In systems for controlling electrical processes, such as for controlling generation and transmission of electrical power, i.e. high-voltage power transmission and generation systems, it is necessary to measure the voltage at various points in the system, such as for instance in a power line in order to provide control and protection of the system.
In order to provide a reliable system there may be redundancy in relation to the control and protection devices provided. Such a redundancy means that several different parallel protection and control devices may need to receive measurements from the same element in the process.
WO2006/128397 discloses an HVDC system where two separate connections to a power line are provided in order to provide redundancy in relation to measurement results.
However, when the system is a high-voltage system it is often necessary to limit the number of contacts to the system element to as few as possible. There may otherwise be a risk for flashover. This is especially the case in Ultra high HVDC (High Voltage Direct Current) power transmission systems.
One way to solve this problem may be to provide duplicated amplifiers connected to a voltage dividing element. Voltage measurements of a system element, such as a power line may be performed through duplicated amplifiers directly connected to such a primary voltage dividing element. However, with this solution it may not be possible to ensure a high enough reliability. The amplifiers may furthermore not be possible to be replaced during operation.
There is therefore a need for an improvement when measuring voltages of electrically conducting elements in a system for controlling an electrical process.