Method for judging end of inter-turn short circuit fault of turbine generator rotor without pulling out guard ring

Abstract

This invention relates to a method for determining the inter-turn short-circuit fault location of a turbine generator rotor without removing the retaining ring. Utilizing the basic characteristics of the generator rotor winding electrical parameters and spatial arrangement, and based on determining that a specific coil in the positive or negative winding has an inter-turn short circuit, this method performs testing and calculations to accurately analyze and determine whether the rotor inter-turn short circuit fault is located at the excitation end or the steam end. This provides a data-driven theoretical basis for determining the fault location and scientifically organizing retaining ring removal for repair, significantly reducing fault repair costs and yielding good social and economic benefits.

Description

Technical Field

[0001] This invention relates to the testing for locating inter-turn short-circuit faults in the rotor windings of generators and synchronous condensers (hereinafter referred to as generators) in the power industry, and in particular to a method for determining the inter-turn short-circuit fault terminal of a turbine generator rotor without removing the retaining ring. Background Technology

[0002] With the increasing frequency of generators participating in deep peak shaving in power systems, generator loads fluctuate within a wide range, and the influence of electromagnetic forces on their rotor windings is also increasing. Inter-turn short-circuit faults in generator rotor windings have become a frequent fault in recent years, seriously affecting the safe and stable operation of the units. With advancements in testing technology, diagnostic testing methods for inter-turn short circuits in generator rotors are becoming increasingly sophisticated. The power industry standard DL / T 1525-2016, "Guidelines for Diagnosing Inter-turn Short-circuit Faults in Salient-pole Synchronous Generators," provides six testing methods, including the AC impedance method, the repetitive pulse method, and the inter-pole voltage method. By comprehensively utilizing these methods, it is possible to diagnose and detect inter-turn short-circuit faults in rotors, and even further determine which specific coil in the positive or negative pole winding has experienced an inter-turn short circuit.

[0003] Generally, short-circuit faults between generator rotor turns are primarily located at the coil end under the retaining ring at the exciter or turbine end, specifically at the coil end or the slot exit point of the rotor. They rarely occur in the straight section of the winding in the middle. On-site handling of faults under the end retaining ring requires first removing the retaining ring. This work requires specialized, large-scale tooling, is difficult, time-consuming, and expensive; the basic cost of removing a single retaining ring is close to one million RMB. Therefore, after fault diagnosis, quickly determining whether the fault location is at the exciter end (exciter end) or the turbine end (turbine end) of the generator rotor, and then conducting targeted on-site repairs, has long been a major challenge. Currently, there is virtually no on-site fault location assessment method. The approach is to first remove one retaining ring to locate the fault; if the fault is not found, another retaining ring is removed for further inspection. This method is somewhat random and unreliable, lacks scientific theoretical basis, and may lead to unnecessary waste of time and money, resulting in prolonged repair time and increased costs. Therefore, improvement and innovation are imperative. Summary of the Invention

[0004] In view of the above situation and to overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for determining the short circuit fault end of the rotor of a steam turbine generator without removing the retaining ring, which can effectively solve the problem of determining whether the fault location of the short circuit between rotor turns is located at the excitation end or the steam end.

[0005] The technical solution solved by this invention is:

[0006] A method for determining the inter-turn short-circuit fault terminal of a steam turbine generator rotor without removing the retaining ring includes the following steps:

[0007] 1. The rotor of the generator under test is located outside the stator bore and is placed horizontally and at rest.

[0008] The rotor of the generator under test is pulled out of the stator chamber and placed horizontally and statically outside the stator chamber. The carbon brushes, slip rings or conductive bolts on the two poles of the rotor have no electrical connection with the outside world.

[0009] II. Determine which specific coil of the generator rotor has an inter-turn short circuit fault.

[0010] Using AC impedance method, repetitive pulse method, inter-electrode voltage or coil voltage method, it is determined which specific coil in the positive or negative winding has an inter-turn short circuit. This coil is called the short-circuit coil.

[0011] III. Electrical Test Circuit Connection

[0012] The electrical test circuit includes a DC power supply test device, a high-precision DC voltmeter, and insulating electrodes (insulating rod contact electrodes), wherein:

[0013] Connect the two voltage output terminals of the DC power supply test device to the two-pole carbon brush slip rings or conductive bolts at the excitation end of the generator rotor. The two measuring terminals of the high-precision DC voltmeter are fixedly connected to two insulating electrodes. The two insulating electrodes are used to measure the overall potential of the short-circuit coil group and the inter-turn potential of each adjacent turn at the excitation end. Connect the input terminal of the DC power supply test device to the 220V or 380V AC power supply on site through a power switch to form the entire electrical test circuit.

