Selecting Insulators for Polluted Environments: Utility Perspective -

Past technical recommendations such as IEC/TR as well as newer specifications such as IEC/TS are both used by power utilities for insulator selection in polluted outdoor environments.

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This edited contribution to INMR by Dr. Wallace Vosloo, retired from Eskom, Richardo Davey of Eskom Research Testing and Johannes Bekker at the University of Stellenbosch in South Africa reviewed different possible approaches in this regard.

Using IEC/TR 

Selecting porcelain and glass insulators for three-phase a.c. systems up to 525 kV phase-to-phase using IEC/TR (Guide for the selection of insulators in respect of polluted conditions) has been based on service experience as well as laboratory testing under naturally and artificially polluted conditions. As stated in this document: Simple general rules should assist choosing the insulator, which should give satisfactory performance under polluted conditions.

Although it is advised to determine pollution type and severity and then use laboratory tests to help select insulators, many utilities have instead simply chosen to standardize on one or more values of minimum Specific Creepage Distance. Here, SCD (the ratio of the leakage distance measured between phase and earth over the r.m.s. phase to phase value of the highest voltage for the equipment) is recommended for various pollution levels (I to IV), namely 16, 20, 25 and 31 mm/kV(Um) respectively for Light, Medium, Heavy and Very Heavy pollution environments. Pollution levels I to IV are determined mainly from IEC/TR Tables (shown in Fig. 1), service experience or by doing site pollution severity (SPS) measurements using Equivalent Salt Deposit Density (ESDD) or Directional Dust Deposit Gauges (DDDG) methods. Table 1 shows typical ESDD and DDDG values used to classify site pollution level and minimum required SCD.

Fig. 2 and Table 2 summarize basic profiling rules recommended in IEC/TR , which are normally followed.

Influence of insulator diameter on pollution performance is also considered for insulators with average diameters of between 300 and 500 mm. In the case of diameters greater than 500 mm, it is recommended that specific creepage distances be increased by 10% and 20%. Laboratory tests, in accordance with IEC 507, are also recommended to evaluate an insulator’s pollution performance but are rarely used by most power utilities. Greasing or washing is recommended for areas with severe pollution and/or low natural washing.

For a.c. porcelain and glass insulators, a utility would typically specify maximum connection length taking into account live line work, minimum dry arcing distance, and minimum creepage distance. Then, it would be stated that insulator profile must comply with IEC/TR , the focus being on simplicity and ease of use.

Case Study Using IEC/TR for Selecting Insulators

It is proposed to erect 132 kV lines in areas with pollution levels ranging from Light to Very Heavy using standard glass cap & pin disc insulators (U120B, F12/146). Assuming the parameters given below, how many discs (n) would be required per string?

System highest voltage (Um) = 145 kV

Minimum required Dry Arcing Distance (DAD) of the insulator string is  mm (i.e. for a high lightning area)

Disc spacing (s) = 146 mm

Arcing distance per disc (a) = 210 mm

Creepage distance (CD) per disc = 320 mm

The arcing distance of a disc insulator string = a + (n – 1) s

Thus, = 210 + (n – 1) x 146 and n = ( – 210) / 146 + 1 = 9.84 (in other words, 10 discs are required)

In terms of pollution level, as shown in Table 1, the specific creepage distances needed for Light, Medium, Heavy and Very Heavy pollution areas are 16, 20, 25 and 31 mm/kV (Um) respectively.

Number of discs required per string = (CD)/320 where CD = (Um x SCD)

Table 3 gives values calculated using (145 x SCD)/320.

Utilities have typically been using 7 to 14 standard glass discs per string for 132 kV lines. More recently, with the advent of new ‘active’ polymeric insulation materials that interact with the environment, utilities have continued to use IEC/TR since nothing else was available in IEC.

Typically, for a.c. polymer insulators, utilities such as Eskom would specify maximum connecting length (taking into account live line work), minimum dry arcing distance and minimum creepage distance. They would also state that insulator profile must:

1. comply with IEC/TR based on in-service and test station experience;
2. have open aerodynamic alternating shed profile with S/P ratio ≥ 1; and
3. that the material must be hydrophobic, with good hydrophobicity transfer capabilities.

