What is BS7671 Amendment 1 about?

It covers regulations for electric vehicle charging installations, particularly concerning earthing methods.

What are the three types of earthing systems discussed?

The three types are TT, TN-CS, and TN-S.

Why are PME supplies problematic for EV charging?

Due to potential voltage risks if the PEN conductor is damaged, creating dangerous conditions.

Can you convert a TN-CS supply to a TT supply?

It's complicated due to various underground service factors and potential safety issues.

What are the five options to ensure safety when using PME for EV charging?

The options include using specific devices that monitor voltage and earth resistance, among other methods.

Is a TT earthing system preferable?

A TT system can be safer if properly implemented, but comes with its own set of challenges.

How can the dangers of high voltage be mitigated?

By using additional ground electrodes and ensuring low resistance connections.

What is the significance of the 70 volts regulation?

It aims to prevent dangerous voltage surges in the event of a fault.

Are there any devices that ensure safety for outdoor charging points?

Some devices monitor and disconnect in the case of voltage detection, but are not foolproof.

What is the ideal solution for EV charging installations?

A proper TT system with low resistance electrodes or three-phase monitoring devices.

Earthing systems, EV charging connection options and open PEN detection devices.

00:38:39

https://www.youtube.com/watch?v=gZVx7GbAwlg

Ringkasan

TLDRThe video focuses on the installation and safety measures surrounding electric vehicle charging according to UK’s BS7671 Amendment 1. It emphasizes the need to understand different earthing systems such as TT, TNCS, and TNS, addressing the risks associated with PME (Protective Multiple Earthing) supplies when applied to outdoor charging. The speaker provides a detailed exploration of the complex interactions between different earthing configurations and their influence on safety during EV charging, outlining the regulations and highlighting the best practices necessary to mitigate electrical hazards. Several options for maintaining safe operations in various earthing scenarios are presented, although most involve considerable compromises or impractical solutions.

Takeaways

⚡️ Understanding BS7671 is essential for EV installations.
🚗 Section 722 focuses specifically on electric vehicle charging.
🔌 Different earthing systems like TT, TN-CS, and TN-S each have unique risks.
🔍 PME supplies can shift to TN-CS, increasing safety concerns.
✋ Existing installations may not meet modern safety standards.
⚠️ Electric vehicle charges need proper earthing for safety.
📉 TT systems can mitigate some issues but are challenging to implement.
💡 Using multiple grounding electrodes can lower risk significantly.
🤖 Voltage monitoring devices provide some level of safety, but aren't foolproof.
🏗️ New builds can incorporate integrated grounding systems for better safety.

Garis waktu

00:00:00 - 00:05:00
JW begins by discussing BS7671, focusing on Amendment 1, which pertains to electric vehicle charging installations. He emphasizes the challenges of installations with PME supplies, particularly TNCS systems.
00:05:00 - 00:10:00
He outlines the three types of earthing systems in the UK: TT, TNCS, and TNS, explaining that TT is the easiest to deal with as it relies on a ground rod, while TNCS is the most common yet fraught with issues due to interlinked neutral and earth connections.
00:10:00 - 00:15:00
Additional details about TNS installations are provided, highlighting the separation of conductors and how external damage can potentially reclassify a system as TNCS if repairs introduce linkages between neutral and earth.
00:15:00 - 00:20:00
JW illustrates how external circuitry might be upgraded or replaced with TNCS components, leading unsuspecting property owners to believe they still have a TNS supply, though they may actually be dealing with the hazards of a TNCS.
00:20:00 - 00:25:00
Transitioning to TT systems, JW outlines the drawbacks, including difficulties in electrode installation near buried services and maintaining safety distances from other underground infrastructure.
00:25:00 - 00:30:00
A scenario involving shared charging points between two houses illustrates the perilous voltage disparity that can arise when one side makes a TT conversion, while the other remains with a TNCS connection, posing shock hazards.
00:30:00 - 00:38:39
In conclusion, JW summarizes that TT installations pose fewer risks if already established, while newer TNCS installations might not be as safe as assumed, emphasizing the importance of adhering to regulations and considering practical safety measures when installing EV chargers.

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Video Tanya Jawab

What is BS7671 Amendment 1 about?
It covers regulations for electric vehicle charging installations, particularly concerning earthing methods.
What are the three types of earthing systems discussed?
The three types are TT, TN-CS, and TN-S.
Why are PME supplies problematic for EV charging?
Due to potential voltage risks if the PEN conductor is damaged, creating dangerous conditions.
Can you convert a TN-CS supply to a TT supply?
It's complicated due to various underground service factors and potential safety issues.
What are the five options to ensure safety when using PME for EV charging?
The options include using specific devices that monitor voltage and earth resistance, among other methods.
Is a TT earthing system preferable?
A TT system can be safer if properly implemented, but comes with its own set of challenges.
How can the dangers of high voltage be mitigated?
By using additional ground electrodes and ensuring low resistance connections.
What is the significance of the 70 volts regulation?
It aims to prevent dangerous voltage surges in the event of a fault.
Are there any devices that ensure safety for outdoor charging points?
Some devices monitor and disconnect in the case of voltage detection, but are not foolproof.
What is the ideal solution for EV charging installations?
A proper TT system with low resistance electrodes or three-phase monitoring devices.

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Teks

Gulir Otomatis:

