Frequently Asked Questions(FAQ)


Basics of Electric current:


The necessary conditions for electric current to flow are:
Completeness of circuit - Flow of electricity can be considered as a process in which the electrons are drawn from the earth by a power plant. These electrons move through the power lines to our equipment and travel all the way back into the earth. This circuit needs to be complete in order for current to flow.
Potential difference - Another factor deciding the direction of flow of current is (electric) potential. Current always flows from a higher potential to a lower potential. In other words it can be said that electrons flow from lower potential to higher one. (the direction of electric current is opposite to that of the electrons). So we need the potential difference for current to flow.
Path of least Resistance- Factor that decides the path a current will flow in case of parallel paths is the (electric) resistance offered by the path. Current will always flow in the path that offers least resistance.

1.What is substation?
Ans(1):

Substations transform high voltage to low voltage or low voltage to high voltage depending upon the needs. Different voltage levels of substation placed between generation of electricity and consumer. A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages.
Substations generally have switching, protection and control equipment and one or more transformers. In a large substation, circuit breakers are used to interrupt any short-circuits or overload currents that may occur on the network.


Thus, when a substation is of rating 66/11 kV, means substation has been designed to receive 80 MVA on 66 kV and it will distribute the received power on 11 kV. Similarly 33/11 kV, means substation has been designed to receive 5MVA on 33KV and it will distribute the received power on 11 kV.


2. What is feeder?
Ans(2):

In electric power distribution, Feeder is a Voltage power line transferring power from a distribution substation to the distribution transformer. The Feeder consists of 3nos conductors (R,Y and B Phase) emanating from Substation to Distribution Transformer.
In electrical wiring circuit in any premises, feeder means the wire carries power from transformer/switch gear to a distribution panel.


3.What is the meaning of 1 Unit Electricity ?
Ans(3):

1 Unit Electricity is the amount of electrical energy consumed by a load of 1 kW power rating in 1 hour. It is basically measurement unit of electrical energy consumption in Joule. 1 kWh (kilo watt hour) and 1 Unit are same. 1 kWh is the amount of energy consumption by 1 kW load in one hour. Therefore, 1 Unit = 1 kWh.
1 Unit Electricity = 1 kWh


= 1 kW x 1 Hour
= 1000 W x 3600 seconds
= 3.6×10^6 Joule

Therefore, 1 Unit Electricity is equal to 3.6×10^6 Joule of electrical energy consumption.



4.What is Group Operating Switch(GOS)?
Ans(4):

Generally GOS(Group operating switch) has 3nos blades(or isolators) for connecting (R,Y,B) lines(feeder) emanating from substations.
Generally GOS is connected between electrical substation and feeder starting point, as isolation point for isolating feeder from substation for general maintenance and used for working under fault condition of specific feeder in distribution system.


5. What is 1ph,3ph and open delta connection:?
Ans(5):

Single phase connection:
Alternating Current, single phase, 50 c/s., 230 volts, between phase and neutral.
In Single Phase connection, One phase line (from 3numbers of conductors of feeder) and neutral line will be connected to consumer premises. This type of load is used only for lighting load and below 5KW of load.

Three Phase connection:
Alternating Current, 3 phase, 50 c/s., 400 volts, between phases and 230 volts between phase and neutral.
In Three Phase Connection, 3nos of phases (all 3nos of conductors of feeder) and neutral line connected to consumer premises. This type of load normally used where load requirement is more than 5KW and normally used for industrial loads, data centres, mobile towers, power grids etc.

Open delta connection:
Open delta connection, where 2 blades of GOS(Group Operating Switch) connected to 3 outgoing lines of feeder and one blade of GOS kept open.
This provision is made for not allowing 3ph motors connected to specific feeder. All three phase motors require 3phase supply, this provision will supply 2ph supply in 3 outgoing conductors, disallowing motors running. Only lighting load and small capacity of 1ph motors will run. This provision is used by distribution system by distribution companies.


6. Why don't birds get electrocuted sitting on power lines?
Ans(6):

Current flows in a closed circuit. A bird sitting on a transmission line does not complete the circuit. If the same bird keeps one leg on one line and another leg (or any part of its body) on another line (or the neutral points), then it will be electrocuted.


7. Why don’t we get electric shock touching a battery?
Ans(7):

If voltage driving the current is less, then shock cannot be felt. The current will not flow through body if required voltage is not enough. It’s the Current that causes the sensation of ‘shock,’ and current only flows through your body if the voltage driving the current is high enough to create a current flow through your skin or whatever.

