APPLICATION Load management of water projects using an integrated systems approach by Chris Scheepers, Dr. Gerhard Bolt and Marius Kleingeld, North-West University

The Department of Water Affairs (DWA), is responsible for the sustainable supply of useable water in . This water is not only used for residential and agricultural purposes but also to provide water for industrial processes, the mining industries and cooling water for power stations. South Africa is divided into 19 water catchment areas. This case study focuses on the Usutu-Vaal government water scheme (GWS). In close to , which supplies water to and four power stations – Tutuka, Matla, Kriel and Duvha. Water is also transferred from Matla to .

Usutu-Vaal consists of six pump stations. For the purpose of this article only Grootdraai (GD), Grootfontein (GF) and Rietfontein (RF) pump stations are considered. Water is pumped from the , both to and through a 40 km canal to GF which is a booster pump station. GF in turn pumps water to both Sasol and, via dam, to Rietfontein dam. New infrastructures were implemented to control the pumps and a new control philosophy was developed for the pump operational scheduling and for the management of the two pump stations in series. Due to the long distance of the canal, changes to the water flow at GD will take from 11 to 16 h before being detectable at GF. The new philosophy involves operating two pumps at both of these pump stations. The main objective of the demand side Fig. 1: Water management areas in South Africa. management (DSM) project is to ensure that water is not pumped during the evening peak period at both GD and GF. Due to the lengthy delay in the actual water flow variation at GF, the GD pumps must be stopped between 07h00 and 09h00. Fortunately this coincides with the Eskom morning peak period. The power-demand baseline, before project implementation, indicated that the average potential peak time power savings would be 10,15 MW. These savings were comfortably achieved. South Africa is divided into 19 water catchment areas, where water is pumped to different regions to ensure sufficient availability for national strategic important areas as shown in Fig.1. Of these, Eskom and Sasol II and III (Synfuels) are the most important. A project for energy savings was undertaken by HVAC International in the Fig. 2: Usutu-Vaal GWS. water catchment area of the Usutu-Vaal government water scheme. The water scheme consists of the following pump  Geelhoudboom (between pumping stations at Grootdraai (GD), stations: Morgenstond dam and Heyshope Grootfontein (GF) and Rietfontein (RF)  Rietfontein (north of Secunda) dam) showed any real potential for significant electrical cost savings.  Grootfontein (west of Charl Cilliers)  Heyshope (close to Piet Retief)

 Grootdraai and Tutuka (next to Very little pumping actually takes place The Usutu-Vaal GWS was constructed with Standerton) at most of these pump stations. Only the the purpose of supplying water to the

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Sasol II and Sasol III development at Secunda, using water from the upper system. This scheme also supplies water to Tutuka, Matla and Kriel power stations as well as providing an emergency supply to Witbank Dam for .

A major storage dam was constructed at Grootdraai near Standerton from where water is transferred via canals and pipelines across the water divide at Trichardt. These pump stations are located at Standerton (GD), Charl Cilliers (GF) and north of Secunda (RF) with an intermediate storage dam at Trichardt. A pump station for supplying water to Tutuka power station was subsequently built at Standerton as part of the Grootdraai pump station. Fig. 2 gives an overview of the Usutu-Vaal GWS. The focus of this article is only on GD and GF pump stations where a unique control philosophy was developed. GD pump station delivers water to GF pump station via the 40 km Vlakfontein canal. The GF Fig. 3: Installation hardware for Usutu-Vaal GWS. pump station serves as a booster pump station. Water enters GF from the endpoint of the canal (forebay) and is pumped to Knoppiesfontein towers. These reservoirs are the highest points above sea level of the water transfer system. Water is gravity fed to Trichardsfontein dam and also Sasol II and III.

