IEC TS 60815 is a selection and dimensioning workflow, not a universal creepage table. The 2025 second editions of Parts 1, 2 and 3 replaced their 2008 predecessors. They start with the system, application and site, establish site pollution severity (SPS), determine a reference unified specific creepage distance (RUSCD), and then apply candidate-specific corrections before an insulator is selected.
A bid that states only a voltage class and one inherited mm/kV number leaves important decisions unresolved. The purchaser still needs to identify the applicable part and edition, pollution evidence, material family, profile, altitude, orientation, dimensions, correction basis and verification documents.
1. Define the System and Application Before Calculating Creepage
Record the electrical system and the physical application before assigning an SPS class or reviewing an offered profile. At minimum, establish:
- AC or DC system and the voltage basis stated in the project specification;
- outdoor equipment type: line insulator, station post, hollow insulator, bushing or another external insulation application;
- ceramic/glass or polymeric housing, including whether an HTM classification is being claimed;
- site altitude, installation orientation, parallel units or strings, and space constraints;
- pollution source, wetting mechanism, seasonal variation, maintenance practice and nearby operating experience.
If any input is missing, label the calculation preliminary. Do not convert a catalog creepage value into project compliance by assumption.
2. Choose the Correct IEC TS 60815 Part and Edition
| Document | Current role | Procurement use |
|---|---|---|
| IEC TS 60815-1:2025 | Definitions, SPS evaluation and general principles | Establish the site-to-reference-to-candidate workflow |
| IEC TS 60815-2:2025 | Outdoor ceramic and glass insulators for AC systems | Review candidate profile, corrections and verification for ceramic/glass designs |
| IEC TS 60815-3:2025 | Outdoor polymer insulators for AC systems | Review profile corrections and any HTM-based selection approach |
| IEC TS 60815-4:2016 | Insulators for DC systems | Keep DC selection separate from Parts 2 and 3 AC work |
The applicable product standard still has a separate role. IEC TS 60815 addresses selection with respect to pollution; it does not replace the product standard, project insulation-coordination requirements, drawings, type-test schedule or inspection plan.
3. Build a Reviewable Site Pollution Severity Evidence Pack
Part 1 provides methods for evaluating SPS. The project team should state which route it used and preserve the underlying evidence. A procurement package may include measured site data, information from suitably comparable operating sites, environmental descriptors, or a justified combination.
| Evidence field | What to record | Review question |
|---|---|---|
| Pollution source | Marine salt, industrial deposit, dust, agriculture or mixed exposure | Is the source directional, intermittent or seasonal? |
| Wetting mechanism | Fog, dew, rain, spray, condensation or another condition | Can the deposit become conductive in service? |
| Measurement or analogue | Location, dates, method, reference surface and comparison site | Is the evidence representative of the equipment location? |
| Operating history | Nearby insulator type, profile, cleaning and known events | Are the system and exposure genuinely comparable? |
| Design constraints | Altitude, orientation, diameter, parallel units and available length | Which corrections must be considered later? |
Do not assign an SPS class from coastline distance alone. Distance can be one descriptor, but local wind, shielding, salt transport, wetting, terrain, industry and operating evidence can change the site assessment. Use the current standard and the project owner's documented method.
4. Move From SPS to RUSCD, Then to the Candidate USCD
The sequence matters. First determine SPS using Part 1. Then obtain the RUSCD for the reference insulator through the applicable material part. Finally apply the corrections required for the offered candidate and installation.
- Confirm the SPS value or class and its evidence basis.
- Select Part 2, Part 3 or Part 4 according to material and AC/DC system.
- Determine the RUSCD using the selected edition of the applicable document.
- Review candidate corrections for shape, size, position, altitude and other factors identified by that part.
- Translate the corrected USCD into the offered design and show the voltage basis, units and total creepage distance.
- Verify the proposal against the drawing, product standard, test evidence and project acceptance rules.
This page deliberately does not reproduce a numeric SPS-to-RUSCD table. Numeric values and correction procedures must come from the licensed edition named in the contract. Copying a table from a withdrawn edition or an earlier project can create an untraceable design basis.
5. Review More Than Total Creepage Distance
Total creepage is only one candidate field. Ask the bidder to provide a controlled drawing and a calculation sheet that allow the reviewer to connect the selected profile to the project basis.
- total creepage distance and arcing distance, with measurement units;
- insulator diameter, shed spacing, projection, overhang and profile sequence;
- installed position and any restrictions on orientation;
- altitude and other environmental corrections used;
- number of parallel insulators or strings where relevant;
- material family and, for polymeric designs, the declared HTM/non-HTM basis;
- drawing revision and traceability to the type-test specimen or design family.
A candidate that meets an uncorrected creepage number can still be unresolved if its profile, size, installation or material assumptions differ from the reference conditions.
6. Keep Ceramic/Glass and Polymer Selection Paths Separate
Part 2 covers ceramic and glass insulators for outdoor AC systems. Part 3 covers polymeric insulators for outdoor AC systems and introduces hydrophobicity transfer material concepts together with revised correction factors.
Do not grant a blanket percentage reduction because the housing is silicone rubber. Any reduced-creepage approach must follow the current Part 3 method and be supported by the material classification, correction basis and evidence required by the purchaser. A generic catalog statement about hydrophobicity is not a design calculation.
Likewise, do not treat ceramic/glass and polymer pollution tests as interchangeable. The applicable test document depends on the material and system.
7. Specify the Verification Document, Not Just “Pollution Test”
| Reference | Official scope | Boundary to preserve |
|---|---|---|
| IEC 60507:2013 | Artificial pollution tests for outdoor ceramic and glass insulators on AC systems above 1 kV | The IEC scope says these tests are not directly applicable to polymeric insulators |
| IEC TS 63414:2025 | Artificial pollution tests for high-voltage polymeric insulators on AC and DC systems | Pollution withstand alone does not resolve every ageing or field-condition question |
The bid document should state the applicable standard and edition, test method, specimen or design-family identity, test condition, acceptance criterion, laboratory requirement and submission deadline. “Test report available” is not enough when the report cannot be tied to the offered drawing.
8. RFQ and Bid-Comparison Checklist
- system type, voltage basis, equipment type and installation orientation;
- SPS value or class, assessment method, data period and site evidence;
- applicable IEC TS 60815 part and edition;
- RUSCD source, candidate correction sheet, resulting USCD and total creepage;
- controlled profile drawing with all critical dimensions and revision;
- material declaration and any HTM/non-HTM claim with supporting basis;
- altitude, diameter, position, parallel-unit and other applicable corrections;
- product standard, type-test schedule, pollution-test requirement and document due date;
- maintenance, washing, coating or other mitigative measures assumed in the design.
Hold the technical comparison when the bidder uses the wrong material part, cites only the withdrawn 2008 edition without a contract basis, omits the SPS evidence, provides only total creepage, assumes an unexplained polymer reduction, or cannot link the calculation and reports to the offered design.
Scope boundary: This guide explains a procurement workflow. It does not reproduce IEC tables, assign an SPS class, calculate a project USCD, certify an offered insulator or replace the licensed standards, project specification, product standard, insulation-coordination study, drawing and test reports.