BAUR's new software, statex, helps utilities to keep their medium-voltage cables in service for as long as possible without jeopardizing the security of supply. The new analysis software evaluates the data from the dissipation factor measurement (tan delta measurement) and uses a patented algorithm to calculate the statistical remaining cable lifetime.
The statistical calculations carried out by statex permit more accurate predictions than evaluation according to IEEE 400.2, which only allows for statements such as "OK" and "action needed." The statex software is based upon a stored data pool and also takes into account the additional parameter TD-Skirt, which predicts the stability of the dissipation factor over several measured values in a measurement cycle. The algorithm used in statex was developed by Korea Electric Power Corporation (KEPCO) and the University of Mokpo (Korea) and its statistical analyses draw upon results from 45,000 cable routes.
Identification of potential savings
Studies by KEPCO have shown that it’s often possible to delay investment in replacement cables. The evaluation of measurement data using the statex algorithm allows cable condition to be assessed significantly more accurately, resulting in a remaining cable lifetime around 11 years longer than that achieved when estimating using IEEE criteria, even for a high-quality distribution network. This meant that existing cables can be kept in service for longer, considerably reducing maintenance costs.
Calculation of remaining cable lifetime based on a diagnostic measurement
statex is said to provide reliable analyses right from the initial dissipation factor measurement, but when repeat measurements are performed on the same cable, the statistical software draws upon the previous results to produce an even more precise prediction. In addition to the expected remaining lifetime, the software also provides recommendations as to when the next cable diagnostics should be performed and for the scheduling of maintenance work or cable replacement. The statistical tool includes both the economic operating limit and an individual user-defined safety margin, meaning users can simply lower the “warning threshold” if they require extra safety.
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