U.S. patent application number 10/300770 was filed with the patent office on 2004-02-05 for superconducting power cable with enhanced superconducting core.
Invention is credited to Alfonso Perez, Sanchez, Jose Luis Nieto, Sanchez, Mauro Eduardo Maya, Mendez.
Application Number | 20040020686 10/300770 |
Document ID | / |
Family ID | 32464651 |
Filed Date | 2004-02-05 |
United States Patent
Application |
20040020686 |
Kind Code |
A1 |
Alfonso Perez, Sanchez ; et
al. |
February 5, 2004 |
Superconducting power cable with enhanced superconducting core
Abstract
Enhanced superconducting power cable of at least one phase,
characterized by two tubular sections, the first section being a
flexible superconducting core, with a stainless steel tape mesh and
copper tape layers overlaid at an angle of 0.degree. to 45.degree.
followed by two or more superconducting material layers placed
overlaid and a second application of two or more superconducting
material layers in opposite direction with regard to the previous
ones; the second tubular section is an annular space of vacuum
thermal insulation formed by a flexible corrugated pipe covered
with multilayer insulations, including also a pipe with a stainless
steel mesh to adhere an internal semiconducting shield made of
polyethylene with insulation followed by a second metal shield
based on copper tapes and a polyethylene protecting cover.
Inventors: |
Alfonso Perez, Sanchez;
(Queretaro, MX) ; Jose Luis Nieto, Sanchez;
(Queretao, MX) ; Mauro Eduardo Maya, Mendez;
(Queretar, MX) |
Correspondence
Address: |
JONATHAN E. GRANT
2120 L STREET, N.W.
SUITE 210
WASHINGTON
DC
20037
US
|
Family ID: |
32464651 |
Appl. No.: |
10/300770 |
Filed: |
November 21, 2002 |
Current U.S.
Class: |
174/155 |
Current CPC
Class: |
H01B 12/12 20130101;
Y02E 40/642 20130101; Y02E 40/647 20130101; Y02E 40/60 20130101;
Y02E 40/641 20130101; H01B 12/06 20130101; Y02E 40/645 20130101;
H01B 12/02 20130101; H01B 12/16 20130101; H01B 12/14 20130101 |
Class at
Publication: |
174/155 |
International
Class: |
H01B 017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 1, 2002 |
MX |
PA/A/2002/007435 |
Claims
1. A superconducting power cable with enhanced superconducting core
of al least one phase with cooling through nitrogen flow in the
cavity of the central pipe, characterized because it has two
tubular sections, being the first one a flexible superconducting
core formed by a corrugated central pipe covered with a stainless
steel tape mesh, layers of copper tapes overlaid at an application
angle at 0.degree. to 45.degree., two or more overlaid layers of
superconducting material tapes with a cabling lay length of 2 to
300 cm and path angle between 0.degree. to 45.degree. to the right
or left and then application of a second section of two or more
superconducting materials layers applied in opposite direction to
the path of the above mentioned layer section, being the previous
assembly wrapped with an insulating material tape; the second
tubular section is an annular space of vacuum thermal insulation
protecting the central core and concentrically formed by a
stainless steel flexible corrugated pipe as internal wall which is
lined on the opposite wall with a multilayer thermal insulation,
then said vacuum space is completed with a stainless steel
corrugated additional pipe in the external wall of which stainless
steel mesh is placed for the adherence of several layers; said
several layers are formed by an internal semiconducting shield made
of thermoplastic o thermosetting low density polyethylene, a
polyethylene electric insulation, a second semiconducting shield, a
metal shield made of copper tapes, and a polyethylene protecting
cover.
2. The superconducting power cable of claim 1, characterized
because the first flexible corrugated pipe forming the vacuum
annular space is made of 304 or 316 stainless steel and has an
external diameter of 6 to 8 cm and an internal diameter of 4 to 5
cm, the corrugation depth can vary between 0.5 and 1 cm and the
corrugation pitch is from 1 to 2 cm for a depth between 0.5 and 0.8
cm.
