I need seminar file base on 220 kV gss. I hope this PDF is useful for me...

INTRODUCION

Electrical power is generated, transmitted in the form of alternating current. The electric power produced at the power stations is delivered to the consumers through a large network of transmission & distribution. The transmission network is inevitable long and high power lines are necessary to maintain a huge block of power source of generation to the load centers to inter connected. Power house for increased reliability of supply greater.
An electrical substation is a subsidiary station of an electricity generation, transmission and distribution system where voltage is transformed from high to low or the reverse using transformers. Electric power may flow through several substations between generating plant and consumer, and may be changed in voltage in several steps.

220KV Grid Substation, MADAR:

Its part of RRVPNL. It is situated at madar ajmer. The power mainly comes from 220KV Kishangarh and 220 KV Beawar
The substation is equipped with various equipments and there are various arrangements for the protection purpose. The equipments in the GSS are listed previously. At this substation following feeders are established.
1. TIE FEEDERS
2. RADIAL FEEDERS
220KV GSS MADAR is an outdoor type primary substation and distribution as well it has not only step down but the distribution work
The electrical work in a substation comprises to:
1. Choice of bus bar arrangement layout.
2. Selection of rating of isolator.
3. Selection of rating of instrument transformer.
4. Selection of rating of C.B.
5. Selection of lighting arrester [LA]
6. Selection of rating of power transformer
7. Selection of protective relaying scheme, control and relay boards.
8. Selection of voltage regulator equipment.
9. Design a layout of earthing grids and protection against lightening stockes.

LIGHTNING ARRESTER

A lightning arrester is a device connected between line and earth i.e. in parallel with the over headline, HV equipments and substation to be protected. It is a safety valve which limits the magnitude of lightning and switching over voltages at the substations, over headlines and HV equipments and provides a low resistance path for the surge current to flow to the ground. The practice is also to install lightning arresters at the incoming terminals of the line.

BUS BARS

Bus Bars are the common electrical component through which a large no of feeders operating at same voltage have to be connected.
If the bus bars are of rigid type (Aluminum types) the structure height are low and minimum clearance is required. While in case of strain type of bus bars suitable ACSR conductor are strung/tensioned by tension insulators discs according to system voltages. In the widely used strain type bus bars stringing tension is about 500-900 Kg depending upon the size of conductor used.
Here proper clearance would be achieved only if require tension is achieved. Loose bus bars would effect the clearances when it swings while over tensioning may damage insulators. Clamps or even effect the supporting structures in low temperature conditions.
The clamping should be proper, as loose clamp would spark under in full load condition damaging the bus bars itself.

INSULATOR

The insulator for the overhead lines provides insulation to the power conductors from the ground so that currents from conductors do not flow to earth through supports. The insulators are connected to the cross arm of supporting structure and the power conductor passes through the clamp of the insulator. The insulators provide necessary insulation between line conductors and supports and thus prevent any leakage current from conductors to earth. In general, the insulator should have the following desirable properties:
• High mechanical strength in order to withstand conductor load, wind load etc.
• High electrical resistance of insulator material in order to avoid leakage currents to earth.
• High relative permittivity of insulator material in order that dielectric strength is high.
• High ratio of puncture strength to flash over.
These insulators are generally made of glazed porcelain or toughened glass. Poly come type insulator [solid core] are also being supplied in place of hast insulators if available indigenously. The design of the insulator is such that the stress due to contraction and expansion in any part of the insulator does not lead to any defect. It is desirable not to allow porcelain to come in direct contact with a hard metal screw thread.

ISOLATORS

“Isolator" is one, which can break and make an electric circuit in no load condition. These are normally used in various circuits for the purposes of Isolation of a certain portion when required for maintenance etc. Isolation of a certain portion when required for maintenance etc. "Switching Isolators" are capable of
• Interrupting transformer magnetized currents
• Interrupting line charging current
• Load transfer switching

CIRCUIT BREAKER

The function of relays and circuit breakers in the operation of a power system is to prevent or limit damage during faults or overloads, and to minimize their effect on the remainder of the system. This is accomplished by dividing the system into protective zones separated by circuit breakers. During a fault, the zone which includes the faulted apparatus is de-energized and disconnected from the system. In addition to its protective function, a circuit breaker is also used for circuit switching under normal conditions.
Each having its protective relays for determining the existence of a fault in that zone and having circuit breakers for disconnecting that zone from the system. It is desirable to restrict the amount of system disconnected by a given fault; as for example to a single transformer, line section, machine, or bus section. However, economic considerations frequently limit the number of circuit breakers to those required for normal operation and some compromises result in the relay protection.
Some of the manufacturers are ABB, AREVA, Cutler-Hammer (Eaton), Mitsubishi Electric, Pennsylvania Breaker, Schneider Electric, Siemens, Toshiba, Končar HVS and others.
Circuit breaker can be classified as "live tank", where the enclosure that contains the breaking mechanism is at line potential, or dead tank with the enclosure at earth potential. High-voltage AC circuit breakers are routinely available with ratings up to 765,000 volts.

Reference: http://studentbank.in/report-a-practical...z4IVz6xnMf