00:00:04
hello i'm jw
00:00:05
today we'll be looking at bs7671 but
00:00:08
it's not actually in this book here it's
00:00:09
on that amendment one which came out a
00:00:11
while ago and then there was those
00:00:12
corrections that came up with it as well
00:00:13
and all of that bother now
00:00:15
section 722 which is what amendment 1
00:00:17
actually covers is
00:00:18
referring to electric vehicle charging
00:00:20
installations only
00:00:22
and what we're going to look at is how
00:00:24
you're going to install something
00:00:26
when you've got a pme supply normally
00:00:29
called
00:00:30
a tn cs when you actually get to the
00:00:32
property itself
00:00:33
and there's five things you can pick
00:00:35
from some of which may or may not be
00:00:37
useful and others
00:00:38
are basically downright impractical and
00:00:41
before you thought about just going oh
00:00:42
it doesn't matter we've got a tns supply
00:00:44
here
00:00:44
well think again because most tns
00:00:46
supplies in the uk
00:00:48
might not be tns anymore they could
00:00:50
actually be tmcs
00:00:52
in disguise so let's just have a look at
00:00:54
that as well and
00:00:55
how that actually works out and the
00:00:57
third option of course is to make it tt
00:01:00
but just a minute because that might not
00:01:01
be any good either because there's a
00:01:02
whole pile of problems involved with
00:01:04
that
00:01:04
as well now in the uk there's three
00:01:07
types of earthing
00:01:08
system that are available and these are
00:01:11
pretty much what you're going to be
00:01:12
given there's not really a whole lot of
00:01:13
choice in what you're going to get
00:01:15
so the first one and it's actually the
00:01:17
easiest one is a
00:01:18
tt arrangement this is where you don't
00:01:21
have
00:01:21
any kind of connection provided by the
00:01:23
electricity company
00:01:25
it's just a question of a rod or other
00:01:27
electrode in the ground
00:01:28
and that is it all you get from the
00:01:31
supplier are the two conductors
00:01:33
line and neutral so if you get a
00:01:36
property that's already got
00:01:37
a tt installation then that's basically
00:01:39
going to be using there's no choice and
00:01:41
this is actually by far the easiest
00:01:43
option
00:01:43
and so if you get one of those then
00:01:45
character of lucky because
00:01:47
that's your only option and you don't
00:01:49
necessarily need any special equipment
00:01:50
or whatever
00:01:51
certainly in the question of those five
00:01:53
items which only apply to
00:01:55
pme supplies next type of supply which
00:01:58
is by far the most common is a
00:02:00
tn cs
00:02:03
and this is typically found on newer
00:02:05
properties and newer meaning anything in
00:02:06
the last
00:02:07
25 or 30 years or so and also any which
00:02:10
have had
00:02:10
new services things put in since then
00:02:14
and with that one you do get the three
00:02:15
conductors so you're getting a line
00:02:18
neutral and the earth connection
00:02:21
crucially on this one at the actual
00:02:23
cutout position where it comes into the
00:02:25
property
00:02:26
the neutral and earth are linked
00:02:27
together
00:02:29
and then outside of the property there's
00:02:31
actually only two wires which will be
00:02:33
the l there
00:02:34
and then the combined neutral and earth
00:02:36
conductor
00:02:37
also called a pin conductor protective
00:02:41
earth and neutral
00:02:42
and the problems around this one and why
00:02:45
you can't just go shoving any old stuff
00:02:46
on the thing particularly outside
00:02:48
all the rises where this conductor here
00:02:50
is the one that gets broken
00:02:52
due to some kind of fault and then what
00:02:54
you end up with there's no neutral ore
00:02:56
earth connected at the installation and
00:02:58
all of this part becomes live because
00:03:00
then when you have your load connected
00:03:03
let's put a light or something in there
00:03:06
it's connected back here but these are
00:03:07
linked together so if this connection
00:03:09
goes away
00:03:11
this is live here so is this and then so
00:03:13
is all of the stuff within the
00:03:14
installation
00:03:15
and this conductor and then is obviously
00:03:16
what's being broken and damaged but
00:03:18
as long as that's intact not a problem
00:03:23
and that's what those five things in the
00:03:24
legs actually apply with so
00:03:26
look at those shortly now the third type
00:03:29
of installation
00:03:30
is a tns
00:03:34
very similar to what we had there but
00:03:35
the difference being
00:03:38
that you've got your line neutral on
00:03:41
earth
00:03:42
inside the property when this goes
00:03:45
outside the property it's actually still
00:03:48
three separate conductors like that
00:03:51
so if one of these gets broken obviously
00:03:54
thinking's not gonna work
00:03:55
but there's no link here between the
00:03:56
neutral and earth conductors so
00:03:58
problems to get with a t and cs supply
00:04:00
don't exist because that conductor that
00:04:02
could be broken
00:04:03
doesn't exist either and even if both of
00:04:05
these got busted
00:04:06
it doesn't matter because again the
00:04:08
neutron earth are not linked together
00:04:10
at the installation the only place these
00:04:13
are linked is way back at the
00:04:14
transformer
00:04:15
where the cable off seat comes from now
00:04:18
that's all very well so you might be
00:04:19
tempted to think well if you've got a
00:04:20
tns supply well that's fine
00:04:21
none of those things in the regulations
00:04:23
apply so obviously it's tns it's not a
00:04:25
tncs but
00:04:26
the problem is that do tns supplies
00:04:29
really exist anymore
00:04:31
and the answer is probably no they do
00:04:33
not
00:04:34
because even if you've got something at
00:04:35
your house which it claims to be tns an
00:04:37
older piece of stuff or whatever
00:04:39
there's a very good chance elsewhere in
00:04:41
the network outside your house where you
00:04:42
can't see
00:04:43
bits of that network may have been
00:04:45
upgraded or replaced or repaired
00:04:47
with pieces of cable or usually used on
00:04:50
the tncs
00:04:51
installation so let's just have a look
00:04:53
at how that could occur
00:04:55
and why tns may not be
00:04:58
what you think it is now this is what a
00:05:00
tns supply would look like
00:05:02
if you could see under the road outside
00:05:04
here's your house with the
00:05:06
three connections inside so line neutral
00:05:08
and earth there
00:05:10
and then the cable itself has three
00:05:12
separate conductors which go all the way
00:05:14
back to the transformer
00:05:15
now it could be nearby or it could be uh
00:05:17
half a mile down the street
00:05:19
so the point here is you've got three
00:05:20
entirely separate conductors there
00:05:22
the only connection between neutral
00:05:26
and earth here is back at the
00:05:28
transformer so if this gets damaged or
00:05:29
broken at any point
00:05:31
even if it's just one two or all three
00:05:32
conductors it doesn't actually matter
00:05:34
because at no point
00:05:36
are the neutral and earth conductors
00:05:38
combined or
00:05:39
linked together in any way and that's
00:05:41
pretty much how it's been for a very
00:05:42
long time
00:05:43
so uh that's absolutely fine there but
00:05:46
of course the problem occurs when
00:05:48
