lca gis mv summary 1 2003

Solvay Fluor und Derivate

SF6-GIS-Technologyfor Power Distribution– Medium Voltage –Summary

L I F E C Y C L E A S S E S S M E N T

1 Pages

Life Cycle Assessment

SF6-GIS Technology for Power Distribution

– Medium-Voltage –

Summary

Author: Dr.-Ing. Ivo Mersiowsky Solvay Management Support — Life Cycle & Sustainability — Hannover, November 2003

Commissioned by:ABB

AREVA T&D (formerly: ALSTOM)EnBW Regional

e.on HanseRWE

SIEMENSSOLVAY Fluor und Derivate

SF6-GIS Technology for Power Distribution – Medium Voltage –

Page 2

Introduction

In autumn 2002, the German Ministry of the Environment published a policy paper

on the »Implementation of the National Climate Protection Programme regarding

Fluorinated Greenhouse Gases (HFC, FC, SF6)«. This policy paper addressed,

among other sectors, the use of SF6 in certain electrical switchgear, claiming appli-

cation of SF6 in medium-voltage switchgear to be dispensable and suggesting a

ban of SF6-insulated in favour of air-insulated medium-voltage switchgear.

Transmission and distribution losses account for approximately 4 % of the electric-

ity consumption in the public utility sector. Specific losses in the medium-voltage

range (MV, 1–52 kV) are higher than in the high-voltage range. This study investi-

gated 10 and 20 kV grids.

When analysing the contribution of electricity distribution grids to Germany’s

greenhouse gas emission burden (global warming potential), the largest share by

far arises from the ohmic losses of cables, lines, and transformers. To date, SF6

emissions from medium-voltage switchgear constitute less than 0.005 % of the

man-made greenhouse effect in Germany.

An earlier life cycle assessment (LCA) on high-voltage (HV) switchgear had shown

power supply systems using SF6-insulated switchgear to be advantageous or at

least competitive from an environmental point of view. The present LCA was com-

missioned by:

♦ Grid operators: EnBW Regional, e.on Hanse, and RWE;

♦ Equipment manufacturers: ABB, AREVA T&D (formerly: ALSTOM), and Sie-

mens;

♦ SF6 producer: Solvay Fluor und Derivate.

This LCA was conducted in accordance with ISO 14040–43 standards and in-

cluded stakeholder participation. The Critical Review according to ISO 14040 was

conducted by TÜV NORD CERT. The independent advisory board comprised:

♦ Zentralverband Elektrotechnik- und Elektronikindustrie ZVEI;

♦ Verband der Netzbetreiber VDN beim Verband der Elektrizitätswirtschaft

VDEW;

♦ Institut für Hochspannungstechnik IFHT an der RWTH Aachen;

♦ Umweltbundesamt UBA; Bundesministerium für Umwelt, Naturschutz und Re-

aktorsicherheit BMU.


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Goal and Scope

The goal and scope of the present study is to investigate the environmental profile

of power distribution in the medium-voltage range (Figure 1). This is accomplished

by life cycle assessment (LCA) of representative product mixes and grids in the

medium-voltage (MV) range, with a comparison between on the one hand air-

insulated switchgear (AIS) and on the other hand gas-insulated switchgear (GIS).

The prerequisite of applying LCA methods is that the systems under comparison

are functionally equivalent. In this case, the functional unit is the distribution of a

certain amount of electricity on the medium-voltage level during one year. Hence,

the comparison cannot be made switchgear by switchgear, but must rather en-

compass representative product mixes and grid designs.

Figure 1: Simplified scheme of electricity supply – transfer (high-voltage level, 110 kV and above) and distribution

(medium-voltage level, 10/20 kV).

Data Collection and Life Cycle Inventory

Investigated AIS and GIS Switchgear

Data were collected for a representative product mix of MV switchgear: transformer

substations, ring-main units (RMU), and consumer substations (Table 1). All se-

lected switchgear models are state of the art and representing standard user speci-

fications in accordance with relevant norms. The switchgear designs comply with

DIN EN 60694 Classification VDE 0670 Part 1000 and DIN EN 60298 Classifica-

tion VDE 0670 Part 6. All conduits and busbars were made of copper. In order to

examine equipment that is fully comparable and well-documented, only type-tested

switchgear were considered eligible for this LCA.


