Grounding location method for single-point grounding fault of generator rotor

Abstract

The present invention discloses a grounding positioning method for a single-point grounding fault of a generator rotor, which is used for positioning a fault grounding point when an insulation fault occurs. The generator rotor is connected to an exciter rotor wheel to connect the generator rotor winding and the exciter winding into a conduction loop, including: the generator rotor is in a stationary state, the negative pole of the conduction loop is grounded, and the resistance value between the positive and negative poles of the conduction loop is detected to obtain a first resistance value; the positive pole of the conduction loop is grounded, and the resistance value between the positive and negative poles of the conduction loop is detected to obtain a second resistance value; the first resistance value, the second resistance value and the DC resistance of the rotor winding are compared respectively, and the position of the fault grounding point is determined according to the comparison result. Compared with the prior art, the present invention can be positioned without disassembling the generator rotor and the exciter rotor, and the positioning is simple and fast.

Description

Technical Field

[0001] The present invention relates to the field of generators, and in particular to ground fault location of a generator rotor. Background Art

[0002] The brushless exciter consists of a permanent magnet rotor, permanent magnet stator, main exciter stator, main exciter rotor, rectifier, fan, pedestal bearing, chassis, baseplate, ground detection device, diffuser, housing end plates, and housing. The exciter operates as follows: the three-phase AC power generated by the permanent magnet is rectified by an AVR and then used to excite the main exciter stator. The main exciter rotor cuts through the magnetic field, generating AC power that is converted to DC through a three-phase full-bridge rectifier and then used to excite the generator rotor. The ground detection device performs insulation measurement: the brush lift control unit energizes the brush lift relay, supplying an external 220V DC power supply to the brush lift electromagnet, lifting the carbon brushes. Two seconds after the insulation resistance measurement begins, the 120V power supply relay switches the DC power supply to positive and negative polarity to perform a self-test. If the self-test passes, the DC power supply, along with the 1.2MΩ internal resistance and the insulation resistance, forms a circuit, generating leakage current. The sampling resistor feeds the leakage current value back to the control circuit board, which then calculates the insulation resistance value.

[0003] When assembling the half-speed steam turbine generator, the generator rotor is connected to the exciter rotor, and the generator rotor winding and the exciter winding are connected to form an integral circuit. The electrical diagram is as follows: Figure 1 As shown, a rectifier assembly is connected to each phase field winding, each with several parallel branches. Dashed lines M1 and M2 represent the exciter shaft. Normal removal of the generator wheel and conductive rod bolts and installation of the exciter journal bracket require at least 15 hours. Reinstallation after removal requires a shaft swing test of the exciter, and the wheel connection requires at least 24 hours.

[0004] In a half-speed steam turbine generator, after the generator and exciter rotors are connected, a brush-lifting device can be used to measure the insulation of the generator, commutator, and main exciter rotors. However, due to limitations in the measurement principle, rotor insulation is measured simultaneously with both the generator and exciter rotors. When a low insulation fault is detected, the device cannot distinguish which part has the insulation problem and cannot locate the fault. This requires disassembling the generator and exciter rotors to locate the fault separately, which is extremely time-consuming and labor-intensive.

[0005] Therefore, there is an urgent need for a grounding location method for a single-point grounding fault of a generator rotor that can solve the above-mentioned problem. Summary of the Invention

[0006] The object of the present invention is to provide a grounding location method for a single-point grounding fault of a generator rotor, which can locate the grounding fault position without disassembling the generator rotor and the exciter rotor.

[0007] To achieve the above-mentioned objectives, the present invention discloses a grounding location method for a single-point grounding fault on a generator rotor, which is used to locate the faulty grounding point when an insulation fault occurs. The generator rotor is connected to an exciter rotor wheel pair so that the generator rotor winding and the exciter winding are connected to form a conductive loop, comprising: the generator rotor is in a stationary state; the negative pole of the conductive loop is grounded and the positive pole is not grounded, and the resistance value between the positive and negative poles of the conductive loop is detected to obtain a first resistance value; the positive pole of the conductive loop is grounded and the negative pole is not grounded, and the resistance value between the positive and negative poles of the conductive loop is detected to obtain a second resistance value; the first resistance value, the second resistance value and the DC resistance of the rotor winding are compared respectively, and the position of the faulty grounding point is determined based on the comparison results.

