Overall view of 220kv switch yard


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Overall view of 220kv switch yard at Dr.NTTPS presentation by Syed.Safiuddin A.Surendra B.Gurumurthy G.Hari krishna B.Vineel : 

Overall view of 220kv switch yard at Dr.NTTPS presentation by Syed.Safiuddin A.Surendra B.Gurumurthy G.Hari krishna B.Vineel


INTRODUCTION: Types of switch yards Gas insulated switch yards Air insulated switch yards Receives electrical power from 6x210 MW and other inflows like K’kota and LANCO(200MW) via incoming transmission lines. Delivers electrical power via outgoing transmission lines to various substations namely these are

Slide 3: 

Podili (2nos) Rentachintala, Tallapalli, Nunna, Tadikonda (2nos), kondapalli(2nos), Gundadala, Narketpalli and Chilakallu

Tasks of switch yard: : 

Tasks of switch yard: Protection of transmission system. Controlling the exchange of power. Maintain the system frequency within the targeted levels. Determination of power transfer through transmission lines. Fault analysis and subsequent improvements. Communication.

Equipments in the switch yard: : 

Equipments in the switch yard: Insulators Conductors and Accessories Clamps and Connectors Circuit breakers Isolators Earthing switch Instrument transformers Surge arrestors Wave traps

The whole layout of switch yard at Dr.NTTPS: : 

The whole layout of switch yard at Dr.NTTPS:

Bus Bar: : 

Bus Bar: The flow of electrical power between incoming and outgoing circuits takes place through the bus bars. These are junction points carrying huge power’ These are copper rods or thin walled tubes operating at constant voltage.

EHV Bus bar arrangements: : 

EHV Bus bar arrangements: Single bus bar. Single sectionalized bus bar. Double bus bar. Main and transfer bus arrangement. Duplicate bus bar arrangement. Three bus system: double and transfer bus. Breaker and half system.

Single bus bar arrangement: : 

Single bus bar arrangement: It is used for 132kv substations. It is cheapest and simplest in design. Disadvantages: The bus bar cannot be repaired or tested with out de-energizing the whole system. If fault occurs on the bus bar itself,there is complete interruption of supply.

Single sectionalized bus bar: : 

Single sectionalized bus bar: It is used in large generating stations where several units are installed. The bus bar is divided in to two sections connected by a circuit breaker. If fault occurs on any section of the bus bar, that section is isolated without affecting the supply to other sections.

Double bus bar arrangement: : 

Double bus bar arrangement: This system is costlier than a single bus bar system. One bus can be serves as a reserve, which is used during the maintenance or fault conditions’ It is used for 220kv sub stations.

Double bus bar with transfer bus: : 

Double bus bar with transfer bus: This system has additional flexibility for operation. We can shut down on breaker without interrupting the transmission line. It is used for critical 220kv sub stations.

One and half bus system: : 

One and half bus system: In this system three breakers are used for two circuits. The loads are automatically transferred to healthy bus from faulty bus without interruption of circuit. It is important for 400kv sub stations where higher flexibility is required.

Insulators: : 

Insulators: These provides necessary insulation between line conductors and supports and thus prevent the leakage of current from conductors to earth. Materials used for insulators: Ceramic(porcelain,steatite) Glass Synthetic resins.

Properties of insulators: : 

Properties of insulators: High electrical resistance. High mechanical strength to with stand conductor load, wind load etc., High relative permittivity of insulator material. It should be non porous and free from impurities and cracks. High ratio of puncture strength to flash over.

Types of insulators: : 

Types of insulators: Suspension type insulators. Pin type insulators.

Conductor and Accessories: : 

Conductor and Accessories: Conductor consists of several strands wound in layers spiraled along the length of conductor. The total number of individual strands “N” is given by N=3n^2+3n+1 where n=no of layers Diameter of conductor=(2n+1)*d where ‘d’ is diameter of strand’ The conductors used are: AAAC – All Aluminium Alloy conductor ACSR – Aluminium conductor steel reinforced AACSR- Aluminium alloy conductor steel reinforced

Clamps and Connectors: : 

Clamps and Connectors:

Circuit Breakers: : 

Circuit Breakers: These are switching devices, design to close or open an electrical circuit under normal or abnormal conditions. Types based on interrupting medium; Air blast circuit breaker Air break circuit breaker Bulk oil circuit breaker Minimum oil circuit breaker SF6 circuit breaker Vacuum circuit breaker

