Governor- :
Governor is a speed control system ,that acts on the turbine ,adjusting the inlet valves for the turbine.This is used to adjust the real power o/p from the generator or to regulate the frequency .Operation can adjust it's preset position for a direct change of real power o/p.
Exciter -:
Exciter is the unit that establishes DC current in the field winding .
AVR -:
AVR is a closed loop controller that fields control input of the exciter .
Real Power Control -:
Real power produced by the generator is approximately equal to the mechanical power received by the generator .
Governor is an inlet valve control mechanism activated through the opeartor . Real power o/p from a generator only be changed by adjusting the governor preset position.
Reactive power control -:
E - induced EMF phase voltage
Q- Reactive power
According to the expression of Q , we controll Q by adjusting induced emf E ,by adjusting induced emf E ,by adjusting excitation dc current (i)
Increase (i) to increase Q
Decrease (i) to decrease Q
change of (i) is activated via separate unit called AVR . This is closed loop voltage controlled adjustable preset .
If the reactive power of the busbar goes up , the terminal voltage is dropped .This drop is sensed by the AVR & send more (i) to the generator field . This boost up E & there by the reactive power generated in the process the terminal voltage (v) ,recovers it's drop & regains nominal value.
If we want to raise reactive power intentionally ; we should use preset input to raise internal emf E .
Monday, September 15, 2008
Sunday, September 14, 2008
FIRE ALARM SYSTEM
Fire alarm system consist of fire detectors ,manual call points ,Bells ,Fire alarm control panels ,Fire alarm cables .
There are 2 types of fire detectors ,smoke detectors & heat detectors . Also there are 2 kinds of smoke detectors which are ionisation detectors and light scattering detectors .From these 2 types light scattering type detectors are most probably used in construction industry .
Light Scattering smoke detector -:
According to the construction of detector it consist of light source ,reflector and photo cell. The light beam does not fall on to a photo electric cell at normally .When smoke enters the detector , some of the light beam is deflected upwards on to the photo electric cell. An electric current is thus produced which actuates the alarm .
Heat Detector -:
Heat detectors not active as smoke detectors . where the places heat detector use ,smoking is allowed .Some heat detectors have predetermine temperature ,when temperature goes above this predetermine value it's activated .Some heat detectors activate to rate of rise temperature .
Bi-metal coil detector is the popular detector for heat detectors among ELV engineers . In the bi-metal coil detector , heat from the fire passes through the cover to the bi-metal coils and the lower coils receives greater heat initially than the upper coil .The lower coil quickly makes contact with the upperv coil to complete the electricalcircuit and sound the alarm.
Manual call point -:
Manual call point use to awarw peoples about a fire .When fire occurs a person can press m.c.p & run away from fire .Due to this press bells start to ringing .
FAC (Fire Aclarm Control ) Panel -:
FAC panel comprise of software & hardware . FAC panel release signals according to the information it received by the detectors .If there are more than 1 FAC panel ,which are interconnected by network cards .FAC panel works 12v dc voltage .
Cables Used in Fire Alarm Systems -:
Fire cables consist with 2 covers for (+) & (-) and one sheath to obtain noise .The outer insulation layer is withstand to fire .
There are 2 types of fire detectors ,smoke detectors & heat detectors . Also there are 2 kinds of smoke detectors which are ionisation detectors and light scattering detectors .From these 2 types light scattering type detectors are most probably used in construction industry .
Light Scattering smoke detector -:
According to the construction of detector it consist of light source ,reflector and photo cell. The light beam does not fall on to a photo electric cell at normally .When smoke enters the detector , some of the light beam is deflected upwards on to the photo electric cell. An electric current is thus produced which actuates the alarm .
Heat Detector -:
Heat detectors not active as smoke detectors . where the places heat detector use ,smoking is allowed .Some heat detectors have predetermine temperature ,when temperature goes above this predetermine value it's activated .Some heat detectors activate to rate of rise temperature .
Bi-metal coil detector is the popular detector for heat detectors among ELV engineers . In the bi-metal coil detector , heat from the fire passes through the cover to the bi-metal coils and the lower coils receives greater heat initially than the upper coil .The lower coil quickly makes contact with the upperv coil to complete the electricalcircuit and sound the alarm.
Manual call point -:
Manual call point use to awarw peoples about a fire .When fire occurs a person can press m.c.p & run away from fire .Due to this press bells start to ringing .
FAC (Fire Aclarm Control ) Panel -:
FAC panel comprise of software & hardware . FAC panel release signals according to the information it received by the detectors .If there are more than 1 FAC panel ,which are interconnected by network cards .FAC panel works 12v dc voltage .
Cables Used in Fire Alarm Systems -:
Fire cables consist with 2 covers for (+) & (-) and one sheath to obtain noise .The outer insulation layer is withstand to fire .
Thursday, September 11, 2008
LIGHTING SYSTEM DESIGN
Lighting designs can be described under following sections ,
1) Interior lighting design
2) Outdoor lighting design
3) Emergency lighting design
Before design a lighting system ,required illuminance level is need to be considered .Illuminance level (Lux) is the level of light energy that are getting from a working plane .The required illuminance level of the working plane depends on the task which takes place in the particular area .
The reflectance from the ceiling ,wall and floor are important in lighting design calculations .Significance of the ceiling reflectance increase as the room area increases . White or near whiteis preferable.
Kind Of Lighting Sources -:
1) Tungstan filaments
2) Tungstan halogen filament
3) High pressure mercurt tungsten discharge (blended)
4)High pressure mercury discharge (fluorescent)
5)High perssure mercury discharge(metal halide)
6) Low pressure mercury discharge
7) High pressure sodium discharge
8)Low pressure sodium discharge
Colour of the light sources are categorise as warm , intermediate & cool.
Light fittings may be divided in to three categories
a) General utility fittings which are designed to give effective & economical illumination.
b) Special fittings usually with optical arrangements such as lenses or reflectance to give directional lights
c) Decorative fittings in which the light is there to be seen rather than to provide light to perform task
Lighting Calculation Equation -:
No of luminaries = (lux level required * area of room)/ (N* lumenous per lamp*UF*LF)
N= no of lamps for light fitting
UF= Utilization factor
Ha= height from worrking plane to light
MF= Maintanance factor
RI= room index = area/Ha(L+W)
L= length of room
H= height of room
Emergency Lighting-:
There are two kind of emergency lighting .Escape light & standby lighting . Escape lighting is safe exit for building occupants by providing appropriate visual conditions.Stand by lighting need to continue normal activity .
1) Interior lighting design
2) Outdoor lighting design
3) Emergency lighting design
Before design a lighting system ,required illuminance level is need to be considered .Illuminance level (Lux) is the level of light energy that are getting from a working plane .The required illuminance level of the working plane depends on the task which takes place in the particular area .
The reflectance from the ceiling ,wall and floor are important in lighting design calculations .Significance of the ceiling reflectance increase as the room area increases . White or near whiteis preferable.
Kind Of Lighting Sources -:
1) Tungstan filaments
2) Tungstan halogen filament
3) High pressure mercurt tungsten discharge (blended)
4)High pressure mercury discharge (fluorescent)
5)High perssure mercury discharge(metal halide)
6) Low pressure mercury discharge
7) High pressure sodium discharge
8)Low pressure sodium discharge
Colour of the light sources are categorise as warm , intermediate & cool.
Light fittings may be divided in to three categories
a) General utility fittings which are designed to give effective & economical illumination.
b) Special fittings usually with optical arrangements such as lenses or reflectance to give directional lights
c) Decorative fittings in which the light is there to be seen rather than to provide light to perform task
Lighting Calculation Equation -:
No of luminaries = (lux level required * area of room)/ (N* lumenous per lamp*UF*LF)
N= no of lamps for light fitting
UF= Utilization factor
Ha= height from worrking plane to light
MF= Maintanance factor
RI= room index = area/Ha(L+W)
L= length of room
H= height of room
Emergency Lighting-:
There are two kind of emergency lighting .Escape light & standby lighting . Escape lighting is safe exit for building occupants by providing appropriate visual conditions.Stand by lighting need to continue normal activity .
Monday, September 8, 2008
CABLES USED IN LOW VOLTAGE SYSTEMS
Mainly three types of cables used PVC/CU ; PVC/PVC/CU ; XLPE/PVC/CU . There are various conductor sizes for cables 1,1.5, 2.5,4,6,10,16,25,35,50,70,95,120,150,1`85, 240,300,400,500 ,630,800,1000 mm2 . When the cross section size of the cable is high , the current carrying capacity of the cable also go high . as well as the width of the insulation increased ,voltage drop propotionally decreased.For every cable there is a recommended voltage drop for per amp/ per meter (mv) .
Cables are usually equipped with cable ties and cable glands . Armoured cables use Cu/ Brass glands & non armoured cables use plastic glands for low cross section areas and Cu /Brass glands for relatively high cross section areas .
Cable laying methods -: 1) Perforated tray 2) Cable Trunking 3) Laying in trenches 4) Laying in conduits 5) Ladder support 6) Cable Ducts
Supporting metal work of the ladder support ,under the cable occupies less than 10% of the plain area. The perforated tray having not less than 30% of it's surface area removed by the perforation .Cable ties are used to lay cable in cable trays .
Cable Selection methods -:
Voltage Drop (Vd) calculation ; Vd =( L*I* Vt)/ 1000 :Vp>Vd
Vd - Actual voltage drop ; L - length of circuit ; I - The current to be carried out by the cable
Vp - Max permissible volt drop 4% of supply voltage in volts .
Procedure of selected cable :
1) Determine the design current of the circuit (lb)
2) Select the type of overload protective device (ln) : (ln > lb)
3) Select the type of cable & method of installation ; whether it is pvc/cu or pvc/pvc/cu or XLPE/pvc/cu or lay in duct ,tray ,ladder ,trench
4) Determine the rating factors ; ca,cg,ci,cf
5) Calculate the current for the circuit taking into account all correction factors
Ic=(In)/ (ca*cg*ci*cf)
6)Select the cable having current carrying capacity more than that It > Ic
7)Effective current carrying capacity of the cable ; Iz = It* ca*cg*ci*cf
cg - correction factor for grouping ca- correction factor for ambient temperature
ci- correction factor for thermal insulation cf- correction factor for protection device
Ic - Calculated current for circuit It - Tabulated single circuit carrying capacity of cable
Iz- Effective current capacity of a cable
Finally we consider about the It value and permissible voltage drop for select a cable .If the cable is non armoured , up to 16mm2 earth cable size is same as the size of main cable ,above 16mm2 earth cable size is half of nain cable.
Cables are usually equipped with cable ties and cable glands . Armoured cables use Cu/ Brass glands & non armoured cables use plastic glands for low cross section areas and Cu /Brass glands for relatively high cross section areas .
Cable laying methods -: 1) Perforated tray 2) Cable Trunking 3) Laying in trenches 4) Laying in conduits 5) Ladder support 6) Cable Ducts
Supporting metal work of the ladder support ,under the cable occupies less than 10% of the plain area. The perforated tray having not less than 30% of it's surface area removed by the perforation .Cable ties are used to lay cable in cable trays .
Cable Selection methods -:
Voltage Drop (Vd) calculation ; Vd =( L*I* Vt)/ 1000 :Vp>Vd
Vd - Actual voltage drop ; L - length of circuit ; I - The current to be carried out by the cable
Vp - Max permissible volt drop 4% of supply voltage in volts .
Procedure of selected cable :
1) Determine the design current of the circuit (lb)
2) Select the type of overload protective device (ln) : (ln > lb)
3) Select the type of cable & method of installation ; whether it is pvc/cu or pvc/pvc/cu or XLPE/pvc/cu or lay in duct ,tray ,ladder ,trench
4) Determine the rating factors ; ca,cg,ci,cf
5) Calculate the current for the circuit taking into account all correction factors
Ic=(In)/ (ca*cg*ci*cf)
6)Select the cable having current carrying capacity more than that It > Ic
7)Effective current carrying capacity of the cable ; Iz = It* ca*cg*ci*cf
cg - correction factor for grouping ca- correction factor for ambient temperature
ci- correction factor for thermal insulation cf- correction factor for protection device
Ic - Calculated current for circuit It - Tabulated single circuit carrying capacity of cable
Iz- Effective current capacity of a cable
Finally we consider about the It value and permissible voltage drop for select a cable .If the cable is non armoured , up to 16mm2 earth cable size is same as the size of main cable ,above 16mm2 earth cable size is half of nain cable.
Introduction
Building Construction is rapidly growing industry in the world . Electrical instalation is major part of it . Electrical installation consist of High voltage system , Low voltage system , Fire Alarm system , Lightning arrestor system , Closed Circuit Television System , Master Antena Television system , Public Address system , C - Bus System ,BMS System .
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