NEUTRAL WIRE AND UNBALANCE CURRENT:

Q1) Difference between ground wire and neutral wire?

ANS) Neutral wire is a return path for unbalance current. Electrically neutral is zero potential with respect to live potential. While ground wire is used for safety purpose. It provides a low impedance path for the fault current to flow to the ground, instead of our body and thus saving us from dangers of electrocution.

Q2) if the neutral wire is at zero potential than how does it provide return path for the current?

ANS) Neutral is a reference point in circuit and when we say it has zero potential, it means that”

“ If the neutral wire is at zero volts then the live wire will be at 220 volts”

Neutral is 0 volts with respect to earth. It means it has same voltage as of the ground. In reality Neutral doesn’t have any voltage. We just assume it to 0 volts so that we can use it for comparison purpose

Q3) what is the difference between balance and unbalance loads?

ANS) Balance loads are those in which power is splitted equally among all phases i.e.

Load on Phase A= Load on Phase B = Load on Phase C

EXAMPLES: Three phase Motors, Converters; Rectifiers using 3 phase input supply are

common examples of balanced loads.

Unbalanced load=the power loading on each phase is unequal.

Load on phase A=/=Load on phase B=/=Load on phase C

EXAMPLES:  A single phase / 2 phase loads on a three phase system is called

Unbalanced load.

A balanced system is more efficient because the heating losses are minimized per watt of power transfer..

If the load is unbalanced, there is a neutral or imbalance current flow. Current imbalance can cause voltage unbalance and if the system is not monitored well for neutral conductor, probability of failure will be high.

Q4) Can neutral wire be made thinner than a phase wire?

Ans) No it cannot be made thinner than a phase wire. We have to follow rules and regulation of our electricity act and according to it, it should not be made thinner than a phase wire.

Q5) what is unbalance current?

During balanced condition there will be no current flowing through the neutral line and hence there is no need of the neutral terminal. But when there will be unbalanced current flowing in the three phase circuit, neutral is having a vital role. It will take the unbalanced current through to the ground and protect the transformer or other equipment

Neutral or unbalance current which flows through neutral impedance raises the load side neutral potential with respect to source neutral point which is normally earthed and at zero potential. This means at load side there will be potential difference between neutral and earth. This can be unacceptable for certain equipment

Unbalanced currents result in higher operating temperature, shortened motor life, and efficiency reduction.

Q6) why is it dangerous to touch live wire of a supply rather than a neutral wire?

ANS) Live wire is the wire which has a potential other than ground potential and usually the neutral is grounded. So, when you touch neutral wire, you won’t get a shock as long as you stand on earth which is grounded and at same potential as neutral wire (i.e. ground potential). But the live wire is not at ground potential so when you touch live wire you will get more shock because there is more potential difference between live wire and earth as compare to neutral wire and earth

Q7) what should be the ground to neutral voltage?

ANS) The potential difference between earth and neutral lines in our homes should be 0 volts ideally. The tolerance permitted is 5-10% of 230 volts. In other words, earth to neutral potential difference measured using a voltmeter should be between 11.5-23 volts

If potential difference doesn’t lie in this range than:

1)     May be earthing is not done properly.

2)     There may be a fault in the wiring due to which the potential of neutral has risen  above its nominal value

Q8) why is there no neutral for High tension lines? Or why transposition of HT lines is required?

ANS) Neutral lines as the name implies carries the neutral/unbalance currents. T/L currents are balanced out using transposition. Without transposition, the system begins to develop some unbalance between phases, with a resulting build up in neutral current. T/L currents are balanced out using transposition. So there is no need for neutral in HT lines

Q9) what happens if I connect a bulb between live and ground wire and not neutral? Will the bulb glow?

It will glow but it is not advisable. Normally the neutral is grounded and will have same zero potential or near to zero. But in most of the installations the grounding is not proper and neutral will show some potential. The brightness of the bulb will be lower

Q10) If a bulb is connected between two phases, will it glow or not?

ANS) The bulb is rated at 220 volts and if we connect the bulb between two phases than voltage will rise to 440 volts. The blub will glow much higher than usual but for the time being as high potential will burn out the filament wire of the bulb.

Q11) why is it said to wear a rubber slipper while working with electrical circuits?

ANS) Rubber is a very bad conductor of electricity and as long as you are wearing a rubber slipper, it will insulate you from the ground and possibly no current will flow from the wire through your body to ground.