Slide 20: 

Types of operating mechanisms: Spring operating mechanism Pneumatic operating mechanism Hydraulic operating mechanism Pneumo spring mechanism 245kv, type 200-SFM-40A, CGL make SF6 gas circuit breaker: Features: Superior interrupting capability Low operation noise Simple construction and compact size Easy installation and maintenance High safety

Slide 21: 

Cross section interrupting unit:

Technical particulars of 220kv circuit breakers: : 

Technical particulars of 220kv circuit breakers: Make :CGL 1. Applicable technical standards :IEC-56/1997 2. Rated Voltage (RMS) :245 KV 3. Rated Frequency :50Hz 4. Number of poles per breaker : 3 5. Class (out door/indoor) :Out door 6. Rated normal current :2500 A 7. Rated short circuit breaking current a) RMS value of AC component :40 KA b) Percentage of DC component :50 % c) Asymmetrical breaking current :49 KA ( including DC component ) 8. Short time current rating for 3sec (RMS) :40KA 9. a)Rated short circuit making current (peak) :100KA b)Rated short circuit breaking current :40 KA 10. Rated out of phase breaking current :10 KA 11. Rated operating sequence :0-0.3sec-CO-3min-CO Operating mechanism :Motor wound spring 12. Type of closing mechanism :Spring 13. Type of tripping mechanism :Spring 14. A) Total creep age distance to ground. :7595 mm b) Creep age factor for the porcelains :Equal to or less than 4 c) Profile factor for the porcelains :Above 0.7

Slide 23: 

Instrument Transformer: Transformers used in conjunction with measuring instrument. These are used for measuring voltage and current in electrical power systems and for power system protection and control. Types: Current Transformer Potential Transformer

Current Transformer : 

Current Transformer Used for measuring high value currents. Designed to provide a current in its secondary coil proportional to current flowing in its primary coil. Primary winding consists of very few turns. Secondary winding consists of large no. of turns. Current to be measured is passes through primary winding.

Out look of C.T: : 

Out look of C.T: Primary current is dependent upon the load connected to the system. Secondary winding is short circuited with the help of an ammeter. It steps down the current to level of ammeter. Secondary winding is nearly short circuited.

Slide 26: 

Secondary winding consists of more no. of cores. One is used for metering purpose and other cores are protection purpose. In metering core the fault current is measured so secondary current rating is more.

Potential Transformer: : 

Potential Transformer: Used for the measurement of high voltages. Primary winding is connected to voltage to be measured. Voltmeter is connected across the secondary winding.

Slide 28: 

The design of potential transformer is quite similar to that of power transformer. The normal secondary voltage rating is 110v. The output of a potential is always small and the size is quite large. The core may be of shell or core type of construction

Protection of potential transformers: : 

Protection of potential transformers: It can be continuously operated at 1.2 times the rated voltage. Short circuit on the secondary side of a potential transformer can lead to complete damage of the transformer. Fuses are used in the secondary side to protect the P.T. against faulty switching and defective earthing.

Surge arrestor: : 

Surge arrestor: It is a protective device which conducts the high voltage surges on the power systems to the ground. Types : Rod gap arrestor Horn gap arrestor Multi gap arrestor Expulsion type arrestor Valve type arrestor

Slide 31: 

Basic construction: It consists of a spark gap in series with a non linear resistor. One end of the arrestor is connected to the equipment to be protected and other end is effectively grounded. The length of gap is set that normal line voltage is not enough to cause an arc. The property of the non linear is that its resistance decreases as the voltage increases and vice versa.

Metal oxide surge arrestor: : 

Metal oxide surge arrestor: It is also known as the zinc oxide surge arrestor. It is well accepted as voltage clippers for effective protection against over voltages. It protects the costly outdoor electrical equipments from over voltages. The striking aspect of this arrestor is its simplicity of construction.

Features: : 

Features: Higher duty capability. Better protection level. Superior performance against pollution. Excellent energy dissipation capability. High surge stability. High thermal stability.

Conclusion: : 

Conclusion: This project OVERALL VIEW OF 220KV SWITCH YARD IN Dr.NTTPS is constructed in such a way that every one understand about the construction and working of 220 kv switch yards and its equipments.

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