Earthing or Grounding Transformer

Earthing Transformer or grounding transformer is the neutral grounding transformer - star connected on the primary and has an open delta on secondary. Open Delta has two terminals. A resistor is connected across these two terminals.

Whenever a fault occurs, voltage will be induced in the open delta and there will be a voltage drop in the resistor connected.
This voltage drop will be sensed by the earthing transformer connected across this resistor. At the secondary of the earthing transformer we have the neutral displacement relay which will give a trip signal or an alarm whenever its settings exceed a particular value.

Earthing transformer can also be called a large Potential transformer (Open delta PT).

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Why use the VCB at High Transmission System ? Why can't use ACB?

Actually the thing is vacuum has high arc quenching property compare to air because in VCB ,the die electric strengths equal to 8 times of air . That y always vaccum used as in Ht breaker and air used as in LT .

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What is an exciter and how does it work?

There are two types of exciters, static exciter and rotory exciter.purpose of excitor is to supply the excitation dc voltage to the fixed poles of generator. Rotory excitor is an additional small generator mounted on the shaft of main generator. if it is dc generator, it will supply dc to the rotory poles through slip ring and brushes( conventional alternator). if it is an ac excitor, out put of ac excitor is rectified by rotating diodes and supply dc to main fixed poles.ac excitor is the ac generator whose field winding are stationary and armature rotates. initial voltage is built up by residual magnetism.It gives the starting torque to the generator.

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What is Automatic Voltage regulator(AVR)?

AVR is an abbreviation for Automatic Voltage Regulator.It is important part in Synchronous Generators, it controls the output voltage of the generator by controlling its excitation current. Thus it can control the output Reactive Power of the Generator.

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Enlist types of dc generator?

D.C.Generators are classified into two types 1)separately excited d.c.generator 2)self excited d.c.generator, which is further classified into;1)series 2)shunt and

3)compound(which is further classified into cumulative and differential).

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1 ton is equal to how many watts?

1 ton = 12000 BTU/hr and to convert BTU/hr to horsepower,

12,000 * 0.0003929 = 4.715 hp therefore 1 ton = 4.715*.746 = 3.5 KW.

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Why syn. generators r used for the production of electricity?

synchronous machines have capability to work on different power factor(or say different imaginary power varying the field emf. Hence syn. generators r used for the production of electricity.

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what is the difference between synchronous generator & asynchronous generator?

In simple, synchronous generator supply's both active and reactive power but asynchronous generator(induction generator) supply's only active power and observe reactive power for magnetizing.This type of generators are used in windmills.

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Give two basic speed control scheme of DC shunt motor?

By using flux control method:in this method a rheostat is connected across the field winding to control the field current.so by changing the current the flux produced by the field winding can be changed, and since speed is inversely proportional to flux speed can be controlled 2.armature control method:in this method a rheostat is connected across armature winding by varying the resistance the value of resistive drop(IaRa)can be varied,and since speed is directly proportional to Eb-IaRa the speed can be controlled.

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Which type of A.C motor is used in the fan (ceiling fan, exhaust fan, padestal fan, bracket fan etc) which are find in the houses ?

Its Single Phase induction motor which mostly squirrel cage rotor and are capacitor start capacitor run.

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What is the significance of vector grouping in Power Transformers?

Every power transformer has a vector group listed by its manufacturer. Fundamentally it tells you the information about how the wingdings are connected (delta or wye) and the phase difference between the current and voltage. EG. DYN11 means Delta primary, Wye Secondary and the current is at 11 o clock referred to the voltage.

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What is 2 phase motor?

A two phase motor is a motor with the the starting winding and the running winding have a phase split. e.g;ac servo motor.where the auxiliary winding and the control winding have a phase split of 90 degree.

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whats the one main difference between UPS & inverter ? And electrical engineering & electronics engineering ?

uninterrupted  power supply is mainly use for short time . means according to ups VA it gives backup. ups is also two types : on line and offline . online ups having high volt and amp for long time backup with with high dc voltage.but ups start with 12v dc with 7 amp. but inverter is start with 12v,24,dc to 36v dc and 120amp to 180amp battery with long time backup.

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What will happen when power factor is leading in distribution of power?

If their is high power factor, i.e if the power factor is close to one:

1.losses in form of heat will be reduced,

2.cable becomes less bulky and easy to carry, and very

cheap to afford, &

3. it also reduces over heating of transformers.

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What is vaccum currcuit breaker.define with cause and where be use it Device?

A breaker is normally used to break a circuit  while breaking the circuit, the contact terminals will be separated. At the time of separation an air gap is formed in between the terminals. Due to existing current flow the air in the gap is ionized and results in the arc. various mediums are used to quench this arc in respective CB's. but in VCB the medium is vacuum gas. since the air in the CB is having vacuum pressure the arc formation is interrupted. VCB's can be used up to 11kv.

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:what is ACSR cable and where we use it?

ACSR means Aluminium conductor steel reinforced, this conductor is used in transmission & distribution.

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Which motor has high Starting Torque and Staring current DC motor, Induction motor or Synchronous motor?

DC Series motor has high starting torque. We can not start the Induction motor and Synchronous motors on load, but can not start the DC series motor without load.

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what happen if we give 220 volts dc supply to d bulb r tube light?

Bulbs [devices] for AC are designed to operate such that it offers high impedance to AC supply. Normally they have low resistance. When DC supply is applied, due to low resistance, the current through lamp would be so high that it may damage the bulb element.

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what is meant by armature reaction?

The effect of armature flu to main flux is called armature reaction. The armature flux may support main flux or opposes main flux.

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Why, when birds sit on transmission lines or current wires doesn't get shock?

Its true that if birds touch the single one line (phase or neutral) they don't get electrical shock... if birds touch 2 lines than the circuit is closed and they get electrical shock.. so if a human touch single one line(phase) then he doesn't get shock if he is in the air (not touching - standing on the ground if he is standing on the ground then touching the line (phase) he will get a shock because the ground on what we standing is like line (ground bed - like neutral)। and in the most of electric lines the neutral is grounded..so that means that human who touch the line closes the circuit between phase and neutral.

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why link is provided in neutral of an ac circuit and fuse in phase of ac circuit?

Link is provided at a Neutral common point in the circuit from which various connection are taken for the individual control circuit and so it is given in a link form to withstand high Amps. But in the case of Fuse in the Phase of AC circuit it is designed such that the fuse rating is calculated for the particular circuit (i.e load) only.So if any malfunction happen the fuse connected in the particular control circuit alone will blow off.

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