Synchronous phase modifier rotor winding turn-to-turn short circuit fault diagnosis method

Abstract

The invention discloses a synchronous phase modifier rotor winding turn-to-turn short circuit fault diagnosis method, particularly relates to the technical field of electrical fault diagnosis, and solves the problems that in the prior art, a rotor winding turn-to-turn short circuit diagnosis method can be divided into online monitoring and offline monitoring, the offline monitoring cannot evaluate the real-time health state of a motor, and the fault diagnosis accuracy is poor. Many on-line detection methods belong to intrusive diagnosis and are easy to damage motor insulation, and a data-driven fault diagnosis method has the technical problems that data are difficult to obtain and an algorithm lacks universality. According to the technical scheme, a stator three-phase current signal and a stator three-phase voltage signal are obtained, and in the process of comparing instantaneous power before and after the turn-to-turn short-circuit fault of the rotor winding, the turn-to-turn short-circuit fault of the phase modifier rotor winding is diagnosed by using third and fifth harmonic amplitudes of the instantaneous power; the synchronous phase modifier rotor turn-to-turn short circuit fault diagnosis method does not need to additionally install a sensor or additionally modify the phase modifier, and realizes synchronous phase modifier rotor turn-to-turn short circuit fault diagnosis.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical fault diagnosis, and in particular to a method for diagnosing a synchronous phase condenser rotor winding inter-turn short circuit fault. Background Art

[0002] In order to adapt to the development of the current era and meet the needs of "large DC transmission and strong reactive power support", researchers have optimized the parameters of the old phase condensers and designed and developed a batch of new synchronous phase condensers. Compared with traditional synchronous phase condensers, the new synchronous phase condensers are less affected by the system and have strong excitation capabilities. When the voltage of the power grid changes greatly, the strong excitation capability can achieve rapid voltage recovery. The new synchronous phase condensers have gradually become the preferred reactive power compensation equipment for large power grids with their fast tracking of reactive power and voltage capabilities, low reactive power compensation equipment failure rate, and large reactive power compensation range.

[0003] Although water cooling is effective in reducing the temperature rise of the phase condenser, motor failures caused by water blockage or water outage account for more than half of the total motor failures. Therefore, the temperature rise caused by the blockage of the phase condenser is likely to cause local overheating of the phase condenser, which in turn affects the safe and stable operation of the phase condenser body. In severe cases, it will burn the internal insulation and cause the rotor winding inter-turn short circuit fault, threatening the normal operation of the phase condenser. The existing rotor winding inter-turn short circuit diagnosis methods can be divided into online monitoring and offline monitoring. Offline monitoring cannot evaluate the real-time health status of the motor. Many online detection methods are invasive diagnosis and are easy to damage the motor insulation. Data-driven fault diagnosis methods have problems such as difficulty in obtaining data and lack of universality of algorithms. Therefore, exploring more rotor winding inter-turn short circuit fault diagnosis methods is of great significance to ensure the safe and stable operation of synchronous phase condensers. Summary of the invention

[0004] Therefore, the present invention solves the problem that the rotor winding inter-turn short-circuit diagnosis method in the prior art can be divided into two types: online monitoring and offline monitoring. Offline monitoring cannot evaluate the real-time health status of the motor, and many online detection methods are invasive diagnosis, which are easy to damage the insulation of the motor. The data-driven fault diagnosis method has the technical problems of difficulty in obtaining data and lack of universality of the algorithm. A synchronous phase regulator rotor winding inter-turn short-circuit fault diagnosis method provided by the present invention takes into account the inherent odd harmonic components in the stator three-phase current in the process of comparing the instantaneous power before and after the rotor winding inter-turn short-circuit fault, thereby improving the accuracy of the diagnosis method.

[0005] The present invention provides a method for diagnosing a short-circuit fault in a synchronous phase condenser rotor winding, comprising the following steps: In order to achieve the purpose of the present invention, a method for diagnosing a short-circuit fault in a synchronous phase condenser rotor winding is proposed, comprising the following steps:

[0006] Step 1: Get the instantaneous values ​​of the three-phase voltages of the phase regulator stator, which are U A (t), U B (t) and U C (t);

[0007] Step 2: Get the instantaneous values ​​of the three-phase currents of the phase regulator stator, which are I A (t), I B (t) and I C (t);

[0008] Step 3: Obtain the instantaneous power P(t) of the synchronous condenser based on the instantaneous values ​​of the three-phase voltage and the three-phase current, P(t) = P A (t)+P B (t)+P C (t) = U A (t)*I A (t)+U B (t)*I B (t)+U C (t)*I C (t);

[0009] Step 4: Perform spectrum analysis on the instantaneous power P(t);

[0010] Step 5: Set the fault threshold. When the amplitudes of the third and fifth harmonics in the instantaneous power are both greater than the threshold, it is diagnosed as a rotor winding turn-to-turn short circuit fault.