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Table 1: Investigated switchgear and their technical data

Type of Switchgear

Operating Voltage [kV]

Rated Current [A] Insulation Medium

Switching Medium1) (Arc-quenching)

12 1,250 Air Vacuum

12 1,250 SF6 Vacuum

24 1,250 Air Vacuum

Transformer Substation HV/MV

Single Busbar

24 1,250 SF6 Vacuum

12 2,000 Air Vacuum

12 2,000 SF6 Vacuum

24 1,250 Air Vacuum

Transformer Substation HV/MV

Double Busbar

24 1,250 SF6 Vacuum

12 630 Air Polymer2)

12 630 SF6 SF6

24 630 Air Polymer2)

Ring-Main Unit RMU

24 630 SF6 SF6

12 630 Air Polymer2) – Vacuum

12 630 SF6 SF6 – Vacuum

24 630 Air Polymer2) – Vacuum

Consumer Substation

24 630 SF6 SF6 – Vacuum

1) For consumer substations, arc-quenching media are given in the following order: switch – circuit breaker. 2) Polymeric arc-quenching medium, »hard-gas« principle.

Losses of electric power due to ohmic resistance were differentiated into constant

and load-dependent in order to facilitate a subsequent variation of load. The default

load of all switchgear was assumed to be 50 %. This was later on varied between a

minimum of 30 % (rural) and up to 80 % (urban).

Table 2: Investigated switchgear and their electrical data based upon calculations from single-line diagrams. Fig-ures were aggregated into ZVEI Product Mix according to Table 5.

ZVEI Product Mix

Variant AIS GIS

Type of Switchgear Trans-former

S/S

RMU Customer S/S

Trans-former

S/S

RMU Customer S/S

Ohmic Loss PL,50 W 2.347 7.763 2.093 1.801 5.321 2.089

Ohmic Loss PL,100 W 4.435 31.051 6.173 3.439 21.243 6.149

Ohmic Loss PL∗ W 1.656 0 733 1.256 0 733

Abbreviations: PL,50 — ohmic loss at 50 % load; PL,100 — ohmic loss at 100 % load (nominal current); PL∗ — constant ohmic loss

due to voltage transformers. RMU — ring-main unit. S/S — substation.

Ohmic resistance of each distinct part of switchgear were taken from type testing

documents. Single-line diagrams were used to determine actual flows of electric


Page 5

currents and calculate losses according to ohmic losses accordingly (Table 2). Cur-

rent and voltage transformers as well as fuses were appropriately considered.

Apart from electrical data, the survey also comprised amounts of material based

upon disassembly analysis by each equipment manufacturer (Table 3). Amounts of

concrete for buildings were calculated with an empirical formula based upon di-

mensions of the switchgear and required aisles.

Based upon operators’ experiences and expectations, the total lifecycle was as-

sumed to be 30 years for AIS, and 40 years for GIS. This assumption was supple-

mented by a variation between 30 and 50 years.

Table 3: Investigated switchgear and their material data based upon disassembly analysis. Figures were aggre-gated into ZVEI Product Mix according to Table 5.

ZVEI Product Mix

Variant AIS GIS

Type of Switchgear Trans-former

S/S

RMU Customer S/S

Trans-former

S/S

RMU Customer S/S

SF6 kg 0 0 0 248 159 56

Aluminium kg

Cast alloy kg 494 0 0 3,422 0 56

Wrought alloy kg 440 0 33 393 0 195

Copper kg 11,993 6,610 1,923 4,248 2,233 1,415

Steel kg

Steel kg 76,083 92,537 32,720 33,328 15,577 7,763

Electrical sheet kg 460 0 733 1,578 0 417

Polymers

Epoxy Resin kg 9,524 4,627 1,440 1,816 2,214 1,978

Thermoplastics kg 637 147 147 655 417 119

Polymer (arc-quenching)

kg 0 220 49 0 0 0

Concrete t 275 487 125 142 89 43

Ceramics kg 0 0 56 615 0 207

Abbreviations: RMU — ring-main unit. S/S — substation.

