Modern Equipment for Recording and Analyzing the Events in Electric Stations

Transcription

1 Modern Equipment for Recording and Analyzing the Events in Electric Stations ANGELA IAGAR, GABRIEL NICOLAE POPA, CORINA MARIA DINIS Department of Electrotechnical Engineering and Industrial Informatics Politechnica University Timisoara Revolutiei Str., no 5, Hunedoara, ROMANIA {angela.iagar, gabriel.popa, Abstract: - Among the most important components of SCADA systems used for the electric stations control and protection are also the equipments for disturbances recording and analysis. In this paper is presented the Compact Digital Recorder (CDR) designated for recording and analyzing the events that occur in electric stations operation. The data stored in the internal CDR memory can be extracted on a PC by program CDR Link for Windows, and for analyzing the disturbances can be used the program Focus for Windows. Key-Words: - electric stations, control, protection, compact digital recorder, disturbances analysis 1 Introduction In Romania, according to TRANSELECTRICA strategy (Romanian Transmission and System Operator), for managing the electric transport and distribution grid is used an EMS/SCADA system (Energy Management and Supervisory Control and Data Acquisition). This system has a hierarchical, decentralized, distributed and redundant architecture. Fig.1. Principle diagram of an EMS/SCADA system An EMS/SCADA system contains [1,2,3]: a). measuring components (for electric grids are measured the voltages, currents, active and reactive powers, frequency, as well as the active and reactive energy); b). drive and automation components (for electric grids: switches, circuit breakers, disconnectors etc.); c). hardware components: computers, printers, plotters, monitors, synoptic displays, process management modules, PLC control modules, storing units (discs and/or magnetic tapes) etc; d). software components: operation systems (in real time, or not), data collecting systems, database management systems, simulation programs, communication programs, archiving/data restoration programs; e). communication components: - LAN networks (Local Area Network: coaxial cables, UTP, fiber optic cables, network cards); - telephone lines; - terrestrial radio communication equipment (emission-reception stations, transmission relays); - communication equipment. The measuring components could be simple transducers connected to an analogue-digital conversion unit, or can be instruments with digital output. The digital value of measurement is taken by a RTU (Remote Terminal Unit), which evaluates the measurement result (is made a verification to frame within the preestablished measuring limits); for some usual cases RTU initiates the performance of some controls and communicates the measurement results to the processing central system. One of the most important components of EMS/SCADA systems is the database management system. The drive and automation components are connected to the RTU tele-transmission terminal units or to PLCs, which, based on the evaluation results, or based on the controls arrived from the processing central system control the performance of some operations. RTUs are local decisional modules that can initiate some critical or ISSN: ISBN:

2 routine operations. The hardware components offer the processing, storing, enter, display and data printing support. From safety considerations are used redundant elements to prevent the data loss or operations interruption. The software components allow the data monitoring, visualizing and processing. Some of these components can initiate physical operations, such as controlling of some drive and automation elements. The communication programs, beside the electronic communication support, ensure the connections between different system elements. Provided that the communications ensure the system s vital data flux, are used redundant means to prevent the system s partial or total drop. EMS/SCADA functions within the energetic system are: data acquisitions and exchange; chronological recording of events; data automatic processing; post fault analysis; real-time database updating; maintaining the database with historical information regarding the system operation; tele-control; warnings and alarms; user interface [4-7]. Further is presented the Compact Digital Recorder designated for recording the events that occur in electric stations operation. The data stored in the CDR internal memory can be extracted on a PC by the program CDR Link for Windows, and for analyzing the disturbances can be used the program Focus for Windows. 2 The Compact Disturbance Recorder When a disturbance occurs in electric stations, it takes place a variation of the analogue and binary parameters. This variation is recorded by the acquisition (scanning) equipments, from which category is also the Compact Disturbance Recorder produced by TELECOMM Bucharest [8]. CDR has 32 numerical inputs and a variable number of analogue inputs, at the user s request: 8/12/16, usually designated for monitoring of some alternate current lines. The CDR data are extracted by means of the CDR Link for Windows program, in form of some specific files.cff. These are transformed by means of the Focus for Windows program in files of.ffw -type, compatible with this visualizing and interpretation application. At occurrence of a fault condition, the scanning frequency increases, to allow a more detailed analysis of the phenomenon. Fig.2. Logic operational diagram of the acquisition, extraction and analysis system of the events from an electric station CDR records the disturbance data and events during: t recording = t Pre + t Fault + t Post, (1) where: t Pre - pre-fault recording time; t Fault fault recording time; t Post post-fault recording time, or: t recording = t Pre + t Lim, (2) depending on the criteria that stops recording. Fig.3. Disturbance s recording time The equipment performs recordings with a programmable sampling rate, within milliseconds. After releasing the first trigger signal and starting recording, it continues the monitoring of inputs and appearance of trigger logic signals. Any trigger signal determines the extension of the post-fault time. Recording is finished when in the pre-established quiescent period is not recorded any logic trigger signal. 2.1 Trigger signals The trigger signal represents any event that can trigger the start of a recording. The trigger signals can be numerical or analogue Trigger signals on numerical inputs The trigger signals on numerical inputs can be selected at passing 0 1, 1 0 or at any change. In the next figures (fig.4,5,6) are presented the trigger signals on numerical inputs. ISSN: ISBN:

3 For the lower level is established a typical delay (3/4 of a period), when, if it wasn t recorded any instantaneous value higher than the minimum prescribed one, the lower limit is declared exceeded (fig.9). Fig.4. Numerical input selected at passing 0 1 Fig.5. Numerical input selected at passing 1 0 Fig.6. Numerical input selected at any change Fig.7. Numerical input selected to generate trigger Trigger signals on analogue inputs Analogue inputs are inputs that undertake (usually) the alternate current/voltage signals. For these, could be mentioned two trigger levels: a lower level and a superior level. For the superior level, the exceeding statement is made at the third sample with the value higher than the prescribed level (fig.8). Fig.8. Trigger statement on analogue input at exceeding the maximum prescribed value Fig.9. Trigger statement on analogue input at exceeding the minimum prescribed value When starting CDR, it s assumed that all input signals are in the normal area, e.g. between the lower trigger level and the superior trigger level. From this moment starts the monitoring of each input in part. 2.2 Recording types A recording is composed always from two parts: - first part, of pre-fault (up to the appearance of the logic trigger signal); - second part, of post-fault (after the appearance of the logic trigger signal). Pre-fault is treated identically for both recording types. The pre-fault length is always fixed, selectable by the user within samples, in steps of 50 samples. The total time (of pre-fault or post-fault) is obtained by the formula: t = sample number sampling rate (3) Fixed length recording The feature of this recording type is the fix length of the total recording time. The total recording time (in samples) is selectable from the following available values: 1000, 1500, 2000, 3000, 5000, 8000, 12000, 18000, 25000, and samples. These values represent the total recording length. From the total recording length, pre-fault shall have the length selected distinctly, and the post-fault length will be the rest of samples: post-fault samples = total samples pre-fault samples (4) During post-fault, the equipment monitors all the numerical/analogue inputs, declares all the logic trigger signals, but these do not affect in any way the operation mode. ISSN: ISBN:

4 Fig.10. Operation mode in case of fix length recording and long time gaps between trigger signals Fig.12. Operation mode in case of variable length recording and long time gaps between two recordings In fig.11 is described the recording mode in case when the time passed between the end of a recording and a new trigger signal is higher than the selected pre-fault time. In this case, all the recordings are complete and distinct. Fig.13. Operation mode in case of variable length recording and short time gaps between two recordings Fig.11. Operation mode in case of fix length recording and short time gaps between trigger signals Variable length recording The sole analogy with the precedent case is the fix redefined length of the pre-fault duration. The total postfault length will result depending on the trigger selections made, the mode in which the fault is developed. The reference element is this case the quiescent period, selectable by the user from the values: 100, 200, 400, 500, 1000, 1500, 2000, 2500, 3000, 5000 and 6000 samples. After declaring the first trigger signal and starting recording, will be continued the monitoring of inputs and appearance of logic trigger signals. Any trigger signal determines the extension of the pos-fault time. Recording is ended when in the pre-established quiescent period is not recorded any logic trigger signal. The same linkage situations for recordings could appear as for the fix length recordings, with the same distinct cases, treated in fig.12 and CDR link for Windows [8] CDR link for Windows is the program designated to connect the Compact Disturbance Recorder equipments to the PC for: - determining the operation mode of CDR equipment; - transferring the available recordings in the CDR s memory; - modifying the equipment s work characteristic; - matching the equipment s real time watch. Connecting is made always by means of a serial line (COM1 COM3) available on PC: directly, by means of a modem, respectively by using connecting equipment through FieldBus (AFB). The operation mode of CDR link for Windows program respects entirely the Windows work principles. 3.1 Menus of CDR link for Windows program Fig.14. Main window: menu and toolbar ISSN: ISBN:

