ABSTRACT: Electricity is a form a energy and is playing vital role in the world. Electricity has become a part of human life. Electricity is developed at one place and transmitted to other places, where the demand exists and resources are not available. So as to achieve balanced regional development of the country. The main aim of the project is 1.To study the operation of switchyard are to facilitate switching operations in transmitting electrical energy from generating station to substation. 2.To acknowledge the protection methods facilitated by the switchyard. 3.And to know switchyard equipment and their operation in detail. The main functions of switchyard are to facilitate switching operations, and to protect the generating station from the faults. Switching operations includes stepping up the generated voltage levels to value which is equal to the substation voltage, and monitoring electrical parameters continuously.

INTRODUCTION TO PROTECTION: Protection is the electrical equipment from faulty section the main objection of protection is to quickly isolate a fault from the ends Faults can occur on any power system components like generator, transformer, and motors etc. faults are generally falling in to two categories short circuit faults. Open circuit faults, short circuit faults are resulting in very abnormal high current if they followed to persist even for short period of time, it can lead to extensive damage to equipment.

SWITCHYARDLAYOUT: After the bus bar arrangement has been decided upon and key diagram are prepare to show the actual Position of the each equipment First prepared on the land plan, space is marked for civil and electrical workers and also The roads and path for movement of men and material On the land plan marked for electrical workers detailed layout which indicates the placing of various equipments In the switchyard is prepared.

Switchyard Description Switch yard is a place where the entire primary protecting equipment of the power system is arranged in a systematic manner from generator transformer to feeders by connecting the transmission lines. The switch yard mainly works on the purpose of stepping the grid voltage down to a certain value. The switchyard under study works on 132/11kv i.e., the input of the transformers 132kv and It steps down to 11kv.the substation receives the 132kv from 220kv substation. The received voltage is stepped down to the required value by using a three phase auto transformer .the auto transformer is economically efficient compared the ordinary there phase transformer. To step down the 132kv voltage to 11kv, auto transformer having 15mva capacity is employed.

The ratings of power transformers that are used in A.P system Ratings of the Transformers: The ratings of power transformers that are used in A.P system 132/11 KV 15 MVA Transformers 11/0.44 KV 2MVA Transformers. Most of the power transformers of 132/11 KV and above are of star-delta vector grouping with the neutral solidly earthed. There are a few transformers with delta-star (delta on HV side). The 33/11 KV and 11KV/415v transformers are of delta-star (delta on HV side).

GENERATOR TRANSFORMER: The generator takes power that is fed to it by the alternator. Here the voltage at a lower level is transformed into a higher level as the higher level transmission is very economical. A transformer is a static device by means of which of which electric power in one circuit is transformed into electric power of the same frequency in another circuit. it can rise or lower the voltage in a circuit, but with a corresponding increase in current basically transformer will work on mutual induction principle between two circuits linked by a common magnetic flux. It is a star-delta power transformer the transformer is connected to the bus by a thin laminated sheet conductors there by constant losses present in the bus can be eliminated to a maximum extent. Thus the generator transformer connects the electromechanical alternator to the static bus bar. The transformer protection is carried out by the buchholz relay. Differential relay, distance relay, and lightning arrester, thus the important part of the switchyard.

AUXILIARY TRANSFORMER: This is the one used for the maintaining the power supply to the auxiliaries and accessories present in the power plant when the entire generating unit of the station is ruined. The transformer takes power from the grid to it is connected and the power is supplied. It is star delta connected.

LIGHTNING ARRESTER: Lightning arrester is also known as surge diverter or surge arrester. They are connected between the line and ground at the substation and always parallel with the equipment to be protected and perform their function by providing a low impedance path surge currents, the surge arresters protective level is less, than surge voltage withstanding capacity of the insulation equipment being protected. The lightening arresters protective level is that the voltage appearing across the terminals of the arrester at spark over or during the flow of current through the arrester after spark gap over. The purpose of lightening arrester is to divert or discharge the surge to the ground.

CURRENT TRANSFORMER: The current transformer is basically a step up transformer.teh primary winding of the current transformer is wound in series with the point where the current is to be sensed small portion of the current flows in the secondary depending upon the turn`s ratio of the transformer. To reduce the burden on the current transformers banks of capacitors are connected in parallel so that the voltage burden is eliminated thus the efficient operation of the system can be obtained. Current transformers are the instrumentation transformers which are used for the metering and protection purposes. The CT ratio is about 600/300:5 through the CT the high magnitude current is stepped down to a corresponding lower current. This current is used for the metering purpose.

