SWS and Electrification

Lessons from Ghana’s Experience.

By: Jabesh Amissah-Arthur,Managing Partner,

Presentation Outline Electrification in Ghana.

Starting Conditions. Accomplishments.

Innovating for Rural Electrification. Background and Motivation for SWS. The Shield Wire Scheme (SWS) – Description Benefits and Savings of SWS. Cost Comparison with standard MV supply. Operational Comparison with standard MV supply.

Conclusion. Successes and Failures. Lessons.

Starting Conditions

The grid supplies only 240 towns in 1/3rd of Ghana.

Virtually all isolated diesels are non-operational.

Macro-economic indices far from being favourable. 5yrs of economic decline. 3yrs of drought, 1982-84. Project area considered to

be very poor.

Project viability doubtful !

Starting conditions were simply far from ideal.

Accomplishments

1985: Grid covers only 1/3rd of Ghana’s land area. Access to service = 23%.

1990: Nine regional capitals and 400 towns have supply from grid.

1995: 1,000 towns (including 87 of 110 district capitals) have grid supply.

2000: All districts and 2100+ towns have grid supply. Access = 43.7%.

2005: 3,200 towns to have supply. Access = 50+%

Innovating for Rural Electrification: Background & Motivation for SWS The citizens of small communities living near HV

transmission lines who had no supply made it a Corporate Social Responsibility and Public Relations issue for the utility, Volta River Authority (VRA).

VRA invited Prof. Iliceto in early 1980s to make innovative proposals for a “Low Cost” solution to serve the settlements near its 161kV transmission lines.

Shield Wire Scheme (SWS) is proposed & implemented: SWS is serving more than 10,000 households in 30

communities that may not otherwise have been served. The cost of SWS is only a fraction of standard MV line. The operational performance of the SWS in terms of

outage frequency and time is better than normal.

The Shield Wire Scheme (SWS)

The SWS uses the sky/shield-wire which is normally grounded with no voltage and only shields the power lines below.

The sky/shield-wire in this case is: Insulated for medium voltage operation. Energised at 20-34kV from sub-station. Supplies loads using earth return current.

Still performs power line protection.

No additional environmental impact.

The Shield Wire Scheme (SWS)

Savings and Benefits

Installation Costs are lower because: Common usage of conductors & grounding rods. Does not add to the power line right-of-way.

Operational Performance is better as: Outage rates are low & permanent faults are rare. Low medium voltage losses due to conductor size. Maintenance burden is extremely low.

Other Benefits. Community protection of the transmission line.

Cost Comparison: MV vrs SWS

Insulators Insulators

Steel Lattice Towers

Survey & Civil Works

Conductors

Accessories

0

5,000

10,000

15,000

20,000

25,000

30,000

MV Line SWS

US

$ p

er

km

MV Line SWS Comment

Acquisition of Right-of-Way Variable - Depends on local conditions.

Survey & Civil Works

4,500 -

Steel Lattice Towers 7,500 750 Increase in erection only

Conductors 10,000 -

Insulators 2,500 3,000

Accessories 500 -

Total Cost per kilometer 25,000 3,750 Saving = 85%

Typical Construction Cost of 34.5 kV line in US $ per km)

0

50

100

150

200

250

300

2000 2001 2002 2003 2004

Fre

qu

ency

MV 1

MV 2

SWS 1

SWS 2

Comparison of Operational PerformanceTotal Outage Frequency - Standard MV vrs SWS.

Successes and Failures The massive extension of the HV grid presented an

opportunity to deploy SWS on the new lines.

SWS cost is only 15% of equivalent MV line. Yet its operational performance is superior.

SWS is now proven technology which supplies settlements within a 20km corridor of the transmission line at very reasonable cost.

A subsidised connection charge helped many to receive supply initially. But paying the bills to maintain supply has been difficult for some.

In more than a few villages, only the Chief’s Palace has been able to retain supply.

Lessons SWS is well-suited for medium sized communities (ie

total <10MW) located near transmission lines. When planning electrification for poor communities

we need to recognise two affordability thresholds:A. Those who can at least afford the variable (operating) cost

of supply but not the full capital recovery burden.

B. Those who cannot afford even the operating cost alone.

Electrification for Group A is sustainable with only an initial connection subsidy which may be justified on social & poverty alleviation considerations.

Access for Group B requires perennial subsidy and so needs cautious consideration of the source of subsidy else “true access” may not be sustainable.

The EndLessons from GHANA’s experiences.

Jabesh Amissah-Arthur