| Publisher | IEEE |
|---|---|
| Type | Guide |
| Scope | Guidance on field testing of shielded power cable systems using very low frequency (VLF) voltage, for withstand and diagnostic purposes. |
| Who uses it | Cable testing technicians, utility and industrial maintenance engineers, commissioning teams, cable jointers and asset managers. |
| Edition note | Refer to the publisher for the current edition. |
What It Is
IEEE 400.2 is the IEEE guide for testing shielded power cable systems in the field using very low frequency voltage, typically at frequencies well below power frequency, with 0.1 Hz being the most common. Because a long cable behaves as a large capacitor, energizing it at power frequency requires heavy, high-power test equipment. Reducing the frequency greatly reduces the reactive power needed, which makes portable test sets practical for medium-voltage cables.
The guide covers two broad uses of VLF. In withstand testing, the cable system is held at an elevated voltage for a defined period to reveal defects that would fail in service. In diagnostic testing, measurements such as dissipation factor (tan delta) and, with suitable equipment, partial discharge are used to assess the overall condition of insulation and accessories. It discusses waveforms, test voltages, durations, interpretation of results and safety considerations for acceptance, installation and maintenance tests.
Why It Matters
Cable failures cause outages, expensive excavation and repair, and safety hazards for workers and the public. Field testing after installation confirms workmanship on joints and terminations, and testing during service supports condition-based maintenance and replacement planning.
VLF testing also replaced much of the historic use of high-voltage DC testing on extruded dielectric cables, which can be harmful to aged insulation. Understanding the guide helps engineers choose an appropriate test, interpret results consistently and avoid both missed defects and unnecessary damage. Testing medium-voltage cables is itself hazardous work. Test terminals, remote cable ends and adjacent circuits must be controlled, and cables must be discharged and grounded after testing because they can store a dangerous charge. Competent personnel combine the guidance in IEEE 400.2 with their organization's electrical safety procedures.
Key Concepts
- Very low frequency (VLF) — an AC test voltage at a frequency far below power frequency, chosen to reduce the reactive power needed to test long cables.
- Withstand test — a pass or fail test in which the cable system must hold an elevated voltage for a set time without breakdown.
- Tan delta (dissipation factor) — a measure of dielectric losses in insulation; its value, stability and change with voltage indicate insulation condition.
- Partial discharge — localized electrical discharges within insulation or accessories that indicate defects and can be measured under some VLF test arrangements.
- Test waveforms — VLF sources produce sinusoidal or cosine-rectangular waveforms, which affect how results are interpreted.
- Acceptance, installation and maintenance tests — test categories for new cables, newly installed systems and systems already in service, with different test levels.
Who Should Know It
- Cable testing and diagnostic technicians
- Cable jointers and termination specialists
- Utility and industrial maintenance engineers
- Commissioning engineers for medium-voltage systems
- Asset managers planning cable replacement
Related Standards
- IEEE 400 — the omnibus IEEE guide to field testing and evaluation of shielded power cable insulation; IEEE 400.2 is one of its companion documents.
- IEEE 400.3 — the companion IEEE guide for partial discharge testing of shielded power cable systems in a field environment.
- IEEE 404 — covers cable joints, a frequent source of defects found by VLF testing.
- IEC 60502 — the IEC standard for extruded cables and accessories, including factory and after-installation test requirements.
How ASEEE Uses It
ASEEE cable and testing programs map learning outcomes and assessments to IEEE 400.2 concepts, including test selection, test setup, safety, and interpretation of withstand and tan delta results. See related ASEEE programs.
ASEEE Programs Referencing This Standard
Educational summary only. ASEEE is not the publisher of this document and this page does not reproduce or replace it. Always consult the current official edition from IEEE for requirements.