CN111398761A - Partial discharge signal acquisition device and partial discharge acquisition analyzer - Google Patents
Partial discharge signal acquisition device and partial discharge acquisition analyzer Download PDFInfo
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- CN111398761A CN111398761A CN202010257808.3A CN202010257808A CN111398761A CN 111398761 A CN111398761 A CN 111398761A CN 202010257808 A CN202010257808 A CN 202010257808A CN 111398761 A CN111398761 A CN 111398761A
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- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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Abstract
The invention relates to a partial discharge signal acquisition device, which comprises a discharge signal acquisition card with a storage space and a power frequency signal acquisition card with a storage space, wherein the power frequency signal acquisition card is connected with the discharge signal acquisition card, and the power frequency signal acquisition card and the discharge signal acquisition card both adopt a pulse excitation measurement method to acquire a partial discharge signal and a power frequency voltage signal of a tested device. The invention also relates to a partial discharge acquisition analyzer, which comprises the partial discharge signal acquisition device and a signal processing unit connected with the partial discharge signal acquisition device; the signal processing unit is used for matching the partial discharge signal acquired by the discharge signal acquisition card and the power frequency voltage signal acquired by the power frequency signal acquisition card, and analyzing the phase of the power frequency voltage signal corresponding to the partial discharge signal acquired by the discharge signal acquisition card according to the matching result. The invention can improve the capture efficiency of the discharge pulse, realize the high resolution and long-time sampling of the partial discharge signal and has high reliability.
Description
Technical Field
The invention belongs to the field of power equipment state monitoring and automatic control, and particularly relates to a device for carrying out charged acquisition and analysis on partial discharge of equipment in a transformer substation.
Background
Partial discharge detection is an important link for detecting the state of the power equipment. Because the insulation defect of the power equipment is easy to generate partial discharge under the action of high voltage, the development of the partial discharge can cause further deterioration of insulation and finally cause insulation flashover, the partial discharge condition of the equipment is monitored, and the defect can be timely found and the early warning of the insulation flashover fault is facilitated.
According to the measurement conditions, the partial discharge detection method can be divided into power failure detection, live detection and on-line monitoring. Among the three methods, the power failure detection is higher in detection cost due to the fact that the equipment needs to be accompanied and stopped, and the power failure detection method is generally used only when the power failure detection is carried out in factory test, equipment overhaul or replacement; on-line monitoring theoretically can realize real-time monitoring of equipment, but the interference in the actual operation process is large, the reliability of the measurement result is not high, and the on-line monitoring is less adopted. The live detection does not need equipment to be stopped, has the function of temporarily creating more appropriate experimental conditions so as to improve the reliability of a detection result, is a compromised partial discharge detection method, and is most common in practical application.
At present, various manufacturers at home and abroad put forward own local discharge live detection equipment, which has respective advantages and disadvantages in acquisition mode, recording method and judgment basis, but has the following defects:
1) the capture and recording of dual firing pulses is imperfect. In general, partial discharge of power equipment is considered as a phenomenon of repeated breakdown and recovery of local insulation caused by local electric field distortion, and discharge pulses generated by the phenomenon have continuous repeatability, which is also the basis of judgment of most field partial discharge detection early warning devices at present. However, increasing research in recent years has shown that partial discharges resulting from many insulation defects in electrical equipment do not have a high pulse repetition rate, but rather are sporadic and intermittent. The long interval time between pulses makes it difficult to sample the pulse signals with high precision and for a long time, and the sporadic captured signals are easily considered as external interference and are ignored under the existing alarm mechanism, so that the existing partial discharge detection device has a larger leak.
2) High resolution and long sampling times cannot be achieved simultaneously. Two factors are generally considered when acquiring and recording the local discharge signal. On one hand, in order to study the change rule of the discharge in a long pressurization time, the discharge signal is required to be continuously recorded in a long time; on the other hand, in order to obtain richer waveform data in the signal analysis process, the acquired signal needs to have higher resolution in the time domain. However, in general, as the capturing and recording of the partial discharge signal usually adopts a continuous measurement method, that is, data is continuously sampled within the recording time after the acquisition device is started until the internal storage space is used up, as shown in fig. 1. The two requirements of high sampling accuracy and long recording time of the signal are usually only satisfied by the memory space of the measuring device.