[0014] IV. Pressure Boost Measurement

[0015] First, adjust the output of the DC power supply test device to zero, close the power switch to supply power to the DC power input side, adjust and increase the output current of the DC power supply, and when the value of the output current monitoring meter of the DC power supply device reaches 100A±5A, stop adjusting and keep the output DC current relatively stable.

[0016] The overall potential of the short-circuit coil and the inter-turn potential of each adjacent turn are measured by contacting and measuring with insulating electrodes. The test data of each corresponding measuring point are recorded. After recording, the voltage is reduced to zero and the power switch is disconnected.

[0017] V. Data Processing

[0018] The recorded data is summarized and processed as follows:

[0019] Overall potential V0 of the short-circuit coil group: Recorded value, V0;

[0020] Inter-turn potential Vi of adjacent turns of short-circuit coil: Recorded value, Vi, (i = 1, 2, 3…8);

[0021] V1 represents the potential between the first end and the first turn, V2 represents the potential between the first and second turns, ... V8 represents the potential between the seventh and eighth turns;

[0022] Total number of turns N in the short-circuit coil: Recorded value, N;

[0023] The average inter-turn potential Vp of the non-short-circuit turns in the short-circuit coil: calculated value, obtained by taking the four largest values ​​in Vi and calculating their average value;

[0024] Overall characteristic ratio k0: Calculated value, k0 = V0 / Vp;

[0025] Inter-turn characteristic ratio ki: Calculated value, ki = Vi / Vp;

[0026] VI. Judgment of Inter-turn Short Circuit Fault Terminal

[0027] a. Based on the overall characteristic ratio k0, the short-circuited winding is confirmed. When the value of k0 is within the range of (N-1, N-1+0.5), that is, within (N-1, N-0.5), the short circuit of 1 turn is confirmed.

[0028] b. Determine the fault location based on the inter-turn characteristic ratio ki:

[0029] When a short circuit occurs in one turn, if there is one and only one inter-turn characteristic ratio ki value in the range of (0, 0.4), and the other inter-turn characteristic ratio ki values ​​are in the range of (0.95-1.05), the fault terminal is determined to be located at the excitation terminal.

[0030] When there are two inter-turn characteristic ratios ki values ​​that are both in the range of (0.4, 0.75), and other inter-turn characteristic ratios ki values ​​are in the range of (0.95-1.05), the fault is determined to be located at the steam end.

[0031] The detection method of this invention is simple and reasonable, with clear steps and explicit criteria. Utilizing the basic characteristics such as the electrical parameters and spatial arrangement of the generator rotor winding, and based on determining that a specific coil in the positive or negative winding has an inter-turn short circuit, this method is implemented for testing and calculation. It accurately analyzes and determines whether the fault location of the rotor inter-turn short circuit is at the excitation end or the steam end, providing a data and theoretical basis for determining the fault end and scientifically organizing the removal and repair of the retaining ring. This greatly reduces the cost of fault repair and has good social and economic benefits. Attached Figure Description

[0032] Figure 1 A schematic diagram showing the unfolded connection of the generator rotor winding;

[0033] Figure 2 This is a schematic diagram of the electrical test circuit wiring of the present invention;

[0034] Figure 3 This is a schematic diagram of the winding slot connection of the present invention;

[0035] Figure 4 This is a schematic diagram of a single set of coil connections for a generator rotor as an application example of the present invention (the fault end is at the excitation end, and the 2nd and 3rd turns are short-circuited at the excitation end);

[0036] Figure 5 This is an equivalent circuit diagram of the fault terminal at the excitation terminal in an application example of the present invention;

[0037] Figure 6 This is a schematic diagram of a single set of coil connections for a generator rotor as an application example of the present invention (the fault end is at the steam end, and the 3rd and 4th turns are short-circuited at the steam end);

[0038] Figure 7 This is an equivalent circuit diagram of the fault terminal at the steam end in an application example of the present invention;

[0039] Figure 8 This is an example of the RSO test waveform diagram used in this invention.

