Zero Sequence Impedance
Zero Sequence Impedance
(OP)
Dear All,
If the cable has neutral conductor, is the zero sequence impedance calculated different?.I have difficulty figuring out how the consultant has come up with the Z(on) at the end.
PRIMARY SUPPLY SYSTEM
Z0 0.586 < 82.88 100 MVA
0.0726 +j 0.5812 100 MVA
SUPPLY TRANSFORMER
Primary Voltage 44 KV
Secondary Voltage .6 KV
ONAN Rating 2.5 MVA
Ratio X/R 9.846 [typical]
Impedance 5.65% on base
Include tolerance -7.50% [MIN]
5.226% < 84.20
Zmin=0.528%+j5.200%
0.2112+j2.080
600 V CABLES
750 MCM Cu
14.9352 m RUN LENGTH
49 ft RUN LENGTH
6 CONDUCTOR/PHASE
6 NEUTRAL CONDUCTOR
Z 0= 0.05689 +j 0.60363 ? per mi
= 0.00053 +j 0.00560 ? actual
= 0.14665 +j 1.55607 ? on
= 1.56297 < 84.62 ? p.u.
Z(on)=.38990+j3.89204
Max Line to ground =33200A
If the cable has neutral conductor, is the zero sequence impedance calculated different?.I have difficulty figuring out how the consultant has come up with the Z(on) at the end.
PRIMARY SUPPLY SYSTEM
Z0 0.586 < 82.88 100 MVA
0.0726 +j 0.5812 100 MVA
SUPPLY TRANSFORMER
Primary Voltage 44 KV
Secondary Voltage .6 KV
ONAN Rating 2.5 MVA
Ratio X/R 9.846 [typical]
Impedance 5.65% on base
Include tolerance -7.50% [MIN]
5.226% < 84.20
Zmin=0.528%+j5.200%
0.2112+j2.080
600 V CABLES
750 MCM Cu
14.9352 m RUN LENGTH
49 ft RUN LENGTH
6 CONDUCTOR/PHASE
6 NEUTRAL CONDUCTOR
Z 0= 0.05689 +j 0.60363 ? per mi
= 0.00053 +j 0.00560 ? actual
= 0.14665 +j 1.55607 ? on
= 1.56297 < 84.62 ? p.u.
Z(on)=.38990+j3.89204
Max Line to ground =33200A






RE: Zero Sequence Impedance
RE: Zero Sequence Impedance
Zn0=.14665+.2112+.0726=.43045
compare to Zn0=.38990
So, where the difference is come from?
I really appreciate, if you know any literature source on the subject that I can read
RE: Zero Sequence Impedance
RE: Zero Sequence Impedance
Kerite has published some typical values for shielded cables.
http://
RE: Zero Sequence Impedance
It seems having neutral conductor has some effects on conductor zero sequence.
Zn0=.14665+.2112+.0726=.43045
compare to Zn0=.38990
I appreciate if you could go through the calculations and see if you will get the same results or not.
RE: Zero Sequence Impedance
It appears we're assuming the transf. is connected Dy?
RE: Zero Sequence Impedance
RE: Zero Sequence Impedance
Cables are inside PVC ducts
6X(4-750 MCM + 500 MCM GND)
RE: Zero Sequence Impedance
What are the two values?
What do these four lines mean?
RE: Zero Sequence Impedance
Z0=.586<82.88 This value is provided by the utility.
Z0= .586*cos(82.88)+j*.586*sin(82.88)
The second line is for cable based on 49' run
Z(49')=.00053+j.00560
Per unit value for 600V,100MVA
Z0=.14665+j1.55607
Z0=sqrt((.14665^2)+(1.55607^2))<atan(1.55607/.14665)
Z0=1.5629<84.62
RE: Zero Sequence Impedance
I think I understand the impedance representations, but I agree it seems to not add up. Excluding the primary, I get:
0.358 + j3.636 pu
RE: Zero Sequence Impedance
RE: Zero Sequence Impedance
Z0(49') = (0.05689 + j0.60363)(5280/49) = 0.00052795 + j0.00560187, which equals 0.00562669<84.616°
Z0(49')pu = (0.00052795 + j0.00560187)/(600V^2/100000000) = 1.56297<84.616° which equals 0.14665 = j1.556075