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Highveld Power Station

​Highveld Timeline of History (1955 - 1963)

 
  Highveld Power Station
 

1955

Dr Johannes Theobald Hattingh was Chairman of  ESCOM when the preliminary work was started on the design of a new power station for the Rand and OFS Undertaking in the district of Heilbron near to Taaibos power station. The water supply was to be provided by the Department of Water Affairs from the enlarged conservation works on the Vaal river. Coal would be supplied from a new colliery to be established by the Clydsdale (Transvaal) Collieries Ltd on coal bearing ground south of the company's existing colliery at Coalbrook. The power station was to be constructed adjacent to Taaibos power station, and ESCOM’s village was to be enlarged to cater for the employees of the two stations. However, the two stations were to be run separately.

1959

The construction of Highveld power station started in January. The first two 60 000kW turbo-generators with their associated boilers were completed and taken into commercial service in February and April of 1959. Two further sets were completed later that year.

A decision was made to establish a 275kV transmission system as a backbone to the Rand and OFS Undertaking. The backbone was used to strengthen the interconnection between the northern and southern group of Rand and OFS power stations; and enable power to be directed to the expanding networks in the OFS and Western Goldfields.

1960

Disaster at Coalbrook North Colliery.

1963

Total capital cost of construction to date was approximately £44 900 000.00

On the 8th November 1963 the Ho​norable Minister AE Trollip visited both Taaibos and Highveld power stations at the invitation of Dr and Mrs RL Straszaker.

Technical Details

Total station electrical capacity

480 000kW

•Total boiler capacity

4 400 000lb/hour

•Steam consumption per kWh generated

8.72lb.

•Approximate calorific ​value of coal​

8 810BTU/lb.

•Overall thermal efficiency on units sent out

28.3%

•Heat rate on units sent out

12 050BTU/kWh

•Coal Consumption per unit sent out

1.368lb


Commissioning Dates of the Plant

Turbo ​Generator

Date

         4 February 1959
         5 April 1959
         3 June 1959
         6​ October 1959
         2 April 1960
         7 December 1960
         1 March 1963
         8 May 1963​

​General Description of the Plant

Turbine House 

7 X 2 Cylinder Impulse Reaction type turbines with generators rated at 60/66MW (70 590/77 650kVA at 0.85pf) manufactured by Brown Boveri Limited. 


1 X 2 Cylinder Impulse type turbine generator with generator rated at 60MW (70 590kVA at 0.85pf) manufactured by Metropolitan-Vickers Limited.

•Steam conditions at turbine stop valve: 900lb/sq.in at 900°F
•Speed 3 000rpm. with direct coupled exciters except for Generator 5 which was gear driven.
•Generators hydrogen cooled, with fans on the shaft.
•MVA rating at H2 pressure 14.7psi abs was 70.59
•MVA rating at H2 pressure 28.0psi abs was 77.7 (Brown Boveri)
•Generator Voltage 11 000. Full load current 3 700amps at 60MW

•Condensers cooling surface:

Brown Boveri sets

49 500sq.ft

Metropolitan-Vickers set

54 000sq.ft

•Circulating water flow:

Brown Boveri sets

42 200gallons/minute

Metropolitan-Vickers set

43 000 gallons/minute


circulating water flow was provided by two pump houses, one at each end of the station. Each pump house contained 4 X 58 200gpm pumps driven by 1210hp motors.

Boiler House

Four Babcock and Wilcox pulverized-fuel bo​ilers, bi-drum with pendant superheaters and tangent tube furnaces.

•Continuous rating (each> 550 000lb/hour
•Outlet pressure 925psig
•Outlet temperature 925°F
•Fully automatic combustion control
•Four coal pulverizing mills per boiler, one as a standby, each driven by 130hp motor.
•Capacity of each mill 25 650lb/hour (11,5tons/hour)
Four International Combustion pulverized fuel boilers, bi-drum with pendent superheaters and tangent tube boilers.
•Continuous rating (each> 550 000lb/hour
•Outlet pressure 925psig
•Outlet temperature 925°F
•Fully automatic combustion control
•Four coal pulverizing mills per boiler, one as a standby, each driven by 130hp motor.
•24 200lb/hour (10.8tons/hour)
Two feed pumps per unit, one as a standby. Each pump had a capacity of 600 000 lb/hour, driven by 1 450hp motor.
•Length of boiler house 680 feet
•Height of boiler house 158 feet
•Ash plant International Combustion hydro-jet type.
•Ash pumped to dams to the east of the station

Coal Plant

Coal obtained from the Clydesdale Colliery, and delivered by overland belt conveyer 6 482 feet long to station coal staiths, with a storage capacity of 24 000 tons.
•Capacity of conveyor 650 tons/hour
•Belt 42 inches wide
•Speed of conveyor 400 feet/minute

Cooling Towers

Six cooling towers were built in two groups of 3 towers each. Five of the towers were splash type filled and one was asbestos cement packed for film flow cooling.
•Height above pond level 127 feet
•Internal dimensions Top 127 feet
Throat 120 feet
Above pond 214 feet
•Capacity 3 240 000 gallons/hour
•Approximate cooling range 15°F


Water

Water was obtained from the Vaal river where a pump station was built, which contained four pumps each of a capacity of 6 600 gpm.

