• GENERAL DISCUSSION ON SUB STATIONS• SINGLE LINE DIAGRAM• COMPONENTS USED• ISOLATERS• BUSBARS• CIRCIUT BREAKERS AND ITS CLASSIFICATION• POWER TRANSFORMERS AND ITS MAIN PARTS• INSTRUMENT TRANSFORMERS• CURRENT TRANSFORMERS• BUCHOLZ RELAY• EARTHING• POWER LINE CARRIER COMMUNICATION
Substation:- A station is a subsidiary station of an electricity generation, transmission, & distribution system where voltage is transformed to high to low or the reverse using transformers.A substation generally have switching, protection, & control equipment & one or more transformers.Types:-(a) Transmission substation(b) Distribution substationTransmission substation connects two or more transmission lines.Distribution substation transfers power from transmission system to the distribution system of an area.
Isolators are designed to open a ckt under n0 load. Its main purpose is to isolate portion of ckt from the other & is not intended to be opened while current is flowing in the line. There are two types of isolators:- off load isolators on load isolators
DEFINITION:- A bus bar is a conducting bar that carries heavy currents to supply several electric circuits.When a no. of generators or feeders operating at the same voltage level to be directly connected electrically, busbar are used as the common electrical component. Bus bars are copper rod or thin walled tubes and operate at constant voltage.TYPES OF BUSBARS:- Main busbar Auxiliary busbarOne busbar is main busbar & another is spare or auxilary busbar.
A circuit breaker is a piece of equipment which can:- break a ckt automatically under fault conditions. make a ckt either manually or by remote control under fault conditions.PRINCIPLE:- A ckt breaker essentially consists of fixed & moving contacts, called electrodes under normal operating conditions, these contacts remain closed & will not open automatically until & unless the systems becomes faulty. When a fault occurs on any part of the system, the trip coils of the breaker get energised & the moving contacts are pulled apart by some mechanism. Thus opening the circuit.
CLASSIFICATION:- oil circuit breakers Sulphur Hexa Fluoride circuit breakers Air-Blast circuit breakers vaccum circuit breakers Under training SF6 type, vaccum ckt breaker & Air- Blast ckt breakers were used in the GSS.
Transformer is an electrical machine which works on the principle of electromagnetic induction. It transfers electric power from one electric ckt to other with the help magnetic path(flux) on constant frequency but equal or different current voltages. For this purpose two sets of insulated windings are wounded on a close terminated steel core. The winding which is connected to the supply is called primary winding & that winding is connected to the load is called secondary winding.
MAIN PARTS OF POWER TRANSFORMERS:-a) coreb) Winding(H.V winding, L.V winding, tertiary winding)c) Tap changerd) Tanke) Conservatorf) Air cellg) Buchholz relayh) Dehydrating breatheri) Oil temperature indicatorj) Winding temperature indicator
Instrument transformers are used for measurement and protective applications together with equipments such as meters & relays.The lines in a station are operated at high voltages and carry currents of thousands of amperes. The measuring and protective devices are designed for low voltage generally 100v and currents about 5A, therefore they will not work satisfactory if mounted on the power lines. This difficulty can be overcome by using instrument transformers, which will step down the voltages and currents to the convenient level for the operation of measuring instruments & relays.
C.T. is an instrument transformer used for protection & metering of high values of currents. C.T. is used for reducing a.c from higher to lower value for measurement/protection/control. There are two classes of C.T: protective C.T measuring C.T Protective C.Ts are used for over current protection, earth fault protection, differential protection& impedence protection, etc. Measuring C.Ts are used with ammeters, wattmeters, KV meters & KWH meters for reducing line.
Potential transformers are instrument transformers. They have a large number of secondary turns and a fewer number of primary turns. They are used to increase the range of voltmeters in electrical substations and generating stations.These are also called as voltage transformers used for line and circuit protections.
Definition:- Buchholz relay is a gas actuated relay. It can only be fitted to the transformers equipped with conservator tanks as it is installed in b/w the conservator tank and the main tank i.e., the pipe connecting the two.Principle:- Whenever a fault occurs inside the transformers, the oil of the tank gets overheated and gases are generated.The heat generated by the high local current causes the transformer oil to decompose and produce gas which can be used to detect the faults.
Operation:- When a fault occurs, heat is produced due to current leakage, some of the oil in the transformer tank evaporates and some vapours collect in the top of the chamber while passing to conservator tank. When a predetermined amount of vapours accumulate in the top of the chamber, the oil level falls, and so closes the alarm circuit of the relay and rings the bell. Thereby the operator knows that there is some fault occurred in the transformer.
Connection of an electric equipment to the earth with the help of connecting rod or wire of negligible resistance is known as earthling. Methods of earthling arrangements at 132 kv GSS: pipe earthling plate earthling
For exchange of datas and transfer message between grid substation, voice communication is necessary. for this purpose high frequency carrier current is transmitted on same transmission line on which power is transmitted.Hence such communication is called “power line carrier communication’’.
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