Visit Report Report on 500KV Grid Station Multan 11
Visit Report On 500KV Grid Station NTDCL Multan May 07th, 0!5 Submitted By Engr. Muhammad Ahmad (Executive Engineer)
Submitted By Muhammad Ikram 2K11-EE-!"# $a%a Sikandar 2K11-EE-!1& Shah%ad 'uain 2K11-EE-!## Muhammad uddamah 2K11-EE-!"*
E+ectrica+ Engineering ,eartment /0 Intitute Engineering 3 4e 4echn+gy Mu+tan
Visit Report Report on 500KV Grid Station Multan 11
OPENING In the name of ALLAH, The Most Benevolent, ever Merciful, All Praise be to ALLAH, Lord of the hole orld! Most Beneficent, ever Merciful, "in# of the $a% of &ud#ment, 'ou Alone e orshi( for, and to 'ou Alone e turn for Hel(! O) GO$, Guide us to the Path that is strai#ht! The Path of those, ho are blessed b% %ou, neither of those, ho have earned 'our An#er, nor of those ho have #one to astra%!
Visit Report Report on 500KV Grid Station Multan 11
OPENING In the name of ALLAH, The Most Benevolent, ever Merciful, All Praise be to ALLAH, Lord of the hole orld! Most Beneficent, ever Merciful, "in# of the $a% of &ud#ment, 'ou Alone e orshi( for, and to 'ou Alone e turn for Hel(! O) GO$, Guide us to the Path that is strai#ht! The Path of those, ho are blessed b% %ou, neither of those, ho have earned 'our An#er, nor of those ho have #one to astra%!
Visit Report Report on 500KV Grid Station Multan 11
P*E+AE once(ts we build by studying theory in classroom, - dim dimensi ension ons s while hile obser bservi ving ng analyzing the activities in real world. Practical inte intern rnsh shiip and and rese resea arch rch work ork on Techni hnical cal studies is an integral part of En#ineerin# (ro#ram! (ro#ram! To become an expert to understand all all conc concer erni ning ng issu issues es conc concer erni ning ng Ethi Ethics cs,, only only theoretical
knowledge
does not
provide
a
concre concrete te base. base. Resear Research ch work, work, report report writin writing, g, internship reports also considered a significant task along with theoretical knowledge therefore we were assigned a visit report on .//"0 Grid 1tation NT$L Multan, so that we gain a clear insight of the real world.
Visit Report on 500KV Grid Station Multan 11
Ac2noled#ement e are indebted to most respected Executive Engineer of protection En#r! Muhammad Ahmad, for his able guidance, motivation and cooperation that he expended to us during the visit program. e wish to express our deep and sincere appreciation and thankfulness to "n#r$ Muha%%ad &h%ad Executive Engineer !P"#$ for his able guidance, whenever we needed them, he was ready to help us by any means, indeed very kind and wonderful human.
ithout
his
continuous
help
and
encouragement, this visit " this report would surely not be able to take this present shape.
Visit Report on 500KV Grid Station Multan 11
List o' Contents O("N)NG$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ "RROR* R"+"R"NC" SORC" NOT +OND (R"+&C"$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ "RROR* R"+"R"NC" SORC" NOT +OND &CKNO-L"DG"M"NT$$$$$$$$$$$$"RROR* R"+"R"NC" SORC" NOT +OND L)ST O+ CONT"NTS$$$$$$$$$$$$$$$$ "RROR* R"+"R"NC" SORC" NOT +OND "."CT)V" SMM&R/$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$5 )NTRODCT)ON O+ NTDC $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ N&T)ON&L GR)D S/ST"M O+ (&K)ST&N $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$7 LOC&T)ON O+ 500KV GR)D ST&T)ON$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$1 S)NGL" L)N" D)&GR&M O+ 500KV G2ST&T)ON $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$!0 +NCT)ONS O+ GR)D ST&T)ON$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$!! T"C3N)C&L D&T& O+ GR)D ST&T)ON$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$!! "4)(M"NTS S"D )N 500KV G2ST&T)ON$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$!
Visit Report on 500KV Grid Station Multan 11
E5E064I7E S6MMA$8
An electrical grid station is an interconnection point between two transmission ring circuits, often between two geographic regions. They might have a transformer, depending on the possibly different voltages, so that the voltage levels can be adjusted as needed. Grid station regulates and controls the power between interconnected transmission lines to increase the reliability of the power system. It receive power from the power station at extremely high voltage and then convert these voltage to some low levels and supplied electric power to the sub stations or to other grid stations at the same voltage level according to the requirements. ational grid system of !a"istan contains an interconnected group of transmission lines in a ring system. It covers most of the power stations of the country in this single ring and supplied electric power to the different areas of the country. #ain function of the grid station is switching between the connected line stations and the load centers. This report comprises on the basics of the $%%&' grid station. It includes the functions and necessary information about the elements of the $%% &' grid station, T(), #ultan.
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atina+ 4ranmiin and ,iatch 0many (4,0)9 ational Transmission * (ispatch )ompany +T() -imited was incorporated on th ovember, /001 and commenced commercial operation on 23th (ecember, /001. It was organi4ed to ta"e over all the properties, rights and assets obligations and liabilities of 22% &' and $%%&' Grid 5tations and Transmission -ines6etwor" owned by !a"istan 7ater and !ower (evelopment Authority +7A!(A.The T() operates and maintains nine $%% &' Grid 5tations, 3/% "m of $%% &' transmission line and 3%%% "m of 22% &' transmission line in !a"istan.
:rid and the Sub Statin9 An electrical power substation is a conversion point between transmission level voltages +such as $%%&' and distribution level voltages +such as //&'. A substation has one or more step8down transformers and serves a regional area such as part of a city or neighborhood. 5ubstations are connected to each other
by the
transmission
ring circuit
system by equipments.
An electrical grid station is an interconnection point between two transmission ring circuits, often between two geographic regions. They might have a transformer, depending on the possibly different voltages, so that the voltage levels can be adjusted as needed.
The interconnected networ" of sub stations is called the grid, and may ultimately represent an entire multi8state region. In this configuration, loss of a small section, such as loss of a power station, does not impact the grid as a whole, nor does it impact the more locali4ed neighborhoods, as the grid simply shifts its power flow to compensate, giving the power station operator the opportunity to effect repairs without having a blac"out.
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atina+ :rid Sytem akitan9
9lectricity is generated at a voltage level of // &' at the largest hydral power station +Tarbela of the !a"istan and it steps up to the voltage level of up to $%% &' by using a unit transformer. A complex distributed networ" of $%% &' transmission lines are present in the !a"istan +from !eshawar to &arachi, the output of the unit transformer is given to these lines which then supplied this power to all of the country with the help of their interconnected networ" of transmission
and distribution lines. In summer season, ice is reached in the Tarbela and
#angla:s reservoirs after melting from northern areas. 5o in this season there is enough water for the production of required electrical power and the generated electrical power is travel from Tarbela to &arachi side. ;ut in winter season, situation is opposite to the above. 7ater is not enough to produce a required power, so the capacity of Tarbela station is somewhat reduced and to compensate this reduced energy, the flow of electric power through the interconnected networ" is changes its direction toward Tarbela from &arachi instead towards &arachi. There is many station in our country but we consider only those have voltage level in between 22% and $%% &'. In ational grid system of !a"istan, several power stations are connected in a ring system and they supplied electric power to different areas of the country under the supervision of 7A!(A. All stations are transmitting their produced power to transmission line and from the ring main system< all regional grids supplied power to their own areas. ;y connecting several power stations into a single ring system, the system stability is increased. Advantage the :rid Sytem
Any time electricity is available for the consumers at lower cost. =low of electrical energy is continuous and sure. It is possible to fulfill the emergency demand of power. ;etter regulation of the voltages. Improved power factor It is possible to govern the generator according to the load. 5afe transmission system.
Visit Report on 500KV Grid Station Multan 11
>educed fault timings. )ontrolled frequency range.
,iadvantage the :rid Sytem
)ost of the control system is increased and their maintenance is complicated. !ower system is affected from the environmental factors. This system is unsafe during the war. 9xtended system is going to complexity. (ue to the expensive equipments, additional load occurred on the consumers. (uring short circuit condition it is impossible to maintain the continuity of power. ?igh initial and maintenance cost. (uring load shedding, capacity of industries connected with the grid is reduced which
cause to industrial development problem. =or maintenance, qualified staff is required and for that reason our country has to spend
more money to call expert engineers from other countries.