Then, for e.g. ease of stock, minimum SCDs of 20 mm/kV for Light to Medium and 31 mm/kV for Heavy to Very Heavy pollution areas would be specified.

Insulation requirements for both UHV a.c. and d.c. insulators are more complex and normally determined along with technical experts from manufacturers (mostly members of Cigré WGs).

Using Latest Specification IEC/TS “Selection & Dimensioning of HV Insulators for Polluted Conditions”

The following major changes have been made with respect to IEC/TR :

• Encouraging use of site pollution severity measurements, preferably over at least a year, in order to classify a site instead of the previous qualitative assessment (see below).
• Recognition that ‘solid’ pollution on insulators has two components: one soluble and quantified by ESDD; the other insoluble and quantified by NSDD.
• Recognition that, in some cases, measuring layer conductivity should be used for SPS determination.
• Using results of natural and artificial pollution tests to help with dimensioning and to gain more experience in order to promote future studies to establish a correlation between site and laboratory severities.
• Recognition that creepage length is not always the sole determining parameter.
• Recognizing the influence of other geometry parameters and of the varying importance of parameters according to the size, type and material of insulators.
• Recognition of the varying importance of parameters according to type of pollution.
• Adoption of correction factors to attempt to take into account influence of the above pollution and insulator parameters.

Fig. 3 shows three approaches proposed for selection and dimensioning of insulators.

Fig. 4 provides Eskom’s specifications for determining site pollution severity and pollution performance curves.

Practical Example Using Three Approaches as per IEC/TS for Insulator Selection

It has been proposed to erect a 132 kV substation and interconnecting lines at Koeberg Nuclear Power Station (KNPS) along the South African west coast. The area is approximately 600 m from the coastal high-water mark and is exposed to strong coastal winds, low rainfall and regular salt fog events. The insulators (substation: 189 – posts (4 kN), 294 – hollow cores (average diameter <400 mm), 387 – long rods/strings (120 kN, ball and socket) and lines: 768 – long rods/strings (120 kN, ball and socket)) should have a maximum connecting length of 1.48 ± 0.02 m, minimum insulation length of 1.2 m, minimum dry arcing distance of 1.5 m and minimum specific creepage distance of 31 mm/kV (CD ≥ mm). In addition, insulators with open aerodynamic alternating shed profiles, S/P ratio ≥1, hydrophobic material and good hydrophobicity transfer capabilities are preferred.

The question is what insulation is required to ensure risk of insulator flashover is minimal, with mean time between flashover (MTBF) of at least 50 years?

Approach 1: Use Past Experience

Duinefontein 132 kV Substation (≈600 m from the coastal high-water mark) is situated only ≈1 km from the new proposed 132 kV substation and interconnecting lines area at KNPS.

In , the 60 porcelain station post insulators installed at the Duinefontein Substation that have a specific creepage distance of 32.4 mm/kV were upgraded (along with all other insulation) using room temperature vulcanized silicone rubber coating (RTV SR A). Prior to this upgrade (since washing did not work and greasing had only a 6 to 12 month effective lifespan) the substation experienced flashovers on an annual basis, including the Type B instantaneous event of February . Since the upgrade, no flashovers occurred to date (18 years later), which includes the catastrophic Type B instantaneous pollution event experienced in February . Indeed, the RTV SR A coating still has excellent hydrophobic properties.

Personnel from the KNPS Weather Station (≈250 m from Duinefontein Substation) classify the area as follows:

• Average ambient temperatures between 14° and 20°C (minimum 4°C and maximum 36°C);
• Exposed to strong coastal winds (gusts up to 35 m/s);
• Low rainfall area (≈320 mm per year) with only 3 to 5 rainy days in summer (≈80 mm)
• High humidity levels at night/early morning and regular salt fog events (≈40 per year).