3. The superconducting power cable of claim 1, characterized
because the thermal insulation placed in several layers is an
aluminum and mylar sheet 0.0005 to 0.005 cm thick.
4. The superconducting power cable of claim 1, characterized
because the second 304 or 316 stainless steel corrugated pipe has
an external diameter between 8 and 10 cm and an internal diameter
between 6 and 7 cm, with a corrugation depth between 0.5 and 1.5
cm, and a pitch between corrugations of 1 to 2 cm for a depth
between 0.5 and 1 cm.
5. The superconducting power cable of claim 1, characterized
because the stainless steel mesh placed on the corrugated central
pipe is placed in a braided way to form an external uniform flat
surface.
6. The superconducting power cables of claim 1, characterized
because the first semiconducting shield is made of thermoplastic or
thermosetting low density polyethylene, wherein the conductivity of
this layer does no exceed 1000 .OMEGA. m at room temperature and
has a thickness of al least 0.006 cm.
7. The superconducting power cable of claim 1, characterized
because the electric core insulation is based on thermoplastic or
thermosetting or crossed chain low, medium or high density
polyethylene and/or ethylene propylene, its thickness depending on
the effect of the operation voltage on the cable and being between
0.229 and 0.976 cm.
8. The superconducting power cable of claim 1, characterized
because the second semiconducting shield is made of the same
components as the first shield but its thickness is at least 0.0129
cm and its maximum volume resistivity is 500 .OMEGA. m at room
temperature.
9. The superconducting power cable of claim 1, characterized
because the metal shield of cooper tape is 0.00635 cm thick, having
a cross section area of at least 0.1 mm.sup.2/mm.
10. The superconducting power cable of claim 1, characterized
because the final protecting cover can be made of polyethylene o
polyvinyl chloride (PVC), with a thickness between 0.203 and 0.279
cm.
11. The superconducting power cable of claim 1, characterized
because the vacuum thermal insulation system functions at
temperatures of 77.degree. K. and under a vacuum pressure of 10 mPa
(milliPascal).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The instant invention relates to the conduction of electric
power and particularly to the manufacturing of a superconducting
power cable of at least one phase, characterized by a central core
based on a superconducting tape material BSCCO of 22233 (Bi.sub.2
Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.x) commercial composition giving a
minimum current density of 7 KA/cm.sup.2 under the criteria of 1
.mu.V/cm. It also includes an annular space of thermal insulation
system wherein the corrugated casing of the system presents a
vacuum pressure below 10 mPa (milliPascals) permitting the thermal
insulation to maintain operating temperatures of 77.degree. K.
(temperature of liquid nitrogen under atmospheric pressure)
throughout the cross section of the cable in its superconducting
part.
[0003] 2. Previous Art
[0004] The invention relates to the transportation of electric
power in superconducting conditions, zero resistance in direct
current. This invention replaces the use of power cables for
distribution and transmission in voltages from 15 kV upwards
because it presents lower conduction losses. High temperature
superconductors can be important aspects of technological advances,
because equipment and devices could have superconducting parts in
their components. An obvious application in superconducting state
is the use of zero resistance properties to the passage of direct
current and low power losses in the electricity transmission. In
the present transmission lines, electric power is lost through heat
when the current passes through normal conductors. If electricity
is transmitted through superconducting cables, said losses can be
reduced or eliminated with the subsequent savings in the energy
costs. This can be applied to any electric component having cooper
leads, for examples, motors, transformers, generators and any
equipment involved with electric power.
[0005] Some US and Japanese companies have manufactured and
evaluated superconducting cable models of up to 5000 cm obtaining
current values not exceeding 1700 A to 2000 A. Tests conducted in
5000 cm long segments have shown problems related to current
distribution among layers. Said distribution tends to be irregular
because of electromagnetic problems related to the lead itself.
[0006] Patent WO 00/39813 describes a superconducting cable using
high temperature superconducting materials HTS with flexible core.
However it applies to a traditional coaxial design with insulated
HTS tape layers and cold design.
[0007] Japanese Patent 06239937 A2 describes a superconducting
cable with HTS materials and flexible core but involving a
traditional DC (direct current) design and insulation between each
HTS tape layer.
[0008] U.S. Pat. No. 5,929,385 describes a superconducting cable
similar to the object of the instant invention but only as far as
the type of materials used is concerned. U.S. Pat. No. 5,952,614
also describes a superconducting cable similar as far as the use of
HTS materials and flexible core are concerned but with a coaxial
design, in cold conditions and with HTS tape traditional design.
For these reasons, said inventions are different from the
characteristics of the instant invention.
DESCRIPTION OF THE INVENTION
[0009] Hereinafter the invention will be described in connection
with the drawings of FIGS. 1 to 6, wherein:
[0010] FIG. 1 is a perspective view with cross section showing the
different layers of the superconducting power cable.
[0011] FIG. 2 is a cross section view of FIG. 1.
[0012] FIG. 3 is a perspective view with cross section of the
vacuum section of the central core thermal protection.
[0013] FIG. 4 is a perspective view with cross section of FIG. 3
showing the opposite wall of the thermal insulation.
[0014] FIG. 5 is a perspective view with cross section of the
superconducting power cable core.
[0015] FIG. 6 is a perspective view with longitudinal cross section
of FIG. 1, showing the annular space of thermal insulation.
[0016] The invention is related to the transportation of
electricity in superconducting conditions, (zero resistance in
direct current). This invention replaces the use of power cables
for distribution and transmission in voltages of 15 kV or more
because it presents lower conduction power losses, considering that
for a Cu lead with a current density of 1-4 A/mm.sup.2 and a
resistivity of 2.times.10.sup.-8 .OMEGA.m, the transmission losses
are on the order of 20-80 mW/Am. To better compare with
superconducting cables, losses caused by the heating of
superconducting materials have to be taken into account. At
cryogenic temperatures, said losses are defined by a Carnot factor
divided between the efficiency of the cooling system. In the case
of liquid nitrogen, this factor is between 10 and 20. Thus, in a
superconductor losses will be lower than 5 mW/Am. The flow of
liquid nitrogen fills the longitudinal cavity 21, FIG. 5, of the
flexible corrugated pipe 1 of 304 or 316 stainless steel. Said pipe
can have an external diameter between 2 cm and 6 cm and an internal
diameter between 1 cm and 4 cm wherein the depth of the corrugation
can vary between 0.5 cm and 1 cm. The corrugation pitch can be
between 0.8 and 1.5 cm for a corrugation depth between 0.4 and 0.5
cm. As another alternative for a depth between 0.4 and 0.6 cm, the
corrugation pitch can be between 1.6 and 3 cm. On this pipe, a 304
or 316 stainless steel mesh is placed in order to obtain a
relatively flat surface. On this mesh a stainless steel tape layer
2 is placed, between 4 and 5 cm wide and between 0.0005 and 0.006
thick. They are placed on the corrugated pipe with spacing between
0.15 and 0.2 cm. Then one or two additional stainless steel tapes,
2.5 to 4 cm wide and 0.001 to 0.002 cm thick, are placed with
spacing between the tapes of 0.1 to 0.15 cm. After, a fist layer of
Cu tapes 3 is placed, from 0.25 to 0.40 cm wide and from 0.025 to
0.030 cm thick, with a cabling length between 2 cm and 100 cm
depending on the design of the first layer of superconducting tapes
to be applied. Said layer of Cu tapes can be laid at an angle
ranging from 0.degree. to 45.degree. depending on the cable design.