Investigated Product Mixes and Grids

The functional unit of power distribution requires that a certain product mix, i. e.

specific numbers of units from each type of switchgear, be considered. Two differ-

ent approaches for obtaining such representative product mixes were employed.

♦ Firstly, an average product mix was calculated based upon figures from a ZVEI

statistical survey of units sold in Germany. This covered the entire range of MV

switchgear equipment for utilities as well as industrial and infrastructure cus-


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tomers, both 10 and 20 kV. However, this did not allow a consideration of ca-

bles and lines in grids.

♦ Secondly, two sample utility distribution grids were designed, one for an urban

(10 kV, Figure 2) and one for a rural area (20 kV, Figure 3). These grids are

representative of Germany in that their topology was derived from a medium-

sized city. Based upon the grid design study, the lengths of cables and lines

were given (Table 4).

Table 4: Topology and quantity structures of sample urban and rural utility grids [ABB 2003]

Grid Rural Urban

Voltage / kV 20 10

Load / MW 25.3 36.1

Grid area / km² ≈ 51 ≈ 12

Load density / MW/km² 0.5 3.0

Ohmic losses per year / GWh/a 1.12 1.52

MV cable 150 mm²/ km 63.1 56.2

MV cable 240 mm²/ km 8.9 0

MV line 95 mm²/ km 34.8 0

Grid length / km 106.8 56.2

Number of transformer substations with double busbar 1 1

Number of bays, comprising –

Incoming/outgoing feeder Transformer feeder Bus coupler

13

10 2 1

23

20 2 1

Number of transformer substations with single busbar 1 0


Incoming/outgoing feeder Transformer feeder Bus sectionaliser

9

8 — 1

—

— — —

Number of ring-main units (RMU) with MV/LV transformers 116 132


Incoming/outgoing feeder Transformer feeder

348

247 118

396

264 135

Number of transformers HV/MV 2 2

Number of transformers MV/LV 118 135

Number of lines MS 10 20

Installed transformer electrical power rating HV/MV / MVA 80 80

Installed transformer electrical power rating MV/LV / MVA 26.6 56.7


Page 7

Figure 2: Topology of urban distribution grid [ABB 2003]

Figure 3: Topology of rural distribution grid [ABB 2003]


Page 8

For the two sample utility distribution grids, ohmic losses for cables and lines, and

for HV/MV transformers were computed from actual load and considered as con-

stant. Since the presupposition was an identical grid topology in case of AIS and

GIS equipment, this did not impinge upon the comparison. Conversely, medium- to

low-voltage (MV/LV) transformers were by definition beyond the system boundary

of MV power distribution; therefore, their substantial ohmic losses were not in-

cluded.

The two sample grids represent municipal utility structures, i. e. do not comprise

industrial grids connected by consumer substations. Therefore, RMUs are even

more abundant. Aside from the lack of industrial sub-grids, however, the quantity

structures of the two sample grids are sufficiently comparable with the ZVEI prod-

uct mix described above. Table 5 provides a comparative overview of all medium-

voltage product mixes thus obtained.

Table 5: Investigated product mixes for medium-voltage switchgear. ZVEI Product Mix is derived from ZVEI sta-tistical survey of medium-voltage units sold in Germany. Figures are units, normalised with reference to one double-busbar transformer substation 24 kV. Figures for urban and rural utility grids are derived from representative topology and grid planning, cf. Figure 2 and Figure 3, respectively [ABB 2003]. Types of switchgear are specified in Table 1.