CAPACITOR VOLTAGE TRANSFORMER (CVT): Voltage transformers are used for measurement and protection.VT`S are necessary for voltage, Directional distances protection. the primary of VT`S is connected to power circuit between phase and ground. The volt ampere rating of VT is smaller as compared with that potential transformer. CVT`S are used for line voltmeters,synchroscope,protective relays, traffic meter etc. The performance of CVT is inferior to that electromagnetic voltage transformer. Its performance is affected by the supply frequency, switching transients, magnitude of burden connected etc. T he CVT is more economical than an electromagnetic VT,when the system voltage normally increases above 66kv.the carrier current equipment can be connected to the capacitor of the CVT`S thereby there is no need of separate coupling capacitors.

BUS BAR: Bus Bar means conductors to which a number of circuits are connected. The power that is trapped from the station alternator by the station transformer will be fed to the bus bars all the bus bars must be cable of handling very high power ratings. Their mechanical strength is such that they are capable of carrying thousands of amperes of current though them. Aluminum is used from the manufacturing bus bars. The bus bars should have low resistance, higher softening temperature and good mechanical properties the currents having an angle of 500 amps the size of the conductor should be around 190mm. Generally a pair of buses, main bus and the stand by bus or reverse bus connected with the help of bus coupler.

ISOLATORS: Isolators are used for making breaking the circuits. Isolators operate under no load condition only. It does not have any speccific current breaking capacity or current making isolator is not used even for breaking load currents. Current is passed through the primary winding of standard C.T and C.T under test. The ratio of the C.T can be determined by comparing the currents in ammeters A1 and A2. Isolators are used in addition to CB`s and are used while closing a circuit. The isolator is closed first the CB. 2) Isolators are necessary on supply side of CB`s in order to ensure isolation of the CB from live parts for the purpose of maintenance. Automatic switching of isolators is preferred.

CIRCUIT BREAKER: The circuit breaker we use in this 132/11kv switchyard is sf6 circuit breaker .for high voltages such as 132kv and above voltages, we use this circuit breaker. The sf6 circuit breaker will operate mainly on the principle of PUFFER principle in extra high voltage operation. As the puffer cylinder moves downwards for the opening stroke, the pressure ratio p1/p2 raises. It depends upon the throat diameter of the nozzle and speed of puffer cylinder the pressure ratio increases to about S times during opening condition. The compressed gas is released through the convergent-divergent nozzle. The arc is quenched at a current zero, for higher interrupting ability, the flow pattern is optimized.

PROPERTIES OF SF6 CIRCUIT BREAKER: High dielectric strength. Thermal and chemical stability. Non- inflammability. Pure sf6 gas is inter and thermally stable. Sf6 gas is an electro negative gas. When arcing takes place through the gas some y-products are produced due to break down of the gas .these by products are hazard to the health of the maintenance of the personal and therefore proper fare should be taken.

PROTECTIVE RELAYS: The Functional Requirements of the Relay: Protective relays are the devices that detect abnormal conditions in electrical circuits by constantly measuring the electrical quantities, which are different normal and fault conditions. The Functional Requirements of the Relay: Reliability: The most important requisite of protective relay is reliability since they supervise the circuit for long time before a fault occurs, if a fault then occurs, the relays must respond instantly and correctly. Sensitivity: The relaying equipments must be sufficiently sensitive so that is operates reliably when required under the actual condition that produces least operation tendency. Speed: the relay must operates at thee required speed it should neither be slow which may result in damage to equipment nor should it be fast which may result in undesired operation.

CONCLUSION: With advancement of power systems, line and other equipments operates at high voltage and carry large current when a short circuit occurs on the system heavy current flowing through the equipment may cause damage. Switchyard is a place where the entire primary protecting equipment of the power system is arranged in a systematic manner from generator transformer to feeders by connecting the transmission lines. Switch gear covers wide range of equipment concerned with switching & interrupting current under normal & abnormal conditions it includes CT`s, CB`s, relays and other equipment. Switchyard protects the generating station from the faults. It suppress the faults by making them not to reach the generating unit. Thus, a switchyard plays a vital role in the protection