something in the road is damaged so
00:05:49
someone comes and digs up the road to
00:05:51
install something
00:05:52
and they accidentally slice through a
00:05:54
load of the cabling
00:05:56
i might expect that they're just going
00:05:57
to come along and put another piece of
00:05:58
this cable in but
00:05:59
unfortunately it doesn't happen most of
00:06:00
the time because this old lead covered
00:06:03
type cable
00:06:03
pretty much isn't used anymore and all
00:06:06
the sort of joining equipment they have
00:06:08
and things
00:06:08
pretty much isn't up to the standard of
00:06:09
doing it so if this cable got damaged
00:06:12
here
00:06:13
and this could be outside your house or
00:06:15
banging on it could be a quarter mile
00:06:16
down the road or in the next street
00:06:17
where you wouldn't even notice
00:06:19
then they're gonna have to put in some
00:06:20
kind of splice here and quite often
00:06:22
what actually goes in is a piece of
00:06:24
modern cable and some kind of joint box
00:06:26
so
00:06:28
this gets linked through here and then
00:06:30
the other two
00:06:31
rather than having a separate cable you
00:06:33
actually have a single conductor in here
00:06:35
and it joins onto both of these at both
00:06:38
ends
00:06:40
if this is going to be a pme supply
00:06:42
which is going to be
00:06:43
there's going to be maybe a
00:06:45
supplementary electrode installed and
00:06:48
that goes into the ground between this
00:06:49
is all very underground anyhow
00:06:52
and then these parts here are put in
00:06:54
some sort of enclosure
00:06:57
resin filled most likely and all is well
00:07:00
so at your house it still shows up as
00:07:03
what's tns so the three separate
00:07:04
conductors
00:07:05
and for a certain distance outside it
00:07:08
still is
00:07:09
but then we've got this repaired section
00:07:10
here with a new piece of two core cable
00:07:12
in it
00:07:13
possibly got a supplemental electrode
00:07:14
installed as well or maybe not all
00:07:16
depends on
00:07:17
who did it and what the individual area
00:07:18
procedures are
00:07:20
so even though it's tns here
00:07:24
it's not because you've now got this
00:07:26
joined piece here so if something gets
00:07:28
broken
00:07:28
along this section you've got exactly
00:07:31
the same problem as you have on a tn
00:07:32
cs supply in that if this piece here is
00:07:35
damaged
00:07:37
and beyond this could be a few meters
00:07:39
long or it could be hundreds of meters
00:07:40
long depending on where it was
00:07:42
it's just the same as having the link
00:07:44
there it's just that the link is a bit
00:07:45
further away but they're still linked
00:07:46
together
00:07:47
so line coming in the only earth you've
00:07:51
got is basically the neutral now
00:07:53
and all of this part here has a rather
00:07:56
dangerous voltage on it
00:07:58
because of course there's no connection
00:07:59
there anymore just as you'd have if the
00:08:02
pen conductor or cne conductor on a tncs
00:08:06
supply it was damaged
00:08:07
and of course you wouldn't know that
00:08:08
this had occurred unless you called up
00:08:10
the uh
00:08:11
network operator and asked them so what
00:08:14
might be
00:08:15
in your house looks like tns quite
00:08:17
probably isn't
00:08:19
and this diagram here only shows a
00:08:21
single repaired piece fairly short
00:08:23
but if this cable was say 300 meters
00:08:25
long and a whole section has been
00:08:27
replaced for some reason
00:08:28
then of course there could be multiple
00:08:29
pieces like this or in fact the bulk of
00:08:31
it could have been replaced with that uh
00:08:33
two core type cable and you might end up
00:08:36
with only a little tiny bit
00:08:37
to your house having the three
00:08:38
conductors
00:08:40
the other thing which tends to happen is
00:08:41
that these old cables get rotten or
00:08:43
damaged or the connections
00:08:44
where the joint boxes are rust away and
00:08:47
rather than
00:08:48
dig up the whole street to repair those
00:08:49
things what you'll actually get
00:08:51
happening
00:08:52
is that a link will be put in here
00:08:55
where it's in your house this is then
00:08:58
tn cs bit to the network might be
00:09:01
this twin cable or some of it might be
00:09:03
these so there you get tncs at your
00:09:06
house
00:09:06
but by the time they've done that it's
00:09:07
highly likely that bits of the cabling
00:09:09
in the street would have been replaced
00:09:10
with things like this
00:09:12
this is basically where your pme comes
00:09:15
from protective multiple earthing
00:09:16
this being one of them there'll be
00:09:18
another one back at the transformer and
00:09:19
possibly others along the network itself
00:09:23
now another thing to consider is that if
00:09:24
you've already got a tn
00:09:26
cs supply which is by far the most
00:09:28
common now so just two conductors coming
00:09:31
in
00:09:31
and the earth is just connected to the
00:09:33
neutral at the point it comes into the
00:09:35
property
00:09:36
nothing else uh obviously there for the
00:09:37
earth conductor
00:09:39
you might be tempted to think well we
00:09:40
could just uh instead of using that
00:09:42
we'll just convert it to a tt
00:09:43
system and not use that thing for the
00:09:47
car charging equipment but there's a
00:09:49
whole pile of problems here
00:09:50
as well in the simplest form all you
00:09:52
would need to do for your charging
00:09:54
equipment
00:09:55
is simply not connect it to the earth
00:09:57
terminal that we have here you would
00:09:59
just connect the line and neutral
00:10:00
through
00:10:00
and then the earth terminal for the
00:10:01
equipment would be an alert electrode
00:10:04
poked into the ground now let's say this
00:10:07
house here wanted to do that
00:10:09
and i'm going to put our charging piece
00:10:11
over here on the outside
00:10:13
so here's our electric vehicle charger
00:10:16
now of course the charger needs some
00:10:17
connections to it so you would have the
00:10:18
wires coming out from the property
00:10:21
i'm not going to show the protected
00:10:22
devices here but of course there'll be a
00:10:24
fuse box and all the other stuff in
00:10:25
there
00:10:26
so your neutral come out to that one
00:10:29
crucially though you wouldn't connect
00:10:31
the earth terminal here to the earth
00:10:33
channel in the charging equipment
00:10:35
you would install your own earth
00:10:37
electrode in the ground
00:10:40
and then you would connect the earth
00:10:42
tone of the charging equipment
00:10:44
to that and i think well that's fine
00:10:46
because now
00:10:48
even if this conductor here gets damaged
00:10:51
this and the car plugged into it is not
00:10:53
connected to this
00:10:54
shared conductor or at least not on the
00:10:56
actual metal work
00:10:58
so not gonna be a problem however the
00:11:00
problem is
00:11:01
this electrode here where you're
00:11:04
actually going to put this
00:11:05
into the ground now a lot of places have
00:11:07
nice driveways which made of concrete or
00:11:09
paving or something else so
00:11:11
in many cases just putting electrode in
00:11:13
could be a major problem because there
00:11:14
might not be anywhere obvious to put it
00:11:16
and once you can dig holes in people's
00:11:17
driveways and then dig out stuff
00:11:19
underneath and drive electrodes down
00:11:20
underneath and attempt to make some kind