3) The information collection is relatively isolated, and the reliability of the result is not high. The direct reason for the partial discharge is the power frequency high voltage applied to the equipment, so when the partial discharge of the equipment is detected, the discharge signal itself cannot be paid attention to, and various characteristics of the discharge signal and the external construction frequency voltage, especially the relation between the partial discharge signal and the power frequency phase, should be paid attention to. However, most of the existing partial discharge live detection devices do not have a detection means for external construction frequency voltage, and only pay attention to the measurement and analysis of partial discharge signals, so that the measurement result is relatively isolated, and the reliability of the detection result is reduced.
Disclosure of Invention
The invention aims to provide a device which can collect partial discharge of equipment with relatively perfect performance, high resolution, long sampling time and high reliability.
In order to achieve the purpose, the invention adopts the technical scheme that:
a partial discharge signal acquisition device is used for acquiring a partial discharge signal of equipment to be tested, and comprises a discharge signal acquisition card with a storage space, wherein the discharge signal acquisition card acquires the partial discharge signal of the equipment to be tested by adopting a pulse excitation measurement method aiming at the discharge signal;
the pulse excitation measuring method for the discharge signal comprises the following steps:
step 1-1: estimating the discharge pulse duration T of partial discharge of the device to be tested according to the device to be tested, setting the sampling rate S required for collecting the partial discharge signal of the device to be tested, and calculating and recording the size of a storage space required by each discharge pulse according to the discharge pulse duration T and the sampling rate S;
step 1-2: averagely dividing a storage space carried by the discharge signal acquisition card into j pulse storage spaces according to the size of a storage space required by each discharge pulse, wherein the kth pulse storage space is used for correspondingly recording the kth partial discharge signal of the tested equipment, k and j are positive integers, j is more than or equal to 2, and j is more than or equal to k;
step 1-3: setting a trigger threshold value of the discharge signal acquisition card, and starting the discharge signal acquisition card;
step 1-4: when the discharge pulse acquisition card detects that the partial discharge signal of the tested equipment reaches the set trigger threshold, the discharge pulse acquisition card is triggered and starts to acquire the waveform of the partial discharge signal, the acquisition is finished until the acquisition duration reaches the discharge pulse duration T, and the acquired partial discharge signals are stored in a corresponding pulse storage space in sequence;
step 1-5: and if the storage space of the discharge signal acquisition card is not used up, returning to the step 1-4, and if the storage space of the discharge signal acquisition card is used up, stopping acquisition.
The partial discharge signal acquisition device also comprises a power frequency signal acquisition card with a storage space, the power frequency signal acquisition card acquires a power frequency voltage signal of the tested equipment by adopting a pulse excitation measurement method aiming at the power frequency signal, and the power frequency signal acquisition card is connected with the discharge pulse acquisition card;
the pulse excitation measurement method for the power frequency signal comprises the following steps:
step 2-1: averagely dividing a storage space carried by the power frequency signal acquisition card into j power frequency storage spaces, wherein the sampling time T' corresponding to each power frequency storage space is longer than the discharge pulse duration time T, and the kth pulse storage space is used for correspondingly recording the kth section of power frequency voltage signals of the tested equipment;
step 2-2: setting the discharge signal acquisition card to output a power frequency acquisition trigger signal for triggering the power frequency signal acquisition card when the discharge signal acquisition card is triggered each time, and starting the power frequency signal acquisition card;
step 2-3: when the power frequency signal acquisition card detects the power frequency acquisition trigger signal, starting to acquire the waveform of the power frequency voltage signal, ending acquisition until the acquisition duration reaches the sampling duration T', and sequentially storing the acquired power frequency voltage signal and the corresponding power frequency acquisition trigger signal into a corresponding power frequency storage space;
step 2-4: and returning to the step 2-3 if the storage space in the power frequency signal acquisition card is not used up, and stopping acquisition if the storage space in the power frequency signal acquisition card is used up.