[0008] Compared with the existing technology, the present invention utilizes the unidirectional conduction performance of the diode connected in series on the exciter coil to force the positive and negative poles of the conduction loop to be grounded respectively, and then measures the resistance value between the positive and negative poles. The location of the grounding fault point is determined based on the size of the resistance value. There is no need to disassemble the generator rotor and the exciter rotor, and positioning is simple and fast.

[0009] Preferably, the "determining the position of the fault grounding point based on the comparison result" specifically includes: judging that the fault grounding point is inside the rotor winding when the first resistance value is less than the DC resistance of the rotor winding and the second resistance value is less than the DC resistance of the rotor winding; judging that the fault grounding point is at the positive pole when the first resistance value is less than the DC resistance of the rotor winding and the second resistance value is equal to the DC resistance of the rotor winding; judging that the fault grounding point is at the negative pole when the first resistance value is equal to the DC resistance of the rotor winding and the second resistance value is less than the DC resistance of the rotor winding; and judging that the fault grounding point is inside the excitation winding when the first resistance value is equal to the DC resistance of the rotor winding and the second resistance value is equal to the DC resistance of the rotor winding.

[0010] Preferably, the "determining the position of the fault grounding point based on the comparison result" also includes: determining whether the insulation resistance value of the rotor is 0 during the insulation fault. If the insulation resistance value of the rotor is not 0 during the insulation fault, the "determining the position of the fault grounding point based on the comparison result" specifically includes: determining that the fault grounding point is inside the rotor winding when the first resistance value is less than the DC resistance of the rotor winding and the second resistance value is less than the DC resistance of the rotor winding; determining that the fault grounding point is at the positive pole when the first resistance value is less than the DC resistance of the rotor winding and the second resistance value is equal to the DC resistance of the rotor winding; determining that the fault grounding point is at the negative pole when the first resistance value is equal to the DC resistance of the rotor winding and the second resistance value is less than the DC resistance of the rotor winding; and determining that the fault grounding point is inside the excitation winding when the first resistance value is equal to the DC resistance of the rotor winding and the second resistance value is equal to the DC resistance of the rotor winding. If the insulation resistance value of the rotor is 0 during an insulation fault, the "determining the position of the fault grounding point based on the comparison result" specifically includes: when one of the first resistance value and the second resistance value is 0 and the other is equal to the DC resistance of the rotor winding, determining that the fault grounding point is at the positive or negative pole; when both the first resistance value and the second resistance value are less than the DC resistance of the rotor winding and the sum of the first resistance value and the second resistance value is equal to the DC resistance of the rotor winding, determining that the fault grounding point is inside the rotor coil; and when both the first resistance value and the second resistance value are equal to the DC resistance of the rotor winding, determining that the fault grounding point is inside the excitation winding.

[0011] Specifically, if the insulation resistance value of the rotor is 0 during an insulation fault, when the first resistance value R1 is 0 and the second resistance value R2 is equal to the rotor winding DC resistance R0, it is judged that the fault grounding point is at the positive pole; when the second resistance value R2 is 0 and the first resistance value R1 is equal to the rotor winding DC resistance R0, it is judged that the fault grounding point is at the negative pole.

[0012] Preferably, the "determining the position of the fault grounding point based on the comparison result" specifically includes: when the first resistance value is less than the DC resistance of the rotor winding, judging that the fault grounding point is inside the rotor winding or the positive pole; when the first resistance value is equal to the DC resistance of the rotor winding, judging that the fault grounding point is at the negative pole or inside the excitation winding; when the second resistance value is less than the DC resistance of the rotor winding, judging that the fault grounding point is at the negative pole or inside the rotor winding; when the second resistance value is equal to the DC resistance of the rotor winding, judging that the fault grounding point is at the positive pole or inside the excitation winding.

[0013] Preferably, the first resistance value and the second resistance value are measured by a double-arm bridge circuit. Of course, the resistance value can also be measured by other resistance measurement circuits.

[0014] Specifically, the measuring ends of the double-arm bridge circuit are connected to the positive electrode and the negative electrode of the exciter conductive rod respectively to detect the first resistance value and the second resistance value.