[0040] Figure 9-12 This is a photograph of the actual object after the protective ring is removed from the excitation end in an application example of the present invention;

[0041] in, Figure 10 The circled location is the standard fault point location; Figure 11 The insulation at the bottom of the second turn was burned out; Figure 12 The insulation at the top of the third turn was burned out. Detailed Implementation

[0042] The specific embodiments of the present invention will be further described in detail below with reference to the relevant standards and examples.

[0043] This invention provides a method for determining the inter-turn short-circuit fault terminal of a turbine generator rotor without removing the retaining ring, comprising the following steps:

[0044] 1. The rotor of the generator under test is located outside the stator bore and is placed horizontally and at rest.

[0045] The rotor of the generator under test is pulled out of the stator chamber and placed horizontally and statically outside the stator chamber. There are no large metal objects around it, and the carbon brush slip rings (collector rings) or conductive bolts on the two poles of the rotor have no electrical connection with the outside world.

[0046] II. Determine which specific coil of the generator rotor has an inter-turn short circuit fault.

[0047] Using methods such as AC impedance analysis, repetitive pulse analysis, inter-electrode voltage analysis, or coil voltage analysis, it is determined which specific coil in the positive or negative winding (usually referred to as the upper and lower poles based on their spatial position after being placed outside the barrel) has an inter-turn short circuit. This coil is called the short-circuited coil. A schematic diagram of the generator rotor winding connection is shown below. Figure 1 As shown;

[0048] III. Electrical Test Circuit Connection

[0049] The electrical test circuit includes a DC power supply test device, a high-precision DC voltmeter, and insulating electrodes (insulating rod contact electrodes), wherein:

[0050] Connect the two voltage output terminals of the DC power supply test device through a 35-50mm... 2 Copper wires are reliably connected to the two-pole carbon brush slip rings or conductive bolts at the excitation end of the generator rotor. The two measuring terminals of the high-precision DC voltmeter are reliably fixed to two insulated electrodes. These two insulated electrodes are used to measure the overall potential of the short-circuit coil and the inter-turn potential of adjacent turns at the excitation end. The input terminal of the DC power supply test device is connected to a 220V or 380V AC power supply on site via a power switch to form the entire electrical test circuit. See the attached diagram for the test wiring schematic. Figure 2 .

[0051] In the electrical test circuit:

[0052] DC test power supply device: capacity 5-10kVA, output DC current 0-300A, used to output a DC current signal with continuously adjustable current as the test power supply for the rotor winding of the generator under test. For ease of implementation, a DC welding machine with similar functions can be used on site.

[0053] High-precision DC voltmeter: used to measure the DC voltage between electrodes at corresponding positions on the rotor winding, 0.5 grade, 0~50V;

[0054] Insulating electrodes: These are used to contact specific locations such as the conductive bolts at the beginning of the generator rotor winding, the center point between electrodes, and the coil under the retaining ring, facilitating the measurement of the DC voltage between the corresponding electrodes. The middle rod of the insulating electrode is wrapped with insulating material, and the end can be made into a probe that can be bent into a certain shape, facilitating contact with the rotor winding under the retaining ring.

[0055] The DC power supply test device serves as the test power source, and its two voltage output terminals are connected via 35-50mm... 2 A copper wire is used to connect the two poles of the generator rotor. A DC current of about 100A is passed through the entire rotor winding. Two insulated electrodes are used to contact the specific position of the rotor winding to be measured in sequence. A high-precision DC voltmeter is used to measure and record the DC voltage between the insulated electrodes. Data analysis and calculation are performed based on the test results to determine the specific fault.

[0056] IV. Pressure Boost Measurement

[0057] First, adjust the output of the DC power supply test device to zero, close the power switch to supply power to the DC power input side, adjust and increase the output current of the DC power supply, and when the value of the output current monitoring meter of the DC power supply device reaches 100A±5A, stop adjusting and keep the output DC current relatively stable.

[0058] Based on the spatial arrangement of different short-circuit sleeve coils, specific positions such as the first end conductive bolt of the rotor winding, the center point between poles, and the lower coil of the retaining ring are selected. Insulating electrodes are used to contact and measure the overall potential of the short-circuit sleeve coil and the inter-turn potential of each adjacent turn.

[0059] For specific measurement locations, refer to the connection diagram within the slots of most generator rotor windings (see attached diagram). Figure 3 When measuring the overall potential of the short-circuit winding, the electrodes are recommended as shown in Table 1 (taking the upper pole winding located at the top when the rotor is stationary as an example; the lower pole winding is symmetrically referenced at 180 degrees). The measurement position between adjacent turns is: the person stands at the excitation end, facing the rotor steam end, at the left corner of each turn of the winding at the lower excitation end of the retaining ring. Record the test data of each corresponding measuring point. After recording, reduce the voltage to zero and disconnect the power switch.

