Expert System Development and Integration with MoniTeq Circuit Breaker Monitoring

Transcription

1 Expert System Development and Integration with MoniTeq Circuit Breaker Monitoring R. Schwabe, C. He New York Power Authority, White Plains, New York Yvan Pinard Snemo Ltd., Brossard, Canada Eric Vermette, software engineer Cybectec, Quebec, Canada Abstract Online monitoring and diagnostics of High Voltage Circuit Breakers incorporated with an expert system is becoming more attractive to reduce operation and maintenance costs, increase apparatus reliability and effectively plan maintenance. The New York Power Authority has implemented a real time circuit breaker condition monitoring system on several breaker types in critical substations. The data collected from the monitoring system is utilized to diagnose the condition of the breaker and identify abnormalities. The initial software platform and User interface required a significant effort to evaluate and analyze the collected data. It became evident that in order to efficiently diagnose the condition of the breaker, the operating platform would require a knowledge based system module to process the collected data. Collaborating with Snemo Ltd. (manufacturer of the MoniTeq system) and Cybectec Inc. (developer of the Visual Substation platform TM and Substation Modernization Platform TM ), the Power Authority initiated a project to develop and implement an expert system for the breaker monitoring system. The project included the development of rule sets for three breaker types, an expert system shell, a rule set editor and a simulator. The expert system components were incorporated into the existing Visual Substation platform. This paper aims to provide an overview of the work that has been completed, including the basic MoniTeq monitoring system, development of rule sets for three breaker types and the integration of the expert system modules into the Visual Substation platform combined with the implementation on NYPA substations.

2 Introduction In order to stay competitive in today s market, electric utilities are being pressured to reduce their overhaul and maintenance costs, which represent a significant portion of the overall costs. One way to accomplish this goal is by extending the interval between maintenance cycles and doing less maintenance, or performing maintenance based on equipment condition rather than time. The disadvantage with less maintenance is fewer opportunities to train new staff in maintenance practices. In addition, as utilities are striving to reduce maintenance costs, hiring practices have lead to the loss of experienced staff, causing the reliance on outside experts. The present trend for scheduled maintenance, which is usually based on equipment type, elapsed time, equipment history maintenance, or number of operations, is being directed more towards a Reliability Centered Maintenance (RCM) program based on a number of parameters. These can include substation and breaker criticality to the system, maintenance history and diagnostic technologies to identify problems or indications when maintenance is required. This approach provides guidance in the use of staff to target maintenance on the most critical apparatus. The use of diagnostic technologies provides an opportunity to obtain real time data on circuit breaker condition. Diagnostic technologies to identify problems or base maintenance programs are being assessed by the Power Authority and applied to specific breaker types. The condition based monitoring program is based on the use of calibrated sensors and the collection, analysis and trending of the data. By comparing the data collected by the monitoring system to that provided by the manufacturer, an assessment can be made on the breaker s condition and if any maintenance is warranted. Incorporating the data into an expert system module provides a real time assessment that can provide information to selected staff for scheduling remediation action. The prototype expert system module was embedded into the Visual Substation platform, which was comprised of an expert system shell capable of analyzing the data and notifying substation operations and maintenance personnel of abnormal conditions. The embedded simulator was utilized to validate all rules for each breaker type, following the coding in the expert system and prior to implementing the platform at the substation. The rule set editor provides the User with the capability of modifying or developing new rules and applying them. The software development has been completed at the end of 2003 while the rules validation is in the initial stage of implementation and will be fully functional by the end of 2004.

