Case study

Suppressing noise from corona effect on a 400kV Line with an innovative OHL conductor design

LOCATION

Germany
PARTNERSHIP

Amprion
Market

Overhead Lines

Eliminating noise pollution caused by overhead lines

In high voltage transmission lines, corona effect is a common physical phenomenon resulting from the ionization of air at surface of the conductor. Corona discharges cause a humming noise that can be a major nuisance for the surrounding population.

Corona discharges occur when the electric field at the surface of the line reaches a threshold value, which is a function of applied voltage, conductor diameter & surface, and atmospheric pressure. The presence of water drops on the surface of OHL conductors amplifies corona effect.

In 2018, Nexans supplied Amprion an innovative OHL conductor specifically designed to suppress corona effect. The conductor was developed to answer the specific need of the German TSO to replace an existing conductor with a low noise solution without replacing the pylons.

The project challenge was to increase the conductor diameter and ampacity while keeping the same linear weight and sag as the original conductor.

400 ^kV

Voltage

1000 ^Amps

Ampacity

+50%

Ampacity increase

2025

In operation

Nexans solution

Nexans OHL conductor design team developed an innovative conductor based on Nexans ACPR LoSag technology including a high modulus carbon composite core for reduced sag, and ice load conditions.

The team succeeded in producing an expanded conductor including a internal layer of aluminum tubes stranded with Z-shaped aluminum wires on the external layer to minimize the increase in drag coefficient. The final diameter was increased by 25% to 25.9mm while the linear weight remained almost unchanged.

In addition to the conductor expansion, a sandblasting treatment was applied on the surface of the conductor in order to control its hydrophily. As a result, water drops are immediately spread over the conductor surfae limiting the risk of local reinforcement of the electric field.

The effectiveness of the design was validated in laboratory. The pilot installation done by Amprion in 2018 further confirmed the efficiency of Nexans solution to avoid corona effect during accoustic measurements in real-life conditions. A second installation of this conductor will be performed in 2025.