Cable faults
Cable testing on low- and medium-voltage (LV/MV) cables throughout Austria
Cable testing does not begin with a fault but with a question: will this section last the next few years? Unlike cable fault location on low-voltage and medium-voltage cables, where something has already failed and the position is being sought, the point here is that nothing should fail. What is tested is the condition – after laying, at recurring intervals, before a network is adopted, or after construction work near the route. Go through the planned scope of testing with us on +43 (0) 2252 53169 or in writing to office@cft.at, and we will clarify sections, switching operations and an appointment.
What we do on site
We test individual sections of your network including joints and terminations, before a fault dictates the order. Testing is done exclusively on the isolated and earthed section; the switching operations remain with your own staff. You receive a test report for each section with an assessment of its condition and a recommendation, comparable at the next cycle.
Key facts at a glance
| Methods | VLF cable testing and sheath test, tested to DIN VDE 0276-620 |
|---|---|
| Application range | Buried low- and medium-voltage (LV/MV) cables belonging to network operators, municipal utilities, local authorities and industrial and commercial businesses, including cable joints and cable terminations |
| Duration | Around 45 minutes per phase, on average two hours per cable – varying with cable type and quantity. |
| Result format | Test report as a PDF for each section tested, condition assessment with a recommendation |
| Service area | The whole of Austria, from Traiskirchen. This service is not offered in southern Germany. |
For network operators and municipal utilities
In the distribution network, testing is a planning tool: it answers which section should be renewed next and which still has reserve, before a fault dictates the order. Three occasions recur – acceptance after laying, recurring testing of the existing network, and condition assessment before a network is adopted, when assets change owner and the valuation has to be reliable. The results are documented for each section so that they can be compared with later measurements.
For industrial businesses
On an industrial site, the entire production operation usually depends on a single medium-voltage ring. A typical occasion is assessment after construction work near the route: an excavator does not have to cut through a cable to damage it – a damaged sheath goes unnoticed for years while moisture reaches the cable screen. Isolating and de-energising, securing against re-energisation and earthing remain with your own operations team; we carry out the measurements.
How the job runs
1. Defining the scope of testing. You name the sections, cable type, year of installation, length and the reason for the test. From this it follows which method makes sense and what it can tell you.
2. Isolation and release for work. Your personnel isolate and de-energise the cable, secure it against re-energisation and earth it in accordance with your operating instructions. Testing is carried out exclusively on the section that has been released.
3. Testing and recording. The test voltage is applied to the section using the agreed method and the measurement is recorded. Anything conspicuous is noted as it occurs, not only at the end.
4. Assessment and handover. You receive the condition assessment with a recommendation. If the test reveals a fault, location follows as a separate step.
Equipment and methods
We test with two complementary methods: VLF cable testing assesses the insulation, the sheath test the outer covering. Testing is carried out to DIN VDE 0276-620.
VLF cable testing
VLF stands for very low frequency: testing is carried out with an alternating voltage of very low frequency instead of at mains frequency. There is a design-related reason why this detour is needed at all, and it explains the choice of method.
Polymer-insulated cables must not be tested with direct voltage – direct voltage deposits space charges in the insulation and can damage the cable instead of assessing it. Testing at mains frequency would be the obvious alternative, but for a longer section it would require a reactive power that no transportable set can provide. The very low frequency solves both: the insulation is stressed in a way similar to mains operation, at a power that can be generated on site.
The test voltage and test duration follow your specification. If you do not specify any, we test to the standard.
The limitation lies in the statement itself – the test shows whether the section withstands the test voltage, not how far ageing has progressed. A section that has passed may be only marginally above the limit.
Sheath test
The outer plastic sheath is tested against earth, that is, the question of whether the cable is still sealed. This is the test that comes first after construction work near the route, because damage to the sheath is the most common unnoticed construction damage. The limitation: it tells you that a sheath fault is present, not where – sheath fault location follows for that.
Further diagnostics
Beyond the yes-or-no statement there are methods that describe the state of ageing rather than only the ability to withstand: partial discharge (PD) measurement, which shows weak points in the insulation before they become faults, and tan delta (dissipation factor) measurement, which uses the dissipation factor to assess ageing and moisture uptake over the entire length. Both are more involved and more demanding to evaluate than a withstand voltage test.
What you receive
You receive a test report as a PDF for each section tested, with the scope of testing, the method used, the readings and a condition assessment together with a recommendation. The header of the report states the standard applied – DIN VDE 0276-620 – together with the agreed test voltage and assessment criteria. The report can therefore be attached to an acceptance or a network adoption and serves as a reference value at the next test cycle.
Costs and effort
There is no flat rate, because the length of the section, the cable type, the test method and accessibility determine the effort involved; we agree the cost range with you by telephone before the job.
If the test reveals a fault and location follows, our rule on re-surveying applies: if our measurement was wrong, the re-survey is free of charge. If our measurement was correct but the search was not precise enough or the excavation not deep enough, the call-out is charged. The reason can be stated in one sentence: in the second case there is no measurement error on CFT’s part.
Frequently asked questions
What is the difference from cable fault location?
The occasion. With cable fault location on low-voltage or medium-voltage cables, something has already failed and the position is being sought. With testing, nothing has failed and the condition is being assessed. The two can follow on from one another, but they are not the same thing.
The test shows a fault. What happens then?
The test then ends and location begins – as a separate work step with its own methods. We agree with you whether measurement continues during the same visit or whether you first assess the section internally.
Does the section have to be isolated and de-energised for the test?
Yes. Testing is carried out exclusively on a section that has been isolated and de-energised, secured and earthed. The switching operations are carried out exclusively by your own appointed personnel in accordance with your operating instructions.
Which set of rules is used for testing?
DIN VDE 0276-620. The test voltage and test duration follow primarily your specification – if you have your own operating rules or acceptance conditions, we test to those. If no specification is given, the standard applies. The scope of testing, the test voltage and the assessment criteria are agreed in writing before the job and recorded in the header of the report, so that the test remains comparable at the next cycle.
Do you also test in southern Germany?
No. We offer cable testing exclusively in Austria, from Traiskirchen. This does not apply to cable fault location – we also carry that out in southern Germany, see cable fault location on medium-voltage cables.
Contact and opening hours
CFT Group GmbH, Wiener Straße 99, A-2514 Traiskirchen, +43 (0) 2252 53169, Monday to Thursday 8:00–16:30, Friday 8:00–12:00 – for jobs throughout Austria. Outside office hours, write to office@cft.at and we will come back to you on the next working day.
Related services
Fault location on low-voltage cables
When the test reveals a fault on a low-voltage section and the position has to be found.
Fault location on medium-voltage cables
The same on the medium-voltage ring, where high-resistance faults predominate.
Cable fault location on street lighting networks
For municipal lighting networks with long rings.
Cable and pipe locating
When the route has to be established before the test.
Utility asset record for GIS
When test results are to be kept permanently in the asset records.
Instruments from SPRINGBOK
Time domain reflectometers for the TDR prelocation that follows a test finding.
Instruments from Radiodetection
Locating equipment for the route of the tested section.
Describe the findings.
The more precisely you describe the findings, the more directly we can go to work. Plans, readings and photos help us settle the method in advance.
What happens next
- We read your message and match the case to a method.
- We come back to you – usually with a question that shortens the appointment.
- We confirm the appointment and what it costs before anyone sets off.
Rather talk?
+43 (0) 2252 53169
Mon–Thu 8:00–16:30 · Fri 8:00–12:00
Describe your case.
Fastest by telephone – then we settle straight away which method fits and what you should prepare.
Outside office hours, write to office@cft.at.