1. THE YARD
2. LIGHTINING ARRESTOR
3. WAVE TRAP
5. INSTRUMENT TRANSFORMER
6. POTENTIAL TRANSFORMER
7. CURRENT TRANSFORMER
8. POWER TRANSFORMER
10 CIRCUIT BREAKER
12. POWER LINE CARRIER COMMUNICATION
13. PROTECTION RELAY
14. CONTROL ROOM
15. BATTERY ROOM
This is my first practical training which has taken at 220 KV GSS, Bharatpur
I would like to express my sincere thanks to Mr. M.M. SINGH, Who have given his excellent guidance and shared his experience with me using entire course of this training report.
We are thanks to other staff member which are guided me. Finally I would like to say this summer training has been a valuable part in my life.
At last but not least I am thankful to the all the staff member of “RAJASTHAN INSTITUTE OF ENGINEERING & TECHNOLOGY”, department of Electrical & Electronics Engineering.
Pawan Kumar Gupta
B.TECH. IV YEAR (EEE)
This is training of 30 days my training place was 220 KV ,GSS, Bharatpur(rajasthan). GSS is the mean of connection between generating station and consumer by providing safety and reliability of system in case of default.
This sub station step down the incoming voltage power transmission to the required valve and then is supplied to the consumer feeder or GSS done by connecting auto transformer operation and requirement of various equipment have been include in detail , further in case of report is the bus bar.
Arrangement of different feeder level and switch yards included information of bus bar arrangement of different level isolator and growing substation also power transformer circuit breaker oil, filtration plant, and compression protection control room and place are leveled.
When India becomes independent its overall installed capacity was hardly 1900 mw. During first year plan (1951-1956) this capacity was only 2300 mw. The contribution of Rajasthan state was negligible during 1&2 year plans the emphases was on industrialization for that end it was considered to make the system of the country reliable. Therefore Rajasthan state electricity board came into existence in July 1957.
In India electrical power is generated at a voltage of 11KV to 33 KV . which is taken stepped up to the transmission level in the range of 66 KV to 400 KV
Member of transmission and switching have to be created. These are known as “SUB STATION”.
Along these transmission lines secondary substation are created where voltage is further stepped down to sub transmission and primary distribution voltage.
A substation is an assembly of apparatus, which transform the characteristics of electrical energy from one form to another say from one voltage level to another level. Hence a substation is an intermediate link between the generating station and consumer.
For economic transmission the voltage should be high so it is necessary to step up the generated voltage for transmission and step down transmitted voltage for distribution. For this purpose substations are installed. The normal voltages for transmission are 400kv, 220kv, 132kv and for distribution 33kv, 11kv etc.
Electricity boards are setup in all states of India which are responsible for
They also construct, install and maintain all the station made for these purpose. In Rajasthan ,R.R.V.P.N.L. is responsible for transmission and distribution of electrical power all over Rajasthan. It has its own generating station and it’s also gets power from various other stations also. It gets power from following stations:-
1. Badarpur Thermal Power Station Delhi
2. Bhakara Nangl Project (at satlaj in Punjab)
3. Gandhi Sagar Dam Kota
4. Jawahar Dam Kota
5. Rana Pratap Sagar Dam Kota
6. Rajasthan Atomic Power Plant (RAPP) Kota
7. Kota Super Thermal Power Station (KSTPS) Kota
8. Anta Gas Power Plant Anta
9. Rajasthan share in Bhakara Beas Management Board (BBMB)
Power obtain from these stations is transmitted all over Rajasthan with the help of grid stations. Depending on the purpose, substations may be classified as:-
1. Step up substation
2. Primary grid substation
3. Secondary substation
4. Distribution substation
5. Bulky supply and industrial substation
6. Mining substation
7. Mobile substation
8. Cinematograph substation
Depending on constructional feature substation are classified as:-
1. Outdoor type
2. Indoor type
3. Basement or Underground type
4. Pole mounting open or kilos type
Any substation has many types of civil and electrical works. Main compo nents are:-
· Bus bar
· Power transformers
· Circuit breaker
· Lightening arrester
· Instrument transformers
The control room is equipped with protective relays, ammeters, voltmeters, energy meters and frequency and power factor meters
D.C. supply is heart of GSS batteries are used for this purpose. They have separate charging circuit also. For communication purpose P.L.C.C. is used which has its various components.