00:11:21
of repair
00:11:22
not really the best choice there but
00:11:25
rather more importantly
00:11:26
where you're going to put your electrode
00:11:28
it has to be a decent distance away
00:11:31
from anything else that's buried
00:11:32
underground and things that are buried
00:11:35
underground
00:11:35
there's a whole pile of stuff such as
00:11:38
cables
00:11:40
most importantly the cables that come
00:11:41
into the house and supply it with
00:11:42
electricity
00:11:44
and everything else such as gas pipes
00:11:47
water pipes
00:11:48
and in fact anything else that's
00:11:50
underground now apart from the risk of
00:11:51
just driving a stake right through these
00:11:53
and causing them to be damaged and then
00:11:54
you've got gas leaks and fires and who
00:11:56
knows what
00:11:58
you can't put an electrode near
00:12:01
to any of these items now how far away
00:12:03
it can be from underground cables those
00:12:05
supplying the electricity to your house
00:12:06
does vary
00:12:07
but in many cases you're looking at the
00:12:09
distances of around five meters
00:12:12
and in many cases considerably more than
00:12:14
that and if you think about the width of
00:12:15
an average house
00:12:16
that could either be the width of your
00:12:18
typical certainly a terraced house or a
00:12:19
semi-detached
00:12:21
so getting the electrode five meters
00:12:22
away from the incoming supply cable
00:12:25
may be entirely impossible the other
00:12:27
thing to consider is that you can't put
00:12:28
it near any metallic pipes on the ground
00:12:30
because
00:12:31
if you had some gas pipes underground
00:12:34
let's draw those in here they would go
00:12:35
into the property
00:12:37
and they're going to go into the next
00:12:38
property and of course they're going to
00:12:40
go all the way along the street
00:12:42
to the next property and so on within
00:12:45
the properties here
00:12:46
all these gas pipes are going to have a
00:12:48
bond that goes over to the earthing
00:12:50
terminal
00:12:50
and it's going to be the same in this
00:12:52
house over here and obviously all the
00:12:54
ones down the street
00:12:55
if you put your electrode in the ground
00:12:57
and it happens to be nearby
00:12:58
one of these gas pipes or water pipes or
00:13:01
whatever else
00:13:02
when a fault occurs and this conductor
00:13:04
has broken
00:13:06
this blue one here is the one that has a
00:13:09
dangerous voltage on it but of course
00:13:10
it's also connected to the main earth
00:13:11
terminal
00:13:12
and it's also connected to this gas or
00:13:14
water pipe that's on the ground so if
00:13:16
your electrode is there
00:13:17
then it's even within a few meters of
00:13:19
the underground gas pipe
00:13:21
that voltage would transfer onto this
00:13:23
electrode
00:13:24
and then you've got the exact same
00:13:25
problem you would have had before it's
00:13:27
slightly better because it's not in
00:13:28
direct contact
00:13:30
but there's still that high likelihood
00:13:31
of a dangerous voltage appearing on this
00:13:33
appearing on the outside of the charging
00:13:35
thing if it's metal and definitely
00:13:36
appearing on the
00:13:37
external metal work of your car that's
00:13:39
plugged into this
00:13:41
so if you're going to convert it to a tt
00:13:43
this has to be many meters away
00:13:46
from anything under the ground gas water
00:13:49
any kind of other metallic pipes and
00:13:50
things that are connected to the
00:13:51
earthing terminal
00:13:52
and in most cases that's going to be
00:13:54
next to impossible to achieve
00:13:57
now here's another scenario two houses
00:14:00
each have an electric car charging point
00:14:02
and it's a shared space in the middle so
00:14:03
it's divided up into the two halves but
00:14:05
it's pretty much the same open area
00:14:07
just happens to be the width of a couple
00:14:09
of vehicles plus a bit of space
00:14:10
and there might be sort of a thin line
00:14:12
of vent or something down the middle
00:14:13
so charging box and electric vehicle
00:14:15
charging box and another electric
00:14:17
vehicle
00:14:18
now if one of these houses had converted
00:14:19
itself to be a tt installation
00:14:22
i'd say it was the end one because it
00:14:23
had a big field over to the side there
00:14:25
so
00:14:25
it could actually put the electrode in
00:14:26
out of sight way over here
00:14:29
so it was a considerable distance away
00:14:30
from anything else and then of course
00:14:32
that was linked in
00:14:33
and went over to the charging point and
00:14:35
i didn't use the other one for that
00:14:37
then tt installation here if this one
00:14:40
over here
00:14:41
is not they just decided to have it be
00:14:43
done on the cheap and they had a
00:14:45
tn cs connection there and somebody just
00:14:47
didn't bother with it or they put just a
00:14:49
uh
00:14:49
a 13 amp plug on the outside wall and
00:14:52
plugged it into that thinking that was a
00:14:53
good idea
00:14:54
when the fault occurs and this conductor
00:14:56
here gets busted
00:14:58
all of the blue here becomes a dangerous
00:14:59
voltage that means that this
00:15:02
particular vehicle here will have a
00:15:04
dangerous voltage on it
00:15:05
relative to the earth itself and even
00:15:08
worse than this
00:15:09
the voltage between these two parked
00:15:12
cars will now be considerable because
00:15:14
this one is connected to the earth from
00:15:16
the
00:15:16
tncs service and this one is connected
00:15:19
directly into the earth itself with an
00:15:21
electrode far away from these so
00:15:23
guaranteed to be a much lower voltage
00:15:24
than this one and of course these cars
00:15:26
close together
00:15:27
they can be touched at the same time
00:15:29
you've got a couple of hundred volts
00:15:31
between them
00:15:32
people are going to get shocked and
00:15:33
injured and this can even happen with a
00:15:36
single house so if you had your car
00:15:38
charging away on the driveway there with
00:15:40
its two wheels
00:15:42
and the charging box was here if your
00:15:44
charging box is connected to an earth
00:15:46
electrode so it's put in the ground and
00:15:48
we managed to get it away from the other
00:15:49
pipes and all the other problems
00:15:52
if you've got say an outside light on
00:15:53
your house
00:15:56
like that and that light happens to be
00:15:58
connected through to the
00:16:01
supply provided there from the ts supply
00:16:03
when this fault occurs where you've got
00:16:05
this break in the
00:16:06
conductor there all of the blue becomes
00:16:09
at a dangerous voltage 200 volts or
00:16:10
something like that
00:16:12
but of course the vehicle isn't because
00:16:14
it's connected via the
00:16:15
system here so then between the vehicle
00:16:17
and the outside light
00:16:19
there's your dangerous voltage so if
00:16:22
you're going to make it tt
00:16:24
you can't have any other items on the
00:16:25
outside of the building here
00:16:27
that are connected to the earth provided
00:16:29
by the supplier
00:16:30
because otherwise when the fault occurs
00:16:32
you're getting that dangerous voltage
00:16:34
between those objects
00:16:36
and it might not even have to be a light
00:16:38
fixture
00:16:39
it could be something as simple as an
00:16:41
outside tap
00:16:42
because if you've got an outside tap
00:16:44
