"We take the complexity out of cable diagnostics"
Interview with Tobias Neier, Head of the BAUR Diagnostics Centre of Excellence
Mr Neier, you compare analysing the cable condition with a check-up at the doctor's – why?
Just as every patient is different and requires an individual interpretation of laboratory and measurement results, so too are cable systems. To assess their condition, experience is needed when evaluating the results. This is a daunting prospect for many because there are no generally valid limit values. But those who learn to use cable diagnostics are able to obtain valuable information about the "state of health" of their distribution network, increase the security of supply, and can typically reduce costs considerably.
What are the actual economic benefits of cable diagnostics?
Knowing the condition of your cables allows you to estimate their remaining life time, enabling better planning of investment in replacements. Often the remaining service life is extended by many years. Or you can identify gradually developing weak points and avoid failures as a result, combined with a more targeted and cost-effective approach to repairs. And for new cable routes or repaired sections, cable diagnostics can show whether the route is OK and the cable accessories have been properly mounted. This also helps to prevent faults from creeping in.
But cable diagnostics takes time – is it really worth the effort?
Definitely, especially for older distribution networks. Anyone who just replaces their 40- or 50-year-old XLPE cables after their intended service life has been reached is simply throwing good money away. That's because many cables are in much better condition than their age would suggest. The advantage of diagnostics here is that it provides meaningful information about the condition of the cable and, unlike cable testing, it is non-destructive. So even if the measured cable has reached the end of its service life, the measurement will not "test it to destruction". Rather, the diagnostics would reveal weak points, enabling you to plan repairs or replacement.
But device training is not the only thing the Centre of Excellence offers. What other services does your team provide?
Our services range from providing advice before making a purchase, training courses for devices and software, creating a diagnostics strategy and assessment logic right through to optimal implementation of the statex® analysis software. At BAUR, we talk about being the "home of diagnostics" and we want operators to feel at home with diagnostics in every area – measurement, evaluation, and assessment.
You just mentioned pre-sales advice. How does that work?
First of all, we work with the customer to determine what is important to them. To do this, a number of questions need to be answered: Is reliability the main concern, is it maintenance costs, or is the network in such a state that major investment in replacements is likely in the near future? What is the existing network topology? For example, an intermeshed urban network places completely different demands on the diagnostics strategy than would a rural network with many spur lines or the distribution network of an industrial park. And, of course, the type of cables used – whether paper-insulated, first generation or more recent XLPE, PE cables, etc. – is important. Based on these factors, we can come up with recommendations for the correct procedure for cable diagnostics and the appropriate technology and evaluation logic.
You mentioned online diagnostics earlier. What role does it play in making diagnostics more efficient, for example, with the help of the VDS PD coupler?
Online diagnostics plays a major role here, because it is quick and easy to perform. We only recently launched the VDS PD coupler onto the market. It is an accessory for our liona measuring device that makes it possible to detect partial discharges (PD) on cable routes without taking them out of operation. The coupling unit is simply connected to the VDS sockets of the switchgear. The measurement therefore only takes a few minutes and offline partial discharge measurement is only necessary if the online measurement indicates a critical condition. So, all in all, operators have to spend much less time on PD measurements, as experience has shown that the majority of measured routes are in good condition.
What other options are there for carrying out cable diagnostics in a time-saving way?
There's the option of performing offline partial discharge measurement and dissipation factor measurement (tan δ measurement) in parallel. So both are carried out in one measurement procedure, which can also include normal cable testing as an option. We call that a Monitored Withstand Test.
The test voltage is increased gradually. If the measurement results indicate a healthy cable, the procedure can be shortened. If, on the other hand, the cable appears to be severely aged or damaged, an extended measuring time provides certainty. It is therefore only necessary to measure and test for as long as is appropriate for the cable condition.
The advantage here is that cable testing is not carried out if the diagnostics already indicate a damaged cable. This prevents cables from failing as a result of testing.
The evaluation of the measurement results also saves time. Based on criteria that can be defined by the operator, the report initially differentiates between good cables, cables that require observation, and severely service-aged cables. If urgent action is required, the measurement engineer on site can see this immediately on the measuring device or at the beginning of the report. The measurement reports become more specific as they progress. The reports can of course be easily exported and processed further in asset management, for example to make comparisons or determine trends.
Speaking of interpretation, many potential operators are troubled by the fact that there are no simple limit values, no "good" and "bad" in diagnostics. Why is that and how do you help operators?
Some people may think that evaluation is like reading tea leaves. But that's not the case. What we lack are fixed limit values for PD measurement and values that can be applied to all types of cables or to mixed routes. That makes things more complex.
We therefore help operators to interpret their measurement results and, if requested, can develop an evaluation strategy and assessment logic with them, as well as helping with evaluations. The assessment logic is customised and can therefore differ from network to network, depending also on the properties. However, our own experience is also part of the process. It is therefore possible to provide start-up assistance based on a great deal of practical experience.
Repeat measurements, trend analyses, root cause analysis of failed cable routes, and much more besides create a wealth of experience for the operator, which makes cable diagnostics more valuable for the company year on year, as well as resulting in slight modifications to the assessment logic.
The evaluation logic allows derivation of specific action plans. With the home of diagnostics and our Centre of Excellence, we support operators on this path. Long-term relationships with customers help to expand their wealth of experience and also to expand our expertise and share it with other customers. After all, it was a close customer relationship that resulted in one of our software solutions, which enables operators to convert the values from dissipation factor measurement into an ageing index and calculate the remaining life time, namely statex®.
Ah yes, the statex® analysis software for calculating service life. What exactly does it do?
The statex® software is based on an evaluation logic created by Korean company KEPCO for its analyses of dissipation factor measurement.
Together with BAUR, this resulted in statex®, a solution that incorporates statistical calculation methods and a great deal of experience. Hence the name, which is composed of "statistics" and "experience". The software uses a database in which the measured values of more than 120,000 cables are stored. Initially, only the values of XLPE cables were stored here, but the diagnostics results of PILC cables and mixed routes are now also included.
Operators who use statex® can therefore very reliably determine the remaining life time of their cables, based on the entire database.
Further information
