VA-TEK Engineering IEEE 400.2 is the guide that governs field testing of shielded power cable with very low frequency AC at less than 1 Hz. The current edition, IEEE 400.2-2024, replaced the 2013 edition and changed several of the criteria a compliant test is judged against. For anyone specifying a VLF test set or writing an acceptance procedure, those changes are the difference between a result that stands up and one that does not.
Key takeaways
- IEEE 400.2-2024 is the active edition for VLF (< 1 Hz) field testing of shielded cable, replacing 400.2-2013.
- The monitored withstand judging criteria were tightened toward tan delta and partial discharge.
- The 2024 edition is widely reported to have made other changes including a unified basis for the test-voltage table, a longer minimum duration for higher-voltage cable, and a controlled ramp-down requirement.
- Damped AC / oscillating-wave testing is a different standard — IEEE 400.4, currently Inactive – Reserved.
- Secondary summaries of the revision vary; the standard text governs any acceptance decision.
1. What IEEE 400.2 covers
IEEE 400.2 addresses field testing of shielded power cable systems using VLF AC — generally 0.1 Hz and below. It covers the method, the test voltages, the duration, and the criteria by which a test is judged, for both a proof/withstand test and a monitored withstand. Its scope is extruded and laminated insulation systems at distribution and transmission voltages, and it sits alongside the IEC documents that define field test voltages.
It does not cover damped AC (DAC / oscillating wave), which has its own guide. The two are often discussed together but are governed separately — see VLF versus DAC testing.
2. What changed in the 2024 edition
The 2024 edition is a revision, not a rewrite, but several changes move the acceptance criteria. The changes most often cited in technical summaries are:
| Area | Reported change in 2024 |
|---|---|
| Test-voltage basis | The test-voltage table was unified to a single basis, replacing the 2013 arrangement in which sine and cosine-rectangular tests were expressed differently and could not be compared directly. |
| Monitored-withstand criteria | Judging was tightened toward tan delta and partial discharge; the 2013 edition had also allowed leakage current and harmonic measures. |
| Duration | The minimum withstand duration for higher-voltage cable was increased (reported as 30 to 60 minutes). |
| Ramp-down | A controlled, slow de-energisation requirement was added, so the cable is not shocked at the end of a test. |
| Tan delta criteria | Judging tables were added or revised, differentiated by insulation type. |
Two cautions. First, published technical summaries of the revision are not identical to each other, and a summary is not the standard. Second, any acceptance decision should be made against the standard text itself — this article is orientation, not a substitute for reading IEEE 400.2-2024.
3. Monitored withstand — why the criteria matter
A plain withstand test is pass/fail: the cable either holds the voltage for the duration or it breaks down. A monitored withstand is different — the operator watches measured quantities evolve across the hold, and judges the cable from how those quantities behave, not only from whether it survived.
That is why the 2024 tightening of the judging criteria matters. If the accepted evidence is now tan delta and partial discharge, then a test set that can only log a final leakage value is not equipped to support a monitored withstand under the current edition. The measurable quantities decide whether the equipment you are buying can run the test the standard describes. More on the measurements themselves: VLF tan delta testing and VLF partial discharge testing.
4. Duration and intended outcome
Duration and voltage trade against each other: a higher test voltage needs a shorter hold, and a longer hold is not automatically safer, because a VLF test deposits a small cumulative stress in the insulation. The 2024 increase in minimum duration for higher-voltage cable is therefore a meaningful change — it lengthens the hold at the top of the voltage range, and a set must be able to sustain a regulated output for that whole period without drooping. The interaction between voltage, duration and test purpose is set out in VLF test duration and frequency and VLF test voltage selection.
5. Where IEEE 400.2 sits alongside other standards
| Standard | Covers | Status |
|---|---|---|
| IEEE 400.2-2024 | VLF (< 1 Hz) field testing of shielded cable | Active |
| IEEE 400.4-2015 | DAC / oscillating-wave field testing, 5 kV and above | Inactive – Reserved |
| IEC 60060-3 | Field test voltages, including VLF and damped AC | Current |
| GB/T 3048.8-2025 | AC voltage test methods, listing VLF and oscillating wave | Published 2025 |
One procurement note: IEEE 400.4 is currently Inactive – Reserved with a revision under way, so a buyer should confirm its current status before citing it as the governing document for a DAC test.
6. What this means in practice
- Write the procedure against the 2024 edition. Older templates built on 2013 criteria may no longer match the current judging basis.
- Check the equipment against the criteria. If the test is a monitored withstand, the set must be able to measure and record tan delta and partial discharge, not merely a final value.
- Record the basis and the trace. A voltage figure without its basis, and without a voltage-against-time record, cannot be trended or defended later.
- Confirm against the standard text. Use summaries to orient; use the standard to decide.
7. Frequently asked questions
Is IEEE 400.2-2024 in force?
Yes — the 2024 edition is the active version and replaces IEEE 400.2-2013. Confirm the current status on the IEEE SA record before finalising a procedure.
What are the main changes from 2013?
The changes most often cited are a unified basis for the test-voltage table, tighter monitored-withstand criteria based on tan delta and partial discharge, an increased minimum duration for higher-voltage cable, and a controlled ramp-down requirement. Published summaries vary, so verify against the standard.
Does IEEE 400.2 cover damped AC (DAC)?
No. DAC, or oscillating-wave testing, is governed by IEEE 400.4, which is currently Inactive – Reserved. IEEE 400.2 is the VLF guide.
What test set do I need for a monitored withstand?
One that can sustain a regulated sinusoidal output for the full duration and measure the quantities the criteria use — tan delta and partial discharge. A sine-wave VLF set with those diagnostics is the configuration that supports the current edition.
8. Where to go next
For the method end to end, see the VLF cable testing guide. For how a test voltage is chosen under the standard, see VLF test voltage selection, and work the figure for your class with the VLF test voltage calculator; for the equipment decision, the VLF hipot tester buyer’s checklist and cost guide. The VA-TEK VLF range covers 30 to 90 kV peak with sine output, and you can request a configuration quote for the criteria you need to meet.
