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1、外文翻译原文：Measurement of Transmission Line Parameters from SCADA Data G. L. Kusic and D. L. Garrison Abstract-Transmission line equivalent circuit parameters are often 25% to 30% in error compared to values measured by the SCADA system. These errors cause the economic dispatch to be wrong, and lead to
2、increased costs or incorrect billing. The parameter errors also affect contingency analysis, short circuit analysis, distance relaying, machine stability calculations, transmission planning, and State Estimator Analysis. An economic example is used to demonstrate the affect of transmission line erro
3、rs. SCADA measurements from several utilities are used to compute the real world value of the transmission line parameters. State Estimation with the estimated parameters is compared to the computations using the theoretical values. Index TermsSCADA Measurements, State Estimation, Transmission Line
4、Parameter Estimation I. INTRODUCTION Utilities in most instances use theoretical values for line parameters calculated from ideal line geometry such as height of conductor above flat, constant resistance earth. Earth resistivity is variable with terrain. Conductor sag effects are impossible to estim
5、ate over hilly terrain. Usually shield wires are grounded at each tower instead of floating over the entire line length. Line resistance varies with current, the ambient temperature and wind effects. An outage is required to measure the line charging equivalent capacitance, only if one-sided excitat
6、ion does not cause too much voltage rise on the open-circuit end. Construction of new parallel lines with mutual coupling, affects old database values. The series reactance of a transmission line is rarely measured, so the value used is for an ideally transposed line. Lines are not transposed becaus
7、e of the added construction cost to mechanically alter positions of the conductors with respect to the support poles every 1/3 the distance. With all of these variations from ideal conditions, and few real measurements, utilities often have as much as 25% to 30% error in their database parameters co
8、mpared to the real world values. Utilities use MW and MVAR metering for revenue. Transmission line losses are usually less than 3% of the total generation. However, line parameters from a theoretical database are used to calculate loss coefficients, or determine the incremental loss factors, in orde
9、r to set the dispatch point for generators (output power). If accurate values of line parameters re-allocate the generator powers, and reduce transmission losses by 0.1%, this translates into immense energy savings over years of operating the power system. For example, at 0.1% savings, a large utili
10、ty transmitting 10000 GWh annually, 0.6 Load Factor, fuel at $20/MBTU and 10.5 Mil rate, may save $11 Million per year for bulk power in the eastern U.S. Monitoring the state of the power system is a major security function of the computer system used at the central control center (dispatch center)
11、of utilities. Voltages and power flow on lines and buses in the control area of the power system are monitored on the order of every 2 seconds. If the measured data are beyond safe operating tolerance limits, the alarms generated must be cleared by the dispatcher through switching line compensators
12、such as capacitor banks and shunt reactors, adjusting variable tap transformers, or transferring generator output, etc. So that dispatcher action can be based on reliable and complete information, measurements of voltages and power flow are processed by a State Estimator which detects faulty measure
13、ment transducers (bad data) and fills in lost measurements when Remote Terminal Units (RTUs) have interrupted signals. State Estimator calculations are based upon theoretical values for transmission line parameters. Errors in the analytical values for transmission line parameters limit the State Est
14、imators capability to detect bad data, and make it ineffective as a monitoring tool. With transmission line errors, the normalized residuals are larger than they should be. At least one utility adjusts its line parameter database to match the real world transmission lines in order to improve the sta
15、te calculated. II. AN ECONOMIC EXAMPLE Consider the 5 bus transmission network shown in figure 1, where the cost of generation is bid as shown for 4 busses. The total load is 669 MW and located at busses B,C, and D. The transmission line flows as calculated for loss-less lines 1 is shown in figure 1
16、. The flow on transmission line XED = .0297 is limited to 240 MW. The other transmission line reactances are XAB = .0281, XBC = .0108, XCD = .0297 XAD = .0303, XAE = .0064 and are loss-less. The open arrows in figure 1 indicate injected power, and the black fill arrows indicate load at the bus In figure 1, of all the Locational Marginal Price (LMP) bids for generation, the 600 MW $10/MWh at bus E is completely utilized before the 69 MW a