220 KV GSS, Bharatpur is the part of the transmission system.
· 220 KV Dausa-Bharatpur,
· 220 KV Agra –Bharatpur,
· 220 KV Dholpur-Bharatpur,
· 220 KV D.C.C.P.P. -Bharatpur
· 132 K.V.
3. Nadbai 1st
4. Nadbai 2nd
· 33 K.V.
· 11 K.V.
2. Reeco 1st
3. Reeco 2nd
The yard is spread in very long area. The yard of 220 KV GSS at Bharatpur has various equipment installed at the yard of 220 KV GSS, Bharatpur are:-
· Lighting Arrester
· Wave Trap
· Current Transformer
· Circuit Breaker
· Bus Bars
· Power Transformer
· Potential Transformer
· Static earthling system
· PLCC equipment including coupling capacitance
Figure-2.1 Switch Yard
BUS BAR SYSTEM
This bus bar arrangement is very useful for working purpose as every GSS. It is a conductor to which a number of cut .Are connected in 220 KV GSS there are two bus running parallel to the each other, one is main and another is auxiliary bus is only for stand by, in case of failure of one we can keep the supply continues.
If more loads are coming at the GSS then we can disconnect any feeder through circuit breaker which is connected to the bus bar. This remaining all the feeders will be in running position .if we want to work with any human damage. In this case all the feeders will be on conditions.
According to bus voltage the material is used .Al is used because of the property & features and it is cheap.
With the help of bus bar arrangement we can connect all the incoming supply which is coming from different higher order GSS.
1. Electricity resistively at 20 c
2. Temp coff. Of resistively
3. Softening tem.
4. Thermal conductivity
5. Meting point
Lightening arrester is first equipment of GSS. It is protecting all the equipment against the HV. The ground wire or earthing does not provide protection against the high voltage waves reaching the terminal equipment .so some protective device is necessary to produce power station ,sub-station and transmission lines against the high voltage wave reaching here. Which is connected between line and earth it acts as a safty valve. .
Through the surge impedence of line limits the amplitude of the line to earth over voltage to a value which wills safe guard the insulation of the protected equipment.
An ideal L.A should have following characteristics:-
1. It should not take any current under normal condition .i.e. its spark over voltage must be higher then the system voltage.
2. Any abnormal transient voltage above the break down voltage must caused it to break as quick as possible in order to provide an alternate path to earth.
3. It must be able to carry the resultant discharge current without causing damage to itself.
For high voltage system the thirties type L.A are used .The value type is also known as non linear diverter .These arrester consist of a spark gape and a non linear resistance. Both resistance and spark gape are accommodated in series with a completely light porcelain condition humidity etc.
They include a number of identical elements connected in series .Each element consist of with pre ionization device between each grounding resistance of high ohmic value connected in parallel.
3.3 NON LINEAR RESISTER:-
The resister disc comprises inorganic material having a silicon carbide base in a clay board. These discs form a block. The ohmic value of which decreases rapidly when the applied voltage and current increases as soon as the current wave resulting from the over voltage has been discharged. The resister block subjected to the sole. Alternating Voltage and resistance assumes great value .So that the amplitude of the resulting current becomes zero.
Figure-3.1 Lighting Arresters
It is used to trap the communication signals & send PLCC room through CVT.
Rejection filters are known as the line traps consisting of a parallel resonant circuit ( L and C in parallel) tuned to the carrier frequency are connected in series at each and of the protected line such a circuit offer high impedance to the flow of carrier frequency current thus preventing the dissipation. The carrier current used for PLC Communication have to be prevented from entering the power equipments such as attenuation or even complete loss of communication signals. For this purpose wave trap or line trap are used between transmission line and power station equipment to-
Avoid carrier power dissipation in the power plant reduce cross talks with other PLC Circuits connected to the same power station.
Ensure proper operating conditions and signal levels at the PLC transmit receive equipment irrespective of switching conditions of the power circuit and equipments in the stations.
Line Matching Filter & Protective Equipments
For matching the transmitter and receiver unit to coupling capacitor and power line matching filters are provided. These flitters normally have air corral transformers with capacitor assumed.
The matching transformer is insulated for 7-10 KV between the two windings and perform two functions. Firstly, it isolates the communication equipment from the power line. Secondly, it serves to match .
Figure-4.1 Line Matching Filter & Protective Equipments
The transmitter consists of an oscillator and a amplifier. The oscillator generates a frequency signal with in 50 to 500 HZ frequency bands the transmitter is provided so that it modulates the carrier with protective signal. The modulation process usually involves taking one half cycle of 50 HZ signal and using this to create block to carrier.
The receivers usually consist of and alternate matching transformer band pass filter and amplifier detector.
The amplifier detector converts a small incoming signal in to a signal capable of operating a relatively intensive carrier receiver relay. The transmitter and receiver at the two ends of protected each corresponds to local as far as transmitting.
When carrying out inspection or maintains work in substation ,it is essential to disconnect reliability the unit of other station on which the work is done from all other parts on installation in order to ensure full safety of working staff .So guard against mistake it is desirable that should be done by an apparatus is called “ISOLATOR”. In other words a device which is used to open or close the circuit either when negligible current is interrupted or when no significant change in voltage across the terminal of each pole of the isolator will result from operation .they must only be opened or closed when current is zero. There is single ear thing Isolator used .
Isolator is switching device used to open (or close) a circuit either when a negligible current exists or when no significant change in voltage across the terminal of each pole of the isolator, will result from the operation.
Broadly speaking isolator are the switches which’s operate under "No current” condition. Thus, isolator is an apparatus which makes a visible and reliable disconnection of the unit or the section after opening the circuit breaker.
Isolators are file with earthing blades as an integral part of it. They may be isolators with single ear thing blades or two earthling blades on either side of it. The isolators used at 220 KV GSS,Bharatpur have single earthing blades either side of it.They must only be opened or closed when current is zero. Isolators are classified into following categories.
1. Bus isolator
2. Line isolator
3. Transformer isolating switch
From constructional point of view the isolator may be classified as-
1.The post- centre post rotating part, double post break type.
2.Two post single type.
3.Base: - Each pipe phase isolator is mounted on a robust base of steal construction.
Figure- 5.1 Isolator
The central post rotates in gun metal bushing and tapered roller bearing provided with grease nipples for lubrication required to be alone at regular’s intervals during routine check up.
(For line side insulation only ) Earthling is achieved by means of an earthed blade pivoted at the base steady operation mechanism .the earth contacts are fixed either at the back or left or right side of main contact and interlocked with them by mechanism interlock.
1.Hand operated: - It consists of a fulcrums and level system for easy operation of isolators.
2.The isolators used in G.S.S Bharatpur at are three post types. Each isolator has three insulators post per phase mounted on a phase of steal construction.
The transformers which are used in A.C. system for the measurement of current, voltage, power and energy are called Instrument transformer. These are also used in connection with the measurement of power factor, frequency and for indication of synchronism.They are two types namely:
Figure-7.1 POWER X-MER
(1) Core type
(2) Shell type
The x-mer used substation is auto-transformer which employed only single winding per- phase. A part of winding is common to both of sides. In addition to primary and secondary winding known as tertiary winding is also provided the power transformer required at substations contain following additional part –
1. HV winding bushing
2. LV winding bushing
3. Tertiary winding bushing
4. Jucking plate
Transformer used in conjunction with measuring are ‘INSTRUMENT TRANSFORMER’. According to the quality measured. These may be divided as
1. Current transformer
2 Potential transformer
These instrument transformers are used to step down these current and voltage. So that they would be metered with instrument of moderate size.
The current transformers are kept in the category of the instrument transformer. The C.T. are used to reduce/ stepping down A.C form high value to lower value for measurement / protection / control.
They are usually installed in the out door switch. The primary conductor at high voltage with respect to earth. The secondary of C.T. is just like the ring type C.T. the primary winding consists of a very few turns , and therefore there is no. appreciation volt drop across injection . Current is transformed by C.T. the current transformer is used with primary winding , connected in series with the line carrying the current to be measured and therefore primary current is dependent upon load connected in the system.
Measurement of alternating current is one of the most frequent operation not only because of it’s inheriant but a also because it is necessary in determining other parameters of electrical circuit. A current transformer value of current is used for Indication of current kwh and kw meters Telementry Protective relay etc
A current transformer is intended to operate normally with rated current of the system flowing through the primary winding which is increased in the series with the network .Secondary winding of current transformer Connected to measuring instruments and relay supplies currents circulating in the design of current transformer.
Similar to CT it is another type of instrument type of instrument transformer .Transformer used for voltage measurements are called voltage transformer or Potential transformer. it may be of 1 phase or 3 phase
These transformers make the instruments suitable for measurement of high voltage and isolating then from high voltage. these transformer are connected in parallel and secondary winding is always open ckt.
