Glossary

The intense heat, light and pressure released by an electrical arc fault. It is a serious hazard to anyone working near live equipment.

Related: Arc Flash Assessments

The standard setting out requirements for inverters connected to the grid in Australia and New Zealand, including grid-support functions such as volt-var response.

The coordinated activity of getting the most value from physical assets over their whole life by balancing cost, risk and performance.

Related: Asset Management & Condition

A structured record of an organisation's assets and their key attributes, such as type, location, age and condition.

The combination of an asset's probability of failure and the consequence of that failure, used to prioritise investment.

Related: Invest

A standards organisation that develops technical standards for materials, products and test methods, including many of the tests used to analyse insulating oil.

Astute monitoring service applied to HV cable networks.

Related: Astute HV Monitoring

Continuous PD monitoring system for HV switchgear and cables with automated alerts and reporting.

Related: Astute HV Monitoring

Astute monitoring service applied to HV switchgear.

Related: Astute HV Monitoring

The body that operates Australia's main electricity and gas markets and power systems.

A device or function that automatically restores supply after a transient fault, reducing the length and number of customer interruptions.

Related: VisNet Reclose²

Online self-serve tool giving LV connection capability and budget quotes in minutes.

A relay or controller that automatically operates a transformer's tap changer to keep voltage within set limits.

Related: SuperTAPP SG

Batteries connected to the network to store electricity and release it when needed.

Generation or storage installed on the customer's side of the electricity meter, such as home solar or batteries.

The voltage at which an oil sample fails electrically under standard test conditions. Low values indicate moisture or contamination.

Related: Oil Testing and Diagnostics

A sustained drop in supply voltage below normal levels, short of a complete loss of supply.

A connection between two lengths of cable. Joints are a common source of partial discharge and cable failure.

The maximum current a cable can carry continuously without exceeding its temperature limit, which depends on how and where it is installed.

The fitting that connects a cable end to switchgear, a transformer or an overhead line. A frequent location for partial discharge and failure.

Instrument and service for online PD testing and condition assessment of MV/HV cables.

Tool for locating LV cable faults.

Related: CableSniffer

An automatic switch that interrupts current when a fault is detected, protecting equipment and people.

Off-the-shelf CNAIM-compliant models with data interfaces and Data Loader software.

A common methodology for calculating the health and criticality of electricity distribution assets, giving a consistent measure of the risk of condition-based failure. It covers 25 asset classes, including switchgear, transformers, overhead lines and cables, and is used for regulatory reporting to Ofgem.

Inspection and testing to establish the current health of an asset and the risk of failure.

Related: Condition Assessment Services

EA Technology methodology that combines condition data and engineering knowledge to quantify asset health and risk.

Related: Invest

Measuring condition indicators on assets, continuously or periodically, to detect deterioration early.

Related: Astute HV Monitoring

Maintaining assets based on their measured condition rather than at fixed time intervals.

Related: Condition Assessment Services

Web application that overlays EV charging demand on a network model to find the best chargepoint locations.

The impact if an asset fails, for example on safety, customers, cost and the environment.

Permanently installed sensors that track partial discharge on HV assets around the clock and raise alerts when activity changes, rather than relying on periodic surveys.

Related: Astute HV Monitoring

Partial discharge in air around sharp points or highly stressed conductors. Often heard as a hiss or smelt as ozone; usually low energy but a sign worth investigating.

Sulphur compounds in oil that attack copper and form conductive deposits, which can lead to winding failure.

Cable rating service that calculates cable current ratings.

A polymeric insulation widely used in modern medium and high voltage cables.

An instrument transformer that produces a smaller current proportional to the primary current, for measurement and protection.

Deliberately reducing generation or demand to keep the network within its limits.

Reliability measures showing how many customers lose supply (Customer Interruptions) and for how long (Customer Minutes Lost). Regulators often link network operator incentives to them.

Reducing the carbon emissions from energy use, for example by electrifying heat and transport and switching to renewable generation.

Related: Consultancy

A specific corrosive sulphur compound found in some mineral insulating oils.

A measure of dielectric losses in insulating oil. Rising values indicate contamination or ageing.

Measuring the gases dissolved in transformer oil. The types and quantities of gas point to specific internal faults such as overheating, arcing or partial discharge.

