CN114545112A - Method for detecting poor contact between slip ring and carbon brush of hydraulic generator - Google Patents

Abstract

The invention provides a method for detecting poor contact between a slip ring and a carbon brush of a hydraulic generator, which comprises the steps of collecting temperatures of the positive and negative electrodes of the slip ring, voltage and current of a rotor in real time, calculating a temperature change trend of the slip ring and a resistance change trend of the rotor, comparing real-time data with a health sample, and judging that equipment parts have faults or are degraded if the temperatures of the positive and negative electrodes of the rotor loop and the slip ring change (develop towards a degradation direction relative to a normal value) at a certain moment under the same working condition. The invention can realize the detection of faults in advance and the formulation of disposal measures, improve the stability of unit operation and prolong the service life of equipment.

Description

Method for detecting poor contact between slip ring and carbon brush of hydraulic generator

Technical Field

The invention relates to a method for detecting a fault of poor contact between a slip ring and a carbon brush of a hydraulic generator, which is a method for detecting the fault of poor contact between the slip ring and the carbon brush of the hydraulic generator based on the temperature change of the slip ring of the hydraulic generator and the resistance change of a rotor loop and belongs to the technical field of fault detection of the hydraulic generator.

Background

The slip ring is an important device for current transmission between fixed equipment and rotating equipment, the slip ring is a terminal of a rotor coil, the slip ring rotates along with a rotor, the carbon brush is fixed on the brush holder and guides exciting current into the slip ring, and the contact performance of the carbon brush and the slip ring directly influences the running condition of the generator. Poor contact between the slip ring and the carbon brush of the generator is a common fault in the running process of the generator, which can cause the contact resistance between the slip ring and the carbon brush to be increased, and the phenomena of heating, power generation, ignition and the like occur, thus causing the electrical corrosion on the surface of the slip ring. The poor contact between the slip ring and the carbon brush can cause the carbon brush to be abraded too fast, the maintenance frequency is increased, the temperature of the carbon brush and the slip ring is overheated due to friction, and even a fire disaster can be caused in serious cases.

The existing technology for solving the above problems is to install an online carbon brush monitoring device to monitor the current, temperature and abrasion loss of each carbon brush in real time; and secondly, whether power generation exists between the slip ring and the carbon brush is judged by detecting electric wave signals emitted during discharging. The running condition of each carbon brush can be accurately monitored by additionally arranging the online monitoring device, but the number of the carbon brushes of the large-scale water turbine generator set is large (for example, 650MW unit, the number of the carbon brushes of a single unit is 48-62), sensors for measuring temperature, current and the length of the carbon brushes are required to be arranged on each brush holder, the whole slip ring is required to be reformed due to airtight and narrow space, the investment is large, the online monitoring device is applied to water and electricity in recent years, the online monitoring device is not popularized in a large quantity, and the data acquisition accuracy and the system stability are still required to be improved. The method for judging the discharge fault of the slip ring and the carbon brush by detecting the discharge signal is mainly used for the double-fed asynchronous wind driven generator and is not popularized and applied to the hydraulic generator.

Disclosure of Invention

In order to accurately detect the poor contact between the slip ring and the carbon brush of the generator and avoid the problems of unit shutdown and the like caused by slip ring faults, the invention provides a method for detecting the poor contact between the slip ring and the carbon brush of the hydraulic generator.

The invention is realized by the following technical scheme: a method for detecting poor contact between a slip ring and a carbon brush of a hydro-generator comprises the following steps:

(1) when the hydraulic generator is set to operate under the working conditions that the active power is P and the reactive power is Q, the normal temperature of the positive electrode of the slip ring is T_{Front (P, Q)}The temperature of the cathode of the slip ring cathode is T_{Negative (P, Q)}Normal voltage of generator rotor is U_(P,Q)Normal electricity of generator rotorThe flow is I_(P,Q)；

