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Any system of energy supply that requires financial support from the general public, for development or deployment, must be of benefit to the majority of the general public. If not, it should not be given or seek public subsidy. In simple terms the proposed system must, IMO, past what I will...

The answer is nuclear power – for those addicted to small scale home energy production look here http://www.youtube.com/watch?v=dwRt74nzRmY :D.

Well I wouldn’t ask “What are the best conditions for pv?”. Rather I would ask what are our future energy needs and how can we best meet them. Then from the whole array of possibilities – that start with using less in the first place - I would look at the most cost effective in terms of...

PV may give hope here for the great unwashed – apparently at least one company is offering (with lots of strings attached) to supply and install the panels for ‘free’. You simply have to agree to let them have the proceeds from feeding the energy back into the supply network. The fact that...

Look at this before you play with that fuse. http://www.hse.gov.uk/pubns/guidance/a33.pdf

A fault may only be detected when someone notices some affect – this could an electric shock if the bonding is not effective, but hopefully it might just be a change in supply voltage affecting the telly :D. However, if a TN-S system becomes faulty there might be no indication. The same is...

Not always, but I am aware of the point you are making - however, you are introducing the touch current model and that would introduce even more complexity as it includes weighted body impedance models and the like. It is often used when assessing appliances, etc. The touch voltage model...

You should get a job at a certain university campus in Oxfordshire that has a close attachment to the military. I was doing some testing there a while ago and I encountered a lecturer wandering down the corridor - he said 'have you seen my student?'. Only one but he still managed to...

What I should have said is that the impedance of ‘mother earth’ is not part of the earth fault loop path model. This model is of cause a simplification to concentrate the mind on the problem in question, namely shock protection. The model has many limitations as it is generally drawn as if...

For additional information The Electricity Council documents I referred to are: Engineering Recommendation G12/1 June 1975 National Code of Practice on the Application of Protective Multiple Earthing to Low Voltage Networks Section 15(g) gave the minimum size of the earthing conductor...

The equation stands - the impedance of ‘mother earth ‘ is not part of the earth fault loop path for TN systems, and for TT systems it is conventional taken to be zero as the impedance of the earth electrodes is much higher. You will not get the link you require as the details appear to have...

Whilst I understand and agree with the separation of the concepts of ‘earthing’ and ‘bonding’ you should not take this too far. In the example I gave the only role of the bonding in protecting against the fault under consideration is to limit touch voltage. It is definitely not to maintain or...

I added a bit on the end for the OP concerning conductor sizing etc. The reasons for looking at touch voltage is that others mentioned it, and that bonding has a role in touch voltage considerations. Taken as a whole this subject can be quite complex and I am afraid that many only have a...

I despair, I really do :cry: Some basic theory for a shock received when touching a faulty appliance. In an installation with Protective “equipotential” bonding Ut = If * R2 volts If the bonding is removed Ut = If * (R2 + Se) volts Where (for simple small installations): Ut...

Have you considered the instrument! The '1000volt Megger' is probably the type designed for use on electrical installations rather than on machines. As such its capabilities will doubtless be limited to that field of use. The reason your specialist instruments cost so much is that they...

Determining if two devices will discriminate under fault conditions is complex. As Spark123 has said - a study of pre-arcing times and let-through-energy is required, and even this does not give a guaranteed result over the range of possible fault or overload conditions. You cannot use the...

Just in support of 1john's statement - here is a note from the standard Note to the scope on page 1 of BS 951: 2009 Electrical earthing - Clamps for earthing and bonding - Specification Note 1 These clamps are also suitable for electrically bonding other conductive parts, where at least...

I can't make out what he has written, but tell him to read page 135 of BS EN 60898-1 2003 + A1 2004 :D. Annex ZA is Normative meaning that it is part of the standard. Further information is available in the related standard BS EN 60947-1, and from the eiema web site. Download their...

The mcb is marked with its Icn rating - that is its Rated Short Circuit Capacity. The Ics value does not have to be on the mcb - this is its Service Short Circuit Capacity. For BS EN 60898 MCBs: Ics = Icn * (factor k) Where k is just a number given in this table. Icn...

The single figure in the square window - whoops - I mean box :D is the energy limiting class as given in Annex ZA, Tables ZA 1 & 2 of BS EN 60898-1 2003 + A1 2004. The figure could be a 1, 2 or 3 - indicating the energy limiting class. Table ZA1 deals with mcbs up to 16A and table ZA...