[0015] Preferably, the positive electrode and the negative electrode respectively include the exciter rectifier wheel, the exciter conductive rod, the rotor wheel pair, and the portion between the rotor lead and the rotor coil.

[0016] Preferably, the generator is a generator excited by rotating rectification.

[0017] Preferably, the grounding location method for the single-point grounding fault of the generator rotor is to locate the fault grounding point when the insulation resistance value of the rotor is less than 10 ohms during the insulation fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the conducting circuit formed after the generator rotor and the exciter rotor are aligned.

[0019] Figure 2 Schematic diagram of the negative grounding of the conductive loop of the present invention.

[0020] Figure 3 Schematic diagram of the positive grounding of the conductive loop of the present invention.

[0021] Figure 4 The present invention is a flow chart of a method for locating a single-point grounding fault in a generator rotor. DETAILED DESCRIPTION

[0022] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the embodiments and the accompanying drawings.

[0023] refer to Figures 2 to 4 The present invention discloses a method for locating a single-point ground fault on a generator rotor. This method is used to locate the faulty ground point in the event of an insulation fault in a half-speed steam turbine generator. The generator rotor 10 and the exciter rotor 20 are coupled in pairs, connecting the generator rotor winding L1 and the exciter windings A, B, and C to form a conductive loop 100. The dashed line M1M2 represents the exciter shaft. This conductive loop 100 includes a rectifier assembly 30 connected to each phase excitation winding A, B, and C. Each phase rectifier assembly 30 includes several parallel branches, each of which includes a unidirectionally conducting diode. A fuse S1 is also connected in series with each parallel branch. The dashed line M1M2 represents the main exciter shaft. Of course, the present invention can also be used in other generators that utilize rotating rectifier excitation.

[0024] refer to Figure 4 The method for locating a single-point grounding fault of a generator rotor comprises: the generator rotor is in a stationary state, (11) the negative pole of the conducting loop 100 is grounded and the positive pole is not grounded (e.g. Figure 2As shown), (13) detecting the resistance value between the positive electrode and the negative electrode of the conductive loop 100 to obtain a first resistance value R1. Figure 3 , (12) grounding the positive electrode of the conducting loop 100 and leaving the negative electrode ungrounded (e.g. Figure 3 As shown). (14) Detect the resistance value between the positive and negative poles of the conductive loop 100 to obtain a second resistance value R2. (15) Compare the first resistance value R1 with the DC resistance R0 of the rotor winding to obtain a comparison result; compare the second resistance value R2 with the DC resistance R0 of the rotor winding to obtain a comparison result. (16) Determine the position of the fault grounding point based on the above comparison result. Among them, the DC resistance R0 of the rotor winding is the resistance value between the positive and negative poles of the conductive loop 100 formed by the engine rotor winding and the main exciter rotor winding measured when no insulation fault occurs, that is, the DC resistance of the engine rotor winding and the main exciter rotor winding.

[0025] The positive pole and the negative pole respectively include the exciter rectifier wheel, the exciter conductive rod, the rotor wheel pair, and the area between the rotor lead and the rotor coil.

[0026] In this embodiment, the first resistance value R1 and the second resistance value R2 are measured using a dual-arm bridge circuit. The measuring ends of the dual-arm bridge circuit are connected to the positive and negative electrodes of the exciter conductive rod, respectively, to detect the first resistance value R1 and the second resistance value R2. Of course, other resistance measurement circuits, other than this embodiment, may also be used to measure resistance values.

[0027] The present invention is used to locate a fault grounding point when the rotor insulation resistance value is less than 10 ohms during an insulation fault. This insulation resistance value is obtained by measuring the insulation of the main exciter rotor using a brush lift or other detection device after the generator rotor and exciter rotor are connected. The method of measuring the insulation of the main exciter rotor after the rotor is connected is well known to those skilled in the art and will not be described in detail here.

