The dielectric strength of dissociated cryogenic gas media
Abstract
The dielectric strength of dissociated binary and ternary gas mixtures containing helium, hydrogen, and nitrogen for cryogenic power applications is reported. The compositions of the dissociated gas species in the temperature range of 77–5000 K at 1.0–2.0 MPa are obtained by minimizing the Gibbs free energy assuming local chemical equilibrium. The resulting mole fractions of the dissociated gas species that vary as a function of temperature and pressure are used for calculating the density-reduced critical electric field representing the dielectric strength. The results suggest that the He-H2-N2 mixture has higher dielectric strength than the He-H2 and He-N2 mixtures, but NH3 would potentially accumulate over multiple arcing and cooling cycles and potentially cause long-term issues in cryogenic switchgear applications. On the other hand, the binary alternatives, the He-H2 and He-N2 mixtures, show lower dielectric strength than the ternary gas mixture but will maintain their original gas properties even over multiple arcing and cooling cycles. The results also show that the dielectric strength of the He-H2-N2 and He-H2 mixtures decreases substantially with increasing temperature whereas that of the He-N2 mixture stays nearly unchanged. The results of this study are useful for the fundamental understanding of gas dielectrics under arcing conditions in cryogenic switchgear applications and the development of resilient cryogenic power systems.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Sep 13, 2018
- Source ID
- 10.1063/1.5051769
Entities
People
- Chanyeop Park
- Lukas Graber
- Sastry Pamidi
Organizations
- Florida State University
- Georgia Tech
- Office of Naval Research