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Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Applications of the Field Analysis During Design Process
of Instrument Transformers
Elzbieta LESNIEWSKA
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Solution of Constructional ProblemsComputations of Electromagnetic and Magnetic Field Distributionsgives possibility of
1. Determining the Equivalent Circuit Parameters2. Choosing an Optimal Design Version3. Selection of Shields
The Field-and-Circuit Method is the most direct method of determining the Characteristics of Current Error and Phase Displacement
The Field-and-Circuit Method application also makes it possible to determine the Composite Error (the Instrument Security Factor KFS and the Accuracy Limit Factor KAF )
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Space-Time 2D analysis allows the computation of a break in the secondary circuit of a current transformer (Peak Values of the Secondary Voltage)
Joining the Field-and-Circuit Method and Space-Time Analysis permits the determination of the operation of protective current transformers during transient state(Instantaneous Error Current vs. Time )
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
1. Choosing the Design Version of an Insulation Systemof HV or Medium Voltage Instrument Transformers
2. Improvement of the Electric Strength of an Insulation System of HV or Medium Voltage Instrument Transformers
3. Selection of Electric Shields4. Design of an Insulation System with Capacitance
Control 5. Design of an Insulation System of the HV Combined
Instrument Transformers
Computation of Electric Fields Distributions gives the possibility of
Application of the Field Method permits the determination of thecoupling parameters of combined instrument transformer
(Mutual Reactance MUI and Mutual Capacitance CUI )(Inner Electromagnetic Compatibility)
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
In regions with currents of known and externally forced distribution, the harmonic electromagnetic field may be described, using the magnetic vector potential A (B = ∇×A), by an equation of Helmholtz type
with Neuman's and Dirichlet's boundary conditions.
wJAAA =j12 µ−ωµγ−×∇×⎟⎟⎠
⎞⎜⎜⎝
⎛µ
∇µ−∇
wzzz
zzz J)Vgradt
A()Arot(rot 1111=+
∂∂
γ+µ
Space-time 2D field-circuit analysis
A MATHEMATICAL MODEL
∫ ∫Ω Ω ∂
∂+
γ⎟⎟⎠
⎞⎜⎜⎝
⎛−=
c c
dt
ASndi
Snu z
c
c
c
c vv2
2
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Computations of Electromagnetic and Magnetic Field Distributionsgives possibility of
1. Determining the Equivalent Circuit Parameters
The Equivalent Circuits of Current and Voltage Transformers
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04 http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
.Magnetic flux density distribution of leakage flux of a voltage
transformer 100VA and ratio15: / 0.1: kV33
Consider this example where the value of total leakage reactance obtained based on field computation equals 0.187Ω and the value obtained by testing on a real life model is 0.190Ω.
mr z 2
2m
2 wX = L = I
ω ω dv 21=dv
21=w
V
B
0m ∫∫ ⋅⎮
⌡
⌠⎟⎟⎠
⎞⎜⎜⎝
⎛⋅
VBHBH
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Computations of Electromagnetic and Magnetic Field Distributionsgives possibility of
2. Choosing an Optimal Design Version
protective coremodel 2model 1
measuring coremodel 1model 2
Distribution of magnetic flux density [T] along the axis passing through the centres of cores for both models
http://webs.uvigo.es/arwtr04
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Distribution of magnetic flux density [T] of leakage flux at the surfaces passing through the centres of cores for two models of a current transformer 50A/5A/5Aa) model 1 b) model 2
a) b)
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
http://
webs.uvig
o.es/arwtr0
4
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wtr04
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Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
The best version is when the core with wound measuring winding is inside and the core with protective winding is outside, which shields the inner winding from the influence of the magnetic flux of the return conductor. Also the instrument security factor KFS is better in this version of the current transformer. The test results are a confirmation of the results of the numerical analysis.