The superconducting material to be used is made of tapes of a 22233
(Bi.sub.2 SR.sub.2 Ca.sub.2 CU.sub.3 O.sub.x) composition
commercial product BSCCO. Said tapes range in width between 0.38
and 0.42 cm and in thickness between 0.018 and 0.022 cm, which
gives a minimum current density of 7 kAcm.sup.2 under the criteria
of 1 .mu.V/cm, (microvolt/centimeter) . With this superconducting
material, two or more layers of tapes are laid with a cabling lay
length between 20 cm and 300 cm, at an angle ranging from 0.degree.
to 45.degree. depending on the design of each layer with a
direction that can be right or left 4, 5, 6. And two or more layers
of superconducting material tape with a lay length between 20 cm
and 300 cm with an angle ranging from 0.degree. to 45.degree.
depending on the design of each layer with a direction that can be
right or left with regard to the cabling, in the opposite direction
of the previously placed layers 7, 8, 9. Finally, a wrapping tape
made of insulating material 10, with a thickness ranging between
0.005 and 0.01 cm and a width ranging between 2 and 4 cm is
laid.
[0017] In order to protect the central core, the superconducting
power cable object of the instant invention is also characterized
because it includes a vacuum thermal insulation system consisting
of a flexible corrugated pipe 11 made of 304 or 316 stainless
steel, to hold the superconducting cable and liquid nitrogen. Said
pipe can have an external diameter ranging between 4 cm and 8 cm
and an internal diameter ranging between 3 cm and 7 cm, the
corrugation depth varying between 0.5 cm and 1 cm. The corrugation
pitch can vary between 1 cm and 2 cm for a corrugation depth
between 0.5 and 0.8 cm. Then, on the periphery of this pipe, a
multi layer thermal insulation (.rho..sub.a) 12 is applied, which
can have a thickness ranging between 0.0005 cm and 0.005 cm which
is calculated according to the following formula:
.rho..sub.a=(S.sub.s+.rho..sub.rt.sub.r)(N/.DELTA.x)
[0018] wherein:
1 .rho..sub.a Thickness of the insulating layer S.sub.s Mass of the
material per area unit .rho..sub.r Insulating material density
t.sub.r Thickness of the anti-radiation casing N/.DELTA.x Layer
density
[0019] Concentrically around the flexible corrugated pipe 11,
covered with the insulating material 12, a second corrugated pipe
13 is placed, creating the vacuum thermal insulation space 20, FIG.
6.
[0020] To ensure the adequate functioning of the thermal insulation
system at a temperature of 77.degree. K., a vacuum pressure below
10 mPa (milliPascals) is required.
[0021] Said second corrugated pipe 13, which creates the vacuum
space, is made of 304 or 316 stainless steel which can have and
external diameter ranging between 8 cm and 10 cm and an internal
diameter ranging between 6 and 7 cm, wherein the depth of the
corrugations may vary between 0.5 cm and 1.5 cm. The corrugation
pitch can be between 1 and 2 cm for a corrugation depth between 0.5
and 1 cm.
[0022] The thermal insulation system includes also on the external
wall of the corrugated pipe 13, a braided stainless steel mesh 14,
FIGS. 1 and 3, offering a uniform surface to the external wall
structure of the helical or spiral shaped corrugated pipe.
[0023] Around the uniform mesh surface 14, an internal
semiconducting shield 15 is applied, which is made of low density
thermoplastic polyethylene or any other thermoplastic or
thermosetting semiconducting material. The conductivity of said
shield should not exceed 1000 .OMEGA. m when it is measured at room
temperature, said shield having a thickness of at least 0.006 cm.
