Archive for the ‘islanding’ Category

TECHNICAL – Glossary & terms used for electrical supplies

Wednesday, May 20th, 2009

GLOSSARY
active power – the multiple of the components of alternating current and voltage that equate to true power. Normally measured in kilowatts (kW) or megawatts (MW).
adoption agreement – an agreement between a developer and a DNO, concerning the transfer into DNO ownership of infrastructure supplied and installed by a third party.
approved contractor – a contractor which has been approved by the DNO for carrying out third party connection work.
Balancing and Settlement Code (BSC) – the code which determines the rules governing the Balancing Mechanism and the settlement process for electricity trading in England and Wales as from time to time amended.
capacity factor – a factor, generally applied to renewable energy schemes, which relates the maximum continuous power output of the generator to the expected long run average power output.
committed network – future network configuration for which financial approval has been given.
condition 4 statement – document published by a DNO outlining the basis of charges for connection to the DNO’s distribution system.
connection agreement – an agreement setting out terms relating to a connection with the DNO Distribution System (excluding any bilateral agreement with the transmission licensee).
Connection and Use of System Code (CUSC) – contractual framework for connection to and use of the NGT transmission system.
connection voltage – voltage level at which a site is connected to the transmission or distribution system.
contestable – that part of the connection works which is open to competition.
CDM Regulations – the Construction (Design and Management) Regulations 1994.
Regulations specifying the duties of designers to minimise health and safety hazards involved in the construction of buildings and other installations.
CD&M Regulations – see CDM Regulations.
Declared Net Capacity (DNC) – declared net capacity: the maximum power available for export on a continuous basis minus any power imported by the station from the network to run its own plant.
determination (of disputes) – any dispute arising under certain sections of the Electricity Act 1989 between a DNO and a person requiring a supply of electricity, can be referred to Ofgem for determination. These determinations are then published as a matter of public record, and then form ‘case law’ on the subject.
distributed generator – a generator which is connected to a DNO’s distribution network rather than to the transmission grid. Distributed generation is generally a lot smaller than plant connected to the transmission grid as the maximum operating voltage of the distribution network is 132kV (and 33kV in Scotland).
Distribution Network Operator (DNO) – a holder of a Distribution Licence.
electronic inverter system – an electronic device placed between a generator and the network it is connected to for the conversion of power at one frequency to another (including dc/ac). The output voltage and frequency may be determined by the control equipment associated with the inverter or by the voltage and frequency of the
network it is connected to.
embedded generator – now generally termed distributed generator (see above), although this term is still used in the Distribution Code of Great Britain and the Grid Codes.
extension – It is sometimes necessary to extend the DNO’s distribution network in order to provide a connection for a new user or generator of electricity. Network extensions are often required for generation schemes in remote locations.
fault contribution – the contribution of an electrical source, such as a distributed generator, to the total fault levels in a distribution network.
high voltage (HV) – any voltage exceeding Low Voltage (ie exceeding 1000volts between phase conductors or exceeding 600volts between phase conductors and earth).
induction generator – a type of rotating electrical generator which operates at a speed not directly related to system frequency. The machine is generally excited by reactive power drawn from the network to which it is connected and the output voltage and frequency are determined by those of the network to which it is
connected.
islanding – islands of supply are discrete parts of a distribution system which are capable of generating and maintaining a stable supply of electricity to the customers within those discrete parts without any connections to the rest of the system.
line drop compensation – a voltage control scheme (used for the control of voltage levels in distribution networks) which compensates for the change in voltage drop in a long line as the current in the line changes.
loss of mains – the loss of an electrical connection between a section of a distribution network and the main grid supply, often due to the operation of circuit breakers.
low voltage (LV) – in relation to alternating current, a voltage exceeding 50 volts measured between phase conductors (or between phase conductors and earth), but not exceeding 1000volts measured between phase conductors (or 600volts if measured between phase conductors and earth).
Long Term Development Statement (LTDS) – (sometimes referred to as the LC25 statement). Statement prepared annually by each DNO as required by Standard Condition 25 of the Electricity Distribution Licence.
mains paralleling – the operation of an electrical generator while connected in parallel with the main grid supply.
negative reactance compounding – a voltage control scheme (used for the control of voltage levels in distribution networks) which allows the voltage–regulated system to be fed from two or more transformers in parallel.
Ofgem – the Office of Electricity & Gas Markets (under the Gas and Electricity Markets Authority, established by the Utilities Act 2000).
point of common coupling – the point in the distribution network where the lines or cables which are used solely to provide the supply to one customer (eg a generation scheme) are connected to infrastructure which is also used to provide supplies to other customers.
primary – generic term used by a DNO to indicate the source of the main 11kV or 6.6kV HV distribution network; eg primary substation – 33/11kV or 66/11kV transformation substation infeed to the 11kV network; 11kV primary busbar – source 11kV busbar for an 11kV network.
protection system – the provisions for detecting abnormal conditions in a system and initiating fault clearance or actuating signals or indications.
reactive power – the product of voltage and current and the sine of the phase angle between them which is normally measured in kilovar (kVAr) or megavar (MVAr).
reactor – wound network component generally used to limit reactive power flows and
hence fault levels.
reinforcement – Reinforcement work is usually required to increase the electrical capacity of those parts of the network which are affected by the introduction of new generation or demand. Other work might include upgrading the switchgear at a substation some distance from the proposed generation scheme, due to the increase in fault level caused by the connection of the generator.
Small Scale Embedded Generator (SSEG) – a source of electrical energy and all associated interface equipment, rated up to and including 16A per phase, single or multi phase 230/400V ac and designed to operate in parallel with a public low voltage distribution network.
Static Var Compensator (SVC) – equipment for injecting or absorbing reactive power (Vars) at the point of connection to assist in control of system voltage.
supplier – a person or company providing a supply of electricity. This could be the
local DNO, a second tier supplier or an exempt supplier.
synchronous generator – a type of rotating electrical generator which operates without slip and at a speed that is directly related to system frequency.
thermal rating – the current-carrying capacity of a cable, an overhead line or any other item of electrical infrastructure, which is determined by the heating effect arising from electrical losses.
third party connection – connection provided by a contractor other than the local DNO.
Use of System (UoS) – the use of a transmission or distribution network by a generator, a supplier, a customer or an interconnected party for the purposes of transporting electricity.