Advantages of Thermal Power plant

Thermal power plants are the power plants in which coal combustion is used for generating electrical energy. These are also known as steam power plants.

There are so many advantages and disadvantages of Thermal power plants as below:-

Advantages of Thermal Power plants

1.      Lower Fuel cost:-

Main advantage of Thermal power plant in comparison to other power plants is that fuel i.e. coal is very much cheap in comparison to other fuel power plants.

2.     Availability of Fuel:-

There is abundant availability of coal and also cost of extraction of coal is quite cheaper.

3.     Lower installation cost:-

Thermal power plants installation cost is very much lower than other power plants.

4.     Ease of Installation irrespective of location:-

Thermal power plants can be installed anywhere in world as coal used of these power plants can be transported by rail/ road/ ship.

5.     Lower space requirements

Space required for installation of Thermal power plants is very much lower than Hydro power plants.

         Simpler heat production cycle

Cycle of heat production is quite simpler than other power plants i.e. heat production cycle is very simple.

7.      Ease of Maintenance

Maintenance of thermal power plants is quite simple. Thermal power plant technology is very old one so process knowledge is abundant available for Thermal power plants.

8.     Safer Operation

Thermal power plants are considered safe in comparison to nuclear power plants. Any failure may leads to cascading effects in nuclear power plants but not in thermal power plants.

9.      Dependability:-

Thermal power plants boiler is more dependable, as thermal power plants supply power during peak load as a base power and in off peak load is valued as power plant fuel.

Disadvantages of Thermal power plants:-

1.      Excessive Pollution problem

Main disadvantage of associated with thermal power plants is the pollution caused by these power plants. These power plants produces large amount of smoke and fumes. This harmful smoke and fumes leads to acid rains and also very harmful to human beings. Coal used in thermal power plants leaves behind very harmful byproducts after combustion.

2.     Higher power generation cost

Power generation cost in Thermal power plants is higher than Hydro power plants as there is no requirement of fuel in these plants.

3.     Lower efficiency

Efficiency of these power plants of quite low in range of 30%.

Open Delta connections; V-V connections

In electrical Systems we have seen Single phase and three phase transformer, Single phase Transformers have single winding and three phase transformers have three windings. These windings are connected in connections such as star-delta, delta-delta, star-star connections. There is another connection known as open delta connections, which consist of two windings of transformers.

Open delta connections are done when one winding of Transformer get faulty so as to continue the operation of Transformer but at reduced load.

Open delta connections are as shown below:-

There are only two windings on both Transformer primary and secondary sides.

Open delta connections are often known as V-V Connection Transformers. Open delta connections are usually used to cater small loads.

Power Delivered by Open Delta connected Transformer:-

Power delivered by open delta connections in comparison to 3-winding Transformers is about 57.7% of power delivered by Three winding Transformers.

Calculations for the same as shown below:-

From Figure above you can see that:-

In case of delta connections ILine = √3 X IPhase

And in Open delta connections ILine =  IPhase

Power delivered by Transformer in VA for Delta connection will be = 3 VL X IPhase

In case of open delta connection power delivered by Transformers in VA will be= √3 X VL X IPhase

Power delivered by open delta connected Transformer= √3 X VL X IPhase

Power delivered by Delta connected Transformer                 3 VL X IPhase

Now from both Power’s we get; Power output of open Delta connections is 57.7% of Power delivered by delta connected power Transformer.

Advantages of Open delta connections:-

Open delta Transformer connections have following advantages:-

1.       These are used where Three phase power load is lower as cost of 3-winding Transformer is very higher.

2.       When Delta-delta connected transformer one winding get burnt than open delta connections will restore supply but with reduced load.

Disadvantages of Open Delta connections:-

With open delta connections power factor of the system get reduced to 86.6%. When load connected at Open delta Transformer is having power factor 1 , then system power factor for open delta connection s will be 0.866.,But when there are delta connected Transformer is connected to that load then system power factor will be 1 means that of load.

Current Transformer Technical Specifications

Current transformers are used to convert alternating current of higher value to lower value depending upon the requirement. Current Transformers has many applications in electrical systems. 

Current Transformers usually have two types of designs:-

1.      Window type

2.      Ring Type

There are generally two type of applications where Current Transformers are used:-

1.      Measurement Type Current Transformers

2.      Protection Type current Transformers

Measurement type CT’s design requires the inclusion of core and winding which will which will when connected to its rated burden; perform within the limits of error as indicated by the standard’s specification. It is an advantage for a measurement type transformer to saturate above this range, which provides a protection against damage to instruments by limiting the secondary current when surge currents or faults appear in the primary circuit.

There are following Specification of current Transformers:-

Rated Transformation Ratio:-

It is the ratio of rated primary current to rated secondary current

Rated primary current: 

It is primary current which is to be Transformed to secondary current as per requirement. Usually rated primary current is the current flowing in system whose value to be converted to as per requirement. CT should be selected according to this current.

