Increase of power supply to 132 kV electrical network in the Port of Durban (South Africa)

Introduction to power supply

The electrical power supply to Durban Harbour is from EE’s 33 kV Congella and Old Ford Road substations with 17 MVA capacity limit in each incomer due to infrastructure exceeding its design lifespan. The 33 kV voltage supply at the intake substations that is Durban Harbour Intake (DHI) Substation and Stanger Street Substation (STS) is stepped down and redistributed to 11/6.6 kV to supply Port operations and consumers in the Ports electrical network.

The supply 300 mm² oil cable to STS and DHI were installed and commissioned in the early 1970’s and 2003 respectively. The Port’s historical load profile data revealed that the 17 MVA firm supply limit was exceeded during the Port’s peak loading intervals in winter months.

This compromises the reliability and firmness of the existing network and increases the likelihood of failure. According to the Port Master Plan, the Port has expansion plans and future developments that require additional load demand which is not available in the currently existing network.

Electrical network system improvement that ensures a firm and robust network is required to cater for the additional load requirements. EE is also phasing out 33 kV as a distribution voltage to large power users.

Figure 1 – Historical Maximum Demand Load Profile for the Port

Figure 1 is a graphical representation of the Port’s historical instantaneous maximum demand load profile in comparison to the 17 MVA firm supply capacity from EE, which was exceeded during peak periods. The port network is under strain during the winter months due to high base loads caused by the refrigerated containers, which are imported/exported through the container terminals.

These high demand peaks have resulted in the Port of Durban reaching the 17 MVA capacity on the electrical network for extremely short durations of times.

An electrical power supply upgrade in the Port is required to strengthen and improve the electrical network and the proposed supply capacity from EE is 132 kV at a capacity of 80 MVA from their 132 kV Edwin Swales substation closest to the Port’s proposed 132 kV outdoor substation site. The electrical upgrade includes the implementation of SCADA system and SAS for the new substation. This will enable the monitoring and control of the electrical network.

This chapter evaluates the Port of Durban’s existing SCADA system, Substation Automation System (SAS) and evaluates what considerations need to be taken into account for undertaking this upgrade.

Modern SCADA master stations are equipped with communications architectures that integrates hardware and software in distributed systems. The real-time data transfer between various viewing computers and servers is via the control centre’s Local Area Network (LAN) platform.

On completion of data processing, the control centre completes the task of issuing control signals to the required part of the system. The Master station retrieves data required by substation equipment from remote station.

RTUs are connected physically with equipment such as switches, circuit breakers, etc. and they monitor and control these devices.

The system HMI enables the user/operator to view the entire plant status through raised alarms and status indications. Alarms are automatically detected under equipment abnormal conditions that require operator’s attention to acknowledge and resolve the conditions raising an alarm. Modern communication protocols provides data integration between master station and remote station.

The designs for SCADA systems should take into account capacity to allow the future automation of the operation of equipment to allow future substations growth and expansion of the electrical power system.

IEDs play a major role in the power systems protection because of the ability to identify the faulted area or abnormal condition in the network and isolate it as quickly as possible before any damage to the equipment is incurred.

Figure 2 – Electrical Substation SCADA Model with Protection Devices

Supervisory Control and Data Acquisition Systems

SCADA systems functions are to monitor and control remote or geographically dispersed systems or plants. SCADA systems retrieves and stores data of the status of the entire plant or substation, indicates and displays areas with abnormalities for the user/operator to take action to normalize the network.

Due to that, electrical systems are growing at a rapid rate with power plants interconnected with the power system substation.

The real-time data obtained from the SCADA system is essential for the plant operation as the user/operator can easily execute supervisory commands. It also enables the operator to execute supervisory commands. In order to allow for future substation growth, expansion and the inclusion of new application functions, SCADA systems should be designed to have sufficient capacity.

Figure 3 – SCADA Communications Architecture

This will ensure that there is sufficient capacity for adding more equipment via the primary feeders in the substation. Modern communication protocols integrate with IEDs for efficient equipment status monitoring and control during abnormal fault conditions SCADA systems enables the user/operator to easily identify the fault location in a complex electrical network, which improves plant productivity and reduces maintenance costs.

SCADA systems consists of the following main components:

1. Multiple RTUs, which are numerical relays.
2. Communication channel infrastructure.
3. Master station and HMI Computers.

Medium voltage electrical networks, building air-conditioning, standby generators and SMART energy metering systems are monitored on the SCADA system.

Figure 4 – Geographically dispersed electrical substations monitored on the Port of Durban’s SCADA system

The Port of Durban has several 33 kV substations and air conditioning plants that are monitored and controlled on the SCADA system.

Figure 4 is a map displaying various substations that are monitored and controlled on the Port’s SCADA system. The numbers on the map are explained as follows:

• 1 denotes the 6.6 kV Sand Bypass Substation.
• 2 denotes Ocean Terminal Building air-conditioning plant.
• 3 denotes the 33 kV incomer STS supplied from EE’s Old Fort Road substation.
• 4 denotes the 33 kV incomer DHI supplied from EE’s Congella substation
• 5 denotes the Port’s 132 kV proposed substation located at Langeberg road.
• 6 denotes the 33 kV Pier 2 Substation which supplies the Durban Container terminal which is the load centre in the Port.
• 7 denotes Allan Dalton substation (AD) 33 kV Substation.
• 8 denotes Pier 1 33 kV Substation.
• 9 denotes the Fynnlands 33 kV Substation.
• 10 denotes the Millennium Tower that is utilised to navigate the ships entering the Port.

Figure 5 – Substation Electrical Network Reticulation

Figure 5 represents SCADA view showing 33 kV DHI intake substation electrical network model with the 17 MVA firm capacity that is stepped down to 6.6 kV and redistributed to various Port consumers. The real time power factor values, bus bar voltages and currents on each feeder are displayed.

From this, it is easy to identify the status of the network and easily retrieve network parameters or data. The Operator is able to perform operation functions in this view such as opening or closing of circuit breakers, applying earths etc.

The Port of Durban’s SCADA platform is ArchestrA systems platform that is mainly used for industrial applications and provides features for configuration, data deployment, cyber security, communications protocols, data management and storage.

The system platform is equipped with high performance historian process that archives and keeps records of production history.

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