ESDD, NSDD and DDDG pollution measurements at the Duinefontein Substation from March to date, were used to calculate ESDD2% = 0.165 mg/cm2 (STDEV = 0.57), average ratio of NSDD/ESDD = 1.1 and monthly average DDDGave = 382 µS/cm.

The flashover of a bare porcelain 132 kV breaker support insulator (having specific creepage distance 32.4 mm/kV) during the catastrophic Type B instantaneous pollution event experienced in the Cape in Feb was used to estimate minimum uniform pollution present on insulation during this event, namely ESDD = 0.4 mg/cm2 and NSDD = 0.182 mg/cm2. Field experience has shown that, while instantaneous pollution events will not occur annually, it can be conservatively assumed that one event occurs each year.

Pollution levels at Duinefontein Substation are as follows:

Type A:  40 natural pre-deposited pollution events per year with critical wetting (ESDD2% = 0.165 mg/cm2 with STD deviation of 0.57 and ESDD/NSDD ratio = 1.1).

Type B:  One instantaneous conductive fog pollution event per year (ESDD2% = 0.4 mg/cm2 and NSDD = 0.182 mg/cm2).

The SPS levels obtained from ESDD and NSDD measurements at Duinefontein Substation (see Fig 5) classify the area for Type A pollution (E6/7) d – Heavy and Type B (E7) e – Very Heavy. DDDG measurements, after climatic factor correction, classify the area as Very Heavy.

The 60 RTV SR A coated porcelain station post insulators with SCD of 32.4 mm/kV at Duinefontein Substation (≈1 km from the new proposed 132 kV substation and lines area) have provided excellent performance for 18 years. Note: these same 60 bare porcelain station post insulators had flashed over more than once annually.  No washing or greasing was recommended.

Koeberg Insulator Pollution Test Station (KIPTS) (≈50 m from the coastal high-water mark) lies about 2 km from the new proposed 132 kV substation and lines area.  Monthly average DDDGave =  µS/cm measured at KIPTS is Extreme (≈6.6 times higher compared to Duinefontein Substation). Findings of some insulator research and tests done at KIPTS over 15 years are presented in “Power Utility Perspective on Natural Ageing and Pollution Performance Insulator Test Stations”.

From natural insulator pollution performance experience gained at KIPTS the following:

Posts: Porcelain post insulators with SCD = 38 mm/kV will flashover more than 3 times per year at KIPTS;

RTV SR A coated porcelain post insulators with SCD ≥ 24 mm/kV will have no flashovers per year at KIPTS. RTV SR A coated porcelain transformer bushings at KIPTS with SCD = 30 mm/kV will perform well for 15 years;

Open aerodynamic alternating shed profile with S/P ratio ≥ 1 and a hydrophobic material with good hydrophobicity transfer capability will work best.

Hollows: SR hollow core insulators with SCD ≥ 28 mm/kV will have no flashovers per year at KIPTS;

Open aerodynamic alternating shed profile with S/P ratio ≥ 1 and hydrophobic material with a good hydrophobicity transfer capability will work best.

Longrods:  SR longrod insulators with SCD ≥ 22 mm/kV will have no flashovers per year at KIPTS;

Open aerodynamic alternating shed profile with S/P ratio ≥ 1 and hydrophobic material with a good hydrophobicity transfer capability will work best.

Note: Corona rings should be installed on 132 kV longrod insulators.

Strings: Standard glass cap & pin disc insulator (F12/146) strings with SCD of 27 mm/kV will flashover more than 3 times per year at KIPTS. The same insulator string with RTV SR A coating applied will have no flashovers per year;

Fog-type glass cap & pin disc insulator (F120P/146) strings with SCD of 37 mm/kV will have no flashovers per year at KIPTS. The same insulator string with RTV SR C coating applied will experience similar leakage currents to SR longrod insulators.

Note: Expect poor natural washing/cleaning and pin erosion problems.

Approach 2: Measure & Test

Approach 2 (as per Fig. 3) is used along with Section 12 of IEC/TS -2 for porcelain and glass, and Section 12 of IEC/TS -3 for polymeric insulators.

