FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A modular plate type resistive superconductor fault current limiter equipment and assembly
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worii, Mumbai 400 030, Maharashtra, India; an Indian Company; AND Central Power Research Institute (CPRI), Prof Sir C.V. Raman Road, P.B. No: 8066, Sadasiva Nagar Post Office, Bangalore 560 080, Karnataka, India; an autonomous society under Ministry of Power, Government of India.
INVENTORS
Dixit Manglesh, Lobo Anthony Marcel, Kulkarni Sandeep and Sukali Ramesh all of Crompton Greaves Limited, Medium Voltage Product Technology Centre (MVPTC), Global R&D Centre, Kanjurmarg (East), Mumbai - 400042, Maharashtra, India; all Indian Nationals.
PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the nature of this invention and the manner in which it is to be performed.

FIELD OF THE INVENTION:
This invention relates to the field of electrical and electronic components and assemblies.
Particularly, this invention relates to a current limiter.
More particularly, this invention relates to a superconductor fault current limiter.
Specifically, this invention relates to a modular plate type resistive superconductor fault current limiter equipment and assembly.
BACKGROUND OF THE INVENTION:
A Fault Current Limiter (FCL) is a device which limits the prospective fault current when a fault occurs in a power transmission and distribution network. It serves to limit mechanical, thermal, and electrical stresses applied to mechanical and electrical components of an electric power system when a fault current such as a short circuit, a ground fault, and a lightning strike occurs.
Current limiting devices are critical in electric power transmission and distribution systems. A current limiter is designed to react and absorb unanticipated power disturbances in a utility grid, preventing loss of power to customers or damage to utility grid equipment.
The concept of using the superconductors to carry electric power and to limit peak currents has been around since the discovery of superconductors and the realization that they possess highly non-linear properties. More

specifically, the current limiting behavior depends on their nonlinear response to temperature, current and magnetic field variations. Superconductivity is a phenomenon of exactly zero electrical resistance occurring in certain materials below a characteristic temperature.
The superconducting fault current limiter may be of an inductive type or of a resistive type. In a resistive FCL, the current passes through the superconductor and when a high fault current begins, the superconductor quenches: it becomes a normal conductor and the resistance rises sharply and quickly. This transition of a superconductor from its superconducting state to a normal resistive state is termed "quenching."
Superconductors, especially high-temperature superconducting (HTS) materials, are well suited for use in a current limiting device because of their intrinsic properties that can be manipulated to achieve the effect of "variable impedance" under certain operating conditions.
FCLs would be installed in transmission and distribution systems for electric utilities and large energy users in high-density areas. The benefits include increased safety, increased reliability, improved power quality, compatibility with existing protection devices, greater system flexibility from adjustable maximum allowed current, and reduced capital investment because of deferred upgrades. The superconducting FCL provides the same continuous protection, with no standby energy losses due to joule heating and no voltage drop. The superconducting FCL instantaneously limits the flow of excessive current by allowing itself to exceed its superconducting transition temperature and switch to a purely resistive state, thus minimizing the fault

current that passes through it. It takes less than 2ms in detecting and limiting the fault currents.
Generally resistive SFCL are manufactured by bulk superconductors or coils of superconductor tapes. The bulk superconductor modules are fragile and are prone to damages. Also the assembly becomes bulky. HTS coils for this application have inductive effects and cannot be non-inductively wound for higher voltages. Making non-inductively coils are complicated and space consuming. This makes the SFCL configuration bulky and complicated for assembly.
However, there is a need for a SFCL which is modular and is very simple and compact.
Also, prior art SFCLs are coil type in which if the superconducting coil gets damaged during surge, the entire coil needs to be replaced. Superconducting material is expensive, and hence entire replacement is a costly proposition. There is a need for an SFCL which is relatively inexpensive in terms of replacement of superconductor material.
A resistive type superconductor fault current limiter is an intelligent and self acting device that can detect and limit fault currents level up to 80% in very short duration. It operates and limits the current within the quarter of first cycle of the fault (within 1 or 2 ms). It is invisible to the line during nominal operations and does not add reactive power losses to the system.