5 Buttons description and their actions Action Long recording description Simultaneous generation CDR and FFW Connecting parameters Exit Parameters take-up Parameters transfer Recordings take-up Recordings saving Recordings mark-up FFW conversion ComTrade conversion Timing Distance trigger Distance reset Button Fig.15. Main window: parameter dialog pages Table 1 4 Focus for Windows [9] Focus for Windows is a programs package designated for visualization, analysis, interpretation and printing the recordings performed in electric stations with equipments of digital perturbograph type. Each parameter is associated with a logic channel, a set of value segments (pre and post-fault) and auxiliary information. These are components of a focus document. The Focus program provides an abstract of the fault analysis through a disturbance report. The quantities (analogue and numerical) acquired by CDR can be graphically visualized with Focus for Windows program. The program provides, also, the voltages and currents phase diagrams, and their spectral analysis. There are two types of menus used within the program: static menus and contextual menus. The static menus provide general (global) options regarding the focus documents. The contextual menu allows the obtaining of information about a channel (about a visible quantity) as well as performing of specific operations on the respective channel (amplification on abscise, on ordinate, color setting, graph line thickness setting etc.). Further is presented an example of focus document in case of a single-phase short-circuit with ground on LEA of 400 kv Sibiu. In fig.16, the marker 2 indicates the time moment t=- 33 ms, characteristic to the pre-fault period. At this time moment is noticed a slight decrease of the voltage on phase 2 (UL2=218.2 kv) compared with the voltages on the other phases (UL1=236.4 kv, UL3=240.8 kv). The current on phase 2 (IL2=1.314 ka) has a higher value (IL1=331.2 A, IL3=401.2 A). The homopolar voltage U0 and the homopolar current have high values (U0=111.8 kv, I0=1.344 ka), that indicate a fault with grounding. The phase diagrams window is noticed both the modification of the current s effective value on phase 2, and the phase differences between currents on phases. The phase differences between the phase voltages are a little modified against the normal operation. In windows U0 and I0 is noticed the beginning of the homopolar voltage increase, respectively of the homopolar current. Thus, marker 2 catches the incipient stage of a single-phased short-circuit on phase 2 (L2) with the ground. Are noticed especially the facilities offered by the FOCUS program in analyzing the analogue and numerical quantities, the visualization of the effective and vector values made in real time. Further the analysis of the disturbance report issued by the Focus program can be determined the causes, amplitude and consequences of the appeared disturbance. ISSN: ISBN:

6 Fig.16. Focus document in case of a single-phase short-circuit with ground on LEA of 400 kv Sibiu 5 Conclusion The EMS/SCADA functions within the energetic system are: data acquisitions and exchange; chronologic recording of events; data automatic processing; postfault analysis; real-time database update; maintenance with historic information regarding the system s operation; tele-control; warnings and alarms; user interface. The Compact Digital Recorder (CDR) allows the recording of events that appear in electric stations operation. Instrumentation of fault quantities is achieved by the Focus for Windows program. Further the analysis of the disturbance report issued by the Focus program can be determined the causes, amplitude and consequences of the appeared disturbance. References: [1] D. Bailey, E. Wrigh, Practical SCADA for Industry, Elsevier, ISBN: , [2] Klaus-Peter Brand, et al., Substation Automation Handbook, Utility Automation Consulting Lohmann, [3] H. Ito, K. Kaneda, K. Hamamatsu, T. Tanaka, K. Nara, Improvements in Dependability and Usability for a Substation Automation System with Redundancy, WSEAS TRANSACTIONS on SYSTEMS, Vol. 7, Issue 10, 2008, pp [4] Klaus-Peter Brand, The Standard IEC as Prerequisite for Intelligent Applications in Substations, IEEE/PES General Meeting, USA, [5] M. Dobriceanu, A. Bitoleanu, M. Popescu, G. VlăduŃ, Practical Aspects Concerning the Monitoring of the Electrical Stations, WSEAS Transactions on Information Science and Applications, Issue 11, Vol. 2, 2005, pp [6] I. Zolotová, L. Landryová, Knowledge model Integrated in SCADA/HMI System for Failure Process Prediction, WSEAS Transaction on Circuits and Systems, Issue 4, Vol. 4, 2005, pp [7] V. Matz, T. Radil, P. Ramos, A. C. Serra, Automated Power Quality Monitoring System for on-line Detection and Classification of Disturbances, IEEE IMTC 2007 Instrumentation and Measurement Technology Conference, Warsaw, Poland, May [8] *** Compact Disturbance Recorder, TELECOMM, [9] *** Focus for Windows v2.0, TELECOMM, ISSN: ISBN: