Economic Operation of Distributed Power Systems Within an Electric

The mentioned precalculations were performed applying two methods to derive values for turbogenerator shaft life expenditure different types of algorithms to three different types of partial following disturbances (computed off line or registered through models, allowing us to identify, for the given case, the sensitivity of torsional monitors) as compared to other possible methods (fatigue the calculated results to both computational simulating accuracy detectors or -sensors) and modeling correspondence. .orientations for future work based on these reflections as well as Among particular aspects of the data recorded during the field on the various actually proposed engineering limits for the tests the spectral analysis of output electrical power and turbine- permissible torsional fatigue caused by the rotational oscillations. The analysis of the frequency modulated synchronous machine is alternator torque measurements are worth mentioning. This spectral analysis is done for the intervals 0 to 1 sec, 1 to 2 sec, 2 to 3 simplified to the isotropic rotor case. This theory allows us to determine an equivalent mechanical impedance of the synchronous sec and 3 to 4 sec after fault inception. The main experimental results are the poor torsional eigenvalues machine, i.e., the complex ratio of the damping torque, with respect content of the output power spectrum and a good evaluation of the to the relative velocity, essentially depending on the following several modes of damping after fault clearing, to be compared with electrical parameters: .external network Thévenin equivalent circuit parameters those experienced after load rejection or after synchronization .subsynchronous machine resistance and inductance starting from no load. The paper also gives some details about special devices (e.g. Moreover, in electromechanical analogies, this mechanical im¬ torsional stresses monitor, sudden load drop generator protection) pedance simply corresponds to a parallel capacity-resistor dipole, that were checked during the real tests, together with a condensed the parameters of which are easily computable. From this theory, the influences of the network and machine description of some of the particular measuring devices that were used (two different types of on-line torsional strain measurements parameters on the electromechanical damping may easily be de¬ on portions of the shaft, alternator d.c.-excitation current pick-up rived; a chart given in the report exhibits some important results. In the Rodenhuize case, the damping factors computed by taking device). Post-factum work related to both the theoretical and practical into account the common thermodynamical damping in each of the analysis of the electromagnetic torsional damping for different turbine sections and the air gap electromagnetic damping above circumstances (CF, companion paper Part II [1]) examines the bases defined, fully agree with those derived from the torque spectra given for the astonishing results given in this paper and carries on to in Part I. The importance of the electromagnetic damping is also pointed consider the necessary accuracy needed for the practically available or input parameter values (characteristics) for both generator and grid out by full scale tests performed on the alternator connected into,the to compute adequately all secondary variables treated in this paper. disconnected from, the grid: the damping is by far greater former than in the latter case. Reference Post-test numerical computations are used to verify the necessary [1] J. F. Goossens, A. J. Calvaer and L. J. Soenen, Full scale short- precision of the values of several machine parameters given by the circuit and other tests on the dynamic torsional response of manufacturers. Electrical parameters were acceptable, (exception was made for Rodenhuize NR 4-300 MW-3000 RPM turbogenerator. Part II. Test and postcomputed results.Electrodynamic damping the Xq reactance because of its influence on the machine internal angle, but this is a common fact) but mechanical parameters, mainly analysis.Elementary fatigue study. stiffnesses, were to be adjusted to meet the measured torsional eigenvalues. 81 WM 081-9 Reference September 1981, p. 4174 [1] J. F. Goossens, A. J. Calvaer and L J. Soenen, Full scale shortcircuit and other tests on the dynamic torsional response of Rodenhuize NR 4-300 MW-3000 RPM turbogenerator. Part I. on Test facilities.Comparisons between precalculated and measured results.Interpretation. 81 WM 057-9 September 1981, p. 4186

Full Scale Short-Circuit and Other Tests the Dynamic Torsional Response of Rodenhuize NR 4-300 MW-3000 RPM

Turbogenerator

Economic Operation of Distributed Power Systems Within an Electric Utility

Part II.Test and Postcomputed

Results.Electrodynamic Damping Analysis Elementary Fatigue Study

J. F. Goossens, Member, IEEE

Richard D. Tabors, Member, IEEE, Susan Finger, Student Member, IEEE, and Alan J. Cox Energy Laboratory, Massachusetts Institute of

Belgium

financial,

EBES, Antwerp, Belgium Technology A. J. Calvaer, Senior Member, IEEE Electrical Engineering Dept, University of Liège, This paper reports on the use of a series of linked economic, and engineering models that describe the operation of an electric utility. In addition, the models estimate the effect of small distributed energy sources that are stochastic in nature upon the utility's operations and financial structure. Fig. 1 is a schematic ofthe

L. J. Soenen

LABORELEC, St. Genesius Rode, Belgium

This paper is the continuation of the companion paper [1] "Part I" and reflects results of post-factum studies. Main topics presented in Part II are: .analysis of the behavior of a frequency modulated synchronous machine acting as damping source at the torsional

eigenvalues (frequencies) .comparison between computed quantities

and measured electrical

.attempt at estimation of the practical applicability of analytical

modeling system. The example energy source investigated in this paper is the direct conversion of solar energy to electricity, photovoltaics, distributed throughout the residential sector. Besides demonstrating the use of, and reporting results from, this set of models, the paper has another primary purpose: the description of a method for estimating rates for the buyback of surplus electricity from the photovoltaic resi¬ dences. While rates for sale to customers are estimated on the basis oftraditional regulatory practice, buyback rates are estimated on the basis of rules of promulgated under the Public Utility Regulatory Policy Act (PURPA).