Visit Report on 500KV Grid Station Multan 11
;catin the Intercnnected "** K7 :rid Statin akitan
Visit Report on 500KV Grid Station Multan 11
Sing+e ;ine ,iagram "**K7 :rid Statin e< Mu+tan
Visit Report on 500KV Grid Station Multan 11
/unctin a :rid Statin9 A Grid 5tation has the following functions@
/ 8 5upply of required electrical power. 2 8 #aximum possible coverage of the supply networ". 8 #aximum security of supply. 3 8 5hortest possible fault8duration. $ 8 Bptimum efficiency of plants and the networ". 8 5upply of electrical power within targeted frequency limits, +30.$ ?4 and $%.$ ?4. C 8 5upply of electrical power within specified voltage limits. 1 8 5upply of electrical energy to the consumers at the lowest cost.
4echnica+ data the "** K7=22*K7 grid tatin> 4,0> Mu+tan9
:rid inut The $%%&' grid station, T() #ultan receives power at the voltage level of $%% &' from the following generating stations. The data of the Transmission lines with length * date of commissioning is as following.
Sr %/ %2 % %3 %$ %
ame 4= ;ine #ultan8Guddu %/ #ultan8Guddu % #ultan8 #6 Garh #ultan8 Dousaf 7ala #ultan8 Gatti #ultan8 >oush
Guddu !ower station +2 )ircuit
;ength (KM) /2 / . /2 222 2
,ate Energi%ing 2/8%$8/00/ %18%/8/00/ /%8%82%%% %38%$82%%/ 218%8/00$ 238%28/001
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#u4affar Garh power 5tation +/ )ircuit
>ousch !ower 5tation +/ )ircuit
Gatti Grid 5tation +/ )ircuit
Dousafwala Grid 5tation +/ )ircuit
4ranmiin :rid Exit (22*K7) The $%%&' grid station, T() #ultan has delivers6receive power at a voltage level of 22%&' to or from the following stations@ The data regarding 22%&' transmission lines is given below.
Sr %/ %2 % %3 %$ % %C %1 %0 /% // /2 / /3
ame 4= ;ine #ultan8 56 >oad %/ #ultan8 56 >oad %2 #ultan8 G!5 %/ #ultan8 G!5 %2 #ultan8 #6 Garh %2 #ultan8 #6 Garh % #ultan8 #6 Garh %/ #ultan8 #6 Garh %3 #ultan8 &A!)B % #ultan8 &A!)B %3 #ultan8 &A!)B % #ultan8 &A!)B %$ #ultan8 'ehari %/ #ultan8 'ehari %2
&ot Addu !ower 5tation +3 )ircuit
#u4affar Garh power 5tation +3 )ircuit
'ehari 5ubstation +2 )ircuit
.G.!.5 #ultan +2 )ircuit
;ength (KM) /11 /11 /3 /3 $ $ $% $% /%2 /%2 /%2 /%2 C0 C0
,ate Energi%ing /28/%82%/ /28/%82%/ %/8%C8/00/ %C8%C8/00/ %C8%C8/00/ %28%/8/00$ /28%$8/00$ 2$8/28/011 /%8/28/010 %/8/28/010 /%8%28/001 208%8/011 2/8%82%%1 2/8%82%%1
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ishatabad +2 )ircuit
E?uiment ued in "** K7 :rid Statin
Shunt $eactr9
Transmission cables have much higher capacitance to earth than overhead lines. -ong transmission lines for system voltages of /2 &' and more need shunt reactors. The same
Visit Report on 500KV Grid Multan voltage rise when a high load suddenly goes for large urban networ"s to Station prevent excessive 11 falls out due to a failure. 5hunt reactors contain the same components as power transformers, li"e windings, core, tan", bushings and insulating oil and are suitable for manufacturing in transformer factories. The main difference is the reactor core limbs, which have non8magnetic gaps inserted between pac"ets of core steel.
To stabili4e the line voltage the line inductance can be compensated by means of series capacitors and the line capacitance to earth by shunt reactors. 5eries capacitors are placed at different places along the line while shunt reactors are often installed in the stations at the ends of line. In this way, the voltage difference between the ends of the line is reduced both in amplitude and in phase angle. In this situation, the capacitance to earth draws a current through the line, which may be capacitive. 7hen a capacitive current flows through the line inductance there will be a voltage rise along the line.
