The primary purpose of a Neutral Grounding Resistor (NGR) is to limit the fault current already present in a single line to ground fault. That is why NGRs are mostly employed in low and medium voltage (LV and MV) distribution networks to ensure generators and transformers remain protected from damaging currents in the event of an earth fault. Alternative protective systems like direct earthling neutral and insulated neutral pose serious disadvantages e.g., transient over-voltages, damaging fault currents with possible arc blast, and difficulties in localizing the ground fault in the insulated systems). That is not the case with the NGR system as it provides a swift response to localize the fault and even prevents the overheating. An NGR system can be inserted between the transformer’s neutral point and the ground to limit the ground fault to get that window of opportunity to enable a quick localization of the fault. Most importantly, it ensures the equipment stays safe.

From the interruption of electricity supply to equipment damage at the fault point and even premature aging of equipment, there are many reasons to install NERs.

How Does A Neutral Grounding Resistor Work?

NGR works by lowering the ground-fault current to a predetermined value. With a properly designed Neutral Grounding system, you can benefit from both ungrounded and solidly grounded systems. When we insert an NGR system between the neutral and ground in a power system, it starts to provide ground fault protection by limiting ground-fault currents to safe levels. Hence, it ensures that all electrical equipment in your power system is fully protected. NERs not only absorb a huge amount of energy but also dissipate it for the duration of the fault event in way that the temperature does not exceed limitations. Therefore, the design and selection of a NER are immensely important if you want to protect equipment and ensure personnel safety.

Purposes of Neutral Grounding Resistor

So, the primary purpose of an NGR in the power system is to limit the high current that flows because of the line to earth fault. An NGR works as a fault current regulator. It limits the fault current with resistance. So, when there is a heavy flow of fault current, it can easily damage the conductor because protection relays require some time to properly isolate the power system. For that little time, NGR steps in by limiting the sudden flow of fault current and converts it into heat energy.

More Interested: Medium Voltage Switchgear

Neutral grounding resistors can also help operate the Earth Fault Relay. It can be done by monitoring and measuring the current that flows through NGR. If there is earth fault, the earth fault relay will trip the circuit. The neutral grounding resistor can help connect protective equipment, which usually cannot operate with a high current. Take the example of Relay. An NGR can be used to reduce the current so that the protective equipment does not have to operate with a high current. NGR also protects the insulation breakdown in electrical equipment. The electrical equipment faults are due to transient over-voltages produced by arching grounded on ungrounded systems. In solidly grounded systems, mechanical stresses in apparatus and circuits carrying fault currents and NGR help reduce them. An NGR also helps measure the fault current through neutral grounding transformers. It can also work as an alarming system by running with a ground fault. Moreover, it provides enough tripping levels that help in careful ground-fault detection.

Power Resistors

When Is An NGR Right For You?

There are many reasons to use NGR. Some of them are:

• There is a high risk of electrical shock or arc flashes that pose a risk to personnel and equipment
• High earth return currents can cause damage or electrical faults to your equipment
• There is a possibility that high earth return currents start to interfere with your telecommunication equipment
• NGR provides safety a reliable, simple, and selective means of protection
• There can be losses because of unplanned downtime

• NGR reduces the step voltage
• There can be rising expenses related to maintenance because of your aging equipment
• Moreover, it reduces operating costs as well

More Interested: Braking Resistors

In any electrical system, the earthing system always plays an important role. To avoid damage to equipment and have a safe operating environment for personnel, you need a NER in AC distribution networks.

Neutral Grounding Resistor The Bottom Line

We explained how important it is to use NGRs. There is no doubt that NGRs provide enhanced safety for personnel and provides more service reliability. Moreover, NGRs also help improve the life of the equipment. Aktif prides itself on offering a range of high-performance NGR solutions to its esteemed clients. So, if you have any queries related to using a Neutral Grounding Resistor or have any other questions, please feel free to contact us.