Trends and Practices in Grounding and Ground Fault Protection Using Static Devices

Grounded and ungrounded systems are in general use in both commercial and industrial distribution systems. Proponents of each type of system have established valid points to defend their position. This paper briefly identifies the types of systems in use in each category and lists some of the main advantages and disadvantages of each. With the advent of higher voltage levels in our low-voltage distribution systems and the trend towards solidly grounded systems, problems resulting from the lack of proper ground fault protective devices have caused some severe equipment burndowns. The need for adequate protection has been recognized by the 1971 National Electric Code. This recognition is being complemented by Underwriters´ Laboratories with the introduction of appropriate standards. With the passing of the Occupational Safety and Health Act of 1970, more emphasis than ever before will be placed on adherence to the preceding code and standards. This paper will review the various methods of detecting ground faults using static devices and describe some of the equipment available for these applications.