On this semiconducting shield the electric insulation of the cable
16 is placed. Said electric insulation is based on low, medium or
high density, thermoplastic or thermosetting or crossed chain
polyethylene and/o Ethylene Propylene (EP), the thickness of the
insulation being between 0.229 cm and 0.876 cm depending on the
operation voltage level of the cable. On this electric insulation,
a second semiconducting shield 17 made of the same materials as the
internal semiconducting shield 15 is placed, FIG. 4. However, in
this case, the thickness of the shield must be at least 0.0127 cm
and has to fulfill a maximum volume resistivity of 500 .OMEGA. m
when measured at room temperature. On this layer, a metal shield
made of Cu tape 18 is placed, which must be at least 0.0635 cm
thick, having a cross section area of at least 0.1 mm.sup.2/mm. On
this metal shield 18, a protective casing 19 is placed, possibly
made of polyethylene or polyvinyl chloride (PVC) depending on the
application of cable, said casing having a thickness ranging
between 0.203 and 0.279 cm.
[0024] According to the technical requirements, the basic
superconductor design parameters used were as follows:
[0025] Tape Width (cm): 0.4.+-.0.02
[0026] Tape Thickness (cm): 0.02.+-.0.002
[0027] Critical current Density (kA/cm.sup.2)>7 (criterion of 1
.mu.V/cm)
[0028] Filamentary section thickness inside the tape 2b.sub.sc
(cm): 0.018
[0029] Critical current in the bending deformation voltage value:
0.1%--not below 95% or 0.2%--not below 90%.
[0030] About 20% reduction in the critical current when the field
is between 0T and 0.1T.
[0031] The basic equations to compute the number of superconducting
tapes and the design parameters are as follows:
[0032] Number of tapes per layer (Ni) 1 Ni = xDiox COS i 2 ai ( 1 +
Si )
[0033] wherein:
[0034] D.sub.io=average diameter of the i layer
[0035] 2.sub.ai=Tape Width of the i layer
[0036] S.sub.i=Relative space between the tapes of the i layer
[0037] .beta..sub.i=Laying angle of the superconducting tapes
[0038] Lay of the tapes in a layer (Pi) 2 Pi = xDio tan i
[0039] Relative spacing between the tapes of a layer: (Si) 3 Si =
xDiox Cos i 2 aixNi
[0040] Relative deformation voltage .epsilon..sub.i regarding the
superconductor in bending conditions of the tapes is:
.epsilon..sub.i=2bscx sen.beta./Dio
[0041] The model base of the superconducting high temperature cable
has been developed, which consists of the design of the
superconducting core itself, as well as the development of
insulation based on known and previously developed materials for
use in medium and high voltage power cables.
EXAMPLE 1
[0042] Under the design conditions, the superconducting tape VAC
(Germany) was chosen. Said tape presents a critical current of 59.8
A to 64.7 A depending on the combination of thickness and width of
the superconducting tape. Based on these variations, the criteria
of linearity of the critical current density used for the cable
optimization and calculation is not very congruent, and thus a
value of the critical current density in the external magnetic
field equals to cero is accepted as 113 A/cm for cable
calculations. Taking into account said variations, the followings
values were taken as parameters for the calculation.
[0043] External Diameter of the core D.sub.fe=5.5 cm;
[0044] Tape thickness 2b.sub.t=0.002 cm;
[0045] Filament section thickness inside the tape 2b.sub.sc=0.018
cm;
[0046] Relative space between each tape in each layer S=0.05.
[0047] The minimum lay of the tapes (maximum angle of tape laying)
is selected based on the limitations imposed by the deformation
voltage threshold with regard to bending, for a superconductor when
the tapes in one layer are bent on a diameter D.sub.1 and the tape
laying angle .beta..sub.i is at a maximum permissible value
(.epsilon.<0.2%, wherein .epsilon.=2.sub.sc cos
.beta..sub.i/D.sub.1) . The critical current of the cable is
expected to be between 6 kA and 10 kA, under the criteria of 1
.mu.V/cm and the approximate values of the magnetic field induction
on the surface of the sixth layer being between 0.04 T and 0.07 T.
For this reason for every 0.001 T increase, the critical current
reduction of the tape is expected to be 2% its initial value.