Rated secondary current: 

This is the secondary current of Transformer. This current is obtained after Transformation by CT. Typical values of secondary current are 5 A and 1A.

Rated burden: 

This is expressed in VA and is an apparent power of the secondary circuit of CT. It is specified on CT’s as per rated secondary current of CT’s at 0.8 Power factor.

Accuracy class: 

Accuracy class will depend upon type of application where CT is used. In case of metering accuracy class is 0.2, 0.5, 0.1, 1, 3 or 5.  It means that the errors have to be within the limits specified in the standards for that particular accuracy class. The accuracy class of measuring CT is 0.2 it means the error limit will be of 0.2%. This means that if we try to measure 100 A with a 0.2 class CT, the measured value may be either 100.2 or 99.8 A.

For protection type CT’s  the CT s should pass both the ratio and phase errors at the specified accuracy class, usually 5P or 10P where 5 stands for 5% and 10 stands for 10% and P stands for Protection.

 Current error (ratio error): 

This error is introduced into measurement by CT generally due to Transformation error. This error is difference between primary current to be measured and Secondary current multiplied by Transformation ratio.

This is expressed by formula as below

Current error, percent =[ (K X.Is)- (Ip)] x 100 / Ip

Where, K= rated transformation ratio

Ip= actual primary current

Is= actual secondary current

Accuracy limit factor: 

This is error value of primary current upto which the CT complies with composite error requirements.

Phase displacement:

Phase displacement as clear from its name is difference in phase between the primary and secondary current vectors.

 The phase displacement is said to be positive when the secondary current vector leads the primary current vector. It is usually express in minutes.

Composite error:-

This error is the subsequent limitation of the harmonic content of the secondary current which is necessary for the correct operation of certain types of relays.

Diameter of CT:-

Bore diameter of the CT shall not be less than 40 mm. Ring type CTs shall have suitable clamp to fix the CT to panel Board.

Highest Withstand Voltage: -

This is highest voltage which is needed to withstand by CT without getting faulty. This doesn’t include the voltage variations in case of fault conditions.

General Technical Specifications of Current Transformers

Standards applicability: -

IS/IEC 60044-1 (2003): Instrument Transformers, Part 1: Current Transformers

BS 3938:1973 :Specification for current transformers

Insulation class: -

E (120°C max)

Test voltage: -

For Ring (Window) type CT : 4KV 50 Hz for 1 min

For Wound type CT : 3KV 50 Hz for 1 min

Operating frequency: -

50Hz

Rated primary rating: -

1A to 7500A

Rated secondary output: -

5A standard (1A on request)

Rated burden: -

1, 1.25, 1.5, 2.5, 3.75, 5, 7.5, 10, 12.5, 15, 20, 30, 45, 60, 100 VA

Class of accuracy: -

0.2, 0.2S for laboratory and power measurement

0.5, 0.5S for accurate measuring, kWh

1 for general measurement

3 for indicating instruments

Ambient temperature:

- -20°C…+45°C

Storage temperature: -

-50°C…+80°C

Thermal short circuit current (Ith):-

40xIn for Wound type CT and

60xIn for Bus Bar type CT.

Dynamic short circuit current (Idyn):-

2.5xIth

Instrument security factor (FS): -

2.5, 5, 10

Limits of current error and phase displacements for measuring current transformers

(Classes from 0.1 to 1)

Limits of current error and phase displacements for measuring current transformers

(For special applications)

Limits of current error and phase displacements for measuring current transformers

(Classes 3 and 5)

Fleming Left Hand and Right Hand rules

There are two laws in electrical field for determining direction of three parameters Magnetic field, Current, & force.

If you know any of these two remaining parameter direction will be determined by Fleming rules. There are two Fleming rules:-

1.     Fleming Left Hand rule

This rule is applicable for Electric Motors

2.     Fleming Right Hand rule.

This rule is applicable for Electrical generators.

1.     Fleming Left Hand rule:-

According to this law Whenever any current carrying conductor is placed in magnetic field then force is experienced on the conductor in a direction perpendicular to magnetic field and current.

Same is shown by Fleming left hand rule.

Now let’s take an example as shown below where a conductor having length “L” is placed in magnetic field having strength “H”. This magnetic field produces a current “I”. This magnitude of force which acts on conductor is as F= BIL

Now according to Fleming left hand rule, take  three fingers forefinger, Second finger and Thumb all in right angle to each other. Now point fore-finger towards the direction of magnetic field, Second finger will points towards the direction of current then thumb will give the direction of force on conductor. Magnitude of the force on conductor will be = BIL

Where, B represents strength of Magnetic field.

2.     Fleming Right Hand rule:-

According to Faraday's law of electromagnetic induction, whenever a conductor moves inside a magnetic field, there will be an induced current in it.