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
HV current transformer 2kA/1A1- primary winding type U, 2- cores with secondary windings, 3- housing,4- paper-oil insulation, 5-oil
A-A
Computations of Electromagnetic and Magnetic Field Distributionsgives possibility of
3. Selection of ShieldsThe aim of using shields is elimination of
influence of the magnetic flux of the return conductor
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Distribution of magnetic vector potential in A-A cross-section of HV current transformer with the application of:
b) the open copper electromagnetic shield(Amax=1,7510-3Wb/m, Amin= -1,3910-3Wb/m),
a) the closed magnetic shield (Amax=1,1810-2Wb/m,
Amin= -2,4310-3Wb/m),
c) the closed steel electromagnetic shield (Amax=2,0510-3Wb/m, Amin= -2,6610-3Wb/m)
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Distribution of the normal component of magnetic flux density along symmetry axis inside the housing of a HV current transformer with the application of: 1- the closed magnetic shield,2- the open copper electromagnetic shield,3- the closed electromagnetic shield made of constructional steel.
Finally an open electromagnetic shield, made from copper, was applied.Because electromagnetic steel shield caused larger power losses in the housing (489.4 W/m and 112.1W/m at the open copper electromagnetic shield)
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
The Field-and-Circuit Method is the most direct method of determining the Characteristics of Current Error and Phase Displacement
0 20 40 60 80 100 120I/In (%)
-0.40
-0.30
-0.20
-0.10
0.00
I (%)
1
2
3
4
∆
0 20 40 60 80 100 120I/In (%)
-0.40
-0.30
-0.20
-0.10
0.00
I (%)
1
2
3
4
∆
0 20 40 60 80 100 120I/In (%)
0.00
2.00
4.00
6.00
8.00
10.00
i (min)
1
2
3
4δ
a) b)
0 20 40 60 80 100 120I/In (%)
0.00
2.00
4.00
6.00
8.00
10.00
i (min)
1
2
3
4δ
Comparison of the current error and the phase displacement characteristics of a 5A/5A current transformer fora) S=Sn =10VA, cosϕ=0.8 b) S= 2.5VA, cos ϕ =0.8obtained using: 1– the field method to determine the parameters of the equivalent circuit of the current transformer and solving a non-linear circuit, 2– the analytic method, 3 – the measurement and 4– using the field-and-circuit method.
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
The Field-and-Circuit Method application also makes it possible to determine the Composite Error (Instrument Security Factor KFS and the Accuracy Limit Factor KAF )
( )2 02 1
1 10
I100% 1= = 100%I I
t
ni K i dtT
ε − ⋅∫
Distribution of magnetic vector potential A in a current transformer 5A/5Aa) at rated state I1 = I1n (Amax=2,010-3Wb/m, Amin= -1,710-3Wb/m)
b) at overcurrent state with rated burden I1 = 157A (ε=10) (Amax=6,010-3Wb/m, Amin= -3,810-2Wb/m)
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
htt
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Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
0 50 100 150 200
I [A]
5
15
25
35
0
10
20
30
ε [%]
1I 1N10
.
The composite error vs. the primary current of a laboratory model 5A/5A current transformer, at an overcurrent state, obtained on the basis of field-
and-circuit calculations –determining the accuracy limit factor KAFL at composite error ε=10% (I1=157A therefore KAFL=31,4)
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Space-Time 2D analysis allows the computation of a break in the secondary circuit of a current transformer (Peak Values of the Secondary Voltage)
2 6 10 140 4 8 12 16
t [ms]
-0.2
0.2
0.6
-0.4
0.0
0.4
0.8
[Wb]
-250
250
750
-500
0
500
1000
u [V]Ψ 2
2u
Flux and secondary voltage vs. time, at an open secondary circuit and rated primary current, calculated for a laboratory model 5A/5A current transformer (core losses taken into account)
tdd =u2Ψ
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
http://webs.uvigo.es/arwtr04
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Peak values of the secondary voltage, determined on the basis of a field analysis and calculated using approximate formulas
based on the field analysis
V V V
918.0 2412.2 1414.2
u
1+
z2s max≈⎛
⎝⎜
⎞
⎠⎟
′′1 2
2 22
1ω
µ ωµL
R
Sl
I
Fe
Fe
Fe u 2s ≈ 2 100
2
SI kl
n
n .