PER SEPT

The electric utility is modeled in SYSGEN using a standard Customer MODELING SYSTEM probabilistic model. This model is derived from the deterministic Load Profile model in which generating units are ranked in order of increasing Dota costs and dispatched against the load duration curve. In the probabilistic model customer load and plant outages are inde¬ L Consumption pendent random variables. The distributed energy model, assuming ERATES a zero marginal operating cost, models these time-dependent plants SYSGEN PV User Model Utility by reducing the net hourly load, from which the load duration curve Rates SO LIPS Utility Costs Rate Setting is created. Production SO LOPS Model and The rate-setting model takes the fuel and operating costs Costing Mode! estimated by SYSGEN and supplements these costs with capital Insolation costs of the utility's generating and transmission equipment. These, combined with taxes and overhead costs, are used to generate two sets of rates. The first set of rates is based upon traditional regulatory practice, allowing a reasonable rate of return on the utility's Weather undepreciated capital stock. The second rate is based upon the Data utility's expansion costs, or marginal costs. Utility Pcnetratton Photovoltaic The worth of photovoltaics has two components. The first is the Load Analysis |*¿t-Impact on reduction of fuel costs to the utility. The second is the value of the Profile Load plants and equipment that the utility can do without and still maintain the same loss of load probability as a result of the model penetration. The results indicate that at increasing levels of 81 WM 148-6 penetration of photovoltaics the "effective capacity" of the September 1981, p. 4196 photovoltaic arrays goes down, as can be seen on Table 1. In addition, the value of the fuel displaced by photovoltaics also and Gas goes down. The paper presents estimated selling rates of electricity for the Its for Evaluation of four model utilities, based upon five different pricing criteria. We also estimate average values of (and, therefore, appropriate rates Internal Conditions in Gas for) surplus photovoltaic electricity. The average buyback value is estimated using two of the pricing criteria. Finally we present, for two utilities, a rate structure that is consistent with current practice for selling rates, but consistent with economic efficiency and PURPA Shotaro Tominaga, Member, IEEE, Hiroshi Kuwahara, Koichi regulations for buyback rates. The resulting buyback rate is higher Hirooka, and Takeo Yoshioka than the selling rate, due to the different pricing criteria and due to Mitsubishi Electric Corporation, Amagasaki, Japan the fact that no account is taken of additional costs that will result from buying back electricity. Introduction The application of gas filled switchgear, utilizing SFq gas as an

Analysis Technique SF6 Application SF6 Equipment

insulating or arc quenching medium, has been advanced for use as substation equipment in the world and air insulated equipment are gradually being replaced by gas insulated ones. Recently, a number of standards have been established on the gas analysis of SFg gas

Table 1

Photovoltaic

Nameplate Capacity

Region

Photovoltaic Effective

Capacity

1

Miami Miami Boston Boston Omaha Omaha Phoenix Phoenix

%of

%of

(MW)

system

(MW)

nameplate

200 1200 200 1200 200 1200 200 1200

3.1 18.3 3.1 18.3 2.6 18.5 2.6 15.9

59 185 71 304 19 74 80 407

29.5 23.8 35.5 25.3

9.5 6.2 40.0 33.9

equipment. Throughout the past 15 year record of manufacturing of SFg gas equipment, gas analysis has been made by the authors on a number of apparatus in operation as well as simulation tests of various conditions. The results showed that gas analysis is effective in the diagnosis of faults in SFß gas equipment. SFß Gas Analysis Methods The SFg gas analysis methods used were gas Chromatograph, hydrolyzable fluoride, acidity and mineral oil. The gas components detected by the gas Chromatograph were air (IVI2 + 0_), CF4, CO2, SOF2 and SO2. The gas sampling method and the relationship between compo¬ nents of SFß gas and their analysis methods are also described in this

section.

Examples of Gas Analysis on Simulation Tests of Internal Conditions It is very important to see what happens if any unusual situation occurs in these apparatus and if such can be detected by the gas analysis method. Fig. 1 shows the relationship between the vessel volume and the decomposed gas concentration when an arc is generated in the vessel. Fig. 2 shows the calculated example of decomposed gas con¬ centration at partial discharge in vessels of different capacity. De¬ composed gas was also detected in a simulation test of overheat of copper wire. It is evident that internal short circuit, partial discharge or overheat in the vessel can be detected by such highly sensitive mea¬ suring methods of decomposed gas as hydrolyzable fluoride or acidity. Evaluation of Conditions of SFg Gas Equipment Operated For a Long Time in the Field by Gas Analysis Fig. 3(a) to (f) show the relationship between service lives of gas

circuit breakers and the components of SFg gas taken from them. The circuit breakers subjected to gas analysis are still operated at present under normal conditions in electrical power companies and industrial

companies.

PER SEPT -31-