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How to Choose replacement porcelain insulator?

12 May.,2025

How to Choose a Polymer Insulator Equivalent for a Porcelain String

Looking at polymer insulators, we’ve considered several factors that determine superior material and product performance. But then you ultimately need to ask, how do you begin to replace porcelain strings with polymer insulators?

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To do that, we need to consider equivalence. This is how we set criteria that allows us to determine what characteristics are critical for switching to polymer.

This brief overview covers the insulator characteristics you need to consider when finding a suitable polymer equivalent to porcelain string. For an in-depth discussion, please read the detailed white paper.

Physical and Electrical Characteristics

There are two broad categories of functional performance equivalence to look at, the physical and electrical characteristics.

Physical equivalence has two aspects. These are defining the mechanical strength of the porcelain bells and determining the appropriate section length. Polymer insulator designs offer various strength ratings as well as the ability to effectively match the section length. This minimizes the impact to existing porcelain bell string designs.

Then the electrical characteristics must be analyzed for suitability with the system voltage. The three types of stress typically considered are:

60 Hz power frequency
switching impulse
lightning impulse voltage

Therefore, the electrical characteristics must be verified after selecting the right strength and size insulator.

Beyond other electrical stresses, transmission line flashovers at nominal system voltage are often caused by contamination build-up on the insulator string. Therefore, comparing leakage distances of insulators is important for determining performance under these conditions.

Making the Comparison

The ultimate strength of porcelain suspension insulators is characterized by the porcelain mechanical and electrical (M & E) value. For polymer suspension insulators, the equivalent measure is the specified mechanical load (SML).

To select a proper strength Hubbell polymer insulator, choose one with an SML equal to or greater than the M & E value of the porcelain insulator. From there, an understanding of the required electrical ratings of the line leads to ensuring the polymer insulator meets the specific design criteria.

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In many cases, the polymer insulator of similar SML will meet or exceed the required electrical ratings. Providing increased leakage distance depends on shed profile, leading to improved contamination performance over the same section length of a porcelain string.

More Considerations Switching from Porcelain to Polymer Insulators

Hubbell Quadri*Sil polymer insulators can provide effective alternatives to porcelain strings when the proper characteristics of the transmission line and assembly are taken into consideration.

But don’t just take our word for it. Check out our white paper which includes the calculations and examples. You’ll find detailed guidelines in “Polymer vs Porcelain Suspension Insulator Equivalence—What to Use?”.

How to Select Electrical Insulator – The Insulator Guide

CVOLT Transmission and Distribution Systems specializes in manufacturing and supplying electrical insulators for overhead power transmission and distribution systems. These insulators prevent unwanted electrical currents from passing through transmission & Distrubutions lines, ensuring safety and efficiency. Made from composite materials resistant to electrical currents and harsh weather conditions, these insulators protect conductors from excess voltages. Common types include pin, post , strain/Disc, Line Post, suspension, and tension insulators, each designed for specific applications and environmental conditions, helping to safeguard overhead systems from lightning and surges.

When replacing porcelain insulators with polymer ones, there are several advantages to consider. Key factors include material properties and product performance. The main question is: how do you start transitioning from porcelain to polymer insulators?

Lets Start the understanding the Types of Insulator.

Key Considerations When Choosing Electrical Insulators

When selecting insulators for transmission lines, it’s crucial to consider several factors to ensure reliability and durability:

Specified mechanical load (SML): The insulator must withstand mechanical loads without failure.
Sectional Length: It should be in Required/Desired Length as per the Power Transmission Lines.
Electrical Performance: The insulator’s ability to resist electrical breakdown is crucial. This includes factors like dielectric strength, leakage distance, and creepage distance, which influence the insulator’s performance under high voltage.
Creep Distance: The creepage distance (the shortest path between two conductive parts along the surface of the insulator) must be sufficient to prevent flashovers, especially in polluted environments.
Thermal Properties: The insulator should have a high thermal endurance to withstand temperature changes without degrading. This is particularly important in areas with extreme temperature fluctuations.
Aging and Durability: Insulators should be resistant to aging and environmental degradation over time. The lifespan of the insulator under the specific operating conditions should be considered to minimize maintenance and replacement costs.
Compliance with Standards: Ensure the insulator complies with relevant industry standards and certifications, such as those from IEC, ANSI, or IEEE, to guarantee safety and performance.
Application Specific Requirements: Depending on the specific application, such as transmission lines, substations, or distribution systems, the insulator may have unique requirements, like specific shapes, sizes, or mounting configurations

Additionally, the reputation and quality standards of the manufacturer are important, as different manufacturers may offer insulators with varying features and reliability. Ensuring these factors will contribute to the longevity and effectiveness of the insulator in the electrical system.

If you are looking for one of the most distinguished Electrical insulator manufacturers in India, CVOLT TRANSMISSION AND DISTRIBUTION SYSTEMS is the right place for you.

Contact us to discuss your requirements of replacement porcelain insulator. Our experienced sales team can help you identify the options that best suit your needs.

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