[0028] Wherein, step (16) specifically includes: when the first resistance value R1 is less than the rotor winding DC resistance R0, judging that the fault grounding point is inside the rotor winding or the positive pole. When the first resistance value R1 is equal to the rotor winding DC resistance R0, judging that the fault grounding point is at the negative pole or inside the excitation winding. When the second resistance value R2 is less than the rotor winding DC resistance R0, judging that the fault grounding point is at the negative pole or inside the rotor winding. When the second resistance value R2 is equal to the rotor winding DC resistance R0, judging that the fault grounding point is at the positive pole or inside the excitation winding. Specifically, in this embodiment, after step (13), the following steps are performed: (15) comparing the first resistance value R1 with the rotor winding DC resistance R0 to obtain a comparison result, (16) obtaining a corresponding judgment conclusion of the fault grounding point based on the comparison result. After step (14), step (15) is performed: comparing the second resistance value R2 with the rotor winding DC resistance R0 to obtain a comparison result, (16) obtaining a corresponding judgment conclusion of the fault grounding point based on the comparison result. After step (16), the method further includes the step of obtaining a final judgment conclusion based on the two judgment conclusions.

[0029] Preferably, in another embodiment, before step 16, the method further includes the step of determining whether the insulation fault is a dead ground, that is, whether the insulation resistance value of the rotor is 0.

[0030] Wherein, if the insulation resistance value of the rotor is not 0 during the insulation fault, and the insulation resistance value is greater than the rotor winding DC resistance R0 or less than the rotor winding DC resistance R0 or equal to the rotor winding DC resistance R0, then in step (16): when the first resistance value R1 is less than the rotor winding DC resistance R0 and the second resistance value R2 is less than the rotor winding DC resistance R0, it is judged that the fault grounding point is inside the rotor winding. When the first resistance value R1 is less than the rotor winding DC resistance R0 and the second resistance value R2 is equal to the rotor winding DC resistance R0, it is judged that the fault grounding point is at the positive pole. When the first resistance value R1 is equal to the rotor winding DC resistance R0 and the second resistance value R2 is less than the rotor winding DC resistance R0, it is judged that the fault grounding point is at the negative pole. When the first resistance value R1 and the second resistance value R2 are both equal to the rotor winding DC resistance R0, it is judged that the fault grounding point is inside the excitation winding.

[0031] If the insulation resistance value of the rotor is 0 during an insulation fault and a dead ground occurs, then in step (16): when one of the first resistance value R1 and the second resistance value R2 is 0 and the other is equal to the rotor winding DC resistance R0, the fault grounding point is determined to be at the positive or negative pole. When both the first resistance value R1 and the second resistance value R2 are less than the rotor winding DC resistance R0 and the sum of the first resistance value R1 and the second resistance value R2 is equal to the rotor winding DC resistance R0, the fault grounding point is determined to be inside the rotor coil. When both the first resistance value R1 and the second resistance value R2 are equal to the rotor winding DC resistance R0, the fault grounding point is determined to be inside the excitation winding. Wherein, when the first resistance value R1 is 0 and the second resistance value R2 is equal to the rotor winding DC resistance R0, the fault grounding point is determined to be at the positive pole, and when the second resistance value R2 is 0 and the first resistance value R1 is equal to the rotor winding DC resistance R0, the fault grounding point is determined to be at the negative pole.

[0032] The above disclosure is only the preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention are still within the scope of the present invention.

