[SystemSafety] Recharging Electric Road Vehicles

From: Peter Bernard Ladkin < >
Date: Wed, 31 Oct 2012 17:41:50 +0100


Happy Halloween!

I just wrote a blog post asking for your comments on eight memes which we have encountered in our work on risk-analysing the recharging of electric road vehicles. Because I understand that many people now read e-mails on tiny devices such as smartphones, and because the post is about 3 A4 pages long, I'll just provide the link: http://www.abnormaldistribution.org/2012/10/31/recharging-electric-road-vehicles/

Here are the first few paragraphs. As the post says, I would be very grateful for any comments, if possible with your name and affiliation for appropriate credit. I intend sharing comments with my colleagues in committee.

[begin excerpt]

Recharging Electric Road Vehicles

I chair a group of specialists (electrical engineers, safety analysts, others) mandated by the German electrical-engineering standardisation organisation DKE to undertake a risk analysis of the process of recharging electric road vehicles.

We have been working now for close on one and a half years, on conductive charging, and have a document under internal review purporting to offer a high-level risk analysis of recharging using so-called “Mode 3”, in which a charging station permanently attached to the ground or to a structure is used. This mode offers charging-service providers and equipment providers the widest scope to ensure safety of the charging process, because anything considered necessary to assure an appropriate degree of safety (“safety functions” in the lingo of IEC 61508) can be built in to the box.

Other modes are Mode 2, in which a “box” with appropriate circuitry and safety mechanisms is built into the cable used for charging a vehicle, while the cable itself plugs straight in to building circuitry; and Mode 1, in which a charging cable is attached at one end to the vehicle and at the other to building circuitry, without any intermediating electrics or electronics.

The Renault Twizy car has a cable in front allowing Mode 1 charging (also Mode 3) through a normal “SchuKo” plug (“SchuKo” is short for “Schutz-Kontakt”, which means “contact-protected”, the usual kind of household plug through which current cannot flow until the person handling the plug is physically separated from live parts).

Inductive charging is somewhat further in the future.

The method we are using is a mix of OHA and HazOp. The OHA part is to consider the entire connected chain as a system, consisting of objects (subsystems)
* grid supply

We then used event trees to estimate the severity (worst-possible outcome) of each hazard. We were concerned with outcomes “electric shock” (to a person) and “fire”. We consider electric shock to a person to be at worst immediately deadly, and fire less so because a person has a certain possibility in general to extricate himherself from a fire situation. We evaluated each hazard as to whether it was unforeseeable, theoretically possible, or plausible.

There are a number of memes concerning this task which I think would like to introduce into discussion amongst safety specialists. I would like to ask for any of your thoughts on the following memes. I would like to share some thoughts transparently with colleagues, and wish to give appropriate credit for contributions, so I would be grateful if you would indicate whether your name, with or without your affiliation, may be associated with your view or whether you wish your comment to be anonymous. My email address is ladkin”AT”rvs.uni-bielefeld.de.

[end excerpt]


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

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