because it's going to come from the
00:16:45
water pipe here
00:16:47
just draw it in there and imagine that's
00:16:49
a tap it's connected to the water supply
00:16:52
which again goes through the street and
00:16:53
of course within the house
00:16:56
that supply is going to be bonded to the
00:16:58
incoming
00:16:59
earth terminal so just as before
00:17:03
your car is sitting there connected to
00:17:05
the charging point
00:17:06
and then between your outside tap and
00:17:08
the charging unit
00:17:09
you've got a dangerous voltage straight
00:17:11
away and there's even one manufacturer
00:17:13
that makes
00:17:14
an outside charging point where you can
00:17:15
have a outside tap put in the bottom of
00:17:17
it as well
00:17:18
so ridiculous so again a really
00:17:21
ridiculous situation
00:17:22
so changing any kind of existing station
00:17:24
to
00:17:25
tt is a pile of problems and not really
00:17:29
something you want to be doing
00:17:30
as yes the car itself might be safe in
00:17:33
isolation
00:17:34
but combined all the other stuff that's
00:17:35
around there it most definitely isn't
00:17:38
and the final point with changing order
00:17:39
t2 you might be considering or tempted
00:17:41
to instead of doing
00:17:42
all that bother with the different
00:17:43
exposed parts and different voltages and
00:17:45
all that hassle
00:17:46
i think well why don't we just not
00:17:47
bother with this tncs supply whatsoever
00:17:50
just throw it all away and why don't we
00:17:51
just convert the whole house to a tt
00:17:53
supply instead because
00:17:55
again that is an option which you could
00:17:56
use so if you're gonna do that first of
00:17:58
all you need to put earth electrode
00:18:00
somewhere suitable so you can't put it
00:18:01
obviously in the way of things under the
00:18:03
ground or anything like that so you'd
00:18:04
have to put it far away in the back
00:18:05
garden
00:18:06
at some considerable distance but let's
00:18:09
say that we did actually do that so
00:18:11
let's put the electrode way over there
00:18:14
in the back garden in a field or
00:18:15
something like that so it's well away
00:18:16
from anything else
00:18:17
buried in the ground and then we're not
00:18:20
going to have
00:18:22
this supplier's earth used at all we're
00:18:25
just going to leave that disconnected
00:18:26
there
00:18:27
and then this coming in will be the
00:18:30
real earth that we're going to be using
00:18:33
and that will be a tt arrangement
00:18:35
absolutely fine
00:18:37
but just to make it no it isn't
00:18:38
absolutely fine because yes there's
00:18:40
another problem here as well if you've
00:18:42
got metal pipes coming into your house
00:18:44
from the gas and water and whatever
00:18:46
other services you may have in your area
00:18:48
if these pipes are metal and they're
00:18:49
coming into your house
00:18:51
this pipe here is connected to everybody
00:18:54
else's house in the street and in the
00:18:55
house over here
00:18:56
where that pipe comes into their house
00:18:58
and goes to the various parts of the
00:18:59
building
00:19:01
of course they're going to have their
00:19:02
main bonding installed which comes
00:19:04
across
00:19:05
to the combined earth and neutral
00:19:07
terminal there and that's a metallic
00:19:09
path all the way through into your house
00:19:11
and of course the next house down the
00:19:12
road and all the others in the street
00:19:15
so if this is coming into your house and
00:19:17
of course regulations require that uh
00:19:19
metallic parts coming in
00:19:20
are bonded so you put your bonding
00:19:22
conductor in like this
00:19:24
from your main earth terminal to the
00:19:26
state water pipe
00:19:28
is this now really a tt system
00:19:33
and the answer is no it isn't because
00:19:35
what you've now got
00:19:37
is the potential from the tncs or the
00:19:40
pme earth coming in
00:19:42
via this water pipe from next door and
00:19:44
next door and so on
00:19:45
and being made of metal that's going to
00:19:46
be a very low resistance
00:19:48
far lower than any earth rod stuck in a
00:19:50
field ever will be so what you've now
00:19:52
got here
00:19:53
is not tt anymore it's actually
00:19:56
a tncs with an extra electrode installed
00:20:01
now the extra electrode may help in the
00:20:03
situation where the conductor is broken
00:20:06
all of this becomes a dangerous voltage
00:20:08
because it's giving a bit of an extra
00:20:09
connection
00:20:10
to the earth there but in reality it's
00:20:13
not going to have a huge impact
00:20:15
that becomes a dangerous voltage as
00:20:17
we've seen before because it's all
00:20:18
connected through
00:20:19
at the same point here live go to
00:20:22
appliances
00:20:23
comes to all those comes back on there
00:20:24
so it's got nowhere to go
00:20:26
so in terms of what's dangerous here all
00:20:28
of this conductor here
00:20:30
and pretty much anything else that's
00:20:31
connected to it so the metal pipes come
00:20:34
in your house and your neighbors
00:20:36
is bringing that dangerous potential
00:20:37
into your property
00:20:39
and then of course it's going to go on
00:20:40
to things that are connected to outside
00:20:41
like your car charging point
00:20:43
the outside tap that solves the metal
00:20:46
pipe going straight to it
00:20:47
so not really a tt system so the only
00:20:50
way you can do it
00:20:51
if you've got that is to replace these
00:20:54
pipes here
00:20:55
with plastic and that includes things
00:20:58
like your gas pipe which you can't
00:20:59
really do with plastic unless it's
00:21:00
already plastic in the ground
00:21:02
plastic water pipes and have no
00:21:04
connection whatsoever
00:21:05
to any other metallic parts from
00:21:08
adjoining properties
00:21:10
and on top of that you still need to
00:21:11
make sure that your earth electrode or
00:21:13
electrodes or maps or whatever
00:21:14
are a decent distance away from all of
00:21:16
this buried underground stuff
00:21:18
as we saw previously if you put this
00:21:20
anywhere near anything underground it's
00:21:22
going to pick up a voltage from this
00:21:23
when the fault occurs
00:21:24
and again bring that dangerous potential
00:21:26
into your property and onto your
00:21:28
cart charging point so in reality then
00:21:31
what are your options so a tt system
00:21:33
already
00:21:34
that's probably the best and that's all
00:21:35
you can use because if it's tt already
00:21:38
that's all you've got
00:21:39
if it's the tns
00:21:43
probably not and the reason being that
00:21:45
it's almost going to be
00:21:47
a tn cs in disguise and then of course
00:21:50
that's the one where you have the
00:21:52
problems because it's not
00:21:55
suitable to use when the protective
00:21:56
contact gets damaged and that's where
00:21:58
you have dangerous voltages outside
00:22:00
and that thing is entirely why things
00:22:01
like caravans can't have a pma supply
00:22:04
either
00:22:04
that's exactly the same reason and why
00:22:06
it's definitely not recommended things
00:22:07
like swimming pools
00:22:08
hot tubs and other things that are
00:22:10
outside so if you've got a tt
00:22:12
installation in your house already and
00:22:13
that's what it's been forever
00:22:15
then that's really the best situation
00:22:17
tncs is probably not tns
00:22:19
because it's almost certainly going to
00:22:20
be converted to tn at cs
