What Are Neutral Grounding Reactors and Their Usage?

  • 15 Feb, 2020

Neutral Grounding Reactors (NGRs) are used in three-phase power networks for low-impedance grounding of the neutral point. They are used to limit the fault current to the level of the phase-to-phase short-circuit current through the network in the event of short-circuit conditions. Typically, a neutral grounding reactor is used at transmission voltage levels to control a single line to ground faults only. It is connected to the neutral of a transformer in a transmission network to protect and control the system.

A typical neutral grounding reactor, also termed as an air-core reactor, is a series inductance that is installed between the neutral point of a transformer or generator and ground. In simple words, the one terminal of the neutral grounding reactor is connected to the neutral of the transformer or generator and the other terminal is grounded to create a path for the short-circuit current. Short-circuit stress is one of the most common types of fault in a power system and an air-core reactor is used to protect the circuitry from this condition. In the normal operation condition, there will be almost zero control flow through the reactor.

It works as per the Ohm’s law, I=VZ, where I imply to the current flowing through the circuit, V is the voltage supplied, and Z represents the impedance value of the circuit. Going by this law, if we increase the value of the network, the current is reduced. That’s how a neutral grounding reactor serves its purpose of limiting the amount of short-circuiting current that a generator or transformer contributes to the system. The benefit of using perfectly sized Neutral Grounding Reactors in the power transmission system is that it keeps the system effectively grounded.

If you are someone working in the power industry and looking for neutral grounding reactors for the transmission system, you can select reactors based on three parameters – impedance value, 10-second rating, and continuous rating. The required impedance value of the reactor for your requirements can be calculated using the basic Ohm’s law. The 10-second rating defines the maximum amount of short circuit current that the generator can see. The continuous rating is defined by the value of the neutral current the generator will see. The other operating parameters that one should consider are ambient temperature, altitude, maximum wind speed, relative humidity, and seismic capacity.

You should contact a professional and experienced electrical equipment manufacturer in the industry to get the best quality neutral grounding reactors for your needs. They will help you in finding the perfectly sized reactors depending on your requirements and operational conditions. A professional manufacturer also helps with any specific requirements of its clients to match their operational needs.