is proven from 10 kV to 110 kV. Second, the wet power-frequency withstand is the value that tracks pollution and ageing performance — it more than quintuples across the range because the shed profile and creepage are redesigned for each voltage class.

3. How to Read Each Test in the Report

• Visual examination & markings (routine). Every unit is marked with manufacturer, year of manufacture, SML and rated voltage; markings must be legible and indelible.
• Tensile load test (routine). A 60 kN tensile load is held for 10 s on every specimen — exactly half the 120 kN SML, the standard routine margin.
• Verification of SML (type). Specimens are loaded to 120 kN; the report records no damage and the failing-load test (cap/pull-out) confirms the connection design.
• Dry lightning-impulse withstand, LIWV (type). 15 positive + 15 negative impulses at the specified level (e.g. 75 kV for 10 kV class, 550 kV for 110 kV class) with no flashover.
• Wet power-frequency withstand (type). Applied at the specified kV (e.g. 42 kV / 230 kV) for 60 s under simulated rain; no flashover is the pass criterion.
• Radio-interference voltage, RIV (type). Measured at 1 MHz; the 10 kV class reports RIV well under the 500 µV limit, confirming a clean end-fitting/housing interface.
• Damage-limit proof & interface tightness (type). A 84 kN tensile load (1 min) plus a 96 h long-time load at 84 kN, with a dye-penetration check of the end-fitting/housing seal showing no ingress.

4. Creepage Distance and Pollution Class

Withstand voltage alone does not size an insulator for a site — creepage distance does. Creepage is the leakage-path length along the shed surfaces, and it is selected from the site pollution severity (SPS) class in IEC 60815-1/2/3: light, medium, heavy and very heavy. The 10 kV class report records a 365 mm creepage on the tested sample; for higher pollution classes the same mechanical design is offered with an extended shed profile and longer creepage.

A common specification error is to quote only the rated voltage and forget the pollution class. Two insulators with the same kV rating but different creepage can have wildly different service lives in a coastal or industrial environment. Always state the SPS class when you request a quotation.

5. Beyond 110 kV: 330 kV and the Verification Flag

The same caution applies to every rating that originates from a scanned, non-text PDF in this batch: it is flagged, never silently inserted. The verified tables above come only from text-searchable reports.

6. Standards That Govern the Tests

7. Procurement Checklist

1. Confirm a valid type-test report exists for the exact model and SML you are buying (e.g. FXBW-110/120, 120 kN).
2. Check the housing material is HTV silicone rubber and the end fittings are crimped with a sealed interface.
3. State the site pollution severity class so the supplier selects the correct creepage distance.
4. Verify the report is issued by a recognised laboratory (XIHARI in this case) with stamp and signatures.
5. Ask for the routine-test certificate per batch — tensile load at 60 kN for 10 s and visual/marking checks.

Frequently Asked Questions

What is the difference between a type test and a routine test?

A type test is performed once on a representative specimen to qualify a design; a routine test is applied to 100% of the units leaving the factory. In the FXBW reports the routine tensile load is 60 kN for 10 s — half of the 120 kN specified mechanical load — plus visual and marking checks on every unit.

What does SML 120 kN mean in practice?

SML (specified mechanical load) is the tensile load the insulator is type-tested to carry without damage. Utilities do not operate at SML; working tension is typically a fraction of it, with the routine test run at 50% of SML as the factory acceptance margin.

Are GB/T 19519 and IEC 61109 the same standard?

Effectively yes for procurement purposes. GB/T 19519-2014 is the Chinese standard modified from IEC 61109:2008, and the XIHARI type-test reports for this FXBW family are issued against it. Specifying either reference covers the same mechanical, electrical and interface test programme.

Why is wet power-frequency withstand the number to watch?

Because it exercises the silicone housing surface under simulated rain — the closest factory simulation of polluted, wet service conditions. Across the family it rises from 42 kV (10 kV class) to 230 kV (110 kV class), and it is the value most sensitive to housing quality and shed design.

How do I size the creepage distance for my site?

State the site pollution severity (SPS) class from IEC 60815 when you request a quotation. The tested 10 kV sample carried a 365 mm creepage; heavier pollution classes are served by the same mechanical design with an extended shed profile and longer creepage.

Summary

• Pain point: composite insulators look identical but perform very differently; the type-test report is the only independent proof of the hidden properties.
• Verified data: FXBW 10/24/35/66/110 kV all carry a 120 kN SML, with dry LIWV from 75 kV to 550 kV and wet PF withstand from 42 kV to 230 kV, tested to GB/T 19519-2014 at XIHARI.
• Creepage: selected per IEC 60815 pollution class; the 10 kV sample measured 365 mm.
• Verification flag: the 330 kV long-rod ratings are type-tested but come from a scanned certificate and must be confirmed visually before publication.
• Action: buy against the report, not the brochure — confirm model, SML, pollution class and laboratory stamp.