8phase reactors can also be made. These may have 8 or 8$8limbed cores. In a 8limbed core there is strong magnetic coupling between the three phases, while in a $8limbed core the phases are magnetically independent due to the enclosing magnetic frame formed by the two yo"es and the two unwound side8limbs. The neutral of shunt reactor may be directly earthed, earthed through an 9arthing8reactor or unearthed.
7hen the reactor neutral is directly earthed, the winding are normally designed with graded insulation in the earthed end. The main terminal is at the middle of the limb height, * the winding consists of two parallel8connected halves, one below * one above the main terminal. The insulation distance to the yo"es can then be made relatively small. 5ometimes a small extra winding for local electricity supply is inserted between the main winding * yo"e.
Visit Report on 500KV Grid Station Multan 11 Shunt reactr carry ut dierent tye tak9
They compensate the capacitive reactive power of the transmission cables, in particular in networ"s with only light loads or no load.
They reduce system8frequency overvoltage when a sudden load drop occurs or there is no load.
They improve the stability and efficiency of the energy transmission.
protection and tele8monitoring between electrical substations through power lines at high voltage, such as //% "', 22% "', and 3%% "'. !-)) integrates the transmission of communication signal and $%6% ?4 power signal through the same electric power cable. The major benefit is the union of two important applications in a single system. In a !-)) system the communication is established through the power line. The audio frequency is carried by a carrier frequency and the range of carrier frequency is from $% "?4 to $%% "?4. The modulation generally used in this system is amplitude modulation. The carrier frequency range is allocated to include the audio signal, protection and the pilot frequency. The pilot frequency is a signal in the audio range that is transmitted continuously for failure detection. The voice signal is converted6 compressed into the %% ?4 to 3%%% ?4 range, and this audio frequency is mixed with the carrier frequency. The carrier frequency is again filtered, amplified and transmitted. The transmission of these ?= carrier frequencies will be in the range of % to E2db. This range is set according to the distance between substations. !-)) can be used for interconnecting !;Fs. The electricity board in India has an internal networ" !-)) between !;Fs.
Visit Report on 500KV Grid Station Multan 11 4he ure ;0 +ine tra
!rovision of defined high voltage line impedances regardless of the configuration of the primary
system switchgear. !revention of signal losses due to propagation into other lines. Attenuation of >= signals from other parts of the power system, thus permitting multiple uses of
the same frequency bands. !-) line traps are connected in series with the high8tension lines and must therefore be rated for the maximum continuous load current and be able to withstand the maxi8 mum fault current at the
place of Installation. (-T) line traps fulfill all the >= requirements as well as all the power system requirements of the latest I9) and A5I recommendations.
0aacitance 0u+ed 7+tage 4ranrmer (0074)9 A capacitor voltage transformer +)'T, or capacitance coupled voltage transformer +))'T is a transformer used in power systems to step down extra high voltage signals and provide a low voltage signal, for measurement or to operate a protective relay. In its most basic form the device consists of three parts two capacitors across which the transmission line signal is split, an inductive element to tune the device to the line frequency, and transformer to isolate and further step down the voltage for the instrumentation or protective relay. The device has at least four terminals a terminal for connection to the high voltage signal, a ground terminal, and two secondary terminals which connect to the instrumentation or protective relay. )'Ts are typically single8phase devices used for measuring voltages in excess of one hundred "ilovolts where the use of voltage transformers would be uneconomical. In practice, capacitor )/ is often constructed as a stac" of smaller capacitors connected in series. This provides a large voltage drop across )/ and a relatively small voltage drop across )2. The )'T is also useful in communication systems. )'Ts in combination with wave traps are used for filtering high frequency communication signals from power frequency. This forms a carrier communication networ" throughout the transmission networ".
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0aacitance 0u+ed 7+tage 4ranrmer
Surge Arreter9 9ach piece of electrical equipment in an electrical system needs to be protected from voltage
surges.
To
prevent
damage
to electrical equipment, surge protection
considerations are paramount to a well8 designed electrical system. #odern metal oxide arresters provide exceptional overvoltage protection of equipment connected to the power system. The proper selection and application of the arrester, however, involves decisions in several areas, which will be discussed in the paper. The original lightning arrester was nothing more than a spar" air gap with one side connected to a line conductor and the other side connected to earth ground. 7hen the line8to8ground voltage reached the spar"8over level, the voltage surge would be discharged to earth or ground.
