Sasol Mining is part of South African integrated energy and chemical company Sasol, undertaking the coal mining operations. Sasol Mining operates six coal mines that supply approximately 40 million tons per annum of thermal coal feedstock.(1) At the company’s largest colliery, the Syferfontein mine in the Secunda area, Sasol Mining identified that the ventilation shaft was not sufficient to ensure the required aeration of the mining district. To ensure uninterrupted power supply to a new ventilation shaft, they needed a new substation.
In underground mining ventilation systems are of paramount importance to ensure safe working conditions for people. Ventilation systems provide clean air, dilute and remove dust as well as natural and machine exhaust gases, and provide cooling for personnel and machinery. Ventilation systems need to run continuously 24 hours a day, throughout the year, which means uninterrupted power supply is a key requirement. The energy demand is significant and ventilation systems are currently the largest consumers of power in underground mines, accounting for as much as 50 percent of energy use(2).
ABB’s protection and control solution offers the needed functionality and flexibility - with cost reduction
For the new substation that feeds the new ventilation shaft, Sasol Mining chose a protection and control solution with ABB’s Relion® relays from the product family’s 615 and 620 series, as well as the all-in-one protection relay REX640 to be installed in the medium-voltage switchgear. This is the first installation with ABB’s Relion protection and control relays for Sasol Mining.
“A key consideration for us when deciding in favor of the Relion relays was that they offered all the functionality we need” said Divesh Ramasur, Senior Electrical Engineer, at Sasol Mining. “They are also flexible and offer large event and fault recording capabilities.”
Sasol Mining chose these protection and control relays because they offer the needed circuit breaker control functions and have arc flash protection embedded for increased safety. They also have simpler GOOSE (Generic Object Oriented Substation Event) protocol utilization and all have the R/L (remote/local) switch available on the relay faceplate for easier operation. Further, the customer chose Relion 620 series relays for motor protection. These relays offer stall protection functionality and also thermal overload protection considering the actual starting time of the motor.
The installation of Relion relays has resulted in cost reduction and reduced switchgear footprint. ”With REX640 we can use only one relay for transformer protection, whereas earlier we had to use many different relays to achieve the same level of protection” said Divesh Ramasur. “The REX640 relay has many protection functions available for transformer protection, such as low impedance differential protection, low impedance restricted earth-fault protection, sensitive earth fault protection, and tap changer control all integrated into the relay. On top of that it has many binary inputs and outputs, and the relay can incorporate many analog inputs, too”.
As a result, the footprint of the switchgear was reduced, as there was no longer the need to install three different relays to obtain the same functionality. The smaller footprint was also achieved thanks to the built in R/L switch and master trip relay, which meant that there was no longer a need to install separate switches on the switchgear panel. The cost reduction thanks to using REX640 was about 25 percent.
Mr. Ramasur also found the configurable LEDs (light emitting diodes) on the relays to be of great help to find faults quickly. He explained “A great benefit comes from the 11 configurable LEDs and even 33 configurable LEDs in REX640. They can be used to indicate which function operated, making it faster for the operator to find the fault.” Further, with the Relion 615 series (REF615) and 620 series (REM620) protection relays in the substation, the customer estimates the total costs were reduced by 10 percent.
Close-up of Relion REX640 
Relion REX640 installed 
Relion REM620 and REF615 installed 
Relion REM620 is used for motor protection 
ABB's UniGear switchgear line-up 
Outside view of the substation
On top of mining, Sasol is also involved in energy, chemicals and synfuels. ABB and Sasol have a long business relationship and Sasol has previously used Relion relays at their Secunda and Sasolburg petrochemical plants, proving their suitability for operation in harsh environments. To further ensure optimal performance, Sasol Mining chose an additional layer of protection, conformal coating, to the relays. Adding a conformal coating to the printed wired boards (PWBs) protects the electronic circuits in particularly demanding environmental conditions, such as in underground mining.
ABB’s scope of work was to supply, install and commission the equipment. Commissioning of the protection relays took place in June 2020.
To learn more about ABB’s digital substation products, please visit go.abb/digitalsubstations
1) https://www.sasol.com/about-sasol/strategic-business-units/energy-business/sasol-mining 2) https://www.canadianminingjournal.com/featured-article/abb-discusses-the-advantages-of-ventilation-on-demand/
