Voltage Transformer Testing Equipment for Hire

Voltage transformer testing is a precision discipline with low tolerance for instrument error. A VT that reports the wrong ratio or fails its polarity check propagates the fault into every protection, metering, and control function downstream. The IEC 61869 series (61869-1 general requirements, 61869-3 inductive VTs, 61869-5 capacitive VTs), AS 61869, and IEEE C57.13 set out the test methods and accuracy classes Australian asset owners and contractors are expected to verify. Megavar’s VT hire fleet is built around the test methods these standards specify, on instruments accurate enough to verify the VT classes that protection and revenue metering depend on.

The fleet covers the four test scenarios that VT commissioning, acceptance, and maintenance work most often demand. Ratio and polarity testing on the Omicron CPC 100 multifunctional primary test set, capable of verifying VT accuracy classes through automated test plans rather than manual point-by-point measurement. Insulation resistance pre-testing on the Megger MIT 5 kV and 10 kV testers for primary winding integrity ahead of any higher-voltage applied potential test. Tan delta and dissipation factor testing on capacitive voltage transformers using the Omicron CP TD1 paired with the CPC 100 platform, supplemented by the Omicron MCC 210 capacitive coupling unit where the CVT requires a dedicated coupling capacitor for both tan delta and partial discharge measurement.

Where the project demands higher-voltage applied potential testing on inductive VT primaries, the Megavar AC withstand fleet (covered on the HV testing rental page) is available alongside the VT-specific equipment listed here. Hire from our offices in Hobart, Launceston, Adelaide and Newcastle, with delivery Australia-wide, from a team that performs VT testing as a core service on protection and metering scopes.

The fleet supports four broad voltage transformer testing scenarios across inductive and capacitive instrument transformer populations.

Factory and site acceptance testing on new VTs

Acceptance testing on new inductive and capacitive voltage transformers verifies that the unit meets its nameplate accuracy class, ratio, polarity, and dielectric performance before energisation. IEC 61869-1 sets the general requirements, IEC 61869-3 covers inductive voltage transformers, and IEC 61869-5 covers capacitive voltage transformers. The Australian standards series AS 61869 has progressively replaced AS 60044 in alignment with the IEC numbering. Routine site acceptance testing typically includes ratio and polarity verification, primary insulation resistance, and applied potential testing where the project specification calls for it.

Commissioning of protection and metering schemes

VT commissioning is the gate before any protection or metering scheme can be energised. The CPC 100 VTRatio test card verifies VT ratio against the nameplate and exposes wiring errors, polarity reversals, and accuracy class deviations that secondary injection testing cannot detect. Where the protection scheme depends on residual voltage measurement (open-delta or broken-delta connections), the polarity test must be unambiguously verified across all three phases before the scheme is placed in service.

Maintenance and condition assessment

Periodic testing on installed VTs supports asset management on aged populations. For inductive VTs, the maintenance battery typically covers insulation resistance, ratio re-verification, and polarity confirmation if maintenance has disturbed the secondary wiring. For capacitive voltage transformers, tan delta and dissipation factor measurements on the capacitor stack detect insulation degradation in the capacitor elements long before the unit fails in service. CVT failures on transmission networks often follow a recognisable tan delta drift profile across multiple measurement campaigns, which is why utility asset management programmes specify CVT diagnostic testing on a multi-year cycle.

Post-fault verification

After a protection misoperation, secondary system rework, or VT replacement, the testing sequence is normally repeated before the affected scheme is returned to service. The same VTRatio, polarity and insulation resistance test sequence used at commissioning is typically re-run to confirm that the rework has not introduced a new fault and that the VT itself remains within its accuracy class.

VT testing equipment ranges from a hand-held insulation resistance tester at the low-cost end to a multifunctional primary test platform with full diagnostic accessory set at the high-cost end. The hire-versus-buy decision turns on utilisation, capital tolerance, and how often the equipment changes generation.

• You need a VT test platform for one commissioning or acceptance window
• Capital is constrained or commissioning rates do not justify outright purchase
• Calibration and freight on owned equipment would exceed hire cost
• The project demands the latest generation of equipment and current calibration
• You want flexibility to scale up multiple test sets in parallel during a peak window 

• Your team performs VT ratio and polarity testing on more than 50 days per year
• You have in-house protection and primary plant test engineers competent on the platform
• Your projects are remote enough that hire freight outweighs purchase plus calibration
• You require permanent on-call availability that hire cannot guarantee
• Your asset management programme commits to a multi-year CVT condition assessment cycle
• You can amortise the unit over its expected service life of 10 to 15 years 

Megavar is a specialist HV testing and commissioning firm with offices in Hobart, Launceston, Adelaide, Newcastle and Gladstone. We perform voltage transformer testing as a core service on transmission and distribution projects every week, including for ElectraNet, TasNetworks, Downer, Acciona and Zinfra/Jemena. The hire fleet exists because we built it for our own commissioning teams first, and we maintain it to the standard those teams require.

When you hire VT testing equipment from Megavar you receive: full current calibration with NATA-traceable certificates, complete accessory and lead sets, and a configuration tailored to your scope. Where the project demands a turnkey service rather than equipment hire alone, we can quote on the full commissioning scope.

Hire periods are flexible from single-day commissioning checks through to multi-month project rentals. Delivery is Australia-wide. Call 1300 730 499 or email rentals@megavar.com.au.

A standard VT test sequence requires three classes of equipment: an insulation resistance tester for the pre-test check on the primary winding (Megger MIT 5 kV or 10 kV), a multifunctional primary test platform for ratio, polarity, and dielectric testing (Omicron CPC 100), and where the VT is a capacitive type, a tan delta accessory and reference coupling capacitor for diagnostic testing on the capacitor stack (CP TD1 and MCC 210). The exact mix depends on whether the VT is inductive or capacitive, the voltage class, and the standards that apply to the project.