the Earth should not be connected to the DC bus. It should remain floating.
By the way is there anyway to attach Ltspice files to this forum?
Your monitor circuit is generating huge leakage currents and power dissipation and surely no acceptable IMD solution.
What is your of insulation resistance threshold specification?
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I expect that an IMD circuit should comply with IEC 61557-8 Insulation monitoring devices for IT systems
Besides a reasonable limit for leakage currents generated by the device, it should be able to detect both asymmetrical and symmetrical earth leakage. The presented circuit is however blind against symmetrical leakage by design. An IMD can't detect all kinds of ground faults without utilizing an AC test voltage or current.
How? the 10 k resistors are grounding the network midpoint. If you add another pair of resistors to ground downstream to the load or in the solar panel, the circuit stays in balance and no additional ground current is generated.For the symmetrical earth leakage I will use a current sensor like a LEM or something like that. Therefore I will cover all the cases.
The file is different from posted schematic (incomplete). The new scheme also seems to involve new problems like needing kV rated transistors for the current limiter circuit.Please find attached the ltspice simulation model here
If your design is somehow related to IEC 61557-8 is needs to detect symmetrical ground faults as well. As already mentioned, it's not possible without using an AC or pulsed DC test voltage.However the specs of my design does not describes such a problem. At the beginning, I need to detect earth leakage in VPAN+ and VPAN- individually.
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