And the sampling rate S' required for acquiring the power frequency voltage signal corresponding to each power frequency storage space is lower than the sampling rate S required for acquiring the partial discharge signal of the tested equipment.
The partial discharge signal acquisition device further comprises a signal concentrator which is respectively connected with the discharge signal acquisition card and the power frequency signal acquisition card, and the signal concentrator is used for summarizing the partial discharge signals acquired by the discharge signal acquisition card, the power frequency voltage signals acquired by the power frequency signal acquisition card and the corresponding power frequency acquisition trigger signals and then outputting the summarized signals.
The discharge signal acquisition card is connected with the partial discharge sensor.
And the power frequency signal acquisition card is connected with the power frequency voltage waveform measuring unit.
The invention also provides a partial discharge acquisition analyzer based on the partial discharge signal acquisition device, which comprises the partial discharge signal acquisition device and a signal processing unit connected with the partial discharge signal acquisition device;
the signal processing unit is used for matching the partial discharge signal acquired by the discharge signal acquisition card with the power frequency voltage signal acquired by the power frequency signal acquisition card and analyzing the phase of the power frequency voltage signal corresponding to the partial discharge signal acquired by the discharge signal acquisition card according to the matching result.
The method for matching the partial discharge signal acquired by the discharge signal acquisition card and the power frequency voltage signal acquired by the power frequency signal acquisition card by the signal processing unit comprises the following steps:
step 3-1: according to the triggering time t of the 1 st section of partial discharge signal acquired by the discharge signal acquisition card1And the triggering time tau of the 1 st section of power frequency voltage signal acquired by the power frequency signal acquisition card1Calculating the trigger time error t of the discharge signal acquisition card and the power frequency signal acquisition card1-τ1；
Step 3-2: let n be 2;
step 3-3: according to the trigger time tau of the nth section of power frequency voltage signal acquired by the power frequency signal acquisition cardnTrigger time error t of the discharge signal acquisition card and the power frequency signal acquisition card1-τ1And calculating the matching trigger time t of the discharge signal acquisition card corresponding to the nth section of power frequency voltage signaln′＝τn-τ1+t1；
Step 3-4: searching each section of partial discharge signal acquired by the discharge signal acquisition card to find out the actual trigger time tmWith said matching trigger time tnThe nearest section of partial discharge signal is used as a partial discharge signal matched with the nth section of power frequency voltage signal;
step 3-5: n are accumulated and the step 3-3 is returned.
And for the I section of the partial discharge signal which is not matched with the corresponding power frequency voltage signal, obtaining the phase of the power frequency voltage signal corresponding to the I section of the partial discharge signal according to the phase of the power frequency voltage signal corresponding to the I-1 section of the partial discharge signal and the trigger time delay of the I-1 section of the partial discharge signal and the I section of the partial discharge signal.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: the invention can effectively improve the capture effect of dual-emitted electric pulses, simultaneously realizes high resolution and long-time sampling of partial discharge signals, and has higher reliability of measurement results.
Drawings
Fig. 1 is a schematic diagram of a conventional method for continuously sampling a partial discharge signal.
Fig. 2 is a schematic diagram of a pulse excitation measurement method for a discharge signal adopted by the partial discharge signal acquisition device of the present invention.
FIG. 3 is a schematic diagram of a discharge signal acquisition card and a power frequency signal acquisition card in the partial discharge signal acquisition device of the present invention using an asynchronous measurement method to measure partial discharge and its power frequency phase.
FIG. 4 is a flow chart of the method for matching the partial discharge signal collected by the discharge signal collection card and the power frequency voltage signal collected by the power frequency signal collection card in the signal processing unit of the partial discharge collection analyzer of the present invention.
FIG. 5 is a schematic representation of the results of the process employed in the present invention.
Fig. 6 is a schematic overall layout of the partial discharge acquisition analyzer of the present invention.
Detailed Description
The invention will be further described with reference to examples of embodiments shown in the drawings to which the invention is attached.
