08 superconducting power grid - cryogenic issues - vv rao
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Superconducting Power Grid – Cryogenic IssuesBy Prof. V. V. Rao, IIT KHARAGPUR
DAE BRNS Theme meeting on LiquidDAE‐BRNS Theme meeting on Liquid Helium Plants, Cryogenics Systems and
their Applications, 25‐26th February 2013, Kolkata
Activities at Applied Superconductivity LaboratoryActivities at Applied Superconductivity LaboratoryCryogenic Engg Centre IIT KharagpurCryogenic Engg Centre IIT KharagpurCryogenic Engg. Centre, IIT Kharagpur Cryogenic Engg. Centre, IIT Kharagpur
SMES
Power Grid
HTSC Generator
HTSC Transmission
cables
HTSC Fault Current Limiter
HTSC Transformers HTSC Motors
Power Grid
BHELCPRI
&P CG, Power BHEL BHELBHEL &Power Grid
CG, Power Grid BHEL BHEL
1SMES storing Li2energy in S.C. inductor Retrieving the energy to utility loadwhen required.
Using cable‐in‐conduit type S.C. wires, thousands of amperes of current can be made to flowthrough the S C coils for storing large amounts of energy which can be fed back to the load
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through the S.C. coils for storing large amounts of energy, which can be fed‐back to the loadwhen the main‐supply fails. More efficient than pumped hydro and battery storagemethods
Superconducting Magnet along with LHe Storage and power electronics housed in Trailer
SMES System Manufactured by AmericanSMES System Manufactured by AmericanSuperconductor Crop., is used by militarybases to extend battery life.
Trailers house SMES units at Tinker Air Force Base in Okalahoma city to enhance
data protectionp
Portable SMES
Very Large Scale SMES for Blackout Solutions
Parameter / Unit JAPAN USAStored energy (MWh) 5,000 5,500
Output power (MW) 1,000 1,000
Coil Current (kA) 707 765Inductance (H) 71.8 67.6Peak field (T) 8 4 7 0Peak field (T) 8.4 7.0
Conv. Efficiency 0.95 0.94
Cryogenic loss (MW) 6.0 5.3He temperature (K) 4.2 1.8p ( )Coil diameter (m) 400 376 400 1568Coil height (m) 10.8 18.0 10.8 15
No. of turns 330 112
Conductor Length (km) 403 574Conductor Size (cm) 21 x 10 13.5
Material Nb3Sn NbTi
Overall Weight (Ton) 25 000 24 000Overall Weight (Ton) 25,000 24,000
Underground structure 3‐tunnel trench
Depth (m) 150 15
SMES development at IIT Kharagpur
0 5 MJ S d i i
SMES coil
(42 cm O.D. and 44 cm height
0.5 MJ Superconducting magnetic energy storage (SMES)
(4 cm O. . and 44 cm heightNbTi Conductor)
Quench and magnetic field gsimulations of HTS‐SMES coils
by Opear‐3D
The Superconducting fault current limiter (SFCL)
Electric power network with FCL in transmission line
The Superconducting fault current limiter (SFCL)
Key characteristics of Fault Current Limiters based on superconducting materials
Under normal operation a fault current limiter inserts negligible impedance into thet knetwork
When a fault occurs the limiter‘s impedance rises rapidly, reducing the current flowingthrough it
Indian power system is expanding at exponential rate with power demandd h 400GW b 2022expected to reach 400GW by 2022.The Corresponding addition of these generation capacity is planned in theresource rich areas of North‐Eastern and Eastern part of the country. However, theload centers are mostly at Northern, Western and Southern parts. Hence totransmit this generated energy to the distant load centers, very large powertransmission cables are required.Establishing such a large transmission network by conventional overhead linesinvolves socio-economic and technical challenges that includes Right‐of‐Way(ROW) availability environmental protection reduction of transmission losses and(ROW) availability, environmental protection, reduction of transmission losses andConductor Volume, control of fault levels, cost optimization etc.
