Derrick BolttSouthern

Region Hydro Generation

Eskom South Africa

Hydro Power in the S/Region.

History of Hydro in the S/Region.

• In 1980 the former Transkei government financed the development of Hydro power schemes in the Eastern Cape .

• Four Hydro Electric stations were built between 1980 and 1984 in the region.

• The stations were allocated to the Transkei Electricity Supply Corporation. (Tescor)

• The Four Facilities were handed over to Eskom Southern Region in April 1995.

The Four Stations Are:

• Collywobbles on the Mbashe river system approximately30kM east of Idutwya .

• First Falls on the Mthatha river situated approximately 5kM east of Mthatha.

• Second Falls on the same river about

15kM down stream from First Falls.

• Ncora on the Tsomo river approximately 50kM west of Engcobo in the North.

Mbashe Hydro Station.

Mbashe From the Air

2nd Falls Hydro Station.

1st Falls Hydro Station

Ncora Hydro Station.

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Southern Region

SOUTHERN HYDRO INTERCONNECTION

Bypass

Umtata River

Mbashe River

Xuka River

Mgwili River

Ncora Dam

Tsomo River

Ncora Irrigation

Ncora Hydro

Ncora Load

Tsomo River

3.3/22/66kVMunicipal

Hydro

First FallsBalancing Dam

Second FallsBalancing Dam

First FallsHydro 11/66kV

Second FallsHydro 11/66kV

Umtata RiverMbasheRiver

Hydro

MbasheWeir

Collywobbles Hydroelectric Scheme 11/66kV

132/66kV

132/66kV

Butterworth132/66kV S/S

ButterworthLoad

132kV line from Pembroke

UmtataLoad

Port St. JohnsNetwork

Qumbu/DumasiLine

FLOW PLAN AND ELECTRICAL INTERCONNECTION

ELECTRICAL SWITCH

ELECTRICALTRANSMISSION LINE

WATER VALVE CONTROL

RIVER

LEGEND

ELECTRICAL SWITCH

ELECTRICALTRANSMISSION LINE

WATER VALVE CONTROL

RIVER

LEGEND

Gauging weir

Gauging weir

NCORA DAM 90 MCu capacity

Over Flow from Ncora Dam

MTHATHA DAM 250 MCu capacity

Mbashe Buffer Dam

Overview of Collywobbles/Mbashe

• Mbashe has three 14MW units with the provision for a future fourth machine.

• Penstock is 1.4kM long by 4.6m diameter dual lined tunnel operating at 14 bars.

• Plant does not have SCO capability due to the design of the draft tube and tail race.

• Siltation of the dam has significantly reduced the available water reserves.

• Water consumed on full load is 38m3/sec.

Mbashe Hydro Gens

Salient Pole Rotor and Stator

Mbashe Spare MIV and Penstock

Mbashe Generator Floor

Overview of Second Falls

• The station has two 5.5MW units with the provision for a future third machine.

• Penstock is 44m long by 3.5m diameter steel tunnel that operates at 4bars.

• Water is discharged from 1ST Falls and reaches 2nd Falls about eight hours later.

• Both units are modified for SCO mode.

• Water consumed on full load is 25m3/sec.

• Station was totally refurbished in 2000.

2nd Falls Hydro Generators

2nd Falls From the Road.

Overview of First Falls

• The station has two 3MW units with the provision for a future third machine.

• Penstock is 27m long by 2.7m diameter steel pipe that operates at 2bars.

• Water is discharged at 6m3/sec from Mthatha dam down the river to 1st Falls.

• Both units are modified for SCO mode.

• Water consumed on full load is 28m3/sec.

• Discharged water flows down to 2nd Falls .

1st Falls Hydro Turbines

1st Falls Hydro Generators

Overview of Ncora Hydro.

• This station has a single 1.6MW unit and two 400kW slip ring machines.

• The machines were removed from 1st and 2nd Falls when they were upgraded.

• Penstock is 260m long by 1.6m diameter steel pipe that operates at 4 bars.

• Water is released from the main Ncora dam via a canal to the holding dam.

• The plant does not have SCO capabilities.

• Water consumed on full load is 6m3/sec.

Ncora Hydro Generators

400KW DC Excitation Machine.

Ncora Hydro Splitter Weir

Upgrading of Mbashe.

• The tunnel was fitted with an extra 70m of steel lining to seal cracks in the concrete.

• The three Boving turbines and the Main Inlet valves were refurbished in 2001.

• The auto voltage regulators and generator protection controls were all upgraded.

• The plant cooling was replaced with closed loop towers to minimized the down times.

• Scada and Telemetry systems improved.

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1985Cracks in the first 50m of concrete penstock.Water pressure in hillside results in landslides.Bore holes are established on the hillside to prevent pressure build-up but is onlysemi-successful.

To Hydro’s -Steel section.

To Weir - Concrete section.

Access pit at station.

Mbashe – Tremor.

Generator Protection Relay.

Unitrol Auto Voltage Relay

Closed Loop Cooling Towers

Control Desk at Mbashe

Upgrading of 2nd Falls

• The station was flooded in 1998 when one of the Main Inlet Valve was damaged.

• Renovations in 1999 has made the station the most modern facility in the region.

• Most of the mechanical plant including the generators were salvaged and re-used after being refurbished on site .

• Both the Turbines were recently rebuilt.

• Fiber optic communications was installed.

Damaged Main Inlet Valve .

PLC controllers at 2nd Falls

2ND Falls Gen Control Panels

Plant Capabilities .

