BAUR viola TD -- Improve Medium-Voltage Cable Testing and Diagnostics

For utilities, service contractors and industrial maintenance teams, cable testing stopped being a pass-or-fail exercise some time ago. The question that matters is not only "will this cable hold?" but "how much life does it have left, and which of these twenty feeders should we spend the next budget on?"

That is the gap the BAUR viola TD is aimed at: a compact VLF test set that also measures tan delta, so condition assessment happens on the same visit as the withstand test.

What the TD version adds to the base viola

BAUR's cable testing line uses the same "TD" suffix convention throughout, and it means the same thing on every model — dissipation factor (tan delta) diagnostics on top of the VLF test capability:

Both models are listed on our site: the BAUR viola VLF cable test system and the viola TD with tan delta.

Why tan delta matters: a withstand test only answers half the question

A VLF withstand test applies elevated voltage for a defined period and looks for breakdown. If the cable survives, you know it is not about to fail today. You do not know whether its insulation has been degrading for eight years, whether it has water trees in the XLPE, or whether it will survive the next five.

Tan delta measures dielectric loss — the energy the insulation dissipates rather than stores. On a deteriorating cable, that loss rises. The useful signal is not a single number, it is the shape of the curve:

• How tan delta changes as test voltage steps up
• How stable the reading is over the test duration
• How this year's value compares with the same feeder's value from previous years

That is why a TD set changes the maintenance conversation. A feeder with a normal withstand result but a rising TD trend belongs in the replacement plan; a feeder with a flat TD history can be moved down the list. Same test day, better decision.

Monitored Withstand Test: turning a pass/fail into data

A conventional withstand test produces one bit of information. A Monitored Withstand Test runs the same test while recording diagnostic parameters throughout — so the test itself becomes a measurement rather than a trip that either ends in silence or in a fault.

In practice this is what makes automated test sequences valuable. BAUR describes the viola TD as supporting automatic test and diagnostic sequences, which matters more than it sounds: on a multi-feeder day, operator-to-operator differences in setup and test execution are the main source of inconsistent TD data. Automation removes some of that variability and shortens time on site.

Choosing between viola TD, Frida TD and PHG 80 TD/PD

BAUR's MV cable diagnostics range overlaps deliberately, and we see the same selection question every time. Buy by the diagnostics you actually have to produce:

Two practical notes. First, PD cannot be retrofitted into a TD-only set — if partial discharge is anywhere in your five-year plan, buy the PD-capable model now. Second, if you are still building the internal case for condition-based maintenance, the article on combining tan delta and PD diagnostics and BAUR's VLF + tan delta FAQ answer the questions that usually come up in that meeting. For the PD side, see the VLF + TD + PD FAQ.

When you do not need the TD version

Tan delta diagnostics earn their cost when you are managing a population of cables over time. If any of these describe your situation, the base viola is likely the better purchase:

• Your cable work is acceptance testing on new installations, where there is no ageing history to trend
• You already own a separate dissipation factor test set
• Your fleet is small enough that a failure is cheaper to repair than to predict
• The diagnostic data has nowhere to go — no historian, no maintenance planner who will act on a rising trend

Buying diagnostics you will not act on is the most common waste we see in cable test budgets. The instrument is the cheap part; the programme around it is what produces reliability.

A typical TD diagnostic visit

1. Isolate the feeder and apply safety grounds; confirm the cable is discharged before connection
2. Connect the test set and enter cable data — length, type and joint configuration affect how results should be interpreted
3. Run the VLF withstand test at the voltage and duration your standard requires
4. Run tan delta measurement across the voltage steps in the automated sequence
5. Compare the results with the feeder's previous test data — trend first, absolute value second
6. Export the report and file it where the next crew will actually find it

The standards framework behind step 3 and 4 usually references IEC 60502-2 for after-laying tests and IEEE 400.2 for VLF field testing and tan delta practice, with national practices such as HD 620 / VDE 0276-620 in Europe. Test voltages, durations and evaluation criteria differ by cable type and by asset owner — always work from the current standard text and your owner's specification rather than from a summary page.

Buying, renting and supporting BAUR cable test systems in Canada

RCC Electronics supplies the BAUR cable testing and diagnostics range in Canada, from the portable test sets to van-mounted systems, along with the fault location and tracing equipment that usually comes with the same programme — TDR units, fault location systems and pin-pointing equipment. If you need to run a diagnostic campaign before committing capital, several of these units are available for rental, and calibration and service are handled in-house — see our services. The full range is listed under BAUR cable testing and diagnostics, with the cable testing brochure as a starting point for module and accessory planning.

FAQ: BAUR viola TD and MV cable diagnostics

What is the difference between the viola and the viola TD?
The viola is a VLF cable test system with the truesinus® waveform. The viola TD adds tan delta (dissipation factor) diagnostics, and BAUR's product description also associates it with a Monitored Withstand Test workflow. If you only need withstand testing, the base model is sufficient.

Does tan delta replace the withstand test?
No. They answer different questions: the withstand test establishes that the cable holds voltage today, while tan delta indicates how far the insulation has aged and how fast that is progressing. Running both on one visit is the point of a TD set.

Can the viola TD do partial discharge testing?
No. PD diagnostics require a PD-capable model such as the PHG 80 TD/PD. PD cannot be added to a TD-only instrument later, so plan for it at purchase if it is on your roadmap.

Does a TD test require an outage?
Yes — the feeder must be isolated, discharged and grounded before connection, so TD testing is normally scheduled with an outage or during planned switching.

How often should MV cables be tested?
There is no single interval. Most asset owners base it on criticality, fault history and previous diagnostic trends, with intervals set by their own maintenance standard and the guidance in IEEE 400.2 and IEC 60502-2. Trend data is only useful if the interval is consistent, so establish a baseline and keep to it.

Can I rent a BAUR cable test system in Canada?
Yes. Frida TD and pin-pointing equipment are available for rental, which is the usual way to run a first diagnostic campaign or cover a short-term programme before purchase.

View the BAUR viola TD Talk to RCC About Cable Diagnostics

* Capability descriptions are summarised from BAUR published product information and RCC Electronics product listings; electrical specifications, test capacities and supported standards should be confirmed against the current BAUR datasheet before purchase. Standard numbers are listed as common industry references — test voltages, durations and evaluation criteria are governed by the current standard text and the asset owner's specification.