techref_imeas[1].pdf
TRANSCRIPT
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D I g S I L E N T T e c h n i c a lD o c u m e n t a t i o n
Current Measurement
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C u r r e n t M e a s u r e m e n t 2
DIgSILENT GmbHHeinrich-Hertz-Strasse 9D-72810 GomaringenTel.: +49 7072 9168 - 0Fax: +49 7072 9168- 88http://www.digsilent.dee-mail: [email protected]
Current Measurement
Published byDIgSILENT GmbH, Germany
Copyright 2009. All rightsreserved. Unauthorised copyingor publishing of this or any partof this document is prohibited.
TechRef StaImea V1
Build 337 05.05.2009
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T a b l e o f C o n t e n t s
C u r r e n t M e a s u r e m e n t 3
Table of Contents
1 GENERAL DESCRIPTION................................................ ......................................................... .............................. 4
1.1 RMS EQUATIONS........................................................................................................................................................... 4
1.1.1 Balanced .................................................................................................................................................................... 41.1.2 Unbalanced ................................................................................................................................................................51.2 EMT EQUATIONS ........................................................................................................................................................... 5
2 INPUT/OUTPUT DEFINITION OF DYNAMIC MODELS ........................................ ................................................... 7
2.1 STABILITY MODEL (RMS)............................................................................................................................................... 7
2.2 EMT MODEL .................................................................................................................................................................. 8
3 INPUT PARAMETER DEFINITIONS............... .................................................. ....................................................... 9
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1 G e n e r a l D e s c r i p t i o n
C u r r e n t M e a s u r e m e n t 5
1.1.2Unbalanced
i, iiand irare positive sequence currents. The current magnitude for unbalanced RMS simulation is calculated as follows:
3-phase system:
}Im{
}Re{
2
3
2
1
2
3
2
1
3
1
ii
ii
ijijii
i
r
cba
=
=
+
++=
(2)
2-phase system:
( )ba iii +=2
1 (3)
Single-phase system:
aii= (4)
DC system:
0==
i
ar
i
ii (5)
1.2
EMT Equations
ir, iiand iare the phasor currents and ia, iband icare the instantaneous phase values in kA of the measured phase currents. The
phase currents are transformed to space vectors (phasor) in the --system. The factors of the -transformation are selected
in a way that the rated current corresponds to an RMS-value. E.g. a symmetrical three-phase current with an RMS-value of 1kA
(peak value of 2 kA) will result in an -current with a magnitude of 1=+ ii p.u., assuming a rated current of 1kA.
Hence, the output of RMS- and EMT-simulation is compatible, which is important for models that shall be used in bothsimulation modes.
The zero-sequence is neglected in the transformation. iis corresponding to the output irand ito the output iiof the current
measurement device. For 2-phase systems an analogous transformation is used.
The output currents for EMT simulation are calculated as follows:
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1 G e n e r a l D e s c r i p t i o n
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3-phase system:
( )
( )cbi
cbar
iii
iiii
=
=
333
1
23
1
(6)
2-phase system:
( )
0
2
1
=
+=
i
bar
i
iii (7)
Single-phase system:
0=
=
i
ar
i
ii (8)
DC system:
0=
=
i
ar
i
ii (9)
The current magnitude is in all cases defined as:
22
ir iii += (10)
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2 I n p u t / O u t p u t D e f i n i t i o n o f D y n a m i c M o d e l s
C u r r e n t M e a s u r e m e n t 7
2Input/Output Definition of Dynamic Models
2.1Stability Model (RMS)
Figure 1: Input/Output Definition of the current measurement for balanced stability analysis (RMS-simulation)
Figure 2: Input/Output Definition of the current measurement for unbalanced stability analysis (RMS-
simulation)
Figure 3: Input/Output Definition of the current measurement for balanced stability analysis (RMS-simulation)
in DC networks
Table 1: Input Definition of the RMS-Model (for internal use only)
ir_A ir
ir_A
ii_A
ir
ii
iir_B
ii_B
ir_C
ii_C
ir_A
ii_Air
ii
i
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2 I n p u t / O u t p u t D e f i n i t i o n o f D y n a m i c M o d e l s
C u r r e n t M e a s u r e m e n t 8
Parameter Description Unit
ir_A Input Current, Real Part, Phase A
(based on 1MVA and nominal voltage)
p.u.
ii_A Input Current, Imaginary Part, Phase A
(based on 1MVA and nominal voltage)
p.u.
ir_B Input Current, Real Part, Phase B
(based on 1MVA and nominal voltage)
p.u.
ii_B Input Current, Imaginary Part, Phase B
(based on 1MVA and nominal voltage)
p.u.
ir_C Input Current, Real Part, Phase C
(based on 1MVA and nominal voltage)
p.u.
ii_C Input Current, Imaginary Part, Phase C
(based on 1MVA and nominal voltage)
p.u.
Table 2: Output Definition of the RMS-Model
Parameter Description Unit
i Output Current, Magnitude p.u.
ir Output Current, Real Part p.u.
ii Output Current, Imaginary Part p.u.
2.2EMT Model
Figure 4: Input/Output Definition of the current measurement for EMT analysis
Figure 5: Input/Output Definition of the current measurement for EMT analysis in DC networks
i_A ir
i_A
i_B ir
ii
i
i_C
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3 I n p u t P a r a m e t e r D e f i n i t i o n s
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Table 3: Input Definition of the EMT-Model (for internal use only)
Parameter Description Unit
i_A Input Current, Phase A
(based on 1MVA and nominal voltage)
p.u.
i_B Input Current, Phase B
(based on 1MVA and nominal voltage)
p.u.
i_C Input Current, Phase C
(based on 1MVA and nominal voltage)
p.u.
Table 4: Output Definition of the EMT-Model
Parameter Description Unit
i Output Current, Magnitude p.u.
ir Output Current, Real Part p.u.
ii Output Current, Imaginary Part p.u.
3Input Parameter Definitions
Table 5: Parameter Definitions
Parameter Description Unit
loc_name Name
pcubic Measurement cubicle for current measurement
i_mode Used current rating
Inom User defined current rating kA
iAstabint A-stable integration algorithm