Department of High-Voltage Engineering

JSC «NIIPT» Vladimirskii L.L.

The development of the HVDC systems in Russia

The evolution of HVDC transmission lines in Russia

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kV 750

600

500

250

700

400

300

100

1890 1950 1962 1990 2017 2025

± 750 kV transmission line - Ekibaztus - Centre ( 6000 MW , 2400 km )

( planning project , construction of 120 km line operating

without voltage )

Ural-Srednyaya ± 750 kV Volga - Centre

3000 MW, 1850 km,

(

planning project )

± 300 kV LAES-Vyborg ( 1000 MW , 110 km )

( )

± Kashira-Moscow ( 30 MW , 112 km )

± 400 kV Volgograd-Donbass -

( 720 MW , 473 km )

Experience of launching HVDC projects in Russia

transmission line

transmission line

transmission line planning project

cable line 100 kV

Field experiments Span of the pilot ± 400 kV DC line

NIIPT, 1956-1957.

± 400 кВ Volgograd-Donbass HVDC line, 1962.

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Field experiments

Span of pilot DC OH line ±750 kV, «NIIPT», 1980

DC OH line 750 kV Ekibaztuz – Center, 1990

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Selection of the main structural elements of the HVDC transmission line based on the expected

weather conditions along the line route

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•Line isolation (the contamination level)

•The air gaps in the insulation support and in the middle of the span (velocity head wind)

•The design of the pole (sleet load)

•Lightning protection system (storm activity in the area of the line route)

•The type and structure of the supports (wind speed, air temperature, ice thickness)

Selection of line insulation

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Determining of pollution degree

Choosing isolation levels - the specific creepage

distance

Select the type of insulation and insulation configuration details for the specific conditions of

pollution

The choice of design of link suspension

Operating voltage in conjunction with polluted and wet insulator

Selection of insulating air gaps in the support and the dimensions to the ground

Design conditions determining the size of air gaps that define the geometry of the supports

Gap Design condition

Vertical spacing "wire-traverse

support"

The length of insulating string, chosen for normal operating conditions, i.e., the effects of operating voltage in conjunction with a polluted and wet insulator surface

Horizontal gap "wire-support"

Maximum operating voltage taking into account crosswind insulating string deviation; the impact of switching surges (K = 1.8-2.0) at design wind pressure; safe operation of a support under voltage

The gap between the pole wires in the

span

Maximum operating voltage, overhead line design parameters and climatic conditions (dancing and whipping of the wires)

Gap "wire-to-ground" in the span

Switching overvoltages, environmental requirements and the electric field intensity under the line at an operating voltage

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Selection of lightning protection system

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Specific features of HVDC line: • Lightning-proof bipolar HVDC line ensured by the rope

protection • Lightning in 90% of cases is negative, so the isolation of the

positive pole is subject to a large extent overlap • Reverse overlap during impact to support only occurs at the

positive pole • Bipolar overlap from lightning strikes are virtually

eliminated

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Selection of the wires and assessment of the impact of HVDC line on the environment

The possibility of using a smaller number of components in the larger cross-section of each wire in comparison with the HVAC EM ≤ 0,9 Е0 where EM - the maximum electric field intensity on the surface of the wires, Е0 – total corona inception voltage at a constant voltage higher than AC one

Requirement for the economic current density A limitation of the corona Ensure of an acceptable levels of interference The mechanical strength of the wires

Pole design

Electric field intensity

on the surface of constituent wires in the pole EM

Minimum cross-section

of the pole is determined

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Assessing the impact of HVDC overhead line on the environment

The main factors of biological influence of the HVDC line

For bipolar HVDC overhead line it is recommended for the maximum permissible values:

Eз = 30÷40 kV/m – the electric field intensity at the surface of the earth;

jmax ≤ 100 nА/m2 – an ion current density in the ground;

n ≤ 3⋅105 cm-3 – on concentration at the ground surface at jmax

Electric field

The electric field at the surface Egr, kV/ m

Unipolar ion currents flowing on the ground

Increase the concentration of positive and negative ions at

the surface

Contribute to the accumulation of electrical

charges in the isolated large objects

Line range as part of the projected Federal Test Centre (FTC)

To create a modern HVDC lines as part of FTC it is created a line range consisting of:

experimental HVDC line(± 800 kV) experimental HVAC line (1000 kV) complex high-voltage test systems (DC, AC and pulse voltage) Laboratory for testing of external insulation of electrical installations

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The main options for increasing the transfer capacity of overhead lines

1. Substitution on aged wires similar new ones

2. Increasing the voltage of overhead lines

3. Increasing the load current by increasing wire size or by increasing the temperature of the wires

4. Construction of a second extra overhead line or double circuit overhead line instead of single-circuit one

5. Conversion of overhead lines from AC to DC voltage with the ability to control the power flow, and reduce losses

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Translation of overhead lines from AC to DC voltage to increase transfer capacity

Converting of the 330 kV single-circuit AC overhead line with the phase of 2×АС 380/50 (Nigeria) to the bipolar ± 500 kV DC line with the pole of 3×АС 380/50

Converting of the 330 kV double-circuit AC line with the phase of 2×АС 380/50 (Nigeria) to the bipolar ± 500 kV DC line with the pole of 3×АС 380/50

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Analysis of the possibility of line converting from the AC to DC voltage

The main parameters of 220 kV line •Rated voltage -220 kV •Nominal transfer capacity - 240 MVA •Actual transfer capacity- 160 MVA •Operation life - 50 years •Type of intermediate support PMT – 220 •The length of the span - 350 m •The existing linear insulation:

14хП-7 (238 cm building height ) 14хП-4,5 (234 cm building height ) The length of the insulator set is about 300 cm

Design conditions: Pollution level– 1 The area to the wind– 3 The area to the ice– 4 Minimum temperature–minus 38 °С Maximum temperature– plus 40 °С Operating temperature– plus 5,2 °С

The need for increasing the transfer capacity in 2.5-3 times (400-480 MBA) in relation to the actual one (MVA 160)

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Selection of isolation levels and types of DC overhead line insulators

Level of external insulation - specific creepage distance λdc Pollution level – 1; λdc=1,6 sm/kV

λ𝑑𝑑𝑑𝑑 = λ𝑎𝑎𝑑𝑑 ∙ 3 ∙ 𝐾𝐾𝑑𝑑𝑑𝑑 ∙ 𝐾𝐾𝐿𝐿 ∙ 𝐾𝐾𝑘𝑘 Key features and sizes of single suspension insulators in the pole

suspension string

Type of insulator

Min

imum

m

echa

nica

l st

reng

th u

nder

te

nsio

n, k

N

Leak

age

path

le

ngth

, L И

, cm

Con

stru

ctio

n he

ight

НИ

, см

Dia

met

er,

d, c

m

Wei

ght,

kg

DFI 250 250 632,5 110-180 9,5

(body) 1,15 1,2 1 90,0

PSV 120 Б 120 44,5 12,7/14,6 28 1,1 1,3 1 5,66

PSV 160А 160 54,5 14,6/17,0 32 1,1 1,3 1 8,28

PSV 210 А 210 55,5 17,0/19,5 33 1,1 1,3 1 9,40

PSV 300 А 300 61,7 19,5/19,8 36 1,1 1,3 1 13,3 15

Construction length of DC overhead line insulator strings

Existing construction length of 220 kV line insulating string is 234-238 cm

Type of insulator

Uнр , kV

Leakage path length of the

insulating string, LГ, cm

Number of insulators in the chain, n

Construction height of the

insulating string, НГ(стр), cm

DFI 250 200 764 2 240 250 956 2 286 300 1146 2 332

PSV 120 Б 200 792 18 229 250 990 23 292 300 1188 27 343

PSV 160 А 200 792 15 219 250 990 19 278 300 1188 22 321

PSV 210 А 200 792 15 255 250 990 18 306 300 1188 22 374

PSV 300 А 200 792 13 254 250 990 16 312 300 1188 20 390

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Design condition Climatic conditions

The smallest insulation distance (cm) for air gaps on the support of the HV DC lines, depending on the rated voltage

±200 kV ±250 kV ±300 kV Lightning overvoltages Wind stress 50 Pa.