[0011] Further, step 1 includes: the stator winding of the phase regulator is connected to the grid, the stator three-phase voltage is equal to the grid voltage, the frequency is 50 Hz, and the stator three-phase voltage can be expressed as:

[0012]

[0013] Where U AN , U BN and U CN are the effective values ​​of the three-phase voltages A, B, and C. UA, UB, and UC are the three-phase voltages of the stator, ω is the grid frequency, and t is the time;

[0014] Furthermore, step 2 includes: when the phase regulator is operating normally, the stator three-phase current includes not only the fundamental wave with a frequency of 50 Hz, but also odd harmonics. The stator three-phase current can be expressed as:

[0015]

[0016] In the formula, I (2k-1)Amf ,I (2k-1)Bmf and I (2k-1)Cmf are the amplitudes of the harmonics of the three-phase currents A, B, and C, respectively. is the phase angle of current lagging behind voltage.

[0017] Furthermore, when the phase regulator is operating normally, the spectrum analysis of the instantaneous power includes not only the constant quantity but also the even-order harmonic components, among which the constant quantity accounts for a large proportion and the even-order harmonic components account for a small proportion. The instantaneous power of each phase of the stator during normal operation can be expressed as:

[0018]

[0019] Furthermore, step 4 includes: when the phase regulator has a short-circuit fault in the rotor winding, in addition to the original constant and even-order harmonic components, the spectrum analysis of the instantaneous power also shows the third and fifth odd-order harmonics, and the amplitude of the odd-order harmonics gradually increases as the severity of the fault increases. The instantaneous power of each phase of the stator after the short-circuit fault in the rotor winding can be expressed as:

[0020]

[0021] Further, step 5 includes: setting the instantaneous power third harmonic amplitude P after the rotor winding interturn short circuit fault 3th The fault threshold is δ1, and the 5th harmonic amplitude is P 5th The fault threshold is δ2, when P 3th >δ1 and P 5th When >δ2, it is diagnosed as a rotor winding turn-to-turn short circuit fault.

[0022] In the above technical solution, the technical effects and advantages provided by the present invention are:

[0023] 1. The present invention provides a method for diagnosing short-circuit faults between turns of a synchronous phase condenser rotor winding. When used on site, only the stator three-phase current signal and the stator three-phase voltage signal need to be obtained. The inherent sensors of the phase condenser itself can obtain the required signals. Therefore, this method does not require the installation of additional sensors or additional modifications to the phase condenser.

[0024] 2. The present invention provides a synchronous phase condenser rotor winding inter-turn short-circuit fault diagnosis method. In the process of comparing the instantaneous power before and after the rotor winding inter-turn short-circuit fault, the inherent odd-order harmonic components in the stator three-phase current are taken into account, thereby improving the accuracy of the diagnosis method.

[0025] 3. The present invention provides a method for diagnosing a synchronous phase condenser rotor winding inter-turn short-circuit fault, obtains a stator three-phase current signal and a stator three-phase voltage signal, and in the process of comparing the instantaneous power before and after the rotor winding inter-turn short-circuit fault, takes into account the inherent odd-order harmonic components in the stator three-phase current, and proposes to use the third and fifth harmonic amplitudes of the instantaneous power to diagnose the phase condenser rotor winding inter-turn short-circuit fault. There is no need to install additional sensors or perform additional modifications to the phase condenser, and non-invasive online monitoring and diagnosis of synchronous phase condenser rotor winding inter-turn short-circuit faults can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0027] Figure 1 It is a flow chart of a method for diagnosing a short-circuit fault between turns of a synchronous condenser rotor winding provided by the present invention;

[0028] Figure 2 This is a simulation model diagram of the synchronous condenser body;

[0029] Figure 3 It is a schematic diagram of external circuit simulation of a short-circuit fault of a synchronous condenser rotor winding according to the present invention; DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0031] In this embodiment, the TTS-300-2 type phase tunner is selected as the object to establish the phase tunner simulation model. Figure 2 The simulation parameters are shown in Table 1. Figure 3As shown, according to the finite element fault simulation model, assuming that the excitation source is a constant voltage source, the excitation current is adjusted according to the short-circuited turn resistance, the short-circuited turn is set to Wingdingfault, and the other normal turn windings are set to Wingdingright. The resistances Rexciting, Rfault and r are the excitation resistance after the rotor winding turns are short-circuited, the excitation resistance of the short-circuited part and the short-circuit transition resistance, respectively. Wa1, Wa2, Wb1, Wb2, Wc1, and Wc2 represent the first branch of phase A and the second branch winding of phase A, the first branch of phase B and the second branch winding of phase B, and the first branch of phase C and the second branch winding of phase C, respectively. Ra1, Ra2, Rb1, Rb2, Rc1, and Rc2 represent the resistance of the corresponding branches, respectively. In order to make the motor reach the phase-converter operating state, the A, B, and C three-phase windings in the external circuit should be connected to a three-phase symmetrical power supply to simulate the grid-connected operation of the phase-converter. Changing Wingdingright and Wingdingfault can control the number of turns of the short-circuit winding, thereby changing the severity of the short-circuit fault. Since Rfault is the resistance corresponding to Wingdingfault, Rfault needs to be changed accordingly when changing the number of turns.

