Copy of `JWES - Elecrical glossary`

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JWES - Elecrical glossary Category: Electronics and Engineering > Elecrical Date & country: 16/12/2007, UK Words: 42

Zs
Earth fault loop impedance, at a particular point in an installation. Measured in Ohms.

Ze
Earth fault loop impedance, as measured at the origin of the installation - usually at the meter or consumer unit for domestic properties. Measured in Ohms. Explanation of Earth fault loop impedance is beyond the scope of these notes. Generally, the lower the reading the better.

TLA
Three Letter Abbreviations. Some in the computing world are even abbreviations of other abbreviations!

Single-Phase Or Three-Phase
Mains electricity is generated as three-phase, with the AC waveforms separated by 120°. Larger machines etc. take three-phase mains directly, as more electrical power can be supplied this way. The term 2-phase is not generally used - although some large houses can have a two-phase supply. Houses and small commercial premises are normally on a sing…

RCD
Residual Current Device - affords extra protection against electric shock, now mandatory in some installations, and mandatory for sockets supplying equipment likely to be used outdoors. These devices work by detecting a slight current imbalance between Live and Neutral wires, and trip the circuit breaker, if this is above the trip value - commonly …

RCBO
Residual Current Breaker with Overload protection. Combined functions of MCB and RCD in one unit. Used to protect the particular circuit and preferable to separate RCD and MCBs. Recommended for commercial installations and especially on ring circuits where there are lots of computers in use (as opposed to a single RCD for the whole building).

PSCC
Prospective Short Circuit Current. The maximum current between phase and neutral, or between phases that the supply can provide. Usually measured by a special instrument at the supply origin - usually at the meter or consumer unit for domestic properties. Measured in kA (kilo Amps or Amps x 1000). CHP is also listed on the plumbing page

PME
Protective Multiple Earthing - commonly used in this area for new buildings. Only the Live and Neutral (or to be precise the PEN conductor) conductors enter the building, and the Neutral and Earth are joined just after they enter the building. Inside the building they are separate. This gives faster blowing of fuses etc. in event of a fault - but i…

PIR
Passive Infra Red. The name of the technology commonly used for movement sensors in intruder alarms and for outdoor security lights. Works by detecting the movement of heated object in its field of 'vision'.

Phase Rotation
Related to three phase, above. This is very important and often overlooked. For example, if someone is wiring up a three phase socket, they could inadvertently swap over two of the phases and all would seem well - voltages etc. would all be OK. However, connect a three-phase motor, and it will run the wrong way if the phases are reversed. This coul…

PFC
Prospective Fault Current. The maximum current for a fault between phases, between live and neutral or between phase and earth that the supply can provide. Usually measured by a special instrument at the supply origin - usually at the meter or consumer unit for domestic properties. Measured in kA (kilo Amps or Amps x 1000).

PEN
means a conductor combining the functions of both earth and neutral.

PCB
Printed Circuit Board. Very widely used method of mounting electronic components, used in TVs, mobile phones. Not really printed anymore - usually either made on an etching and electroplating process or by stamping.

PC
Personal Computer. Can also refer (in industrial electrics) to Programmable Controller or PLC - Programmable Logic Controller.

PAT
Portable Appliance Testing. Periodic inspection and testing of portable appliances for electrical safety and maintenance. Required for commercial premises under Electricity at Work Act and recommended for domestic ones too. We also recommend ALL electrical equipment should be checked periodically, not just portable equipment.

Ohms
Unit of electrical resistance. Every electric cable, wire and PCB track has resistance, which causes heating effects when a current passes through it. So the larger the current, the larger the cable size in order that the resistance is lower, hence the heating effect is kept within acceptable limits. Cable length also plays a part too. Typical circ…

NICEIC
National Inspection Council for Electrical Installation Contracting - Independent trade association for electrical contractors. Larger electrical contracting companies are often members. Membership applies to the company not the individuals. I am not a member. I believe (as of Dec 05) that they are in the process of splitting their organisation int…

MIEE
A person who is a Full Member of IEE - not a company but individuals. I am one.

microCHP
small Combined Heat and Power (plant). This is the future of heating and electricity generation. microCHP refers to a small system for a domestic house. The system comprises a boiler for heating and hot water, combined with an electricity generator. By definition, microCHP is limited to 16A electrical output. The system can also export power back …

MCB
Miniature Circuit Breaker - Modern replacement for fuses in consumer units (fuse boxes). Has benefit of more precise tripping and can be reset. In my opinion all fuse boxes and consumer units that still have fuses should be converted to use these.