In today's power scenario, the generating capacity is rapidly increasing and is added in to the power systems with many interconnections. The addition of new generation and expansion of power network, has led to the threat of significant increase in fault current levels. The increase in fault current could surpass the breaking capacity of the installed circuit breakers. Conventional solutions such as bus splitting, fuses, upgradation of circuit breaker and downstream equipments, reactors and the like are available. However, they are not regarded as effective measures when reliability, stability and sustainability of power systems are considered.
Conventional solutions to cope with the fault currents also add more reactive power to the system during normal operation. Upgradation or replacement of the breakers and related downstream equipments would be expensive, time consuming and could lead to power cut for several days, affecting the economy growth.
There is a need for a smart engineering solution which is effective, reliable, and economical and maintenance free.
OBJECTS OF THE INVENTION:
An object of the invention is to provide a resistive superconductor fault current limiter.
Another object of the invention is to provide a modular type resistive superconductor fault current limiter.
Yet another object of the invention is to provide a coil free compact modular type resistive superconductor fault current limiter.

Still another object of the invention is to provide a modular assembly design for a superconductor fault current limiter which is compatible for all possible current and voltage rating.
An additional object of the invention is to provide a superconductor fault current limiter with relatively higher efficiency.
Yet an additional object of the invention is to provide a superconductor fault current limiter wherein effect of flux impact between modules is minimized significantly,
Still an additional object of the invention is to provide a superconductor fault current limiter with relatively fast current limitation capability.
Another additional object of the invention is to provide a superconductor fault current limiter with ease of manufacturing and assembly.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a modular plate type resistive superconductor fault current limiter equipment, said equipment comprises: a) plate-type substrate adapted to host a plurality of strips of superconductors linearly aligned, along the length of the plate, parallel to one another in a spaced apart manner, in that, only one strip per length is provided, in that, two adjacent strips are spaced apart in an equidistant manner through the breadth of said substrate, said substrate further including holes below the length of each of said strips in order to provide a path for liquid nitrogen flow for effective cooling;

b) plurality of operative horizontal contacts within the perimeter of said substrate, each contact adapted to connect a pair of adjacently located single strips at only one of their correspondingly adjacent axial ends, said operative horizontal contacts consisting of a first set of horizontal contacts and a second set of horizontal contacts, wherein said first set of horizontal contacts are adapted to connect an odd numbered strip to an even numbered strip starting from an operative lateral end of said substrate and are located at a first longitudinal end of the substrate and wherein said second set of horizontal contacts are adapted to connect an even numbered strip to an odd numbered strip starting from the same operative lateral end of said substrate and are located at a second longitudinal end of the substrate, thereby ensuring a U-shaped conducting path between adjacent strips and further provisioning a substantially zigzag pattern of conductors and provisioning modularity being defined by the number of said strips; and
c) a pair of end vertical terminals adapted to be connected to a first strip and an end strip, respectively, for each substrate such that it extends beyond the boundary of said substrate to provide external connections, wherein each of said end vertical terminals are located only on one side of said substrate.
Typically, said strips are high-temperature superconductivity (HTS) tapes.
Typically, said substrate is a Glass Fiber Reinforced Polymer (GFRP) plate or ceramic plate or mica plate.
Typically, breadth "width" of the strips range from about 4mm to about 12mm.

Typically, said contacts are copper horizontal end terminals with four bolts in such a way that each strip is clamped in the centre with two bolts.
According to this invention, there is also provided a modular plate type resistive superconductor fault current limiter assembly, said assembly comprises:
A. a plurality of plate type resistive superconductor fault current limiter
equipment of claim 1, each substrate having a pair of end vertical
terminals; and
B. an assembly for stacking a plurality of said equipment together, in a
spaced apart manner, to provide modular rating by adding or
removing said equipment, said assembly further comprising:
i. first end plate and an axially spaced apart second end plate wherein said first end plate is an operative top plate and the second end plate is an operative bottom plate with said plurality of stacked equipment being aligned longitudinally in the spaced apart region between said first end plate and said second end plate, said first end plate including slots such that said end vertical terminals of each equipment protrude beyond the plane of said first end plate to allow further electrical connections; ii. plurality of U-clamps, each of said U-clamps adapted to connect a pair of end vertical terminals through its pair of arms, respectively;
iii. at least an L- adapted to connect a plurality of U-clamps on one of its arms;
iv. tie rod adapted to space apart said first end plate from said second end plate; and

