The vocabulary of the Power layer.

The high-voltage part of the grid that carries bulk power from generators to load centres, at 132 kV and above in most Australian networks and at comparable voltages elsewhere. Transmission lines are few, long and heavily loaded, and connecting to one gives access to the largest blocks of capacity. In the National Electricity Market each region's transmission assets belong to a transmission network service provider, and a load of data centre scale usually connects here.

See also Distribution network, Point of connection, Network capacity

The medium and low-voltage part of the grid between transmission substations and end users, at up to 66 kV in most Australian networks and below about 100 kV elsewhere. It holds little spare capacity at any one point; a facility of a few tens of megawatts may connect here, but above that reinforcement usually costs more than a transmission connection. Owners are distribution network service providers in Australia and utilities or distribution system operators elsewhere.

See also Transmission network, Hosting capacity, Network augmentation

The physical and contractual boundary where the facility's installation meets the network, usually a set of terminals in a substation or on an incoming line. Ownership, maintenance, metering and the performance standards the connecting party must meet are all defined here. In Outpace's value chain it is also the boundary between the Power layer and the Data Centre layer: upstream is access and supply, downstream is the facility.

See also Connection offer and agreement, Metering and settlement, Substation

The formal process by which a prospective load asks a network owner for a connection and learns what it takes. In the National Electricity Market the sequence is enquiry, application, offer and agreement under Chapter 5 of the National Electricity Rules, with system studies between steps; other grids have equivalents such as the interconnection request. Here a site's claimed capacity first meets the network's real condition; most sites marketed as having power have not passed this stage.

See also Connection offer and agreement, Interconnection queue, Network capacity

The contract between the connecting party and the network owner that sets the capacity, voltage, performance standards, charges and timing of a connection. An offer precedes it and may be conditional on augmentation works, further studies or payments. A signed agreement with a defined capacity and energisation date is the only document that turns a claim of available power into a right; letters of intent, enquiry responses and capacity maps do not.

See also Connection enquiry and application, Performance standards, Energisation

The ordered list of projects waiting for a network owner or system operator to study and approve their connection. Each connection changes the flows and fault levels later ones are studied against, so studies run in sequence. In several large markets the generation queue now outlasts the construction time of the plant behind it, and large loads have joined the same bottleneck. Queue position is an asset, and in some jurisdictions a transferable one.

See also Connection enquiry and application, Network capacity, Network augmentation

The additional load a point on the network can supply without breaching thermal, voltage or stability limits under the operator's planning criteria. It depends on the lines, transformers and generation behind the point and on what other users already draw. Capacity is quoted for a point and a time rather than for a parcel of land; a figure without a point of connection and a planning case attached is a marketing number.

See also Hosting capacity, Firm and non-firm access, Network augmentation

A firm connection has its full capacity available under normal and credible contingency conditions; a non-firm one may be reduced when the network is constrained. Non-firm or flexible connections come sooner and cheaper because the network is not reinforced for the worst hour. The questions for an AI facility are how many hours a year the reduction bites and whether the workload tolerates them. Calling a non-firm connection firm is the most common misstatement in site marketing.

See also Curtailment, Network capacity, Demand response

A reduction in the power a connected party may inject or draw, instructed by the network owner or system operator to keep the network within limits. For generators it means spilling energy; for loads, reducing demand on instruction. Curtailment terms sit in the connection agreement and any flexible connection arrangement, and the expected hours and megawatts of curtailment are an input to the facility's revenue model.

See also Firm and non-firm access, Load shedding, Demand response

The generation or load a section of the distribution network can accept without upgrades, as published by the network owner in capacity maps and planning reports. These figures are screening tools: they reflect a standard planning case, are updated infrequently and rarely count applications already in progress, so they can overstate what remains available. They are useful for ruling sites out and poor evidence for ruling them in.

See also Network capacity, Connection enquiry and application, Distribution network

Works that increase the existing network's capacity to accommodate a new connection: a new transformer, a reconductored line, an additional substation bay or a second circuit. Who pays depends on the regulatory regime; in Australia the connecting party typically funds augmentation that serves only it, while shared network upgrades pass through the regulated planning process and asset base. Its lead time, set by transformer and switchgear supply, is usually the critical path of a large connection.

