Porcelain insulator: an old friend with whom not everything is so simple 

When you hear “porcelain insulator,” many, even in the industry, immediately think of something outdated, heavy and fragile. I’ll say right away that this is the first and biggest misconception. Yes, polymers are advancing, but discarding porcelain is a big mistake. In certain conditions, especially when it comes to durability under constant mechanical stress or in aggressive environments, it is still unrivaled. But the question immediately arises: what kind of porcelain? Where are its application limits today? I’ll try to sort it out based on what I personally encountered.

Not just ceramics: what is hidden behind the term

The main thing is to understand thatporcelain insulatorit's not just baked clay. We are talking about high-voltage porcelain, which undergoes multi-stage firing at temperatures above 1200°C. The composition of the mass, the drying mode, the glaze - all this is critically important. A poorly prepared mass produces microcracks, which then develop during thermal cycling (day-night, winter-summer). I saw such samples after 5-7 years of service in a temperate climate - they look scary.

It is the glaze that is the key element of protection. High-quality glaze not only gives shine, but creates a layer that is impenetrable to moisture and chemically resistant. But here lies a common problem: if the application technology is broken, drips and “tears” appear. or underfilled. Dust begins to stick in these places, then moisture, and surface breakdown begins. We once checked a batch of 10 kV bushings - 30% had inhomogeneity in the glaze at the fastening ear. The manufacturer, of course, swore that this was permissible. I had to reject it.

Compared with polymer insulators, porcelain insulators lose in weight and, in some cases, in resistance to vandalism (shots, for example). But theirstability of dielectric propertiesover time - a huge plus. The polymer can age and lose its hydrophobicity, and porcelain, if it survives the first couple of years without defects, will last for decades. It's like a time-tested tool.

Where is it irreplaceable and where is it no longer installed?

There are several niches where I don’t see alternatives to porcelain. The first is highly polluted atmospheres: industrial areas with emissions, the sea coast. What is important here is the resistance of the glaze surface to aggressive salts and acids. The polymer may require frequent cleaning, and the glaze, when properly profiled, will often self-clean with rain.

The second is high mechanical tensile loads. We are talking about long, heavy tires or rigid mounts. The porcelain insulator here works like a stone - it will not “creep” or deform under constant load. For substation equipment, where geometric stability is important, this is critical.

But in 6-10 kV overhead lines you almost never see it in new projects. The reasons are obvious: weight, difficulty of installation (fragility), cost of logistics. Polymer ones are easier and cheaper to install. But here’s what’s interesting: at some facilities built back in the USSR, theseporcelain insulatorsThey hang for 40-50 years and, if not broken, perform their function perfectly. This says something.

Case study: replacement at a substation

We had a project to modernize a 35 kV switchgear cell. There were old Soviet post insulators. The customer insisted on replacing it with “everything modern”, that is, with polymer. But after a detailed analysis of the loads and environment, it turned out that overheating from tires is possible in this compartment, and next to it there is a ventilation duct with raw air. The risk of early aging of the polymer from heat and moisture was high. They convinced us to leave the porcelain, but took modern ones with improved profiles from a reliable supplier. The key argument was preciselystability of dielectric propertiesin unstable temperature and humidity conditions.

Quality problems and how to deal with them

The most pressing issue today is the dispersion in quality. The market is flooded with products that save on everything: on raw materials, on firing, on control. Visually, such an insulator may look decent, but its mechanical bending strength or dielectric strength under impulse voltage is a lottery.

I have developed a rule for myself: always demand factory test reports for the exact batch that is being supplied. Not certificates of conformity in general, but specific tests. Especially onheat resistance of porcelain(temperature drop test) and mechanical destructive load. If the supplier starts to mumble, this is a red flag.

Another point is geometry. It would seem like a small thing. But if deviations in the dimensions of the flange or threaded hole exceed the tolerances, mechanical stress occurs during installation. The insulator operates under load from the moment of installation. Over time, this is guaranteed to lead to a crack. I had to use torque wrenches and templates to avoid over-tightening or putting it crooked.

Working with suppliers: personal experience

In search of a balance between price and quality, you often turn to manufacturers from Asia. The story here is mixed. There are outright consumer goods, and there are companies that seriously work on quality. For example, for several years we have been cooperating withShijiazhuang Hist Electric Co.,Ltd. I came across them almost by accident while studying catalogs of cable fittings manufacturers. Their websitehiste-ru.comQuite informative, it is clear that they are not the first year on the market - they were founded in 2004.

What can I note from theirporcelain insulators- stable geometry and good quality of glaze. We ordered bushings from them for complete transformer substations. They came with a full package of tests, including a partial discharge test. During the acceptance process, no (mechanical) defects were identified. For me, as a practitioner, this is an important indicator - when products arrive from the factory without surprises.

Of course, they are not the only ones, and for some items, especially pin insulators for overhead lines, they do not always have the required standard sizes. But as one of the trusted sources for certain tasks, I can note it. Their profile - cable fittings - is felt in their approach: accuracy in detail is important for connections.

A look into the future: does porcelain have it?

It seems to me that it is premature to talk about the complete displacement of porcelain. His niche is narrowing, but becoming more specialized. This is no longer a mass product for each support, but a piecemeal, critical element for difficult conditions.

Development is moving towards optimizing shapes for better characteristics at the same weight, in the search for new glaze compositions with increased durability. I have seen prototypes with ribs of complex shape, which at a lower height give the same length of the leakage path. This is interesting.

My result is this:porcelain insulatoris a classic that requires a respectful and competent approach. You can’t take it “as long as it’s cheaper?”. It must be properly selected, carefully tested, and precisely applied where its advantages outweigh its disadvantages. In skillful hands, this is a reliable and durable element that will survive more than a dozen years and more than one cycle of modernization around it. This means that understanding it and understanding its subtleties is still necessary.