High voltage composite insulator adopts large-small umbrella structure (large-small-large) to improve its wet-dirt-resistant ability.


Excellent bird-prevention and induction circular tube type grading ring structure could effectively prevent flashover by birds’ droppings.


Integrated half-round grading ring structure


Direct current product end fitting sealing structure


Alternating current product end fitting sealing structure

Raw Material Quality Process Control

Testing basis

  • ISO 37: 2005 Rubber.vulcanized or thermoplastic-Determination of tensile stress-strain properties
  • ISO 34-1 :2004 Rubber.vulcanized or thermoplastic-Determination of tear strength-Part1: Trouser.angle and crescent test pieces
  • ISO 7619-1 :2004 Rubber.vulcanized or thermoplastic-Determination of indentation hardness­Part1 :Duromerer method(Shore hardness)
  • ISO 4892-2:2006 Plastics-Methods of exposure to laboratory light sources-Part 2:Xenon-arc sources
  • IEC 60587:2007 Electrical insulating materials used under severe ambient conditions-Test methods for evaluating resistance to tracking and erosion
  • IEC 60695-11-10:2003 Fire hazard testing-Part 11-1 0:Test flames-50W horizontal and vertical flame test methods
  • IEC 60243-1: 1998 Electrical strength of insulating materials-Test methods-Part1 :Tests at power frequencies
  • IEC/TS 62073:2003 Guidance on the measurement of wettability of insulator surfces
  • IEC 60120: 1984 Ball and socket coupling dimensions of string insulator units
  • IEC 60372:1984/AM2:2003 locking deviceof s for ball and socket couplings of string insulator units-Dimensions and tests
Physics-Chemistry Laboratories

Based on the requirement of experiment and test in overall production, the company sets physical and chemical properties testing room of silicone rubber, mandril, metal fitting and so on, as well as electrical performance testing room which is equipped with relative facilities and testing methods. Testing room has gone through strict certification of National Quality Supervision and Meteorological Service Department, fully satisfying and guaranteeing requirements of product quality test, and can test on time, rapidly and accurately.

Vulcanized Rubber Property Test

Hardness test


Shore hardness is no less than 50ShoreA: variation of hardness before and after boiling should not exceed 10%.

Tensile strength test


Mechanical breaking strength is no less than 4 MPa; elongation at break should be no less than 150%.

Burning Test


Adopt vertical burning method, flammability is FV-0 level.

Puncture Test


AC breakdown strength is no less than 20kV/mm, DC is no less than 30kV/mm.

Split strength test


Tearing strength is no less than 10kN/m

Formulation optimization test


Research sizing formula and process of different voltage products and continuously optimizing to satisfy customers’ requirements of product quality.

Volume Surface resistivity test


Volume resistivity and surface resistivity are no less than 1.0 x 1012 Ω • m

1000h UV test


After test, marks on umbrella or cover should be clear to distinguish from, surface degradation is not allowed, such as cracking and surface bulging.

Anti-tracking Test


Anti-tracking and anti-electrical-erosion is no less than TMA4.5 level.

Formulation optimization test


Hydrophobic test mainly include product classification (HCl – HC6 level I , measurement of dip angle, transfer of hydrophobicity, loss and recovery. Hydrophobicity of outgoing product should reach above HC2 level.

Mandril Property Test

Stress-corrosion-resistant Test


Put on the larger one of 67%SML and 300MPa on mandril, add 1 N concentration of nitric acid in acid containers immediately for 96h. The test is qualified if no breakdown occurred within 96h.

Power-frequency voltage-withstand Test


Put 80% dry power frequency flashover voltage on sample for 30min, no breakdown or surface flashover should happen.

Current Leakage Test


No breakdown or surface flashover should happen, current should not exceed 50uA.

Dye Penetration Test


The time of penetration should exceed 15min.

Photo-permeability Inspection by Each


To remove internal flaws such as impurity, bubble, cracking and so on.

Fittings Test

Zn-coat thickness test


Test ten points on sample, the single minimum ≥ 80um, single mean value≥120um, overall mean value ≥ 85um.

