Partial Discharge Testing Equipment for Hire

Partial discharge is the small, localised electrical breakdown that occurs in regions of an insulation system where the local electric stress exceeds the dielectric strength of the material. Voids in epoxy, defects in cable joints, contamination on switchgear bushings, water trees in cable insulation and floating particles in GIS will all generate measurable PD long before they cause an outright failure. PD testing detects, quantifies and locates these defects, and is widely accepted as the leading indicator of insulation-system condition on transmission and distribution assets.

Two broad measurement approaches are in use. Conventional PD measurement per IEC 60270 detects pulse currents through a coupling capacitor, expresses results in picocoulombs and is the reference method for type tests, factory acceptance tests and offline site measurements. Non-conventional methods covered by IEC TS 62478 use acoustic, transient earth voltage (TEV) and ultra-high-frequency (UHF) sensors to detect PD on energised assets without de-energisation. Both approaches are represented in the Megavar hire fleet, with Omicron’s MPD 600 platform covering IEC 60270 conventional measurement and EA Technology’s UltraTEV Plus² covering online TEV and ultrasonic surveys.

Cable PD testing is governed by IEEE 400.3 and IEC 60885-3, transformer PD testing falls under IEC 60076 series, GIS PD testing under IEC 62271-203, and rotating machine PD testing under IEC 60034-27 series. Megavar’s commissioning engineers perform PD measurement against these standards on transmission and distribution networks every month, including on BESS step-up transformers, transmission GIS, distribution switchgear surveys and HV motor stator windings. Hire from our offices in Hobart, Launceston, Adelaide and Newcastle, with delivery Australia-wide.

PD testing is applied across the major HV asset classes, with measurement methods adapted to the asset type and the test scenario.

Switchgear and substation surveys

Online PD surveys on energised MV and HV switchgear use a combination of TEV (transient earth voltage), airborne ultrasonic and contact ultrasonic sensors. The walkaround survey is non-invasive, takes a single shift on a typical substation, and identifies the panels and cubicles where PD activity warrants further investigation. The EA Technology UltraTEV Plus² is a recognised industry standard for this work in Australia and worldwide.

Cable joint and termination diagnostics

Offline PD measurement on cables is normally combined with a VLF or AC resonant withstand test, providing both an acceptance result and a sensitive diagnostic in a single site visit. The PD measurement system synchronises with the test voltage waveform to produce a phase-resolved partial discharge (PRPD) pattern, which an experienced diagnostic engineer interprets to localise activity to a joint, termination or insulation defect. IEEE 400.3 and IEC 60885-3 set out the test methods.

Transformer factory acceptance and site testing

PD measurement on transformers is required by IEC 60076 during factory acceptance and is performed at site after major works such as rewinds or relocations. Offline measurement uses the conventional IEC 60270 method with coupling capacitors at each high-voltage bushing. UHF measurement using internal couplers or oil-valve-mounted sensors complements the conventional method on large transformers and is increasingly specified on transmission-class units.

GIS commissioning and condition assessment

Gas-insulated switchgear is PD-tested at FAT and at site commissioning per IEC 62271-203. UHF PD measurement is the dominant method on GIS because the wave structure of the GIS itself acts as a low-loss waveguide for PD signals at UHF frequencies, allowing detection of defects that would not be visible to conventional measurement. Megavar performs UHF PD measurement on GIS commissioning projects using the MPD 600 platform with UHF couplers.

Rotating machine stator winding tests

PD measurement on HV motor and generator stator windings, governed by the IEC 60034-27 series, is one of the most useful tools for assessing winding insulation condition between major overhauls. Online PD measurement using stator slot couplers is a long-running asset management practice on large machines; offline PD measurement during a planned outage gives a more controlled measurement environment with the stator de-energised and the test voltage applied in steps.

PD testing is split between two distinct operating modes, and the right method depends on what you are trying to learn and what access the asset permits.

Online PD measurement

Online measurement is performed with the asset energised and in service, using non-conventional sensors that do not require electrical connection to live parts. TEV and ultrasonic sensors detect PD activity through the metallic enclosure or by airborne acoustic coupling. Online measurement is the standard approach for survey-based asset management programmes because it requires no outage, no de-energisation and no scheduling negotiation with operations. The trade-off is that quantitative comparison against IEC 60270 acceptance limits is not possible and the result is always interpreted as a relative indicator of activity rather than an absolute pC measurement.

Offline PD measurement

Offline measurement is performed with the asset de-energised and an external test voltage applied through a controlled HV source. The conventional IEC 60270 method gives a quantitative result in picocoulombs, comparable across measurements and against published acceptance limits. Offline measurement is required for type tests, factory acceptance tests, after-laying cable acceptance tests and any project specification that calls for compliance with IEC 60270. The trade-off is the outage cost, the additional planning, and the requirement for a calibrated HV source matched to the asset under test.

