The Common Impedance is a per unit impedance model including an ideal transformer. The main usage is for branches used ...
DIgSILENT PowerFactory Technical Reference Documentation
Common Impedance ElmZpu
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Contents
Contents 1 General Description 1.1 Models
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1.2 Input Parameter
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1.2.1 Basic Data and Load-flow, Simulation and Full Short-circuit parameter . .
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1.2.2 Basic Data and VDE/IEC and ANSI short-circuit parameter . . . . . . . .
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List of Figures
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List of Tables
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Common Impedance (ElmZpu)
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General Description
1 1.1
General Description Models
The Common Impedance is a per unit impedance model including an ideal transformer. The main usage is for branches used for network reduction. The transformer ratio is equivalent to the nominal voltage of the connected busbars. Figure 1.1 shows the model for absolute impedance. Figure 1.2 shows the model for p.u. impedance.
Figure 1.1: Common impedance positive, negative and zero-sequence model in ohm, absolute values
Figure 1.2: Common impedance positive, negative and zero-sequence model in p.u.
U ni and U nj are the nominal voltage of the connected busbars in kV. The following equations in p.u. are used: ui − uj = z ij · ii uj − ui = z ji · ij with z ij = rij pu + jxij pu z ji = rji pu + jxji pu The corresponding impedance in ohm seems from connection side i is calculated according to:
Z ij =
Common Impedance (ElmZpu)
U n2i · (rij pu + jxij pu) Sn
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General Description
from connection side j:
Z ji =
U n2j · (rji pu + jxji pu) Sn
with U ni , U nj Nominal busbar voltage of side i and side j Sn Nominal power in MVA of common impedance For the short-circuit calculation method IEC/VDE and ANSI it is possible to use different impedances as for the load flow calculation and the complete short-circuit method (see option: Use same impedance as for load-flow ). Further is it possible to insert different impedances for Zi−j and Zj−i (see option: Use equal Impedances (zij = zji) ). The zero-sequence impedance can be inserted separately. If the option Use same Impedance z2=z1 is enabled, when is the negative sequence impedance equal to the positive-sequence impedance.
1.2 1.2.1
Input Parameter Basic Data and Load-flow, Simulation and Full Short-circuit parameter Table 1.1: Input Parameters of the Common Impedance Parameter
Description
Unit
Sn nphases
Nominal Power No. of phases ( 3phase or 1phase model ) Use equal impedances zij = zji Positive-sequence impedances from i-j Positive-sequence impedances from j-i Zero-sequence impedances from i-j Zero -sequence impedances from j-i Use Impedance z2 = z1 Negative-sequence impedances from i-j Negative-sequence impedances from j-i
MVA 1 or 3
iequalz r pu, x pu r pu ji, x pu ji r0 pu, x0 pu r0 pu ji, x0 pu ji iz2eqz1 r2 pu, x2 pu r2 pu ji, x2 pu ji
Common Impedance (ElmZpu)
enable/disable p.u. p.u. p.u. p.u. enable/disable p.u. p.u.
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General Description
1.2.2
Basic Data and VDE/IEC and ANSI short-circuit parameter Table 1.2: Input Parameters of the Basic Data Page Parameter
Description
Unit
Sn nphases
Nominal Power No. of phases ( 3phase or 1phase model ) Use same impedance as for load-flow
MVA 1 or 3
iZshc
enable/disable
If the option Use same impedance as for load-flow is disabled the following additional parameters are used: Table 1.3: Input Parameters of the Load-Flow Model Parameter
Description
Unit
rs pu, xs pu
Positive-sequence impedances from i-j Positive-sequence impedances from j-i Zero-sequence impedances from i-j Zero -sequence impedances from j-i Negative-sequence impedances from i-j Negative-sequence impedances from j-i
p.u.
rs pu ji, xs pu ji r0s pu, x0s pu r0s pu ji, x0s pu ji r2s pu, x2s pu r2s pu ji, x2s pu ji
Common Impedance (ElmZpu)
p.u. p.u. p.u. p.u. p.u.
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List of Figures
List of Figures 1.1 Common impedance positive, negative and zero-sequence model in ohm, absolute values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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1.2 Common impedance positive, negative and zero-sequence model in p.u. . . . . .
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Common Impedance (ElmZpu)
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List of Tables
List of Tables 1.1 Input Parameters of the Common Impedance . . . . . . . . . . . . . . . . . . . .
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1.2 Input Parameters of the Basic Data Page . . . . . . . . . . . . . . . . . . . . . .
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1.3 Input Parameters of the Load-Flow Model . . . . . . . . . . . . . . . . . . . . . .
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