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What is Floating Neutral ? Easiest Explanation with Circuit Simulation - YouTube
Channel: Gaurav J - TheElectricalGuy
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In this video, you’ll understand the concept
of Floating neutral, what are it’s effect
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and what causes floating neutral.
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I’ll also show you a live circuit simulation
of floating neutral, which will make things
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crystal clear.
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So, to understand the concept of floating
neutral, you need to watch the video.
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We know that, when the load on the system
is balanced, sum of return currents of all
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the three phases is zero.
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And hence, current flowing through neutral
conductor is also zero at every instance.
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This we have learned in detail in the video
in which I explained, “if we can remove
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the neutral wire”.
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If you have’t watched it, I’ll give link
for that video down in the description of
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this video.
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Go check that out.
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It’ll help you to understand this video
more clearly.
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To understand the floating neutral, you must
know why neutral is necessary.
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That’s why we’ll look at that first.
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So, when the load is balanced, current flowing
through neutral is zero.
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And in that case, we can even remove the neutral
wire.
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But this situation is not practical is distribution
system.
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In distribution system, the load is always
unbalanced.
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And that’s when neutral comes into picture.
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Now, when I am saying balanced load that means,
all the load connected are taking equal amount
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of power.
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And when load connected takes different amount
of powers then the load is said to be unbalanced.
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Remeber that.
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Now, let’s go to our distribution transformer.
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This is connected in delta-star manner meaning,
primary or incoming is connected in delta
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connection and secondary or outgoing is connected
in Star connection.
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This common point right here, is our neutral
point.
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This here is our load.
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Which are three different houses.
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Of course, power consumption of these load
will be different.
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When the load in not balanced or equal on
all the phases, sum of return currents will
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not be zero.
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This I’ll also show you in a simulation
in few minutes.
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So this is where we’ll need neutral wire.
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Job of Neutral wire is to carry the unbalanced
current and help in keeping the phase to neutral
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& phase to phase voltage constant.
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Which is our case, let’s say, phase to neutral
is 250 volts & phase to phase is 433V.
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These voltage you’ll get even if the load
is unbalanced when neutral is there.
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I’ll tell you what I am trying to say here
via a circuit simulation.
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Here we have our three phase supply connected
in star.
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That’s our neutral point connected to ground.
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We also have a three LEDs connected to each
phase in star as load.
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Each LED is consuming 5 watts.
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….
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So, we can say the load is balanced.
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We have also connected neutral wire here.
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Now, across each load we have connected a
voltmeter to check the voltage across each
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load.
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And an ammeter is connected in series in the
neutral wire.
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This ammeter will tell us if any current flows
through neutral.
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Now, let’s start the simulation.
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In the first scenario the load is balanced.
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And as you can see, no current is flowing
through neutral wire.
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You can see ammeter read 0 A. Which proves
our statement.
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In this case even if we remove the neutral
wire it will not affect the circuit.
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……. as you can see, even when the neutral
is removed voltage across each load is constant
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that is 250 V. Let’s connect the neutral
back.
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Now, in scenario two, we’ll unbalance the
load.
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Let me make the second LED 10 watts and the
third one 3 watts.
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All LED now taking different power, which
means the load is unbalanced.
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Now let’s start the simulation.
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As you can see the ammeter is now reading
32.2 mA.
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This is the current coming because of the
unbalanced load.
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Which proves our second statement also.
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Even if the load is unbalanced, voltage across
each load is constant I.e. 250V.
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You can see the reading of voltmeter.
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That’s why neutral wire is of so much importance
in distribution system.
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Now, let’s say the neutral wire is broken
somewhere.
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Since the neutral is broken, current will
try to find out another way to return.
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This will create unequal voltage across the
loads.
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Some load may have very high voltage than
normal and some may have very less voltage
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than normal.
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And in this case, the phase to neutral and
phase to phase voltage keeps on changing as
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the load varies.
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And hence, this situation is called as “Floating
Neutral” or some people also calls it as
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floating ground.
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Floating neutral does’t mean that the neutral
wire floats in air.
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As the value of potential of such open neutral
keeps on changing or it keeps on floating
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based on the load, it is called as “Floating
Neutral” or “Floating ground”.
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I’ll also show you the floating neutral
in our simulation in few minutes.
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And that’s very interesting.
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And by the way, if you are new on this channel
& interested in learning electrical engineering
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in easiest way, then do subscribe to my channel.
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Floating neutral can be very dangerous.
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It causes, very high or very low voltage across
the load.
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Load connected phase to neutral can experience
maximum voltage of phase to phase.
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Which in our case is 433 volts.
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So, if you see here, our appliance or any
device which is connected across phase to
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neutral is designed for 250 volts but, now
it may have to face 433 volts.
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Definitely this high voltage will damage the
device.
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Not only this, but floating neutral can also
create hazardous touch voltage at equipment’s
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body.
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Because the neutral is broken, electricity
will try to flow through different paths.
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It can be equipment’s body also.
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And if someone touches that, that person will
have a serious injury or in worst case death.
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If your house has floating neutral, you may
experience flickering of lights.
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In such case, you have to immediately call
your electrician and get it checked.
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Otherwise you are under very high risk of
getting electric shock or fire hazard.
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There are multiple reasons which can cause
floating neutral.
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Like
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Neutral broken at source side I.e. at distribution
transformer
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If this happens, majority of the customer
will face voltage variation.
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Some of them may face very high voltage maximum
upto line to line voltage, and some may experience
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low voltage.
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Majority of the equipment connected may get
damaged.
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Floating neutral can also happen if the overhead
neutral line is broken.
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In such case, customers connected to that
phase will be affected.
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It can also happen because of poor workmanship
or loose connection.
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If you know any other reason that can lead
to floating neutral, do let me know via comments.
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Now, let’s go back to our circuit simulation.
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Where we’ll create floating neutral.
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Here load is unbalanced.
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Neutral is carrying some current.
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Now let’s say the neutral is broken.
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I’ll delete the neutral from load.
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When I delete the neutral see what happens.
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As you see from the reading of voltmeter.
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Voltage across the load in no more constant.
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LED one is having 284 volts, lED two having
168 volts & LED three having 318 volts.
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And our LEDs are meant to handle only 250
volts.
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Now, if the load changes.
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Let me make LED three of 10 watts…..
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As you can see, again the voltage across the
load is changed.
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This will keep on changing or keep on floating
with the change in the load.
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This situation is what we call as Floating
neutral
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