What Radio Influence Voltage Measures
Radio Influence Voltage (RIV) measures electromagnetic interference from corona discharge on an insulator. It is reported in microvolts at 1000 kHz under a specified test voltage RMS to ground. RIV is not a design rating but a performance limit observed during testing.
How RIV Is Tested and Reported
RIV is measured at a defined test voltage RMS to ground and reported as the maximum value in microvolts at 1000 kHz. For example, the ANSI 57-2 line post insulator is tested at 22kV RMS to ground, with a maximum RIV of 100μV. The ANSI 56-3 high voltage pin type is tested at 30kV RMS to ground, with a maximum RIV of 200μV.
Why Utilities Specify RIV Limits
Utilities set RIV limits to prevent interference with radio and communication systems near transmission lines. A high RIV value indicates significant corona activity, which can degrade insulator performance over time and affect nearby electronic equipment.
What Affects RIV Levels
RIV levels are influenced by glaze quality, fitting design, surface contamination, and the presence of sharp edges or protrusions. A smooth, well-glazed surface and a properly designed fitting reduce corona and lower RIV.
RIV and Insulator Design
Insulators with longer leakage distance and optimized shed profiles tend to have lower RIV. The ANSI 57-2 line post insulator has a 559mm leakage distance and a maximum RIV of 100μV at 22kV RMS. The ANSI 56-3 pin type has a 533mm leakage distance and a maximum RIV of 200μV at 30kV RMS.
RIV vs Flashover and Withstand Voltages
RIV is not a withstand or flashover voltage. It is a separate measurement of electromagnetic noise. A high RIV does not imply poor electrical strength. The flashover and withstand voltages are tested separately and are not directly related to RIV levels.
Using RIV Data in Procurement
When specifying insulators, include RIV limits if electromagnetic interference is a concern. Compare RIV values only at the same test voltage RMS to ground. Use the actual measured values from the product’s test data, not assumed or estimated figures.
RIV in Non-Standard Applications
For non-standard insulator designs, RIV testing is conducted at the specified test voltage RMS to ground. Huahao engineers assist in developing insulators for specific applications, including those with RIV requirements.