The pollution and climate at Duinefontein Substation (as in Approach 1) give the expected pollution severity levels and climate in the area of the proposed 132 kV substation and interconnecting 132 kV lines as follows:

Type A: (E6/7) d – Heavy as 40 natural pre-deposited pollution events per year with critical wetting (ESDD2% = 0.165 mg/cm2 with STD deviation of 0.57 and ESDD/NSDD ratio = 1.1).

Type B: (E7) e – Very Heavy as one instantaneous conductive fog pollution event per year (ESDD2% = 0.4 mg/cm2 and NSDD = 0.182 mg/cm2).

Candidate insulators were selected as shown in Table 4, where possible with a maximum connecting length of 1.48 ± 0.02 m, minimum insulation length of 1.2 m, minimum dry arcing distance of 1.5 m, minimum specific creepage distance of 31 mm/kV (CD ≥ mm). Insulators with open aerodynamic alternating shed profile with S/P ratio ≥ 1, and hydrophobic material with good hydrophobicity transfer capabilities. Porcelain post, standard glass and fog type glass insulators were included as reference.

Laboratory pollution U50% flashover voltage (using the rapid flashover test method) curves at three pollution levels (as in Fig. 4) – SDD of 0.06; 0.12 and 0.48 mg/cm2 with NSDD ≥ 0.1 mg/cm2 was obtained using:

• for porcelain and glass insulators the Solid Layer Test Method (see Table 5) according to IEC using Procedure B and spray gun for applying the Kaolin composition and Annex B.3.2. The degree of pollution on the test insulator was determined using the SDD method. Recommendations as given in Annex D and E were followed.

• and, for polymeric insulators according to modified Solid Layer Test Method (see Table 5) with pre-conditioning procedure, and with/without recovery according to Cigre TB 555 and Cigre TB 691.

The rapid flashover laboratory solid layer pollution test done on SR Longrod A insulator to determine U50% = 225 kV at SDD = 0.12 mg/cm2 and NSDD = 0.1 mg/cm2 with 48-hour hydrophobicity recovery is shown in Figure 6 as example. The rapid flashover laboratory solid layer pollution test results for all the candidate insulators are shown in Table 4.

The candidate insulators’ pollution U50% flashover voltage results in Table 4 were then converted into flashover stress along the test insulation length HT = 1.2 m as  in kV/m and is presented as a three-point approximated inverse power law curves against pollution level SDD in mg/cm2 in Fig. 7.

The candidate insulator pollution flashover performance curve constants A in kV/m and α was determined for equation U50%/Ht = A · SDD-α and the values are shown in Table 4.

Um-ph/H was calculated as 70 kV/m using the specified insulation length H = 1.2 m, and Um-ph = 83.7 kV (the highest system r.m.s. phase to ground voltage that the insulator to be supplied will be subjected to).

The candidate insulator was accepted for further calculation if  U50%/Ht> 70 kV/m in the SDD range of 0.12 to 0.48 mg/cm2.

Insulator pollution flashover performance curve constants A in kV/m and α, of the candidate insulators was used along with pollution severity levels and climate in the area of the proposed 132 kV substation and interconnecting 132 kV lines in the statistical approach as per Annex G of IEC/TS -1 in order to optimize insulation selection. Fig. 8 shows the Insulator Selection Tool, a commercially available statistical software.

As example, using the IST for MTBF of 50 years 768 – 132 kV SR Longrod A insulators require:

• SCD of 20.2 mm/kV when exposed to 40 natural Type A pre-deposited pollution events per year with critical wetting (ESDD2%= 0.165 mg/cm2 with STD deviation of 0.57 and ESDD/NSDD ratio = 1.1) (see Fig. 9);

• and SCD of 22 mm/kV when exposed to one Type B instantaneous conductive fog pollution event per year (ESDD2%= 0.4 mg/cm2 and NSDD = 0.182 mg/cm2) (see Fig. 10).

The MTBF obtainable within the required connecting length of 1.48 ± 0.02 m and SCD needed for MTBF of 50 years was calculated for the reference and candidate insulators using the IST. Results are shown in Table 6.

