Glossary of Terms
Terra Energy Solutions
This glossary explains the technical terms you may encounter in our proposals, installation documents, and handover packs. It is intended to provide clarity and avoid misunderstandings. These definitions do not replace BS 7671, MCS standards, manufacturer instructions, or statutory regulations.
A
AC (Alternating Current)
Electrical current that regularly reverses direction. UK mains supply (230V) uses AC.
Access Equipment
Scaffolding, ladders, or MEWPs used to safely access work areas.
Ampere (A)
Unit of electrical current, used to define cable ratings and equipment load.
B
Battery Storage System
Equipment that stores energy for later use, commonly paired with solar PV.
BS 7671 (IET Wiring Regulations)
UK standard governing electrical installation design and testing.
C
Cable Route
The physical pathway cables follow through a property.
Circuit
A complete path for current flow including cables, accessories, and protective devices.
Circuit Breaker (MCB)
Protects a circuit by disconnecting it when overloaded or short-circuited.
Commissioning
Testing and verification that an installation functions safely and correctly.
Consumer Unit
Also called a fuse board or distribution board. Contains protective devices.
CT Clamp (Current Transformer Clamp)
A sensor that measures electrical current for monitoring or export limiting.
D
DC (Direct Current)
Electricity flowing in one direction. Used in solar panels and batteries.
DNO (Distribution Network Operator)
Company responsible for the local electricity grid and for approving solar/battery connections.
Design Capacity
Intended output, storage size, or operational limit of a system.
E
Earthing / Grounding
Directing fault current safely into the earth to reduce risk of shock or fire.
EIC / EICR
EIC: Electrical Installation Certificate
EICR: Electrical Installation Condition Report
Confirm the safety and compliance of installations.
EV Charger (Electric Vehicle Charge Point)
Device used to charge electric vehicles.
F
Feed (Electrical Feed)
A supply cable running from point A to point B for the purpose of carrying electrical power, typically supplying distribution boards, sub-mains, or other downstream circuits.
Final Circuit
A circuit supplying end-use equipment such as sockets, EV chargers, or lighting.
Fuse
A protective device that melts under fault conditions to disconnect a circuit.
G
Generation Meter
Records the electricity generated by a solar PV system.
Grid Connection
Where the property connects to the public electricity network.
G98
A UK engineering standard governing the connection of small-scale generation equipment (typically ≤16A per phase) to the electricity distribution network.
Covers systems such as small inverters, micro-PV setups and certain battery systems.
Usually allows simplified, “fit-and-notify” approval.
G99
A UK engineering standard governing the connection of larger-scale generation equipment (>16A per phase) to the electricity network.
Applies to most domestic and commercial solar PV and battery systems above the G98 threshold.
Requires DNO approval before installation, and may involve export limits, witness testing, or network studies.
G100
A UK engineering standard that governs export limitation schemes for generation equipment connected to the electricity network.
Used when a solar PV or battery system could export more power than the Distribution Network Operator (DNO) allows.
Specifies the requirements for compliant export-limiting controllers, monitoring, failsafe behaviour, and how systems must respond if communication or control signals fail.
I
Import / Export
Import: Electricity drawn from the grid
Export: Electricity sent back to the grid
Inverter
Converts DC from solar/battery systems into usable AC electricity.
Isolation / Isolator Switch
Device that safely disconnects equipment or circuits.
K
kW (kilowatt)
Unit of power. Indicates instantaneous electrical load or output.
kWh (kilowatt-hour)
Unit of energy. Used for consumption, generation or storage measurement.
L
Load
Any device that consumes electricity.
Low-Voltage (LV) System
Electrical systems operating up to 1000V AC.
M
MCB (Miniature Circuit Breaker)
Protective device for overload and short-circuit protection.
MCS (Microgeneration Certification Scheme)
UK certification for renewable installations.
Making Good
Restoring affected areas to a functional condition. Does not include decorative finishing unless specifically agreed.
Meter Tails
Cables that connect the electricity meter to the consumer unit.
N
Neutral
Conductor providing the return path for AC circuits.
Nominal Voltage
Standard operating voltage of a system (e.g., 230V AC in the UK).
P
Phases (Single-Phase / Three-Phase)
Types of power supply:
Single-phase: Common in homes
Three-phase: Used for high-power loads or commercial properties
Protective Device
Any device that disconnects a circuit under fault conditions (MCB, RCD, RCBO, fuse).
PV (Photovoltaic)
Technology that converts light into electricity using solar panels.
R
RCD (Residual Current Device)
Disconnects circuits in the event of earth leakage to protect against shock.
RCBO
Device combining MCB and RCD functions.
Roof Anchors / Fixings
Hardware used to secure solar mounting systems to roofs.
S
Scaffolding
Temporary structure enabling safe work at height.
Shading
Obstructions such as trees, chimneys or buildings that reduce solar yield.
SPD (Surge Protection Device)
Protects equipment from transient voltage spikes.
String (Solar String)
Solar panels wired in series to form a DC array.
Supply Capacity
Maximum current the property’s supply can deliver, set by the DNO.
T
Testing & Inspection
Process required by BS 7671 to verify electrical safety.
Three-Phase Supply
400V system used for larger electrical loads.
TN-C-S / TN-S / TT
Different earthing arrangements used in UK properties.
U
UPS (Uninterruptible Power Supply)
Backup device that provides temporary power during an outage.
V
Volt (V)
Unit of electrical potential.
Voltage Drop
Reduction in voltage along a cable run due to resistance.
W
Watt (W)
Unit of electrical power.
Weatherproofing
Design elements protecting equipment exposed to outdoor conditions.
Z
Ze / Zs (Earth Fault Loop Impedance)
Values that verify the effectiveness of protective devices and the earthing system.