7.4. Determining the electric fields of overhead power lines

Project management: Danube University Krems, Department for Integrated Sensor Systems, Vienna
Start: 1 April 2020
End: 31 March 2022

Background

The high-voltage direct current transmission lines (HVDC) planned in Germany will emit static magnetic fields and, when designed as overhead lines, also static electric fields and possibly space charge clouds, which result in slowly varying quasi-static fields. In order to determine the exposure of the population, these fields must be measured. The progress in detecting exposure through static electric and magnetic fields in the vicinity of high-voltage direct current (HVDC) transmission lines and hybrid HVDC and high-voltage alternating current (HVAC) transmission lines largely depends on how reliable, low-maintenance, and mobile the measurement technology used is. In particular, difficulties in detecting static electric fields prevent fast, meaningful measurements.

The detection of the static electric field is associated with difficulties compared with the measurement of the low-frequency electric fields of high-voltage alternating current (HVAC) transmission lines. Because the measurement results strongly depend on the temperature and on the space charge or ion flow, the data output drifts slowly. As a result, the measuring systems often have to be recalibrated. The measurement is often subject to errors, especially at low field strengths. In addition, a strong distortion of the electric field results from the measuring system itself. In the presence of ions, an accumulation of space charges occurs near the sensor because the directional ion flow along the field lines. These space charges generate an additional electric field in the vicinity of the sensor; this superimposes the field to be measured on the line and can falsify the measurement result. This is particularly relevant in the vicinity of HVDC transmission lines, which are surrounded by higher ion concentrations.

Objective

Measurement technology must be developed for the reliable, cost-effective, and accurate detection of static electric fields in the vicinity of HVDC transmission lines. The primary objective of the project is the identification of field distortion-free, ion flux and potential-independent miniaturised measurement methods for the measurement of static and low-frequency electric fields in the typical environment of HVDC transmission lines and HVDC-HVAC hybrid lines as well as the testing, adaptation, and validation of these methods.

Implementation

In the first phase of the project, the researcher will review the state of the art in science and technology relevant to the project. This includes the evaluation of relevant technical literature with regard to suitable technologies, sensor designs, and readout procedures as well as the conditions that occur in the effective range of the lines. Based on this data, a catalogue of requirements for the measurement system will be drawn up, and the concept for the measurement system is developed with reference to this. The first phase of the project also includes a preliminary study based on computer simulations in order to be able to estimate the expected characteristics of the system in advance.

Based on the results of the first project phase, the construction, adaptation, and calibration of the measurement and calibration system will begin in 2020.