Approach 3: Measure & Design

As per Fig. 5, the area proposed for the 132 kV substation and interconnecting lines can be classified for Type A pollution as Class d – Heavy and for Type B pollution as Class e – Very Heavy. Thus, in the worst case, a minimum SCD of 31 mm/kV is needed for the reference glass disc insulator.

As per IEC/TS -2, the following is recommended for porcelain and glass insulators:

• Aerodynamic, alternating sheds on long rod insulators, post insulators, hollow core insulators;

• Anti-fog profile for disc insulators;

• p1 – p2 ≥ 15 mm, s/p ≥ 0.65, c ≥ 25 mm, l/d ≤ 5, 5˚ ≤ α ≤ 25˚ and CF ≤ 4 (lowest risk options used);

• No altitude correction required;

• 10% increase in SCD for hollow core insulators with average diameter > 300 mm and < 400 mm.

For more information, please visit Aerodynamic Glass Insulator.

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As per IEC/TS -3, the following is recommended for hydrophobicity transfer polymeric insulators:

• SCD could be reduced or increased depending on the environment or pollution level (no clear advice given);

• Aerodynamic alternating sheds;

• p1 – p2 ≥ 18 mm, s/p ≥ 0.75, c ≥ 40 mm, l/d ≤ 4.5, 5˚ ≤ α ≤ 25˚ and CF ≤ 4 (lowest risk options used);

• No altitude correction required;

• 10% increase in SCD for hollow core insulators with average diameter > 300 mm and < 400 mm.

Insulators must have a minimum SCD of 31 mm/kV (CD = mm) and hollow core insulators with minimum SCD of 31 x 1.1 = 34.1 mm/kV (CD = mm) are recommended. Table 7 provides a summary and comparison of results obtained for these three Approaches.

Discussion

As per Table 7, the findings of Approach 1 and 2 correlate with one another, showing that both approaches would work if correct data required as per Fig. 3 is available. The practical examples demonstrate that both approaches lead to a selection having good accuracy. Moreover, as per Table 7, Approach 3 in general would result in over-dimensioning of required insulation.

Table 8 offers a comparison of the recommendations as per IEC/TR and specifications as per Approach 3 in IEC/TS -1 for the practical examples. Findings are similar in regard to specific creepage distance. However, Approach 3 takes into account use of hydrophobicity transfer materials, which could result in a one class lower SCD, different profile parameters and anti-fog instead of open aerodynamic disc insulators.

Conclusions

In summary it has been demonstrated with practical examples, how the old technical recommendation, i.e., IEC/TR and the new technical specification i.e., IEC/TS are being successfully applied by a utility, in this case, Eskom, to select and dimension outdoor insulators for polluted environments (Note: Ageing and failure modes are not taken into consideration in this discussion).

The importance is also shown of site pollution severity measurements, climatic conditions, identifying pollution type and practical use of data collected from natural pollution test sites, in-service insulators, laboratory pollution flashover tests and statistical evaluation.

1.What is a high voltage glass insulator?

A high voltage glass insulator is a specialized component used in electrical power transmission and distribution systems to support and isolate high voltage conductors from the tower and ground. These insulators are typically made of toughened glass, chosen for its high dielectric strength, which means it can withstand high voltages without breaking down. They are designed to prevent electrical energy from escaping the system, either through arcing or as heat.

Function: High voltage insulators provide the necessary insulation to keep high voltage conductors separated from the supporting structure (like a tower) and the ground, preventing electrical short circuits.

Material: They are often constructed from glass, specifically toughened glass, which is a type of glass that has been heat-treated to increase its strength and durability.

Design: These insulators come in various shapes and sizes, depending on the voltage and application. Some common designs include string insulators (used for high voltage power lines) and bushings (used in transformer connections).

Advantages: Glass insulators offer several advantages, including high mechanical strength, weather resistance, and the ability to easily detect defects like cracks, as they are transparent.

