Post History

Fault Codes (Page 38)

   ![Tesla gnd fault codes](https://electrical.codidact.com/uploads/ktxh4sq1pw51dfc1cw80py1hzhxp) 

  PE ground is mandatory to be functional and is tested.  Typical standards expect < 25 Ohms for residential zones.
 
  RCD's and similar testers use as test resistor to force an unbalance current  using well-balanced common mode latching relay.  The imbalance creates a differential current to trip at line voltages and would be in low mW levels. 

  Every region or country has its[ own standards for safety using RCD's](https://www.wikiwand.com/en/Residual-current_device) and this also depends on the power category for PE grounded equipment.

  PE is used to shunt noise (EMI or RF pulse coupling) in switching transformers which provide isolation for line frequency at high voltage.  The interwinding capacitance leakage  is generally small so the "Y" film caps only need to be say 100 times bigger to shunt the voltage to PE Gnd with the help of a high inductance BALUN or CM power choke.  


  There are many test methods for the presence of PE gnd and depends on the purpose of the test. For self testing I would measure AC voltage, then DC voltage then constant current diode test. 

   **I imagine Tesla would do something similar with and measure the low frequency AC voltage drop after any other primary safety test.  Measuring with high frequency could be problematic. I would have included an RCD-like functional test into the charger product that does not require human intervention.**

  Keep in mind RCD's and GFCI's use a test resistor to simulate leakage but actual force a latching relay using a balanced CM coil to detect the residual different in L1-L2 or L-N currents.