With the application of the international standard IEC 61850-9-2, a new era of substation automation has been introduced and ABB is recognised as one of the leaders of this technological revolution as its digital substations are achieving new successes in the field.
Stefan Meier, Digital Substation Product Manager, ABB, presenter of Engerati’s webinar, “We are bridging the gap-Enabling digital substations” describes the evolution to the digital substation and its benefits and opportunities for the utility.
Substation automation and the challenges
Meier introduces the webinar by pointing to the challenges that utilities face when it comes to substation automation in the 21st century. He lists these as:
An increasing demand on the refurbishment of substations
Grid transition in energy and communication
Growing time and cost pressures when carrying out projects
Better utilization of existing assets
Growing expectations on transmission system availability
Safeguarding investment over the whole life cycle
Sustainability in the qualification of operators and suppliers.
The evolution to the digital substation
Meier explains that there are two parts in the evolution of a digital substation:
The transformation from a wired to an optical communication network
The evolution of the current and voltage transformer from conventional current transformers (CTs) and voltage transformers (VTs) to Non-Conventional Instrument Transformers (NCITs). He discusses the move to new applications like combined current and voltage NCITs for metering and protection. Today, standardized integration of protection, control and metering with the IEC 61850 standard is possible.
The key elements of today’s digital substation include:
A substation automation protection and control system with IEC 61850 station bus
IEC 61850 process bus which connects the switchyard to the protection and control system
Standalone merging units which bridge the gap between the analogue and digital world. This is compliant to IEC 61850
NCITs increase safety and reduce footprint.
Benefits of digital substations
During the presentation, Meier discusses the benefits that a digital substation offers.
During the installation phase, these include:
Standardized and factory-tested panels
Late customization-even after project delivery (all digital communication is based on IEC 61850)
Material reduction (less cabling and space reduction for instance)
Outage time reduction (faster installation through pre-tested process bus systems).
The benefits experienced during the operational phase include:
Increased safety (digitizing signals at their source reduces the risk of electrical hazards)
Effective maintenance (more supervision is available, enabling a better understanding of operational failures in assets)
Easier maintenance (upgrading equipment with less need for outages)
Standardized process interface (fast replacement process).
Digital substation –the opportunities
The opportunities that the digital substation offers include an 80% reduction in copper cabling in transmission level air insulated substations (AIS). This is done by replacing the long stretches of copper with fibre optic cables and replacing horizontal wiring between intelligent electronic devices (IEDs). Copper cables remain for power supply and short connections between primary apparatus and marshalling kiosks in the switchyard. Connections between primary apparatus and process IO modules are reduced as fewer independent connections are needed.
Transportation of material is also reduced. Over 30 tons less material is transported to the site for an average sized transmission level substation. The weight of the fibre optic cabling is around 90% less than the copper cables it replaces. If CTs are replaced by optical ones, almost 80% weight reduction on CTs is achieved.
Another plus is less installation time (40%) of new protection and control systems because there are fewer panels to install and less cables to be pulled, connected and tested. There is also a reduced feeder outage time (40-50%) during secondary upgrades.
There is also a 30-60% reduction in space needed for protection and control panels.The same number of IEDs need less space due to the absence of conventional IOs (input/output system). Also, the higher integration of control and protection functionality allows for further space reduction.
Depending on the substation layout, the switchyard footprint can also be reduced by 50% due to using circuit breakers with integrated disconnecting functionality and optical current transformers.
Experiences in the field
During the webinar, Meier points to various programmes that ABB offers for digital substations and describes the features of each in detail. A few examples of ABB solutions implemented around the world are highlighted and their merits discussed in detail during the webinar. A brief overview follows:
Australia-NCITs and process bus (NCITs for gas insulated switchgear)
For Powerlink, Queensland, Australia, this project presented a real-life NCIT experience. 350pcs CP-type sensors for current and voltage measurement was installed in 6 substations. These were in continuous operation for over 15 years with a proprietary communication system. Not one of these primary sensors failed. The voltage levels are 275kV and 325kV.
Switzerland-IEC 61850-9-2 process bus and NCITs (First NCIT and process bus installation)
For EGL, Axpo, Switzerland, this involved an NCIT and IEC 61850-9-2 pilot installation with ELK-CP3 NCIT for current and voltage, REL670 line protection, REB500 busbar protection and E880 revenue meters from L+G. The pilot experience involved the simple commissioning thanks to the in-built supervision features of used products. The system has been in a permanent and stable operation since 2009. Protection performance is the same as the conventional system. Measuring accuracy meets the expected class 0.2. The year of commissioning was 2009 and the voltage level 400kV.
Sweden-IEC 61850-9-2 process bus and NCITs (FOCS with disconnecting circuit breaker)
For Svenska kraftnat, Sweden, the project involved an NCIT and IEC 61850-9-2 pilot installation with optical CT, integrated in disconnecting circuit breaker and REL670 line protection. This was installed in parallel to the conventional system to assess performance and long term behaviour. The FOCS (optical CT) measurements meets the expected accuracy levels . Protection is also running stable and meeting performance requirements. Pilot was followed by the official release of life tank breaker with integrated optical CT. The year of commissioning was 2010 and the voltage level 400kV.
Taiwan-IEC 61850-9-2 process bus with SAM600 (Standalone merging units in existing substation)
For TPC, Taiwan, the project involved the SAM600 installation in an existing 161kV substation, RET670 and third party protection IED with IEC 61850-9-2 process bus, and verification of correct operation compared to a traditional installation. The equipment was installed and successfully commissioned in January 2015.
In conclusion, Meier says that ABB’s intention is to bridge the gap by connecting technologies, data and people. “We are enabling our customers to take the step from the conventional system towards the modern digital substation.”