The primary winding of the potential transformer is connected to the main GSS LINE DIAGRAM. the primary has large no of turn in secondary,which provided step down of voltage , and then the voltmeter is connected across secondary terminal the high voltage line.
Some terms related to PT :-
A. RATED VOLTAGE :- the capacity voltage of the PT which it can stand
B. RATED TRARNSFORMER RATIO:- The ratio of the rated primary voltage to the rated second voltage.
C. RATED SECONDARY VOLTAGE:- 130 / root (3) = 63.3 VAR.
Voltage transformer which step down system voltage to sufficient form high value to low value are necessary in every system for
Induction of d.c supply voltage conduction.
Metering of the supply of energy.
Design and ranges are selected according to the secondary size of potential transformer for indicating instruments, meter and relays. But calibration of these instruments is done according to the primary voltage .
The transformers are used to step down or step-up the incoming line voltage but at grid substation for the purpose of distribution. it is the main & major requirement of GSS for step down the supply voltage .The rating of transformer is taken according to the load .
There are three power transformers of 100 MVA . They are used convert 220 KV/132 KV. Which transforms e/e energy from one voltage level to another desired level with corresponding change in current value and with out any change in frequency value.
The physical basis of a transformer is mutual induction between the circuits linked by a common magnitude pulse voltage supplied to one set of winding called primary switch builds up a magnitude flux through the iron.
A transformer in simplest form consist of two magnetic coil, which are electrically separated from each other but magnetically linked through path of reluctance .
In brief a transformer is a device that
1. Transform electric power from the one circuit to another.
2. It does not so without a change of frequency.
3. It accomplishes this by electromagnetic induction.
The magnetic core is built up of laminations of high –grade section or other steel which are insulated from each to other by varnish or other insulation materials.
According to the number of winding placed around the core. The transformer are classified as
5. Earthing terminals the trank
6. Cooling systems
7. Pressure relief value
8. Bush hold relay
9. Dehydration breather
The automation required use of automatic voltage control of substation so that a predetermined bus- bar voltage can maintained. In general a tap changer is provided on a transformer for a maintaining a pre determine outgoing voltage where the incoming voltage may be subjected to voltage variations. The output of P.T. connected to controlled voltage side of the power of transformer is used to energize the automatic voltage regulating relays. The voltage to be controlled remains with in prescribed limits.
GAS OPERATED RELAY:-
The relay is located in the pipe between the main tank and conservator. In case of fault such as insulation was creating impulse failures fall of oil level produces gases. This rises and accumulated in the upper part of the housing consequently the oil level falls down and the float sinks thereby tilling the mercury switch. The conducts are closed and alarm circuit is energized. Bachholz protection is always used in conjunction with some other forms of electricity operated protective gears as it can unity operate for truly internal transformer faults and does not respond to external bushings or cable faults.
SILICA GEL BREATHER:-
A silica gel breather is employed as a measurement of preveusing moisture in gress. It is connected to the conservator tank which is filled to transformer to allow for changes in volume due to temperature variation.
FILTER: - Filter is intended for prolonging like water acid etc from oil. .
In transformer, the insulating oil provides an insulating medium as well as a heat transferring medium that carry away heat produced in the winding and iron core.
The life of the transformer depends chiefly upon the quality of the insulating oil. So high quality insulating oil are used. It should meet the following requirements:-
· It should be provide good transfer of heat.
· It should provide high electric strength.
· It should have low velocity.
· Flash point of the oil must be high.
· Also fire point should be high.
In order to avoid current leakage to the Earth, through the supporting structure provide to the conductor of overhead transmission lines, insulators are used. The conductors are secured to the supporting structures by means of insulating feature, which do not allow current to flow through these support and hence finally to the earth . Bus support insulators are porcelain or fiberglass insulators that serve to the bus bar switches and other support structures and to prevent leakage current from flowing through the structure or to ground. These insulators are similar in function to other insulator used in substations and transmission poles and towers.
An Insulator should have following characteristic:-
1. High Insulation resistance.
2. High mechanical strength
3. No internal impurity or crack Disc
Generally Porcelain or glass is used as material for insulators. Porcelain because of its low cost. is more common.
Insulators can be classified in following ways :-
Pin Type: - These are designed to be mounted on a pin, which in turn is installed on the cross arm of a pole.
