Utility2Utility: Swissgrid (Switzerland)
- Feb 4, 2015 7:00 am GMT
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Swissgrid, the transmission system operator (TSO) of Switzerland, also owns the entire Swiss 380/220 kV network and is responsible for grid operations in the country. An unbundled transmission company, Swissgrid is not allowed to generate or trade power by law.
For this installment of our Utility2Utility series, we spoke with Dr. Nisheeth Singh, senior expert in grid applications at the utility about Swissgrid’s history, partnering on a grid across the EU, and new software that helps them manage this multi-country system.
Tell us about Swissgrid—its history and its function.
Singh: Swissgrid is located in Laufenburg at the northern border of Switzerland on the Rhine River. Laufenburg was the location of the first transnational interconnection for energy exchange between Germany, France and Switzerland, established in 1958 and known as the Star of Laufenburg Interconnection. On August 10, 2010 the IEEE dedicated the Star of Laufenburg Interconnection as an IEEE Milestone in Electrical Engineering and Computing.
Elektrizität Gesellschaft Laufenburg (EGL) was the first company to manage the cross-border exchange and Swiss 380/220 kV network from 1958 until 2001. From 2001 until 2006, ETRANS, a neutral, independent system coordinator founded by the regional transmission companies in Switzerland, managed the cross-border exchange and monitoring as an initial step toward market liberalization.
Swissgrid was founded in 2005 by the regional transmission companies in Switzerland as an additional step toward liberalization of the Swiss electricity market. In 2006 Swissgrid assumed network monitoring, coordination, and operations from ETRANS, while Swiss regional transmission companies maintained ownership of the network until the end of 2012. In 2013 Swissgrid became the full-fledged TSO and owner of the Swiss 380/200 kV network.
How do you blend managing partners and tech requirements across several countries?
Singh: In Europe the TSOs cooperate internationally at two levels. The first is the European Network of Transmission System Operators for Electricity (ENTSO-E, www.entsoe.eu), which is an association of all TSOs in Europe. The ENTSO-E coordinates the security and reliability of the European transmission network and creates the conditions for the single internal European market for energy producers, consumers and traders. The ENTSO-E enables cross-border trades to occur without technical and market hurdles.
The second level of cooperation occurs at Regional Security Coordination Initiatives (RSCIs), which ensures that security is maintained for the region and for each TSO participating in the RSCI. Swissgrid is a member of the TSO Security Cooperation RSCI (TSC, www.tscnet.eu), which includes 13 Central European TSOs and is based in Munich.
Swissgrid is an active member of ENTSO-E and participates in its working groups that define guidelines, best practices and requirements for secure and reliable operation. These working groups also standardize business processes and data exchange standards to facilitate cross-border trade.
Both ENTSO-E and the RSCIs manage network security in the operational planning phase for networks under its respective jurisdictions. Each TSO prepares the network model a day in advance for its network, performs contingency analysis, and publishes planned network models for use by all the participating TSOs. Each RSCI merges the individual network models produced by each TSO to create a model of the complete interconnected network. Each TSO is free to use this merged model for contingency analysis of its network.
TSC’s Common Tool for Data Exchange and Security Assessments (CTDS) performs the contingency analysis of the entire system. In the event of a contingency violation, the CTDS suggests a re-dispatch or changes in network topology. Each TSO can use the complete network model for validating or investigating the effectiveness of the recommended measures.
How has this new transmission optimization software platform helped with issues?
Singh: Swissgrid selected Nexant’s Security Constrained Optimal Power Flow (SCOPF) software as an optimization tool to minimize losses, maintain voltage profiles and generate re-dispatches to alleviate congestion. The SCOPF software product is security constrained and provides a solution that is N-1 secure. An important part of our core business is to keep the network secure.
When congestion is detected in the Swissgrid network, the software analyzes and recommends topological measures that can reduce the loading of congested elements. If topological measures are not sufficient, then it performs transformer tap-changing and generation re-dispatch calculations to relieve the congestion.
Swissgrid also uses the same software optimization platform to plan voltage and reactive power planning in day-ahead time frame. The hourly load and generation profile is used to compute the voltage profile, which must be maintained by the generating plants or distribution-system operators.
What benefits do you expect, and have already received, from this platform?
Singh: Our cost savings were estimated to be up to approximately SFr 100,000 ($112,000) on a typical operational day.
What hurdles did you overcome and will you still have to overcome?
Singh: Data modeling and management have been the major hurdles in implementing this type of software. The TSOs’ conventions and modeling guidelines vary over a wide range; the models must be coordinated and tested before a feasible practical solution can be trusted for operator use. The data is from different sources and is in different formats with varying quality. For example, the sign convention for power flow for power injections could be contradictory in neighboring network areas. Consistent transformer modeling for the entire network is important for voltage profile and loss calculations. While most of these items have been sorted out in our own network, plausibility checks and validation of comprehensive network data are ongoing.
The hurdle at the organizational level is the lack of a cross-border regulatory framework accepted and applied by all the countries in the interconnected network. The coordination of these activities over 41 TSOs covering 31 countries is one of the major challenges for ENTSO-E. ENTSO-E is working with the Agency for the Cooperation of Energy Regulators (ACER www.acer.europa.eu) and other EU bodies toward a single European market. The organizations are addressing cross-border capacity allocation, congestion management, balancing and other important topics with network codes and legislative acts.
How are you tying this project to other aspects of your business?
Singh: The software is part of the online dispatching environment that helps the dispatcher to make decisions for maintaining voltage profiles as part of its regular activity. Day-Ahead Reactive Planning (DARP) provides the guidelines for the generators and distribution system operators to maintain the voltage.
Currently Swissgrid uses the SCOPF re-dispatch tool for internal congestion in our own network. The Contingency Analysis and Re-dispatch Tool (CART) runs at 15-minute intervals to help the dispatcher ascertain N-1 security and propose actions to alleviate it, if needed. The online network model is generated by State Estimation, which is the basis of the CART tool and runs every five minutes. The Nexant software is tuned to deliver the optimization results within this time frame.
Why invest in this type of software? What was the impetus?
Singh: Investment in this type of software is needed to fulfill the core functions of a transmission system operation. Network security is of prime importance and the actions to ensure the security of supply and reduce the costs are part of our continuous improvement process. As part of a large network, the influence of transits must be analyzed, monitored and regulated for a secure network operation. The software plays a major role as a decision-support system for the operator.
What advice would you give other TSOs faced with similar cross-border, multiple partner tech issues? Where do they start with planning?
Singh: Cross-border trades between two control areas achieve an additional level of complexity when the border is international. To succeed in coordinating the cross-border flows over national boundaries one must have approval of the national regulators who are affected by these cross-border flows. ACER, ENTSO-E and other European Commission agencies are managing this activity in Europe. In the absence of such organizations it is important that various national regulators come to a common understanding of the need and mutual benefits of such cross-border cases.
The technical issues relate mainly to data modeling. The participating TSOs must agree on a common convention, definition of data exchanges, format, and periodic rate of data exchange. The International Electrotechnical Commission (IEC www.iec.ch) provided a major contribution to solving these issues by proposing a Common Information Model (CIM) for modeling and exchange of network data.
The TSOs must also ensure that the sharing of resources and benefits are clearly agreed on and defined in advance. Since the issues relate to commercial aspects of energy trading, data confidentiality and transparency requirements must also be part of this agreement.
Read more articles from this series: