Glossary of terms and acronyms

To help you understand the terminology we use in the electricity industry, we've listed a number of commonly used phrases and acronyms.

Commonly used phrases

Embedded — any generation which is connected directly to the local distribution network, as well as combined heat and power schemes of any scale
Generator capacity — the total capacity of all generators
Interconnector — electric lines or other electrical plants based within Great Britain which convey electricity between Great Britain and another country or territory
Load — the energy demand experienced on a system
Margin — the difference between the level of demand and supply that is available to meet it
Maximum Generation Service — a facility that allows access to capacity which is outside of the generator's normal operating range in emergency circumstances for up to 2 hours
Peak — the maximum power requirement of a system at a given time, or the amount of power required to supply customers at times when need is greatest
Pumped Storage — used for converting large quantities of electrical energy to potential energy
Restricted — an estimate of the demand after any Customer Demand Management has occurred
Weekday Peak Demand — the highest electricity demand expected/observed during each week expected between Monday and Thursday
Winter Peak Demand — the highest electricity demand expected/observed during the winter

A

A	Amperes
AC	Alternating Current
ACE	Advanced Commissioning Engineer
ACER	Agency for the Cooperation of Energy Regulators
AGI	Above Ground Installation
AIS	Air Insulated Substation
ANM	Active Network Management
ASA	Ancillary Services Agreement
AVCS	Automatic Voltage Control Schemes

B

BCA	Bilateral Connection Agreement
BEGA	Bilateral Embedded Generation Agreement
BEIS	Department for Business, Energy and Industrial Strategy
BELLA	Bilateral Embedded Licence Exemptible Large Power Station Agreement
BETTA	British Electricity Transmission and Trading Arrangements
BIL	Basic Impulse Level
BM	Balancing Mechanism
BMRS	Balancing Mechanism Reporting System
BMU	Balancing Mechanism Unit
BOA	Bid Offer Acceptance
BS	Balancing Services
BSC	Balancing and Settlement Code
BSUoS	Balancing Services Use of System

C

CB	Circuit Breaker
CBA	Cost Benefit Analysis
CC	Connection Conditions
CCGT	Combined Cycle Gas Turbine
CCS	Carbon Capture Storage
CDM	Construction Design Management
CEC	Connection Entry Capacity
CEGB	Central Electricity Generation Board
CfD	Contract for Difference
CION	Connection and Infrastructure Options Note
CM	Capacity Market
CSAT	Customer Satisfaction
CSM	Cable System Monitor
CSS	Connection Site Specification
CT	Current Transformer
CTM	Circuit Thermal Monitor
CUSC	Connection and Use of System Code
CVA	Central Volume Allocation

D

D Code	Distribution Code
DAR	Delayed Auto Reclose
DC	Direct Current
DCUSA	Distribution Connection Use of System Agreement
DN	Distribution Network
DNO	Distribution Network Operator
DPD	Detailed Planning Data
DRC	Data Registration Code
DSM	Dynamic System Monitor
DSO	Distribution System Operator
DSR	Demand Side Response

E

E&R	Emergency and Restoration
EDL	Electronic Dispatch Logging
EDR	Environmental Discretionary Reward
EDT	Electronic Data Transfer
EMC	Electromagnetic Compatibility
EMR	Electricity Market Reform
EMT	Electromagnetic Transient
ENA	Energy Networks Association
ENCC	Electricity National Control Centre
ENTSO-E	European Network of Transmission System Owners for Electricity
EON	Energisation Operational Notification
ESO	Electricity System Operator
ETO	Electricity Transmission Owner
ETYS	Electricity Ten Year Statement
ETYS	Electricity Ten Year Statement
EV	Electric Vehicles

F

FACTS	Flexible alternating current transmission system
FES	Future Energy Scenarios
FFR	Firm Frequency Response
FON	Final Operational Notification
FR	Frequency Response

G

GBSQSS	Great Britain Security and Quality of Supply Standard
GC	Grid Code
GEMA	Gas and Electricity Markets Authority
GIS	Gas Insulated Substation
GNCC	Gas National Control Centre
GSP	Grid Supply Point
GW	Gigawatt
GWh	Gigawatt Hour

H

HSE	Health and Safety Executive
HV	High Voltage
HVAC	High Voltage Alternating Current
HVDC	High Voltage Direct Current
Hz	Hertz

I

IEC	International Electrotechnical Commission
IET	The Institution of Engineering and Technology
ION	Interim Operational Notification

J

JPC	Joint Planning Committee

K

kA	Kilo Amperes
kV	Kilo Voltage
kW	Kilowatt
kWh	Kilowatt Hours

L

LCPD	Large Combustion Plant Directive
LDTEC	Limited Duration Transmission Entry Capacity
LJRP	Local Joint Restoration Plan
LV	Low Voltage
LVAC	Low Voltage Alternating Current

M

MEL	Maximum Export Limit
MFR	Mandatory Frequency Response
MIL	Maximum Import Limit
MITS	Main Interconnected Transmission System
MOA	Meter Operator Agent
MSA	Mandatory Services Agreement
MSC	Mechanical Switched Capacitors
MVAr	Mega Volt Amperes Reactive
MVArh	Mega Volt Reactive Hour
MW	Megawatt
MWh	Megawatt Hour

N

NAP	Network Access Planning
NBM	Non Balancing Mechanism Unit
NDP	Network Development Policy
NETS	National Electricity Transmission System
NGET	National Grid Electricity Transmission
NGP	National Grid Property
NISM	Notification of Insufficient System Margin
NOA	Network Options Assessment
NPS	Negative Phase Sequence
NTS	National Transmission System

O

OCB	Oil Circuit Breaker
OCGT	Open Cycle Gas Turbine
OFGEM	Office of Gas and Electricity Markets
OFTO	Offshore Transmission Owner
OHL	Overhead Lines
OTS	Operational Tripping System

P

PAS	Platform for Ancillary Services
PC	Planning Conditions
PPE	Personal Protective Clothing
PPS	Positive Phase Sequence
PQM	Power Quality Monitor
PTW	Permit to Work
PV	Photovoltaic

R

RDP	Regional Development Plan
REMIT	Regulation of wholesale energy markets integrity and transparency
RES	Renewable Energy Source
RfG	Requirements for Generators
RIIO	Revenue = Incentives + Innovation + Outputs Regulatory Framework

S

SCS	Substation Control System
SF6	Sulphur Hexafluoride
SGT	Supergrid Transformer
SLD	Single Line Diagram
SO	System Operator
SOF	System Operability Framework
SPD	Standard Planning Data
SQSS	Security and Quality of Supply Standards
SRS	Site Responsibility Schedule
SSAT	Stakeholder Satisfaction
STC	System Operator Transmission Owner Code
STTEC	Short Term Transmission Entry Capacity
SVC	Static VAR compensator

T

TEC	Transmission Entry Capacity
THD	Total Harmonic Distortion
TISS	Transmission Interface Site Specification
TNCC	Transmission National Control Centre
TNUoS	Transmission Network Use of System
TO	Transmission Owner
TOCO	Transmission Owner Connection Offer
TOGA	Transmission outage and generator availability
TOV	Temporary Overvoltage
TRW	Transmission Reinforcement Works
TSO	Transmission System Operator
TWh	Terawatt hour

V

V	Voltage
VIP	Visual Improvement Provision
VT	Voltage Transformer

W

W	Watt
WVT	Wound Voltage Transformer

Z

ZPS	Zero Phase Sequence