IEEE Std C62.11-2020 pdf free download.IEEE Standard for Metal-Oxide Surge Arresters for AC Power Circuits ( > 1 kV ).
8.4.2.2.1 The 1.2150 impulse sparkover determination test
The 1.2/50 impulse sparkover determination test is performed using at least five positive and five negative waves. A minimum prospective magnitude of 1.2 times the arrester’s discharge voltage at a lightning impulse classifying current (per Table 3 or Table 4) shall be used. The maximum arrester voltage recorded during the five positive and five negative polarity standard lightning impulses shall be compared to the discharge voltage obtained with the currents in Table 3 or Table 4. If the lightning impulse classifying current discharge voltage exceeds the voltage values measured during the impulse test described earlier, the lightning impulse classifying current discharge voltage is the 1.2/50 impulse protective level, and no further testing is required on this wave shape. If the voltage measured during the impulse test exceeds the lightning impulse classifying current discharge voltage, proceed to 8.4.2.2.2 to determine the 1.2/50 impulse protective level.
8.4.2.2.2 The 1.2150 impulse sparkover test
The purpose of the I .2i50 impulse sparkover test is to determine the highest standard lightning impulse voltage greater than 3 is duration that the arrester will allow without sparkovcr.
For each polarity, the test procedure shall be as follows:
a) Determine the base generator charge voltage. VG, according to the method described in the following note and record crest voltage and time to sparkover (where sparkover occurs) for each of the 20 impulses used for establishing 1’G•
The procedure for establishing VG is as follows: start by applying an impulse having a prospective crest voltage somewhat lower than the expected sparkover voltage of the arrester, raising the generator charge voltage in approximately 5% steps for subsequent impulses until sparkover occurs. Then apply a series of 20 impulses, decreasing the prospective crest voltage by about 5% after every sparkover and increasing the prospective crest voltage by about 5% after every withstand. I is the average generator charge voltage used during the series of 20 impulses.
b) Apply five impulses using a generator charge voltage not more than 1.05 Vi,; then record crest voltage and time to sparkover. If sparkover does not occur within 3.0 is after the virtual zero point on each of the lIve impulses. IEEE Std C62.11-2020 pdf free download.