A substation is a 'part of an electrical generation, transmission, and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several others important functions. Between the generating station and consumer, electric power may flow. Through several substations at different voltage revels.
Substations may be owned and operated by an electrical" utility or may be owned by a large industrial or commercial customer. Generally, substations are unattended, relying on SCADA for remote supervision and control. A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages.
The word substation comes from the days before the distribution system became a grid. As central generation stations became larger, smaller generating plants were converted to distribution stations, receiving their energy supply from a larger plant instead of using their own generators. The first substations were connected to only one power station, where the generators were housed, and were subsidiaries of that power station. Electric power is produced at the power generating stations, which are generally located far away from the load centers. High voltage transmission lines are used to transmit the electric power from the generating stations to the load centers. Between the power generating station and consumers several transformations and switching stations are required. These are generally known as substations. Substations are important part of power system and form a link between generating stations, transmission systems and distribution systems. It is an assembly of electrical components such as busbars, switchgear apparatus, power transformers etc.
Their main functions are to receive power transmitted at high voltage from the generating stations and reduce the voltage to a value suitable for distribution. Some substations provide facilities for switching operations of transmission lines, others are converting stations. Substations are provided with safety devices to disconnect equipment or circuit at the time of faults. Substations are the convenient place for installing synchronous condensers for the purpose of improving power factor and it provide facilities for making measurements to monitor the operation of the various parts of the power system.
The substations may be classified in according to service requirements and constructional features. According to service requirements it is classified into transformer substations, switching substations and converting substations. The present-day electrical power system is a.c. i.e. electric power is generated, transmitted and distributed in the form of alternating current. The electric power is produced at the power stations which are located at favorable places, generally quite away from the consumers.
TYPES OF SUBSTATIONS:
Ø Single Bus bar
Ø Mesh Substation
Ø One and a half Circuit Breaker layout
Ø Main and Auxiliary bus bar
Ø Double bus bar
Ø Double Main and Auxiliary bus bar
Rigid non-metallic conduits are used for surface, recessed and concealed conduit wiring. Conductors of ac supply and dc supply shall be bunched in separate conduits. The numbers of insulated cables that may be drawn into the conduit are given in table.
Maximum permissible number of 1.1 kV grade single core cables that may be drawn into rigid nonmetallic conduits.
Conduit shall be fixed by saddles secured to suitable wood plugs or other plugs with screws at an interval of not more than 60 cm. whenever necessary, bends or diversions may be achieved by bending the conduits or by employing normal bends, inspection bends, inspection boxes, elbows or similar fittings.
INDIAN ELECTRICITY RULES
The Indian electricity act, 1910
This is an act relating to amend the law relating to the supply and use of electrical energy. It regulates :-
Grant of licenses, revocation or amendment of licenses;
Purchase of under takings annual accounts of licenses.
The electricity (supply) Act 1948:
This act rationalizes the production and supply of electricity and generally provides for taking measures conductive to its development. It enacts The central electricity authority Constitution and State electricity boards.
The electricity regulatory commission act, 1998:
The act provides for the establishment of the central electricity regulatory commission and state regulatory commission, Central and state transmission utilities, Framing grid code and grid standards, Rationalization of electricity tariff, Transport policy regarding subsidies.
The electricity act, 2003:
The content supersedes and consolidates the provision of the electricity regulatory commission act, 1998, the Indian electricity supply act, 1948 and the electricity act 1910
Energy conservation act 2001:This act concerns any form of energy derived from fossil fuels, nuclear substances or materials and hydroelectricity and includes electrical energy or electricity generated from renewable.
The Indian electricity rules 1956:
As per section of 37 of Indian electricity act 1910. The central electricity board has framed the Indian electricity rules 1956. It contains 143 rules along with detailed annexure and covers:
Ø Authorization to form duties.
Ø Inspection of electric Installations
Ø creation of inspection agency, entry and inspection,
Ø inspection fees, appeal against an order,
Ø submission of records by supplier or owner
Ø Licensing: application, contents and form of draft license.
Ø Advertisement of application and contents there of approval of draft license and a notification for grant of license.
Ø Commencement of license.
Ø Amendment of license preparation and submission of accounts and model condition of supply.
Ø General safety precautions regarding, construction, installation, protection operation and
Ø maintenance of electric supply lines and apparatus., service lines and apparatus on consumers premises., identification of earthed conductors, accessibility of bare conductors, provisions applicable to protective equipment instructions for restoration of persons suffering from electric shock.,
Ø Intimation of accidents precautions to be adopted by consumers, owners’ electrical contractors electrical work man and suppliers, periodical inspection testing of consumers installations.
Ø General conditions relating to supply and use of energy: Testing of consumer's installation
Ø Precaution against leakage. Defined voltage and frequency of supply pacing and sealing of energy and demand meters.
Ø Point of supply precautions against failure of supply.
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