Type of Switchgear ZVEI Product Mix Urban Grid (Utility) Rural Grid (Utility)

Transformer S/S, Single Busbar 12 kV 2.61 0.00 0.00

Transformer S/S, Single Busbar 24 kV 2.14 0.00 0.75

Transformer S/S, Double Busbar 12 kV 1.22 1.92 0.00

Transformer S/S, Double Busbar 24 kV 1.00 0.00 1.08

RMU 12 kV 40.39 132.00 0.00

RMU 24 kV 33.05 0.00 116.00

Customer S/S 12 kV 4.48 0.00 0.00

Customer S/S 24 kV 3.66 0.00 0.00

Abbreviations: RMU — ring-main unit. S/S — substation.

Calculation of Life Cycle Inventory and Environmental Impact Indicators

The life cycle inventory covered acquisition of raw materials, pre-production of all

relevant materials, manufacture and operation of switchgear, and electricity gen-

eration. SF6 emissions from GIS included losses during manufacture, operation,

and end-of-life management. Discounted SF6 emissions during manufacture and

operation were calculated to be 0.14 % p. a., based upon ZVEI surveys. Losses

during end-of-life management were assumed to be 2 %, provided that SF6 ReUse

is employed. This figure was varied across a wide range.

The following environmental impact indicators were calculated using dedicated

LCA software: primary energy demand, global warming potential (GWP), acidifica-

tion potential (AP, »acid rain«), and nutrification potential (NP, eutrophication).


Page 9

Moreover, parameter variations and scenario analyses covered the following rele-

vant factors: SF6 emission rates, length of switchgear use phase, load of switch-

gear, shares of AIS and GIS equipment in grids, and electricity generation mix. The

latter scenarios addressed varying CO2 loads per kWh due to different national

electricity generation mixes.

Results for Environmental Impact Categories

First, the results are presented on switchgear level, i. e. not considering other grid

components, such as cables, lines, and transformers. This allows for a more de-

tailed comparison. In a subsequent step, however, a dominance analysis will show

the rather minor contribution of switchgear compared with those other grid compo-

nents. This will put the results on switchgear level into perspective of the grid level.

All results for environmental impact categories are shown as relative figures, nor-

malised to the AIS reference system. The results obtained for global warming po-

tential (GWP) as the critical impact category – with the smallest differences be-

tween AIS and GIS systems – are commented individually. Results for the other

impact categories – primary energy demand, acidification potential (AP), and nutri-

fication potential (NP) – show even larger advantages for the GIS systems.

ZVEI Product Mix

The ZVEI Product Mix should represent an average assortment of MV switchgear

equipment for utilities and industrial customers in Germany. The global warming

potential GWP100 calculated for the ZVEI Product Mix amounts to 115 tonnes of

CO2 eq./a with AIS switchgear and approx. 90 tonnes of CO2 eq./a with GIS

switchgear. Ohmic losses account for 67 % (AIS) and 65 % (GIS) of these figures,

respectively. With GIS switchgear, SF6 emissions contribute 22 % to the total

GWP100 of the system. Using GIS switchgear, the advantage regarding GWP100 is

almost 22 %, as compared to AIS (Figure 4). Results for all environmental impact

categories in absolute figures calculated for the ZVEI Product Mix are shown in

Table 6.


Page 10

Primary Energy Demand

0%

20%

40%

60%

80%

100%

120%

ZVEI AIS ZVEI GIS

Global Warming Potential GWP100

0%

20%

40%

60%

80%

100%

120%

ZVEI AIS ZVEI GIS

Acidification Potential AP

0%

20%

40%

60%

80%

100%

120%

ZVEI AIS ZVEI GIS

Nutrification Potential NP

0%

20%

40%

60%

80%

100%

120%

ZVEI AIS ZVEI GIS

Materials and manufacture Ohmic losses SF6 emissions

Figure 4: Results for environmental impact categories calculated for the ZVEI Product Mix (switchgear level, i. e. other grid components, such as cables, lines, and transformers were not considered). Relative figures normalised to the reference system AIS = 100 %.