The first embodiment is as follows: a partial discharge signal acquisition device comprises a discharge signal acquisition card with a storage space. The discharge signal acquisition card acquires the partial discharge signal of the equipment to be tested by adopting a pulse excitation measurement method aiming at the discharge signal.
The traditional method for measuring and collecting partial discharge signals is time-based, that is, after the start of measurement is set, a collection card starts to continuously collect signals until the required sampling time is reached or the storage space of the collection card is used up. As can be seen from fig. 1, in the continuous measurement method, signal segments and no-signal segments in the waveform data are not distinguished in the measurement process, but for most types of partial discharges, the occupied proportion of the signal segments in the entire waveform data is small, and most of the storage space is occupied by meaningless noise, which causes great waste of the storage space. Especially for sporadic pulse partial discharge with a low pulse repetition rate, it is difficult to capture even discharge pulses by using the above method, and the temporal resolution and the correlation between pulses are not mentioned.
For the above-mentioned defects of the continuous measurement method, as shown in fig. 2, the pulse excitation measurement method for the discharge signal adopted by the partial discharge signal acquisition apparatus of the present invention specifically includes the following steps:
step 1-1: the method comprises the steps of estimating the discharge pulse duration T of partial discharge of the device to be tested according to the device to be tested, setting the sampling rate S required for collecting the partial discharge signals of the device to be tested, and calculating the storage space required for recording each discharge pulse according to the discharge pulse duration T and the sampling rate S.
Step 1-2: and averagely dividing the storage space carried by the discharge signal acquisition card into j pulse storage spaces according to the size of the storage space required by each discharge pulse, wherein the kth pulse storage space is used for correspondingly recording the kth partial discharge signal of the tested equipment, and each pulse storage space can store data which is sampled at a sampling rate S and has sampling time reaching the discharge pulse duration T. k. j is a positive integer, j is more than or equal to 2, and j is more than or equal to k.
Step 1-3: and setting a trigger threshold value of the discharge signal acquisition card, starting the discharge signal acquisition card to enable the discharge signal acquisition card to enter a waiting state, and transferring the electric signal acquisition card to not record data in the waiting state.
Step 1-4: when the discharge pulse acquisition card detects that the partial discharge signal of the tested equipment reaches a set trigger threshold value, the discharge pulse acquisition card is triggered and starts to acquire the waveform of the partial discharge signal, the acquisition is finished until the acquisition duration time reaches the discharge pulse duration time T, the acquired partial discharge signals (recorded waveforms) are stored in a corresponding pulse storage space in sequence, and then the discharge pulse acquisition card enters a waiting state again.
Step 1-5: and (4) if the storage space of the discharge signal acquisition card is not used up, returning to the step 1-4, and if the storage space of the discharge signal acquisition card is used up, namely after the discharge pulse acquisition card is triggered for n times, stopping acquisition.
As can be seen from comparing fig. 1 and fig. 2, since the acquisition device, i.e., the discharge signal acquisition card, does not record data while waiting for triggering, the storage space required by using the pulse excitation method is much smaller than the space occupied by continuous recording for the same segment of signal, i.e., the utilization rate of the storage space can be greatly improved by using the pulse excitation measurement method. For accidental partial discharge, as pulse intervals account for most of recording time, the method can greatly prolong the duration of single acquisition, thereby more effectively monitoring the change rule of the discharge characteristic along with time; in addition, due to the improvement of the utilization rate of the storage space, the pulse excitation measurement method can greatly improve the sampling rate on the premise of keeping long-time recording, so that the original information in the discharge waveform is retained to the maximum extent, and convenience is provided for subsequent data processing.
It should be noted that after the sampling device has performed a recording process, a preparation time, referred to as the blanking time of the sampling device, is required before entering the waiting state, which is denoted by t in fig. 20And (4) showing. This means that if the separation time T of two adjacent pulses satisfies T < T < T + T0The second pulse will be missed. But at present the mainstream sampling equipment t0The value is in the microsecond order, and for accidental pulses, the interval time of adjacent pulses is obviously far longer than the microsecond order, and the possibility of being missed is extremely small; for the frequent pulse, the number of the pulse is huge, and even if some pulses are omitted, the triggering of an alarm mechanism and the subsequent data processing are not influenced. Therefore, the measurement method using pulse excitation still has high reliability.
