Insulation Resistance Testing Equipment for Hire

Megavar supplies diagnostic insulation resistance testers for hire across Australia, supporting acceptance testing, commissioning verification, preventive maintenance, and fault investigation on high voltage cables, rotating machines, transformers, and switchgear. The hire fleet covers the Megger MIT range at two test voltages: the MIT 5 kV for the bulk of HV insulation diagnostics, and the MIT 10 kV for the highest voltage class assets and the most demanding diagnostic work. The same instruments are used by Megavar commissioning engineers on substation, BESS, and renewable energy projects every week.

Insulation resistance testing is the first line of evidence on the condition of electrical insulation. A simple spot reading confirms an asset is safe to energise, but the diagnostic value comes from the time-based tests that a high voltage insulation tester performs: the polarisation index, which compares the ten-minute reading to the one-minute reading, and the dielectric absorption ratio, which compares the sixty-second reading to the thirty-second reading. Both reveal moisture ingress and insulation ageing that a spot reading cannot. On HV plant the test voltage matters: insulation that passes at 1 kV can still fail under the stress of a 5 kV or 10 kV diagnostic test that approaches the conditions the insulation sees in service.

The Megavar insulation resistance hire fleet is built on the Megger MIT diagnostic range, the established high voltage insulation tester family in heavy use across Australian utilities, generators, and engineering firms. The instruments deliver guarded measurement to the tera-ohm range, programmable test voltages, automatic polarisation index and dielectric absorption calculation, dielectric discharge testing, and step-voltage and ramp-voltage modes for breakdown investigation. Test results store on the instrument and download to the Megger software for trend comparison against previous tests on the same asset, which is the basis of any condition-based maintenance programme. Hire from our offices in Hobart, Launceston, Adelaide and Newcastle, with delivery Australia-wide, from a team that performs insulation diagnostics as a regular part of substation commissioning, cable acceptance, and rotating machine maintenance scopes.

The fleet supports the full range of HV insulation diagnostic scenarios across utility, industrial, generation, and renewable energy sites.

HV cable acceptance and maintenance testing

Insulation resistance testing is a standard step in cable acceptance and maintenance, performed alongside VLF withstand and tan delta diagnostics. The polarisation index and dielectric absorption tests detect moisture ingress at terminations and joints before it develops into a fault. The MIT 5 kV and 10 kV both perform timed PI and DAR tests automatically and store the full resistance-versus-time curve for analysis.

Rotating machine insulation diagnostics

Generator and large motor stator winding insulation is assessed by polarisation index at 5 kV or 10 kV depending on the machine voltage class, following IEEE 43 for the recommended practice. The guarded measurement terminal on the MIT range isolates the winding under test from surface leakage and end-winding current, which is essential for a meaningful PI on a large machine.

Transformer and switchgear insulation testing

Winding-to-winding and winding-to-earth insulation resistance on transformers, and phase-to-earth insulation on switchgear, are routine acceptance and maintenance measurements. The diagnostic test voltages and the dielectric discharge test on the MIT range distinguish genuine insulation degradation from temporary surface effects.

Commissioning verification on substation and renewable plant

Insulation resistance verification on primary plant, cables, and auxiliary systems is a normal hold point in substation, solar farm, wind farm, and BESS commissioning. Megavar engineers perform these tests as a regular part of commissioning scopes, which is why the hire fleet is maintained to commissioning standard.

Standards referenced

IEEE 43 (rotating machine insulation, polarisation index), IEEE C57.12.90 and IEEE C57.152 (transformers), IEEE C57.13.1 (CT secondaries), IEEE 400 (cables) and asset-specific IEC standards for the plant under test, and the relevant Australian network service provider commissioning specifications. Megavar can develop project-specific insulation test plans against the standards and acceptance values that apply to the asset.

Diagnostic high voltage insulation testers carry a meaningful capital cost, an annual calibration cycle, and software that is periodically revised by the manufacturer.