Page 11

Table 6: Results for environmental impact category indicators calculated for the ZVEI Product Mix

Materials and Manufacture of all Switchgear

Ohmic Losses of Transformer

Substations

Ohmic Losses of Ring-Main Units

(RMU)

Ohmic Losses of Customer Substations

SF6 Emissions of Switchgear

Primary Energy Demand [MJ/a]

AIS 443,625 263,450 872,130 234,700 —

GIS 135,721 202,000 595,680 234,160 —

Global Warming Potential GWP100 [kg CO2-Äq./a]

AIS 37,855 14,888 49,284 13,263 0

GIS 12,029 11,415 33,662 13,232 19,556

Acidification Potential AP [kg SO2-Äq./a]

AIS 456.0 18.3 60.7 16.3 —

GIS 130.6 14.1 41.4 16.3 —

Nutrification Potential NP [kg PO4-Äq./a]

AIS 12.59 2.80 9.26 2.49 —

GIS 3.37 2.14 6.32 2.49 —

Urban Grid

Since the topology of the urban grid remains identical in case of AIS or GIS equip-

ment (cf. Figure 2 and Table 4), only the results for the underlying switchgear

product mix are given here; the influence of other grid components is shown in the

dominance analysis below.

The global warming potential GWP100 calculated for the urban grid amounts to

1,220 tonnes of CO2 eq./a with AIS switchgear and approx. 1,190 tonnes

of CO2 eq./a with GIS switchgear. However, ohmic losses of cables, lines and

MV/LV transformers are identical in both cases and account for 91 % (AIS) and

92 % (GIS) of these figures, respectively. Whereas the contribution of switchgear is

only 10.4 % (AIS) and 7.4 % (GIS), respectively. With GIS switchgear, SF6 emis-

sions contribute 1.4 % to the total GWP100 of the system. Using GIS switchgear,

the advantage regarding GWP100 is 3.2 %, as compared to AIS. Figure 5 shows

only the comparison by switchgear, excluding the dominant and identical contribu-

tion by cables, lines, and HV/MV transformers. Results for all environmental impact

categories in absolute figures calculated for the urban grid are shown in Table 7.


Page 12


0%

20%

40%

60%

80%

100%

120%

Urban AIS Urban GIS


0%

20%

40%

60%

80%

100%

120%

Urban AIS Urban GIS


0%

20%

40%

60%

80%

100%

120%

Urban AIS Urban GIS


0%

20%

40%

60%

80%

100%

120%

Urban AIS Urban GIS


Figure 5: Results for environmental impact categories calculated for the urban grid (switchgear level, i. e. other grid components, such as cables, lines, and transformers were not considered). Relative figures normal-ised to the reference system AIS = 100 %.


Page 13

Table 7: Results for environmental impact category indicators calculated for the urban grid

Materials and Manufacture of

Switchgear

Manufacture of other Components

Ohmic Losses of Switchgear

Ohmic Losses of other Components



AIS 410,737 7,920 1,644,210 19,473,000 —

GIS 84,610 7,920 1,129,595 19,473,000 —


AIS 35,300 393 92,915 1,100,400 0

GIS 7,805 393 63,835 1,100,400 16,965


AIS 379.7 6.4 114.4 1354.8 —

GIS 97.5 6.4 78.6 1354.8 —


AIS 11.77 0.15 17.46 206.75 —

GIS 2.38 0.15 11.99 206.75 —

Rural Grid

Since the topology of the rural grid remains identical in case of AIS or GIS equip-

ment (cf. Figure 3 and Table 4), only the results for the underlying switchgear

product mix are given here; the influence of other grid components is shown in the

dominance analysis below.

The global warming potential GWP100 calculated for the rural grid amounts to

930 tonnes of CO2 eq./a with AIS switchgear and approx. 890 tonnes of CO2 eq./a

with GIS switchgear. However, ohmic losses of cables, lines and HV/MV trans-

formers are identical in both cases and account for 87 % (AIS) and 91 % (GIS) of

these figures, respectively. Whereas the contribution of switchgear is only 12.6 %

(AIS) and 8.7 % (GIS), respectively. With GIS switchgear, SF6 emissions contribute

1.6 % to the total GWP100 of the system. Using GIS switchgear, the advantage re-

garding GWP100 is 4.2 %, as compared to AIS. Figure 6 shows only the comparison

by switchgear, excluding the dominant and identical contribution by cables, lines,

and MV/LV transformers. Results for all environmental impact categories in abso-

lute figures calculated for the rural grid are shown in Table 8.


Page 14


0%

20%

40%

60%

80%

100%

120%

Rural AIS Rural GIS


0%

20%

40%

60%

80%

100%

120%

Rural AIS Rural GIS


0%

20%

40%

60%

80%

100%

120%

Rural AIS Rural GIS


0%

20%

40%

60%

80%

100%

120%

Rural AIS Rural GIS


Figure 6: Results for environmental impact categories calculated for the rural grid (switchgear level, i. e. other grid components, such as cables, lines, and transformers were not considered). Relative figures normalised to the reference system AIS = 100 %.


Page 15

Table 8: Results for environmental impact category indicators calculated for the rural grid

Materials and Manufacture of

Switchgear

Manufacture of other Components

Ohmic Losses of Switchgear

Ohmic Losses of other Components



AIS 368,639 14,693 1,496,159 14,345,000 —

GIS 74,195 14,693 1,001,714 14,348,000 —


AIS 32,533 867 84,548 810,520 0

GIS 6,767 867 56,608 810,830 14,137


AIS 344.3 10.4 104.1 997.4 —

GIS 80.6 10.4 69.7 998.2 —


AIS 10.67 0.27 15.89 152.30 —

GIS 2.03 0.27 10.64 152.35 —

Dominance Analysis of Grid Components

A dominance analysis was conducted to examine the contributions of various grid

components to the global warming potential (GWP) indicator of the whole distribu-

tion system. This analysis was applied to the two representative sample distribution

grids, both urban and rural. In either case, cables, lines, and HV/MV transformers

were found to contribute around 90 % of the total GWP result. In contrast to this,

the switchgear themselves constitute only about 10 %. This fundamental proportion

remains true irrespective of whether AIS or GIS equipment is used. As a conse-

quence, the system GWP cannot be reduced substantially by imposing prefer-

ences in switchgear technology.

Figure 7 illustrates this relation for the urban grid; the results for the rural grid are

comparable. Furthermore, this shows that RMU in turn constitute the predominant

contribution among switchgear, i. e. if cables, lines and transformers are ignored.

Moreover, in case of GIS equipment, the contribution of SF6 emissions to the GWP

of these sample grids is only 1.4 % (urban) and 1.6 % (rural), respectively. This

confirms that with respect to climate protection, restrictions on SF6 emissions from

switchgear would reduce total GWP only insignificantly.


Page 16

Contributions to Global Warming Potential GWP100Urban Distribution Grid AIS

Ring-main Units (RMU)9%

Others10%

Other Grid Components90%

Transformer Stations1%

Contributions to Global Warming Potential GWP100Urban Distribution Grid GIS

Ring-main Units (RMU)7%

Transformer Stations1%

Other Grid Components92%

Others7%

Figure 7: Dominance analysis for sample urban utility grids using AIS or GIS equipment, respectively. Contribu-tions of grid components to global warming potential (GWP100) are shown. Grid components other than switchgear include cables, lines, and transformers. (Totals may differ from 100 % due to rounding im-precision.)

8%


Page 17

Interpretation and Discussion

On grid level, being relevant for planning decisions, the predominant contribution to

climate impact (GWP) of power distribution grids are ohmic losses from compo-

nents other than switchgear. It was shown that restrictions on a particular switch-

gear technology, and SF6-GIS in particular, would fail to be environmentally effec-

tive. On the contrary, GIS technology permits locating the RMU close to consum-

ers, thus further minimising substantial losses arising from MV/LV transformers. In

a conservative approach, this effect has not been quantified in this LCA.

In the following, the major factors determining the results of this LCA are discussed

as for their influence (derived from parameter variation and scenario analysis):

♦ SF6 emissions from medium-voltage GIS constitute only a minor contribution to

GWP of the distribution grid (about 1.5 %, even when GIS technology is em-

ployed exclusively). Hence, the sensitivity of the results of this LCA towards this

parameter – leakage plus discounted emission from manufacture and end-of-life

management – is very low. The voluntary commitment adopted by electric in-

dustry ensures that, using the SF6 ReUse concept, even during end-of-life

management no significant emissions are incurred.

♦ The realistic lifetime of medium-voltage switchgear is demonstrated to be of

comparatively small influence. The discounted environmental burdens due to

materials do not cause a qualitatively significant change of results throughout

the range of 30–50 years lifetime.

♦ Conversely, an increased load of switchgear substantially improves the advan-

tage of GIS technology concerning GWP. Grid operators expect that the load is

usually rather higher than assumed in this LCA and will grow further in the fu-

ture for reasons of efficient grid utilisation. On the other extreme of the range,

even minimum loads as in rural areas do not cause a break-even in GWP of

AIS and GIS technology.

♦ Since ohmic losses are the single most relevant factor determining the GWP of

the distribution grid, the specific CO2 load of the electricity mix plays a signifi-

cant role. However, variations of the specific CO2 load of the electricity mix are

fairly limited, unless energy generation undergoes a fundamental change. For

instance, a realistically moderate increase of either wind energy or power pur-

chases from other European countries does not substantially influence the re-

sults of this LCA. Conversely, a fundamental change in energy generation (for

instance, with decentralised power plants) would also imply completely different

transmission and distribution grids.


Page 18

Transferability of Results

The basic results of this LCA apply to industrial grids as well. Apart from topology,

the main difference is that RMUs are the most prevalent type of switchgear in utility

grids; whereas in industrial grids, there are larger numbers of transformer and cus-

tomer substations. Hence the advantages of GIS technology that were shown to be

greater for RMUs than for substations will make less of a difference. Since ohmic

losses of other components are predominant, this will not substantially affect the

expected results for industrial grids. On the contrary, the load is rather higher in in-

dustrial grids, thus shifting the balance further in favour of GIS equipment.

With a similar rationale, the fundamental conclusions of this LCA can also be ap-

plied to other European countries. As ohmic losses of other components are the

major influence on GWP, the specific national product mix will not affect the out-

come very much. This was shown by a scenario analysis (Figure 8); using the

ZVEI Product Mix, the resulting advantages in GWP are shown in relation to the

AIS reference scenario. Even for countries with a lower CO2 load of the electricity

generation mix – due to either nuclear or renewable energy sources – the relative

GWP advantage of employing GIS equipment remains greater.

Global Warming Potential GWP100Szenario Analysis for Electricity Mixes

ZVEI Product Mix

-100%

-80%

-60%

-40%

-20%

0%

20%

40%

60%

80%

100%

0,0 0,2 0,4 0,6 0,8 1,0 1,2

CO2 Load of Electrity Mix [kg CO2 eq./kWh]

Rel

ativ

e G

WP

Adv

anta

ge v

s. B

asis

Sce

nario

AIS

[%]

AIS

GIS

ElectricityMix Norway

Electricity Mix France

Electricity Mix Germany/Wind +10%

Basis: Electricity Mix Germany

Electricity Mix Czech Rep.

Figure 8: Scenario analysis examining the influence of the CO2 load of the electricity generation mix on results for

global warming potential GWP100 – calculated for ZVEI Product Mix

The shares of RMUs as opposed to transformer and customer substations in the

product mix show a moderate influence on the results; yet, this becomes insignifi-

cant if the other grid components are taken into consideration. With topology re-


Page 19

maining identical for AIS and GIS, the differences in grid design in various coun-

tries will not have a substantial bearing on overall results.

Conclusions and Recommendations

When assessing the environmental profile of power distribution, the system ap-

proach, implying a consideration on grid level, is indispensable to obtain meaning-

ful results. Consequently, if ohmic losses from cables, lines, and transformers are

taken into consideration, the differences between MV switchgear technologies AIS

and GIS become all but negligible. This life cycle assessment (LCA) indicates that

electrical power losses due to ohmic resistance of cables, lines, and HV/MV trans-

formers constitute the predominant contribution to the GWP of distribution grids.

Because of their compact construction and their sealed, gas-tight compartments,

the investigated GIS are advantageous from an environmental point of view, even

concerning climate impact (GWP). When considering a GIS unit on its own, the

largest share (about 70 %) of GWP-relevant emissions is due to ohmic losses.

These originate not least from switchgear components that are independent of AIS

or GIS technology, e. g. voltage transformers and fuses. Extrapolating the data of

this LCA, the specific contribution of SF6 emissions from MV switchgear during

their lifecycle to the overall GWP in Germany is estimated at less than 0.005 %.

Since the environmental benefits that can be accomplished by giving preference to

AIS or GIS technology in medium-voltage applications are insignificant, AIS and

GIS switchgear are competitive from an environmental point of view. Aside from

ecological considerations, the assessment of alternatives must take other aspects

into account. This is corroborated by a communication of the European Commis-

sion Directorate General Environment to the ECCP Working Group:

»Amendments to marketing restrictions — […] In making such proposals the

Commission must ensure that an assessment of alternative substances and tech-

nologies has been made which takes into account the safety, impact on human

health, technical feasibility, cost-effectiveness and environmental impact of such al-

ternative substances or technologies.« 1

The following conclusions are derived from the results:

♦ The system approach, involving a consideration on grid level, is indispensable

in order to obtain meaningful results. On the one hand, the overall contribution

of electricity distribution grids to national greenhouse gas emissions is con-

firmed to be very small. On the other hand, ohmic losses are clearly identified


Page 20

as the predominant factor influencing the climate impact of the system. As a

consequence, if ohmic losses from cables, lines, and transformers are taken

into account, the differences between MV switchgear technologies become all

but negligible. Therefore, relevant climate impact reduction potentials due to a

regulation targeted on electrical switchgear and components are not expected.

♦ If a comparison of medium-voltage applications is yet made, GIS technology

shows advantages compared with AIS technology, regarding primary energy

demand, acidification potential (acid rain), nutrification potential (eutrophication),

and even global warming potential (GWP). Losses of SF6 from GIS medium-

voltage equipment are very small and consequently affect the GWP only to a

negligible extent. Conversely, the load of distribution grids and of switchgear

themselves is found to be the principal GWP factor. The current trend towards

higher utilisation of grid capacities would thus favour GIS. In order to realise any

significant optimisation potential, however, a load management for distribution

grids appears more useful than any technical modification of switchgear.

♦ Hence, bans and restrictions on the use of GIS medium-voltage equipment as

proposed by the recent policy paper are not justified from an ecological point of

view. As a meaningful contribution to climate protection cannot be achieved by

regulatory measures directed at switchgear and components, it appears appro-

priate to leave technological decisions to the grid operators, who will take other

criteria, such as economic feasibility and personnel safety, into consideration.

♦ The results of this LCA may in principle be transferred to other European coun-

tries. The primary energy mix for electricity supply, being the most important re-

gional factor, showed only a minor influence on the results.

References

The full report of this LCA study is available on request – please contact the au-

thor: Dr.-Ing. Ivo Mersiowsky, Solvay Management Support

PO Box 220, D-30002 Hannover, Germany, [email protected]

Citations may be made as follows:

[SOLVAY et al. 2003] — Solvay Management Support: SF6-GIS-Technologie in der Energieverteilung –

Mittelspannung. Life Cycle Assessment study commissioned by ABB, AREVA

T&D, EnBW Regional, e.on Hanse, RWE, Siemens and Solvay Fluor und Derivate.

Solvay: Hannover/Germany (in German, abstract and summary available in Eng-

lish).

1 Document DG ENV.C.2/JD D(2003)421117 dated 12/06/2003.

Validity Statement by TÜV NORD CERT

lca gis mv summary 1 2003

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