Claims

1. A grounding location method for a single-point grounding fault of a generator rotor, used for locating the fault grounding point when an insulation fault occurs, wherein the generator rotor is connected to an exciter rotor pair so that the generator rotor winding and the exciter winding are connected to form a conducting loop, characterized in that: include: The generator rotor is at rest; The negative electrode of the conduction loop is grounded and the positive electrode is not grounded, and the resistance value between the positive electrode and the negative electrode of the conduction loop is detected to obtain a first resistance value; The positive electrode of the conduction loop is grounded and the negative electrode is not grounded, and the resistance value between the positive electrode and the negative electrode of the conduction loop is detected to obtain a second resistance value; Respectively comparing the first resistance value, the second resistance value and the DC resistance of the rotor winding, and determining the position of the fault grounding point according to the comparison result; The "determining the position of the fault grounding point according to the comparison result" specifically includes: when the first resistance value is less than the DC resistance of the rotor winding and the second resistance value is less than the DC resistance of the rotor winding, determining that the fault grounding point is inside the rotor winding; when the first resistance value is less than the DC resistance of the rotor winding and the second resistance value is equal to the DC resistance of the rotor winding, determining that the fault grounding point is at the positive pole; when the first resistance value is equal to the DC resistance of the rotor winding and the second resistance value is less than the DC resistance of the rotor winding, determining that the fault grounding point is at the negative pole; when the first resistance value is equal to the DC resistance of the rotor winding and the second resistance value is equal to the DC resistance of the rotor winding, determining that the fault grounding point is inside the excitation winding; Before the "determining the position of the fault grounding point based on the comparison result", it also includes: determining whether the insulation resistance value of the rotor is 0 when the insulation fault occurs. If the insulation resistance value of the rotor is not 0 when the insulation fault occurs, the "determining the position of the fault grounding point based on the comparison result" specifically includes: when the first resistance value is less than the DC resistance of the rotor winding and the second resistance value is less than the DC resistance of the rotor winding, determining that the fault grounding point is inside the rotor winding; when the first resistance value is less than the DC resistance of the rotor winding and the second resistance value is equal to the DC resistance of the rotor winding, determining that the fault grounding point is at the positive pole; when the first resistance value is equal to the DC resistance of the rotor winding and the second resistance value is less than the DC resistance of the rotor winding, determining that the fault grounding point is at the negative ... When the rotor winding DC resistance and the second resistance value are equal to the rotor winding DC resistance, it is judged that the fault grounding point is inside the excitation winding; if the insulation resistance value of the rotor is 0 during the insulation fault, the "judging the position of the fault grounding point based on the comparison result" specifically includes: when one of the first resistance value and the second resistance value is 0 and the other is equal to the rotor winding DC resistance, it is judged that the fault grounding point is at the positive and negative poles; when the first resistance value and the second resistance value are both less than the rotor winding DC resistance and the sum of the first resistance value and the second resistance value is equal to the rotor winding DC resistance, it is judged that the fault grounding point is inside the rotor coil; when the first resistance value and the second resistance value are both equal to the rotor winding DC resistance, it is judged that the fault grounding point is inside the excitation winding.

2. The method for locating a single-point grounding fault of a generator rotor according to claim 1, characterized in that: If the insulation resistance value of the rotor is 0 during an insulation fault, when the first resistance value R1 is 0 and the second resistance value R2 is equal to the DC resistance R0 of the rotor winding, it is judged that the fault grounding point is at the positive pole; when the second resistance value R2 is 0 and the first resistance value R1 is equal to the DC resistance R0 of the rotor winding, it is judged that the fault grounding point is at the negative pole.

3. The method for locating a single-point grounding fault of a generator rotor according to claim 1, characterized in that: The "determining the position of the fault grounding point based on the comparison result" specifically includes: when the first resistance value is less than the DC resistance of the rotor winding, judging that the fault grounding point is inside the rotor winding or the positive pole; when the first resistance value is equal to the DC resistance of the rotor winding, judging that the fault grounding point is at the negative pole or inside the excitation winding; when the second resistance value is less than the DC resistance of the rotor winding, judging that the fault grounding point is at the negative pole or inside the rotor winding; when the second resistance value is equal to the DC resistance of the rotor winding, judging that the fault grounding point is at the positive pole or inside the excitation winding.

4. The method for locating a single-point grounding fault of a generator rotor according to claim 1, characterized in that: The first resistance value and the second resistance value are measured by a double-arm bridge circuit.

5. The method for locating a single-point grounding fault of a generator rotor according to claim 4, characterized in that: The measuring ends of the double-arm bridge circuit are respectively connected to the positive electrode and the negative electrode of the exciter conductive rod to detect the first resistance value and the second resistance value.

6. The method for locating the grounding of a single-point grounding fault of a generator rotor according to claim 1, characterized in that: The positive electrode and the negative electrode respectively include an exciter rectifier wheel, an exciter conductive rod, a rotor pair of wheels, and a portion between a rotor lead and a rotor coil.

7. The method for locating a single-point grounding fault of a generator rotor according to claim 1, characterized in that: The generator is a generator excited by rotating rectification.

8. The method for locating a single-point grounding fault of a generator rotor according to claim 1, characterized in that: The grounding location method for a single-point grounding fault of a generator rotor is used for locating a fault grounding point when the insulation resistance value of the rotor is less than 10 ohms during an insulation fault.

Images