[0060] Table 1: Electrode positions at the overall potential of the short-circuit coil

[0061]

[0062] V. Data Processing

[0063] The recorded data is summarized and processed as follows:

[0064] Overall potential V0 of the short-circuit coil group: Recorded value, V0;

[0065] Inter-turn potential Vi of adjacent turns of short-circuit coil: Recorded value, Vi, (i = 1, 2, 3…8);

[0066] V1 represents the potential between the first end and the first turn, V2 represents the potential between the first and second turns, ... V8 represents the potential between the seventh and eighth turns;

[0067] Total number of turns N in the short-circuit coil: Recorded value, N;

[0068] The average value of the inter-turn potential of the non-short-circuit turns in the short-circuit coil, Vp: The calculated value takes into full account the need to remove the short-circuit turns, the accuracy of each turn's measurement value, and the slight difference in the inter-turn voltage of each normal turn. Therefore, the average value of the four largest values ​​in Vi is calculated.

[0069] Overall characteristic ratio k0: Calculated value, k0 = V0 / Vp;

[0070] Inter-turn characteristic ratio ki: Calculated value, ki = Vi / Vp;

[0071] VI. Judgment of Inter-turn Short Circuit Fault Terminal

[0072] a. The short-circuit winding is determined based on the overall characteristic ratio k0. When the value of k0 is within the range (N-1, N-1+0.5), i.e. within (N-1, N-0.5), it is determined that one turn is short-circuited. Under normal circumstances, the short circuit will not exceed two turns. Otherwise, the generator may trip due to excessive rotor vibration or excessive rotor current during operation. The defect will not be allowed to develop and expand. At the same time, once an inter-turn short circuit defect is found during periodic maintenance, it will be dealt with immediately on site. The defect will not be allowed to develop and expand.

[0073] b. Determine the fault location based on the inter-turn characteristic ratio ki:

[0074] When a short circuit occurs in one turn, if there is one and only one inter-turn characteristic ratio ki value in the range of (0, 0.4), and the other inter-turn characteristic ratio ki values ​​are in the range of (0.95-1.05), the fault terminal is determined to be located at the excitation terminal.

[0075] When there are two inter-turn characteristic ratios ki values ​​that are both in the range of (0.4, 0.75), and other inter-turn characteristic ratios ki values ​​are in the range of (0.95-1.05), the fault is determined to be located at the steam end.

[0076] This invention has achieved good technical results in practical applications, as illustrated by the following examples:

[0077] The prototype generator model is QFSN-600-2YHG, with a rated capacity of 600MW.

[0078] The rotor winding is divided into positive and negative poles, with 8 sets of coils on each pole. The first set of coils has 6 turns, and the remaining sets of coils have 8 turns each, for a total of (6+7×8)×2=124 turns.

[0079] I. Determine the short-circuit coil

[0080] The repetitive pulse method (RSO) test revealed a clear difference curve between the two poles. Applying a 100V AC voltage for coil voltage testing showed that the overall voltage of the upper pole's eight coils was significantly lower than the lower pole's eight coils, with a difference of 10.69%. Further testing revealed that the voltage of the upper pole's eighth coil was significantly lower than the lower pole's eighth coil, with a difference as high as 52.24%, confirming an inter-turn short circuit in the upper pole's eighth coil. Relevant test waveforms and data are as follows: Figure 8 As shown in Table 2;

[0081] Table 2: Test data using the coil voltage method

[0082] Serial Number Upper pole Voltage (V) Lower pole Voltage (V) Voltage difference (%) 1 All 8 sets 47.6 All 8 sets 53.3 -10.69 2 Sets 1-4 23.2 Sets 1-4 23.2 0.00 3 Sets 5-8 24.9 Sets 5-8 29.7 -16.16 4 Set 8 3.2 Set 8 6.7 -52.24

[0083] II. On-site determination of test data at the faulty end

[0084] The eighth set of positive coils was tested. Based on the spatial arrangement of the eighth set of coils, the two potential reference points selected when measuring the overall potential of the short-circuit coil group were the ventilation hole on the left surface of the eighth set of excitation terminals of the upper pole and the center point between the bottom turns of the eighth set of excitation terminals of the upper pole. When measuring the inter-turn potential Vi of adjacent turns of the short-circuit coil, the two potential reference points selected were the left corner positions of each adjacent turn of the eighth set of coils under the guard ring, which are easy to observe and contact.

