del sistema de turbina-generador instalado. Producción. Nuestro centro de producción (Orléans, Francia) está equipado con máquinas de tecnología punta. Los generadores síncronos constituyen el equipo más costoso en un sistema de potencia. Como consecuencia de los posibles fallos que se presentan tanto. CONTROL DE FRECUENCIA EN GENERADORES SÍNCRONOS Carol Sánchez Mateo Rodríguez Fredy Salazar Luz Dary Garcia Universidad.

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The magnitude of the third harmonic voltage at the neutral connection becomes maximum while in terminals it decreases to zero, as it is presented in figure 3 [4, 8].

Although a first fault normally does not cause any problem, this have to be removed before the occurrence of a second ground fault which could cause severe machine damages and the consequent outage. However, by using the proposed alarm-trip logic, remarkable improvements could be obtained in the case of detecting high impedance ground faults.

As is mentioned before, the third harmonic voltage appears as zero-sequence quantities. Considering a ground fault at the neutral connection, the third harmonic at this node decreases to zero. This method is based on the comparison of third harmonic voltages using several mathematic relations which should make the protective device more susceptible to the variation of these voltages.

### Sistema de potencia con 4 generadores sincronos. – File Exchange – MATLAB Central

This circuit was solved according to the Millman theorem properties, and it is graphically presented in figure 11 [13]. Improvement of the third harmonic based stator ground fault protection for high resistance grounded snicronos generators. Figure 3 Magnitude of the third harmonic at the stator winding considering a ground fault in terminals.

According to preliminary test performed in the proposed real synchronous generator, the obtained values for the maximum fault resistances which are detectable by using each one of the three proposed schemes are presented in table 2. These variations are particular for each one of the generator machines and are due small imperfections in the winding distribution during the soncronos process, which cause small voltage unbalances [9].

The high impedance method is frequently used because in the case of faults the current magnitude is relatively low [1, 2]. Figure 1 Magnitude of the third harmonic at the stator winding considering non fault situations Considering a ground fault at the neutral connection, the third harmonic at this node decreases to zero.

Theoretical evaluation of the non-faulted and faulted models. Grid-side converter control of DFIG wind turbines to enhance sinronos quality of distribution network. Methodology Method of third harmonic This method uses a comparison of the third order component of the voltage measured at the synchronous generator terminal Vt or at the neutral Vn connections.

This scheme is based on the measurement of the third harmonic component of voltage at the neutral connection of the synchronous generator, as presented in figure 4. From the proposed equivalent, voltages at the neutral Vn and terminal Vt under fault conditions are obtained as it is presented in 14 and Figure 4 Protective scheme used sijcronos detect under voltage of the third sjncronos Figure generadoree Protective scheme using over voltage of the third harmonic Ratio of the third harmonic components Scheme 3 This method is based on the comparison of wincronos harmonic voltages using several mathematic relations which should make the protective device more susceptible to the variation of these voltages.

Method and system for rapid modeling and verification of excitation systems for synchronous generators. Conference Publication N o.

Finally, the use of the ratio scheme shows an interesting behavior making possible the detection of high impedance faults. All the contents of this journal, except where otherwise noted, sincroons licensed under a Creative Commons Attribution License.

The behavior of the third harmonic voltage is described by curves as shown in figure 14 [7, 10]. A stator ground fault close to the neutral point is not immediately catastrophic because: English pdf Article in xml format Article references How to cite this article Automatic translation Send this article by e-mail. Table 2 Maximum fault resistance values detectable by the analyzed protective methods using the voltage thresholds Undervoltage, overvoltage and ratio of the third harmonic of voltage Fault resistance estimation using the alarmtrip logic As proposed improvement of the protection method, the alarm-trip logic previously explained is considered to determine the maximum values of fault resistance which could be detected in the case of ground faults.

This corresponds to a proposed improvement of the classical voltage threshold alternatives. Figure 5 Protective scheme using over voltage of the third harmonic.

The first strategy is based on the determination of the normal values of the third harmonic of voltage at the terminals and the neutral of the synchronous generator. Overvoltage of the third harmonic component Scheme 2. The current magnitude depends of the grounding type high, medium and low impedance. Additionally, E 3n corresponds to kE 3 and E 3t is associated to 1-k E 3where both are the third harmonic voltages produced by the stator winding between the generator neutral and the ground-fault location k, and between the generator terminal and the ground fault location krespectively.

Schemes 2 and 3 Overvoltage and ratio of the third harmonic components, respectively have a better performance according to the analyzed cases, because the capability to detect high fault resistances is higher than in the case of scheme 1. The results help to validate the system behavior by a comparison of the values obtained for the third harmonic voltage measured at the ground connection Vn and these measured at the machine terminals Vt with those obtained by using equations 6714 and 15 considering the real machine parameters given by table 1.

Smooth transition from wind only to wind diesel mode in an autonomous wind diesel system with a battery-based energy storage system. Similarly, the admittances Y 1 and Y 2 have the same meaning. Where i indicates the imaginary operator and f is the power frequency. These three different methods are based in voltage measurements at the neutral and terminal connections, and also in the ratio of these measurements.

Figure 6 Protective scheme of third harmonic voltage using the ratio method. Figure 14 Third harmonic voltage typical variations caused by changes in the output active power. Figure 12 Equivalent circuit used to find Vt and Vn.

## Electric Machinery Company – Generadores Sincrónicos

Table 1 Typical values for a unit-connected generator. In this method, the third harmonic voltage is measured at the neutral. Poland Developments in Power System Protection. This relay detects variations at the magnitude of the third harmonic causing alarm or trip. Lund Institute of Technology. In the case of the overvoltage sihcronos the third harmonic scheme 2there is not possible to detect any ground fault because the overlapping of the normal operation range values of the third harmonic and those values measured in case of faults.

Figure 8 Zero-sequence circuit Figure 9 Simplified zero-sequence circuit Solving circuit proposed in figure 9 sincrobos, equations 6 and 7 are then obtained for the voltage at the neutral and terminals, respectively.

The obtained results shows small variations in the maximum fault resistance detected, showing the reduced dependence of the proposed protection strategy and the synchronous generator load condition. According to the results, it is shown that the scheme 1 Undervoltage of the third harmonic component has a lower capability to detect the abnormal behavior in case of high resistant faults.

In figure 6 the ratio scheme is presented [7, 11, 12].

The logic used to determine the presence of trip or alarm for both, under and overvoltage of the third harmonic component schemes 1 and 2, respectivelyis presented in figure 13, and it is based on the comparison of the values of the third harmonic of the voltage measured denoted with the additional subindex m and those normal values as the present in figure Figure 1 Magnitude of the third harmonic at the stator winding considering non fault situations.