http://webs.uvigo.es/arwtr04
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Joining the Field-and-Circuit Method and Space -Time Analysis permits the determination of the operation of protective current transformers during transient state (Instantaneous Error Current vs. Time )
coreprimary bar
secondary windinggap
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Distribution of magnetic vector potential A of toroidal protective current transformer 600A/1A at transient state for primary currenti1=8(cos314,16t-e-20t)kA and time t=5ms
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
-10
0
10
20
30
40
0 0,05 0,1 0,15 0,2
Instantaneous error current vs. time of toroidal protective current
transformer 600A/1A at saturation state
Primary and secondary currents vs. time of toroidal protective current
transformer 600A/1A at saturation state1- primary current
i1=8(cos314,16t-e-20t)kA in terms of secondary winding
2-secondary current-40
-30
-20
-10
0
10
20
0 0,05 0,1 0,15 0,2
1
2
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
A MATHEMATICAL MODEL
The electric field in an insulation system (after introducing the scalar electric potential
E = -∇V where E is the electric field strength) is described by the Laplace's equation
∇2 V = 0
with Neuman's and Dirichlet's boundary conditions.
The boundary conditions are: values of potential (Dirichlet's), and the condition of the
tangential electric field strength (Neuman's ) at the boundary of the whole system with
the surrounding air.
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
1. Choosing of Design Version of an Insulation Systemof HV Voltage Transformer
Computation of Electric Fields Distributions gives possibility of
Distribution of the electric potential [V] in the insulation
system of the HV voltage transformer 110: kV/100: V 3 3
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
. Distribution of the electric field strength [V/mm] in the core window of HV voltage transformer
In paper-oil nearby edge
of the primary coil
In paper-oil nearby edge of the secondary
coil
In transformer oil
Area where electric field
strength exceeded 5kV/mm
8,89kV/mm 6,70kV/mm 3,17kV/mm 42,5mm2
.Maximum values of the electric field strength in paper-oil and in oil insulation in considered voltage transformer
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
2. Improvement of the Electric Strength of an Insulation System of a Medium Voltage Instrument Transformer
Computation of Electric Fields Distributions gives possibility of
epoxide resin
trivolton
core
secondary windings
bolt
A
A
A-A voltageterminal
The constructional variant of the voltage transformer 15kV/100VEvery construction improvement is carried out in order to obtain a better device. For the voltage transformer it means achieving a greater rated power at the same accuracy class and greater electric strength at the assumption of the same external dimensions.
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04 htt
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Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
under test conditions (38kV-1 minute) under operating conditions
Distribution of electric potential [V] at the surfaces passing through the centres of the voltage transformer after redesign
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
http://webs.uvigo.es/arwtr04 http://webs.uvigo.es/arwtr04
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
.Distribution of the electric field strength [V/mm] in the area of the voltage transformer after redesign under test conditions (38kV-1 minute)
Because of the definition of the picture, the field distribution ispresented at the assumption of the upper limit 8kV/mm.
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
http://webs.uvigo.es/arwtr04 http://webs.uvigo.es/arwtr04
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Distribution of the electric field strength [V/mm] in the area of the voltage transformer after redesign under operating conditions
Because of the definition of the picture, the field distribution ispresented at the assumption of the upper limit 3kV/mm.
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
http://webs.uvigo.es/arwtr04 http://webs.uvigo.es/arwtr04
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Computation of Electric Fields Distributions gives possibility of
HV voltage transformer 110: kV/100: V 1- core, 2-grounded shield 3- HV shield 4-foil 5-secondary coil 6-housing 7-cover
3 3
3. Selection of Electric Shields
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
htt
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Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
. Distribution of electric potential [V] in insulation of HV voltage transformer when grounded shield has radius a) 190mm, b) 147mm, c) without shield
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
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Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Distribution of electric potential [V] in insulation of the last design version of HV voltage transformer
Radius of grounded shield Area where electric field strength exceeded 8kV/mm
Maximum values of the electric field strength
190mm 79,6mm2 15,8kV/mm
147mm 23,3mm2 15,2kV/mm
0mm 11,4mm2 14,5kV/mm
Table III. Maximum values
of the electric field strength in
insulation of voltage
transformer
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
htt
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http://webs.uvigo.es/arwtr04
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
4. Design of an Insulation System with Capacitance Control Computation of Electric Fields Distributions gives possibility of
main shields
intermediate shields
FIELD DISTRIBUTIONS
SHIELDSOPERA3D
capacitance
potentialsThe commercial software OPERA3Dwas used to compute field distribution and the author’s software SHIELDSwas used to optimise the number, dimensions and position of each electrostatic control shields in the insulation. Both programs interact with each other.
