High-temperature superconducting (HTS) direct current (dc) power cables allow high levels of power transmission and distribution at low loss and can be tailored to effectively limit fault currents. HTS Conductor on Round Core (CORC ®) power transmission cables offer additional benefits over other HTS cable designs, including a much higher current density and a higher degree of flexibility. These benefits make CORC ® cables most suitable for applications in confined spaces where tight bends are required, such as onboard naval ships and in data centers. The development of CORC ® power transmission cables for operation in pressurized helium gas is described, including their ability to act as fault current limiting cables. The 10 m long bipolar dc CORC ® power transmission cable system is designed to operate at a current of 4000 A per pole at 50 K in pressurized helium gas. The test results at temperatures between 60 K-74 K in helium gas at a pressure of 1.7 MPa are described both during normal operation and during an overcurrent event. The results demonstrate the potential of CORC ® cables to operate at currents exceeding 10 000 A per pole at 50 K at current densities of more than 200 A mm −2 , resulting in the most energy dense superconducting power transmission cable to date. The successful operation during an overcurrent event also shows the added benefits of the high level of current sharing between tapes in CORC ® cables that allow them to be operated as FCL cables without the need to incorporate a substantial amount of stabilizer. The successful test is a major milestone towards reliable high energy density power transmission in helium gas cooled superconducting power systems based on CORC ® cables.
Recently, the number of cyber threats on power systems has increased at an unprecedented rate. For instance, the widespread blackout in Ukrainian power grid on December 2015 was a wakeup call that modern power systems have numerous vulnerabilities, especially in power substations which form the backbone of electricity networks. There have been significant efforts among researchers to develop effective intrusion detection systems (IDSs) in order to prevent such attacks or at least reduce their damaging consequences. However, all of the existing techniques require some level of trust from components on the supervisory control and data acquisition (SCADA) network; hence, they are still vulnerable to sophisticated attacks that can compromise the SCADA system completely. This paper presents a radio frequency-based distributed intrusion detection system (RFDIDS) which remains reliable even when the entire SCADA system is considered untrusted. The proposed system uses radio frequency (RF) emissions to monitor the power grid substation activities. Indeed, it utilizes a radio receiver as a diagnostic tool to provide air-gapped, independent, and verifiable information about the radio emissions from substation components, particularly at low frequencies (LF, 0.05−50 kHz, or >20 µs period). The simulation and experimental results verified that four types of diagnostic information can be extracted from radio emissions of power system substation circuits: i) harmonic content of the circuit current, ii) fundamental frequency of the circuit current, iii) impulsive signals from rapid circuit current changes, and iv) sferics from global lightning strokes. Each or a combination of the first three diagnostics can be effectively leveraged to directly detect specific types of power grid attacks. Meanwhile, the last diagnostic is utilized to check the integrity of the receiver's signal as it is encoded with the quasi-random distribution of the global lightning strokes. The simulation and real-world experimental results verified the effectiveness of RFDIDS in protecting the power grid against sophisticated attacks.
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