Electricity Billing.pptx

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Electricity Billing

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• _{Electrical energy is most useful form of energy because it can be most conveniently}

transformed into other forms of energy like heat light, mechanical energy that we require in our day to day life.

• _{But electricity is not readily available and is required to be produced (generated) in a}

factory called power station.

• _{Like any other manufacturing process, the production (generation) of electricity also}

need some cost to be incurred - Plants and Equipment, Inputs (water, fuel etc.), Ash smoke disposal systems, Personnel

• Cost of Transmission and Distribution to the large number of consumers of various categories (viz. domestic, commercial, industrial, agricultural etc.)

• _{All these costs when added together constitutes the total cost of electricity which in}

the consumers have to share according to the quantum of electricity consumed taking into account the nature and time of use of electricity by each category of consumers.

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The basic difference between power and energy –

Power –

It is the capacity to Generate or consume electricity. The term “Power” specifies the capacity of generation or consumption in terms of Kilowatt (KW) or Megawatt (MW). One Megawatt as we know in one thousand Kilowatt.

Energy –

It is the Power Generated or Consumed by utilizing the capacity for a duration of time. If one kilowatt Power has been generated or distributed continuously for one hour, it is said that an energy of One Kilowatt hour has been generated or used. Similarly if Five kilowatt of Power is generated or consumed for Two hours, an energy of 10 ( = 5 X 2) kilowatt hour has been generated or consumed and so on.

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Electric Power, AC, and DC

Electricity

Key Question:

How much does electricity cost and what do you

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Electric Power, AC, and DC Electricity

• _The_watt_{(W) is a unit of power.}

• _Power_{is the rate at which energy}

moves or is used.

• _{Since energy is measured in}_joules_,

power is measured in joules per second.

• _{One joule per second is equal to}

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Power in electric circuits

• _{One watt is a pretty small amount of power.}

• _{In everyday use, larger units are more convenient to}

use.

• _A_kilowatt_{(kW) is equal to 1,000 watts.}

• _{The other common unit of power often seen on}

electric motors is the horsepower.

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Power

P = VI

Current (amps)

Voltage (volts)

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Calculate power

• A light bulb with a resistance of 3Ω is

connected to a 1.5-volt

battery in the circuit shown at right.

• _{Calculate the power used by}

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Paying for electricity

• Electric companies charge for the

number of kilowatt-hours used during a set period of time, often a month.

• _One_{kilowatt-hour}_{(kWh) means that}

a kilowatt of power has been used for one hour.

• _{Since power multiplied by time is}

energy, a kilowatt-hour is a unit of

energy.

• _{One kilowatt-hour is 3.6 x 10}6_joules

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Calculate power

• Your electric company charges 14 cents per kilowatt-hour. Your coffee maker has a power rating of 1,050 watts.

• _{How much does it cost to use the coffee maker one hour}

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Power in AC circuits

• For a circuit containing a motor, the power calculation is a little different from that for a simple resistance like a light bulb.

• _{Because motors store energy}

and act like generators, the current and voltage are not in phase with each other.

• _{The current is always a little}

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Power for AC circuits

• Electrical engineers use a power factor (pf) to calculate power for AC circuits with motors

P = VI x

pf

Avg. current (amps) Avg. voltage

(volts)

Power (watts)

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The amount of Electricity used is measured in units

To calculate the amount used we use the following formula

Units used = PRESENT reading - PREVIOUS reading

Meter Reading

Present Previous

32514 32347

Meter Reading

Present Previous

60134 59929

Units used = 32514 - 32347 = 167

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Calculate the units used for each of the following sets of readings Present Previous 41067 40878 23107 22939 81074 80873 00453 00269

Units = 41067 - 40878= 189 Units = 23107 - 22939=

Units = 81074 - 80873 = Units = 00453 - 00269 =

168 201 184

We can calculate the cost of the electricity using Total cost = units used x cost per unit

Find the cost of 125 units of electricity at 6p per unit

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Electricity Bills

Calculate the total cost for each of the following

1. 3412 3349 2. 6035 5950 3. 1023 0881 4. 0894 0782 5. 0402 0324

Present Previous

1 unit of electricity costs 4p

Units used Total cost 63

85 142 112 78

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Other costs on an electricity bill

Standing charge - this is a fixed amont of money paid even if no electricity is used

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Bright Spark Electricity

House H. Old, 3 This Street 11/09/96 - 14/12/96

Meter Reading Charges Amount

Present Previous

2065 1876 units at 8p

Standing charge

Sub-total

VAT at 17.5%

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Power factor correction

Power factor. Ratio of useful power to total power drawn from AC supply

Inductive devices use reactive power.

Motors, welding sets, induction heaters, fluorescent lights.

Power Factor Correction (PFC)

• Uses capacitors

• Reduces power consumption

• Leads to increased supply capacity

• _{Increases life expectance of electrical}

equipment

Image source: Power factor correction, An introduction to technology and techniques. Carbon Trust

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Why household wiring is done using

parallel connection

• _{Houses are generally wired in parallel rather than series circuits for a}

couple of reasons. Think of the series circuits on old Christmas tree lights. If one light bulb doesn't work, none of the lights will come on, because all the electricity has to flow through each light bulb in

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• _{Another problem with series wiring is that as we extend the circuit,}

adding more lights, each light we add makes the other lights dimmer. That's because we're increasing the total linear resistance in the circuit. The voltage is fixed, so as the resistance increases, the current flow

must decrease. Neither of these are desirable situations and, therefore, our houses are wired in parallel

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• The other feature of parallel circuits is that adding another light or

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• If this seems like magic to you, you'll just have to accept that this is the way electricity works. Incidentally, you can extend this picture. If you put a third branch in with another 60-watt light bulb, it too, would draw 1/2 amp, and the total current drawn in the common parts of the circuit would be 1 1/2 amps. There are three parallel paths, each carrying 1/2 amp.

• You can see that if you put in thirty 60-watt light bulbs, you are going to draw 15- amps (I=P/V=30x60/120=15). Fifteen amps flowing through a conventional

household wire is close to the point where you'll blow the fuse or trip the breaker.

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• _{Assuming your ECG bill for the month of September 2016 was GH₵}