Applications: High voltage glass insulators are essential components in power transmission and distribution lines, substations, and other electrical infrastructure where high voltage insulation is needed.

2.What are the main properties of a high-voltage glass insulator?

High-voltage glass insulators are characterized by high dielectric strength, mechanical strength, resistance to environmental factors, and durability. They are designed to withstand high voltages without breakdown, are strong enough to support conductors, and can resist weathering, contamination, and other environmental conditions.

Weather Resistance: Glass insulators can withstand various weather conditions, including rain, snow, temperature fluctuations, and exposure to sunlight.

Resistance to Contamination: They are designed to resist the accumulation of dust, dirt, and pollutants, which can lead to flashover.

Chemical Inertness: Glass is chemically inert and resists corrosion and degradation from various chemicals.

Air Permeability: They allow for airflow, aiding in heat dissipation and preventing moisture buildup.

Low Maintenance: Their durability and resistance to environmental factors require minimal maintenance.

3.What is the importance of high voltage glass insulators in an electrical system?

High voltage glass insulators are crucial in electrical systems for safety, stability, and efficient power transmission. They prevent short circuits, electric shocks, and power interruptions by mechanically holding conductors in place and preventing current leakage. Additionally, they help maintain the electrical system's stability and ensure safe operation by preventing current flow to unintended paths.

Safety: our glass insulator prevent electrical current from flowing to ground or unintended paths, which is vital for avoiding short circuits, electric shocks, and electrical fires.

Stability:glass electric insulators help maintain the electrical system's stability by preventing current leakage and ensuring that electrical energy is transmitted effectively.

Power Transmission: high voltage insulator ensure the reliable transmission of electricity by preventing current flow to ground and maintaining the integrity of the electrical system.

Mechanical Support: They provide physical support to electrical conductors, preventing them from sagging, falling, or damaging.

Preventing Electrical Discharge: Insulators protect against electrical hazards, such as electrical discharge and arcing, which can damage equipment and endanger personnel.

4.What are the factors to consider when selecting high-voltage glass insulators?

When selecting high-voltage glass insulators, consider mechanical strength, electrical properties, environmental factors, and economic factors to ensure reliable and safe performance. Key aspects include the voltage rating, mechanical load capacity, resistance to contamination, thermal stability, and ease of installation and maintenance.

1. Mechanical Strength:

Load Capacity, Residual Mechanical Strength, Design

2. Electrical Properties:

Voltage Rating, Dielectric Strength, Creepage Distance, Leakage Distance:

3. Environmental Factors:

Resistance to Contamination, Weather Resistance, Thermal Stability

5.What are the main parameters that define each model of glass insulator?

The main parameters defining a model of glass insulator include mechanical, dimensional, geometric, and electrical properties. These parameters are crucial for ensuring the insulator's performance and safety under various operating conditions.

Mechanical Parameters:

Mechanical breaking load: This refers to the maximum load the insulator can withstand before fracturing.

Coupling standard: This specifies the method used to connect the insulator to the tower or other components.

Diameter: This specifies the insulator's physical dimensions.

Dimensional Parameters:

Creepage distance: The distance along the insulator's surface that an electric arc can travel without causing a flashover.

Pitch: The spacing between the ribs or protrusions on the insulator.

Geometric Parameters: Insulator profile: The shape and configuration of the insulator, including the shape of the individual glass discs or segments.

Electrical Parameters: Dry and wet power frequency withstand voltages: The voltage the insulator can withstand under dry and wet conditions at normal power frequencies.

Lightning impulse withstand voltages: The voltage the insulator can withstand under lightning impulse conditions.

Flashover voltage: The voltage at which a disruptive discharge (flashover) occurs across the insulator.

6.What is the installation and maintenance process for high-voltage glass insulators?

High-voltage glass insulators are crucial components in power transmission systems, requiring careful installation and maintenance. Installation involves secure fastening to support structures with appropriate hardware and tools, while maintenance includes regular inspections for contamination and corrective actions.

Installation Process:

1. Secure Fastening: Insulators must be securely fastened to the supporting structures using appropriate hardware and tools, ensuring a robust and reliable connection.

2. Environmental Considerations: The installation process should take into account the specific environmental conditions, including pollution levels and weather patterns, to ensure long-term performance.

3. Proper Alignment: Insulators need to be properly aligned and spaced to ensure optimal performance and prevent electrical faults.

Maintenance Process:

1. Regular Inspection: Regular inspections are crucial for detecting any signs of contamination, damage, or deterioration, which can compromise insulation integrity.

2. Contamination Removal: In polluted environments, regular cleaning and washing of insulators are necessary to remove accumulated contaminants and maintain their insulating properties.

3. Coating Application: Applying coatings, such as silicone grease or RTV silicone rubber, can enhance the hydrophobicity of insulators, preventing water accumulation and reducing the risk of flashovers.

4. Partial Discharge Monitoring: Monitoring for partial discharges (PD) using acoustic or other advanced techniques can help identify potential problems and plan maintenance proactively.

5. Replacement: Damaged or deteriorated insulators should be replaced to maintain the reliability and safety of the system.

7.What materials are used in the manufacture of high voltage glass insulators?

High voltage glass insulators are primarily made of high-quality toughened glass for their main insulation body. They also utilize metal fittings, such as cast iron, forged steel, cement, and stainless steel, for fastening and bonding, along with bonding materials.

Toughened Glass: The core of the insulator, providing high mechanical and thermal strength, and electrical insulation.

Metal Fittings: Used for connecting the insulator to transmission lines and other components. Common materials include cast iron, forged steel, stainless steel, and sometimes bronze.

Bonding Materials: Like aluminous cement, are used to secure the metal fittings to the glass, ensuring a robust and reliable connection.

Additional Materials: Some insulators might also incorporate other materials like zinc sleeves for corrosion resistance in harsh environments.

Raw Materials for Glass Production: Raw materials for producing the glass include silica, alumina, sodium carbonate, sodium sulfate, limestone, potash, and dolomite.

8.How does contamination affect the performance of high-voltage glass insulators?

Contamination on high-voltage glass insulators, such as dirt, salt, or dust, significantly reduces their insulation performance by creating conductive paths and increasing the risk of flashover and power outages. These contaminants, combined with moisture, can lead to the formation of a conductive layer, allowing leakage current to flow and weakening the insulator's ability to withstand high voltages.

• Reduced Dielectric Strength: Contamination reduces the insulator's ability to withstand electric stress, leading to flashover (sparking) and potential power outages.
• Increased Leakage Current: Contaminants on the insulator surface, especially when wet, create a conductive path that allows leakage current to flow, further weakening the insulation.
• Accelerated Aging: Excessive contamination, particularly with corrosive elements, can accelerate the aging and degradation of the insulator material.
• Flashover: The combination of contamination and moisture can lead to flashover, a sudden breakdown of the insulator's electrical insulation, potentially causing a power outage.

9.What are the measures that can be taken to mitigate the effects of contamination on high voltage insulators?

To mitigate the effects of contamination on high-voltage insulators, a multi-pronged approach is recommended. This includes regular cleaning, applying protective coatings, and adjusting insulator designs to improve performance under contaminated conditions.

1. Cleaning and Maintenance:

Washing: Regularly washing insulators with deionized water to remove contaminants is a common practice.

Blasting: Using blasting techniques to remove organic material and other pollutants can be effective.

Visual Inspections: Regular visual inspections help identify signs of degradation and contamination early on.

2. Protective Coatings:

Silicone Grease/Coatings: Using silicone grease or coatings on insulators can create a water-repellent and arc-track-resistant surface, encapsulating pollutants and improving long-term performance.

Room Temperature Vulcanization (RTV) Silicone Coatings: These coatings, especially in highly contaminated areas, offer excellent dielectric properties and flexibility, helping to reduce flashover risks.

3. Design and Material Considerations:

Hydrophobic Surfaces: Employing silicone rubber materials or other hydrophobic surfaces on insulators can improve performance under pollution and reduce leakage currents.

