Cryogenic System for a High Temperature Superconducting Power Transmission Cable Page: 4 of 9
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operate the cable at voltage and current for 26 h to achieve steady state operation for an
extended period. A fifth run, conducted for 72 h, demonstrates the capability of operating
the cable for extended periods at current and voltage. These runs simulated the normal
operation of the cable expected in the field.
This section is a brief discussion of the placement and accuracy of the instrumentation
used in the HTS cable system. Table 2 lists the sensor types and accuracies as listed by the
manufacturers. Thermometers T4 and T5 are factory-calibrated platinum resistance
temperature devices (RTDs) mounted in stainless steel sheaths. They are installed in the
liquid manifolds on the terminations as shown in Fig. 1. Thermometers T6 and T7 are
factory-calibrated platinum RTDs mounted on specially designed TeflonTM holders to
measure the temperature of the liquid nitrogen going into and out from the HTS cable
through the HTS cable former. The TeflonTM holders were required to provide electrical
isolation from the HTS cable when it is at high voltage. Thermometers T8 and T9 are
factory-calibrated platinum RTDs that are mounted on the cable centering spiders and
measure the liquid nitrogen temperature of the return flow over the outside of the cable.
The flow rate of liquid nitrogen is measured with a turbine flowmeter given in Table 2 and
has a factory calibration. The inlet and outlet pressures are measured with strain gage
HTS CABLE CRYOGENIC SYSTEM TESTS
The pressure drops in the HTS cable system were measured as a function of flow
without carrying current in Run 1. The HTS cable pressure drop is measured across the
supply and return lines to the HTS cable (P4 - P5). The data fit well with the following
expression for the pressure drops in the system:
AP = APg + K , (1)
where the pressure drop AP is a combination of the contribution due to changes in
elevation within the system APg and the mass flow rate through a modified loss coefficient
KL for the HTS cable and terminations [KL = 2.8 x 10-6 bar/(g/s)2].
Table 2. Instrument list and accuracies
Instrument Type Range Accuracy Vendor
T-6 Platinum RTD 14 K-325 K 20 mK at 100 K Lakeshore
T-7 (PT-103) 35 mK at 300 K Cryotronics
PS-1 Strain gage 0-10 bar gage 1% FS Omega
PS-3 Strain gage 0-1 bar absolute 1% FS Omega
T1 RTD 32.6 K-1128.6 K 0.1 K Doric
Flow Turbine meter 3.7-38. L/min 0.15 % Sponsler Company
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Demko, J.A.; Gouge, M.J.; Hughey, R.L.; Lue, J.W.; Martin, R.; Sinha, U. et al. Cryogenic System for a High Temperature Superconducting Power Transmission Cable, article, July 12, 1999; Tennessee. (digital.library.unt.edu/ark:/67531/metadc624543/m1/4/: accessed May 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.