HTS cables (2G-YBCO) cooled to cryogenic temperatures (65-77K) candd th i W k i i i d i i h i taddress these issues. Work is in progress in designing such cryogenic systemskeeping in mind AC Losses, Heat‐in‐leak, reliability and safety aspects
Cold Vs Warm Dielectrics
Cold dielectric (Within Vacuum Vessel)Dielectric at LN2 Temperature
Warm dielectric (Beyond Vacuum Vessel)Dielectric at Room TemperatureDielectric at LN2 Temperature Dielectric at Room Temperature
Has low losses Generates higher lossesPower capacities – 3-5 times theconventional cables
Power capacities- double of conventionalcables
Technical challenges due to temperaturedependent properties of cold dielectricinsulation
Less technical challenges due to use ofconventional dielectric insulation
HTS t b d hi ldi l L k f HTS hi ldi lt i ddHTS tapes can be used as shielding layers to contain magnetic fields, decreasing the amount of eddy current loss. Neighbouring cables can be closer
Lack of HTS shielding can result in eddy currents in the cryostat and other components at higher currents. Neighbouring cables cannot be closer to avoid Jc degradation
Design Issues for Cooling of HTS Cables
Electrical ThermalLosses
A.C. Losses Dielectric Losses
Thermal
Conduction and Convective losses Heat Leaks
Fluid Mechanics
Pressure Drop Friction factor
Material Science
Pressure Drop Friction factor
Mechanical
Former Materials Insulation Materials
Mechanical
Bending Radius Fracture Toughness Twist Pitch of HTS Tape
CLOSED LOOP COOLING SYSTEM (COURTESY: NEXANS)
Cryorefrigerator (Brayton,Stirling Cycles)
OPEN LOOP COOLING SYSTEM (COURTESY: NEXANS)
TERMINATION with CRYOGENIC COOLING
FIGURE ‐ Front‐view of the 25‐m HTS‐FCL cableand its corresponding 3‐phase terminationslocated at the HTS cable test facility at the OakRidge National Laboratory, USA. The HTS‐FCLcable exits the building after the firsttermination and re‐enters the building in frontof the second termination.
HTS Motors: Advantages• High Power Density: The HTS field winding produces magnetic fields higher than those with g y g p g g
conventional machines, resulting in smaller size and weight.
• High Partial Load Efficiency: HTS motors have higher efficiency at part load (down to 5% of )full speed) that results in savings in fuel use and operating cost. The advantage in efficiency
can be over 10% at low speed.
• Low Noise: Lower sound emissions than conventional machines.
• Low Synchronous Reactance: HTS air‐core motors are characterized by a low synchronous reactance which results in operation at very small load angles. Operating at a small load angle provides greater stiffness during the transient and hunting oscillationsangle provides greater stiffness during the transient and hunting oscillations.
• Harmonics: Tolerate power grids with high harmonic content.
C li l d i i i i Fi ld i di l lik• Cyclic load insensitivity: Field windings operate at nearly constant temperature unlike conventional motors and, therefore, are not subject to thermal fatigue.
• Maintenance: HTS motors compared to conventional motors will not require the common• Maintenance: HTS motors compared to conventional motors will not require the common overhaul, rewinding or re‐insulation.
Cryogenic Cooling of Rotating HTS Machines
•A Helium Transfer Coupling (HTC) is a device that puts the cryogen in and out from theA Helium Transfer Coupling (HTC) is a device that puts the cryogen in and out from thestationary cooling system to the rotating part of the HTS motor.•We have to maintain field‐pole HTS coils at the cryogenic temperatures during rotation.
HTS Transformers for the power grid – half the size and weight‐ Double the efficiencyg y
Benefits:• Greater efficiency• Greater efficiency• Compact, lighter and quieter• Can run indefinitely above rated
power without affectingtransformer lifeD t i li il lik• Do not require cooling oil like
conventional transformers, thuseliminating the possibility of oilg p yfires and environmental hazards
• Do not Require IronHence, Compact and Lighter
S d iS d i
Superconducting Power Cables
Superconducting Power Cables
S d ti F ltS d ti F ltSuperconducting Magnetic Energy Storage
Superconducting Magnetic Energy Storage
Superconducting Fault Current Limiters
Superconducting Fault Current Limiters
Role of HTS materials for power application –
growing rapidly
Role of HTS materials for power application –
growing rapidlySuperconducting Superconducting Superconducting Superconducting Cryogenic Refrigerators
with High Cooling Capacity are being
developed
Cryogenic Refrigerators with High Cooling Capacity are being
developed
Generator/MotorGenerator/Motor TransformersTransformers
Interaction with R&D Institutes and Industries
Central Power Research Institute, Bengaluru Power Grid Corporation of India Limited, DelhiBharat Heavy Electrical Limited, HyderabadCrompton Greaves MumbaiCrompton Greaves, MumbaiSchneider Electric, Bengaluru
Looking for collaboration with Academic Institutes