See also Contestable works, Transformer lead time, Connection offer and agreement

Connection works the connecting party may procure from a competing contractor rather than from the incumbent network owner. In the National Electricity Market dedicated connection assets such as a new substation or spur line are generally contestable while shared network works are not; the split differs by state and again in other countries. Contestability gives the connecting party control of price and programme for assets it will own, instead of waiting on the incumbent's workload.

See also Network augmentation, Connection assets, Substation

The ability of the network at a point to hold a stable voltage waveform through a disturbance, measured by the fault current available there. Strength comes mainly from synchronous machines, so a network with many inverters and few spinning machines is weak. Weak networks impose tighter performance requirements on new connections and may need synchronous condensers or grid-forming equipment; in the National Electricity Market a party whose equipment reduces system strength can be charged for the remedy.

See also Inertia, Fault level, Grid-forming inverter

The resistance of the power system to changes in frequency, supplied by the rotating mass of synchronous generators and motors. When supply and demand diverge, inertia slows the frequency change and gives control systems time to act. As coal and gas units retire, operators procure inertia directly or substitute fast frequency response from batteries; a facility load or battery that responds within a fraction of a second holds something the operator values.

See also Frequency and voltage, System strength, Grid-forming inverter

The two quantities a power system is operated to hold within bands: frequency, 50 Hz in Australia and most of the world and 60 Hz in North America and parts of Asia, and voltage at each node within a percentage of nominal. Frequency reflects the supply and demand balance across the whole system; voltage is local and follows reactive power flows. The connection agreement sets what the facility must ride through and must not cause.

See also Inertia, Reactive power, Ancillary services

Services the system operator buys to keep frequency, voltage and system security within limits, separately from energy. In the National Electricity Market the main ones are frequency control ancillary services, procured in raise and lower markets from very fast to slow; other systems speak of frequency response, operating reserve and regulation. Large loads with controllable demand or batteries can be paid to provide them, offsetting part of the resilience they would build anyway.

See also Frequency and voltage, Demand response, Battery energy storage system

The technical requirements a connecting party agrees to meet at the point of connection: voltage and frequency ride-through, reactive capability, harmonic limits, protection settings and behaviour during disturbances. In the National Electricity Market they are negotiated between automatic and minimum access standards and written into the connection agreement; other grids use a grid code. A large AI load built on fast-switching power electronics is studied against them much as a generator is, and that takes months.

See also Connection offer and agreement, Power quality, Harmonics

The relays, circuit breakers and communications that detect a network fault and disconnect the smallest possible section within a fraction of a second. A fault on one feeder should not take down the substation, and a fault at the facility should not take down the network. The connection agreement requires the facility's protection to coordinate with the network's, and the grading studies that prove it are part of the connection process.

See also Protection relay, Switchgear, Fault level

The planning criterion that a network must keep supplying its load after losing any single element: one line, transformer or generator. A connection meeting N-1 has at least two independent paths, each able to carry the full load. Most transmission networks are planned to N-1 and some critical sections to N-2. A single-circuit spur offers no such redundancy, leaving the facility's own dual feeds, storage and generation to carry the burden.

See also Dual feeds, Firm and non-firm access, Network protection

The capability to restore a power system from complete shutdown, using generators that start without external supply and energise the network in stages. System operators contract black start services from specific plants in each region. For a facility the question is where it sits in the restoration sequence: large loads are reconnected late, so on-site generation and storage sized for a short outage may face a long one after a system-wide event.

See also Load shedding, Behind-the-meter and front-of-meter, Inertia

The deliberate disconnection of load, by automatic relays or the system operator, to prevent collapse when supply falls short. Under-frequency load shedding acts within fractions of a second in predefined blocks; manual shedding follows when reserves are exhausted. Large industrial loads are often in the early blocks because one feeder removes a lot of demand. The connection agreement sets which schemes a facility is in, and exclusion is usually bought with controllable demand.