00:22:22
and then of course that's where the
00:22:23
problems occur and that's when we have
00:22:25
those five
00:22:26
options in the regulations which you can
00:22:29
allegedly use to mitigate the problem
00:22:31
when
00:22:31
the conductor is broken so let's just
00:22:34
have a look at those five
00:22:35
and see if they're actually any good now
00:22:38
in section 72 the
00:22:40
regulation is 7241141
00:22:43
and this refers to a tn system and it
00:22:46
basically says a pme earthing facility
00:22:47
shall not be used as the means of
00:22:49
earthing for the protective inductor
00:22:50
contact of a charging point located
00:22:52
outdoors or that might be reasonably
00:22:54
expected to be used to charge a vehicle
00:22:56
located outdoors
00:22:57
unless one of the following methods is
00:22:58
used now in reality
00:23:00
vehicles are going to be charged
00:23:01
outdoors because that's where people put
00:23:03
them
00:23:03
so there's very few instances where you
00:23:05
would have that on the say an indoor
00:23:07
charging arrangement
00:23:09
and this is the thing with the five
00:23:10
options now the first option
00:23:12
being number one is where you have a
00:23:15
charging point that forms part of a
00:23:16
three-phase installation
00:23:18
and this is where it supplies loads
00:23:19
other than electric vehicle charging and
00:23:21
because of the type installation
00:23:23
the maximum voltage is going to exceed
00:23:25
70 volts now
00:23:26
this is never going to be used in a
00:23:27
domestic installation simply the fact
00:23:30
that domestic installations
00:23:31
don't have three phase so of course
00:23:33
that's out the window completely
00:23:35
and even if you're in a situation that
00:23:36
did as we've covered in other videos
00:23:38
the likelihood of having an installation
00:23:40
where the loads on it are always going
00:23:42
to be decently balanced
00:23:43
is pretty much zero anyhow so that
00:23:46
option is usually a fail
00:23:48
and certainly as a fail on domestic
00:23:49
where you've only got single phase
00:23:50
available
00:23:51
option number two is quite an
00:23:53
interesting one which we'll actually
00:23:54
come back to
00:23:55
and look at at the end because it may
00:23:57
end up being the actual proper solution
00:23:59
in the final scheme of things although
00:24:01
you may not like the price of
00:24:02
actually doing it now the other three
00:24:05
are the various devices which may or may
00:24:09
not exist and some manufacturers claim
00:24:10
to have them and others don't and
00:24:12
some of them may never exist so the
00:24:14
first device is number three there
00:24:16
protection against later shock is
00:24:17
provided by this device this is the one
00:24:19
that monitors the voltage
00:24:21
and it's the voltage between the earth
00:24:24
of the installation
00:24:26
and the actual earth
00:24:30
which means it's going to be outside and
00:24:32
if this exceeds 70 volts
00:24:34
for more than four seconds then it will
00:24:35
disconnect the equipment and crucially
00:24:37
disconnect the
00:24:39
installation earth as well because
00:24:40
that's where your dangerous voltage will
00:24:41
appear
00:24:43
all very well in theory however the
00:24:44
problem with this is that to detect the
00:24:46
voltage between two parts
00:24:48
you've got this already but to take the
00:24:50
voltage between that and the actual
00:24:51
earth outside you're going to need some
00:24:52
kind of earth electrode to be put in
00:24:54
because there's no other way you can
00:24:55
measure voltage between two items you've
00:24:57
got to have a connection to them
00:24:59
and whether this is going to be an
00:25:00
actual electrode or some kind of thin
00:25:02
probe as some manufacturer may have
00:25:03
suggested the reality is going to have
00:25:05
to shove something in the ground
00:25:06
and then straight away back to all those
00:25:08
problems we had before where
00:25:10
electrode or probe or sensor whatever
00:25:12
else it is going in the ground
00:25:13
there's got to be many many meters away
00:25:16
from anything else in the ground like
00:25:17
pipes cables or whatever else
00:25:19
you've got to make sure that it's
00:25:20
obviously not going to be poking through
00:25:21
anything else in there
00:25:22
it's all the same problems as a tt
00:25:24
installation so of course why would you
00:25:26
actually bother
00:25:27
the only difference is that you're
00:25:28
having the earth and they need an extra
00:25:30
bit of machinery to connect between it
00:25:31
so
00:25:32
that really is a bit of a bust and
00:25:33
that's one that's called this unicorn
00:25:35
device which uh
00:25:36
theoretically exists from these one
00:25:38
manufacturer but again why would you
00:25:40
bother when you can just make it a tt if
00:25:41
you're going to go to what hassle of
00:25:42
having electrodes
00:25:44
now number four is protection against
00:25:47
electric shock in the single phase
00:25:48
installation
00:25:49
is by another device and this one
00:25:51
monitors the voltage
00:25:52
between the line and neutral conductors
00:25:56
and if the voltage goes outside of a
00:25:57
certain range which is based in the
00:25:59
normal range which is 207
00:26:01
to 253 volts then it will disconnect
00:26:05
and also of course remove that
00:26:06
protective conductor as well
00:26:09
now if the pen conductor is broken
00:26:13
in some cases yes the voltage will go
00:26:15
either lower than this
00:26:17
or higher than that the problem here is
00:26:19
that it doesn't do that in
00:26:20
all cases and this is due with a
00:26:23
three-phase system
00:26:24
becoming unbalanced and whilst your
00:26:26
house doesn't have a three-phase system
00:26:28
the connection to it from the street
00:26:29
almost certainly will be a three-phase
00:26:31
system
00:26:32
and in some cases some houses are going
00:26:35
to get a high voltage
00:26:36
some of them will get a low voltage but
00:26:38
it's totally possible for some to have
00:26:39
voltage that's within this range
00:26:42
that's between a line of neutral but
00:26:44
crucially between
00:26:46
what you might think is the neutral and
00:26:47
then the earth outside
00:26:49
that can still be more than 70 volts
00:26:53
because what's then happened is that
00:26:54
both of these have gone up
00:26:57
relative to the earth here so the
00:27:00
difference between them is still within
00:27:01
this boundary
00:27:02
but because they're both lifted they're
00:27:04
now both considerably above the
00:27:06
actual earth outside and if that's more
00:27:08
than 70 volts then again there's your
00:27:09
problem
00:27:10
dangerous shocks and whatever else are
00:27:12
going to happen
00:27:13
so that in itself may work in some
00:27:15
situations but it most certainly won't
00:27:17
work in all of them
00:27:18
so yeah not really a particularly
00:27:21
desirable result
00:27:23
and then number five is some other
00:27:25
device which isn't really defined in the
00:27:26
regulations at all
00:27:28
it's an alternative device that doesn't
00:27:30
result in a lesser degree of safety from
00:27:31
the two devices mentioned earlier now
00:27:34
as far as i can see there aren't any
00:27:35
devices on the market which would do
00:27:37
that
00:27:38
because it does state it doesn't provide
00:27:40
a lesser degree of safety than using
