High-resistance grounding system

 High-resistance grounding system :

 High-resistance grounding (HRG) systems are commonly used in plants and mills where continued operation of processes is paramount in the event of a fault. High-resistance grounding is normally accomplished by connecting the high side of a single-phase distribution transformer between the system neutral and ground, and connecting a resistor across the low-voltage secondary to provide the desired lower value of high side ground current. With an HRG system, service is maintained even during a ground fault condition. If a fault does occur, alarm indications and lights help the user quickly locate and correct the problem or allow for an orderly shutdown of the process. An HRG system limits ground fault current to between 1A and 10A.

Advantages

• Limits the ground fault current to a low level.

• Reduces electric shock hazards.

• Controls transient overvoltages.

• Reduces the mechanical stresses in circuits and equipment.

• Maintains continuity of service.

• Reduces the line voltage drop caused by the occurrence and clearing of a ground fault.

Disadvantages

• High frequencies can appear as nuisance alarms.

• Ground fault may be left on system for an extended period of time.

Grounding of an electrical system is a decision many of us face on a daily basis. As we’ve seen, several methods exist to accomplish this task, each offering its own advantages and disadvantages. As an electrical designer or installation professional its up to you to make the final decision as to when best to install the most appropriate system.