Canadian Yachting February 2018 - 45

El e ctri c S h o c k Dr o w ni n g ( E S D)
J o h n G ulli c k, A P
M a n a g er of G o v er n m e nt a n d S p e ci al Pr o gr a ms

W h at d o e s " mi n ut e " m e a n ?
I n 2 0 0 8 t h e U. S. C o ast G u ar d c o n d u ct e d a st u d y t h at i n di c at e d t h e f oll o wi n g:
C urr e nt l ev el

P ossi bl e eff ects o n t h e h u m a n b o dy

1 mA

Perce pti o n level. Sli g ht ti n gli n g se ns ati o n b ut still d a n ger o us
u n der cert ai n c o n diti o ns.

5 mA

Sli g ht s h ock felt, n ot p ai nf ul b ut dist ur bi n g. Str o n g i nv ol u n t ary re acti o ns m ay le a d t o i nj ury.

6 - 16 m A

Pai nf ul s h oc k. B e gi n t o l os e m usc ul ar c o ntr ol.

17 - 99 m A

Extr e m e p ai n, r es pir at ory arr est, s ev er e m usc ul ar c o ntr ac ti o ns. A n i n divi d u al c a n n ot l et g o of a n el ectri ﬁ e d o bj ect.
D e at h a p ossi bility.

100 - 2000
mA

Ve ntric ul ar ﬁ brill ati o n, m usc ul ar c o ntr acti o n, n erv e d a m a g e
a n d d e at h is li kely.

2000 + m A

C ar di ac arr est, i nt er n al or g a n d a m a g e a n d s ev er e b ur ns.
D e at h is pr o b a bl e.

W h y f r e s h w at e r a n d n ot s alt ?
S alt w at er is a n y w h er e fr o m 5 0 t o 1 0 0 0 ti m es m or e c o n d u c ti v e t h a n fr es h w at er. T h e c o n d u cti vit y of a h u m a n b o d y w h e n
w et li es b et w e e n t h e t w o b ut is m u c h cl os er t o s alt w at er t h a n
fr es h. T h e h u m a n b o d y o nl y sl o ws el e ctri cit y d o w n s o m ost
of t h e el e ctri c al c urr e nt will g o ar o u n d o n its w a y t o a gr o u n d.
W h y Alt e r n ati n g C u r r e nt ( A C) a n d n ot Di r e ct C u r r e nt ( D C) ?
T h e c y cli n g n at ur e of A C disr u pts t h e ti n y el e ctri c al si g n als
us e d b y o ur n er v es a n d m us cl es f ar m or e t h a n t h e str ai g ht
ﬂ o w of D C.
H o w d o e s el e ct ri cit y g et i nt o t h e w at e r i n t h e ﬁ r st pl a c e ?
I n a pr o p erl y f u n cti o ni n g el e ctri c al s yst e m all of t h e 1 2 0 v olt
A C c urr e nt t h at g o es i nt o a b o at t hr o u g h its s h or e p o w er

F or str ay A C t o g et i nt o t h e w at er, t h er e m ust b e a n el ectric al f a ult a n d a f a ult
i n t h e s af ety gr o u n d. C o urt esy D avi d Rif ki n.

c or d r et ur ns t o t h e s o ur c e - t h e tr a nsf or m er as h or e or o n
t h e d o c k w h er e it ori gi n at e d. F or a n y of t h at c urr e nt t o wi n d
u p i n t h e w at er t h e f oll o wi n g t hr e e t hi n gs h a v e t o o c c ur.
1. El e ct ri c al f a ult: S o m e w h er e c urr e nt m ust b e es c a pi n g
fr o m t h e s yst e m tr yi n g t o ﬁ n d a n ot h er p at h b a c k t o its
s o ur c e as h or e.
2. A C S af et y G r o u n d F a ult: T h e A C gr o u n di n g s yst e m
m ust b e c o m pr o mis e d s o t h at str a y c urr e nt c a n n ot e as il y g o t o gr o u n d t hr o u g h t h e gr o u n d s af et y wir e. A n y
str a y el e ctri cit y t h e n h as o nl y o n e p at h b a c k t o its s o ur c e,
t hr o u g h t h e w at er.
3. N o Gr o u n d F a ult Pr ot e cti o n: Gr o u n d F a ult Pr ot e cti o n
( G F P) d e vi c es, li k e Gr o u n d F a ult Cir c uit I nt err u pt ers ( G FCIs) r e q uir e d i n b at hr o o ms as h or e, ar e d esi g n e d t o d et e ct
diff er e n c es m e as ur e d i n milli a m ps a n d t o s h ut d o w n t h e
el e ctri cit y wit hi n fr a cti o ns of a s e c o n d. If t h e cir c uit d o es n ot
h a v e o n e t h e el e ctri cit y will c o nti n u e t o ﬂ o w i nt o t h e w at er.
If t h es e c o n diti o ns e xist t h e n s o m e or all of a b o at's u n d erw at er m et als, li k e t h e pr o p ell er, st er n dri v e or t hr o u g h h ull
ﬁtti n gs, will b e e n er gi z e d a n d el e ctri cit y will r a di at e o ut fr o m
t h es e ﬁtti n gs i nt o t h e w at er a n d will s et u p a d a n g er o us v olta g e t h at will p ass t hr o u g h a n y s wi m m er cl os e b y.
Eli mi n ati n g C u r r e nt L e a k a g e:
I n t his arti cl e I will n ot g o i nt o t h e d et ails a b o ut ﬁ n di n g o ut if
y o ur b o at is l e a ki n g el e ctri c al c urr e nt b ut a b asi c cir c uit t est er
a n d cl a m p m et er s h o ul d d et e ct a n y pr o bl e ms. Yo ur m ari n a
s h o ul d b e t esti n g its s yst e ms o n a r e g ul ar b asis a n d y o u c a n
us e a t est m et er t o q ui c kl y d et er mi n e if t h e s h or e a n d b o at
p o w er s yst e ms ar e w or ki n g pr o p erl y. J ust b e c a us e y o ur b o at
is n ot l e a ki n g p o w er n o w d o es n ot m e a n t h at it will n ot d o s o
i n t h e f ut ur e. T h er e ar e t w o w a ys t o eli mi n at e t h e pr o bl e m:
T h e ﬁrst a n d b est is t o c o m pl et el y is ol at e t h e A C s h or e
C o nti n u e d o n p a g e 5 2

w w w. c a n a di a n y a c h ti n g. c a

45

T H E P O RT H OL E

R e c e ntl y I h a v e r e c ei v e d a c o u pl e of q u esti o ns r e g ar di n g
str a y el e ctri cit y i n t h e w at er ar o u n d fr es h w at er m ari n as.
T his str a y el e ctri c al c urr e nt c a n c a us e s wi m m ers a n yt hi n g
fr o m a mil d s h o c k t o d e at h a n d t h er e h a v e b e e n a n u m b er
of r e c or d e d d e at hs, es p e ci all y i n t h e U. S., w h er e 1 2 0 v olt
Alt er n ati n g Crr e nt ( A C) fr o m n e ar b y b o ats or d o c ks h as
el e ctr o c ut e d or i n c a p a cit at e d s wi m m ers i n fr es h w at er.
T his littl e k n o w n a n d oft e n u ni d e nti ﬁ e d pr o bl e m is c all e d
El e ctri c S h o c k Dr o w ni n g ( E S D). T h es e d e at hs a n d i nj uri es
ar e e ntir el y pr e v e nt a bl e.
I n m y r es e ar c h I f o u n d a n e x c ell e nt arti cl e o n E S D i n t h e
B o at U. S. S e a w ort h y m a g a zi n e, J ul y 2 0 1 3, writt e n b y B et h
L e o n ar d. Wit h B o at U. S.'s p er missi o n a n d t h at of B et h I will
t a k e m ost of t his i nf or m ati o n dir e ct fr o m t h at arti cl e.
E S D h a p p e ns w h e n " mi n ut e " a m o u nts of alt er n ati n g c ur r e nt ar e pr es e nt i n fr es h w at er.

J US T
AS K
JOH N
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Table of Contents for the Digital Edition of Canadian Yachting February 2018