00:27:42
three or four now
00:27:45
lesser degree of safety than three means
00:27:47
it's going to have to do at least what
00:27:48
number three would do and that's where
00:27:49
you've got a sense in the actual ground
00:27:51
itself that will work in all cases
00:27:53
but nobody's going to install that
00:27:54
because you need to put another
00:27:55
electrode in
00:27:56
better than four there is one way of
00:27:59
doing it
00:28:00
and certainly one matter at least has
00:28:01
this and essentially what it does it's a
00:28:03
voltage monitoring device
00:28:05
which is just the same as we had in
00:28:06
number four and that's again between
00:28:08
that range of voltages
00:28:09
as stated in the regulations it's the
00:28:11
207 to 253.
00:28:14
obviously manufacturers may choose a
00:28:15
slightly different range if they deem
00:28:17
that appropriate
00:28:18
and then what at least one of them has
00:28:19
got is a sense
00:28:21
coil similar to an rcd
00:28:25
so i've got a magnetic core there with
00:28:27
the sense wires coming off of that
00:28:29
what goes through this
00:28:32
is the protective conductor that goes to
00:28:34
the charging equipment so
00:28:36
here would be your electric car
00:28:40
all the wires going through and that
00:28:43
protective conductor coming through
00:28:45
there
00:28:46
let's draw that in green that's a bit
00:28:47
more obvious
00:28:49
what it's doing is monitoring the
00:28:50
current that flowed through this
00:28:51
protective conductor
00:28:53
now in normal cases there shouldn't be
00:28:54
any current going through there so if it
00:28:56
detects that there's current flowing
00:28:57
through this
00:28:58
electronics in the device will then
00:29:00
disconnect all of the conductors to it
00:29:02
and therefore remove that danger from it
00:29:04
so basically it's going to cut that off
00:29:05
completely
00:29:05
leaving it totally isolated now that
00:29:08
sounds like a good idea in theory
00:29:10
but unfortunately there's a problem with
00:29:11
this
00:29:13
cars have rubber tyres and they're
00:29:15
generally insulated from the ground that
00:29:17
they're standing on
00:29:19
so if a dangerous voltage occurs on this
00:29:21
conductor initially nothing will happen
00:29:24
the only time something's going to
00:29:25
happen is if some unfortunate individual
00:29:27
was standing here next to the electric
00:29:30
car
00:29:32
and if they touch the car where's the
00:29:34
current going to flow well it's going to
00:29:35
go through the
00:29:37
sensing coil here through the car and
00:29:39
then through the person and into
00:29:41
of course the ground or earth down here
00:29:45
and then that will disconnect and all
00:29:46
this well but not really because it's
00:29:48
already put the current through the
00:29:49
person and giving them a fairly
00:29:50
unpleasant shock
00:29:51
now while this is better than nothing
00:29:53
it's unfortunately not good enough
00:29:55
because
00:29:56
this is equivalent to using an rcd as a
00:29:58
single means of protection so basically
00:30:01
stuff sits around being live when
00:30:03
someone grabs hold of it it might
00:30:04
disconnect
00:30:05
and that's similar to if you've had your
00:30:06
house with the lighting circuit with no
00:30:08
protective conductor in it you can't
00:30:10
just bung an rcd on and hold it all this
00:30:12
well because you've got metal items
00:30:13
there because then
00:30:14
again it would sit there doing nothing
00:30:15
with live parts hanging down live
00:30:17
switches
00:30:18
when some person came along and touched
00:30:19
it they get a shock and then the thing
00:30:21
disconnects
00:30:22
and the regulator's question is four one
00:30:23
five one two which states that the use
00:30:26
of rcds is not recognized as a solid
00:30:28
protection
00:30:28
and does not obviate the need to apply
00:30:29
when the protected measures specified in
00:30:31
four one four and four which are all the
00:30:32
usual
00:30:34
automatic disconnection supply and so on
00:30:36
now whilst the device in the charging
00:30:38
point is not technically an rcd because
00:30:40
it's sensing on a single conductor only
00:30:43
the reality is that the principle is the
00:30:44
same you don't want a system which
00:30:46
requires people to get a shock before it
00:30:48
actually disconnects you want to happen
00:30:50
obviously well in advance of that and
00:30:52
then that comes back to having a probe
00:30:53
in the ground to detect the voltage
00:30:54
between the actual earth
00:30:56
and the conductors in the installation
00:30:57
which again is the same
00:30:59
effort and bother that's putting in a tt
00:31:01
installation in the first place
00:31:04
so what then is the answer well the
00:31:06
answer is certainly with the regulations
00:31:07
we currently have them
00:31:09
is the second item out of those five
00:31:11
which states the main i think terminal
00:31:13
the installation is connected to an
00:31:14
installation of electrode by a
00:31:15
protective conductor
00:31:16
and the resistance of the earth
00:31:17
electrode to earth shall we search that
00:31:19
the maximum voltage between the main
00:31:20
earthing terminal the installation and
00:31:22
earth in the event of an open circuit
00:31:23
fault in the pen conductor
00:31:25
and so on does not exceed 70 volts
00:31:28
so what this means then if you've got
00:31:29
your house
00:31:32
and it has a tn cs supply which let's
00:31:34
face it uh
00:31:35
most of them obviously will it's sitting
00:31:38
on the ground there
00:31:41
we'll put the suppliers coming in and of
00:31:44
course your earth is then just provided
00:31:45
as
00:31:46
a connection from that particular
00:31:48
conductor
00:31:49
what this means is that when this
00:31:51
conductor is damaged a dangerous voltage
00:31:53
is going to occur here
00:31:54
and the way to reduce this voltage is to
00:31:56
connect this
00:31:57
to an additional earth electrode that
00:32:00
you've got outside of your house
00:32:02
now the problem with putting a single
00:32:03
electrode in is you're going to have a
00:32:04
fairly high resistance in the soil or
00:32:06
whatever
00:32:06
if you can get less than 100 ohms with a
00:32:08
single one then you're doing pretty well
00:32:10
and this particular regulation there is
00:32:11
a part in the annex
00:32:13
in section 722 and this gives you some
00:32:16
examples and if you do the calculations
00:32:18
you want something in the region
00:32:20
of 5 ohms or less
00:32:23
perhaps in the case of 2 ohms or less
00:32:27
now if you want to sting electrode in
00:32:30
you're not going to be getting anywhere
00:32:31
near that so how can it be done well the
00:32:33
answer is you don't put it in a single
00:32:35
stick in the ground
00:32:36
what you do is you dig up the person's
00:32:38
driveway like that
00:32:41
and inside the ground before you put
00:32:42
your driveway in you put a big mesh
00:32:45
or grid of tape this could be that
00:32:48
reinforcement fabric you can buy for
00:32:49
putting in concrete or whatever
00:32:51
and that goes in there under the
00:32:52
driveway over an area of say
00:32:55
10 or 20 square meters so once that's
00:32:58
inside
00:32:59
and it's being installed you have your
00:33:00
concrete put over the top or whatever
00:33:02
nice surface you're having tarmac or
00:33:03
paving slabs or whatever else
