Prevention of Ice Build-Up on Power Line Conductors and Ground Wires,
Inclusive Dates: 10/01/11 – 10/01/12
Background — Ice build-up on electric power lines and ground wires during a winter storm is a major concern to the electric power utilities in cold climate regions. Unabated, it could cause extensive structural damage and economic loss. To protect the power lines, utilities are interested in anti-icing and de-icing methods that are efficient and economical.
Approach — Precipitation icing is the primary cause of structural damage when, during a storm, raindrops or snowflakes stick to conductors and freeze to form an ice layer. A high level of vibration acceleration is known to weaken the adhesion and friction forces between the two contacting surfaces, which separate and slide relatively freely. This effect is utilized for friction force reduction in metal working. As an anti-icing approach, longitudinal guided waves generated and propagated along the power line conductors or ground wires based on the magnetostrictive sensor (MsS) technology were proposed. A high level of vibration acceleration associated with the guided waves may weaken the adhesion and friction forces between conductors and precipitation. When raindrops or snowflakes do not adhere to conductors, they will fall off by natural forces (gravity, wind, and wind-induced vibrations) and no ice layer would be formed on the conductors as a result.
Accomplishments — The feasibility of preventing ice build-up using MsS-generated longitudinal guided waves was investigated experimentally on 0.25-inch diameter steel rods. The rod was subjected to simulated icing conditions in an environmental chamber with 20 kHz guided wave vibrations propagated continuously along its length. It was found that, with approximately 0.9 micron displacements (or 1.4 x 104 m/sec2 vibration acceleration), which is the upper bound of the vibration displacements that could be produced continuously with the existing MsS technology, ice forming on the rod was unpreventable. Even if some much higher level of vibration accelerations could prevent the ice forming and build-up, this anti-icing approach was deemed impractical unless a simple way to produce the required level of vibration is found.
However, during the research project, it was realized that the MsS probe developed and used in this feasibility investigation produced about 30 times stronger signals than those generated directly in the steel rod using existing MsS probe technology composed of a coil and bias magnets. Recognizing that the developed MsS probe design would also eliminate the need of heavy bias magnets (which has limited a wider use of the MsS technology for cable/rope inspections and monitoring), a preliminary prototype MsS probe was developed and its applicability for cable/rope inspection was evaluated and proven on a 0.4-inch diameter ground wire. This magnet-less probe is expected to significantly expand the applications of the MsS technology for cable/rope inspection and monitoring.