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Last edited 17 Nov 2019
Glossary of electrical terms
Big Data is both a general term for the expected explosion in data as more interactions take place over the Internet and a more specific term in the information and communications technology (ICT) sector referring to data sets that are too large or too complex to be handled by commonly available software tools.
This is electricity storage, typically consisting of batteries, located centrally on the domestic network normally near the Consumer Unit or included with other centrally located equipment or plant, for example a photovoltaic (PV) inverter.
The term centralised inverter refers to a now outdated practice of connecting more than one PV string in parallel to an inverter. Doing this makes it difficult to optimise the performance of each string and for this reason string inverters (one inverter per string) has become common.
Clean AC (colloquialism):
Clean AC is a term referring to a pure sinusoidal waveform. Many power conversion processes typically rely on rapid switching (Pulse Width Modulation) of the electricity which can produce voltage spikes, harmonics and other irregularities. If these are not adequately catered for in the circuit design or device screening it can interfere with radio and TV transmissions or other equipment.
A closed loop system (simple or complex) is one where the output of a system is sensed and fed back, often as an error signal relative to the input stimuli, to ensure a desired set point (outcome) is achieved.
An item that consumes electricity which is primarily electronic in nature (mobile phone, computer, TV etc.) as opposed to an electrical appliance (washing machine, fridge etc.). As more traditional appliances become smart and Internet enabled they too will, in terms of their controllability and system performance, become more like modern electronic devices.
Electro-migration (in integrated circuits):
This refers to a phenomenon where the current density in a conductor gets so high that it transports the metal ions along the path of current flow and forms voids at the grain boundaries. When this happens in excess the conductor essentially breaks and the integrated circuit fails. Typically the current density in domestic wiring for example, is several hundred A/cm2 but for integrated circuits it can be as high as 1,000,000 A/cm2 for aluminium interconnects or even higher for copper.
In AC circuits a ‘real’ resistive component (found in DC and AC systems) has two other impeding mechanisms referred to as reactive or imaginary components. One is related to the changing magnetic field and self-inductance and the other to electrostatic storage and capacitance.
LTE networks – LTE (Long Term Evolution):
Machine-to-machine refers to communications between machines. As ‘things’ become smarter and Internet enabled they will communicate with each other without human intervention – it is closely aligned with the Internet-of-Things (IoT).
Network (the domestic network and the local distribution network (DNO managed)):
A domestic network refers to the cables, connectors and equipment that connect the electricity supply (the meter) to the end device or appliance (load). More recently the domestic network may also consider conversion processes as many of these are now external to the device itself. The local distribution network is that which is operated by the DNO up to and including the meter.
This typically refers to the electricity consumed by a power supply or converter when it is not providing any output. Parasitic consumption refers to when a device is on standby mode but is not actually being used, for example a TV. Other examples of hidden energy waste include leaving batteries on charge beyond when they are fully charged.
An open loop system is one where an input stimuli is given to a system that with good design should achieve a certain set point or output. It does not have any error correcting feedback from output to input compensating for system variations.
A Piconet is a very local network between for example, a mobile phone and a computer, usually wireless.
Power Usage Effectiveness (PUE):
A measure of the power used by the computing equipment in a Data Centre compared to the total Data Centre demand. A PUE of 2 means that half of the total power supplied to the Data Centre (including cooling, lighting, fans etc.) is used by the computing equipment; ideally it should be 1.
Pulse Width Modulation (PWM):
The simplest way to think of this is the time a switch is on. If a switch is on for a long time current flows for the majority of the time. If it is only on for a very short period then little flows. Generally, in electrical circuits the switch is electronic and may operate at about 500 kHz or every several microseconds.
Unit of electricity:
A Watt is a measure of power and is equivalent to one Joule per Second corresponding to the rate of consumption in a circuit where the potential difference is one Volt and a current of one Ampere flows.
This article was created by --BRE. It was taken from The future of electricity in domestic buildings, a review, by Andrew Williams, published in November 2014.
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