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In Germany the low-voltage grid is 0.4kV whereas the plugs in flats have 230V. Who is responsible for this conversion? Smart meter?

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    \$\begingroup\$ You are comparing apples and oranges, that is line2line and line2neutral voltages. \$\endgroup\$ – PlasmaHH Apr 3 '18 at 11:58
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    \$\begingroup\$ Smart meter? of course not because the 380 V / 220 V system has been in use long before smart meters even existed. \$\endgroup\$ – Bimpelrekkie Apr 3 '18 at 12:11
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There is no conversion going on because it isn't needed.

The 400 V is the voltage between two phases of the 3-phase 380V grid.

The 230 V is the voltage between one phase and neutral.

Read more at: Three-phase electric power

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  • \$\begingroup\$ Is it still called 380 V grid when it carries 400 V nowadays? \$\endgroup\$ – Arsenal Apr 3 '18 at 15:31
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    \$\begingroup\$ Yes. It might actually be 400, and the "230" might be 240. \$\endgroup\$ – Jamie Hanrahan Apr 3 '18 at 15:33
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    \$\begingroup\$ Assuming the phase angles are correct the phase-phase voltage is always sqrt(3) times the phase-neutral voltage. Roughly speaking 220 goes with 380, 230 goes with 400 and 240 goes with 415. \$\endgroup\$ – Peter Green Apr 3 '18 at 18:16
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LV grids in Germany and Europe usually consists on a three-phase connection with a voltage of 400 V (L-L). (Global exceptions)

However for harmonization residential distribution of the Low voltage grid is distributed to 230 V (L-N) for private households and continues using 400 V to others that need this voltage or 3 phase power.

Metering is a separate issue.

There are many different meter designs

  • active power in 3-phase 4-wire network with service to 1 to 4

One to four tariff. Ability to measure power only in any two phases or in any one phase (when these options must be neutral connected).

  • active power in one or two three-phase or four-wire network

One to four tariff. Ability to measure power in only one phase with the conditions attached neutral.

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No. Meters measure. They don't convert.

Conversion between AC voltages is done with transformers.

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