Suspension Type:-These insulators hang from the cross arm, there by forming a string.
The centre post carries the moving contact assembled at the extremities the moving contact engages the fixed contacts are generally in the form of spring loaded finger contact.
The insulator consist of following parts -
1. Contacts :- The contacts are rated for line current and designed to withstand electromagnetic strains and prevent charging at rated shortly time current the contact are made of electrolytic fixed in housing.
2. Switching blade:- The blade is made of electrolytic copper.
3. Tandom pipe:-All three phases are opened or closed simultaneously with a tandem pipe this is dipped galvanized and provided with on or off insulators and pad locking.
4. Motor operated:-This is meant rotary motion of the linear operating pipe for either of opening or closing for remote level local operation. Hand operation is also provides with detectable handle that can be fitted and square.
Breakers are switching and current interrupting devices. Basically a circuit breaker comprises a set of fixed and movable contacts. The contacts can be separated by means of an operating an arc. The arc is extinguished by a suitable medium such as dielectric oil vacuum, SF6 gas.
The circuit breakers play an important role in the design and performance of a power system, in that these are the key pieces of apparatus protecting the system and thus ensure continuity of supply from consideration of cost, the circuit breakers represent a major items, and are, next only to the generator and transformer, since their quantity is greater than that of generators/transformer in a power system owing to the services required for control of transmission lines, bus-bar etc. in addition to control of transformers and generator.
Figure-9.1 CIRCUIT BREAKERS.
FUNCTION OF CIRCUIT BREAKER
The expected functions of a circuit breaker are: -
i. It must be capable of closing on to and carrying full load currents for long period of time.
ii. Under proscribed condition, it must open automatically to disconnect the load or some small overload.
iii. It must successfully and rapidly interrupt the heavy current, which flow when a short circuit has to be cleared from the system.
iv. It must be capable of closing on to a circuit in which a fault exists and immediately re-opening to clear the fault from system
v. It must be capable of carrying current of short circuit magnitude until, and for such time as, the fault is cleared by another breaker nearer to the pint of fault.
Circuit Breaker Types
i. Bulk oil Circuit Breakers
ii. Minimum oil Circuit Breakers.
iii. Air blast Circuit Breakers
iv. Sulphur hexafluoride (SF6) Circuit Breakers.
v. Vacuum Circuit Breakers
AIR BLAST CIRCUIT BREAKER
This type of breaker find application operating system from 132 kv and these are meant for outdoor used and based on the multiple interception. Principal using compressed air as a medium for quenching the arc. The compressed air acts as a medium of high dielectric strength which present flashover across the writers in case of over voltage when the contacts are in open position. The breaker can be opened or closed pneumatically from the control cabin or by protective relay or electrically fault occuring the operating pressure used at G.S.S Bharatpur is 12 kg/cm.
AIR BLAST C.B. HAS FOLLOWING ADVANTAGES:-
1. No fire hazards caused by oil.
2. The C.B operates at hogs speeds.
3. The duration of arc is possible.
4. Frequent operation of C.B’s is possible.
5. Almost no maintenance is needed.
6. Facility of high speed recoding.
TYPES OF AIR BLAST C.B’s:-
There are three types of air blast circuit breaker:-
1. Axial blast C.B.
2. Axial blast air C.B. and with side moving contact.
3. Cross blast air circuit breaker.
In the closed position of air blast circuit breaker. There is no compressed air in arc chamber hallow calcium insulator. When fault occurs on the line CB operates and compressed air quenches the arc into no of section.
VACUUM CIRCUIT BREAKER
FUNCTION OF SF6 GAS IN SF6 CIRCUIT BREAKERS
The density of SF6 Gas is about five times that of air and heat dissipation in it is also much more than in air.
Air atmospheric pressure dielectric strength of SF6 gas is about 2.4 times that of air and at about 3-Kg/cm2 it is same as that of oil. Table no. D1 gives physical properties of SF6 gas.
There is some decomposition of the gas long periods of arcing. However such decompositions very little and has no effect upon dielectric strength and interrupting capability. The solid are product formed by arcing metallic fluoride, which appears in the form of fine gray powder. This are generated power has high dielectric strength under dry conditions existing in the breaker. A good quality absorbent is used so that the level of the gaseous by products is kept very low. Certain impurities such as air result in the dilution of SF6 gas in the field as long as the process recommended is followed. While releasing the arced gas into atmosphere, international sniffing of gas should be avoided. The relation between SF6 gas pressure and temperature is given in fig. 4.13, which is a very useful date at the tie filling of SF6 in circuit breaker.