(2) Because the hydro-generator has many and complicated operating condition influence factors and is influenced by the precision error of the acquisition sensor, the temperature of the anode and the cathode of the slip ring, the rotor voltage and the rotor current data acquired at different moments are not completely the same even under the condition of the same active power P and reactive power Q. Therefore, when the active power is P and the idle power is Q, the temperature of the positive electrode of the slip ring acquired at the moment i is recorded as T_{Positive (P, Q) i}And the slip ring negative electrode temperature is recorded as T_{Negative (P, Q) i}And the generator rotor voltage is recorded as U_(P,Q)iThe generator rotor current is marked as I_(P,Q)i；

(3) Calculating the resistance of the rotor loop according to the rotor voltage and the rotor current obtained in the step (2) by the following formula:

in the formula, R_(P,Q)iThe loop resistance of the rotor is expressed when the rotor operates under the working condition that the active power is P and the reactive power is Q at the moment i;

(4) after the water turbine generator set is normally and stably operated for a long time, the data collected under the working conditions that the active power is P and the reactive power is Q at different moments are recorded to obtain the positive and negative electrode temperatures of the slip ring and the rotor loop resistance data set under the working conditions that the active power is P and the reactive power is Q:

slip ring positive temperature data set, namely: t is_{Positive (P, Q)1}、T_{Positive (P, Q)2}、....、T_{Positive (P, Q) n}；

Slip ring negative temperature data set, namely: t is_{Negative (P, Q)1}、T_{Negative (P, Q)2}、....、T_{Negative (P, Q) n}；

Rotor loop resistance data set, namely: r_(P,Q)1、R_(P,Q)2、....、R_(P,Q)n；

(5) According to the data group in the step (4), respectively calculating corresponding average values as normal values of the hydraulic generator under the working conditions that the active power is P and the idle power is Q, namely:

(6) r obtained according to step (5)_(P,Q)、T_{Front (P, Q)}、T_{Negative (P, Q)}And respectively calculating the temperature change rates of the rotor loop resistor and the slip ring anode and cathode:

η_Rthe change rate of the rotor loop resistance relative to the normal value is shown when the working condition that the active power is P and the reactive power is Q at the moment i is operated;

η_{is just}The change rate of the positive electrode temperature of the slip ring relative to the normal value is shown when the working condition that the active power is P and the reactive power is Q at the moment i is operated;

η_{negative pole}The variation rate of the temperature of the cathode of the slip ring relative to the normal value is shown when the working condition that the active power is P and the reactive power is Q is operated at the moment i;

(7) eta calculated according to the step (6)_R、η_{Is just}、η_{Negative pole}Respectively judging the variation trends of the rotor loop resistance, the slip ring anode temperature and the slip ring cathode temperature:

η_R>0, indicating that the rotor circuit resistance is increasing;

η_{is just}>0, indicating that the slip ring positive electrode temperature is increasing;

η_{negative pole}>0, indicating that the slip ring positive electrode temperature is increasing;

(8) and (4) according to the calculated data and the set data obtained in the steps (3) to (6), carrying out the following judgment:

A、η_R>0 and η_{Is just}>0, or η_{Is just}>0, judging: the positive electrode of the slip ring and the carbon brush have poor contact failure;

B、η_R>0 and η_{Negative pole}>0, or η_{Negative pole}>0, judging: the negative pole of the slip ring has bad contact fault with the carbon brush;

C、η_R>0 and η_{Is just}>0 and η_{Negative pole}>0, or η_{Is just for}>0 and η_{Negative pole}>0, judging: poor contact faults exist among the positive electrode and the negative electrode of the slip ring and the carbon brush;

D、η_R>0, judging: poor contact faults can exist in the excitation circuit;

E、η_Rless than or equal to 0 and eta_{Is just for}Less than or equal to 0 and eta_{Negative pole}And (5) judging whether the content is less than or equal to 0: the excitation circuit is good, and the slip ring has good running condition;

F、η_{is just}And (5) judging whether the content is less than or equal to 0: the positive electrode of the slip ring is in good contact with the carbon brush;

G、η_{negative pole}And (5) judging whether the content is less than or equal to 0: the slip ring cathode is in good contact with the carbon brush;

H、η_Rand (5) judging whether the content is less than or equal to 0: the excitation circuit connecting member is excellent.

And (5) according to the detection result of the step (8), making inspection measures in time and making a maintenance treatment plan. If the poor contact between the slip ring and the carbon brush is detected, the abrasion length and pressure of the carbon brush are detected and measured on site, and if the length of the carbon brush is insufficient, replacement adjustment is carried out; checking whether the connection between the carbon brush and the brush braid, and between the brush braid and the brush frame is loosened and local sparks are generated, and fastening or replacing if the connection is loosened; and if the surface of the slip ring is uneven, making an overhaul plan to carry out turning and polishing treatment on the slip ring. If the excitation loop is detected to have poor contact faults, the rotor lead connection part, the excitation cable lap joint part and the rotor magnetic pole connecting piece need to be checked to determine whether looseness exists.

The invention is based on the following principle:

when the hydraulic generator operates normally and stably, the temperatures of the rotor loop resistance, the anode and the cathode of the slip ring should be relatively stable under the same working condition. The invention calculates the normal value of the generator in normal and stable operation by a big data statistical method, namely a 'health sample'. Comparing the real-time data with the healthy sample, and judging that the equipment component has a fault or is degraded if the temperatures of the rotor loop resistor and the anode and the cathode of the slip ring change (develop towards the degradation direction relative to a normal value) at a certain moment under the same working condition.

(1) And calculating the average value of the normal temperature values of the rotor loop resistance and the slip ring positive and negative electrodes by using a big data statistical method. When the hydraulic generator normally and stably operates, the collected data of the rotor loop resistance, the positive and negative electrode temperatures of the slip ring conform to normal distribution (Gaussian distribution), and the longer the operation time of the generator is, the more the collected data is, and the more accurate the normal value calculated by using a big data statistical method is.

(2) When the hydro-generator operates at a certain moment, the change rate of the rotor loop resistance and the temperature of the anode and the cathode of the slip ring is larger than zero relative to the change rate of the stable value under the same working condition, which indicates that the rotor loop resistance and the temperature of the anode and the cathode of the slip ring under the same working condition develop towards the degradation trend than the normal stable operation.

(3) The contact area of the carbon brush and the slip ring is reduced (the contact is point contact or line contact), the carbon brush and the slip ring are displaced when being installed, the pressure of a spring of the carbon brush is too large or too small, oil stains or dirt exist on the surface layer of the slip ring, the carbon brush is loosened and ignited due to vibration, poor contact between the slip ring and the carbon brush can be caused, and the temperature of the slip ring is increased.

(4) The rotor loop resistance is the rotor internal (magnetic pole, lead) resistance + slip ring and carbon brush contact resistance + excitation cable and cable joint resistance. The contact fault of the slip ring and the carbon brush cannot be judged only by increasing the resistance of the rotor loop, the contact fault of the slip ring and the carbon brush is judged and checked together with the increase of the temperature of the slip ring, and the judgment logic is shown in figure 1.

(5) Therefore, the fault detection method can judge the fault of poor contact between the slip ring and the carbon brush through the increase of the temperature of the slip ring and the increase of the resistance of the rotor loop.

The invention has the following advantages and effects: through gathering sliding ring temperature, rotor voltage and electric current in real time, detect sliding ring and carbon brush contact failure, formulate the disposition measure in advance, avoid taking place the equipment accident, improve the stability of unit operation, extension equipment life cycle provides reliable technical support for the operation unit stator bar of water power plant connects the contact state, has fine practical meaning and spreading value. When the contact between the slip ring and the carbon brush of the generator is poor, the slip ring can be burnt and damaged, and the unplanned shutdown can be caused, so that the good contact between the slip ring and the carbon brush can be ensured, and the key for ensuring the normal operation of a generating set of a power plant is realized. According to the method, the fault of poor contact between the slip ring and the carbon brush can be effectively detected, and early warning is carried out before equipment is damaged. By the method, when fault early warning is detected, field detection is carried out, the patrol frequency of power station personnel is reduced, 30 working hours are saved every month, meanwhile, artificial measurement errors are avoided, and online real-time detection is realized.

Drawings

FIG. 1 is a logic diagram of the joint judgment of the temperatures of a rotor loop resistor and a slip ring;

FIG. 2 is a schematic diagram of a slip ring negative contact surface with uneven streaks;

fig. 3 is a schematic view showing a negative electrode carbon brush having a contact surface with a significant dent.

Detailed Description

The present invention will be further described with reference to the following examples.

Example 1

The following data is obtained from an existing computer system at the time of operation of a plant number 3 unit:

(1) the unit is obtained when the active power is P (520 and 530MW) and the reactive power is Q (70 to 80MVar) from 4 months and 4 days and 25 months in 2020 to 2021 (serial numbers 1 to 21 in the table): and calculating the resistance R of the rotor loop according to a calculation formula of the slip ring anode temperature, the slip ring cathode temperature, the rotor voltage and the rotor current data:

in the formula, R_(P,Q)iRepresenting the loop resistance of the rotor when the rotor operates under the working condition that the active power is P and the reactive power is Q at the moment i;

(2) calculating data under working conditions that active power is P and reactive power is Q at different moments obtained in the step (1) to obtain data sets of positive and negative temperatures of the slip ring and resistance of the rotor loop under the working conditions that the active power is P and the reactive power is Q:

slip ring positive temperature data set (21): 69.3, 69.5, 68.9, 68.2, 69.8, 68.3, 68.5, 69.5, 69.2, 69.7, 68.4, 69.5, 70.2, 70.5, 70.8, 70.9, 70.3, 71.1, 71.8, 71.4;

slip ring negative temperature data set (21): 74.3, 73.9, 73.8, 74.2, 74.1, 73.7, 73.5, 74.2, 74.3, 74.2, 74, 73.9, 74.3, 74.4, 74.2, 75.1, 75.9, 76.3, 76.6, 77.2, 77.3;

rotor circuit resistance data set (21): 105.3, 108.9, 110.2, 101.1, 113.1, 112.5, 108.9, 107.1, 101.5, 105.6, 104.3, 109.9, 114.1, 115.5, 119.2, 118.7, 121.2, 124.2, 120.9, 129.5, 130.1;

(3) respectively calculating corresponding average values according to the following calculation formulas to serve as normal values of the hydraulic generator under the working conditions that the active power is P and the idle power is Q:

(4) respectively calculating the change rate of the rotor loop resistance and the positive and negative temperature change rates of the slip ring collected at 25 days in 4 months in 2021 according to the following calculation formula, namely:

(5)η_R>0 and η_{Is just}>0 and η_{Negative pole}>0, or η_{Is just}>0 and η_{Negative pole}>0, detecting that: the failure of poor contact between the anode and the cathode of the slip ring and the carbon brush is detected, and early warning is sent out;

(6) according to the early warning condition, arranging personnel to check the flatness of the carbon brush, the brush holder and the slip ring in situ, and finding that the surface of the slip ring has dents and the surface of the carbon brush has dents at the same time through checking, as shown in fig. 2 and 3;

(7) in the power plant, the turning and polishing are carried out on the slip ring and the carbon brush is replaced in 2021, 5 months in combination with the overhaul of the unit, the temperature of the anode and the cathode of the slip ring and the resistance of a rotor circuit are obviously reduced after the replacement, and the normal operation is recovered.

Claims (1)

1. A method for detecting poor contact between a slip ring and a carbon brush of a hydro-generator is characterized by comprising the following steps:

(1) setting the active power of the hydraulic generator to be P and the idle powerWhen the sliding ring operates under the working condition of Q, the normal temperature of the positive electrode of the sliding ring is T_{Front (P, Q)}Normal temperature of slip ring cathode is T_{Negative (P, Q)}Normal voltage of generator rotor is U_(P,Q)The normal current of the generator rotor is I_(P,Q)；

(2) Recording the positive electrode temperature of the slip ring acquired at the moment i as T under the working conditions that the active power is P and the reactive power is Q_{Positive (P, Q) i}And the slip ring negative electrode temperature is recorded as T_{Negative (P, Q) i}And the generator rotor voltage is recorded as U_(P,Q)iThe generator rotor current is marked as I_(P,Q)i；

(3) Calculating the loop resistance of the generator rotor according to the voltage and the current of the generator rotor obtained in the step (2) and the following formula:

in the formula, R_(P,Q)iThe loop resistance of the generator rotor is expressed when the generator rotor operates under the working condition that the active power is P and the reactive power is Q at the moment i;

(4) after the hydroelectric generating set normally operates for a long time, the data collected under the working conditions that the active power is P and the reactive power is Q at different moments are recorded to obtain the anode and cathode temperatures of the slip ring and the resistance data set of the generator rotor loop under the working conditions that the active power is P and the reactive power is Q:

slip ring positive temperature data set, namely: t is_{Positive (P, Q)1}、T_{Positive (P, Q)2}、....、T_{Positive (P, Q) n}；

Slip ring negative temperature data set, namely: t is_{Negative (P, Q)1}、T_{Negative (P, Q)2}、....、T_{Negative (P, Q) n}；

Rotor loop resistance data set, namely: r_(P,Q)1、R_(P,Q)2、....、R_(P,Q)n；

(5) According to the data group in the step (4), respectively calculating corresponding average values as normal values of the hydraulic generator under the working conditions that the active power is P and the idle power is Q, namely:

(6) r obtained according to step (5)_(P,Q)、T_{Front (P, Q)}、T_{Negative (P, Q)}And respectively calculating the temperature change rates of the rotor loop resistor and the slip ring anode and cathode:

η_Rthe change rate of the rotor loop resistance relative to the normal value is shown when the working condition that the active power is P and the reactive power is Q at the moment i is operated;

η_{is just}The change rate of the positive electrode temperature of the slip ring relative to the normal value is shown when the working condition that the active power is P and the reactive power is Q at the moment i is operated;

η_{negative pole}The variation rate of the temperature of the cathode of the slip ring relative to the normal value is shown when the working condition that the active power is P and the reactive power is Q is operated at the moment i;

(7) eta calculated according to the step (6)_R、η_{Is just}、η_{Negative pole}Respectively judging the variation trends of the rotor loop resistance, the slip ring anode temperature and the slip ring cathode temperature:

η_R>0，indicating that the rotor circuit resistance is increasing;

η_{is just for}>0, indicating that the slip ring positive electrode temperature is increasing;

η_{negative pole}>0, indicating that the slip ring positive electrode temperature is increasing;

(8) and (4) according to the calculated data and the set data obtained in the steps (3) to (6), carrying out the following judgment:

A、η_R>0 and η_{Is just}>0, or η_{Is just}>0, judging: the positive electrode of the slip ring and the carbon brush have poor contact failure;

B、η_R>0 and η_{Negative pole}>0, or η_{Negative pole}>0, judging: the negative pole of the slip ring has bad contact fault with the carbon brush;

C、η_R>0 and η_{Is just}>0 and η_{Negative pole}>0, or η_{Is just for}>0 and η_{Negative pole}>0, judging: poor contact faults exist among the positive electrode and the negative electrode of the slip ring and the carbon brush;

D、η_R>0, judging: poor contact faults can exist in the excitation circuit;

E、η_Rless than or equal to 0 and eta_{Is just}Less than or equal to 0 and eta_{Negative pole}And (5) judging whether the content is less than or equal to 0: the excitation circuit is good, and the slip ring has good running condition;

F、η_{is just}And (5) judging whether the content is less than or equal to 0: the positive electrode of the slip ring is in good contact with the carbon brush;

G、η_{negative pole}And (5) judging whether the content is less than or equal to 0: the slip ring cathode is in good contact with the carbon brush;

H、η_Rand (5) judging whether the content is less than or equal to 0: the excitation circuit connecting member is excellent.

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