00:33:06
before that's done you need to have a
00:33:07
connection made to that metal work
00:33:08
underground
00:33:10
that goes inside and connects to the
00:33:11
main earth terminal in the building
00:33:13
so once it's all finished and covered
00:33:14
over it looks exactly the same
00:33:16
but all this metal work buried
00:33:18
underground it's going to have a massive
00:33:19
surface area compared to that tiny
00:33:21
little rod you might have stuck in for a
00:33:22
tt installation so its
00:33:24
resistance there is going to be much
00:33:25
lower that's how you get it in this
00:33:27
single digit ohm range
00:33:29
and then when this conductor becomes
00:33:31
damaged and broken
00:33:33
although the voltage on this thing would
00:33:35
normally go fairly high because it's
00:33:37
connected to the earth here
00:33:39
very solidly that will keep the voltage
00:33:41
here much lower
00:33:42
what will actually happen is that the
00:33:44
current in the installation
00:33:46
which will be from your line connectors
00:33:49
to your appliances in the house
00:33:51
and then coming back if that was totally
00:33:54
open you get 230 volts here
00:33:56
because it's got a decent path going
00:33:58
back to the earth here of a low
00:34:00
resistance a couple of ohms it's got
00:34:02
somewhere for the current to flow
00:34:04
go back into the ground eventually gets
00:34:05
back to the transformer so the voltage
00:34:07
here
00:34:08
is kept down at a decent level and in
00:34:11
this case your vehicle
00:34:13
sitting on the driveway there connected
00:34:16
to this
00:34:18
voltage difference between the vehicle
00:34:20
itself and exposed metal parts
00:34:22
and the ground itself with this massive
00:34:24
metal grid in
00:34:25
is going to be fairly small and
00:34:27
certainly well under
00:34:28
the 70 volts there
00:34:32
that's required in the regulations now
00:34:34
this is totally permitted and it's
00:34:35
actually suggested in that section two
00:34:38
connecting your own electrode to a tncs
00:34:41
provided earth
00:34:41
is also permitted and has been pretty
00:34:43
much forever most people should not do
00:34:45
it because in most cases a single rod is
00:34:47
useless
00:34:48
but if you've got a big section like
00:34:50
this then it's absolutely ideal
00:34:52
and the other way it could be done if
00:34:53
you're going to be building a new house
00:34:54
for example
00:34:55
is when you're building the house and
00:34:57
putting in the concrete foundations
00:34:58
which might be say a
00:35:00
strip foundation for example if when the
00:35:03
house was built
00:35:04
they put in a load of reinforcement
00:35:06
fabric in here
00:35:08
and also in here and had the good sense
00:35:11
to make it exposed here so it could
00:35:13
connect to the main earthing terminal
00:35:14
then you've got again this massive
00:35:16
section all the way under the house
00:35:17
there
00:35:18
huge surface area connecting to the
00:35:19
actual earth itself and again
00:35:21
you could use that and if it was a raft
00:35:24
type foundation
00:35:25
which is just basically a slab of
00:35:26
concrete in the ground that whole thing
00:35:28
could be filled with a metal
00:35:31
reinforcement and you can have this
00:35:34
gigantic
00:35:35
earth mat under the entire property
00:35:37
connected through
00:35:39
problem solved now of course it's all
00:35:42
very well if you've got a new house so
00:35:43
you're putting in your driveway
00:35:45
obviously if you've got an existing
00:35:46
installation you can't use this because
00:35:48
it's unlikely the customers wanting to
00:35:50
pay thousands for a new driveway just to
00:35:52
have their electric car plugged in but
00:35:54
certainly at the moment and unless some
00:35:56
magical solution occurs in the future
00:35:57
which it
00:35:58
won't do this is realistically the only
00:36:01
proper and safe way to ensure that this
00:36:04
dangerous situation doesn't occur
00:36:06
the other things in the regulations may
00:36:07
work in some of the situations such as
00:36:09
the voltage monitoring or that current
00:36:11
going to the uh
00:36:12
through the protective induction to the
00:36:13
device and then disconnecting it and of
00:36:15
course there's various combinations of
00:36:16
monitoring current on various conductors
00:36:18
and whatever
00:36:18
but in the end this is really the only
00:36:21
proper and fully foolproof way of doing
00:36:24
it
00:36:25
provided that the electrode resistance
00:36:27
here is in the single digit ohms that's
00:36:29
required
00:36:31
and the final thing we'll just cover
00:36:32
quickly here is that if you have
00:36:34
a three-phase supply into your property
00:36:38
so that would be the three phases or
00:36:40
three line conductors coming in
00:36:43
and you've also got the neutral coming
00:36:44
in as well and of course you would also
00:36:46
have the
00:36:47
protective conductor which in most cases
00:36:49
is going to be part of that anyway
00:36:51
if you've got that as an installation
00:36:54
then there is another possible choice
00:36:56
and this is where this o pen device
00:36:58
comes from which is made by a company
00:37:00
called matt
00:37:00
e because it's got all three phases and
00:37:04
the neutral
00:37:06
this and any other devices that might be
00:37:07
made along those similar lines
00:37:09
can determine when this conductor has
00:37:11
been broken
00:37:12
because what will happen is that the
00:37:14
voltage point
00:37:16
if you imagine that was sort of the
00:37:16
middle point and they were connected to
00:37:18
it normally that would be
00:37:19
zero relative to all three
00:37:22
if that's then broken if you had your
00:37:25
phase diagram like that
00:37:27
normally this is at zero in the middle
00:37:30
when that's broken the neutral point
00:37:31
goes away because loads on this are
00:37:33
going to be unbalanced
00:37:34
that point may shift in one of the three
00:37:37
directions there so if you said it
00:37:38
shifted over here
00:37:40
that's where your dangerous voltage to
00:37:41
ground occurs but by monitoring the
00:37:43
current and the voltage across
00:37:44
all of the conductors that can be
00:37:45
reliably detected
00:37:47
and then it can disconnect the whole lot
00:37:49
so that particular thing is
00:37:51
totally valid and that is an ideal
00:37:52
solution but of course it only works
00:37:55
where you have all three phases
00:37:56
available in say most domestic
00:37:58
properties that's not going to be an
00:37:59
option
00:38:00
because simply they don't have a
00:38:01
three-phase supply installed
00:38:04
so that can be useful let's say only of
00:38:06
any value with three-phase supply
00:38:08
if you don't have access to all three
00:38:10
phases that technology is with no value
00:38:13
whatsoever and bearing in mind that that
00:38:16
company that makes that device matter it
00:38:17
also makes other devices but those are
00:38:19
again just the voltage monitoring types
00:38:20
of things
00:38:21
which we saw earlier which again will
00:38:23
work in some cases
00:38:25
unfortunately not all of them
00:38:28
so that's it for this video and
00:38:30
unfortunately that's just a big can of
00:38:31
worms opening up there in terms of what
00:38:33
you can do with
00:38:34
electric vehicle charging connections
00:38:35
but until next time
00:38:37
thanks for watching