The power frequency phase when the partial discharge is generated is an important characteristic quantity of the partial discharge, and has important significance for the identification of the discharge type and the fault diagnosis. However, most of the existing partial discharge live detection devices do not have the capability of measuring the external construction frequency voltage of the power equipment, so that the partial discharge signal cannot be compared with the power frequency phase information, and thus important reference information is lost. Therefore, when the local discharge signal is collected, the power frequency voltage signal is also required to be collected.
When the traditional measuring method is used, the storage space is not segmented, and the sampling rate is generally low, so that the duration of single-segment sampling is long, the change of a power frequency voltage signal is obvious, and the phase generated by partial discharge can be directly read. When the pulse excitation measurement method is used for collecting the local discharge signal, the single-section measurement time is usually only microsecond magnitude, and the power frequency voltage signal changes relatively slowly, so that the power frequency voltage signal is almost a constant value in such a short time, and the phase information of the power frequency voltage signal is difficult to read directly. Due to the non-uniqueness of the sine inverse function, it is not feasible to use the amplitude of the power frequency signal to reverse the phase thereof.
For the above problem, a solution idea is to assume that the power frequency period is fixed to 20ms, and calculate the phase of each pulse according to the trigger time of each pulse recorded by the acquisition device. However, in practical situations, the period and amplitude of the power frequency voltage usually fluctuate within a range, and the phase information obtained by using the method is not accurate. Especially for accidental pulses, the long interval time between pulses is easy to cause the accumulative effect of errors, and the reliability is difficult to guarantee.
Therefore, the partial discharge signal acquisition device is designed with the following scheme:
the partial discharge signal acquisition device also comprises a power frequency signal acquisition card with a storage space, the power frequency signal acquisition card acquires a power frequency voltage signal of the tested equipment by adopting a pulse excitation measurement method aiming at the power frequency signal, and the power frequency signal acquisition card is connected with the discharge pulse acquisition card.
The pulse excitation measurement method for the power frequency signal adopted by the power frequency signal acquisition card comprises the following steps:
step 2-1: the method comprises the steps of averagely dividing a storage space carried by a power frequency signal acquisition card into j power frequency storage spaces, wherein the sampling time T 'corresponding to each power frequency storage space is longer than the discharge pulse duration T, the sampling rate S' required for acquiring a power frequency voltage signal corresponding to each power frequency storage space is lower than the sampling rate S required for acquiring a local discharge signal of the tested equipment, and the kth pulse storage space is used for correspondingly recording the kth section of power frequency voltage signal of the tested equipment.
Step 2-2: and setting the discharge signal acquisition card to output a power frequency acquisition trigger signal for triggering the power frequency signal acquisition card each time the discharge signal acquisition card is triggered, and starting the power frequency signal acquisition card, as shown in the attached figure 3.
Step 2-3: when the power frequency signal acquisition card detects a power frequency acquisition trigger signal, starting to acquire the waveform of a power frequency voltage signal, ending acquisition until the acquisition duration time reaches the sampling duration time T', and storing the acquired power frequency voltage signal and the corresponding power frequency acquisition trigger signal into a corresponding power frequency storage space in sequence.
Step 2-4: and (3) if the storage space of the power frequency signal acquisition card is not used up, returning to the step 2-3, and if the storage space of the power frequency signal acquisition card is used up, stopping acquisition.