Related: Oil Testing and Diagnostics

Smaller-scale generation, storage and flexible demand connected to the distribution network, such as rooftop solar PV, batteries and EVs.

Related: Network Planning and Connections

A company licensed to own, operate and maintain the electricity distribution network that carries power from the transmission system to homes and businesses in its area.

Related: Network Operators

A company that owns and operates the electricity distribution network, delivering power from the transmission network to homes and businesses in its area.

Related: Network Operators

A distribution network operator that actively manages power flows, flexibility and DER on its network, rather than only building and maintaining it.

Related: Network Operators

The shift from passively running the network to actively managing it in real time as DER and electrification grow.

Measuring contact resistance while circuit breaker contacts are moving, to reveal wear, arcing damage or misalignment.

Protection that detects current flowing to earth and isolates the faulty circuit.

Connecting electrical equipment to the general mass of earth to provide a safe path for fault current and limit dangerous voltages.

Related: Earthing and Lightning Design and Compliance

Pole-mounted LV voltage control product (EcoJoule).

A vehicle powered fully or partly by a battery charged from the electricity network.

Training programme in electrical distribution engineering.

The rules and procedures that govern safe working on or near electrical systems.

Related: Electrical Safety and Compliance

A long-term plan setting out how a network will change to meet future demand, generation and policy goals.

A national plan developed by Energy Networks Australia setting out how Australia's electricity networks should transform to support the energy transition.

Switching energy uses such as transport and heating from fossil fuels to electricity.

The point at which an asset is expected to need replacement because its condition makes continued operation too risky or uneconomic.

The industry body representing electricity and gas network operators in the UK and Ireland. It publishes engineering recommendations such as G99.

The national industry body representing Australia's electricity transmission and distribution and gas distribution businesses.

The technical requirements for connecting generation and energy storage to distribution networks in Great Britain, published by the Energy Networks Association.

The chargers and supporting network connections needed to charge electric vehicles.

Related: VisNet Connect

The effect of EV charging demand on local network capacity, voltage and loading.

A cap on how much power a customer's generation can export to the network. Static limits are fixed; dynamic limits change with real-time network conditions.

The highest voltage levels, used mainly on transmission and sub-transmission networks.

The maximum current that would flow at a point in the network during a short circuit. Equipment must be rated to withstand and interrupt it.

Related: Fault Level Study

Finding where on a cable or line a fault has occurred, to reduce search and repair time.

Related: CableSniffer

Adjusting generation or demand in response to network needs, often for payment, to avoid or defer reinforcement.

Partial discharge from a loose or unearthed metal part that becomes electrically charged.

Voltage control company that joined EA Technology.

Related: Voltage Control and Monitoring

Measuring furanic compounds released into oil as paper insulation ages. It gives an indication of how much life the paper insulation has left.

Related: Oil Testing and Diagnostics

Monitoring that detects when an LV fuse has operated, so supply loss can be found and fixed faster.

Related: VisNet Hub

Compact switchgear where live parts are sealed inside a metal enclosure filled with insulating gas, usually SF6.

Related: UHF Barrier Spacer Sensor

Software that stores and maps network assets by location.

Showing that new generation or storage meets the technical rules for connecting to and operating on the network.

The part of the network closest to customers, where solar PV, batteries and EVs connect. Grid-edge intelligence means monitoring and processing data at this level.

Related: VisNet View

Connecting electrical equipment and systems to the earth so fault current has a safe path to flow, protecting people and equipment and limiting dangerous voltages. Also known as earthing.

Related: Earthing and Lightning Design and Compliance

UltraTEV Plus² feature that prompts the user through the PD survey and interprets results on screen.

Related: UltraTEV Plus²

A single score that combines condition, age and other data to show how degraded an asset is and how close it is to end of life.

Related: Invest

Clamp-on high frequency current transformer sensor for cable PD testing with UltraTEV Plus².

Related: HFCT

A clamp-on sensor fitted around a cable's earth connection that picks up the high-frequency current pulses caused by partial discharge. Mainly used for online cable PD testing.

Related: HFCT

Voltage levels above medium voltage, used for bulk power transfer on transmission and sub-transmission networks. Exact thresholds depend on the applicable standard.

An offline test that applies a voltage above normal operating level for a set time to confirm that insulation can withstand it.

The amount of DER, such as solar PV export, that a section of network can accept without breaching voltage or thermal limits.

Related: Network Planning and Connections

Hosting capacity expressed as the amount of power, in kW, that each customer connection can export to the network without breaching voltage or thermal limits.

Tool that produces HV connection quotes for network operators in minutes.

International standard giving specifications for checking and reusing SF6 gas taken from electrical equipment.

International standard for sampling gases and oil from oil-filled electrical equipment for dissolved gas analysis.

An international standard for communication between devices in substations and power system automation.

IEEE guide for field testing shielded power cable systems using very low frequency (VLF) voltage, including Tan Delta acceptance values.

The thermal energy a worker could be exposed to at a given distance during an arc flash. It is used to set safe working boundaries and select protective clothing.

Related: Arc Flash Assessments

Using a thermal camera to find hot spots on electrical equipment, such as loose connections or overloaded components, without touching it.

Related: Thermographic Surveys

A professional association for electrical and electronic engineering that publishes widely used standards, such as IEEE 400.2 for field testing of power cables.

The tension at the boundary between oil and water. It falls as oxidation products and contaminants build up, so it is an early indicator of oil ageing.

Partial discharge inside voids, cracks or gas pockets within solid insulation.

An association that develops standards for electrical acceptance and maintenance testing and certifies electrical testing technicians.

Risk-based asset investment decision support tool that analyses asset health and risk.

Related: Invest

The international family of standards for asset management. ISO 55001 sets out the requirements for an asset management system that can be independently certified.

Air terminals, down conductors and earthing that safely conduct a lightning strike to ground and protect a structure.

Related: Earthing and Lightning Design and Compliance

A cable diagnostic technique that analyses how a cable responds to signals across a range of frequencies to locate and assess insulation degradation along its length.

Taking oil samples from oil-filled switchgear while it remains energised, so its condition can be assessed without an outage.

Related: Oil Testing and Diagnostics

A study of how power flows through a network under different conditions, checking that voltages and equipment loadings stay within limits.

Related: Load Flow Study

Technologies such as heat pumps, EVs and solar PV that reduce carbon emissions but add new demand or generation to the network.

The lowest voltage level of the distribution network, supplying homes and businesses directly. It typically covers voltages up to 1 kV AC.

Related: LV Network Monitoring

Predicting how demand and generation on the low voltage network will change, for example as EVs and heat pumps are adopted.

Related: VisNet Forecast

Measuring voltage, current and power flows on the low voltage network, usually at the substation or on overhead lines, to see what is happening at the grid edge.

Related: LV Network Monitoring

Designing new or reinforced low voltage circuits so they meet voltage, thermal and safety limits.

Related: VisNet Design

Whether customers on the low voltage network receive supply within required voltage and reliability limits.

Software platform on VisNet Hub that hosts apps from different suppliers through an open API (developed on the OpenLV project).

Related: VisNet Hub

A review of how well an organisation's maintenance practices match its assets' needs and recognised standards.

The documented approach that sets how, when and why each type of asset is maintained.

Laboratory testing of the materials in failed or aged components to support failure investigations.

Related: Failure and Forensic Investigations

The voltage level between low and high voltage, typically above 1 kV and up to around 35 kV. It is used to distribute power to local substations and larger customers.

A local energy system with its own generation and often storage that can run connected to the main grid or independently.

Laboratory imaging used in failure investigations to examine internal damage in components without, or before, cutting them open.

Related: Failure and Forensic Investigations

The amount of water in insulating oil. High moisture lowers dielectric strength and speeds up the ageing of paper insulation.

Balancing the greenhouse gases emitted with those removed from the atmosphere, so the overall total is zero.

Related: Consultancy

Increasing the capacity of an electricity network, for example by upgrading transformers, replacing cables or adding new circuits, so it can carry more demand or generation.

The process of connecting new demand or generation to the network, including assessing capacity, cost and design.

Related: VisNet Connect

Building a digital model of an electrical network to analyse its performance and plan changes.

Related: Network Planning and Connections

Upgrading network capacity, for example with larger cables or transformers, to meet higher demand or generation.

Electrical signals from sources other than partial discharge that can look like PD. Good instruments and analysis separate genuine PD from noise to avoid false alarms.

Partial discharge testing carried out with the asset disconnected and energised from a separate test supply. This gives lower background noise and allows test voltages above normal working voltage.

Related: Offline Cable Testing

Electrical tests carried out on a de-energised transformer to assess windings, insulation and core condition.

Related: Offline Transformer Testing

The Office of Gas and Electricity Markets, the regulator for the electricity and gas markets in Great Britain.

The level of acidic compounds that form as oil oxidises. High acidity speeds up paper degradation and can lead to sludge.

Taking a representative sample of insulating oil for laboratory analysis. Correct sampling is essential for reliable results.

Related: Oil Testing and Diagnostics

Online portal giving clients access to their oil analysis results.

Related: Oil Testing and Diagnostics

Partial discharge testing carried out while the equipment stays energised and in service, so no outage is needed.

Related: Condition Assessment Services

Protection that disconnects a circuit when current exceeds a set level for a set time.

Conductors carried on poles or towers, as opposed to underground cables.

Related: VisNet View

An additive that slows down oil oxidation. Its level is tested to know when the oil needs re-inhibiting.

The paper wrapped around transformer windings. Its condition largely determines how long the transformer will last.

An older type of cable insulated with oil-impregnated paper, still common in many distribution networks.

What is Partial Discharge?

Partial discharge is a localized electrical discharge within insulation, typically caused by defects, ageing, contamination, or poor installation. It does not immediately bridge the insulation, but it is a strong indicator that deterioration is underway and failure risk is increasing.

What are the causes of PD?

• Voids/bubbles within solid or liquid insulation

• Surface contamination or tracking

• Poor operating environment

• Incorrect system design or installation

• High humidity, dust and poor substation conditions

What are the types of PD?

• Internal PD– Occurs within voids, cracks, or gas pockets inside solid insulation.

• Surface PD – Discharge along the surface of insulating material, often due to contamination or moisture.

• Corona discharge – Ionization around sharp points or conductors in air; usually low‑energy but detectable.

• Floating Electrode PD– Happens when an ungrounded/loose metallic part becomes electrically active.

Introductory PD survey service.

A site inspection of HV assets using handheld PD instruments to find and rank equipment showing PD activity, usually repeated at set intervals.

Related: Partial Discharge Surveys

An offline cable test that measures the magnitude and location of PD along a cable route and presents it as a map, so specific joints or sections can be targeted.

Related: Offline Cable Testing

HFCT sensors installed permanently on cables to allow future PD testing without re-access.

UltraTEV Plus² accessory for phase-locked PRPD recording.

Related: Wireless Phase Reference

A reference signal that synchronises PD measurements to the supply voltage waveform, so readings can be plotted against phase for PRPD analysis.

Related: Wireless Phase Reference

A plot of PD pulse magnitude against the phase angle of the supply voltage. The shape of the pattern helps identify the type of PD and separate genuine PD from noise.

A unit of electric charge (one trillionth of a coulomb) commonly used to express the apparent charge of a partial discharge pulse.

Accessory for checking polarity during LV installation.

Related: Polarity Test Pen

Toxic chemicals once used in transformer oils. Testing confirms whether oil is contaminated and needs to be handled and disposed of under regulation.

Investigating failed electrical equipment to establish the root cause and prevent it happening again.

Related: Failure and Forensic Investigations

How closely the voltage and current supplied stay within expected limits. Poor power quality can damage equipment or disrupt operations.

Related: Power Quality Survey/Study

Engineering studies that model an electrical network to check it is safe, compliant and performing as intended.

Related: Power Systems Studies

A review of a site's electrical system design, condition and operation against standards and best practice.

EA Technology training team / brand.

Testing new cables or equipment to confirm their condition before they are put into service.

Spotting intermittent, early-stage faults such as developing cable faults before they become permanent outages.

Related: VisNet Hub

Using condition data and trends to predict when an asset is likely to fail, so action can be taken beforehand.

Injecting test current through the primary circuit to check the whole protection system end to end, including current transformers, relays, wiring and the breaker.

The likelihood that an asset will fail within a given period, often derived from its health index.

A customer who both consumes and produces electricity, for example with rooftop solar.

Setting protection devices so that the one nearest a fault operates first, isolating only the faulty part of the network.

Related: Protection Coordination Study

A device that monitors current or voltage and signals a circuit breaker to trip when it detects a fault.

The part of AC power that supports voltage and magnetic fields in equipment but does no useful work. Managing it helps control network voltage.

A designated area where renewable generation, storage and transmission are developed together to connect large amounts of clean energy efficiently.

Power flowing from the LV network back towards higher voltage levels, usually because local generation such as solar PV exceeds local demand.

The price control framework Ofgem uses to set the revenue that network companies in Great Britain can earn, based on Revenue = Incentives + Innovation + Outputs. RIIO-ED periods apply to electricity distribution.

Cables that run up and across multi-occupancy buildings to supply individual flats.

Prioritising asset investment according to how much risk each intervention removes for the money spent.

Related: Invest

A structured process for finding the underlying cause of a failure rather than just its symptoms.

Related: Failure and Forensic Investigations

Testing motors and generators to assess the condition of their insulation and their overall health.

Related: Rotating Machine Condition Assessment

Injecting test signals directly into a protection relay, without primary current, to confirm its settings and timing.

Compounds formed when SF6 is broken down by electrical arcing, especially when moisture is present. They reduce insulation performance and can damage internal components.

Testing SF6 gas for purity, moisture and acidity to confirm it is still fit for use in switchgear.

An electricity network that uses monitoring, communications and automation to manage supply and demand more efficiently.

A digital electricity meter that records consumption in detail and sends readings remotely.

Expansion port on UltraTEV Plus² that connects additional sensors.

Related: UltraTEV Plus²

Technology that converts sunlight directly into electricity using semiconductor panels.

Related: Renewables

The legally required range within which the voltage supplied to customers must be kept, set by regulation as a tolerance around the nominal supply voltage.

Related: Voltage Control and Monitoring

Long-term planning that links asset decisions to an organisation's objectives, risk appetite and budget.

A site where voltage is transformed and circuits are switched and protected.

Platform from which UltraTEV Plus² software updates are downloaded.

A gas used for insulation and arc quenching in switchgear. It is highly effective but a very potent greenhouse gas, so its use and handling are tightly regulated.

Voltage control relay for transformer tap changers.

Related: SuperTAPP SG

Systems that monitor and control network equipment remotely from a control centre.

Partial discharge along the surface of insulation, usually caused by contamination or moisture. It can leave carbonised tracks that weaken the insulation over time.

Equipment that switches, controls and protects electrical circuits, such as circuit breakers, switches and fuses, typically housed in substations.

Related: Asset Management & Condition

A test that measures dielectric losses in insulation. Rising tan delta values indicate bulk insulation ageing such as water treeing, so it complements PD testing.

Related: Offline Cable Testing

A device that changes a transformer's turns ratio to adjust its output voltage. An on-load tap changer does this while the transformer stays energised.

Related: Voltage Control and Monitoring

Control unit for transformer tap changers.

Related: Voltage Control and Monitoring

Supply of spares for tap changers.

Related: Tapchanger Maintenance

Modelling that combines engineering and cost analysis to compare options and find the best-value solution.

Probe used with UltraTEV Plus² to locate the source of TEV activity within switchgear.

Related: TEV Locator Probe

Maintaining assets at fixed intervals regardless of their actual condition.

Fundamentals voltage control offering for voltage compliance on a low carbon grid.

Related: Voltage Control and Monitoring

Inspection of overhead line tower foundations for corrosion and deterioration that could affect structural integrity.

Equipment that transfers electrical energy between circuits while changing the voltage, for example stepping medium voltage down to low voltage for local distribution.

Related: Offline Transformer Testing

Questionnaire used to gather transformer background information for health index assessment.

Related: Oil Testing and Diagnostics

Laboratory testing of insulating oil samples to assess the internal condition of a transformer or oil-filled switchgear without taking it apart.

Related: Oil Testing and Diagnostics

A short voltage pulse that appears on the metal casing of switchgear when partial discharge occurs inside it. TEV sensors detect these pulses from the outside, without opening the equipment.

Related: UltraTEV Plus²

The electromagnet that releases a circuit breaker's mechanism to open its contacts when protection signals a trip.

Recording the current drawn by a circuit breaker's trip coil as it operates. The resulting profile reveals mechanical or electrical problems in the tripping mechanism.

The rated voltage between a cable conductor and earth. It is used as the reference for setting cable test voltages.

UHF sensor that detects PD in gas insulated switchgear through the barrier spacer.

Related: UHF Barrier Spacer Sensor

Directional UHF antenna used to pinpoint the source of PD.

Related: UHF Directional Antenna

UHF sensor accessory for detecting and locating PD, particularly in GIS.

Related: UHF Receiver

Detecting partial discharge from the electromagnetic signals it radiates in the UHF band. Particularly effective in gas insulated switchgear and for locating the source of PD.

Related: UHF Receiver

UltraTEV Plus² accessory for PD detection on specific asset types.

Related: UltraBolt

Parabolic ultrasonic accessory for inspecting overhead assets from a distance.

Related: UltraDish

Ultrasonic probe used in contact with equipment to detect internal PD.

Related: Ultrasonic Contact Probe

Flexible ultrasonic sensor for reaching awkward locations.

Related: Ultrasonic Flexi-Sensor

Detecting partial discharge from the ultrasonic sound it produces. Best suited to surface discharge and corona on air-insulated equipment, cable terminations and overhead assets.

Related: Ultrasonic Contact Probe

The range of sensors and add-ons that extend UltraTEV Plus² to more asset types.

Related: UltraTEV Accessories

Handheld PD detection device in the UltraTEV range.

Related: UltraTEV Detector²

Cloud-based platform that stores UltraTEV survey data, tracks trends and gives access to expert analysis.

Handheld multi-sensor PD detection instrument with built-in TEV and ultrasonic sensors, guided mode and cloud data sync.

Related: UltraTEV Plus²

A company that generates, transmits or distributes electricity, or supplies it to customers.

The switching element in a vacuum circuit breaker. The contacts open inside a sealed vacuum chamber, which extinguishes the arc. Testing checks that the vacuum is still intact.

Related: Vacuum Interrupter Testing

Technology that lets an EV battery export power back to the network as well as charge from it.

Testing cables with a high-voltage supply at a very low frequency, typically 0.1 Hz. This cuts the power needed to energise long cables, allowing offline PD and Tan Delta tests from a standard supply.

Related: Offline Cable Testing

EA Technology's brand for LV network monitoring, modelling and connections products.

Related: LV Network Monitoring

Online self-serve connection tool showing network operators and customers the impact of new connections.

Related: VisNet Connect

LV network design software.

Related: VisNet Design

Software for forecasting future demand and generation on the LV network.

Related: VisNet Forecast

LV substation monitoring device that measures and processes data at the network edge and hosts apps.

Related: VisNet Hub

LV auto-reclose device that restores supply after transient faults.

Related: VisNet Reclose²

Temperature sensor accessory for LV monitoring.

Related: VisNet Temperature Sensor

Monitoring device for overhead LV networks.

Related: VisNet View

An inverter function that absorbs or supplies reactive power in response to local voltage, helping to keep voltage within limits.

Service to help networks meet voltage compliance requirements.

Related: Voltage Control and Monitoring

Keeping network voltage within its required limits using tap changers, automatic voltage control and other devices. It is getting harder as more DER connects.

Related: Voltage Control and Monitoring

Industry forum on voltage control issues.

An indicator built into switchgear that shows whether a circuit is live. Some PD instruments can take measurements through the VPIS sockets.

Related: Voltage Presence Indicating System (VPIS)

Accessory that lets UltraTEV Plus² measure PD through switchgear VPIS sockets.

Related: Voltage Presence Indicating System (VPIS)

Tree-shaped degradation that grows in polymeric cable insulation (such as XLPE) when moisture is present under electrical stress. It shortens cable life and is detected with Tan Delta testing.

Coordinating voltage control across all network levels, from HV to LV, rather than managing each level separately.

Related: Voltage Control and Monitoring

Accessory that provides a phase reference so PD readings can be plotted against the supply voltage.

Related: Wireless Phase Reference