The
modern metal
oxide
arrester
provides both excellent
protective
characteristics and temporary overvoltage capability. The metal oxide dis"s maintain a stable characteristic and sufficient non8linearity and do not require series gaps. (ue to the broad nature of this subject, this paper will concentrate on the application of the gapless metal oxide arrester to circuits and systems rated /%%% ' and greater.
A lightning arrester is a device used on electrical power systems to protect the insulation on the system from the damaging effect of lightning. #etal oxide varistors +#B's have been used for power system protection since the mid /0C%s. The typical lightning arrester also "nown
Visit Report on 500KV Grid Station Multan 11 as surge arrester has a high voltage terminal and a ground terminal. 7hen a lightning surge or switching surge travels down the power system to the arrester, the current from the surge is diverted around the protected insulation in most c ases to earth.
0ircuit Breaker9 A circuit brea"er is an automatically8operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow. Hnli"e a fuse, which operates once and then has to be replaced, a circuit brea"er can be reset +either manually or automatically to resume normal operation. )ircuit brea"ers are made in varying si4es,
from
small
devices
that
protect
an
individual
household
appliance
large switchgear designed to protect high voltage circuits feeding an entire city.
up
to
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@eratin All circuit brea"ers have common features in their operation, although details vary substantially depending on the voltage class, current rating and type of the circuit brea"er. The circuit brea"er must detect a fault condition< in low8voltage circuit brea"ers this is usually done within the brea"er enclosure. )ircuit brea"ers for large currents or high voltages are usually arranged with pilot devices to sense a fault current and to operate the trip opening mechanism. The trip solenoid that releases the latch is usually energi4ed by a separate battery, although some high8voltage circuit brea"ers are self8contained with current transformers, protection relays, and an internal control power source. Bnce a fault is detected, contacts within the circuit brea"er must open to interrupt the circuit< some mechanically8stored energy +using something such as springs or compressed air contained within the brea"er is used to separate the contacts, although some of the energy required may be obtained from the fault current itself. 5mall circuit brea"ers may be manually operated< larger units have solenoids to trip the mechanism, and electric motors to restore energy to the springs. The circuit brea"er contacts must carry the load current without excessive heating, and must also withstand the heat of the arc produced when interrupting the circuit. )ontacts are made of copper or copper alloys, silver alloys, and other materials. 5ervice life of the contacts is limited by the erosion due to interrupting the arc. #iniature and molded case circuit brea"ers are usually discarded when the contacts are worn, but power circuit brea"ers and high8voltage circuit brea"ers have replaceable contacts. 7hen a current is interrupted, an arc is generated. This arc must be contained, cooled, and extinguished in a controlled way, so that the gap between the contacts can again withstand the voltage in the circuit. (ifferent circuit brea"ers use vacuum, air, insulating gas, or oil as the medium in which the arc forms. (ifferent techniques are used to extinguish the arc including
-engthening of the arc
Intensive cooling +in jet chambers
(ivision into partial arcs
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ero point quenching +)ontacts open at the 4ero current time crossing of the A) waveform, effectively brea"ing no load current at the time of opening. The 4ero crossing occurs at twice the line frequency i.e. /%% times per second for $%?4 and /2% times per second for %?4 A)
)onnecting capacitors in parallel with contacts in () circuits
=inally, once the fault condition has been cleared, the contacts must again be closed to restore power to the interrupted circuit. Arc interruption
)ircuit brea"ers are usually able to terminate all current very quic"ly typically the arc is extinguished between % ms and /$% ms after the mechanism has been tripped, depending upon age and construction of the device.
'igh-v+tage circuit breaker
9lectrical power transmission networ"s are protected and controlled by high8voltage brea"ers. The definition of high voltage varies but in power transmission wor" is usually thought to be C2.$ "' or higher, according to a recent definition by the International 9lectro technical )ommission +I9). ?igh8voltage brea"ers are nearly always solenoid8operated, with current sensing protective operated through current transformers. In substations the protective relay scheme can be complex, protecting equipment and busses from various types of overload or ground6earth fault. ?igh8voltage brea"ers are broadly classified by the medium u sed to extinguish the arc.