The pipeline was 24km long, with the first 16km being 80cm bore. At this point there was a take-off supplying Sasol, after which the pipeline was 60cm bore up to the station.

Water storage capacity at the power station was 12 million gallons. The reservoirs were interconnected with the 6 million gallon storage reservoirs at Taaibos power station.

Water Purification Plant

This plant which s​upplied potable water to both power stations and colliery properties has a normal output of 650 000 gallons per day.

Water Softening Plant

The water softening plant supplied softened water for boiler make-up, and was of the base-exchange type. It was fully automatic and capable of softening 168 000 gallons of water per day.

Switch​gear

The main station busbars were outdoor strung type using double conductors and energized at 275kV. The 275kV switchgear connected to the duplicated busbars was of airblast type, manufactured by Brown Boveri and had a rupturing capacity of 7 500MVA.

Each generator was connected through a 11/275kV generator transformer and a 275kV circuit breaker to the 275kV busbars.

There were six outgoing 275kV feeders, two each to Everest, Scafell and Snowdown Distribution Stations.

There were two 3.3kV Station Boards comprised 150MVA rupturing capacity switchgear. Supply to the boards was from either the 15MVA 275/3.3kV station transformer, or alternatively from a 15MVA 132/3.3kV transformer fed from Taaibos.

Motors of 200hp and higher rating were supplied at 3.3kV and smaller motors at 380 volts.

Switch Operating Room (Control Room)​

 
 

The switch operating room contained control and relay panels for remote control and automatic protection of all the 275kV circuit breakers, generators, feeders, transformers and main 3.3kV circuits. Communication services were also centred in the switch operating room. The control and relay panels were manufactured in South Africa.​

Transformers

Generator transformers were rated at 73MVA ratio 11/275kV with forced oil blast cooling. The unit transformers for the turbine and boiler auxiliaries were connected directly to the generator terminals. These were natural cooled oil filtered units rated at 5.5MVA with a voltage ratio of 11/3.3kV.

Works​hops

Mechanical and electrical workshops were equipped with machine tools and facilities for effecting normal maintenance and all but the heaviest repairs to the power station plant

DISASTER AT THE COALBROOK NORTH COLLIERY

On the 21 January 1960, a tragic disaster occurred at the Coalbrook North Colliery of the Clydesdale (Transvaal) Collieries Limited. Regarded as the worst disaster in South African mining ​history, a subsistence of rock trapped 437 miners. Despite nearly two weeks of rescue efforts, none of the men survived. The north colliery was the sole supplier of coal to Taaibos power station. The South Colliery supplied coal to Highveld Power Station. Prior to the disaster, Taaibos was burning 40 000 tons of coal per week, and as a result the disaster had a significant effect on the output of the station.

In order to relieve the load from Taaibos, steps were taken to transfer the load to other power stations, as well as obtaining coal from the South Colliery and Cornelia Colliery near Vereeniging. At a later stage coal was also railed in from ​Witbank. However the boilers at Taaibos were designed for burning the type of coal produced from the Vereeniging coalfields. As a result it was necessary for coal from Cornelia to be railed to Taaibos. The Witbank supplies were used at Klip and Vereeniging power stations.

MOTHBALLING

The process of closing down Taaibos and Highveld power stations began in 1986. Both power stations were to be placed in reserve storage (“mothballed”) over a period of two years. A “mothballed” power station was one that could be brought back into service if necessary.

DECOM​MISSIONING

A decline in mining and industrial activity resulted in decreased demand for electricity. Consequently, a decision was made in 1994 to decommission and dispose of Highveld and Taaibos power stations. Attempts to sell the power stations were unsuccessful. Both stations were no longer viable as operating power stations. Spare parts and the cost of operating staff would be too costly. Also, ESCOM could not guarantee the demand for any electricity generated.

Staff who were employed at Kragbron either transferred to other power stations, or chose early retirement packages. As the closing down of the power station was phased over a number of years, and done in a controlled manner, the final shut-down had little affect on the surrounding community.

In 1999, five people were still working full time at Kragbron. They were to remain until the final disposal of the power stations. All storage facilities were rented to outside users to generate income.

Within the next couple of years all of the buildings will be demolished except for the offices of Taaibos.
The cooling towers will be imploded and coal staiths demolished. All equipment will be sold as parts or scrap.

The residential accommodation has been rented out by Esprop (ESCOM Properties department) to non-ESCOM families within the surrounding areas, and is currently running at approximately 95% occupancy.

REF​ERENCES

Electricity Supply Commission - Rand & Orange Free State Undertaking - Published by ESCOM

Electricity Supply Commission - Taaibos & Highveld power stations, Report written for the visit of the Honourable Minister AE Trollip, 1963.

ESCOM Annual Financial Reports (1946-1998)

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