[0085] A DC welding machine was used as the DC test power source on site, with a DC current of 95A applied. The DC voltage of the entire rotor winding was approximately 7560mV. The test and calculation data are as follows:

[0086] The total potential of the short-circuit coil (8th set) is V0 = 469.6mV;

[0087] The inter-turn potential Vi (i = 1, 2…8) of adjacent turns of the short-circuit coil is divided into (unit: mV):

[0088] V1 = 66.2, V2 = 10.0, V3 = 66.9, V4 = 66.8, V5 = 64.9, V6 = 65.1, V7 = 64.7, V8 = 65.0 (unit: mV)

[0089] Total number of turns N in the short-circuit coil: Recorded value, N = 8;

[0090] The average inter-turn potential Vp of the non-short-circuit turns in the short-circuit coil: Calculated value, Vp=(66.2+66.9+66.8+65.1) / 4=66.25mV.

[0091] Population characteristic ratio k0: Recorded value k0 = V0 / Vp = 469.6 / 66.25 = 7.088

[0092] Inter-turn characteristic ratio ki: Recorded value ki = Vi / Vp

[0093] Based on the overall characteristic ratio k0, the value of k0 is 7.088, which is within the range of (N-1, N-0.5), that is, within (7, 7.5). Therefore, it is determined that there is a short circuit of 1 turn.

[0094] Data analysis of the inter-turn characteristic ratio ki shows that k2 = 0.151, meaning that there is only one inter-turn characteristic ratio ki value located in the range of (0, 0.4), while the other ki values ​​are all located in the range of (0.95-1.05). Therefore, it is determined that the fault is located at the excitation end.

[0095] After removing the exciter end retaining ring on site, a short circuit fault was found at the exciter end at the corresponding location between the 2nd and 3rd turns, as shown in the diagram. Figure 9-12 As shown. The inter-turn short-circuit fault point was then addressed on-site, and the ends of the exciter were cleaned, some insulation material was replaced, and all test results were normal after the treatment.

[0096] Based on this application example, the method of the present invention is derived as follows:

[0097] When a DC current is applied to the rotor windings, the inter-turn potential difference (inter-turn potential distribution) of different coils in each winding is proportional to the series connection of the DC resistances of the different coils in the windings (DC resistance voltage drop). Therefore, the inter-turn potential difference can be equivalently replaced by the inter-turn resistance value. Since the cross-sectional dimensions of a single-turn coil in the rotor are basically the same, it is easy to know that its resistance value is proportional to its length. Therefore, the inter-turn potential distribution of the short-circuit winding can be transformed into the distribution of inter-turn DC resistance values ​​for equivalent substitution analysis, that is, it can be replaced by the equivalent circuit of series and parallel connection of the coil DC resistance for substitution analysis.

[0098] 1. For ease of calculation and explanation, let the resistance of a single-turn coil be R, and let R = 1 (a dimensionless value). Then we can draw the following conclusion:

[0099] (1) After using resistance values ​​instead of potential differences, the inter-turn potential, the average inter-turn potential Vp of non-short-circuit turns, and the inter-turn characteristic ratio ki can be directly converted into resistance values. The corresponding relationships are shown in the table below:

[0100] Original parameter name Equivalent conversion parameter names Converted parameter values Potential difference resistance difference Average inter-turn potential Vp of non-short-circuit turns Normal single-turn resistor R 1 Overall potential of the short-circuit coil (8 turns) The total resistance value of the coil is R0 Approximately 7-7.5 Overall characteristic ratio k0 = V0 / Vp k0=R0 / R=R0 Approximately 7-7.5 Inter-turn characteristic ratio ki = Vi / Vp Single-turn resistance value ki = Ri / R = Ri Normal turns Ri = 1, abnormal turns Ri < 1

[0101] (2) The single-turn resistance value Ri and the DC resistance values ​​between each distributed measuring point are proportional to the total length of the single turn and the length between each distributed measuring point. That is, the resistance value can be further converted into the conductor length value of the single turn. According to the typical rotor data, the rotor's long shaft length is 7 meters and the end length is 1 meter. Then, when the single-turn resistance R = 1, the corresponding conductor length is 7 + 1 + 7 + 1 = 16 meters. That is, the DC resistance value per unit length of the conductor in a single turn is 1 / 16. The corresponding resistance values ​​of the 7-meter conductors on both sides of the rotor's long shaft are 7 / 16, and the corresponding resistance values ​​of the 1-meter conductors at the excitation end and steam end are 1 / 16.