v. spacer tie rod and a spacer element adapted to ensure said spaced apart nature of adjacent equipment in the stack of equipment, thus ensuring pre-defined space.
Typically, said top plate is a GFRP plate
Typically, said bottom plate is a GFRP plate
Typically, said U-clamps are U-shaped copper terminals
Typically, said L-clamps are L-shaped copper terminals.
There is also provided an enclosure for said modular plate type resistive superconductor fault current limiter assembly said enclosure being a cryostat chamber with vacuum filled walls adapted to store said assembly in a liquid Nitrogen bath and including copper current leads, connected to said L-clamps, extending out of said bath and out of a top flange which covers the bath and the assembly
Typically, said enclosure includes a Liquid Nitrogen inlet for allowing input of liquid Nitrogen.
Typically, said enclosure includes a Nitrogen gas vent.
Typically, said enclosure includes level sensors to sense level of liquid Nitrogen.
Typically, said enclosure includes a temperature sensor to sense temperature within the cryostat chamber.
Typically, said enclosure includes a pressure release valve.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The invention will now be described in relation to the accompanying drawings, in which:
Figure 1 illustrates a schematic of a single plate-type resistive superconductor fault current limiter;
Figure 2 illustrates a stack of plates of Figure 1;
Figure 3 illustrates a front view of the assembly;
Figure 4 illustrates an auxiliary view of the assembly;
Figure 5 illustrates a top view of the assembly; and
Figure 6 illustrates an assembly for a SFCL in a nitrogen bath for actual use.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided a modular plate type resistive superconductor fault current limiter.
Figure 1 illustrates a schematic of a single plate-type resistive superconductor fault current limiter.
In accordance with an embodiment of this invention, there is provided a plate-type substrate (6) upon which a plurality of strips (11) of superconductors are linearly aligned, along the length of the plate, parallel to one another in a spaced apart manner. The strips are high-temperature

superconductivity (HTS) tapes. The plate is a Glass Fiber Reinforced Polymer (GFRP) plate.
In accordance with an aspect of this invention, Only one conductor per length is provided, in that, two adjacent conductors are spaced apart in an equidistant manner through the breadth of the substrate. This arrangement minimizes the heating effect at the joint of superconductor (HTS) strip to copper termination. Since HTS strip carries higher current of about 200A, more conductor in the same cross section may produce heating and temperature may increase beyond the operating temperature 77K (-196), quenching and damaging the HTS strip.
Further, the GFRP base plate has holes below the length of each of the HTS strips path in order to provide liquid nitrogen flow for effective cooling.
The breadth of the HTS strips may range from about 4mm to about 12mm.
In accordance with another embodiment of this invention, there are provided a plurality of contacts (7), each contact adapted to connect a pair of adjacently located single HTS strips at only one of their correspondingly adjacent axial ends. These contacts (7) are copper horizontal end terminals. These contacts are horizontally disposed with respect to the plate, in that, they are parallel to the plane of the plate. A first contact starting from a lateral end of the plate connects a first strip (frorn the lateral end) to a second adjacently located spaced apart spaced, thereby ensuring a conducting path between the first strip and the second strip in a U-shaped pattern. This first contact is located at a first axial end of the plate. A second contact starting from a lateral end of the plate connects a second strip (from the lateral end)

to a third adjacently located spaced apart spaced, thereby ensuring a conducting path between the second strip and the third strip in a U-shaped pattern. The second contact is located at a second axial end of the plate. Further, a third contact is located at the first axial end of the plate and is adapted to connect the third strip to a fourth strip in a U-shaped pattern. Still further, a fourth contact is located at the second axial end of the plate and is adapted to connect the fourth strip to a fifth strip in a U-shaped pattern. Thus, a first set (7a) of plurality of contacts are disposed on the first axial end of the plate and a second set (7b) of plurality of contacts are disposed on the second axial end of the plate. The first set of contacts and the second set of contacts are spaced apart by the width of the space between the HTS strips that they connect. The first set of contacts and the second set of contacts lie within the defined portion of the plate, without extending beyond its boundaries.
Due to this formation, a substantially zigzag pattern of conductors is formed. The copper clamping contacts are tightened, typically, with 4 bolts in such a way that each tape is clamped in the centre, typically, with two bolts. This gives a perfect tightening across the termination and ensures maximum contact area to the HTS strip. Also the HTS strip is sandwiched between two copper terminations / contacts.
Superconducting material is brittle. The incoming surge, which it should withstand, is a relatively high surge, typically about 10 to 20 times the normal current. The cost of superconducting material is high. Hence, even if it formed into coils, and the coil damages, replacement of coil turns out to be a substantially expensive affair. In the current invention, only a portion (strip) of the superconducting material may get damaged. Thus, only the

strip will have to be replaced, without affecting the adjacent strips, or the plate, in general.
Depending upon the rating required, the path of conduction may be elaborated i.e. more number of strips may be added in one plate. In accordance with yet another embodiment of this invention, there is provided an end vertical terminal (10) adapted to be connected to a first HTS strip and an end HTS strip for each plate such that it extends beyond the boundary of the plate to provide external connections. Both the end vertical terminals are located only on one side of the plate.
Figure 2 illustrates a stack of plates of Figure 1.
In accordance with still another embodiment of this invention, there is provided an assembly for stacking a plurality of plates (Figure 1) together to provide increased rating to a superconductor fault current limiter (SFCL). Adjacent plates are spaced apart with respect to each other.
Figure 3 illustrates a front view of the assembly. Figure 4 illustrates an auxiliary view of the assembly. Figure 5 illustrates a top view of the assembly.
In accordance with an additional embodiment of this invention, there is provided a first end plate (2) and an axially spaced apart second end plate (8) wherein the first end plate is an operative top GFRP plate and the second end plate is an operative bottom GFRP plate. The plurality of stacked plates, as seen in Figure 2, are aligned longitudinally in the spaced apart region

between the first end plate (2) and the second end plate (8). Adjacent plates are spaced apart with respect to each other. The first end plate includes slots such that the end vertical terminals (10) of each plate protrude beyond the plane of the end plate to allow further electrical connections.
In accordance with yet an additional embodiment of this invention, there is provided a plurality of U-clamps (9), each U-clamp adapted to connect a pair of end vertical terminals through its pair of arms, respectively. Particularly, the U-clamps are copper terminals. Further, there is provided at least an L-clamp (1) adapted to connect a plurality of U-clamps on one of its arms. Particularly, the L-clamps are copper terminals.
In accordance with further additional embodiments of this invention, there is provided a tie rod (3) adapted to space apart the first end plate (operative top plate as denoted by reference numeral 2) from the second end plate (operative bottom plate as denoted by reference numeral 8). There is also provided a spacer tie rod (4) and a spacer element (5) to ensure the spaced apart nature of adjacent plates in the stack of plates, thus ensuring predefined space.
Figure 6 illustrates an assembly for a SFCL in a nitrogen bath for actual use.
The SFCL module assembly (30) is seen in a cryostat chamber (31). This cryostat chamber includes vacuum filled walls (29). The SFCL module assembly (30) is immersed in a liquid Nitrogen bath (28) which is filled in the cryostat chamber (31). Liquid Nitrogen inlet for allowing input of liquid Nitrogen is shown by reference numeral 22. Reference numeral 21 refers to

a cryostat chamber top flange which covers the bath and the assembly. Reference numeral 23 refers to Nitrogen gas vent. From the L-clamps (reference numeral 1 from Figures 3, 4, and 5), copper current leads (24) extend out of the bath (28) and out of the top flange (21). Reference numeral 25 refers to level sensors to sense level of liquid Nitrogen. Reference numeral 26 refers to temperature sensor to sense temperature within the cryostat chamber. Reference numeral 27 refers to pressure release valve.
The technical advancement lies in providing a coil free compact assembly for resistive type superconductor fault current limiter. It also provides for a modular assembly design, compatible for a plurality of possible current and voltage ratings; just by increasing or removing the plate modules, various type of current and voltages ratings can be achieved. The spaces between the HTS strips provide for cooling channels and hence, higher efficiency due to cooling channels can be achieved. Every conductor surface is exposed to cryogenic fluid for effective cooling. Using this assembly, fast current limitation (1-2 ms) can be achieved. The non-inducting and coil free assembly is achieved due to parallel arrangement of conductors. The parallel arrangement in a module will have no effect of flux from other module. There is also provided an optimized design for HTS tapes performing live without damage or burnout. It is, therefore, a compact modular design for any rating of current or voltage. And it is easy for manufacturing and assembly. The amount of copper used for the formation of this modular plate type resistive superconductor fault current limiter equipment is relatively less, as compared to other prior art superconductor fault current limiters of the prior art which include two or more closely located groups of adjacent strips, resulting in lower copper losses.

While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. A modular plate type resistive superconductor fault current limiter equipment, said equipment comprising:
a) plate-type substrate adapted to host a plurality of strips of superconductors linearly aligned, along the length of the plate, parallel to one another in a spaced apart manner, in that, only one strip per length is provided, in that, two adjacent strips are spaced apart in an equidistant manner through the breadth of said substrate, said substrate further including holes below the length of each of said strips in order to provide a path for liquid nitrogen flow for effective cooling;
b) plurality of operative horizontal contacts within the perimeter of said substrate, each contact adapted to connect a pair of adjacently located single strips at only one of their correspondingly adjacent axial ends, said operative horizontal contacts consisting of a first set of horizontal contacts and a second set of horizontal contacts, wherein said first set of horizontal contacts are adapted to connect an odd numbered strip to an even numbered strip starting from an operative lateral end of said substrate and are located at a first longitudinal end of the substrate and wherein said second set of horizontal contacts are adapted to connect an even numbered strip to an odd numbered strip starting from the same operative lateral end of said substrate and are located at a second longitudinal end of the substrate, thereby ensuring a U-shaped conducting path between adjacent strips and further provisioning a substantially zigzag pattern of conductors and provisioning modularity being defined by the number of said strips; and

c) a pair of end vertical terminals adapted to be connected to a first strip and an end strip, respectively, for each substrate such that it extends beyond the boundary of said substrate to provide external connections, wherein each of said end vertical terminals are located only on one side of said substrate.
2. An equipment as claimed in claim 1 wherein, said strips are high-temperature superconductivity (HTS) tapes.
3. An equipment as claimed in claim 1 wherein, said substrate is a Glass Fiber Reinforced Polymer (GFRP) plate or mica plate or ceramic plate.
4. An equipment as claimed in claim 1 wherein, breadth of the strips range from about 4mm to about 12mm.
5. An equipment as claimed in claim 1 wherein, said contacts are copper horizontal end terminals with four bolts in such a way that each strip is clamped in the centre with two bolts.
6. A modular plate type resistive superconductor fault current limiter assembly, said assembly comprising:
A. a plurality of plate type resistive superconductor fault current limiter
equipment of claim 1, each substrate having a pair of end vertical
terminals; and
B. an assembly for stacking a plurality of said equipment together, in a
spaced apart manner, to provide modular rating by adding or
removing said equipment, said assembly further comprising:
i. first end plate and an axially spaced apart second end plate wherein said first end plate is an operative top plate and the second end plate

is an operative bottom plate with said plurality of stacked equipment being aligned longitudinally in the spaced apart region between said first end plate and said second end plate, said first end plate including slots such that said end vertical terminals of each equipment protrude beyond the plane of said first end plate to allow further electrical connections;
ii. plurality of U-clamps, each of said U-clamps adapted to connect a pair of end vertical terminals through its pair of arms, respectively;
iii. at least an L- adapted to connect a plurality of U-clamps on one of its arms;
iv. tie rod adapted to space apart said first end plate from said second end plate; and
v. spacer tie rod and a spacer element adapted to ensure said spaced apart nature of adjacent equipment in the stack of equipment, thus ensuring pre-defined space.
7. An assembly as claimed in claim 6 wherein, said top plate is a GFRP plate.
8. An assembly as claimed in claim 6 wherein, said bottom plate is a GFRP plate.
9. An assembly as claimed in claim 6 wherein, said U-clamps are U-shaped copper terminals.
10. An assembly as claimed in claim 6 wherein, said L-clamps are Lshaped copper terminals.

11. An enclosure for said modular plate type resistive superconductor fault current limiter assembly of claim 6, said enclosure being a cryostat chamber with vacuum filled walls adapted to store said assembly in a liquid Nitrogen bath and including copper current leads, connected to said L-clamps, extending out of said bath and out of a top flange which covers the bath and the assembly
12. An enclosure as claimed in claim 11 wherein, said enclosure includes a Liquid Nitrogen inlet for allowing input of liquid Nitrogen.
13. An enclosure as claimed in claim 11 wherein, said enclosure includes a Nitrogen gas vent.
14. An enclosure as claimed in claim 11 wherein, said enclosure includes level sensors to sense level of liquid Nitrogen.
15. An enclosure as claimed in claim 11 wherein, said enclosure includes a temperature sensor to sense temperature within the cryostat chamber.
16. An enclosure as claimed in claim 11 wherein, said enclosure includes a pressure release valve.