Acceptable Functional Integration in HV Substations

Working Group B5.13 Report by  Dr. Alexander Apostolov (Convener)

The introduction of microprocessor based relays more than two decades ago resulted in a natural process of ever-increasing complexity of the functionality of different types of protection relays that expanded into multifunctional Intelligent Electronic Devices. 

The Technical Brochure covers the impact of Functional Integration on reliability, availability, refurbishment, operation, maintenance and testing of Substation Automation Systems and its relation with standardization and customization, as well as its impact on the organization of the utilities and vendors. An industry survey covering the two main points of view of Functional Integration - the users’ and the manufacturers’ provides an insight into the perception of acceptability of Functional Integration and gives an idea of the trends for the future.

The first few chapters of the report define protection and other  functions and the requirements for their implementation. The analysis shows some clear advantages of a higher degree of integration of functions in a substation automation system. These include, but are not limited to a reduction of the number of devices and consequently simplification in wiring and reduction in the number of cubicles. All these factors contribute to a reduction in the overall cost of the system, as well as improvements in the efficiency and quality of the engineering process, but may have impact on the reliability and the performance of the overall system compared to a less integrated system. Functional Integration may imply "cultural" changes for both utilities and vendors due to the massive introduction of digital technologies that are developing and changing quickly.  It also requires adaptation of maintenance methods with respect to the procedures applied to conventional bays and systems.

Testing is one of the key requirements to ensure correct operation of a protection and control system. Methods for testing of individual functional elements, complex functions, a device as a whole and distributed applications should be developed and applied, taking into consideration the possible overlapping of functions operation for the same event.

One of the primary tasks of working group B5-13 was to prepare and perform an industry survey on the acceptable level of Functional Integration. The questions in the utility survey were formed in a way that provides good understanding of what IEDs are used, what is the acceptance of integration of protection and non-protection functions and the constraints that impact the level of acceptance, as well as the impact of IEC 61850, utility organization, engineering practices and perception of the benefits of functional integration.

The manufacturers' survey questions were tailored to increase the understanding of what IEDs are developed and made available on the market, what is the acceptance of integration of protection and non-protection functions in the devices and the constraints that impact the level of acceptance. Another group of questions are related to the impact of vendor’s organization, outsourcing and perception of the benefits of functional integration.

The report includes the results from the survey based on 29 responses from utilities and 20 responses from vendors. Multifunctional IEDs seem to be generally accepted by utilities. The majority uses integration of protection and control functions even at higher voltage under the condition that the IEDs are duplicated. The advantages of Functional Integration are in engineering, application flexibility, commissioning, maintenance and addition of functions.

There is a consensus among the major manufacturers that Functional Integration reduces costs and space requirements, and improves the application flexibility.

The increasing acceptance of IEC 61850 standard and the shift of the focus from devices to functions and their free allocation will also facilitate increased Functional Integration and its acceptance. This will probably lead to totally integrated protection and control systems in the future.

The technical brochure is available from the CIGRÉ web site.  

Members of Working group B5.13

Relion advanced protection & control.
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