Fitting hardness test


Variation of each batch welding zone should be no longer than +20HBS

Size check


Size, form and location tolerance conform to regulations of figure sample.

No-go gauge test


Socket and foot should pass measurement of corresponding check gauge measuring tool.

Mechanical tensile strength test


Tensile failing load should be no less than 1.5 times of SML (specified mechanical load).

Fitting Pin Test


Run three operational load test on samples, rich value F should be between Fmin50N and Fmax500N.

Advanced Production Technology and Equipment


Adopt new-type full-automatic 550T cylinder injection machine and 1200T large-volume injection machine, for injection moulding and firm sticking many groups of umbrella covers and mandrils at one time, promoting its security.

Adopt domestic 6000kN large diameter clearance displacement pressure welding machine and B000kN Germany-imported press-connection machine insulator metal fittings.

Rubber injection molding machine with volume of 3000CC-15000CC, for various types of insulators for line , power plant.

Uniflex press-connection machine


Average-allocated stress without hurting integrity of mandril glass fiber bundles, able to fully play its advantage in tensile strength, equipped with “acoustic emission detection system” to detect its stability and guarantee a stable intensity and safe, reliable connection of metal fittings.

AT-550L full automatic silicon rubber injection moldlng machine


Put 80% dry power frequency flashover voltage on sample for 30min, no breakdown or surface flashover should happen.

C-type injection molding machine


Inject composite insulator large umbrella skirt for creepage and anti-icing.

Tongchun JY-6000C press-connection machine


Adopt amount and pressure to control quality together, highest pressure limit and lowest limit could effectively prevent over-voltage and under-voltage, there is a small mechanical strain discrete value.

Key Process Control of Production Area

There is one key control of production process: mandril assembly and two special processes: silicone rubber mixing and vulcanization molding. Advanced supervision system and equipment are equipped to supervise product quality.

Adopt vulkameter to test stability of silicon rubber vulcanization curve; ultrasonic nondestructive thickness gauge to inspect uniformity of sheath thickness; tension test for stability of product mechanical strength.

Use vulkameter to test refining gum quality


Run the test of vulcanization curve on produced mixing refining gum to obtain correct vulcanizing time directly, so as to regulate surtable time for production line and verify its craft to guarantee product quality.

Use thickness gauge to inspect uniformity of sheath thickness


To test thickness of gauge more conveniently, uniformity of rapidly. To keep a uniform thickness with conformation of standard requirement.

Tension sampling test


The method is to run a 50% mechanical load test for 10s on each product in outgoing test to test its mechanical ability and conform a steady mechanical ability of each product.

Appearance test


Overall surface flaw area should not exceed 0.2% of total area. There shouldn’t be any of the following flaw:

1) single umbrella surface is larger than 25 square mm or its deeper is larger than 1 mm;

2)there is cracking at the root of umbrella, especially the ones close to end facilities;

3) separate or not firmly stick between coat and end facilities;

4) separate or not firmly stick between umbrella and sheath;

5) there is molding distance over 1 mm on the surface of coat.

Product Quality Control

Chief test basis

IEC 61109:2008 Insulators for overhead lines-Composite suspension and tension insulators for with a nominal voltage greater than 1 000 V-Definitions, test methods and acceptance criteria.

There are advanced facilities in high voltage laboratory, able to carry out design experiment, molding experiment as GB standard, IEC standard or customer requirement, able to fully satisfy inspection requirements of the third-party sampling test. power frequency equipment, steep waving equipment, water boiling, tensile machine

Water boiling experiment tank


Able to boil deionized water with 0.1 %(weight) NaCl for 41 h to run water dipping pre-stressed test.


Power frequency testing equipment


Power frequency testing transformer runs power frequency testing on each mandril to test its electric insulation performance more strictly.

2000kN ZTW


Able to satisfy test of composite insulator design test. type test, sampling test and mechanical load property test by each.

Steep wave generator


Steep wave generator impacts sect on of products with positive and negative polarity for 25 times each with steepness no less than 1000kV/us, running a more strict electrical performance test on outgoing product to guarantee a definitely safe and reliable insulation property.

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