[0102] 2. The fault is at the excitation end.

[0103] When a winding containing 8 turns has inter-turn short-circuit points C and D at the excitation end between the 2nd and 3rd turns (for ease of drawing and explanation, the analysis focuses on the short-circuit points between the 2nd and 3rd turns; the analysis method for other locations is similar), its equivalent schematic diagram and equivalent resistance circuit diagram are as follows: Figure 4 and Figure 5 As shown, V2 and V3 are the potentials between the 2nd and 3rd turns and between the 3rd and 4th turns, respectively.

[0104] Figure 5 For ease of understanding and viewing, the equivalent diagram of the 8-turn coil is shown. In reality, each turn of the coil is a coil stacked in the same slot, with the same cross-sectional area and the same length along the rotor length direction, differing only slightly in length at the ends. A typical length is 7 meters along the rotor's long axis, with the length of each end turn gradually increasing from the 1st to the 8th turn, approximately 0.6-1.2 meters. For ease of analysis and calculation, the end length is taken as 1 meter. Point C is located at the midpoint of the line segment between points 2 on the left and 2 on the right in the diagram. Based on the preceding information, the approximate segmented resistance values ​​between each marker point are:

[0105] R A-左1 =1,R 左1-右2 =15 / 16,R 右2-C =1 / 16 * 1 / 2 = 1 / 32, R D-左3 =1 / 16 * 1 / 2 = 1 / 32, R 左3-B =5

[0106] It can be calculated that the resistance of the entire series circuit of the 8th coil single resistor is approximately 1 + 15 / 16 + 1 / 32 + 1 / 32 + 5 = 7, which is approximately equal to n-1 times the potential of a single-turn coil; in the parallel circuit including the inter-turn short circuit point, R C-左2 R 左2-右3 R 右3-D The total resistance of the circuit is approximately equal to 1, while the value of the RCD branch at the short-circuit point is smaller, usually less than 1 / 4 or even smaller; otherwise, it cannot truly constitute an inter-turn short-circuit fault that can affect the potential. Taking 1 / 4 here, the total resistance of the parallel branch is 0.2.

[0107] The total circuit resistance of the short-circuit winding can be calculated to be 7 + 0.2 = 7.2.

[0108] The potential values ​​of adjacent turns can be calculated as follows using a resistive circuit:

[0109] V1, R1, k1 1 V2, R2, k2 0.975 V3, R3, k3 0.225 V4, R4, K4 1 V5, R5, K5 1 V6, R6, K6 1 V7, R7, K7 1 V8, R8, K8 1

[0110] The potential short circuit range of the coil under the retaining ring, i.e. the coil end or the slot outlet of the rotor, is between points 2 on the left and 2 on the right, or within 0.5 meters of points 2 on the left and 2 on the right in the direction of the rotor's long axis. This can be calculated and derived similarly to the above.

[0111] From the above derivation and the data in the table above, it can be seen that under normal conditions without short circuits, the total DC resistance R0 (total potential V0) of the 8-turn coil in series is 8. Under the condition of a 1-turn short circuit, the total circuit resistance R0 (total potential V0) is reduced to 7.2, that is, the overall characteristic ratio k0 = V0 / Vp = R0 / R = R0 is located in the interval (7, 7.5). At the same time, there is only one inter-turn characteristic ratio ki = Vi / Vp = Ri / R = Ri (k3) with a value of 0.225, located in the interval (0, 0.4), while the other ki are all located in the interval (0.95-1.05). This is consistent with the criterion described in the method of this invention: "When a 1-turn short circuit occurs, if there is only one inter-turn characteristic ratio ki located in the interval (0, 0.4), and the other inter-turn characteristic ratio ki are located in the interval (0.95-1.05), the fault terminal is determined to be located at the excitation terminal."

[0112] Similarly, it can be deduced that when the short circuit point is located at points 2 on the left and 2 on the right, and when the rotor's long axis is 0.5 meters away from points 2 on the left and 2 on the right, that is, at the boundary point of the excitation end short circuit range, the values ​​are as follows: (RCD is still taken as 1 / 4. When the RCD value is smaller, the Ki of the corresponding special turn is also smaller.)