[0032] Table 1: TTS-300-2 Synchronous Condenser Parameters

[0033]

[0034] Table 2 shows the amplitude of each harmonic of the instantaneous power of the branch under different short-circuit turns. It can be seen from Table 2 that after the rotor winding inter-turn short circuit occurs, the 3rd and 5th harmonics in the instantaneous power jump sharply, and increase with the severity of the fault. In engineering applications, the thresholds δ1 and δ2 can be set according to the actual parameters and working requirements of the phase regulator. Assuming that δ1=5 and δ2=0.05 when P 3th >5 and P 5th When it is greater than 0.05, it is diagnosed as a rotor winding turn-to-turn short circuit fault.

[0035] Table 2: Table of harmonic amplitudes of branch instantaneous power under different short-circuit turns

[0036]

[0037] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for diagnosing short-circuit faults in rotor windings of synchronous condenser, characterized in that: The steps include: S1: Get the instantaneous values ​​of the three-phase voltage of the phase regulator stator, which are U A (t), U B (t) and U C (t); S2: Get the instantaneous values ​​of the three-phase current of the phase regulator stator, which are I A (t), I B (t) and I C (t); S3: Obtain the instantaneous power P(t) of the synchronous condenser based on the instantaneous values ​​of the three-phase voltage and the three-phase current, P(t) = P A (t)+P B (t)+P C (t) = U A (t)*I A (t)+U B (t)*I B (t)+U C (t)*I C (t); S4: Perform spectrum analysis on instantaneous power P(t); S5: Set the fault threshold and compare the harmonic amplitude in the instantaneous power with the threshold to determine whether there is a short circuit fault between the rotor winding turns.

2. The synchronous phase condenser rotor winding turn-to-turn short circuit fault diagnosis method according to claim 1, characterized in that: In the step S5, when the amplitudes of the third and fifth harmonics in the instantaneous power are both greater than the threshold, it is diagnosed as a rotor winding turn-to-turn short circuit fault.

3. The synchronous phase condenser rotor winding turn-to-turn short circuit fault diagnosis method according to claim 1, characterized in that: In step S1, the phase regulator stator winding is connected to the grid, the stator three-phase voltage is equal to the grid voltage, the frequency is 50 Hz, and the stator three-phase voltage can be expressed as: Where U AN , U BN and U CN They are the effective values ​​of the three-phase voltages A, B, and C respectively.

4. The synchronous phase condenser rotor winding turn-to-turn short circuit fault diagnosis method according to claim 1, characterized in that: When the phase regulator in step S2 operates normally, the stator three-phase current includes not only the fundamental wave with a frequency of 50 Hz, but also odd harmonics. The stator three-phase current is expressed as: In the formula, I (2k-1)Amf ,I (2k-1)Bmf and I (2k-1)Cmf are the amplitudes of the harmonics of the three-phase currents A, B, and C, respectively. is the phase angle of current lagging behind voltage.

5. The synchronous phase condenser rotor winding turn-to-turn short circuit fault diagnosis method according to claim 1, characterized in that: When the phase regulator in step S4 is operating normally, the spectrum analysis of the instantaneous power includes not only constants but also even-order harmonic components. The instantaneous power of each phase of the stator during normal operation can be expressed as:

6. The synchronous phase condenser rotor winding turn-to-turn short circuit fault diagnosis method according to claim 2, characterized in that: In the step S4, when the phase regulator has a short-circuit fault in the rotor winding, in addition to the original constant and even-order harmonic components, the spectrum analysis of the instantaneous power also shows the third and fifth odd-order harmonics. The instantaneous power of each phase of the stator after the short-circuit fault in the rotor winding can be expressed as:

7. The synchronous phase condenser rotor winding inter-turn short circuit fault diagnosis method according to claim 6, characterized in that: In step S5, the instantaneous power third harmonic amplitude P after the rotor winding interturn short circuit fault is set 3th The fault threshold is δ1, and the 5th harmonic amplitude is P 5th The fault threshold is δ2, when P 3th >δ1 and P 5th When >δ2, it is diagnosed as a rotor winding turn-to-turn short circuit fault.

8. The synchronous phase condenser rotor winding turn-to-turn short circuit fault diagnosis method according to claim 6, characterized in that: In step S4, as the severity of the fault increases, the amplitude of the odd-order harmonics gradually increases.

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