The wires and pipes: physical infrastructure to data

Module 2 introduced the organisations that handle energy data. The data those organisations move comes from a physical place: every transformer, every cable, every meter, and every substation generates data as a byproduct of doing its job. The biggest data gap in the GB system today sits at the lowest voltage level, exactly where the energy transition is creating the most change.

Electricity in GB follows a voltage cascade from generation to consumption. At each level, transformers step the voltage down and monitoring equipment generates specific data types. Understanding this cascade is the key to understanding where energy data comes from.

Six voltage tiers sit between the generator and your kettle. Each tier produces a different category of data, monitored by a different actor under a different rulebook.

Level 1: Generation (11-25 kV)

Power stations and large renewable installations generate electricity at 11-25 kV. Generators produce output data (MW, MWh, availability), fuel data, and emissions data. This feeds into settlement as generation metering data and into NESO's balancing mechanism as real-time availability declarations.

Level 2: Supergrid (400/275 kV)

Three transmission owners operate the supergrid: NGET (England and Wales), SPT (southern Scotland), and SHET (northern Scotland). At this level, SCADA systems sample voltage, current, power flow, and circuit breaker status every 2-10 seconds. This produces E-category data types (E1 transmission telemetry, E3 power quality, E5 fault records) that flow over air-gapped Operational Technology networks, physically separated from the internet for security.

Level 3: Grid and primary substations (132/33 kV)

Voltage is stepped down at grid supply points (132 kV) and primary substations (33 kV), operated by the six DNO groups across their 14 licence areas. D1-category data (distributionnetwork telemetry) is generated here, including transformer loading, tap changer positions, and fault indicators. This is where distribution-level SCADA begins.

Level 4: High voltage (11 kV)

The 11 kV network connects primary substations to secondary (distribution) substations. D6-category SCADA data is generated here, monitoring feeder currents and voltages. Many 11 kV circuits now have automated switching (self-healing networks) that generates event logs and switching data used for reliability analysis.

Level 5: Low voltage (400/230 V)

The LV network runs from secondary substations to consumer premises. Historically, this was a data desert - DNOs had zero visibility of conditions on the 230 V cables between secondary substations and homes. D5-category LV monitoring data is now being generated by sensors deployed under RIIO-ED2 investment plans, but coverage remains patchy. This is the LV visibility gap - the single biggest data challenge in the GB distribution system.

Level 6: Your home (230 V, smart meter)

At the consumer end, smart meters generate A-category and B-category data: A1 (half-hourly consumption), B1 (export data from solar panels), and register reads for billing. This data flows through DCC's communications network to suppliers and settlement systems. At national scale, DESNZ reported over 41 million smart and advanced meters at the end of March 2026, and Elexon expects MHHS processing to handle up to 500 billion half-hourly meter readings per year from May 2027.

The gas network is fundamentally different from the electricity network in how it generates data. Electricity is measured in watts and watt-hours with instantaneous readings. Gas is measured in volume (cubic metres) at the meter, then converted to energy (kWh) using the calorific value of the gas - which varies depending on its composition.

The National Transmission System (NTS), operated by National Gas Transmission, carries gas at approximately 70 bar pressure from coastal terminals, storage facilities, and interconnectors to offtake points. Four Gas Distribution Networks (GDNs) then distribute gas at progressively lower pressures to consumers. The data generated is different from electricity: flow rates, pressures, linepack (the amount of gas stored in the pipeline system itself, which acts as a buffer), and composition data.

The most critical gas data comes from approximately 20 gas chromatographs positioned at NTS entry points. These instruments continuously measure the exact chemical composition and calorific value (CV) of gas entering the national system. Every gas bill in Great Britain depends on these CV measurements: the volume recorded at your meter is multiplied by the applicable calorific value to determine the energy you actually consumed. A 1% error in CV measurement across the entire network would affect billions of pounds in billing.

The physical infrastructure described above was designed for one-way power flow: large power stations generate, the grid transmits, distribution networks deliver, consumers consume. The energy transition is breaking this model in three ways, and each creates a data challenge.

Electric vehicles

As of early 2025, there are approximately 473,348 battery electric vehicles (BEVs) on GB roads. Each draws 7-22 kW when charging (depending on the charger type), and clusters of EVs on the same street can push LV feeders to their thermal limits. Without LV monitoring data, DNOs cannot see where these clusters are forming until a cable or transformer fails. This is not a future problem - it is happening now in streets where multiple early adopters charge simultaneously.

Heat pumps

Approximately 51,886 heat pumps were installed in 2025, each drawing 3-12 kW of electrical power. Unlike gas boilers (which use the gas network), heat pumps add load to the electricity network. The critical concern is coincident winter demand: on cold mornings, every heat pump on a street starts drawing maximum power simultaneously, creating peak loads that the LV network was never designed to handle.

Rooftop solar

Great Britain now has over 18 GW of rooftop solar capacity. Unlike EVs and heat pumps (which add demand), solar creates reverse power flow - electricity generated on rooftops flows back into the LV network, through the secondary transformer, and potentially up into the 11 kV system. This reversal was never part of the original network design, and it can cause voltage rise issues on LV feeders. Without monitoring, DNOs discover these problems only when customers complain about appliance damage from overvoltage.

Why this is a data problem

The common thread across EVs, heat pumps, and solar is the LV visibility gap. All three technologies connect at the lowest voltage level - exactly where DNOs historically had no monitoring. Without LV data, DNOs cannot see where reinforcement is needed until something fails. They cannot plan proactively for EV clusters, cannot assess whether a feeder can accept more heat pumps, and cannot detect solar-driven voltage rise. The RIIO-ED2 price control (2023-2028) includes investment in LV monitoring, but closing the gap across millions of LV circuits will take years. This is why the LV visibility gap is the single most important infrastructure data challenge in GB energy today.

Sections 3.1 to 3.3 traced where data is created. Four telemetry sources supply almost everything a practitioner then works with, and each one points at datasets the applied stage of this course consumes. Locate these four on the network map and most GB energy data has an origin you can name.

Transmission SCADA

NESO and the three transmission owners run SCADA across the 400 kV and 275 kV supergrid, sampling voltage, flow and plant status every few seconds. The aggregated and historical views surface as system data on the NESO Data Portal, which the applied stage draws on for balancing and system-operation analysis.

Distribution monitoring

Each DNO monitors its 132 kV to 11 kV network, and increasingly the LV network, as it takes on distribution system operator (DSO) functions. This is the source behind connection heatmaps, the Embedded Capacity Register and the LV monitoring feeds that flexibility and connections work depend on.

GSP boundary metering

At each grid supply point, boundary metering records the settlement-grade volumes crossing between transmission and distribution. These half-hourly boundary reads feed Elexon settlement and the GSP Group reconciliation that later modules follow from meter to market.

Gas NTS and LDZ telemetry

On the gas side, flow, pressure and calorific value are measured across the NTS and within each Local Distribution Zone (LDZ). These feeds drive gas balancing and the CV-adjusted energy figure behind every gas bill, the settlement inputs the gas modules build on.

Read together, these four sources are why the applied stage can treat settlement, balancing and open market data as trustworthy: each dataset traces back to metering or telemetry at a known point on the network. When a figure looks wrong downstream, the fastest diagnosis is to ask which of the four produced it.