Line Arresters to increase line utilization - w5.siemens.com - 2019-03... · Voltage builds up...

Line Arresters to increase line utilization Innovation for compact & cost-efficient lightning-proof transmission lines -

Unique solutions that combine composite insulators and line arresters

Florent Giraudet, Dirk Helbig

Siemens Customer Conference; Poiana Brasov, 13.-14. March 2019

siemens.com/energy/insulators © Siemens AG 2019

© Siemens AG 2019

siemens.com Siemens Customer Conference, Poiana Brasov, 13.-14. March 2019

Surge Arresters: One technology, 2 different purposes

Surge arresters protect valuable equipment

from damage due to transient overvoltages

Surge arresters improve lightning

performance by reducing outages

© Siemens AG 2019


Mitigation measures of lightning performance improvement

Increasing BIL

Additional Shield Wires

Footing resistance improvement

LSA application Cost-efficient

Back-flashover is when the lightning strokes

hit the shielding wire or the tower top

Direct flashover is when the lightning

strokes directly hit the phase conductor

© Siemens AG 2019


Our offer: Line condition studies

Lightning simulation for protection effectiveness

The effectiveness of line arresters strongly depends on the protection configuration selected.

Study LSA Remarks LSA

Qty

BFR Back-Flashover

Rate

1 No Maximum flashover rates since L1,L2 and L3

are unprotected 0 2,030

2 L1/L2/L3 LSA in section 2 / 4 / 6 / 8 / 10 204 0,146

3 All phases LSA partly in section 6 /10 on 34 towers 204 0,360

4 L2/L3/L6 LSA in section 2 / 4 / 6 / 8 / 10 204 0,016

© Siemens AG 2019


EGLA vs. NGLA

Line

Ground lead

Insulator

Line conductor

Ground terminal

Active

part*

GAP

EGLA (Externally Gapped Line Arrester)

NGLA (Non Gapped Line Arrester)

* The active part of an EGLA is called

SVU (Series Varistor Unit).

It’s directly connected to the line!

Active part

It’s disconnected from the line by the GAP!

EGLA =

+

Disconnector

Preference for EGLA design

+ Less material required due to lightning

protection only and not continuously energized

+ No leakage current, no Electrical stress, better

ageing, longer life expectancy

+ No lead / no disconnector. Leads to less

mechanical issues. More options for live

installation

+ Cannot fail due to line fault

+ No maintenance/monitoring required

– Energy not evenly shared. Insulation co-

ordination is more challenging

– Specific design for each situation needed, i.e. for

different tower / insulator strings / conductor

designs. Retrofit is more challenging than new

projects

© Siemens AG 2019


Externally Gapped Line Arresters (EGLA)

Sequence of events in EGLA surge protection

1. Surge travels down the line to the insulator

2. Voltage builds up across the EGLA gap and

across the insulator

3. Since the EGLA gap is smaller than the insulator

strike distance the EGLA gap flashes over

4. The varistors in the SVU immediately conduct

and transfer the surge charge to ground

5. Once the charge is depleted and the current is

reduced to milliamps, the gap interrupts and all

current flow ends

The surge event is over, there is no fault current

and no breaker operation.

Series Varistor Unit (SVU)

= surge arrester

The SVU will extinguish the arc

in less than 10 ms (half-cycle).

The follow current will be limited

to a maximum of 2A within 10ms

after lightning discharge

occurred.

Spark gap

© Siemens AG 2019


EGLA References – 3EV series

245 kV – RTE, France

63 kV – RTE, France 420 kV – CLP, Hong Kong

354 kV – KEPCO, South Korea

220 kV – Nextbridge, Canada

110 kV – EGAT, Thailand

© Siemens AG 2019


EGLA type testing IEC 60099-8 High-voltage laboratories in Berlin, Germany

EGLA withstand test

with failed SVU

Follow current

interrupting test

Short circuit test

Vibration test

Standard lightning impulse sparkover test

© Siemens AG 2019


New lines: Early integration at design stage

• No additional costs for installation or

power interruption

• No unnecessary hardware, counterweight

or support

• No moving parts / robust design

• Stable gap distance

• Does not influence regular line inspection

& maintenance

• If SVU is grounded only, replacement can

easily be done in live condition

• Cost-effective lightning performance

EGLA 500kV in V-string

configuration

© Siemens AG 2019


Retrofit application might require additional hardware …

… or not !

