Grounding resistors
Grounding resistors
(OP)
What is the difference between a neutral grounding resistor and a neutral grounding reactor. Can one be used instead of the other for grounding substation transformer neutrals?
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RE: Grounding resistors
RE: Grounding resistors
You mention commercial or industrial applications...
It is quite common for utilities to use neutral grounding reactors and I would imagine quite a few are for industrial/commercial applications. Certainly resistors are much more common, but reactors do have their applications.
Reactors seem to be used more on generators as resonant grounding systems or on transformers as low-resistance grounding systems.
For resonant ground systems, the reactor is sized to resonate with the system capacitance, thus limiting the fault current to very low magnitude. Depending on the fault type, this can allow generators to remain in operation, through a fault condition. There are stories about generators taking a fault condition for over 1 hour with little to no damage.
For low-resistance grounding systems, the reactors may prove to have some economic advatages over resistors.
RE: Grounding resistors
RE: Grounding resistors
D. Beeman "Industrial Power Systems Handbook" includes the low voltage (up to 600VAC) generator grounded via low value reactance with a remark that the grounding reactance should pass ground currents equal to at least 25% of three-phase value.
The Beeman Handbook correctly makes a distinction between the reactance system grounding and ground fault neutralizer that also uses the reactor for the system grounding.
The reactor system grounded generator may have the current for phase-to-ground 5 to 25% of three-phase fault current. It is not used much since it causes excessive overvoltages.
The ground fault neutralizer is used for high voltage overhead lines where faults may be self-healing. It has nearly zero fault currents and the transient voltages are not excessive.
RE: Grounding resistors
A 1991 version appears at:
standards.ieee.org/colorbooks/sampler/Greenbook.pdf
Am I out of date / showing my age / misunderstood the question?
RAC
RE: Grounding resistors
For ~2-35kV distribution circuits, the two methods are compared in §3.3 of ANSI/IEEE Standard C62.92.4-1991 …Application of Neutral Grounding in Electrical Utility Systems, Part IV—Distribution
Reactor versus resistor grounding seem to be regional preferences/practices, based to a large degree on operating history versus service continuity and life-cycle costs. Reactor grounding may experience resonant-overvoltage problems not usually associated with resistive grounding.
RE: Grounding resistors
Thanks all for your reply to the post and references you've mentioned