I studied the photos of the 24kV/250A CT porcelain insulator you sent me. Are you complaining about the unglazed (white) spots on the porcelain insulators as shown in the photos? Please feedback whether your QC inspectors had discovered any unglazed spot with area more than 100 mm2 (with photos).
I would like to inform you that routine visual inspection of the porcelain insulators was conducted according to IEC 62155 standard. The area of any single glaze defect shall not exceed 100 mm2 as stated on page 65 of IEC 62155 standard. Our factory adopted a more stringent passing criteria for the top surface of the porcelain insulators - any single glaze defect shall not have an area exceeding 25 mm2. The attached photos showed that the single glaze defect was less than 25 mm2. Thus we are not able to reject these porcelain insulators to our factory. Please send me photos showing the single glaze defect area of more than 25 mm2 on the top side of the porcelain and 100 mm2 for the rest of the porcelain surfaces. I need these photos to make a claim to our factory and request for new replacement porcelains.
I will visit Charoenchai factory afte the Songkran holidays to conduct a joint inspection on the CT bushing porcelains. We will support you and make a claim to the factory if the defects are justified based on IEC 62155 standard.
I look forward to more input from you.