In summary, the discharge signal acquisition card and the power frequency signal acquisition card in the partial discharge signal acquisition device of the present invention adopt a partial discharge power frequency phase asynchronous measurement method based on multivariate combined acquisition, and the principle thereof is shown in fig. 3. Two acquisition cards (the acquisition card 1 is a discharge signal acquisition card, and the acquisition card 2 is a power frequency signal acquisition card) both use a pulse excitation measurement method to record data, wherein the single-section sampling time of the acquisition card 1 is short, and the sampling rate is high, so as to record local discharge waveforms; the acquisition card 2 has long single-section sampling time and low sampling rate and is used for recording the waveform of the power frequency voltage signal. The trigger output of the acquisition card 1 is connected to the acquisition card 2 and serves as a trigger source of the acquisition card 2, namely, every time the acquisition card 1 records a partial discharge pulse, a pulse is generated on the channel 1 of the acquisition card 2, and the power frequency phase corresponding to the pulse can be read from the waveform recorded by the acquisition card 2.
The partial discharge signal acquisition device further comprises a signal concentrator which is respectively connected with the discharge signal acquisition card and the power frequency signal acquisition card, and the signal concentrator is used for summarizing and outputting the partial discharge signals acquired by the discharge signal acquisition card, the power frequency voltage signals acquired by the power frequency signal acquisition card and the corresponding power frequency acquisition trigger signals. In the scheme, the discharge signal acquisition card is connected with the partial discharge sensor, and the power frequency signal acquisition card is connected with the power frequency voltage waveform measuring unit.
Based on above-mentioned partial discharge signal pickup assembly, design a partial discharge and gather the analysis appearance, the scheme is as follows:
the partial discharge acquisition analyzer comprises a partial discharge signal acquisition device and a signal processing unit connected with the partial discharge signal acquisition device, wherein the signal processing unit is used for matching a partial discharge signal acquired by the discharge signal acquisition card and a power frequency voltage signal acquired by the power frequency signal acquisition card and analyzing the phase of the power frequency voltage signal corresponding to the partial discharge signal acquired by the discharge signal acquisition card according to the matching result.
As mentioned before, the acquisition device has a turn-off time t of several microseconds between two adjacent acquisitions0This extinguishing time is present on both acquisition cards. If the discharge pulse happens to appear at the moment when the acquisition card 1 is in the waiting state and the acquisition card 2 is in the extinguishing state, the pulse measured on the acquisition card 1 cannot be recorded on the acquisition card 2, i.e. the pulse on the acquisition card 1 cannot necessarily find the corresponding signal on the acquisition card 2, which is particularly easy to appear when the pulse repetition rate of the discharge source is high. For this reason, an algorithm needs to be designed to match the pulses on the two acquisition cards. The method for matching the partial discharge signal acquired by the discharge signal acquisition card and the power frequency voltage signal acquired by the power frequency signal acquisition card by the signal processing unit comprises the following steps:
with S1Representing a set of pulses recorded by the acquisition card 1, containing M, p elementsmRepresenting pulses therein, i.e. pm∈S1，tmRepresents the trigger time of the pulse; with S2Representing a set of pulses recorded by the acquisition card 2, containing N, q elementsnRepresenting pulses therein, i.e. qn∈S2，tnIndicating the time of triggering of the pulse. Due to the fact that
Therefore with S2De-matching S with reference to the signal in1Of (2). This practice will lose a part of S1The measured signal needs to be compensated for by subsequent processing.
Step 3-1: due to p1Must be in accordance with q1Correspondingly, if the two signals are synchronous in trigger time, the trigger time t of the 1 st section of partial discharge signal acquired by the discharge signal acquisition card is used1And the triggering time tau of the 1 st section of power frequency voltage signal acquired by the power frequency signal acquisition card1Calculating the trigger time error t of the discharge signal acquisition card and the power frequency signal acquisition card1-τ1. Thus tnThe corresponding trigger time on the discharge signal acquisition card is tn′＝τn-τ1+t1I.e. at tmMust be present with tnEqual trigger time, the pulses corresponding to these two time values are the matching pulses.