Cambodia/Thailand

230kV Malaysia

132kV

© Siemens AG 2019


Various benefits for line surge arrester application

Overview

* disconnects the AR from power line in case of AR-overload

Lightning performance improvement

•Reduce outages due to poor grounding / high lightning activity

•Double-circuit outage reduction / Underbuilt distribution lines

Switching surge control - structure optimization / lower clearances

Safety concerns - Prevent population injury & equipment damages

Line uprating and compaction – reduced insulation levels

Live line working - temporarily reduce minimum approach distance

Lowering costs and losses in your system

© Siemens AG 2019


Line uprating

Um = 50 kV Um = 123 kV

10

75

mm

EGLA solution

Um = 123 kV

Length: 1075 mm

1600 m

m

10

75

mm

48% section increase

- Might be not approved by public authorities

- Can take 5-10 years for approval

EGLA (Externally

Gapped Line Arrester)

Conservative

approach

Same section length !

100% lightning proof !

© Siemens AG 2019


Line compaction: Operate 420 kV with 245 kV ratings

1) Determination of the switching surge factor

• Results from SIGMA SET simulation of the surge factors by

the reclosing operation for a 420 kV line of 100 km.

• 1,8 p.u: with station arresters Ur=336 kV

2) Determination of the EGLA spark gap distance

U10%, EGLA =1,8pU*(1+1,3*Sigma(0,06))***

=1,8 pU * 1,078 = 1,94 p.U. 664 kV

***EGLA IEC 60099-8 Safety factor 7,8% 664 1360 2100

• 30% more compact than a

standard 420kV string

• 2100 mm arcing distance for a

standard 245 kV string

• fulfill IEC 60815 (25mm/kV

10500mm creepage),

• 100% lightning-proof

© Siemens AG 2019


Product overview: Composite Insulators

Long Rod Insulators for Overhead Transmission Lines

Sy

ste

m v

olt

ag

e

72.5 kV

245 kV

420 kV

550 kV

36 kV

100 kN 120 kN 160 kN 210 kN 240 kN 300 kN

400 kN & 500 kN

145 kV

70 kN

3FL2

Mechanical classes, SML

3FL5 3FL6 3FL3 3FL4

3FL7

550 kN 630 kN

3FL9 3FL8

Recent development

© Siemens AG 2019


Product overview: Composite Insulators

Long Rod Insulators for Overhead Transmission Lines

Long rod insulators (3FL)

IEC 61109 / ANSI C29.11 / CSA C411.4

One-piece housing: HTV silicone coating and weather-sheds

are made of one shot injection

Overmoulding system: no additional sealing necessary

• Triple point is totally enclosed by the silicone housing

One-piece design:

without overmoulding system.

One-piece design with overmoulding system

Metal end-fittings Forged steel – Hot dip galvanized

Sealing system preferred: Triple point is sealed with Wacker Silgel 612

• Better performance under step front impulses (tracking & erosion) • Inspection on site becomes easier in case of erosion (triple point)

• Silgel 612 maintains its properties at very low temperatures (-50°C) • 100% routine tested to prevent rod cracking

E-CR Core Rod Electrical-Corrosion Resistant Fibre

Reinforced epoxy resin Plastic

© Siemens AG 2019


Contact information

Siemens AG

Energy Management

High-voltage products

Dirk Helbig

Florent Giraudet

Technical Sales

Nonnendammallee 104

13629 Berlin, Germany

Phone: +49 1622 83 93 05

E-mail: [email protected]

siemens.com/energy/insulators

mailto:[email protected]

Line Arresters to increase line utilization - w5.siemens.com - 2019-03... · Voltage builds up...

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