3 System Architecture The Visual Substation based expert system analyzes the data collected by the MoniTeq circuit breaker monitoring system, generates events and alarms, and notifies relevant personnel. Figure 1 shows the whole system architecture including the MoniTeq circuit breaker monitoring system, Substation Modernization Platform, Visual Substation platform, expert system module, rule editor, etc. The shaded areas indicate components that were added to the original Visual Substation platform. The Visual Substation platform can operate with or without the expert system components. Circuit Breaker Monitoring System The MoniTeq circuit breaker monitoring system was jointly developed with Hydro Quebec and is commercialized by Snemo, Ltd. The system is composed of sensors installed on the circuit breaker, one or more local data acquisition systems at the breaker (local controller) connected to a data base server (Central Controller ) that incorporates the Visual Substation Platform with the embedded Expert System modules (Expert system shell, Rule set, Rule editor and Simulator). The Visual Substation server/client architecture provides access to the database and circuit breaker sensor configuration. Fiber optic cables provide communication between the acquisition unit and the server computer. The data collected from the monitoring system is utilized by the expert system to diagnose the condition of the breaker and determine if any abnormalities exist. The Local Controller measures, converts and records the mechanical and electrical signals from sensors monitoring the parameters such as travel, pressures, temperatures, currents, voltages, and compressor operation. A unique set of sensors is developed and configured for each breaker type. Data is collected under normal operating conditions at predefined intervals and during breaker operation (DFR record). The recorded information is analyzed by the software platform and depending on the result, a diagnostic alarm report can be sent to designated staff at the site as in Table 2. The MoniTeq system is presently installed at a number of NYPA substations on three circuit breaker types that include the Westinghouse SF6 SFA double pressure (345kV and 765kV), GE Hitachi HVB (345kV) and Cogenel PK air blast circuit breakers. Figure 2 shows the MoniTeq system local controller installed at Power Authority s Marcy substation.

4 Expert System Development and Implementation In this section, the expert system development procedure for the MoniTeq monitoring system combined with the implementation on Power Authority substation circuit breakers will be described and summarized. Rule set development for specific breaker types Rule sets were developed for the three breaker types monitored by the MoniTeq system. The rules are based on manufacturer specifications and field experience. Rule sets for each breaker can be subdivided in two major categories. The first set verifies all sensor states, the acquisition state and the communication state. The second set verifies the breaker operation state. This analysis is done when operations occur and at a regular interval between two operations. A rule has two components: ʺConditionsʺ and ʺResultsʺ. The ʺConditionsʺ portion represents the conditions, with respect to input and calculated data, that will trigger the application of the rule. The ʺResultsʺ portion is a series of actions to be taken whenever the rule applies. Actions can be an event notification, an operation notification, an alarm notification, a command to a device, a state or a value modification. Table 1 provides an example of a typical rule for low air pressure used in the expert system. Once defined for a typical breaker type, the rules are saved in a template and may be re used for other similar breakers by only changing the prefix for the breaker and pole number. The open architecture of the system allows the user to define, modify, validate and organize rules. The user can also test the rules with the simulator. Figure 3 shows the rule editor used in the expert system incorporated within Visual Substation. Visual Substation and Substation Modernization Platform The Cybectec Substation Modernization Platform TM (SMP) is a substation grade intelligent gateway specially designed to integrate both existing and new RTUs, IEDs, PLCs and control centers into a single homogeneous substation automation system. It provides utilities and systems integrators with a complete solution for the automation of new substations and the modernization of legacy systems. For this application the SMP software runs on the same PC platform as the CC. Cybectec s Visual Substation is a sophisticated real time client server application that brings the power of a SCADA system to a substation. Visual Substation is utilized as the core of the central controller software for the MoniTeq system. This product was designed, and is used to control and monitor electrical installations. All inherent concepts relating to the electrical utility industry are already present in a stable and

5 flexible architecture. The system supports the acquisition of multiple sources of data or information and enables visualization and analysis with specialized tools. Two additional functions were added to the present Visual Substation product to support the specific requirements of the MoniTeq system application: Acquisition of data from MoniTeq local controller units. An expert system shell component allowing the configuration and the realtime processing of the breaker data. Expert System Shell The expert system shell was a new component added to the Visual Substation platform. The expert system is composed of two elements: Man Machine Interface ( MMI ) to visualize and configure the knowledge base ( rules ); Real time inference engine (processing). The man machine interface enables configuration of the knowledge base and real time visualization of the symptoms, rules and diagnostics states. This application could be connected to the server either locally or remotely and will be used for the maintenance of the system. The real time inference engine is implemented as a rule interpreter with the possibility of combinations and relations between different rules. A complex hierarchical structure of rules and diagnostics is supported. The expert system component will handle: Triggers to rule evaluation; Rules based on acquisition point values and/or other rules state.; Diagnostics based on rules. The triggers will initiate rule activation/evaluation. For example, a trigger could be set to operate on opening / closing operation. Upon trigger activation, all data point values associated with the processing to be executed will be frozen (snapshot) and will be used to process all algorithm calculations. If the expert system finds a problem (activation of a diagnosis), it will send the information to the main Visual Substation alarms database. Those alarms will contain a description of the diagnosis as found by the expert system. Those diagnostics will be presented to the user upon request as a document describing the problem and the possible solutions. Visual Substation already incorporates a logic point processing engine. This engine includes a script language that enables the production of new data points based on logical conditions, algorithms and mathematical functions. This function has been enhanced to include vector based mathematical functions allowing a preprocessing of the raw data acquired from the Local Controller.

