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Neutral and Earth voltage with battery storage


I have a battery storage system which is grid tied. This has been G98 registered. The battery has a grid tie and a UPS backup circuit.

The system works as expected, however when in UPS backup mode, I have noticed something that I need to clarify.

When in normal grid tied mode, the following voltages are recorded on the UPS output: 

L-N = 230V 

L-E = 230V 

N-E = 0V 

When in UPS mode, the following: 

L-N = 230V

L-E = 130V

N-E = 130V 

The manufacturer confirmed that when in UPS mode, a N-E link is made automatically and disconnected automatically. I have contacted them but being in China, they are slow to respond.

What I noticed, is that if you switch off loads on the UPS output, the voltage between L&E slowly increases to around 200V. I haven’t as yet tested to see if the same is apparent with N&E. 

Any ideas? This is an inverter so I am unsure if this sort of reading/phenomenon is normal? 


  • The manufacturer today confirmed the following: 

    A “N-E” bond is created on the UPS backup output when in backup mode. 

    Voltages of 130V between N-E and L-E are normal, due to capacitances in the UPS output.

    That doesn't make sense to me - any capacitive coupling between N and PE should be shunted out by the N-PE link (if it's correctly being applied).

       - Andy.

  • I thought that too

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