kWh
Kilo-Watt Hour. Measure of energy used - electrical in this example. Your home electricity meter measures in these units. One unit costs about 5 pence. W or kW is a measure of electrical power. 1000W = 1 kW. For example, a 100W light bulb will consume 1kWh of energy in 10 hours. W or Watts is the unit of power, which for electrical power is define…

JIB
Joint Industry Board (Joint venture between ECA (Electrical Contractors Association) and Amicus). I am registered and approved under their Electro-Technical Certification Scheme for electricians. Registration applies to individuals not the company. All people registered and approved carry a photo-ID card. This is a very good scheme and an excellent…

IEE
Institution of Electrical Engineers - Long established trade association for professional electrical / electronic engineers. Publishers of the IEE wiring regulations. I am a full member. Update - April 2006. The IEE have now merged with another body and call themselves the IET - Institution of Engineering and Technology.

HiFi
Stands for 'High Fidelity'. A term used to describe good quality sound systems. Although rather distorted (a pun!) from what it meant some years ago, it now often applies to any type of music system - some that are distinctly Low-Fi to my ears. I have always liked tinkering with HiFi and speakers.

FCU
Fused Connection Unit - commonly used in kitchens to connect fixed appliances to the ring main. Also SFCU which is an FCU with a switch - usually double pole so isolates both live and neutral to the appliance - but NOT the earth. Also commonly referred to as fused Spurs

EMC
Electro Magnetic Compatibility - A complex subject that is usually referred to in the context of ensuring equipment is not adversely affected by electrical noise eg. from welding equipment, and that equipment does not give out excessive electrical noise/ interference, in-order to prevent audible hiss or crackle through radios etc.. CE marking cover…

ECA
Electrical Contractor's Association - Independent trade association for electrical contractors. Larger electrical contracting companies are often members. Membership applies to the company not the individuals. I am not a member.

Earthing
Method of connecting most exposed metal work in a building and metal appliances to electrical Earth - nominally 0V. Windows and shelves are normally excluded but most metal pipes etc. are included. This means that in the event of a fault - eg. Live wire touching a metal case, then the earth will facilitate automatic disconnection of the mains suppl…

DC
Direct current. Does not alternate! Normally used in electronic circuits and computers etc and is often derived from ac-mains via a power supply. All batteries are DC. Cars, lorries etc. run on DC battery power, as do touring caravans and boats - some may also have ac power via a generator or external mains hook-up. A device called an inverter can …

DAB
Digital Audio Broadcasting, as in DAB digital radio.

CIS
Construction Industry Scheme. Inland Revenue scheme that applies to self-employed persons (like me) who do work in the construction industry. Identifies who the person is, by means of a photo card, and allows tax deduction at source for construction projects where the person is working for a main contractor. This scheme does not apply where the per…

CEng
A person who is a Chartered Engineer and member of the Engineering Council. I am.

Ceiling Rose
No, not a plant, but an innocent looking round thing on the ceiling above conventional lights. Complex inside as they usually act as a junction box for 11 or more conductors (wires). Can be daunting to replace - even for skilled people, especially if other electrical cables have been added in as well. Watch out for the switched live, is my tip on t…

CE
Commonly referred to as CE marking on products. Stands for Conformity Europene - a vast subject that governs standards for many products, not just electrical.

CCTV
Closed Circuit Television - commonly refers to security cameras, that record on to a tape and/or monitored by a control centre.

BSc
Batchelor of Science - University degree qualification (I have one in Electrical and Electronic Engineering), Others are BA - Batchelor of Arts, BEng - Batchelor of Engineering, or MSc etc. where the M is for Master. Electrical Trade Associations etc

BEAB
British Electrotechnical Approvals Board. Approval body for approving electrical appliances for use in the UK.

BS
British Standard

BABT
British Approvals Board for Telecommunications. Approval mark for telephones etc. for use in the UK.

BASEC
British Approvals Services for Cables.

Architrave Switch
Small thin light switch that is often fitted onto Architrave - which is?... The curvy frame or moulding found around a door frame, that traditionally covers the joint between the wall-plaster and the door frame itself.

AC
Alternating current. The type of electricity normally used in houses. Called alternating because is has a cyclical current waveform that alternates as the generator in the power station rotates, at 50 times per second. NOTE: When we refer to 240V ac mains voltage in the UK, this is not the peak value. The peak voltage in the cycle is 340V - the 240…