The standard you are looking for (IEC 815) has been replaced. This post explains what you need instead. Blog Post: Understanding the IEC 60815 Series (The Successor to IEC 815) Title: Beyond the PDF: What You Need to Know About the IEC 815 Replacement
For years, this was the industry benchmark. However, as high-voltage networks grew more complex and pollution data became more detailed, the technical committee realized the old guide was no longer sufficient. It was officially and replaced. The Current Standard: IEC 60815 You are actually looking for the IEC 60815 series. This is the active, updated version of the old 815 guide. It has been expanded from a single document into a multi-part series. What is IEC 60815? This standard provides a method to determine the required creepage distance (the surface leakage path) for insulators based on the severity of the pollution at the installation site. iec 815 pdf
Instead of one generic PDF, the new standard is split into four parts: The standard you are looking for (IEC 815) has been replaced
Here is what happened to it, why you cannot find it, and—most importantly—which current standard you actually need for selecting insulators in polluted environments. Originally, IEC 815 (1986) was titled: "Guide for the selection of insulators in respect of polluted conditions." However, as high-voltage networks grew more complex and