Batteries have rated voltages of 1.5 V, 3 V, 9 V ,12 V.

Human body usually has a resistance of 2500 to 100,000 ohms. Body resistance is not a fixed quantity. It varies from person to person and from time to time.

Let's go with 2500 ohms,
I=V/R I=12/2500= 0.0048A

This much current through body is negligible. Human body will not feel shock.
It’s the Current that causes the sensation of ‘shock,’ and current only flows through your body if the voltage driving the current is high enough to create a current flow through your skin or whatever.


8. Relation between V(voltage) and W(Watt)?
Ans(8):

Voltage is the unit of difference in electrical potential between two points or the electromotive force. Watts is the unit of power and generally used when talking about electrical power. It can also be interpreted as rate of energy transfer.

wheraeas Ampere is a measure of the current.

So the relation between the two for an electrical circuit is,

Power = Voltage * Current

In terms of units, it becomes

watt= voltage* ampere


9. What is LILO(Last In Last Out)fashion connection?
Ans(9):

The incoming transmission line of substation tapped to another incoming transmission line of other substation. ( parallel run of incoming lines to different substations).


10. How to calculate current at different voltage level of feeders of substation?
Ans(10):

Calculation of current At 220KV for 1MW,

P=√3 V I cos⁡φ

1MW(1 X 10^6)= 1.73 X 220 X I(current) X 0.90

I(current)=3Amps.

Current for 1MW at 220KV =3Amps

Similarly changing voltage for calculation of Electric current at different voltage level is,

1MW(At 220KV level) =3Amps
1MW(At 110KV level) =6Amps
1MW(At 33KV level) =20Amps
1MW(At 11KV level) =60Amps


11.What is Open Access?
Ans(11):

Open Access enables the users whose connected load is more than 1MW to buy cheap power from open market. This allows the customers to choose from number of competitive power companies, rather than being forced to buy power from local utility as monopoly.


12.What is IPP?
Ans(12):

An independent power producer(IPP) has the facilities to generate electric power for sale to utilities and end users as per the PPA(Power Purchase Agreement) executed with public companies or other non utilities.

Sources of power generation:
Non-renewable: Coal, Fossil fuel,Natural gas,Petroleum,Nuclear
Renewable: Biomass,Biofuel,Hydro,Thermal,Tidal,Wave,Solar,Wind
Co-gen: Sugar factory


13. What is Captive and Group Captive Generation?
Ans(13):

Captive Generation:
Electricity generation facility used by themselves and excess generated electrical power transmitted to utilities or non-utilities as per PPA executed. This can be off Grid or they can be connected to electric grid for transmission of excess generated electricity. This type of facility used by most of industrial and commercial application.

Group captive generation:
The owner of captive generation is more than one member or group of members. Captive generators generate the electrical power for their own use and transmit rest of electrical power to the electrical grid.


14.What is Co-Generation in Open Access Electricity?
Ans(14):

Co-generation produces two forms of energy from one fuel. One of the forms of energy is heat and the other is electricity or mechanical energy.

Cogeneration or Combined Heat and Power (CHP) is the combined generation of heat and power. Cogeneration first involves producing power from a specific fuel source, such as natural gas, biomass, coal, or oil. During fuel combustion, cogeneration captures the excess heat which would have otherwise been wasted.


15.What is Wheeling and Banking?
Ans(15):

“Wheeling” means the operation where by the distribution system and associated facility of a transmission and/or distribution licensee as the case may be, are used by the company for the conveyance of electricity on payment of charges.

For example,
Captive generators and IPPs transmit the generated power to the transmission and distribution system to meet the demand of end consumers either utility or non-utility depending upon PPA executed.

“Banking” means residual electrical energy after utilization by the “Exclusive” or “Partly Exclusive” Consumer or “captive consumption” out of the injected energy in a month into the transmission and/or distribution system of Corporation/ESCOMs, which will be utilized for its own use or for wheeling to its “Exclusive” or “Partly Exclusive” Consumers at a later date/month, as per the terms and conditions set forth in this agreement.

For example,
under a banking agreement an electricity surplus in any state will be sold to other state which requires power. When that state (which has supplied power) requires the power again, they take same amount of power from those states when needed.


16.What is Aggregator?
Ans(16):

An aggregator is a energy service provider which can increase or reduce the electricity consumption of consumers according to total electricity demand on the grid.

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