Page 53 - Energize April 2022

TECHNICAL

Figure 3a Figure 3b

Test procedures If a test voltage is applied that is greater than 120% of the
The test must be done with consistency, so use the same test arrester’s rated voltage, then it will result in a lower-than-expected
voltage setting and apply the test voltage for the same amount of resistance value even when the arrester is not faulty. Therefore, it
time each time. It is recommended that the test voltage is applied is best to stay within the recommended test voltage range of 50%
for at least 15 s, but optimally 60 s. Repeat the test three times, to 120% of the arrester’s rated voltage.
taking the average reading as the result. A repeatable result is
indicative of a good measurement process. Test results and recommendations
A good medium voltage (1 kV to 30 kV) arrester should have a A test was done on a selection of 15,3 kV rated surge arresters.
very high resistance of gigaohm to terohm range at its operating The test parameters were:
voltage range and arresters of the same type and voltage rating • 15 kV applied test voltage
should have very similar resistance values. Any arrester that • 30 seconds of applied test voltage each time
shows a low resistance value is faulty and must be replaced or • No filters or special settings used
refurbished. • 3 tests were done on each arrester, but only after fully
discharging each time
• Pass/Fail level was determined to be 1 GΩ based on
manufacturer’s information

It is highly recommended to check surge arresters regularly. The
test for them is simple and quick, and it needs to be done. A faulty
arrester can result in severe damage to expensive assets, like
transformers. Therefore, regularly following the simple process
from this application note can save money and maintain a smooth
and steady electric power supply.

Contact Marie-Claude Rasendra, Megger,
Figure 4 Marie-Claude.Rasendra@megger.com, www.megger.com

Arrester ID Test 1 (MΩ) Test 2 (MΩ) Test 3 (MΩ) Average (MΩ) Result
12001 839 919 909 889 FAIL
12003 1115 1212 1206 1178 PASS
12004 1190 1174 1146 1170 PASS
12008 999 1066 1038 1034 PASS
Table 1: Surge arrester test results

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