6 MoniTeq Acquisition Unit Simulator A simulator as shown in Fig. 4 was developed to test the protocol implementation and to assist in the expert system rules validation. This tool will enable the simulation of any possible conditions in an easy way. The simulator is a small stand alone Windows application, presenting a simple user interface and well adapted to the task. The simulator could be sent to the end users and could be used by laboratories to design, validate and test new rules. The functions that will be supported by the simulator are: Reading, saving and creating the configuration parameters for an installation. Manually setting different points and values Manually setting DFR records ( 300 points vectors ) Mini script language to simulate sequence of events. Serial port communication (configurable) Data Acquisition The structure of Visual Substation already allows connection to multiple sources of data (IED s). The Proprietary communication protocol used by MoniTeq s local controller units (LC) are incorporated into the Visual Substation server. The acquisition subsystem supports an unlimited number of simultaneous connections to LC (limited only by the number of communication ports available on the computer). Each connection will support an individual configuration set up (communication port, speed,) and an individual signal map (list of signals connected to the LC). The acquired data is processed and integrated into the main database and will be treated as any other source of data. For example, there will be no difference between the data coming from MoniTeq s LC and data coming from Cybectec s SMP Gateway. It will then be possible to acquire simultaneously data coming from multiple sources ( IED, PLC, ), each using different communication protocols ( DNP, Modbus, OPC, ), by using the SMP ( stand alone gateway ) or the SMP PC ( software gateway ). Figure 5 shows the main interface of data source configuration for Visual Substation. Analysis and Visualization The Visual Substation tools enable visualization and analysis of the alarms and events, real time and historical data. Data points can be set up to generate alarms and events. All alarms and events are automatically time stamped and logged. The alarm and event display can be configured to provide quick recognition of problems. Filtering functions can eliminate untimely alarms. User provided icons and an alarm location diagram help reduce intervention time. Figure 6 shows the alarms and events handling interface and Figure 7 shows the alarm notification configuration interface. The State Pages function displays in real time the state and value of all the points of the system. The Trending and Report Generation functions enable the viewing and displaying of

7 historical data. Figures 8 and 9 show the DFR historical data for the air pressure of an HVB breaker and a PK breaker, respectively. With Visual Substation, different data types can be plotted in one figure as it can be seen in Fig 10, which shows how the daily average pressure changes with ambient temperature. Conclusion With a collaborative effort among Snemo, Cybectec and NYPA, an expert system for the real time circuit breaker condition monitoring (MoniTeq) has been developed and implemented on the Power Authority s critical substations. Although the expert system is still in its initial state, it shows a great potential in the automatic condition monitoring and diagnosis on substation circuit breakers. References 1. Zelingher S., Schwabe R., Landry M., Mercier A., Condition Monitoring of Circuit Breakers A Step Towards the Global Approach to Substation Monitoring, Paper presented at the EPRI Substation Equipment Diagnostics Workshop, Palo Alto, California, November 9 11, Cybectec Proposal, Monitoring System Central Controller and Expert System for MoniTeq III Prepared for New York Power Authority, August Landry M., Zelingher S., Mercier A., Schwabe R., Giradeau R., Bennett R., Lebow M., Spindle H., A Microprocessor Based Condition Monitoring System for SF6 High Voltage Circuit Breakers, CIGRE Symposium on Diagnostics and Maintenance Techniques, Berlin, April, Frechette M., Landry M., Zelingher S., Schwabe R., Predictive Assessment of Moisture Dynamics in the Context of Two Pressure Type SF6 Breakers, Eight International Symposium on High Voltage Engineering, Yokohama Japan, August Carreau D., Jolicoeur A., Rajotte C., Mont Briant M., Mercier P., Landry M., A Method for Assessing the Economic Justification of Retrofitting On line Condition Monitoring to an Existing Circuit Breaker Installation, EPRI Substation Equipment Diagnostics Conference New Orleans, Louisiana, February 1999

