A ground fault on a production line can bring more than one machine to a stop. Depending on the power system, it may interrupt a whole process and leave crews dealing with unfinished work or material stuck in equipment.
High resistance grounding gives electrical designers a way to limit ground-fault current. It connects the system neutral to ground through a resistor, while monitoring equipment alerts the maintenance team when a fault occurs.
Where the design allows, the system may keep operating after the first ground fault. The team still needs to find and repair it. HRG does not prevent faults or promise uninterrupted operation.
How High Resistance Grounding Works
The neutral grounding resistor sits between the system neutral and ground. When a phase conductor faults to ground, the resistor limits the current flowing through that connection. A monitor detects the fault and raises an alarm.
The electrical designer selects the resistor and protection arrangement for the system. The facility also needs a clear response procedure: who receives the alarm, how the fault is located, and when repairs take place.
An alarm needs attention even if the equipment keeps running. A second fault on another phase can create a much more serious condition.
Why Some Facilities Use HRG
In a process plant, stopping equipment suddenly may affect several connected operations. Maintenance crews may need time to shut down a line properly, clear material, or arrange a repair.
An HRG system can help provide that time after a first ground fault, where continued operation is permitted by the design. This is one reason it is used in selected manufacturing plants, process facilities, and industrial power systems.
Some mission-critical facilities also use resistance grounding. However, a data center or critical building does not need HRG simply because downtime is costly. The grounding method has to suit the loads, protection scheme, operating procedures, and applicable code requirements.
How It Differs From Solid Grounding
A solidly grounded system connects the neutral to ground without an intentional grounding resistor. An HRG system adds resistance to limit ground-fault current.
Item | Solid grounding | High resistance grounding |
Neutral connection | No intentional grounding resistor | Through a neutral grounding resistor |
Ground-fault current | Depends on the system and fault path | Limited by the grounding design |
Fault response | Protection commonly disconnects the affected circuit | May allow continued operation after the first fault |
Room coordination | Grounding and bonding connections | Resistor, monitoring, connections, and access |
The designer chooses the arrangement that fits the project. Equipment bonding is still required with HRG; the resistor does not replace those connections.
The Equipment Needs Space in the Room
On a one-line diagram, the resistor takes up very little space. The actual equipment may need its own enclosure, mounting location, cable connections, and room for maintenance.
Some units are part of an equipment assembly. Others are installed separately. The approved equipment drawings should guide what goes into the model, including:
- The resistor enclosure and its mounting
- Monitoring equipment or an indication panel
- Connections to the transformer or switchgear
- Grounding and control routes
- Required access and clearances
- Nearby conduit, cable tray, busway, piping, and framing
Electrical BIM services should include these items while the room layout is still being developed. Waiting until the main equipment and pathways are fixed can leave few workable locations.
What Happens When the Resistor Is Left Out?
Imagine a transformer feeding a distribution lineup in an industrial electrical room. The one-line shows a neutral grounding resistor, but the room model includes only the transformer, switchgear, conduits, and cable tray.
When the team adds the resistor enclosure, the intended wall space is already covered by conduit. Another location sits behind piping. A third has enough space for the enclosure but leaves a difficult route back to the transformer.
At that point, fitting the equipment means revisiting work the team thought was settled.
Adding it earlier lets the team review the enclosure and its connections together. They can adjust nearby routes, check the mounting, and leave enough access to inspect the unit and reach the monitor.
On an industrial facility electrical BIM project, that review may also involve process piping, ventilation, structural framing, and equipment-removal routes. BIM coordination services help the trades check how their installations share the room.
Where the distribution includes main-tie-main switchgear or multiple transformers, the team must follow the approved design when modeling the HRG connections.
For data center projects, data center BIM services bring the approved HRG equipment into the wider room and pathway review. The team checks its location alongside the facility’s critical power systems, cooling equipment, and structural elements.
BIM shows whether the equipment can be installed and maintained. The electrical engineer remains responsible for choosing the grounding method, sizing the resistor, and defining the protection requirements.
Include HRG in the Room Layout
High resistance grounding may help a facility manage a ground fault without an immediate shutdown. Once it is part of the design, its equipment needs the same coordination attention as the transformer and switchgear.
Electrical room modeling should include the enclosure, connections, monitoring, and access before the layout is finalized. That gives the construction team a chance to resolve space and routing problems before installation.
Frequently Asked Questions
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What is high resistance grounding?
It connects the system neutral to ground through a resistor that limits ground-fault current.
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How does an HRG system work?
The resistor limits current during a ground fault, and monitoring equipment alerts personnel so they can locate and repair it.
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Why do facilities use HRG?
Where the design permits, it can allow continued operation after a first ground fault while personnel arrange a response.
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Where is HRG used?
Selected manufacturing plants, process facilities, industrial distribution systems, and some mission-critical applications use it.
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How does HRG affect BIM coordination?
The team needs to account for the equipment, mounting, connections, cable routes, and maintenance access in the room model.
Is the Grounding Equipment Missing From Your Room Model?
Eracore coordinates HRG equipment with transformers, switchgear, feeder routes, and surrounding building systems so crews have room to install and maintain it.
