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State Estimator Implementation at PacifiCorp: Challenges and Experience. By Real time Apps Team Grid Operations PacifiCorp. Company Overview.
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State Estimator Implementation at PacifiCorp: Challenges and Experience By Real time Apps Team Grid Operations PacifiCorp
Company Overview • PacifiCorp is one of the leading utilities in the west part of United states, serving about 1.7 million customers in six western states. The company was acquired by MidAmerican Energy Holding Company in 2006. It has three primary subsidiaries: • Pacific Power - a regulated electric utility with service territory throughout Oregon, northern California, and southeastern Washington. • Rocky Mountain Power – a regulated electric utility with service territory throughout Utah, Wyoming, and southeastern Idaho. • PacifiCorp Energy - operates 70+ generation facilities in the six states that Pacific Power and Rocky Mountain Power operate in, plus two facilities in Montana, three in Colorado, and one in Arizona.
PacifiCorp EMS System • PacifiCorp’s EMS system supports operations of all three subsidiaries. • Two redundant pairs of servers reside in Pacific Power Control Center and Rocky Mountain Control Center. • SCADA, AGC, SE and other Advanced Applications are all running on a primary server and can be failed over to the back-up server in the other control center. • Every three weeks, a database with SCADA and model changes and software upgrades are integrated and tested on the development and QAS servers. • Software and database updates are deployed onto production servers after succesful testing and approval on QAS servers. • EMS system is protected with firewalls and isolated from the corporate’s main network per NERC CIP standards.
PacifiCorp Network Model • PacifiCorp Legacy EMS had eight different systems and databases. • It did not have State Estimator and other Advanced Applications before the 2006 upgrade. • It was challenging to build the model from scratch. • WECC spans portions of Canada, Mexico and fourteen Western U.S. states. • As PacifiCorp resides in this WECC region, we started with WECC planning model.
PacifiCorp Network Model (External) • Some WECC external areas are far away from our control areas and are thereby less relevant to the PacifiCorp internal models. • Using PTI Network equivalence software, most of the external model which is 69 kV and below was eliminated (with an exception for generator buses). • The backbone and most of the bulk power system model (230 KV and 500 KV) of the Western Interconnection was maintained. • Some of the 100 KV to 230 KV networks were also maintained depending on geography and how relevant they were to the internal systems, and all tie-lines with PacifiCorp.
PacifiCorp Network Model (Internal) • The PacifiCorp model has two internal areas. One area is PACE (Rocky Mountain Power) and another is PACW (Pacific Power). Three major efforts to complete the SE model: • The entire bus/branch model derived from PTI was replaced with the detailed SCADA one-line node-breaker model. The nameplate details of numerous equipment in the model were gathered to verify and update the accuracy of the static model. • Initial Load flow solutions were successfullyobtained after less than one week of load flow tuning with the vendor’s help. • Mapping detailed SCADA breaker statuses, telemetry meters of MW, MVAR, KV and Tap positions received from RTU or via ICCP to equipment in the model for the SE
PacifiCorp Network Model • The combined PacifiCorp internal and external model footprint:
Model Update and Maintenance (Why is this a Big deal?) • PacifiCorp is going through tremendous infrastructure growth especially in the Utah area of Rocky Mountain Power. • Adding new transmission lines, new wind farm generators, new load substations are included in this growth. • Updating the network model to reflect all the new changes and keeping the model and mapping in sync with the SCADA database are big issues for PacifiCorp to maintain the SE solution as valid and up-to-date.
Model Update and Maintenance with CIM DE Tool (Conversion) • The model was initially built and populated in the vendor’s source data format. • CIM DE tool was introduced later to allow the users to have better version control, model updates and CIM data import/export. • Among the first group of customers to implement “reverse engineering”: converting the model and data from source data into the CIM database. • Two sets of data and table conversion involved: • CIM/XML compliant data: those related to the pure network model; • non-CIM compliant data: including CIM extention tables for SCADA and AGC data.
Model Update and Maintenance with CIM DE Tool (External) CIM XML Files CIM XML Files CIM DB
PacifiCorp SE tuning experience • Identified and mapped measurements exactly where they are measured. • Modeled the tap changer on the correct side of the transformer. • The voltage ratio is a key for the reactive power flow in a fixed tap transformer • Assigned correct weights to the real and pseudo measurements. • Series compensators in the model caused quite a bit of a challenge during the tuning phase. • Added ZERO impedance lines to map the measurements to the bus side of the series capacitors and shunt reactors. • PACW is closely inter-tied with other utilities like PGE and BPA. This is another significant challenge we are facing with the model on the west side of PacifiCorp (PACW) • Developed a in-house tool to capture SCADA measurements snapshot from production to development system
PacifiCorp EMS Advanced Applications (Current) • State Estimator • On production Nov. 2008 • Runs every 5 minutes • 99.5% valid solutions. • Real Time Contingency Analysis • On production Nov. 2008 • Runs every 15 minutes (3 cycles of SE) • More than 1000 contingency cases • Dispatcher Load Flow • On production Nov. 2008 • Save cases are archived for up to six months. • Supports eight study users
PacifiCorp EMS Advanced Applications (Future) • Day Ahead Studies • Generating unit and interchange schedules • Load forecast data • Scheduled Outages • Dispatcher Training Simulator • DTS is a stand alone server. • Mimics the production EMS system • Provides a realistic method for training operators
Industrial Challenges • It is very important to improve the quality of field measurements. Some meters have not been checked out for a long time. • Lack of real time telemetry on observability of SE. Adding new meters and meter replacements in the internal area require huge commitments in money and resource. • How to get changes quickly reflected in the model is a very challenging task. More processes and coordination need to be defined. • New changes in the external area of the model require information sharing among utilities. Such tools or agreements are not yet readily available. • Field changes have to be mirrored in the EMS real time database. Especially for those non-telemeter pseudo breakers. • The robustness of SE is still a very important subject.
Real-Time Applications Team Members • Madhukar Gaddam is Senior Applications Engineer in Real Time Applications at PacifiCorp. He previously worked in ABB, AREVA and CMC India. He has Masters in Electrical Engineering (Power systems) from Indian Institute of Technology, Kanpur, India and is a Senior Member of IEEE. • Rick Nielson is Lead/Senior Engineer in real time Applications group at PacifiCorp. He previously was with Utah Power and Light. He has a Bachelors degree in Electrical Engineer from the University of Utah in Salt Lake City, Utah. • Giridhar Valmikamis a Sr. Power System Consultant working for CompuSharp Inc. He was previously with Exelon Corporation, Chicago. He has a Masters degree in Power Systems from NIT, Warangal, India and is a Member of IEEE. • Peng Liis Principal Engineer and Real Time Applications team lead at PacifiCorp. He previously was with Canadian Space Agency, ABB and Nortel Networks, He has PhD degree in Electrical Engineering (Control Systems) from University of Ottawa, Canada and is a Member of IEEE and Senior Member of AEE.