Tmperature +15°С. No ice

195 245 290

Internal overvoltages 170 215 255 Ensuring of safe lifting on the bar of support (without going to traverse) without turning off the overhead line

Temperature –15°С. No ice and wind 220 270 320

Operating voltage Maximum wind at – 5°С. No ice 80 90 100

Permissible values of air gaps on a support with an operating voltage of ± 200, ± 250 and ± 300 kV

An analysis of the dimensions of the PTM-220 support shows that it meets the requirements to the size of the air gaps for all of the options under consideration of the HVDC lines by voltage class, estimated climatic conditions and electrical requirements.

The minimum dimension to the ground in an uninhabited area at an operating voltage

of ± 200, ± 250 and ± 300 kV Controlling of the dimension to the ground on the biological impact:

The limits:

Electric field intensity at the ground surface : Eз = 30÷40 kV/m

The density of the ion current in the ground for population: jmax ≤ 100 nА/m2

Operating voltage ±200 kV ±250 kV ±300 kV

Dimension to the ground , м 7 7,5 8

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Selection of the electrical parameters of the HVDC line

Bipolar DC overhead line Increasing of the transfer capacity in 2,25-3 times relating to the current actual transfer capacity of the overhead AC line (160MVA): 360-480 MVA DC "pole-to-earth" voltage, versions: 200, 250, 300 kV Metallic current return

Electrical parameters of the HVDC line № п/п

Voltage,

kV

Transmission power,

MVA

Pole current,

А

Current density in the

wire, А/mm2

Cross-section of the pole,

mm2

Number of the wires in the pole and wire type

1 200 360 900

0,8/1,2

1125/750 2×АС600/1×АС750 2 200 480 1200 1500/1000 2×АС750/2×АС500 3 250 360 720 900/600 2×АС500/1×АС600 4 250 480 960 1200/800 2×АС600/1×АС800 5 300 360 600 750/500 2×АС400/1×АС500 6 300 480 800 1000/650 2×АС500/1×АС650

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Selection of the variants of HVDC line Voltage, kV

Current density, А/mm2

Pole construction Insulating string length,

m Transfer capacity is

480 MVA Transfer capacity is

360 MVA

200 0,8 2×АС750 2×АС600

2,4 1,2 2×АС500 1×АС750

250 0,8 2×АС600 2×АС500

2,8 1,2 1×АС800 1×АС600

300 0,8 2×АС500 2×АС400

3,3 1,2 1×АС670 1×АС500

Current density, А/mm2

Power, MVA Voltage, kV Pole

construction

Insulating string length,

m

1,2

480 300 1×АС650 3,3 Possible increasing of mechanical strength of the existing poles 360

300 1×АС500 3,3

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Proposals for the development of HVDC overhead lines in Russia

1. To organize an international scientific-technical conference of BRICS countries and other interested countries and organizations in the research, design, development and operation of the HVDC super- and ultra-high voltage lines in 2016 in Russia

2. To consider the strategy of development of the electric grid complex if the Russian Federation taking into account the construction of long-distance DC power lines of super- and ultra-high voltage, as well as rational use of translations of the HV AC to DC lines to increase transfer capacity

3. To perform a research on the selection of optimal translation variants of the HV AC to DC line in order to increase their transfer capacity to develop technical solutions for the overhead line and conversion terminal devices.

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