Re: [SystemSafety] Hazard and Qualitative-Risk Analysis of Mode 3 Charging of Electric Road Vehicles

From: Peter Bernard Ladkin < >
Date: Tue, 22 Oct 2013 11:32:53 +0200


On 10/21/13 5:07 PM, Andrew Rae wrote:
> The only comment I can make until the document is in English is to applaud you and the committee for
> opening it to public peer review.

Thank you!

My personal wish is that such an analysis be public, and be improved and filled out as experience is gained. Because lots of people have an interest in ensuring that such processes are as safe as can be.

The house stuff worries me. Some people have been explaining the state of electrical installations in buildings in Germany. It is not much different from other countries and, we may presume, better than most. There is no requirement to modify installations in private households, although when professional electricians are called in, they upgrade the circuits with which they deal to current standards, and advise on the rest if necessary.

The different standards throughout Europe along are .... interesting. Almost everyone has protection against excessive current and short-circuits (these are two different kinds of protective device, even though a short-circuit mostly results in excessive current). But requirements for residual current devices vary. The British, and I think the French, require only Type AC, which protects against a sinusoidal wave form, but not against modified sinusoidal wave forms (say, those where half the cycle is chopped to null). Those are protected with Type A devices (a Siemens specification) which is since 2007 the law in Germany (my house protection was modified in 2006, but has them in - it has been state of the art for a while. The protectors are combined excess/short-circuit/Type A RCD devices to an Eaton design). Type A protection, though, may be blinded by DC currents of 6mA or over. There is quite a lot of discussion about that in standardisation committees at the moment, because electric vehicles have DC circuits in them and the question is where the protection should occur. Type B RCDs protect against all RC, but Type A combined protectors cost about 30 and Type B well over 100. Not much difference, one might think, but in practice it means that people and companies don't install Type B protection if they can avoid it.

What we are really concerned about is people putting in their own recharging boxes. These things deliver a lot of juice over many hours, potentially daily. The boxes themselves *should* be installed by a professional electrician who has the responsibility to ensure the circuit at the back of it is fit for purpose. But when heshe comes into the building and says "oh, my, you need this-and-this-and-this in the way of a circuit behind your box and it'll cost " then some building owners may well think "gee, I'll just put it in myself and avoid all that". That's folks.

15 or 16 people die in Germany every year from electric shock from building circuits. About 600 people die in building fires, of which fully one-third derive from electrical faults. So roughly speaking ten to thirteen times as many people die from electrically-caused fires as directly from electric shock. Nevertheless, in our analysis we rate shock as a more severe outcome than fire, because shock is instant and one has a chance theoretically to take some action in case of fire.

None of that gets into the HazAn, but it is stuff we think about in Committee a lot. Indeed, there is one project in my uni group (a Master's thesis) trying to assess reliably the state of installations in a small town near Bielefeld, and we have a project application in to try to do it for Bielefeld. We shall have to work with social scientists who know how to do this kind of thing.

> I don't know the direction of cause and effect but the difference in quality between open and closed
> risk assessments in my collection is marked. This doesn't stop a prevailing culture of secrecy.

When risks are assessed by a company for a product, or a systems integrator, then that entity is responsible in a legal sense for that analysis. If that analysis is open and if/when an accident happens then the legleagles have immediate access to an analysis they can criticise. If the analysis is not available, then there are all sorts of legal processes one might have to go through to obtain it; wide-ranging US-type disclosure rules do not apply over here, as I understand it; our rules are more limited.

> I look forward to the English version, and I hope you will consider publishing the received comments
> to the extent permitted by confidentiality.

That is strictly up to the authors of the comments. We also consider publishing comments anonymously.

PBL Prof. Peter Bernard Ladkin, Faculty of Technology, University of Bielefeld, 33594 Bielefeld, Germany Tel+msg +49 (0)521 880 7319 www.rvs.uni-bielefeld.de



The System Safety Mailing List
systemsafety_at_xxxxxx Received on Tue Oct 22 2013 - 11:33:05 CEST

This archive was generated by hypermail 2.3.0 : Sun Feb 17 2019 - 20:17:06 CET