high resistance grounding (HRG) Vs solid grounding
high resistance grounding (HRG) Vs solid grounding
(OP)
Can anyone help regarding high resistance grounding (HRG) and solidly grounded system?
I am interested to know what are pros/ cons of both systems. In our utility solid grounding is used for the LV distribution systems.
What advantages can we get if HRG system is used instead?
Another clarification required regarding HRG systems is the voltage rise on healthy phases in event of SLG fault? What is extent of this voltage rise?
I am interested to know what are pros/ cons of both systems. In our utility solid grounding is used for the LV distribution systems.
What advantages can we get if HRG system is used instead?
Another clarification required regarding HRG systems is the voltage rise on healthy phases in event of SLG fault? What is extent of this voltage rise?






RE: high resistance grounding (HRG) Vs solid grounding
Voltage rise on the unfaulted phases can reach phase-phase voltage from phase to ground, or 1.73 pu.
RE: high resistance grounding (HRG) Vs solid grounding
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(2B)+(2B)' ?
RE: high resistance grounding (HRG) Vs solid grounding
Bill
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"Why not the best?"
Jimmy Carter
RE: high resistance grounding (HRG) Vs solid grounding
RE: high resistance grounding (HRG) Vs solid grounding
High resistance grounding provides safer, reliable and economic system. HRG is preferred for continuous process industries and limits the ground fault current.
Most common reason for not using HRG is that in a typical power system, one phase or three phase four wire loads are fed. HRG is preferred on three phase three wire systems.
During a ground fault, the steady state L-G voltage of the unfaulted phases would be close to full L-L voltage.
RE: high resistance grounding (HRG) Vs solid grounding
Can I ask what systems are in use in US utilities where both single phase and three phase loads are to be supplied (that is distribution systems)? Is it HRG or solidly grounded?
I understand that in past (and still at few places) in US delta systems (3ph-3wire) were in use which were later replaced by corner delta systems (3ph-4wire). Are these systems still exist? if yes what earthing is used for these systems?
In UK only solidly grounded systems are used for low voltage distribution (230/400 volts).
M.A.Sh.
Elect. Engr.
RE: high resistance grounding (HRG) Vs solid grounding
Corner grounded systems are three wire delta systems. One phase is grounded.
3 ph., 4 wire systems are generally 240 Volt delta systems but at least one side of the delta is center-tapped for 120:240 Volts. Single phase panels are fed with 120/240 Volts.
Three phase four wire panels are fed with the three phases and the fourth wire comes from the center tap. The center tap is grounded.
Two phases are at 120 volts to ground and the third phase is at 208 Volts to ground. This is often called the wild leg, or the high leg. The NEC prohibits connecting single phase loads to the
In a 3 ph. 4 wire panel three phase loads are connected to the three phase bus bars and receive 240 Volts three phase. HRG is mainly found in industrial plants.
Further, there is a code rule to the effect that if grounding a neutral will result in maximum voltages to ground of 150 Volts or less then the neutral MUST be grounded. As far as I know, the high leg is not usable for circuits connected to the neutral and the rule is applied to 120/120/240 4 wire circuits.
But North America is a big place and there may be local exceptions.
Bill
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"Why not the best?"
Jimmy Carter
RE: high resistance grounding (HRG) Vs solid grounding
Single phase fault = 3 V(0)/(Z1+Z2+ZO+ZF) where as Z1=Positive sequence impedance, Z2=negative sequence impedance, Z0=zero sequence impedance, V(0)=Prefault voltage.
Benefit by doing this, your transformer will be not overstress when Single Phase fault occured. In transmission and distribution utility, transformer is the most expensive equipment(will cost millions). The utility will alyways want to protect their most expensive equipment.
You may refer to the Ieee141, iee241, ieee 242, iee 399 and power system anaylsis book by Hadi Saadat.
RE: high resistance grounding (HRG) Vs solid grounding
27.6 kV system is a three phase 4 wire system, I wonder why would they do it and make it a 4 wire and suppply neutral; may be there pole tops primary is 16.7 kV. Just wondering the concept behind this application.
RE: high resistance grounding (HRG) Vs solid grounding
Some other distribution voltages are;
12,000/6,900 V, 13,200/7,620 V, 13,800/7,960 V, 25000/14,400 V, and 35,000/20,200 V.
The neutral conductor will be grounded at each transformer location and about 4 times per mile.
I am not familiar with the 1.5 Ohm resistor grounding but I imagine it may be to encourage any neutral current to return via the neutral conductor so as to lessen the erosion of the ground electrodes.
Bill
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"Why not the best?"
Jimmy Carter
RE: high resistance grounding (HRG) Vs solid grounding
RE: high resistance grounding (HRG) Vs solid grounding
X0/X1 ratio should be equal to or less than 3 and R0/X1 equal to or less than 1, at any point in the system.
RE: high resistance grounding (HRG) Vs solid grounding
With a 1.5 ohm resistor, the system would not be HRG. HRG is used on low voltage systems, not medium voltage systems. I don't know of any US utilities that provide an HRG secondary service. Generally an HRG system would be provided by the customer.
RE: high resistance grounding (HRG) Vs solid grounding
Please notice that the solid/effective grounded system has low overvoltage but high fault current. In contrast, the HRG has high overvoltage and low fault current.
For overvoltage associated with the coefficient of grounding, the enclosed link to thread238-237503: COG (Coefficient of Grounding) may help.
RE: high resistance grounding (HRG) Vs solid grounding
RE: high resistance grounding (HRG) Vs solid grounding
Bill
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"Why not the best?"
Jimmy Carter
RE: high resistance grounding (HRG) Vs solid grounding
Thanks for your warm welcome back.
RE: high resistance grounding (HRG) Vs solid grounding
RE: high resistance grounding (HRG) Vs solid grounding
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If we learn from our mistakes I'm getting a great education!
RE: high resistance grounding (HRG) Vs solid grounding
RE: high resistance grounding (HRG) Vs solid grounding
Thanks