Successful fault level prediction trials

Outram Research has confirmed that trials with Scottish Power Energy Networks (SPEN) and Western Power Distribution (WPD) to test and validate an entirely original solution to determine peak fault current on the electrical network have been a success.

The Outram Fault Level Monitor (FLM), which predicts the RMS and peak fault current by passively monitoring disturbances on the transmission and distribution networks during normal operation, is a more cost-effective and potentially more accurate approach than existing methods. The compact device allows users to take measurements on the live network and calculate a fault level value at that measurement point using both upstream and downstream information. The user is presented with a full fault level overview including real time fault level predictions, the trend and average values over a time period such as 30 minutes.

The new product can help improve network safety by accurately predicting fault current and revealing potential fault level issues, in turn helping operators make better investment decisions and simplifying the connection and management of distributed renewable power generation. Network operators will be able to identify the fault level in areas of the network where network modelling may be difficult or non-existent, verify the adequacy of network breakers and resolve fault level problems more quickly. Applying the Outram FLM to Active Network Management schemes is further demonstrating the commercial viability, flexibility and general potential of the Outram FLM for electrical distribution companies worldwide.

Field trials with SPEN demonstrate that the Outram FLM can consistently and accurately calculate fault current in real-world applications. The results are within 5% of the values produced by computer modelling, which has previously generated the most accurate fault level calculations available. In fact it is possible that the values produced by the Outram FLM are more accurate than the modelled values.

Managing Director of Outram Research, John Outram, said: “We are delighted with the success of the trials. The possibility of having an instrument that predicts the value of the maximum fault level on their networks, at every voltage level, is generating much interest among Distribution Network Operators (DNOs). The Outram FLM is a unique solution which meets a need that, up until now, has remained unfulfilled. The equipment is the size of a lunchbox so can be deployed quickly and easily and moved from site to site by a single engineer. We have worked very closely with SPEN on the requirements and with additional help from another UK DNO, Western Power Distribution, we aim to deliver a solution with all the functionality required by operators worldwide.”

Western Power Distribution (WPD) is planning to take the Outram FLM one step further. With a vision for an Active Network Management solution, WPD aims to introduce a means of supplying the FLM with a small, non-customer-affecting network disturbance and to combine it with the benefit of further communications developments. This should enable a Fault Level value with a high confidence rating to be produced on demand. WPD have identified a real network environment in which they aim to trial active fault level-based control of a Distributed Generation connection.

Stage one of this project involved laboratory trails comparing the predicted fault level with the actual measured peak current seen in response to a bolted fault. These trials were outstandingly successful, the results showing that the FLM predictions were between 2.5 and 5% of the current measured by lab instrumentation – an error margin felt very hard to improve upon as noise on the network and sensor deficiencies will always produce some degree of uncertainty.

All these trials show that the FLM technique is not only accurate, but also that this precision can be repeated in different network situations. Outram Research Ltd is currently in talks with other DNOs to get the Outram FLM deployed in a number of further sites. After reinforcing their findings with more trials, Outram looks forward to offering the FLM to the wider market and is now accepting expressions of interest.