Now if a conductor forcefully moved inside the magnetic field, there will be a relation between the direction of applied force, magnetic field and the current. Then relation between Magnetic field force, Current and applied force will be given by Fleming right Hand rule.

Now according to Fleming right Hand rule Hold the first finger, Second finger and Thumb of your right hand all in right angle to each other. Then point forefinger towards line of force, then thumb will point towards direction of applied force and Second finger will give direction of current induced in conductor.

Battery Calculation for UPS

It is important to select battery size according to UPS capacity otherwise appropriate backup of UPS can’t be obtained.

To calculate battery size according to UPS capacity is as below:-

UPS Backup [in hours]X UPS Capacity in VA = Battery Ah
            Volts* Power factor

From Above formula we see that:-

UPS Backup(in Hrs) means backup requirement of application

UPS Capacity is in VA

Volts is the voltage of battery is usually 12V

Power factor is the power factor of connected load. If you don’t know power factor then take Power factor as 0.8.

Let’s take an example of 500 VA UPS, Battery voltage is 12 V and Power factor as 0.8 and UPS backup required is of 2 hrs then battery size in Ah is as below:-

2X 500 = Battery Ah

12X0.8

Battery Ah= 1000/9.6

It comes approximately as 100Ah so battery requirement is 100 Ah for 500 VA capacity for backup of 2 hrs.

If there are UPS of higher ratings then there will be requirement of more batteries to be either connected in series or parallel.

Then following formula is used in this case:-

UPS Backup [hrs] =N(series) X VoltsX Battery Ah X N(parallel)/(UPS capacity in VA)

Where, Series and parallel of batteries combination is calculated as per user requirement.

If there are two or more batteries are required then following formula is used:-

Backup [in hours] = No. of batteries X Battery Ah X Volts / (Load/p.f.)

Geysers construction; Geysers working principle; Selection of Geysers

Geysers are integral part of Household. They are used to heat the water. Now in this article we will discuss about:-

Geyser works on the principle that electrical energy is converted into heat energy. Heating element is used to generate the heat to heat the water. The heater and immersion rods have same principle but only difference is of controlling and protections in geysers.

Geysers are of three types:-

1.       Pressure Type

2.       Non-Pressure type

3.       Instantaneous Type geysers

Now let’s discuss them one by one:-

1.       Pressure Type Geysers:-

These Types of geysers are usually storage type geysers. In these geysers have a storage tank where water is kept under pressure, this pressure allows hot water to flow in taps and showers at good flow-rate.

In these geysers cold water inlet is kept at bottom of geyser and hot water outlet is kept at Top of geyser. Whenever there is requirement of Hot water, hot water withdrawn get equally displaced by cold water. By keeping cold water inlet at bottom of geyser ensures that geyser never gets emptied and avoid the burning of heating element.

2.       Non-Pressure type geysers:-

These geysers are very which similar to pressure type geysers with only difference is that it has single outlet which displaces hot water when the valve on the cold water is  opened. In these geysers thermostat is installed on water supply system.

3.      Instantaneous type Geysers:-

These type of geysers are available in both  pressure and non-pressure types. But  non-pressure type instantaneous geysers are most commonly used. In these geysers heating element is wired around the pipe. Heating element is used to heat the water matching the flow rate. Heating element used in these type of geysers is of higher rating. Material used for these geysers is of durable  material  so as to ensure safety.

Geyser Parts

There are following parts of a geyser:-

(a)    Inlet Tube:- As clear from name it is used for cold water inlet in geyser

(b)   Heating element :- This is used to heat the water

(c)    Outlet valve:- This is used for hot water outlet from geyser

(d)   Steel Tank/ Fiber Tank:- These are used to hold all parts of geyser and also water is stored in this tank in  case of storage type geysers.

(e)    Pressure relief Valve:- This is used to protect the geyser in case of high pressure in geyser which was generated during heating up of water.

(f)     Temperature cut off Switch (thermostat):- This is used to switch off power supply when temperature rises above the limit.

(g)     Anticorrosion Anode rod:- This is used to keep steel tank free from corrosion. The rod is usually made of magnesium which attracts corrosive elements and further prevents tank from corrosion.

(h)   Insulation:- Insulating material is used to keep water warm for long time. This material used for insulation is an epoxy or glass lining 

Geysers Internal Parts are as shown below:-

While Selection of Geyser following points needed to be taken in consideration:-

1. Star Rating if Geyser

2. Standing losses per day:- These losses means if geyser is kept on 24 hrs when water get heated up. Usually 25 Ltr 5 star Geyser standing losses/24 hrs are 0.5 KWH/24 hrs.

3. Short circuit protection in Geysers:- Although Pressure relief valve and Thermostat are provided for protection of geysers. But now days additional Safety feature is provided in geysers so as to protect the Humen beings against shock if Short circuit occurs in geysers, in this protection 240 V supply get converted into 24/12 V supply during short circuit so that shock doesn't occur.