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Syed Usman Afaq
08-21-2014 08:19 AM

Zero sequence impedance, positive sequence impedance at 50 Hz

Can anyone provide me the standard parameters of 95 sq mm DIN 48201-E-Cu conductor i.e. Zero sequence impedance, positive sequence impedance etc at 50 Hz. Urgent response is needed
08-21-2014 10:22 AM
Top #2
Ing. Ole Knudsen
08-21-2014 10:22 AM
The only parameters that depend on the conductor alone, are the DC resistance, the mass per meter, the bending modulus, etc.
All other electrical parameters depend on geometric configurations, and surrounding insulation materials, and so on.
08-21-2014 12:34 PM
Top #3
Krishnan S
08-21-2014 12:34 PM
Please look at it this way.
when there is an unbalance in currents in a 3 phase power supply system for analytical purposes can be the currents can be resolved into balanced components such as positive sequence,negative sequence and zero sequence components for ease of treatment.
Likewise unbalance voltages can be resolved into balanced sequence components.
It is surprising that you are attempting to resolve passive components such as conductors into sequence components.
please note sequence components become useful only for unbalance in active parameters such as voltages and currents .
08-21-2014 03:11 PM
Top #4
Shailesh Kumar Chetty
08-21-2014 03:11 PM
Agreed with Mr. Ing. Ole Knudsen comments

better you calculate yourself based on the configuration which you have installed.
08-21-2014 05:45 PM
Top #5
Alan Maltz
08-21-2014 05:45 PM

It should not be surprising that our Trainee Engineer is interested in the sequence impedances. He is trying to figure out how to calculate the impedances for inclusion in a sequence diagram, not resolve passive components into sequence components as you questioned. Once has he has those impedances he can then impose the sequence voltages that you allude to and calculate the sequence voltage drops and/or currents.

As Ole has pointed out, the exact configuration of the conductors relative to each other plays a major role in the impedances and sequence diagram of the cable and how it fits into the overall system sequence network.

For example, three phases laid flat is a source of unbalance because of the unequal spacing of the two outer conductors relative to the center; whereas a triangular configuration has all conductors the same distance from each other and usually results in a balanced system. One may have a significant zero sequence impedance while the other may not.

08-21-2014 08:18 PM
Top #6
Spir Georges GHALI
08-21-2014 08:18 PM
Dear Sayed ;

We know all that each cable has an " Impedance - Z " that compose of a " Resistance - R " and " Reactance -X " where we can calculate each one as follow :

The " Resistance " :
R = ρ x L / S
where :
R : the Resistance in " Ω "
ρ : the Resistivity in " Ω.mm^2 / km^2 ", where that is depend on conductor's material as follow according to " IEC 60909 " at " 20°C " : Copper : ρ = 18.51, Aluminum : ρ = 29.41
L : the Length in " km "
S : the Section of cable in " mm^2 "
Noting that when the ambient temperature if more than " 20°C ", the value of " ρ " is changed according to the Ambient Temperature and the Insulation's material of the conductor.

The " Reactance " :
According to " IEC ", we can calculate it as follow :
X = λ x L
where :
X : the Reactance in " Ω "
λ : a Constant that depends on the following parameters :
- Type of Cable " Single Core or Multi Cores "
- if it's " Single Core " it depends on the " Installation Methods " defined by " IEC 60
364-5-52 "
So, for " 50 Hz " :
- " λ = 0.080 mΩ / m " for " Multi-Cores "
- " λ = 0.085 mΩ / m " for " Single Core " installed as " Trefoil "
- " λ = 0.130 mΩ / m " for " Single Core " installed as " Flat - Touched "
- " λ = 0.145 - 0.150 mΩ / m " for " Single Core " installed as " Flat - Separated "
L : the Length in " m "

Then, by knowing the " R & X ", we can calculate " Z ".
08-21-2014 11:08 PM
Top #7
Ing. Ole Knudsen
08-21-2014 11:08 PM
If you look up in the various standards, you will find that your constants are not quite constant, due to physical phenomena.

The resistance you show, is only correct for DC.
For AC, it depends on both the frequency and the conductor shape, and to a smaller extent on the conductor's position in relation to each other.

For the reactance, you have a similar dependency on distances, which means that voltage and insulating material will affect the reactance, in addition to the conductor shape.

The best source of accurate information will be the various standards that show these values for a variety of thicknesses and configurations.

In Australia, it is the AS/NZS 3008 that covers this issue, and I am sure other countries will have similar standards.
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