We have a number of recognized transmission and distribution experts serving on our board of "Grid Masters." Several times each month we’ll post what we judge to be the toughest questions that also have high interest to our readers. At least one of our experts will respond. Want to challenge our Grid Masters for a chance to win?
Q: What are the forces in play when a HVDC cable link interferes with a telecoms line within its route?
A: The potential for interference between a DC link and telecommunication circuits depends on several factors:
- DC converter harmonic generation, i.e. magnitude, frequency spectrum and degree of balance
- Effectiveness of any dc side harmonic filtering deployed
- Mutual electromagnetic coupling between the DC link and the telecommunications circuits, i.e. circuit proximity and length of exposure. Close proximity with long parallel exposure gives high coupling.
- Type of communications circuit, i.e. audible frequency range telephone wire circuit
- Harmonic cancellation, i.e. degree of harmonic balance on DC circuit (pole mode or ground mode), DC cable proximity (close laying versus spaced laying), use of twisted pair telephone circuits
- Electromagnetic shielding of cable circuit or telephone circuit, i.e. use of conductor screen or metallic conduit.
- The proper construction of the telephone circuit is very important for interference mitigation, e.g. use of twisted pairs and screening.
HVDC Business Development
See previous questions and answers and join the discussion. Add your comments below: