Current driven transformers for contactless power supplies in HV lines

Current driven transformer

The electrical transmission system of most developed countries is aging and under increasing load, which gives rise to equipment wear-out failures. This diminishes system reliability and increases the global cost of operation. Since the grid is constrained to expand, a possible solution is to optimize the operation and improve the inspection and maintenance of the existing power system.

Through such a process, the goal is to maximize utilization, boost efficiency and enhance the reliability of the transmission network. The use of autonomous robots in inspection and maintenance plans of overhead transmission lines is a valid option to achieve such a task while minimizing costs and ensuring worker safety.

The power supply of the robot has been identified as a crucial component in the viability of the project.

Recent developments have determined that a power supply based on the magnetic energy around the power transmission line is feasible and possesses significant advantages over known options, such as enabling the robot to operate unattended for long periods of time and permitting weight reduction of the power supply.

To use the magnetic energy, a current-driven transformer is clamped around the power line, functioning mechanically like a current probe.

Furthermore, a capacitor is connected to the transformer secondary in order to establish a resonant circuit and therefore increase the output power transferred to the load without increasing the size of the core. Design procedures for this case are displayed and related to computer simulation.

Load tests are presented and compared with the case without the capacitor.

Context and State of the Art

Power utility companies in most of the developed countries are facing the problem of operating and maintaining electrical transmission systems that are aging and under increasing load, whilst being constrained to expand the grid.

The process of aging gives rise to equipment wear-out failures and the increased demand for electricity results in congestions, significantly increasing the stress-related faults. Hence, future system reliability is diminished and the global cost of operation is increased, not only from constraints in total power transfer capacity but also from the required expansion, redundancy, and added maintenance plans.

Typically, these are the industry practices, yet the inherent high costs of equipment and labor, as well as time-frame, associated with the planning and construction of high voltage lines, have impaired such solutions. Also, the growing public sentiment against locating new transmission power lines in the communities is an important deterrent.

To achieve such a task, possible options are the use of autonomous robots in inspection and maintenance plans of overhead transmission lines and the use of Distributed Flexible Alternate Current Transmission Systems (D-FACTS) to control power flows in the transmission grid.

Figure 1 (see above) shows a conceptual schematic for each of these solutions.