See also Curtailment, Demand response, Frequency and voltage

Where a generator or battery sits relative to the facility's revenue meter. Behind-the-meter assets supply the facility directly; front-of-meter assets sell into the network and the facility buys by contract. Behind-the-meter supply avoids network charges on displaced energy and can ride through a grid outage, but the facility carries the plant's availability, fuel and emissions obligations. As connection timetables lengthen, on-site plant is increasingly proposed as primary supply, turning a few hours a year of standby into continuous duty.

See also Co-location with generation, Gas peaking plant, Network charges

An inverter that sets its own voltage and frequency reference and can therefore hold a network up alone. A grid-following inverter, the conventional kind, synchronises to an existing voltage and stops when it is lost. Grid-forming batteries supply synthetic inertia and fault current and are replacing the services of retiring synchronous plant. A grid-forming facility battery can hold the site up when the network is lost and be contracted for system strength services.

See also System strength, Inertia, Battery energy storage system

The installation where voltage is changed and circuits are switched, protected and metered: transformers, switchgear, busbars, protection and control equipment in a secured compound or building. A large facility usually has a dedicated connection substation stepping transmission or sub-transmission voltage down to the site's distribution voltage. The connection agreement sets whether the connecting party or the network owner builds and owns it, which changes programme, cost and who is called when it fails.

See also Power transformer, Switchgear, Connection assets

The lines, cables and substation equipment built solely to connect one facility to the shared network. Overhead lines are cheaper and faster per kilometre and more exposed to weather and fire; underground cables cost far more, take longer to repair and are often required near urban land. They are usually paid for by the connecting party, may be contestable, and stay on the facility's side of the boundary even when the network owner operates them.

See also Contestable works, Substation, Point of connection

The machine that transfers power between two voltage levels through magnetic coupling, with no moving parts beyond its cooling and tap changer. At a facility connection, transformers step the network voltage down in one or two stages to the medium voltage distributed around the site. They are large, custom-built, oil-filled and slow to replace, so the number and rating of transformers, and the spare held on site, is a first-order availability decision.

See also Transformer rating and ratio, Transformer lead time, Substation

A transformer is rated by apparent power in megavolt-amperes, voltage ratio, such as 132 kV to 33 kV, and cooling stages, each allowing a higher rating as fans and pumps are added. The MVA figure applies at rated temperature rise; the real power a facility can draw through it is that figure times the power factor. An on-load tap changer adjusts the ratio in small steps to hold secondary voltage steady.

See also Power transformer, Power factor, High, medium and low voltage

The circuit breakers, disconnectors, earthing switches, busbars and instrument transformers that connect, isolate and protect circuits at a given voltage. High-voltage switchgear is air-insulated in an outdoor yard or gas-insulated in a compact enclosure; medium-voltage switchgear sits in rows of metal-clad panels. Rated current and fault-breaking capacity must exceed the network's fault level at the point, and the busbar arrangement decides whether a failed section can be isolated while the rest stays live.

See also Fault level, Protection relay, Radial and ring feeds

The conventional bands for electrical plant: low voltage up to 1 kV, medium voltage from 1 kV to about 35 kV in IEC usage and higher in North America, and high voltage above that, with extra-high voltage for the largest transmission lines. Equipment, clearances, safety rules and qualifications change at each boundary. A facility connects at high voltage, distributes at medium and uses equipment at low; each transformation loses energy and adds a failure point.

See also Transformer rating and ratio, Switchgear, Transmission network

The current that would flow at a point if a short circuit occurred there, set by network strength and the transformer impedance between source and fault. It sets the switchgear's fault-breaking capacity and the mechanical forces equipment must bear. A high fault level means a strong network and dearer switchgear; a low one a weak network where voltage dips and power quality are harder to manage. Fault level studies are part of every connection application.

See also System strength, Switchgear, Protection relay

Two ways of arranging the circuits that supply a site. A radial feed runs from source to load along one path, so any fault interrupts supply until repaired. A ring runs from the source through several points and back, so a faulted section can be isolated and loads beyond it fed from the other side. Rings cost more in cable and switchgear and allow any section to be maintained or lost without an outage.

See also Dual feeds, Switchgear, N-1

Two independent supplies to a site from separate network circuits, ideally from separate substations by separate routes, each able to carry the full load. Dual feeds are the first requirement for high availability at the grid level, and independence is the point: two circuits on the same towers or the same transformer fail together. The connection agreement and planning standard decide whether both feeds are firm and how fast supply transfers between them.