;ul" oil
#inimum oil
Air blast
'acuum
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5=
Some of the manufacturers are A;;, G9 +General 9lectric , A>9'A, #itsubishi 9lectric,
!ennsylvania ;rea"er, 5iemens, Toshiba, ;?9- and )G-. (ue to environmental and cost concerns over insulating oil spills, most new brea"ers use 5= gas to quench the arc. )ircuit brea"ers can be classified as live mechanism is at line potential, or dead
tank ,
where the enclosure that contains the brea"ing
tank with
the enclosure at earth potential. ?igh8voltage
A) circuit brea"ers are routinely available with ratings up to C$ "'. /2%%&' brea"ers are li"ely to come into mar"et very soon. ?igh8voltage circuit brea"ers used on transmission systems may be arranged to allow a single pole of a three8phase line to trip, instead of tripping all three poles< for some classes of faults this improves the system stability and availability.
Su+ur hexa+uride (S/ &) high-v+tage circuit-breaker
A sulfur hexafluoride circuit brea"er uses contacts surrounded by sulfur hexafluoride gas to quench the arc. They are most often used for transmission8level voltages and may be incorporated into compact gas8insulated switchgear. In cold climates, supplemental heating or de8rating of the circuit brea"ers may be required due to liquefaction of the 5= gas.
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Air +ant Sytem9 (uring repairing of different elements of grid station, air plant system is used. Air plant system m contains a small si4e cylinder in which the air is stored after compression by the small si4e compressor. (uring maintenance and routine cleaning of the different elements, compressed air is through on the external surface of the particular element.
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I+atr S
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0urrent 4ranrmer9
In electrical engineering, a current transformer +)T is used for measurement of electric currents. )urrent transformers, together with voltage transformers +'T +potential transformers +!T, are "nown as instrument transformers. 7hen current in a circuit is too high to directly apply to measuring instruments, a current transformer produces a reduced current accurately proportional to the current in the circuit, which can be conveniently connected to measuring and recording instruments. A current transformer also isolates the measuring instruments from what may be very high voltage in the monitored circuit. )urrent transformers are commonly used in metering and protective relays in the electrical power industry.
The )T is typically described by its current ratio from primary to secondary. Bften, multiple )Ts are installed as a Jstac"J for various uses. =or example, protection devices and revenue metering may use separate )Ts to provide isolation between metering and protection circuits, and allows current transformers with different characteristics +accuracy, overload performance to be used for the different purposes.
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4ranrmer A transformer is a device that transfers electrical energy from one circuit to another circuit through inductively conductorsKthe transformerLs coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformerLs core and thus a varying field through the secondary winding. This varying magnetic field induces a varying electromotive force +9#= or JvoltageJ in the secondary winding. This effect is called mutual induction.
If a load is connected to the secondary, an electric current will flow in the secondary winding and electrical energy will be transferred from the primary circuit through the transformer to the load. In an ideal transformer, the induced voltage in the secondary winding +'s is in proportion to the primary voltage +'p, and is given by the ratio of the number of turns in the secondary +s to the number of turns in the primary +p as follows
Visit Report on 500KV Grid Station Multan 11 ;y appropriate selection of the ratio of turns, a transformer thus allows an alternating current +A)voltage to be Jstepped upJ by ma"ing s greater than p, or Jstepped downJ by ma"ing s less than p. In the vast majority of transformers, the windings are coils wound around a ferromagnetic core, air8core transformers being a notable exception. Transformers range in si4e from a thumbnail8si4ed coupling transformer hidden inside a stage microphone to huge units weighing hundreds of tons used to interconnect portions of power grids. All operate with the same basic principles, although the range of designs is wide. 7hile new technologies have eliminated the need for transformers in some electronic circuits, transformers are still found in nearly all electronic devices designed for household +JmainsJ voltage. Transformers are essential for high voltage power transmission, which ma"es long distance transmission economically practical.
Baic rinci+e The transformer is based on two principles first, that an electric current can produce a magnetic field +electromagnetism, and, second that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil +electromagnetic induction. )hanging the current in the primary coil changes the magnetic flux that is developed. The changing magnetic flux induces a voltage in the secondary coil.
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0+aiicatin Transformers can be classified in many different ways< list is
;y power capacity
from a fraction of a volt8ampere +'A to over a thousand #'A<
;y frequency range power8, audio8, or radio frequency<
;y voltage class
from a few volts to hundreds of "ilovolts<
;y cooling type
air8cooled, oil8filled, fan8cooled, or water8cooled etc@
;y application
such as power supply, impedance matching, output voltage and
current stabili4er, or circuit isolation<
;y purpose
distribution, rectifier , arc furnace, amplifier output, etc.<
;y winding turns ratio
step8up, step8down, isolating with equal or near8equal
ratio, variable, and multiple windings.