∫⋅
=v
e dvW2
ED2
2UWC e=
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
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Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Distribution of the electric potential along the height of the ceramic insulator
of the ceramic insulator of the combined instrument transformer
with capacitance control of the current and voltage parts in the axis direction and in the radius direction
Distribution of the electric field strength [V/mm] in the insulation system
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
htt
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http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
5. Design of an Insulation System of the HV Combined Instrument Transformers
Computation of Electric Fields Distributions gives possibility of
Computing the electric strength of this insulation system of combined instrument transformers creates many problems. All these problems are connected and one modification in the design produces, out of necessity, other modifications. The results of mutual interaction are field distributions in the whole insulation system of the combined instrument transformer computed for the final version of design.
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
of the casing with cores
Distribution of the electric field strength [V/mm] in the insulation systemof the current part of the combined transformer
of the pipe with the endings of the secondary windings in the place where the shields begin
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
of the HV voltage coil
Distribution of the electric field strength [V/mm] in the insulation systemof the voltage part of the combined transformer
of the of lead conductor of HV coil in the place where the shields begin
The designed prototype of the combined transformer successfully passed all HV tests.
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
http://webs.uvigo.es/arwtr04
htt
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/web
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Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Application of the Field Method permits the determination of thecoupling parameters (Mutual Reactance MUI and Mutual Capacitance CUI (Inner Electromagnetic Compatibility)
Circuit model of couplings in a combined transformer
Where: CUI - mutual capacitance (coupled by the electric field), MUI -mutual reactance (coupled by the electromagnetic field), ZU, ZI- the burdens of the secondary windings of the voltage and current transformer
UI 22 eW
CU
= IUm UI
ψX = ωM = ω 2 I
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
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Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
The location of the endings of the secondary windings of the current transformer nearby the voltage transformer core in the bottom part of the housing
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
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wtr
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tr04
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Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Distribution of the magnetic flux density [T] in the core of voltage part of the combined instrument transformer caused by secondary currents of the current parts.
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
http://webs.uvigo.es/arwtr04
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Distribution of the electric field strength [V/mm] in the area of the ceramic insulator, where the electric shields end
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
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p:/
/web
s.uvi
go.e
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Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
The variation of current error
±εi
The variation of voltage error
±ε v
results of computing 0.033 % 0.004%
test results 0.034% 0.02%
Prevention of possible couplings before making the prototype is simpler and less expensive than the elimination of interference during the operation of individual instrument transformers caused by placing them in the same case.
The mutual inductance MIU and the mutual capacitance CUI are very small for the final construction of the combined instrument transformer after limited mutual influences and equal to 0.12µH and 1.95pF respectively.
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
http://webs.uvigo.es/arwtr04
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
Analysis of physical field distribution using accurate numerical methods gives wide possibilities especially for constructors of precision electrical devices, which require very high accuracy. By applying the field method, the constructor is able to predict all steady state and transient parameters of the designed device before making a real life prototype. In the case of instrument transformers, it is very important to accurately compute the field distribution.
The tests on the real-life model are very expensive so it is vitally important to carry out careful experimentation using computer software first to perfect the design prior to building and testing real-life models.
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
HV Combined Instrument Transformer
HV SF6 Voltage Transformer
Medium Voltage Voltage Transformer
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
htt
p:/
/web
s.uvi
go.e
s/ar
wtr
04
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04
Department of Applied Electrical Engineering & Instrument TransformersTechnical University of Lodz
ARWtr 2004 Lecture: APPLICATIONS OF THE FIELD ANALYSIS DURING DESIGN PROCESS OF IT by E. Lesniewska
Modern TransformersARWtr 2004 28 -30 October. Vigo – Spain http://webs.uvigo.es/arwtr04