From n to 2, search for t one by onemNeutralization of tn' t having the smallest difference valuemThe pulse corresponding to the two is the matching pulse; then N is increased, and the above steps are repeated until N ═ N, as shown in fig. 4, specifically as follows:
step 3-2: let n be 2;
step 3-3: according to the trigger time tau of the nth section of power frequency voltage signal acquired by the power frequency signal acquisition cardnTrigger time error t of discharge signal acquisition card and power frequency signal acquisition card1-τ1Calculating the matching trigger time t of the discharge signal acquisition card corresponding to the nth section of power frequency voltage signaln′＝τn-τ1+t1；
Step 3-4: collected by the search discharge signal collecting cardFinding out the actual trigger time tmAnd matching the trigger time tnThe nearest section of partial discharge signal is used as a partial discharge signal matched with the nth section of power frequency voltage signal;
step 3-5: and N is accumulated, the step 3-3 is returned, and if the matching process is completed when N is equal to N, the accumulation of N is not continued.
However, since the triggering of the acquisition cards 1 and 2 is asynchronous, if the acquisition card 2 is in the off state when the acquisition card 1 is triggered, the signal recorded on the acquisition card 1 will not be reflected in the acquisition card 2. When the discharge signal has strong periodicity and the pulse repetition rate is low, if only the pulse corresponding to the acquisition card 2 in the acquisition card 1 is extracted, a large amount of effective information will be lost, and a correct experimental result cannot be obtained. For this reason, signals recorded in the acquisition card 1, but not recorded in the acquisition card 2, cannot be simply discarded. In practical application, because the extinguishing times of the two acquisition cards are basically the same, the situation that two pulses are not captured by the acquisition card 2 continuously does not exist, namely, if the signal f on the acquisition card 1 isnIf not recorded by the acquisition card 2, its previous signal fn-1Must be recorded by the acquisition card 2. Using fn-1In combination with the pulse delay between the two signals, the signal f is obtainednThe phase information of (1). The method specifically comprises the following steps: and for the section I partial discharge signal which is not matched with the corresponding power frequency voltage signal, obtaining the phase of the power frequency voltage signal corresponding to the section I partial discharge signal according to the phase of the power frequency voltage signal corresponding to the section I-1 partial discharge signal and the trigger time delay of the section I-1 partial discharge signal and the section I partial discharge signal.
In order to verify the effectiveness of the method, pulse excitation measurement is performed on sparse discharge with a discharge phase within the range of 180-200 °, and the phase distribution is calculated by using an asynchronous method and an equal period method respectively, and the obtained result is shown in fig. 5. It can be seen from the figure that, due to the fluctuation of the power frequency signal period, the discharge phase obtained by the equal period calculation method has larger fluctuation, and due to the low discharge repetition rate, the cumulative effect of errors is more obvious, and the fluctuation range of the discharge phase reaches half of the power frequency period. The discharge phase obtained by using the asynchronous measurement method is concentrated in the range of 180-200 degrees and is consistent with the real phase distribution. Therefore, the method can be used for efficiently measuring the sparse discharge signal by using an asynchronous measurement method and combining pulse excitation measurement, and accurately obtaining the phase distribution information of the sparse discharge signal, thereby providing a new thought for characteristic research of the discharge and field type identification.
In summary, the function of the partial discharge signal collecting device of the present invention in the whole partial discharge live detection system is shown in fig. 6. Signals sensed by the partial discharge sensor are transmitted to the partial discharge acquisition device through a cable and are connected to the acquisition card 1; the power frequency voltage signal is collected by a power frequency voltage measuring unit, and the measuring result is transmitted to the collecting card 2 through a cable; the acquisition results of the two acquisition cards are collected by the signal concentrator and then transmitted to the portable signal processing unit for subsequent signal processing and mode identification. In practical application, the acquisition device and the signal processing device can be combined to form a portable partial discharge acquisition analyzer, so that the partial discharge signal can be acquired and analyzed in real time, a preliminary analysis result is given, and the purpose of high-efficiency charged detection is achieved.
