SENTRY provides information on the health and risk associated with underground LV cable assets, allowing planning of investments and targeting resources most efficiently to maximise network reliability into the future. In addition, SENTRY can detect insulation breakdown very early in the failure process, flagging for installation of auto-reclosing equipment and/or repair before an outage event.
Low Voltage (LV) cables represent a significant proportion of a DNO’s asset base, yet there is little availability of data to permit asset condition assessment (a cornerstone of the long term asset intervention strategy) and hence asset risk to a DNO. The industry uses the Condition Based Risk Management (CBRM) system to assess the condition of many of the assets. This assessment is based on the likely condition from the age, environment and duty of an asset and then modifies this through use of various data sets to provide an estimate of the probability of failure. In order for an asset to be assessed in this manner there needs to be a collection of appropriate input data which reflects the asset’s current condition and the trend or movement in that condition over the medium to long term.
In the case of solidly insulated cables in general and LV cables specifically, data is not presently widely available. Existing methods require the destructive testing of the cable (generally through cable sampling) and analysis of the condition of the cable’s components to determine if a level of degradation can be determined. This results in disruption to customers and stakeholders alike and is often costly owing to the excavation of footways and roads. An alternative to intrusive destructive testing of cables is to measure data from in-service cables using SENTRY over a time period and use this data to determine condition.
SENTRY accurately assesses the comparative cable condition and its movement over time in comparison to similar assets. It achieves this by monitoring the electrical characteristics of the LV cables connected to an LV fuse panel, as well as injecting a spread spectrum signal into the cables and performing analysis on the returned signals. At KELVATEK we have been researching and collecting live network data on LV cable failure modes for nearly two decades. Recently we built a dedicated LV cable failure mode research facility at our test network.
As most new connections are provided in some manner from existing low voltage cable networks the ability to determine the relative health of the asset prior to connection will provide network operators with improved measures of the cable reliability under higher loading conditions and hence will permit targeted intervention on the associated asset. This assessment of the cable condition will therefore replace the current process of “fix on fail” and hence provide improved customer service for all.