07-01-2014, 02:13 PM
Understanding General Arrangement & Layout of Switchyard.A brief overview of various Switching Schemes, analyzing latest trends in Switchyard
Understanding General .doc (Size: 1.08 MB / Downloads: 35)
Switchyard: Definition
Switchyard is a main connecting link between the generating plant and transmission system.It is the place, where power system begins. Actually, in a power plant, power is generated at low voltage in the range of (11-21 kV). It is well known fact that large amount of power is evacuated at HV and EHV; from economical point of view. In present scenario, 400 kV is used commonly. After generator transformer and before transmission line, switchyard area is constructed.
Switchyard: Types
1. AIR INSULATED SWITCHYARD
2. GAS INSULATED SWITCHYARD
1. AIR INSULATED SWITCHYARD
A Outdoor Switchyard or Substation, consisting of large breakers and towers, is usually located in an area close to the plant. The substation is used as the distribution center where:
electrical power is supplied to the plant from the outside, and
electrical power is sent from the plant
It is essentially a hub for electrical power sources. It exists at a generating station to coordinate the exchange of power between the generators and the transmission lines in the area. A outdoor switchyard also exists when high voltage lines need to be converted to lower voltage for distribution to consumers.
It contains current carrying conductors, grounding wires and switches, transformers, disconnects, remotely controlled arc snuffing breakers, metering devices, etc.
GAS INSULATED SWITCHYARD
GIS (gas insulated switchyard) internationally is getting acceptance on account of technical merits. It has excellent adaptability in meeting most difficult terrain or space constraints. Low space requirements on account of high dielectric strength of gas leads to flexibility of application. Entire switchgear being in a sealed environment gives least impact of polluting conditions like dust, impurities and deteriorating lubricants used in disconnectors. There has been besides above, other factors such as safety, longevity, & adaptability which make GIS an attractive proposition as compared to AIS.
VOLTAGE TRANSFORMERS (CVTs)
Voltage transformers shall be of capacitor voltage divider type with electromagnetic unit.
The CVTs shall be thermally and dielectrically safe when the secondary terminals are loaded with guaranteed thermal burdens.
The electro-magnetic unit (EMU) shall comprise of compensating reactor, intermediate transformer, and protective and damping devices. The oil level indicator of EMU with danger level marking shall be clearly visible to maintenance personnel standing on ground.
The secondaries shall be protected by HRC cartridge type fuses for all windings In addition fuses shall also be provided for protection and metering windings for connection to fuse monitoring scheme. The secondary terminals shall be terminated on stud type non-disconnecting terminal blocks via the fuse inside the terminal box of degree of protection IP: 55. The access to secondary terminals shall be without the danger of access to high voltage circuit.