overcurrent protection and surge protection

[panthripu]

The RC unit fixed on the transformer for protection from overvoltages--what kind of maintenace is done on it ? How can the healthiness of RC unit be checked for big transformers.
Same for the surge arrestors.Is there any test other than visual inspection ?Can the healthiness of checked that it is really supressing the surges?

 

[ron]

In addition to visual checks, you can perform resistance measurements through bolted connections with a low-resistance ohmmeter, you can perform an insulation-resistance test on each arrester, phase terminal-to-ground with voltage application in accordance with manufacturer?s published data (below the clamping voltage) and you can test grounding connections.