• You need a 5 kV or 10 kV diagnostic tester for a single acceptance, commissioning, or maintenance campaign
• Capital is constrained or the project rate does not justify outright purchase of a current-generation diagnostic tester
• Calibration and freight on owned equipment would exceed hire cost over the project life
• Your scope is short and the unit would otherwise sit idle between projects

• Your team performs HV insulation diagnostics on more than 60 days per year
• You have in-house test engineers competent on the PI, DAR, and dielectric discharge workflow
• You can amortise the unit over its 7 to 10 year service life
• Your asset programme commits to a multi-year insulation trend baseline
• You require permanent on-call availability that hire cannot guarantee

Megavar is a specialist HV testing and commissioning firm with offices in Hobart, Launceston, Adelaide, Newcastle and Gladstone. We perform insulation diagnostics as a regular part of substation commissioning, cable acceptance, and rotating machine maintenance work for ElectraNet, TasNetworks, Downer, Acciona, Zinfra/Jemena, and renewable energy developers across Australia. 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 insulation resistance testing equipment from Megavar you receive: full current calibration with traceable certificates, the complete test and guard lead set, and a configuration tailored to your scope. Where the project demands a turnkey insulation diagnostic survey rather than equipment hire alone, we can quote on the full service. Hire periods are flexible from a single-day acceptance check through to multi-month maintenance campaigns. Delivery is Australia-wide. Call 1300 730 499 or email rentals@megavar.com.au.

An insulation resistance tester, often called a megohmmeter or by the brand name Megger, applies a known DC test voltage across electrical insulation and measures the resulting leakage current to calculate insulation resistance. A diagnostic high voltage tester goes further than a simple spot reading by performing timed tests, the polarisation index and dielectric absorption ratio, and a dielectric discharge test, which reveal moisture ingress and insulation ageing that a single reading cannot. The Megavar fleet covers the Megger MIT diagnostic range at 5 kV and 10 kV.

The test voltage should match the voltage class of the asset and the acceptance specification. Low voltage equipment is typically tested at 500 V or 1 kV, but HV cables, transformers, switchgear, and rotating machines are tested at 2.5 kV, 5 kV, or 10 kV so the diagnostic test approaches the stress the insulation sees in service. The Megavar fleet provides 5 kV and 10 kV diagnostic testers for HV plant.

There is no single universal pass figure; acceptance depends on the asset type, its voltage class, temperature, and the applicable standard. The more meaningful diagnostic is the trend over time and the time-based ratios. A polarisation index above 2 generally indicates dry, sound insulation on a rotating machine per IEEE 43, while a value near 1 suggests moisture or contamination. Comparing the current result against previous tests on the same asset, corrected for temperature, is the basis of any condition assessment.

The polarisation index is the ratio of the insulation resistance measured at ten minutes to the resistance measured at one minute, during a continuous test at constant voltage. Sound, dry insulation continues to increase in resistance over the ten-minute period, giving a high ratio. Wet or contaminated insulation reaches a steady value quickly, giving a ratio close to 1. The Megger MIT range calculates the polarisation index automatically and stores the full resistance-versus-time curve.

The difference is the maximum diagnostic test voltage. The 5 kV unit covers the bulk of HV cable, transformer, switchgear, and motor insulation diagnostics. The 10 kV unit is required for the highest voltage class assets and large generator stator windings, where the acceptance specification or the asset voltage class calls for a 10 kV test so the diagnostic approaches in-service stress. Both units perform the same polarisation index, dielectric absorption, and dielectric discharge tests; the 10 kV simply extends the available test voltage.

The dielectric discharge test measures the reabsorption current one minute after a timed insulation test is de-energised and the insulation is allowed to discharge. It is sensitive to ageing and deterioration in multi-layer insulation systems, particularly in cables and transformer windings, and detects problems that the polarisation index alone may miss. The Megger MIT diagnostic range performs the dielectric discharge test automatically as part of the diagnostic test sequence.

The guard terminal diverts surface leakage current away from the measurement circuit, so the instrument measures only the volume resistance through the insulation rather than the combined volume and surface leakage. On a contaminated or humid surface, or on a large machine winding with significant end-winding leakage, guarding is essential for a meaningful result. The Megger MIT range provides a dedicated guard terminal.

Yes. Megavar performs full insulation diagnostic surveys using the equipment in this rental fleet, including test planning, on-site execution, result interpretation, and reporting against IEEE 43 and the relevant acceptance specifications. If your project requires a turnkey survey rather than equipment hire alone, contact us with the asset type, voltage class, the standard or specification that applies, and the test window, and we will quote a full scope.