Manufacturer of Low and Medium Voltage Switchgear


Understanding Neutral Grounding Resistors

Safety is critical in electrical systems. A key aspect of ensuring safety is the proper grounding of electrical equipment. Grounding helps protect people and equipment from electrical faults and potential hazards. A neutral earth resistor (NER) is an important component of an electrical system that provides a controlled path for the flow of fault current in the event of a ground fault.

What is a Neutral Earth Resistor?

A neutral earth resistor is a resistor connected between the neutral point of an electrical system and earth. It is designed to limit the fault current flowing through the neutral point during a ground fault. The resistor is usually made of high quality, high temperature resistant materials such as stainless steel or nickel-chromium alloy. It is specifically chosen for its ability to handle the high fault currents that can occur during a fault.

Uses of Neutral Grounding Resistors

The main purpose of a neutral point grounding resistor is to protect the electrical system and its components from damage that may occur during a ground fault. When a ground fault occurs, the fault current seeks a path to ground. Without a neutral grounding resistor, this fault current can cause serious damage to equipment, resulting in costly repairs and downtime.

By connecting a neutral grounding resistor, the fault current can be diverted through this resistor, thus limiting its magnitude. This controlled flow of fault current helps protect the system by preventing excessive current from flowing through the neutral. It also helps prevent voltage imbalance and reduces the risk of electrical fires and other hazards.

How does a neutral earth resistor work?

During normal operation, the neutral earth resistor remains idle as fault currents are minimized. However, if an earth fault occurs, the fault current increases significantly. This increase in current activates the neutral earth resistor, allowing the fault current to flow through it.

The resistor is designed with a specific resistance value that limits the fault current to a safe level. The resistance value is carefully calculated based on system characteristics such as fault current level, system voltage and fault duration. By controlling the fault current, neutral grounding resistors help prevent damage to the electrical system.

Benefits of using neutral grounding resistors

There are several benefits to using a neutral grounding resistor in an electrical system:

Prevents Equipment Damage: By limiting the fault current, neutral grounding resistors help protect electrical equipment from damage that may occur during a ground fault. This can save businesses from costly repairs and replacements.
Reduced Downtime: When equipment is damaged due to a ground fault, it is often necessary to shut down for repairs. By preventing equipment damage, neutral grounding resistors help minimize downtime and ensure continuous operation.
Enhanced Safety: The controlled flow of fault current provided by neutral grounding resistors reduces the risk of electrical fires, electric shocks and other hazards. It helps create a safer working environment for personnel and equipment.
Improved System Reliability: By preventing excessive fault currents, neutral grounding resistors help maintain system stability and reduce the likelihood of cascading faults or system failures.


Neutral grounding resistors play a vital role in electrical systems by providing a controlled path for fault currents during an earth fault. They help protect equipment, minimize downtime, enhance safety and improve system reliability. By understanding the uses and benefits of neutral grounding resistors, electrical system designers and operators can ensure the safety and efficiency of their systems.

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