[0048] The influence of the deformation voltage on the
superconductor with regard to the value of the tape critical
current during the manufacturing of cable is described in the
comments on Table No. 1.
2TABLE NO. 1 Expected manufacturing results (2.sub.a = 0.38 cm,
2b.sub.sc = 0.018 cm) Layer D.sub.i I.sub.c I.sub.maxi Num- Bending
.epsilon. Tape I.sub.ci REAL S.sub.i ber Mm % N.sub.i A A
I.sub.ci/I.sub.co A Real 1 13.32 0.135 40 42.22 1688.8 0.1667
1672.3 0.0377 2 17.52 0.103 42 41.54 1744.7 0.1722 1727.6 0.0399 3
42.03 0.043 44 40.85 1797.4 0.1771 1779.8 0.0446 4 51.72 0.035 45
40.17 1807.7 0.1784 1790.0 0.0325 5 15.82 0.114 42 39.49 1658.6
0.1637 1642.3 0.0457 6 9.97 0.181 37 38.80 1435.6 0.1417 1435.6
0.0484 .SIGMA. 10132.8 1 10047.6
[0049] According to the above table, it can be seen that the
current value depends on the maximum deformation voltage if and
only if it does not exceed the deformation value of 0.2% which is
the critical value of the current. From the results obtained in the
above table, we observe that there is uniform current distribution
in every layer, which gives a current distribution factor
I.sub.ci/I.sub.co=1 and a real maximum critical current value of
I.sub.MAX REAL=10047 A.
EXAMPLE 2
[0050] However, in Table No. 2, the optimization results of the
cable are presented as the criteria to reach the peak critical
current value and the minimization of the energy losses under the
influence of the flow and axial magnetic field.
3TABLE NO. 2 Optimization Results Tape Layer D.sub.i laying Num-
Exterior direc- J.sub.ct .beta..sub.i P.sub.f I.sub.calc ber Cm
tion A/cm degrees cm I.sub.i/I.sub.o J.sub.i 1 5.554 L/1 111.11
24.6 37.89 0.1671 1.0000 2 5.588 L/1 109.31 18.6 51.96 0.1716
0.9938 3 5.632 L/1 107.51 7.70 130.35 0.1765 0.9859 4 5.676 R/-1
105.71 6.30 160.89 0.1769 0.9941 5 5.720 R/-1 103.91 21.2 46.15
0.1648 0.9967 6 5.764 R/-1 102.11 35.3 25.48 0.1431 0.9985 .SIGMA.
5.764 1.0000 0.9948
Maximum current reached I.sub.MAX=10028.5
Total sum of the utilization coefficient in the six layers
K.sub.MAX=.SIGMA..sub.J1=5.96689
[0051] And according to the above mentioned criteria, current
distribution is uniform in all the cable layers, and the losses
caused by the axial magnetic field are minimized.
[0052] Wherein:
[0053] D.sub.i exterior=external diameter of the i layer
[0054] J.sub.ci=Density of the lineal critical current for the
tapes of the i layer
[0055] .beta..sub.i=Tape laying angle for the tapes of the i
layer
[0056] P.sub.i=Tape lay for the tapes of the i layer
[0057] N.sub.i=Number of tapes in the i layer
[0058] I.sub.ci=Total critical current of all the tapes in the i
layer (current i layer) versus the total number of tapes (sum of
the critical currents of all the tapes) in the model.
[0059] I.sub.calc=I.sub.i/I.sub.o Current distribution in the i
layer of the total current.
[0060] N.sub.1/N.sub.o=I.sub.ci/I.sub.co=Number of tapes in the i
layer (critical current in the i layer) versus the total number of
tapes (sum of the critical currents of all the tapes) in the
model.
[0061] I.sub.maxREAL=Real value of the current peak in the i layer
when the current reaches its critical value in at least one of the
layers.
[0062] J.sub.i=Superconductor utilization coefficient in the i
layer.
* * * * *