[SystemSafety] Recharging Electric Road Vehicles

[Steve Tockey]

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.


-- steve



-----Original Message-----
From: Peter Bernard Ladkin <ladkin at rvs.uni-bielefeld.de>
Date: Wednesday, October 31, 2012 9:41 AM
To: "systemsafety at techfak.uni-bielefeld.de"
<systemsafety at techfak.uni-bielefeld.de>
Subject: [SystemSafety] Recharging Electric Road Vehicles

Folks,

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-veh
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
* fixed charging column with connection to grid
* charging column/charging cable interface (plugset)
* charging cable
* charging cable/ vehicle interface
* vehicle
and to define the properties of and relations between these objects which
we consider relevant to
safety properties. We use the HazOp guideword process to extend the set of
properties to consider
and to guide us to possible hazard situations. We associated each hazard
specifically with one of
the subsystems involved in it.

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
ladkin²AT²rvs.uni-bielefeld.de.

[end excerpt]

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




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