Figure-9.2 SF6 CIRCUIT BREAKERS
Earthing is the provision of a surface under the sub station, which has a uniform potential as nearly as zero or equal to Absolute Earth potential. The provision of an earthing system for an electric system is necessary by the following reason.
1. In the event of over voltage on the system due to lighting discharge or other system fault. These parts of equipment which are normally dead as for as voltage, are concerned do not attain dangerously high potential.
2. In a three phase, circuit the neutral of the system is earthed in order to stabilize the potential of circuit with respect to earth.
The resistance of earthing system is depending on shape and material of earth electrode used.
The earthing is of two principal types :-
· Neutral Earthing
· Equipment Body Earthing
Neutral Earthing also known as System Neutral Earthing (or Grounding) means connecting the neutral point i.e. the star point of generator,transformer etc. to earth. In rotating machines, generator, transformer circuit etc., the neutral point is always connected to earth either directly or through a reactance. The neutral point is usually available at every voltage level from generator or transformer neutral. If neutral point is not available, then the most common method used is using a Zigzag transformer. Such a transformer has no secondary. Each phase of primary has two equal parts. There are 3 limbs and each limb has two winding, providing flux density under normal condition. Since the fluxes are opposite, the transformer takes very small magnetizing current under normal conditions. During fault, the circuit is primary side,
which provides very less impedance to the current. The grounding transformers are short time rating. Their size is almost one tenth as compared to power transformer.
Electrical Earthing is different from neutral earthing. During fault condition, the metallic parts of an electrical installation which do not carry current under normal conditions, may attain high potential with respect to ground. As human body can tolerate only I=0.165A/T current for a given time t so to ensure safety we connect such metallic parts to earth by means of Earthing system ,which comprises of electrical conductor to send fault current to earth. The conductor used is generally in the form of rods, plates, pipes etc.
Earthing system ensures safety in following ways :-
1. The potential of earthen body does not reach dangerously high value about earth, since it is connected to earth.
2. Earth fault current flows through earthing and readily causes the operation of fuse or an earth relay.
Connection of Electrical Equipment to Substation:-
S.NO. Apparatus Path to be connected 1. Supporting of bus insulator Base plate 2. High voltage circuit breaker Operating mechanism frame 3. Isolator Operating mechanism frame bed 4. Potential transformer Transformer tank LV 5. Power transformer Core tank
Merits of neutral Earthing:-
1. Arcing grounding is reduced.
2. Voltage of heating with respect to earth remains at harmless value they don't increase to root 3 times of normal value.
3. Suitable neutral point.
4. The earth fault relaying is relatively simple useful amount of earth fault current is available to operate earth fault relay.
5. The over voltage due to lightening are discharged to earth.
6. Improved service reliability due to limitation of arcing ground and improved of unnecessary fringing of CB.
At GSS the neutral point of power transformer is connected solidly to earth generally the earth connection are provided which leads reliability.
The purpose of protective relay and protective system is to operate the correct CB‘s as to disconnect only the faulty equipment from the system as quickly as possible. Thus minimizes the trouble caused by fault by they do occur. The protective relay does not operate possibility of the fault on the system. Their active starts only after the faults have occurred. It could be idea led if the protection could anticipate and peasant faults because it is impossible to except where original case of fault create some effects which can operate a protective relay. These are two groups of protective relay.
1. Primary relaying equipments.
2. Back-up relaying equipments.
Primary relaying is the first line of difference whereas back up protection relaying works. Only when the primary relaying equipments fails and also back up relays are slow in motion condition. Another job of back relay is to act as primary relay in case of where this is out work.
Relay must operate when it is required. Since relay remains ideal. Most of the time proper maintenance also plays important role in improving reliability. Relay should select fault region and isolate that section from circuit. It should also operate required speed. It should neither be slow which may not result in damage to the equipment nor it should too fast which may result undesired operation during transient faults and should be sensitive to faults.
