Electronic – what is the electrical component symbol in datasheet ABB M1M 10

installpower electronicspower-meterschematicsymbol [~]

I am planning to install a power meter ABB M1M 10 with Delta connection (2E) 3 phase 3 wire system. However, I fail to recognize the electrical component symbol in the red area of the attached image below. May I know anyone at here able to recognize this component symbol? May I know what is the symbol standard that I can refer to?

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if my explanation is not clear enough, please refer to attached link pdf ABB M1M part 6.2
link:
https://library.e.abb.com/public/053a9148943a411c8d134fc7a9db366c/Installation%20Manual%20M1M%2010.pdf

Best Answer

They look like surge arrestors. The odd thing is that they only appear on the three-phase 3-wire connection and not on the other two. This makes me think that they should be used when the three-phase supply is floating.

In this way the arrestors will break down if the floating supply drifts above a certain voltage for some reason. The reason for it may be so as not to exceed the CAT III insulation rating of the meter itself.

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