;y 5upply 5ingle and three !hase transformers.
;y special application current and 'oltage transformer.
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Aut 4ranrmer9 The auto transformer is being used in $%%&'6 22%&' grid station.
/ire rtectin Sytem9 =ire protection system is used in the electrical grid station to overcome the fire produced by any cause, so the equipments will wor" under the safe condition and the chances of burning of the electrical and other equipments used in the grid station is reduced. 7hen the fire is produced by any electrical or environmental reason, fire protection system will enables to control the
Visit Report on 500KV Grid Station Multan 11 produced fire. (ifferent methods are used to ma"e combustion impossible in the grid station, but in $%% &' grid station, T(), #ultan, water is primarily used in the fire protection system.
ature /ire
Three essentials are needed for the fire
=uel
Bxygen
?eat To bring fuel to its ignition point
0+aiicatin /ire
=our classes of fires are@
)lass A !aper, wood, textiles and rubbish
)lass ; -iquids such as alcohol, oil and grease
)lass ) 9lectrical
)lass ( Bccur in certain metals li"e magnesium, sodium, potassium and titanium.
rinci+e Extinguihing /ire
)ool the fuel below its ignition point
>emove the oxygen supply
5eparate the fuel from the oxygen
Extinguihing Agent
)lass A
Visit Report on 500KV Grid Station Multan 11 >espond best to water or water type which lower the fuel below its ignition point.
)lass ; >espond to carbon dioxide, halogenated hydrocarbons, and dry chemicals, all of which displace the oxygen supply ma"ing combustion impossible.
rtective $e+ay9
A relay is a device that MdetectsN the fault and MdirectsN the circuit brea"er to isolate the faulty part6equipment from the system.
/unctin $e+ay
A relay performs three functions.
5ensing.
)omparing.
Visit Report on 500KV Grid Station Multan 11
Tripping.
It senses the MfaultN. This is done by the relay to MrespondN to the change if any, in the
currents passing through it. It compares the current through it with the designed value of current. It responds only if the
current through it is different from its designed current rating. If the current through it is different from its designed current rating, it sends information to
the circuit brea"er for tripping.
ua+itie a :d $e+ay
In order to perform its function successfully, a relay should have the following qualities.
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5electivity.
5peed.
5ensitivity
>eliability
5implicity.
9conomical
$e+ay A+icatin
Ground fault
!hase fault
;us protection
Transformer protection
Transmission -ine protection
Auxiliary
Bu Bar and Bu 0u+er9 In electrical power distribution, a bus bar is a thic" strip of copper or aluminum that conducts electricity within a switchboard, distribution board, substation or other electrical apparatus. ;us bars are used to carry very large currents, or to distribute current to multiple devices within switchgear or equipment. =or example, a household circuit brea"er panel board will have bus bars at the bac", arranged for the connection of multiple branch circuit brea"ers. An aluminum smelter will have very large bus bars used to carry tens of thousands of amperes to the electrochemical cells that produce aluminum from molten salts.
7hen a number of generators or feeders operating at the same voltage have to be directly connected electrically, bus bars are used as the common electrical component. The si4e of the bus bar is important in determining the maximum amount of current that can be safely carried. ;us
Visit Report on 500KV Grid Station Multan 11 bars can have a cross8sectional area of as little as /% mmO but electrical substations may use metal tubes of $% mm in diameter +/,0 mmO or more as bus bars.
A bus bar may either be supported on insulators, or else insulation may completely surround it. ;us bars are protected from accidental contact either by a metal earthed enclosure or by elevation out of normal reach. eutral bus bars may also be insulated. 9arth bus bars are typically bolted directly onto any metal chassis of their enclosure. ;us bars may be enclosed in a metal housing, in the form of bus duct or bus way, segregated8phase bus, or isolated8phase bus. ;us bars may be connected to each other and to electrical apparatus by bolted or clamp connections. Bften joints between high8current bus sections have matching surfaces that are silver8plated to reduce the contact resistance. At extra8high voltages +more than %% "' in outdoor buses, corona around the connections becomes a source of radio8frequency interference and power loss, so connection fittings designed for these voltages are used. =ollowing bus bar schemes are used in the field of electrical power system@
5ingle bus bar scheme
5ectionali4ing bus bar scheme
(ouble bus bar scheme
Terminal section scheme
#ain and transfer bus scheme
>ing bus scheme
,ub+e Bubar Scheme
In $%%&' grid station, the double bus bar and one * half circuit brea"er scheme is being used. The following diagrams are double bus bar and one * half circuit brea"er scheme.
