A method for diagnosing rotor turn-to-turn short circuit faults by installing detection coils on the rotor

Abstract

The present invention discloses an online diagnosis scheme for the inter-turn short circuit fault of the synchronous condenser rotor winding. In view of the characteristics that the excitation of the synchronous condenser is often adjusted, the present invention installs two groups of detection coils at both ends of the rotor, and diagnoses the fault according to the difference in the magnitudes of the currents induced on the coils when the excitation current is adjusted, effectively solving the problem of difficult online diagnosis of the inter-turn short circuit fault of the synchronous condenser rotor winding.

Description

Technical Field

[0001] The present invention relates to the field of motor fault diagnosis, and more particularly to an online diagnosis method for inter-turn short circuit faults of a synchronous condenser rotor winding. Background Art

[0002] The energy distribution in China determines that China needs to carry out the project of transmitting electricity from the west to the east. A large number of new synchronous condensers are put into use to maintain voltage balance in power transmission. The new synchronous condenser has good voltage regulation ability. However, since the excitation of the synchronous condenser needs to be frequently adjusted to change the reactive power provided to the power grid, the current impact caused by current changes and the huge centrifugal force caused by the high-speed rotation of the rotor will cause the rotor insulation layer of the synchronous condenser to be easily damaged. Slight damage to the insulation layer itself will not have too much impact on the operation of the synchronous condenser. However, as the motor continues to operate, the insulation layer at the damaged part will continue to deteriorate, eventually leading to extremely serious accidents such as shaft magnetization and rotor grounding.

[0003] At present, there is little research on the inter-turn short circuit fault of the synchronous condenser rotor winding. In actual situations, in most cases, it is necessary to perform fault diagnosis after the rotor winding of the synchronous condenser is taken offline. However, there is a special case of inter-turn short circuit of the rotor winding, where the short circuit does not occur during shutdown but occurs under the action of centrifugal force during operation. In this case, it is difficult to effectively distinguish faults with the current offline diagnosis scheme. Therefore, the research on the online fault diagnosis method for synchronous condensers is of great significance. Summary of the Invention

[0004] Aiming at the problems existing in the background art, the purpose of the present invention is to provide an online diagnosis method for inter-turn short circuit faults of a synchronous condenser rotor winding. The diagnosis method is as follows:

[0005] (1) Install detection coils on the large teeth on both sides of the rotor to detect the magnitude of the induced current generated during excitation regulation.

[0006] (2) Determine whether there is an inter-turn short circuit fault in the rotor winding according to the magnitude of the current difference between the two detection coils when the excitation current is adjusted.

[0007] The specific technical solution of the diagnosis method is as follows:

[0008] 1) Wind detection coils at the large teeth on both sides of the synchronous condenser rotor, and lead out the detection coils through slip rings, and record the magnitudes of their currents as i D0 and i D1 .

[0009] 2) Calculate the magnitude of the difference i D in the induced currents of the two detection coils, i D =(i D0 -i D1 ).

[0010] 3) First, when the synchronous condenser is operating normally and the excitation regulation rate is x A / s, record the current difference i D between the two detection coils as i0.

[0011] 4) Analyze the phenomena that will occur under the condition of inter-turn short circuit of the rotor winding:

[0012] According to the mutual inductance formula:

[0013]

[0014] where M 12 is the mutual inductance between the two coils, N1 and N2 are the number of turns of the two coils respectively, Λ is the magnetic conductance, μ is the magnetic permeability, S is the coil area, and l is the distance between the two coils.

[0015] The mutual inductance between the excitation and damping coils can be regarded as the sum of the mutual inductances of the windings in each individual slot and the damping winding. Then:

[0016]

[0017] where M field,D1 is the magnitude of the mutual inductance between the excitation and the detection coil D1; N, Λ, μ, S, and l represent the number of turns of the coil, magnetic conductance, magnetic permeability, coil area, and the distance between the coils respectively; λ is a constant coefficient between 0 and 1, representing the degree of inter-turn short circuit of the slot winding coil.

[0018] Since the distances from the faulty coil to both ends are different, it can be seen that the magnitudes of the mutual inductances of the excitation winding with the two detection coils after the fault are different. Therefore, when the excitation changes at this time, the induced current magnitudes generated in the two coils are different.

[0019] 5) When wanting to perform fault diagnosis on the synchronous condenser, monitor the regulation rate of the excitation current, denoted as y A / s, and the magnitude of the difference i D between the induced currents of the two detection coils.

[0020]

[0021] 7) If the value of i1 is greater than 1.1 * i0 (leaving a 10% threshold), it is considered that the synchronous condenser has an inter-turn short circuit fault in the rotor winding.