8 Expert system rules Breaker (BR) Short description: General description: Application Rule script: Actions: Impacts: Low air pressure in tank: pole PP The rated air pressure in the air tank of the operating mechanism ensures normal operation of the HVB breaker. A too low air pressure will cause a decrease in the speed of the operating mechanism which could affect the arc quenching capability of the circuit breaker and its dielectric withstand following current interruption. PP = A,B & C BB_PP_AIRPRESSURE_STATE = TRUE (Sensor state OK) AND BB_ACQUISITION_STATE = TRUE (Acquisition unit OK) AND (BB_PP_AIRPRESSURE_MN_AVG BB_AIRPRESSURE_LOWRANGE_HVB) / BB_AIRPRESSURE_LOWRANGE_HVB ) < 0.1 (Last minute pressure is lower than 10% of nominal low range value) If the air pressure is too low: Inspect the air system (compressor and pressure governor switch, etc.) Replace any defective parts Make the required adjustments Low operating mechanism speed Current may not be interrupted during high short circuit current Table 1. BR1: Air pressure regulation problem Low air pressure PP

9 Breaker Legend VSS New component Existing component Moniteq AU Serial Protocole LCCOM COMTRADE Maker Moniteq AU Simulator Serial Protocole LCCOM SMP Client OPC Client COMTRADE Files Visual Substation Server Data Event Alarm Data Data log Specific Calculation Module DCOM Site Configuration DB Oscillograms View Visual Substation Explorer Diag. Report View SMP-PC Point List Configuration LCCOM (.par) Expert System Module Diagnostic Report Files Visual Config Knowledge Base Data Rules file File Rule Editor Figure 1. Block diagram of software system and components

10 Figure 2. MoniTeq LC installed at NYPA Marcy substation Figure 3. Rule set editor for expert system incorporation

11 Figure 4. MoniTeq acquisition unit simulator main interface Figure 5. Visual Substation data source configuration Figure 6.Visual Substation alarms and events handling interface

12 Figure 7. Alarm notification configuration interface Figure 8. DFR historical data Air Pressure curve for a HVB breaker

13 Figure 9. DFR historical data--blast time and air consumption for a PK circuit breaker Figure 10. Trending plot of average pressure and temperature within one day

14 Type: Rule File Name: Rule name: Report Description: Nominal values: B3414_C_AIRPRESSURE_STATE B3414_MINUTEACQUISITION_STATE B3414_C_AIRPRESSURE_MN_MIN B3414_C_AIRPRESSURE_MN_MAX B3414_C_AIRPRESSURE_MN_AVG Conditions: Results: General Description: Causes & related components: Impacts: Actions: Alarm D:\...\NYPA MARCY 5HVB_PK.xml B3414_C_AirPressureSignal Air pressure signal problem, pole C, circuit breaker B3414 FALSE TRUE 'If sensor is in defective state B3414_C_AIRPRESSURE_STATE EQV FALSE 'and acquisition cycle is working AND B3414_MINUTEACQUISITION_STATE EQV TRUE for additional information only AND (B3414_C_AIRPRESSURE_MN_MIN > ) AND (B3414_C_AIRPRESSURE_MN_MAX > ) AND (B3414_C_AIRPRESSURE_MN_AVG > ) B3414_C_AirPressureSignalProblem Problem in the acquisition chain: - Defective sensor - Defective analog/digital converter - Loose electrical contact terminals - Incorrect calculations - Rules using this signal are deactivated -- Defective sensor. Check that the 4-20 mamp.cc sensor output matches the input pressure. Use a multimeter in the sensor output loop to measure the output current. Use the manometer of the device (if available) to compare the result. Make sure the DC current at the sensor terminals match the manufacturer's specifications. -- Defective analog/digital converter. Use a multimeter in the sensor output loop to measure the current coming into the A/D converter and check the characteristics. With the pressure sensor not plugged in, there should be a Vdc voltage. -- Check the electrical contact terminals Table 2 Diagnostic Alarm Report