Key Facts:
- New technique calculates fault current by observing normal operation of the grid
- Allows accurate planning of breakers and other key components
- Avoids unnecessary over-specification of components
- New patent-pending technique developed by UK company Outram Research
- Field trials underway to show that algorithm is accurate in real-world situations
Outram Research Ltd – a specialist manufacturer of leading-edge power quality analysers – is conducting a research project with ScottishPower (Energy Networks) that aims to provide new insights into the characteristics of the electricity supply grid, enabling more accurate planning of capacity and upgrades. The research project uses a new technique developed by Outram to measure fault current, the maximum current that can flow in the event of a fault.
Fault current, also known as short-circuit current, is a critical factor for network planning. Objects on the grid must be capable of withstanding the maximum fault current, and components such as breakers must have sufficient rating to isolate the fault safely, allowing the rest of the system to continue functioning.
Determining fault current is a major challenge for planners at electricity utilities as the grid becomes increasingly complex. Motors and other inductive loads can deliver energy back to the grid in the event of a fault, whilst distributed generation of power from renewable sources such as solar power means that parts of the grid may change dynamically from consuming power to supplying energy at different times of the day or week.
Geoff Murphy, lead development engineer with ScottishPower Energy Networks, commented, “With increased dynamics within the electricity network, measuring the capacity and capability of the system is vital to enable the connection of new types of generation and loads. Outram Research offer a novel and efficient way of calculating fault currents to enable us to plan and design the system more effectively and avoid unnecessary expenditure.”
Existing methods of measuring fault current are limited, and can only provide approximate values after a long period of measurement, which may last several weeks. The new patent pending technique calculates fault current accurately and quickly, monitoring parameters without affecting the network or users consuming power. Utility companies can also use the technique to determine how fault current changes over time: for example as different loads are connected and disconnected over the course of a day or week.
“We have already demonstrated the effectiveness of this new technique in the laboratory,” commented John Outram, Managing Director of Outram Research. “Our partnership with ScottishPower will allow us to assess the effectiveness and accuracy of the algorithms and Outram hardware when used to monitor current in the field.”
The research project is already underway, with results expected in the fourth quarter of 2011.
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