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over-current protective device at the origin is the main fuse. Often a BS88 fuse  

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over-current protective device at the origin is the main fuse. Often a BS88 fuse  

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Uo = nominal voltage usually 230V or 400V ac

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Uo = nominal voltage usually 230V or 400V ac

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Prospective fault current is a calculation of Uo/Ze usually taken from the earth loop impedance test and states how much current may flow in the event of a short circuit

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Prospective fault current is a calculation of Uo/Ze usually taken from the earth loop impedance test and states how much current may flow in the event of a short circuit

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The symbol U is the nominal voltage between phases. The nominal voltagebetween phases in a three- phase system is 400 volts. The symbol, U0 represents the nominal phase voltage to Earth (for TN systems). The nominal value of U0 in three-phase and single- phase systems is 230 volts.

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Reg 311.1 of BS 7671 "...design of an installation within thermal limits & admissable voltage drop...diversity may be taken into account.."
Diversity assumes that not all appliances are simultaneously energised.
Example: For a domestic dwelling, lighting = 66% of possible total demand, power & heating = 100% to first 10A then 50% of remainder, cooker = first 10A  plus 30% of remaining load (+ another 5 A if a socket is fitted into the isolator switch)
The sum total is then added and the main protective device is chosen based on this value.
Ed

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Harmonic distortion is the distortion of the signal due to these harmonics. A voltage or current that is purely sinusoidal has no harmonic distortion because it is a signal consisting of a single frequency.

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e) the answer is AC, AC stands for alternating current in case you didn't know. the second answer is 50hz

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e) the answer is AC, AC stands for alternating current in case you didn't know. the second answer is 50hz

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G) The earth fault loop impedance: Earth fault loop impedance is the path followed by fault current when a low impedance fault occurs between the phase conductor and earth, i.e. “earth fault loop”. Fault current is driven round the loop by the supply voltage.

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G) The earth fault loop impedance: Earth fault loop impedance is the path followed by fault current when a low impedance fault occurs between the phase conductor and earth, i.e. “earth fault loop”. Fault current is driven round the loop by the supply voltage.

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A Guide to Earthing SystemsSince earthing is one of the first things to consider when designing an electrical installation. Here we provide an electrician’s guide to earthing systems and the BS 7671 regulations relating to them.What type of earthing systems are there? There are five types listed in BS 7671 Wiring Regulations: 1.     TN–S 2.     TN–C–S 3.     TT 4.     TN–C 5.   

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A Guide to Earthing SystemsSince earthing is one of the first things to consider when designing an electrical installation. Here we provide an electrician’s guide to earthing systems and the BS 7671 regulations relating to them.What type of earthing systems are there? There are five types listed in BS 7671 Wiring Regulations: 1.     TN–S 2.     TN–C–S 3.     TT 4.     TN–C 5.   

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Nominal means 'named'. So a nominal voltage is the 'named' voltage. For example, the nominal voltage of the supply system in Britain is 230 V. But its actual value is allowed to vary between 216.2 V and 253.0 V.

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In an electrical installation or an electricity supply system an earthing system or grounding system connects specific parts of that installation with the Earth's conductive surface for safety and functional purposes. The point of reference is the Earth's conductive surface, or on ships, the surface of the sea. The choice of earthing system can affect the safety and electromagnetic compatibility of the installation. Regulations for earthing systems vary considerably among countries and among different parts of electrical systems, though many follow the recommendations of the International Electrotechnical Commission which are described below.This article only concerns grounding for electrical power. Examples of other earthing systems are listed below with links to articles

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In an electrical installation or an electricity supply system an earthing system or grounding system connects specific parts of that installation with the Earth's conductive surface for safety and functional purposes. The point of reference is the Earth's conductive surface, or on ships, the surface of the sea. The choice of earthing system can affect the safety and electromagnetic compatibility of the installation. Regulations for earthing systems vary considerably among countries and among different parts of electrical systems, though many follow the recommendations of the International Electrotechnical Commission which are described below.This article only concerns grounding for electrical power. Examples of other earthing systems are listed below with links to articles

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the inspector must determine all of the following page 17 points a - h