From Trichardsfontein dam the water feeds into rivers that flow into the RF dam. Finally, water is pumped to the from RF dam. In the event of the Komati water scheme malfunctioning, this water can be pumped towards . The equipment at all the pump stations was old and outdated and did not have suitable component requirements for automation. It was therefore necessary to Fig. 4: Pump monitoring panel. upgrade the existing control equipment and control philosophy to implement automated control. different pump stations, are presented The old relay control system was upgraded in Figs. 5 and 6, where the high power to PLCs. These upgrades were necessary Previous control equipment consumption during the Eskom peak to implement a REMS in order to control Prior to this study, control of these three morning and evening periods can be the pumps automatically. PLC control was pump stations was accomplished using seen. It is evident that load shifting was not implemented and dam level sensors were outdated relay logic and automated attempted at these pump stations. installed at the water reservoirs. Monitoring control was not possible. Problems of the dam is essential for accurate Manual control of these pumps was done experienced with this equipment and decision making on the number of pumps by the control room operators. The level of pump control were: which should be operated to keep the each dam is reported to the control room dams at a maximum level.  Manual control through telephonic operator. Dam levels were not monitored reporting of dam levels was not reliable remotely and were simply reported by way After the implementation a new control or sustainable of a telephone call. philosophy, based on TOU, the client will have an improved system with intelligent  Outdated control philosophy that could Developing a new control philosophy easily result in future maintenance logging and control. Furthermore, problems For energy savings to be implemented at the scope of the project includes the these pump stations, a programmable commissioning of a variable speed drive  Lack of existing control philosophy that (VSD) on one of the GD pumps. This VSD takes time of use (TOU) into account logic controller (PLC) was introduced, that allows a supervisory control and data had previously been installed but was  No data trending available acquisition (SCADA) system and a real never fully commissioned. Before the start of the project, a power time energy management system (REMS) HVAC International's REMS-pumping baseline was constructed using historical to realise energy savings and optimise the control together with an on-site information data. These power baselines, for the three pumping schedule. management system (OSIMS) was installed

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procedure is not automated but monitored by the operators.

Results During March 2012 to May 2012, load was successfully shifted out of the Eskom peak period at all the pump stations. A major factor to ensure electrical energy savings is the large dam storage capacities. This includes the Eskom and Sasol reservoirs as well as the manmade and natural dams. The new equipment was successfully installed and implemented using the new control philosophy. Results of GD and GF obtained during May 2012 are presented in Fig. 5 and Fig. 6. These figures clearly illustrate the control philosophy and the periods where the pumps were switched Fig. 5: Grootdraai and Tutuka demand. off.

Conclusions By means of proper planning, risk analysis, sound engineering practices and the implementation of a proven REMS- pumping control system HVACI was able to shift large electrical loads out the Eskom evening peak without comprising the supply of water to the power stations. Eskom subsidised the Usutu-Vaal project with a grant in excess of R30-million. Advantages realised from this project are more than just hardware upgrades but also include condition monitoring of the pumps. This makes it possible to run the most efficient pump combinations and schedule accurate maintenance periods.

The electrician can log into the REMS systems remotely, change schedules and analyse the event log to determine whether and why a pump has tripped. This alone saves a lot of time that used Fig. 6: Grootfontein demand. to be wasted driving large distances unnecessarily between pump stations. to monitor, integrate, simulate, optimise System integration of GD and GF pump and control elements of the water pumping stations HVACI facilitated the refurbishment of system. The hardware upgrades which will pumps that were not part of the IDM Due to the length of the Vlakfontein enable REMS control consists of: scope to ensure mechanical reliability water canal between GD and GF, the that is critical to national power security.  Compact logix Ethernet processor effect of the water pumped to GF is only Additional capacity was also made (PLC) per pump measurable after 12 to 24 hours. If two available to ensure the comeback load is  Compact I/O device adapter per pumps are used the time delay is reduced moved to the weekends. HVACI and DWA pump to approximately 11 hours. Therefore, to be have established a new control philosophy  Control panel and MMI (man machine able to stop the GF pumps between 18h00 standard which will be used as benchmark interface) per pump and 20h00, the GD pumps should not only for future DWA projects. The old relay logic

 RSLinx OEM SCADA software be stopped at the same time, but also control panels were due for an upgrade between 07h00 and 09h00. This coincides and Eskom Distribution would have had to  Differential pressure transmitters for the dams and reservoirs with the Eskom morning peak period. initiate a modernisation project, regardless of the necessity to implement load shifting.  Optical fibre communication back By stopping the GD pumps during the Three DWA pumping stations (Jericho, bone with GSM back up morning hours a water-shortage is created Kliphoek and Camden) in the Usutu The hardware and network upgrades are at GF 11 hours later. Without creating scheme are ready for upgrade by Eskom- summarised in Fig. 3. a water-shortage at GF the water will IDM and will soon benefit from the HVAC overflow at the forebay, resulting in International technologies. Condition monitoring is required to ensure wasted electricity. At GF the operators are pumps are running in the most efficient responsible for monitoring the water level Acknowledgement combinations and that any mechanical of the forebay and ensuring that the level This article was presented at the 2012 ICUE, problems are identified quickly to ensure is kept constant. Due to stopping the GD Cape Town, August 2012 and is reprinted timely preventative maintenance. Fig. 4 pumps in the evening the "watershortage" with permission. shows the condition monitoring screenshot effect will reach GF pump station the for individual pumps. Typical data recorded next morning between 05h00 and 07h00. Contact Dr. Gerhard Bolt, and logged include vibration, bearing and Therefore, the GF pumps also need to North-West University, Tel 012 809-0693, winding temperature, etc. be stopped in the morning hours. This [email protected]

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