[0113]

[0114]

[0115] From the above derivation, within the range where a short circuit may occur under the retaining ring, the converted and derived resistance value (dimensionless value), i.e., the inter-turn characteristic ratio ki, is located between 0.25 and 0.32. Considering some minor error factors in actual field measurements, such as the RCD value between short-circuit points, coil length deviation, and measurement voltage deviation, the range of ki values ​​is appropriately widened, and its range is defined as (0, 0.4). The result does not affect the final logical judgment.

[0116] 3. The fault is at the steam end.

[0117] When a winding containing 8 turns has inter-turn short-circuit points E and F at the steam end between the 3rd and 4th turns (for ease of drawing and explanation, the analysis focuses on the short-circuit points between the 3rd and 4th turns; the analysis method for other locations is similar), its equivalent schematic diagram and equivalent resistance circuit diagram are as follows: Figure 6 and Figure 7 As shown.

[0118] Similar to the analysis at the fault end on the steam side, the typical length is 7 meters along the rotor's long axis. The length of each turn at the end gradually increases from the 1st to the 8th turn, approximately 0.6-1.2 meters. Taking the end length as 1 meter, and assuming point F is located at the midpoint of the line segment between points 2 on the left and 2 on the right in the diagram, then approximately:

[0119] R A-左2 =2,R 左2-汽左2 =7 / 16,R 汽左2-F =1 / 16 * 1 / 2 = 1 / 32, R E-左4 =1 / 16 * 1 / 2 + 1 / 2 = 17 / 32, R 左4-B =4

[0120] It can be calculated that the resistance of the entire series circuit of the 8th coil single resistor is 2 + 7 / 16 + 1 / 32 + 17 / 32 + 4 = 7, which is approximately equal to n-1 times the potential of a single-turn coil; in the parallel circuit including the inter-turn short circuit point, R F-汽右2 R 汽右2-左3 R 左3-汽左3 R 汽左3-E The total resistance of the circuit is approximately equal to 1, while the resistance of the RCD branch at the short-circuit point is much smaller, typically less than 1 / 4 or even less; otherwise, it cannot truly constitute an inter-turn short-circuit fault that can affect the potential. Taking 1 / 4 as the value here, the parallel branch resistance is 0.2.

[0121] The total circuit resistance of the short-circuit winding can be calculated to be 7 + 0.2 = 7.2.

[0122] The potential values ​​of adjacent turns can be calculated as follows using a resistive circuit:

[0123] V1, R1, k1 1 V2, R2, k2 1 V3, R3, k3 0.575 V4, R4, K4 0.625 V5, R5, K5 1 V6, R6, K6 1 V7, R7, K7 1 V8, R8, K8 1

[0124] The potential short-circuit location range of the coil under the retaining ring, i.e. the coil end or the slot outlet of the rotor slot, is between two points, Steam Left 3 and Steam Right 3, or within 0.5 meters of Steam Left 3 and Steam Right 3 in the direction of the rotor's long axis. This can be calculated and derived similarly to the above.

[0125] From the above derivation and the data in the table above, it can be seen that under normal conditions without short circuits, the total DC resistance R0 (total potential V0) of the 8-turn coil in series is 8. Under the condition of a short circuit of 1 turn, the total circuit resistance R0 (total potential V0) is reduced to 7.2, that is, the overall characteristic ratio k0 = V0 / Vp = R0 / R = R0 is located in the range of (7, 7.5). At the same time, there are two inter-turn characteristic ratios ki (k3 and k4), with values ​​of 0.575 and 0.625 respectively, both located in the range of (0.4, 0.75), while the other ki values ​​are all 1. This is consistent with the criterion described in the method of this invention: "When there are two inter-turn characteristic ratios ki values ​​both located in the range of (0.4, 0.75), and the other inter-turn characteristic ratios ki values ​​are located in the range of (0.95-1.05), the fault end is determined to be located at the steam end."