See also Radial and ring feeds, N-1, Firm and non-firm access

The device that measures current, voltage and frequency on a circuit, compares them against its settings and trips a circuit breaker when they indicate a fault. Modern relays are digital, record every event and communicate to decide which breaker opens first. Settings are graded so the breaker nearest the fault trips before those upstream, and the grading study proving this against the network owner's protection is a connection requirement.

See also Network protection, Switchgear, Fault level

How closely the voltage supplied to and current drawn by a facility stay to an ideal sine wave at nominal magnitude and frequency, measured as harmonics, flicker, unbalance, sags and swells. Network standards limit what the network must deliver and what a load may cause. AI facilities run on power electronics, so they are both sensitive to poor quality and capable of causing it, and connection studies test the second as closely as the first.

See also Harmonics, Reactive power, Performance standards

Distortion of the voltage or current waveform by components at multiples of the fundamental frequency, produced by rectifiers, inverters, variable-speed drives and switch-mode power supplies. Harmonic currents heat transformers and cables beyond their fundamental loading, interfere with protection and can pass back into the network. Connection agreements cap the harmonic emission a facility may inject, and filters or active front ends on its equipment are how the cap is met.

See also Power quality, Power factor, Performance standards

The component of alternating-current power that oscillates between source and load without doing work, measured in megavolt-amperes reactive and needed to magnetise transformers and motors and hold voltage up along lines. It travels poorly, so it is supplied locally by capacitors, synchronous condensers, static compensators or battery inverters. The connection agreement sets the reactive range a facility must absorb or supply at its connection point, sizing equipment it would not otherwise buy.

See also Power factor, Frequency and voltage, Transformer rating and ratio

The ratio of real power, in megawatts, to apparent power, in megavolt-amperes, at a point in the system. A power factor of one means all the current does useful work; lower values mean conductors and transformers carry current that delivers no energy. Network tariffs penalise poor power factor through demand charges levied in megavolt-amperes, and it consumes transformer capacity, so correction equipment pays for itself quickly in a large facility.

See also Reactive power, Transformer rating and ratio, Demand charge

The time between ordering a large power transformer and receiving it, for transmission-class units now measured in years in most markets. The constraint is a small number of manufacturers, specialised steel and copper supply, and demand from grid replacement programmes and renewables as well as data centres. The order is therefore placed before the connection agreement is final and the facility design frozen, a capital commitment made on incomplete information.

See also Long-lead items, Power transformer, Network augmentation

Equipment whose delivery time exceeds the time between ordering it on firm information and needing it on site: large transformers, high-voltage switchgear, gas turbines, large generators and some cable. Long-lead items set the critical path of a facility programme and are ordered early, often by the sponsor at its own risk, to protect the energisation date. Holding or trading manufacturing slots for this equipment is a real competitive position today.

See also Transformer lead time, Energisation, Switchgear

The moment the network owner first applies voltage to the facility's connection assets, after the works are complete and inspected and the agreement's conditions precedent are met. It is distinct from commercial operation: equipment is energised in stages, tested under load and released for service afterwards. The energisation date is the figure the revenue model depends on, controlled by the network owner's programme, any augmentation and the long-lead items.

See also Grid-side commissioning, Connection offer and agreement, Long-lead items

The staged tests that prove the connection and the facility's electrical plant behave as the agreement requires: protection trips, phasing checks, transformer energisation, load steps, reactive capability and harmonic and flicker measurements. In the National Electricity Market the sequence includes hold points the market operator must release and measured data to validate the connection study models. This grid-side programme runs alongside, and sometimes gates, the Data Centre layer's commissioning of the power train inside.

See also Energisation, Performance standards, Metering and settlement

Revenue metering records the energy passing the point of connection each settlement interval, to an accuracy class set by market rules; settlement turns the readings into what the facility pays for energy, network use and market fees. In the National Electricity Market the interval is five minutes and an accredited metering provider, rather than the network owner, supplies the meter. This data underpins every energy cost, carbon and provenance claim the facility makes.

See also Point of connection, Spot and contract markets, Energy provenance evidence