Managing the process and the power systems that serve it through a single integrated control system can cut costs while giving a much better overview of the total plant. Laya Sathyadevan explains.
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Managing the process and the power systems through a single integrated control system can cut costs and give a better overview of the total plant. Image from ABB. |
Traditionally, the systems that serve process automation and power automation within the same plant are separated, both by a lack of common communication and architectural standards as well as organizational differences between departments.
Intelligent electronic devices (IEDs) are microprocessor-based controllers of power system equipment. They can communicate with the automation system as well as with each other to give an overall picture of what is happening to the process or power supply system. IEC61850 communication interface can efficiently handle this data over Ethernet. Exchanging the same amount of data between plant devices using traditional communication interfaces will require extensive cabling.
Imagine a typical small oil platform with a 10-bay medium voltage electrical system. Signalling between the bays, to and from the automation system and for other tasks, can require around 980 wired connections. When we also consider the large number of available protocols, the bandwidth and cost-efficiency of this approach is very limited, and could result in solutions having to be implemented on a project-by-project or even device-by-device basis. Furthermore, multiple systems mean multiple databases, additional engineering tools, different operator stations, and more system administration and maintenance.
Today, this barrier is a costly reality for many operators of offshore platforms and FPSOs, which may use a large number of communication protocols, such as Modbus and Profibus. If a device needs to be integrated to the control system, it could require a solution designed just for that single device. Transferring data such as valve positions and thermal alarms between the process automation system and the power automation system will require a lot of hard wiring.
Electrical integration
This barrier is one that can be eliminated through electrical integration, which means integrating process automation and power automation into the same plant control system. This integration is based on devices that use IEC 61850 interfaces to transfer control or power data, saving up to 30% on cabling costs compared to hard wired systems. This creates a single automation environment that unifies the control of process-related equipment as well as protection, control and monitoring of substation equipment and power transmission and distribution. Integrating the process automation system with the power automation system allows a single overall strategy in the areas of engineering, operations and maintenance.
The economic benefits of electrical integration can run into millions of pounds, either through increased production or reduced operating costs. IEC 61850 interfaces also support redundancy, making the integrated power and control system more tolerant of failures. During the lifetime of an oil and gas platform, various components of the integrated power and control system will have to be exchanged or replaced. Over time, the system may also cope with integration of new components from the same or new suppliers or it may have to be extended. Irrespective of these changes, interoperability must be maintained. The data structure of IEC 61850 has been specifically designed to achieve this.
One drawback of this integrated system approach is that IED attributes, such as parameter settings, are managed by tools specific to each IED manufacturer. This means that using IEDs from several vendors will increase the number of tools needed to support the system.
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The control of drives, intelligent MCCs, medium voltage switchgear, protection and control IEDs integrated on the same system increases visibility of the process, asset management of electrical devices, better interfaces with process control and improved operational procedures. |
Electrical integration based on open standards
The difficulties of electrical integration have been largely removed with the advent of IEC 61850. Acknowledged as the global communication standard in substation automation, it represents a huge step forward in simplifying the integration of protection and control IEDs.
With its standardized model of the IED and its data and communication services, IEC 61850 ensures interoperability between electrical devices from different vendors and is able to replace all the typical protocols found in the substation automation domain. Based on Ethernet technology and providing flexible and open system architecture, IEC 61850 makes the application future-proof over entire system lifecycles.
Electrical integration extends the typical scope for asset management tools from just instrumentation into electrical power generation and distribution as well. The resulting architecture provides operators and maintenance personnel with current process information plus all relevant electrical asset information. All information sent via IEC 61850 interfaces is available as real-time data. This can be customized so that, for example, the IED sends data only every five minutes. The architecture also offers remote access to all equipment diagnostics from the same maintenance workplace.
To achieve this, IEC 61850 uses a mainstream communication technology, manufacturing message specification (MMS) over Ethernet. This standard specifies two main types of communication; vertical communication between the control system and the IEDs and horizontal communication from IED to IED.
Vertical communication uses the full MMS stack and is intended for the vast amount of data shared between the control system and the IEDs. Horizontal communication uses the special generic object orientated substation event (GOOSE) messaging, a data transfer method that removes the delays inherent in traditional hard-wire signals, allowing high-priority data to go directly between the IEDs.
Savings
Major benefits of electrical integration include reduced investment cost through one integrated system, improved operator effectiveness and collaboration across all areas of the plant and reduced maintenance costs through using one common maintenance strategy for the entire plant.
It can also provide an enhanced energy reduction program by improved visibility into power consumption. For industries such as oil and gas, 24/7 availability and reliable electrical supply are paramount. Integrating the electrical system into the Integrated Control and Safety System (ICSS) using IEC 61850 technology gives the user an excellent overview of a platform’s electric power assets, as well as a large amount of data that allows ready diagnosis of faults.
The main objective of a power management system is to avoid blackouts, especially those with in-house generation, critical loads or insufficient supply from the electrical grid. One critical functionality of a power management system is load-shedding; keeping critical loads running should incoming power be lost. Non-critical loads are shed to keep critical parts of the plant running.
With electrical integration, load-shedding applications are now easier to design and can have an even faster response time compared to hard-wired solutions. Systems that can help achieve this include ABB’s System 800xA, the first process-control system on the market to support the IEC 61850 standard. Its AC 800M controller functions, as an IED, allow it to communicate horizontally with other IEDs via GOOSE. Load-shedding can be implemented using an Ethernet-based solution, which means faster trips, monitoring of trip data quality and reconfiguration of trip logic without re-wiring. This allows a faster response to power glitches, giving increased plant uptime by preventing blackouts.
Cutting the cost of power
With access to all critical electrical data, cost-sensitive producers can reduce their total consumption of electrical power significantly. An integrated system enables plant operators to see and understand power usage in a more coordinated manner, allowing new energy-saving opportunities and allowing existing reduction programs to be improved. An increase in power consumption by a unit or area due to equipment malfunction and wear can quickly be remedied, while better visibility of power consumption and costs allows easier energy audits and benchmarking.
Integration in action
An example of electrical integration in action offshore is an ICSS for an FPSO operating in the Jordbaer field in the Norwegian sector of the North Sea. Based on ABB’s System 800xA, this uses 14 AC 800M and AC 800M HI controllers in redundant configurations, providing an integrated solution for hull side (vessel control and safety) and topside (process control and safety).
The days of treating control and power as two separate entities are surely numbered and the progressive company seeking to cut costs and gain better visibility will increasingly come to see them as inextricably linked and part of a greater whole.
Laya Sathyadevan is an oil and gas systems engineer at ABB UK. She is currently working on QGC project in Australia and BP Caspian project where IEC 61850 communication is used to integrate process and power automation systems. Sathyadevan has a Master’s degree in Control Systems from Imperial College London.
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