Creepage Distance Optimization: Adjusting the creepage distance (the distance an electric field can travel across the insulator surface) can improve the insulator's ability to withstand contaminated conditions.

10.What are the differences between a glass insulator and other types of insulators?

Glass insulators stand out compared to other insulator types like ceramics and polymers due to their high dielectric strength, mechanical durability, and resistance to environmental factors. They offer superior electrical insulation and longer lifespans, contributing to a more sustainable and robust electrical system.

• Dielectric Strength: Glass insulators boast a significantly higher dielectric strength than ceramics or polymers, meaning they can withstand higher electrical stress without failing. This makes them suitable for high-voltage applications where reliable insulation is crucial.
• Mechanical Strength and Durability: Glass insulators are known for their mechanical strength, particularly their resistance to breaking and compressive stress. Their durability and long lifespan make them a reliable choice for long-term electrical infrastructure.
• Environmental Resistance: Glass insulators are highly resistant to contamination, moisture, and temperature variations, making them suitable for various environments. Their low thermal expansion coefficient minimizes deformation due to temperature changes.
• Manufacturing and Cost: While glass insulators offer superior performance, they can be more expensive and require specialized manufacturing processes compared to some other insulators.

11.What are the environmental benefits of using high-voltage glass insulators?

High-voltage glass insulators offer several environmental advantages, including a longer lifespan, recyclability, and reduced environmental impact compared to alternative materials like ceramic or composite insulators. Their durability and resistance to environmental degradation minimize waste and lower the consumption of natural resources. Additionally, they are easy to install and maintain, further reducing the environmental footprint associated with power transmission.

• Reduced Environmental Impact: The use of glass insulators, especially in high-voltage applications, can minimize the need for other materials and processes, leading to lower environmental footprints.
• Resistance to Environmental Degradation: Glass exhibits good resistance to weathering, pollution, and other environmental factors, contributing to its longevity and reducing the need for frequent replacements.
• Lower Consumption of Natural Resources: Compared to materials like porcelain or some composite materials, glass insulators may require fewer raw materials and energy to manufacture, leading to reduced resource depletion.
• Improved Performance in Polluted Environments: Glass insulators, particularly those with specific surface treatments, can exhibit superior performance in polluted environments, minimizing the risk of flashovers and power outages.

12.What do you know about China high-voltage glass insulator manufacturer-Nooa Electric?

Nooa Electric is a major global manufacturer of glass insulators, used in power transmission lines and substations. These power line insulators prevent the flow of electricity between conductive components and grounded structures, ensuring safe and reliable power delivery. Nooa Electric is known for producing a wide range of glass insulators, including toughened glass insulators for high-voltage applications

• Nooa Electric Co., Ltd. - China Leading Powerline Insulators Manufacturer With 22+ Experience.
• Self-own 70,000 ㎡toughened glass insulators factory. More Than 200 Employees, Including 25 Technicians.
• Production Capacity : Pieces Per Year with 2 New Kilns.
• The Qualified Supplier For State Grid Corporation Of China And Southern State Grid Corporation Of China, And Is A Participating Unit Of Product Standard Formulation Of The National Electrical Insulator Standard Committee.
• The range of suspension insulators produced in Nooa Electric complies with the main international and national standards: IEC, ANSI, ISO, TYPE TEST, INTERTEC.

13.What are the best high-voltage glass insulator solutions for different weathers and environments?

best glass insulator solutions are tailored to specific needs, ranging from protecting against pollution and severe weather to enhancing thermal insulation and addressing particular application requirements.

• Polluted environments：Anti-pollution / Anti-fog profile powerline insulator
• Desertic and industrial pollution environments：open profiles glass insulators
• Extreme cold environments: standard type glass insulators
• Regular environments：Standard profile glass insulator

14.What are the Main high-voltage glass insulators does Nooa Electric manufacture?

Nooa Electric manufactures various types of glass power line insulators, including standard profile, anti-pollution profile, and aerodynamic types, as well as multi-umbrella and ground wire insulators. The details as below

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