EHV Transmission Equipments C K Thakur Chief Design

EHV Transmission Equipments C. K. Thakur Chief Design Engineer (Project Engineering Electrical) NTPC

Over view n n n 5/21/2021 Switching Schemes. Type of Towers. Type of conductors. Switchyard types. Switchyard equipments. Switchyard Layouts. 2

Switching schemes n n n 5/21/2021 Single bus. Main and Transfer (sectionalised). Double bus. One and half breaker scheme. Double main and Transfer (Sectionalised). Double Breaker 3

Factors Affecting Switching Scheme System Security/Reliability. - Feeder Fault. - Bus Fault. - Equipment Failure. - Redundancy. n 5/21/2021 4

Factors Affecting Switching Scheme (Contd. ) n n n 5/21/2021 Operational Flexibility. Ease of Maintenance. Simplicity of Protection Arrangements. Ease of Extension. Area available. Cost. 5

Line Towers n n n 5/21/2021 Single Circuit. Double Circuit. Dead end type. Tension Towers. Suspension Towers. 6

Tower Design n n 5/21/2021 Wind Force. Conductor Tension. Span. Type of conductor. 7

Tower Hardwares n n 5/21/2021 Insulator Strings. Vibration Dampers. Spacers. Earthwire & OPGW. 8

Type of Conductor n n 5/21/2021 ACSR Moose (800 A). Zebra (700 A). Rabbit (190 A). Dog (290 A). 9

Switchyard Type n n n 5/21/2021 Conventional Air Insulated Type. Gas Insulated type. Air Insulated (Enclosed type). 10

Switchyard Equipments. n n n n 5/21/2021 Circuit Breaker. Disconnectors. Current Transformers. Capacitor Voltage Transformers. Lightning Arrestors. Post Insulators. Wave Traps 11

General Parameters Dielectric Parameters. (IEC 694) - Power Frequency Voltage. - Lightning Impulse Voltage. - Switching Impulse Voltage. - Corona Extinction Voltage. - RIV Level. n 5/21/2021 12

400 k. V Equipments 5/21/2021 13

220 k. V Equipments 5/21/2021 14

132 k. V Equipments 5/21/2021 15

General Parameters (Contd. ) n n n 5/21/2021 Rated Current. Short Time Current. Creepage Distance. 16

Circuit Breakers Type n n n 5/21/2021 MOCB. ABCB. SF 6 17

Circuit Breaker n n n n 5/21/2021 Fault clearing. Load Make Break Time. Single/Multi Break. Voltage Distribution across breaks. Closing resistors. Operating mechanism (Spring/Pneumatic/Hydraulic) 18

Disconnectors n n n n 5/21/2021 HCB Type. Double Break Type. Pantograph type. Vertical Break type. Provision of Earth Switches. Motor / Pneumatic operated. Gang operated/Single pole type. 19

Current Transformer n n n 5/21/2021 Bar Primary type. Dead tank/Live tank type. Ring Type. No. of Cores. Ratio. Accuracy. 20

Capacitor Voltage Transformer n n 5/21/2021 Capacitance. Voltage Ratio. No. Of Cores. Accuracy. 21

Lightning Arrestor n n n 5/21/2021 Gap Type / Gapless Type. Voltage Rating. Energy Capability. Monitoring. Location. 22

Post Insulators n n n 5/21/2021 Voltage Rating. Cantilever Strength. Fixing Details. 23

Wave Trap n n 5/21/2021 Rated Inductance(0. 5/1. 0 m. H). Rated current. Band Width. Coupling (Phase to Phase). 24

Switchyard Layout Guidelines n n 5/21/2021 Place All Equpt. At ground level for ease of maintenance. Busbars placed at right angles to feeders. Accessibility of feeders from either side of switchyard. Conductor crossings at right angles be separated to achieve adequate clearances. 25

Switchyard Layout Guidelines(Contd. ) n For 400 k. V - Phase to Phase 4000 mm - Phase to earth 3500 mm n For 220 k. V - Phase to Phase 2100 mm - Phase to earth 2100 mm 5/21/2021 26

Switchyard Layout Guidelines(Contd. ) n n 5/21/2021 Lower level connections can be of Rigid pipe or flexible conductor. Upper level connections can be of strung type only. For aesthetic looks and similarity all same equipments be in one line as far as possible. Road near circuit breaker be kept for maintenance purpose. 27

Switchyard Layout Guidelines(Contd. ) n n 5/21/2021 Provide Double insulator strings for upper level for safety reasons and to avoid busfaults due to conductor snapping. Cable trenches to be routed for ease in maintenance and movement. Lightning protection to be provided using Lightning masts and/or shield wires. Lighting to be provided by fixtures on 28 LM platform.