0811013106

7/27/2019 0811013106

1/34

Presented By

JANMEJAYA MISHRA

7/27/2019 0811013106

2/34

OF

HVDC TRANSMISSION

7/27/2019 0811013106

3/34

Introduction to HVDC transmissionAC Generation and Transmission

Advantages of HVDC

Principles of AC /DC Transmission

Thyristor Evolution

Conversion principles

Analysis of 12 pulse bridge

Operation of HVDC

Types of HVDC

Salient features of Talcher-Kolar HVDC

7/27/2019 0811013106

4/34

Due to ease of transformation of voltage levels (simple

transformer action) and rugged squirrel cage motors,ALTERNATING CURRENT is universally utilized.

Both for GENERATION and LOADS and hence for

TRANSMISSION.

Generators are at remote places, away from thepopulated areas i.e. the load centers

They are either PIT HEAD THERMAL or HYDEL

Turbines drive synchronous generators giving an

output at 15-25 kV.

Voltage is boosted up to 220 or 400 KV by step-up

transformers for transmission to LOADS.

To reach the loads at homes/industry at required safe

levels, transformers step down voltage.

REASONS FOR AC GENERATION AND TRANSMISSION

7/27/2019 0811013106

5/34

ADVANTAGES OF HVDC OVER HVAC TRANSMISSION

HVDC can be built in stages: Monopolar line with

ground return initially can be converted into bipolar line when load increases.

No skin effect and proximity effect no corona effect and no radio interference in

HVDC.

Less conductors required so less transmission loss and low cost of installationin

HVDC transmission.

Since DC current in HVDC no inductance hence no inductive voltage drop implies

better voltage regulation.

7/27/2019 0811013106

6/34


HVDC transmission has lesser dielectric power losshence has high current carrying

capacity.

Independence of frequencies of sending-end and receiving-end networks in HVDC

makes possible to generate in one frequency and utilize in some other frequency.

In HVAC there is limit on length of cable depending upon the rated voltage due to the

presence of charging current. For evidence about 60 km for 145 kV 40 km

for 245 kV and 25 km for 400kV line transmission.

High operating voltagescan be employed in HVDC.

7/27/2019 0811013106

7/34

Terminal Cost AC

Terminal Cost DC

Line Cost DC

Line Cost AC

Break Even Distance

7/27/2019 0811013106

8/34


CHEAPER THAN HVAC SYSTEM DUE TO LESS

TRANSMISSION LINES & LESS RIGHT OF WAY FOR THE

SAME AMOUNT OF POWER TRANSMISSION

7/27/2019 0811013106

9/34

HVDC BIPOLAR TRANSMISSION SYSTEM

2 DOUBLE CIRCUIT HVAC TRANSMISSION SYSTEMS

2000 MW HVDC VIS- A- VIS HVAC SYSTEMS

7/27/2019 0811013106

10/34

7/27/2019 0811013106

11/34

7/27/2019 0811013106

12/34

HVDC is the unique solution to interconnect

asynchronous systems or grids with different

frequencies.

Solution: HVDC Back-to-Back

Up to 600 MW

Back-to-Back Station

AC AC

50 Hz 60 Hz

7/27/2019 0811013106

13/34

HVDC represents the most economical

solution to transmit electrical energy over

distances greater than approx. 600 km

Solution: HVDC Long Distance

Up to 3000 MW

Long Distance Transmission

AC AC

DC line

7/27/2019 0811013106

14/34

HVDC is an alternative for submarine transmission.

Economical even for shorter distances such as a few

10km/miles

Solution: HVDC Cable

Up to 600 MW

Long Submarine Transmission

AC AC

DC cable

7/27/2019 0811013106

15/34

HVDC BIPOLAR LINKS IN INDIA

NER

ER

SR

NRNER

ER

SR

NR

RIHAND-DELHI -- 2*750 MW

CHANDRAPUR-PADGE2* 750 MW

TALCHER-KOLAR 2*1000 MW

ER TO SR

EXPERIMENTAL PROJECT

ER

SR

7/27/2019 0811013106

16/34

HVDC LINK CONNECTING

REGION

CAPACITY

(MW)

LINE

LENGTH

Rihand Dadri

North-North 1500 815

Chandrapur -

Padge

West - West 1500 752

Talcher

Kolar

East South 2500 1367

7/27/2019 0811013106

17/34

7/27/2019 0811013106

18/34

Since our primary source of power is A.C,

the following are the basic steps:

1. CONVERT AC into DC (rectifier)

2. TRANSMIT DC

3. CONVERT DC into AC ( inverter)

This has been possible with advent of

High power/ high current capability thyristors,

IGBTs and GTOs

Fast acting computerized controls

7/27/2019 0811013106

19/34

THYRISTOR VALVE

7/27/2019 0811013106

20/34

Connects AC phases to DC system

Conduct High Current currents upto 3000A without therequirement of paralleling of thyristors

Block High Voltage

Blocks high voltage in forward and reversedirection up to 8 to 10 kV

Controllablethyristor triggering /conduction possible with thegate firing circuits

Fault tolerant and robust

7/27/2019 0811013106

21/34

3

6

CiLs

4

E1 Ls

Ls

Bi

iA

1

2

I

V'd

5

Vd

IddL

d

7/27/2019 0811013106

22/34

Each thyristor conducts for 120

Every 60 one Thyristor from +ve limb and one Thyristorfromve limb is triggered

Each thyristor will be triggered when voltage across itbecomes positive

Thyristor commutates the current automatically when the

voltage across it becomes

ve. Hence, this process is callednatural commutation and the converters are called LineCommutated converters

7/27/2019 0811013106

23/34

Commonly Used in HVDC systems

7/27/2019 0811013106

24/34

Commonly adopted in all HVDC applications

Two 6 pulse bridges connected in series

30 phase shift between Star and Delta

windings of the converter transformer

Due to this phase shift, 5thand 7thharmonicsare reduced and filtering higher order

harmonics is easier Higher pulse number than 12 is not

economical

7/27/2019 0811013106

25/34

I R

DC CABLE or O/H LINE

I Ed rd

RECTIFIER

dio RV

I X2

d c

cos

rI Ed

L I X

2

d c

cos

VdioI

INVERTER

VdR=VdioR cos-Id Xc+Er VdI=VdioI(cos-Id Xc+Er

2 2

7/27/2019 0811013106

26/34

V 1 V 3 V 5

V 2V 6V 4

Phase A

Ud

Phase B

Phase C

Id

Power FlowAC System DC System

V 1 V 3 V 5

V 2V 6V 4

Phase A

Ud

Phase B

Phase C

Id

AC System DC SystemPower Flow

30 60 90 120 150 180

0

+Ud

-Ud

160

5

Rectifier

Operation

Inverter

Operation

Rectifier Operation Inverter Operation

7/27/2019 0811013106

27/34

7/27/2019 0811013106

28/34

DC OH Line

Converter

Transformer

Thyristor

Valves

400 kVAC Bus

AC Filters,Reactors

Smoothing Reactor

Converter

Transformer

Thyristor

Valves

400 kVAC Bus

AC Filters, shuntcapacitors

Smoothing Reactor

Bipolar

Current

Current

7/27/2019 0811013106

29/34

DC OH Line

Converter

Transformer

Thyristor

Valves

400 kVAC Bus

AC Filters,Reactors

Smoothing Reactor

Converter

Transformer

Thyristor

Valves

400 kVAC Bus

AC Filters

Smoothing Reactor

Monopolar Ground Return

Current

7/27/2019 0811013106

30/34

DC OH Line

Converter

Transformer

Thyristor

Valves

400 kVAC Bus

AC Filters,Reactors

Smoothing Reactor

Converter

Transformer

Thyristor

Valves

400 kVAC Bus

AC Filters

Smoothing Reactor

Monopolar Metallic Return

Current

7/27/2019 0811013106

31/34

Kolar

Chintamani

Cudappah

HoodyHosur

Salem

Udumalpet

MadrasBlore

+/- 500 KV DC line

1370 KM

Electrode

StationElectrode

Station

TALCHER

400kv System

220kv system

KOLAR

7/27/2019 0811013106

32/34

TALCHER-KOLAR HVDC & EHVAC SYSTEM

7/27/2019 0811013106

33/34

Salient Features Rectifier Talcher, Orissa

Inverter Kolar, Karnataka

Distance

1370 km

Rated Power 2000 MW

Operating Voltage 500 kV DC

Reduced Voltage 400 kV DC

Overload

Two Hour, 50C 1.1 pu per pole

Two Hour, 33

C 1.2 pu per pole Half an hour, 50/33C 1.2/1.3 pu per pole

Five Seconds 1.47 pu per pole

To be upgraded to 2500MW

7/27/2019 0811013106

34/34

Presented By

JANMEJAYA MISHRA

0811013106 (ELE-A)

Documents

0811013106