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I've been wondering what would happen if you grounded both star points of a Y/Y connected transformer. This shouldn't affect the voltages, so why really is it not advised to earth both the primary and secondary star points of a transformer?

Any information on this will be appreciated.

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    \$\begingroup\$ what if the 3 sides are not balanced? \$\endgroup\$ – analogsystemsrf Oct 12 '19 at 8:34
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    \$\begingroup\$ You forgot to mention the type of the transformer. There are 3 and 5 limb types, makes a lot of difference. \$\endgroup\$ – Marko Buršič Oct 12 '19 at 9:19
  • \$\begingroup\$ If the primary star point is not grounded and one phase connection is broken, the voltage over both remaining windings will be substantially lower than the voltage between a phase and ground. \$\endgroup\$ – Uwe Oct 12 '19 at 10:35
  • \$\begingroup\$ Doesn't the primary side have an earth-to-neutral bond already? \$\endgroup\$ – ThreePhaseEel Oct 12 '19 at 14:22
  • \$\begingroup\$ Who advises to not earth both star points? There are thousands of intertie transformers in the power grid with both Y winding star points connected to earth. You can't always extrapolate advice for 1 application to a wider rule. \$\endgroup\$ – relayman357 Oct 13 '19 at 22:00

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