The protective relay serves for preventing tap changers and transformer from being damage which is the part of delivering the protective relay as to be connected in away that transformer immediately switched off captions oil immersed transformer. Transformer break down are always precede by more or less violent generation of gas. A broking joints produce local arc and vaporize in the vicinity. As earth faults has the some results sudden short circuit rapidly increased the temperature of the winding particularly the inner layer and packed oil in vaporize. Discharge due to insulation weaken i.e. by the dehydration of the oil produce local heating and generate gas. The generation of oil vapour or gas in utilize to actuate a relay the relay is arranged between the transformer tank and the separate oil conservator. The vessel is normally is full of oil. It contains two floats if the gas bubbles are generated in transformer due to faults. They will be rise and transfers the conservator and will trap in the upper part of the relay chamber. Thereby displacing the oil and lowering the faults. This sinks and eventually closes and external contacts which operates an alarm over other protection and flashover at the bushing are not at adequately covered by other protective scheme also unless it improves ground.
The differential scheme detects such faults and also on the leads between CTs are power transformer provided ct’s are not mounted separately on transformer bushing. In service internal faults operate when the relay is energizes. The protective relay reenergized only by oil flow from the tap changer heat to the conservator. The oil flow operates the flap value which is trapped into the “off” position by timing mechanism. Thus the trapping switch is energized the CB’s are operated the transformer off the line.
To remote control of power switch gear requires the provision of suitable control plates located at a suitable point remote from immediate vicinity of CB’s and other equipments.
At "GSS BHARATPUR" the separate control room provided for remote protection of 220KV switch yards transformer incoming feeder, outing feeders. Bus bar has their own control plant in their control rooms. The control panel carrier the appropriate relays. Necessary meters indicating lamp control switches and fuses. There are meters for reading purpose. A circuit concerning the panel is shown on the panel with standard co lour.
On each panel a control switch is provided for remote operation of circuit breaker. There are two indicators which show that weather circuit breaker is closed or open. A control switch for each insulator is also provided. The position indicator of isolator is also done with the help of single lamp and indicator. The colour of signal lamps are as follows :-
RED:- For circuit breaker or isolator is close option
GREEN:-For CB or isolator in open position.
In addition to used indication an alarm is also providing for indicating abnormal condition when any protective relay or tripping relay has operated. Its constants energies on auxiliary alarm. Relay which on operation completes the alarm belt circuit.
There is a hinged Synchronizing panel mounted at the end of control panel. Before coupling any incoming feeders to the bus bar. It just be Synchronized with switches. When the synchronous copy shows zero we close the circuit breaker.
Synchronoscope is used to determine the correct instant of closing the switch which connect the new supply to bus bar. The correct instant of synchronizing when bus bar incoming voltage.
a. Are in phase
b. Are equal in magnitude
c. Are in some phase sequence
d. Having same frequency
e. The voltage can be checked by voltmeter the function of synchronoscope is to indicate the difference in phase and frequency.
These are fitted on different panel to record transmitted energy and recorded in energy hours. For this purpose MWH meter have been provided.
This is mounted on each feeder panel to record import or export power.
Provided to each feeder to measure frequency which analog or digital.
Volt Meter :-
Provided on each panel or the purpose of indication of voltage.
These are used to indication the line current.
Provided for indicating power factor of import and export.
Maximum Indicator Demand :-
Chief requirement of these indicators to record the minimum power factor taken by feeder during a particular period. This record the average power successive predetermined period.
There is a battery sexton or battery room which has 55 batteries of 2 volt each for 132KV section and 110 batteries for 220KV section. Therefore D.C. power available is for functioning of the control panels. A battery charger to charge the battery.
· Various parts of lead acid batteries:-
o Terminal port
o Vent plugs
Charging of batteries:-
It is the first charging given to batteries by which the positive plates are converted to “lead peroxide”, where as the –ve plates will converted to spongy lead.
Also in a fully charged battery the electrolyte specific gravity will be at its highest venue or 1.2 and its terminal voltage will be 24 volts
When a fully charged battery delivers its energy out by meeting a load the lead peroxide of the +ve plates slowly gets converted to lead sulphate and the spongy lead of the –ve plates also gets converted into lead sulphate during this time the specific gravity of the electrolyte also decreases the value around 1.00 and the terminal voltage also decreases from its initial to a lower value which may be around 1.85 or 1.8.
The training at grid substation was very helpful. It has improved my theoretical concepts of electrical power transmission and distribution. Protection of various apparatus was a great thing. Maintenance of transformer, circuit breaker, isolator, insulator, bus bar etc was observable.
I had a chance to see the remote control of the equipments from control room itself, which was very interesting.
So the training was more than hope to me and helped me to understand about power system more.Similar Threads:
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