PD testing equipment sits at the most specialised and expensive end of the HV diagnostic fleet. Even tier-one Australian utilities frequently hire rather than buy, because measurement competency is more critical than equipment ownership and the equipment becomes obsolete faster than equivalent withstand test sets.

• You need offline conventional PD measurement on a single project
• You need an online PD survey carried out by experienced operators
• Your team has not been trained on PD pattern interpretation
• You need transformer or GIS PD measurement with UHF couplers and supporting accessories
• The diagnostic outcome matters more than equipment ownership
• You want results interpreted by engineers who measure PD every month

• Your team performs PD surveys as a routine asset management activity
• You have qualified PD engineers in-house with current measurement competencies
• Your network covers more than 50 distinct PD measurement locations per year
• You can commit to ongoing manufacturer training and software updates
• Your asset register justifies a multi-year diagnostic programme
• Your organisation can absorb 3 to 5 year obsolescence on the measurement platform

PD testing is one of the most demanding HV diagnostic disciplines. Equipment ownership is necessary but not sufficient. The measurement is only useful if the operator can identify a calibration drift, recognise a noise source on a busy substation site, distinguish PRPD signatures of corona, surface tracking and internal voids, and translate the result into a clear maintenance recommendation. Megavar’s commissioning engineers do this work every month on transmission and distribution projects.

When you hire PD testing equipment from Megavar you receive: current calibration with traceable certificates, the matched coupling components for the asset class you are testing, and the manufacturer's manuals. Where the project requires the measurement and interpretation done end-to-end rather than equipment alone, we can quote a turnkey diagnostic service. This is the most common arrangement for offline cable PD work, transformer site PD, GIS commissioning PD, and stator winding PD measurement.

Hire periods are flexible from a single-day online PD survey through to multi-month offline measurement campaigns. Delivery is Australia-wide. Call 1300 730 499 or email rentals@megavar.com.au.

Partial discharge testing detects, measures and locates the small localised electrical breakdowns that occur in HV insulation systems before they develop into outright failures. PD activity is the leading indicator of insulation degradation in cables, transformers, switchgear, GIS and rotating machines, and PD testing is widely considered the most sensitive non-destructive diagnostic available for HV assets. Both quantitative offline measurement (per IEC 60270) and qualitative online surveys (per IEC TS 62478) are recognised methods.

For online surveys on energised switchgear and transformers, a handheld TEV and ultrasonic instrument such as the EA Technology UltraTEV Plus² is sufficient for a walkaround survey. For offline IEC 60270 measurement, you need a measurement system (Omicron MPD 600 or equivalent), a coupling capacitor matched to the test voltage and asset class (such as the MCC 210), an HV test source (a VLF set, AC resonant set, or AC dielectric test set depending on the asset and applicable standard), and the appropriate coupling and earthing accessories. The exact configuration depends on the asset under test and the specification.

The reference standard for conventional offline PD measurement is IEC 60270. Asset-specific standards build on this: IEEE 400.3 and IEC 60885-3 for cables, IEC 60076 series for power transformers, IEC 62271-203 for GIS, and the IEC 60034-27 series for rotating machines. IEC TS 62478 covers non-conventional measurement methods including acoustic, TEV and UHF. AS/NZS standards reference IEC 60270 directly for most Australian applications.

Yes. Online PD surveys are performed on energised substations using TEV and ultrasonic sensors that do not require electrical connection to live parts. A typical MV switchroom survey can be completed in a single shift, with results presented as a panel-by-panel risk indicator and recommendations for follow-up. Online surveys are the standard approach for survey-based asset management programmes because they require no outage and can be scheduled with minimal disruption to operations.

The IEC 60270 method captures the PD pulse current as a small charge transfer in the test circuit, then integrates and calibrates it against a known charge injection so that the result is expressed as an apparent charge in picocoulombs. The measurement system applies bandpass filtering to suppress noise and synchronises to the applied test voltage so that PD pulses can be plotted on a phase-resolved partial discharge (PRPD) pattern. The PRPD pattern is the primary output that an experienced diagnostic engineer uses to identify the type and likely location of PD activity.

Yes. Megavar provides full PD diagnostic services using the equipment in this rental fleet, including measurement, PRPD pattern interpretation, defect classification and a written diagnostic report. This is a common arrangement for offline cable PD work, transformer site PD, GIS commissioning PD and rotating machine stator PD measurement. Contact us with the asset class, voltage level and project schedule and we will quote a complete scope.