Can anyone explain about different type of earthing system

different type of earthing system

one needs to distinguish between to what is commonly referred to as the " Dirty Earth", also known as the general Electrical earth; To this mat all ELECTRICAL devices are connected.( Motors, drives soft starts etc) Then there is the “Clean earth” mat used for all field Instrumentation and DCS/PLC earthing. The 2 mats are very often located under the same MCC or Equipment room and should be at least 3.5m apart to prevent inter-action. Correct earthing of Instrumentation systems is critical to their performance and should be correctly applied.