Re: [SystemSafety] Recharging Electric Road Vehicles

From: Steve Tockey < >
Date: Wed, 31 Oct 2012 21:26:06 +0000

Beyond just "electric shock" and "fire", isn't it also necessary to consider some scenario where for some reason the content of the battery leaks? I don't know enough about the technology inside the car batteries (is it solid/powder or is it liquid? ...), but I would think that a) it's some pretty nasty chemicals, and b) there has to be some scenario where those chemicals could get get loose as part of the charging process.

-----Original Message-----
From: Peter Bernard Ladkin <ladkin_at_xxxxxx Date: Wednesday, October 31, 2012 9:41 AM To: "systemsafety_at_xxxxxx <systemsafety_at_xxxxxx Subject: [SystemSafety] Recharging Electric Road Vehicles


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: icles/

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 ³Mode 3², 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 (³safety functions² in the lingo of IEC 61508) can be built in to the box.

Other modes are Mode 2, in which a ³box² 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
³SchuKo² plug (³SchuKo² is short for ³Schutz-Kontakt², which means ³contact-protected², 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 ³electric shock² (to a person) and ³fire². 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 ladkin²AT²

[end excerpt]


Prof. Peter Bernard Ladkin, Faculty of Technology, University of
Bielefeld, 33594 Bielefeld, Germany
Tel+msg +49 (0)521 880 7319

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Received on Wed Oct 31 2012 - 22:26:17 CET

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