• Both 1st and 2nd Falls were modified for synchronous condenser operation. (SCO)

• The new control relays allow for maximum reactive power support to the network.

• The units produce real power during peak times and remain in SCO when off peak.

• The change from MW to MVARs is a simple process and is done in a few minutes.

• Protection is calibrated for Reverse Power.

Plant Capabilities cont..

• Different modes of voltage regulation is available.(Voltage , Power Factor & MVar)

• The most stable of these modes is to operate the machines in voltage control.

• The large increase in network loading at Peak times has an effect on Plant stability.

• A unique system of controls and settings have been applied to optimize all the network and plant conditions .

Protection challenges

• The control relay parameters are often revised to facilitate the dynamic network conditions to keep the plant on load.

• The network generated negative phase sequence is high with low peak voltages.

• Islanding of the plant does often occur.

• Remote tripping of the three stations optimized the safe restoration of supply .

Connecting to the Grid.

• Second Falls is the only plant where the synchronization process is fully automated

• The other stations have a manual close facility via a common synch check panel.

• Keeping the plant synchronized to the grid under all conditions is still a challenge.

• Local network conditions are dynamic with variations in network loading and Voltages

Network Loading in the Region

• The 70MVA of connected Hydro power was sufficient in the 90s to supply the 50MVA of loading in the region. (ex Tescor)

• Electrification of the area soon changed that and by 1998 the load had doubled with an additional 132kV line from Natal.

• The huge increase in power made the contribution by the Generators essential for network stability during peak times.

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Evening Peaks

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Date and time

Lo

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VA

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Load ProfileUMTATA DISTRICT

Load Profile - 22 January 2003

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TOTAL LOAD

GENERATION

LINES

Costing and Availability Data.

• The average cost per MWH at the stations varies monthly and is rainfall dependant.

• Plant utilization and availability in summer is high to maximize power production.

• The cost per MWH has varied from R68 in 2007 to R153 per MWH in 2009 .

• The present cost per MWH in July was low due to the recent high rainfall in the area.

• The following graphs will provide detail.

49

Year-On- Year Production in MWH:

2011/09/23 50

Percentage Utilisation of Generators:

Generators percentage Availability:

Average Cost in Rand per MWH.

Future long Term Planning.

• A de-siltation study has recently been completed on the Mbashe dam system.

• Refurbishment of the main inlet valves and the associated service seals.

• Generator stator and winding repairs.

• Maintenance to the Penstock and intake tunnel with all the sealing gates .

• Repairs to the four Hydro dam walls.

Mbashe Dam (Full)

Mbashe Dam Siltation

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Scouring at Mbashe Dam

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Strategic Value of Generation.

• The Generators are needed in Peak times of the day to reduce the high demand which occurs twice a day in the region.

• The Hydro generators ensure network stability for the regional grid in the area.

• The stations provide emergency power on demand - when & If required in a few minutes.

• The Hydro Stations have the ability to Black start and energize the 132kV Backbone.

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Strategic Importance cont..

• Eliminates the need to Load shed large portions of the local network during the winter Peak.

• Reduces the MVA max demand logged on the Transmission in feed to Distribution.

• The reduction in demand reduces the high costs actually paid to Tx by S/Region Dx.

• The ability to run in S.C.O. for some of the units provides Network stability without the use of water .

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The need for the Hydros.

• The max demand in the Eastern area is a typical domestic load that increases drastically by 06h00 to 09h00 and again 17h00 to 21h00.

• Without the Gen availability during those times the 132kV system is strained to the point in winter where load shedding may be done to prevent possible network instability

• If any of the main feeds are down the gens have to support the grid for the full outage duration.

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MVAMTATA AREA LOAD

Pembroke/Kei 132kV safe transfer limit

Requirement f rom 1 and 2 Falls continuous.

Requirement f rom Mbashe varied.

Estimated return to service - 20h00

Max gen required - 63MVA.

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The Importance of Hydro

• The Hydro Gens play a important role in security of supply in the Southern Region.

• By providing instant additional MW power.

• They do have the ability to black start in minutes and Island feed small towns in the area.

• Provide system stability when in SCO mode.

• The power generated is deemed to be renewable energy – Green Power .

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FF G1 MVA MB G3 MVA MB G2 MVA MB G1 MVA SF G2 MW

Typical Gen loading in 24hrs

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To Summarize in Short

• The Hydro Gens in the Southern Region are critical to Ensure the following:

• Network and grid stability to the Region during specific times of the day .

• The Gens allow some flexibility to take out Main 132kV linking lines into the Region.

• The Gens provide a large reduction in Max demand from Tx which saves costs.

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In Conclusion .

• All four of the Hydro Gen sites in the S/Region are required for the business.

• The Government & Eskom has committed to the renewable energy source protocol.

• Green power at present is the Buzz word at all energy conferences in the world .

• We have this green resource available.

• It is a nice to have and a must to keep.

Future Hydro Sites in the Region

• A few additional Hydro generation sites have been identified in the Region.

• The existing site at Teebus on the Orange Fish river Tunnel near Gariep dam.

• Tsitsa Falls on the Umzimvubu river North of Mthatha on the N2 towards Kokstad .

• An additional site on the Umzimvubu River down stream from Tsitsa Falls .

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Existing Turbine at Teebus

Spare MIV at Teebus

Future Tsitsa Falls Site.

Future Umzimvubu Site .

Mbashe River .

Thank You.

Questions?06/09/2004 71