Hello everybody,

What is the difference between protective earth and functional earth? How are they constructed?

 

I also want to know it.

Maung Maung Latt

 

protective earth is also called dirty earth, which is used to protect the personnel & equipment.

However the functional earth is clean earth. Which is also a reference earth for the digital and analog signals. It is also required to reduce the distortion in the signals.

 

protective earth or circuit protective earth is intended to protect the personals from electric shock during an earth fault in any appliances he/she is using. This earth conductor will have a connection from appliances metalic exposed part up to the main earth terminal in the supply intake room. The fault current will flow through this conductor to the eart mass which will in turn on the protective devices such as MCB or RCD to safely open the circuit within 0.4 seconds.

Functional earth is intended to reduce the radio frequency noise, computer filters to enhance the clarity of signals or other equipments which have always 10mA leakage current. Functional earthing must be separated from installation earthing except at the main earth terminal connection point.

 

in our product for outdoor application we use SMPS which has Ln N & 'FG' pins at input. It is replacement to older SMPS (with L & N only)

Should we connect 'FG' to field Earth?