[0126] Similarly, it can be deduced that when the short circuit point is located at points 3 on the left side of the steam engine and 3 on the right side of the steam engine, and when the rotor's long axis is 0.5 meters away from points 3 on the left side of the steam engine and 3 on the right side of the steam engine, that is, at the boundary point of the short circuit range at the steam end, the values ​​are respectively: (still taking rcd as 1 / 4, when the rcd value is smaller, the ki of the corresponding special turn still meets the condition)

[0127] Short circuit point boundary location Ki value of special turns Left 3 0.578，0.672 Car right 3 0.625，0.625 0.5 meters below the left side of the car. 0.555，0.695 0.5 meters below the right side of the car. 0.648，0.602

[0128] From the above derivation, within the range where a short circuit may occur under the retaining ring, the converted and derived resistance value (dimensionless value), i.e., the inter-turn characteristic ratio ki, is located between 0.555 and 0.695. Considering some minor error factors in actual field measurements, such as the RCD value between short-circuit points, coil length deviation, and measurement voltage deviation, the range of ki values ​​is appropriately widened, and its range is defined as (0.4, 0.75). The result does not affect the final logical judgment.

[0129] In practical applications, the methods of this invention have achieved the expected technical effects. Other application examples are listed in the table below:

[0130]

[0131] In the above application examples, after the exciter end retaining ring was removed on-site, the fault points were all consistent with the judgment made by the method of the present invention, indicating that the method of the present invention has high accuracy.

Claims

1. A method for determining the inter-turn short-circuit fault terminal of a turbine generator rotor without removing the retaining ring, characterized in that, Includes the following steps:

1. The rotor of the generator under test is located outside the stator bore and is placed horizontally and at rest. The rotor of the generator under test is pulled out of the stator chamber and placed horizontally and statically outside the stator chamber. The carbon brushes and slip rings on the two poles of the rotor are not electrically connected to the outside world, or the conductive bolts are not electrically connected to the outside world. II. Determine which specific coil of the generator rotor has an inter-turn short circuit fault. Using AC impedance method, repetitive pulse method, inter-electrode voltage or coil voltage method, it is determined which specific coil in the positive or negative winding has an inter-turn short circuit. This coil is called the short-circuit coil. III. Electrical Test Circuit Connection The electrical test circuit includes a DC power supply test device, a high-precision DC voltmeter, and insulating electrodes, wherein: Connect the two voltage output terminals of the DC power supply test device to the two-pole carbon brush slip rings or conductive bolts at the excitation end of the generator rotor. The two measuring terminals of the high-precision DC voltmeter are fixedly connected to two insulating electrodes. The two insulating electrodes are used to measure the overall potential of the short-circuit coil group and the inter-turn potential of each adjacent turn at the excitation end. Connect the input terminal of the DC power supply test device to the 220V or 380V AC power supply on site through a power switch to form the entire electrical test circuit. IV. Pressure Boost Measurement First, adjust the output of the DC power supply test device to zero, close the power switch to supply power to the DC power input side, adjust and increase the output current of the DC power supply, and when the value of the output current monitoring meter of the DC power supply device reaches 100A±5A, stop adjusting and keep the output DC current relatively stable. The overall potential of the short-circuit coil and the inter-turn potential of each adjacent turn were measured by contacting and measuring with insulating electrodes. Record the test data for each corresponding measuring point. After recording, reduce the voltage to zero and disconnect the power switch. V. Data Processing The recorded data is summarized and processed as follows: The overall potential V0 of the short-circuit coil group: recorded value V0; Inter-turn potential Vi of adjacent turns of short-circuit coil: Record value Vi, where i=1,2,3…8; V1 represents the potential between the first end and the first turn, V2 represents the potential between the first and second turns, ... V8 represents the potential between the seventh and eighth turns; Total number of turns N in the short-circuit coil: Recorded value N; The average inter-turn potential Vp of the non-short-circuit turns in the short-circuit coil is obtained by taking the four largest values ​​in Vi and calculating their average value. Overall characteristic ratio k0: Calculated value k0 = V0 / Vp; Inter-turn characteristic ratio ki: Calculated value ki = Vi / Vp; VI. Judgment of Inter-turn Short Circuit Fault Terminal 6.1: The short-circuited winding is determined based on the overall characteristic ratio k0. When the value of k0 is within the range of N-1 to N-1+0.5, the short circuit of 1 turn is determined. 6.2: Fault identification based on the inter-turn characteristic ratio ki: When a short circuit occurs in one turn, if there is one and only one inter-turn characteristic ratio ki value in the range of 0 to 0.4, and the other inter-turn characteristic ratio ki values ​​are in the range of 0.95 to 1.05, the fault terminal is determined to be located at the excitation terminal. When there are two inter-turn characteristic ratios ki values ​​that are both in the range of 0.4 to 0.75, and other inter-turn characteristic ratios ki values ​​are in the range of 0.95 to 1.05, the fault is determined to be located at the steam end.

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