Global SIPS Experience

Authors: V. Madani, Pacific Gas & Electric, D. Novosel, Quanta Technology, and M. Adamiak, General Electric, USA

Local protection systems arrest the propagation of the fast-developing emergencies through automatic actions and are applied to address equipment specific or local system problems. Local protection systems are not engineered to address large-scale power system problems, or to arrest the system from large scale cascading events.
The trend in power system planning is to develop tight operating margins, with less redundancy. At the same time, addition of renewable energy resources, interchange increases across large areas, and introduction of fast reactive control devices make the power system more complex to operate.

The fundamental changes in the design and operation of the electric power system require that system-wide protection solutions be integrated as part of the overall solutions to prevent disturbance propagation.
As a result, automated schemes have been designed to detect one or more predetermined system conditions that would have a high probability of causing undesired stress on the power system.
Examples of large scale blackouts in the past decade published in a December 2005 IEEE Spectrum article by V. Madani and D. Novosel have shown that the risk of such events (product of blackout probability and the associated cost) is no longer acceptable, as they have led to very large and unexpected social and financial consequences.

Reduction of the risk of large system-wide disturbances and blackouts requires that system protection function be approached with the assistance of modern technologies in support of preserving system integrity under adverse conditions.
These schemes, defined as system integrity protection schemes (SIPS), are installed to protect the integrity of the power system or strategic portions thereof, as opposed to conventional protection systems that are dedicated to a specific power system element. The SIPS encompasses special protection system (SPS), remedial action schemes (RAS), as well as other system integrity schemes, such as underfrequency (UF), undervoltage (UV), out-of-step (OOS), etc. These schemes provide reasonable countermeasures to slow and/or stop cascading outages caused by extreme contingencies.

Advanced detection and control strategies through the concept of SIPS offer a cohesive management of the disturbances.
With the increased availability of advanced computer, communication, and measurement technologies, more “intelligent” monitoring and arming equipment can be used at the local level to improve the overall response. Traditional dependent contingency/event based systems could be enhanced to include power system response based algorithms with proper local supervisions for security.

In 2006, the System Protection Subcommittee of the IEEE Power System Relaying Committee (PSRC) started an initiative to update the industry experiences on SIPS by creating and widely disseminating a new survey to attract as wide a response from the industry worldwide, a comprehensive effort of IEEE and CIGRE representation to cover a worldwide base of responses.

Survey Approach
The survey was intended to compile industry experiences with a category of protection schemes designed to protect the integrity of the power system; system stability, maintaining overall system connectivity, and/or to avoid serious equipment damage during major events. The survey was designed to provide guidance for future system implementers based on what exists today as well as operating practices and lessons learned. Our industry has long recognized system vulnerabilities, and is energized to promote grid reliability with SIPS being a key element. The responses to this survey can assist the industry in driving towards a more robust grid design.

The survey participants were international, and the topographical structure of the power industry varies from one system to the next. For example, in some cases, the entire country is operated under a national power grid. In other cases, only the Grid Operators have participated on behalf of the entire grid. There are also many responses in a bundled or aggregate form since responses are representing a regional grid. Therefore, the total number of responses is not as meaningful as the total number of schemes reported, types of applications, operational experiences, and the technologies deployed. Care has been exercised not to have duplicate data entered.

The summary observation from the results gathered is that for the most part these schemes are accepted worldwide, are used in a variety of SIPS - from manually operated systems to very advanced and high speed schemes, all having a high degree of overall reliability, and good operational experiences. Many of the SIPS have annually or bi-annual operational history which assists in validity of the data. Several examples of more complex schemes have been included by the survey participants as part of the detailed report, which also emphasizes the wide acceptance of the SIPS.

A. Material Supplied to the Survey Participants: In addition to the questionnaire, the participants received supplementary material - the SIPS or RAS application definitions, a short review of methods to balance the operation of the power system and the main factors influencing the type of SIPS applied. This material was provided to assist the respondents with the selection of the most appropriate types of SIPS actions, and to achieve consistency when tabulating the results.

B. Survey Data: Validity of Survey Data: This survey was sent to power companies, grid operators, and Independent System Operators worldwide. The representatives of more than 100 individual power companies and bundled power systems have been tabulated. Results are presented in graphical format with a summary interpretation. The responses are from a representative cross-section of utilities in terms of type of utility, size of a power company, municipalities, national grids, and provinces.

The respondents also cover a broad geographical and Regional Council diversity within the North American Electric Reliability Corporation (NERC), as well as a significant number of CIGRE participants from different countries with completely different grid topographies (Figure 1).

The survey responses show great consistency reflecting common practices across all segments of the industry. The survey has two complementary parts, namely, operational experiences and design practices. The two parts in the survey complement each other well with the information received from the industry. The operational experiences section demonstrates the performance of the existing schemes, including discrete elements, the telecommunication system availability and associated maintenance for telecommunication dependent schemes, the operational performance and overall throughput timing for systems that have stringent performance requirements. The engineering, design, and implementation section of the survey responses demonstrate how the SIPS have become an integral part of the technological advancements in power system manufacturing of multifunction protective devices, as well as the integration of advanced functions that at one time, would have been performed by discrete components. The survey results also highlight the need for better system monitoring, advanced tools, and advanced applications.

BeijingSifang June 2016