Visit Report on 500KV Grid Station Multan 11
Visit Report on 500KV Grid Station Multan 11
Inu+atr9 #aterials that do not have any free electrons. ;ecause of this fact, they do not tend to share their electrons very easily and do not ma"e good conductors of electrical currents.
9lectrical insulation is the absence of electrical conduction. 9lectronic band theory +a branch of physics says that a charge will flow if states are available into which electrons can be excited. This allows electrons to gain energy and thereby move through a conductor such as a metal. If no such states are available, the material is an insulator. #ost insulators have a large band gap. This occurs because the JvalenceJ band containing the highest energy electrons is full, and a large energy gap separates this band from the next band above it. There is always some voltage +called the brea"down voltage that will give the electrons enough energy to be excited into this band. Bnce this voltage is exceeded, the material ceases being an insulator, and charge will begin to pass through it. ?owever, it is usually accompanied by physical or chemical changes that permanently degrade the materialLs insulating properties.
#aterials that lac" electron conduction are insulators if they lac" other mobile charges as well. =or example, if a liquid or gas contains ions, then the ions can be made to flow as an electric current, and the material is a conductor. 9lectrolytes and plasmas contain ions and will act as conductors whether or not electron flow is involved.
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Insulators suffer from the phenomenon of electrical brea"down. 7hen the electric field applied across an insulating substance exceeds in any location the threshold brea"down field for that substance, which is proportional to the band gap energy, the insulator suddenly turns into a resistor, sometimes with catastrophic results. (uring electrical brea"down, any free charge carrier being accelerated by the strong electric field will have enough velocity to "noc" electrons from +ioni4e any atom it stri"es. These freed electrons and ions are in turn accelerated and stri"e other atoms, creating more charge carriers, in a chain reaction. >apidly the insulator becomes filled with mobile carriers, and its resistance drops to a low level. In air, J corona dischargeJ is normal current near a high8voltage conductor< an JarcJ is an unusual and undesired current. 5imilar brea"down can occur within any insulator, even within the bul" solid of a material. 9ven a vacuum can suffer a sort of brea"down, but in this case the brea"down or vacuum arc involves charges ejected from the surface of metal electrodes rather than produced by the vacuum itself. (ifferent types of insulators are being used in the power transmission system and in the grid stations. In grid stations, at extra high voltage, the bushing type insulators are mostly used.
S
There can also be controls for the supply of electricity to the switchboard, coming from a generator or ban" of electrical generators, especially frequency control of A) power and load sharing controls, plus gauges showing frequency and perhaps a synchroscope. The amount of power going into a switchboard must always equal to the power going out to the loads. Inside the switchboard there is a ban" of bus bars 8 generally wide strips of copper to which the switchgear is connected. These act to allow the flow of large currents through the switchboard, and are generally bare and supported by insulators.
Visit Report on 500KV Grid Station Multan 11 A control room is a room serving as an operations centre where a facility or service can be monitored and controlled. A control room can, at times, be designated as an area of refuge, particularly in high ris" facilities, such as a nuclear power station or a petrochemical facility, as an accidental fire can have severe repercussions to the surrounding environment. As is typical for all areas of refuge, occupants must be provided with guaranteed life support and guarantee of functionality of the items they are intended to control for the anticipated design8basis fire event. It is not unusual to provide control rooms with gaseous fire suppression systems to safeguard its contents and occupants.
The primary equipment in control rooms is housed in multi8function cabinets. 5ince the control equipment is intended to control other items in the surrounding facility, it follows that these +often fire8resistance rated service rooms require many penetrations. (ue to routine equipment updates, penetrates, such as cables are subject to frequent changes. It follows that an operating control
room
maintenance
program
must
include
vigilant fire
stop maintenance
for code compliance and for gaseous fire suppression systems to wor" as well. (ue to the nature of the sensitive equipment inside control room cabinets, it is useful to ensure the use of JT8