[0022] Beneficial effects:

[0023] By installing two groups of detection coils at both ends of the rotor, the present invention performs fault diagnosis according to the difference in the magnitudes of the currents induced on the coils when the excitation current is regulated. Aiming at the characteristic that the excitation of the synchronous condenser is often regulated, it can effectively solve the problem of difficult on-line fault diagnosis of the inter-turn short circuit of the rotor winding of the synchronous condenser. Description of the drawings

[0024] Figure 1 is a schematic diagram of the installation of the detection coil (top view);

[0025] Figure 2 is the diagnostic flowchart for the inter-turn short circuit fault of the rotor;

[0026] Figure 3 is the difference i between the induced currents of the two coils D . Specific implementation manners

[0027] The technical solution of the present invention will be described in detail below in combination with simulation cases:

[0028] As Figure 1 , 2 , as shown in Fig. 3, the rated capacity of the synchronous condenser simulation model is 300 Mvar, the rated stator voltage is 20 kV, the rated frequency is 50 Hz, the rated stator current is 8,660 A, the rated excitation voltage is 323 V, the rated excitation current is 2,381 A, the rotor has a total of 32 slots, and each slot has 12 turns of windings. Now, a 3-turn inter-turn short circuit fault occurs in a certain slot of the rotor, and the synchronous condenser is in the state of adjusting the magnitude of the excitation current from 0.5 s to 1 s. The following is the diagnosis of the fault:

[0029] 1) Wind the detection coils around the large teeth on both sides of the rotor of the synchronous condenser, lead out the detection coils through slip rings, and record the magnitudes of their currents as i D0 and i D1 .

[0030] 2) Calculate the magnitude of the difference i between the induced currents of the two detection coils D , i D =(i D0 -i D1 ).

[0031] 3) First, when the synchronous condenser is operating normally and the regulation rate of the excitation is x A / s, record the value of the current difference i between the two detection coils D as i0.

[0032] 4) Analyze the phenomena that will occur under the condition of the inter-turn short circuit of the rotor winding:

[0033] According to the mutual inductance formula:

[0034]

[0035] where M 12 is the mutual inductance between the two coils, N1 and N2 are the number of turns of the two coils respectively, Λ is the magnetic conductance, μ is the magnetic permeability, S is the area of the coil, and l is the distance between the two coils.

[0036] The mutual inductance between the exciting coil and the damping coil can be regarded as the sum of the mutual inductances between the windings in each individual slot and the damping winding. Then:

[0037]

[0038] Where M field,D1 is the magnitude of the mutual inductance between the exciting coil and the detection coil D1; N, Λ, μ, S, and l respectively represent the number of turns of the coil, magnetic conductance, magnetic permeability, coil area, and the distance between the coils; λ is a constant coefficient between 0 and 1, representing the degree of inter-turn short circuit of the coil turns in the slot winding.

[0039] Since the distances from the faulty coil to both ends are different, it can be seen that the magnitudes of the mutual inductances of the exciting winding with respect to the two detection coils are different after the fault. Therefore, when the excitation changes at this time, the magnitudes of the induced currents generated in the two coils are different.

[0040] 5) When fault diagnosis of the synchronous condenser is to be carried out, the rate of change of the exciting current during regulation is denoted as y A / s, and the magnitude of the difference i D between the induced currents in the two detection coils.

[0041] 6) Denote

[0042] 7) If the value of i1 is greater than 1.1 * i0 (leaving a threshold of 10%), it is considered that the synchronous condenser has a turn-to-turn short circuit fault in the rotor winding.

[0043] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0044] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. An online diagnosis method for inter-turn short circuit faults in the rotor winding of a synchronous condenser, characterized in that, The diagnostic method is as follows: (1) Detecting coils are installed on the large teeth on both sides of the rotor to detect the magnitude of the induced current generated during excitation regulation; (2) Judging whether there is a turn - to - turn short - circuit fault in the rotor winding according to the magnitude of the current difference between the two detecting coils when the excitation current is adjusted; The detailed steps of the diagnostic method are as follows: 1) Wind a detection coil around the large teeth on both sides of the synchronous condenser rotor, lead out the detection coil through the slip ring, and record the magnitudes of their currents as i D0 and i D1 ; 2) Calculate the magnitude of the difference i in the induced currents of the two side detection coils D where i D = (i D0 - i D1 ); 3) First, when the synchronous condenser is operating normally and the excitation regulation rate is x A / s, record the value of the current difference i D between the two detection coils as i0; 4) Analyze the phenomena that will occur under the condition of turn - to - turn short - circuit of the rotor winding: Based on the mutual - inductance formula: where M 12 is the mutual inductance of the two coils, N1 and N2 are the number of turns of the two coils respectively, Λ is the magnetic conductance, μ is the magnetic permeability, S is the coil area, and l is the distance between the two coils; 5) When it is desired to perform synchronous condenser fault diagnosis, the rate during the adjustment of the excitation current is monitored and denoted as y A / s, as well as the magnitude of the difference i D between the induced currents of the two detection coils; 6) Record 7) If the value of i1 is greater than 1.1 * i0, it is considered that a turn - to - turn short - circuit fault has occurred in the synchronous phase modifier rotor winding.

2. The on-line diagnosis method for the inter-turn short circuit fault of the rotor winding of a synchronous condenser according to claim 1, characterized in that The mutual inductance between the excitation and damping coils can be regarded as the sum of the mutual inductances of the windings in each individual slot and the damping winding. Then: where M field,D1 is the magnitude of the mutual inductance between the exciting and detecting coils D1; N, Λ, μ, S, and l represent the number of turns of the coil, magnetic conductance, magnetic permeability, coil area, and the distance between the coils, respectively; λ is a constant coefficient between 0 and 1, representing the degree of inter-turn short circuit of the slot-wound coil turns.

3. An on-line diagnosis method for inter-turn short circuit fault of the rotor winding of a synchronous condenser according to claim 1, characterized in that Since the distances from the coil to both ends are different, it can be seen that the mutual inductances of the excitation winding to the two detecting coils are different after the fault. Therefore, when the excitation changes, the magnitudes of the induced currents generated in the two coils are different.

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