The beneficial effect of this scheme lies in:
(1) effectively improving the capture efficiency of the dual-distribution electric pulse. The traditional partial discharge signal acquisition method using time as a target has poor acquisition effect on accidental signals, and is easy to be regarded as interference signals and ignored. The pulse excitation method provided by the invention takes partial discharge pulses as a measurement target, can effectively record even discharge with low repetition rate, and provides favorable conditions for early screening and elimination of defects;
(2) high resolution and long-time sampling of the partial discharge signal can be realized simultaneously. In the continuous sampling method, because the acquisition card still records signals within the interval time between two pulses, information redundancy and waste of storage space are caused, and the method is limited by the storage space of the acquisition card, and high resolution and long-time sampling of the signals can not be realized at the same time. The pulse excitation method provided by the invention records effective pulses when collecting partial discharge signals, and the collection card is in a standby state during the pulse interval, so that the storage space can be utilized to the maximum extent, thereby realizing coexistence of high resolution and long sampling time, and having important significance for measurement of partial discharge signals, especially occasional signals;
(3) and the reliability of the measuring result is improved by combining with the power frequency voltage waveform. The waveform of the external construction frequency voltage of the power equipment cannot be obtained in the traditional partial discharge live measurement, and the power frequency phase corresponding to the partial discharge pulse generation time cannot be determined. The invention utilizes the power frequency voltage measuring device to obtain the waveform of the applied voltage, the waveform is accessed into the partial discharge signal acquisition system, and the method of asynchronous measurement by using the double acquisition card solves the problem of simultaneous acquisition of the low sampling rate power frequency signal and the high sampling rate partial discharge signal, effectively obtains the power frequency phase information of the partial discharge of the equipment, and provides favorable evidence for the subsequent partial discharge type identification.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (9)
1. The utility model provides a partial discharge signal collection system for gather the partial discharge signal of equipment under test, its characterized in that: the partial discharge signal acquisition device comprises a discharge signal acquisition card with a storage space, and the discharge signal acquisition card acquires a partial discharge signal of the equipment to be tested by adopting a pulse excitation measurement method aiming at the discharge signal;
the pulse excitation measuring method for the discharge signal comprises the following steps:
step 1-1: estimating the discharge pulse duration T of partial discharge of the device to be tested according to the device to be tested, setting the sampling rate S required for collecting the partial discharge signal of the device to be tested, and calculating and recording the size of a storage space required by each discharge pulse according to the discharge pulse duration T and the sampling rate S;
step 1-2: averagely dividing a storage space carried by the discharge signal acquisition card into j pulse storage spaces according to the size of a storage space required by each discharge pulse, wherein the kth pulse storage space is used for correspondingly recording the kth partial discharge signal of the tested equipment, k and j are positive integers, j is more than or equal to 2, and j is more than or equal to k;
step 1-3: setting a trigger threshold value of the discharge signal acquisition card, and starting the discharge signal acquisition card;
step 1-4: when the discharge pulse acquisition card detects that the partial discharge signal of the tested equipment reaches the set trigger threshold, the discharge pulse acquisition card is triggered and starts to acquire the waveform of the partial discharge signal, the acquisition is finished until the acquisition duration reaches the discharge pulse duration T, and the acquired partial discharge signals are stored in a corresponding pulse storage space in sequence;
step 1-5: and if the storage space of the discharge signal acquisition card is not used up, returning to the step 1-4, and if the storage space of the discharge signal acquisition card is used up, stopping acquisition.
2. The partial discharge signal acquisition apparatus according to claim 1, wherein: the partial discharge signal acquisition device also comprises a power frequency signal acquisition card with a storage space, the power frequency signal acquisition card acquires a power frequency voltage signal of the tested equipment by adopting a pulse excitation measurement method aiming at the power frequency signal, and the power frequency signal acquisition card is connected with the discharge pulse acquisition card;
the pulse excitation measurement method for the power frequency signal comprises the following steps:
step 2-1: averagely dividing a storage space carried by the power frequency signal acquisition card into j power frequency storage spaces, wherein the sampling time T' corresponding to each power frequency storage space is longer than the discharge pulse duration time T, and the kth pulse storage space is used for correspondingly recording the kth section of power frequency voltage signals of the tested equipment;
step 2-2: setting the discharge signal acquisition card to output a power frequency acquisition trigger signal for triggering the power frequency signal acquisition card when the discharge signal acquisition card is triggered each time, and starting the power frequency signal acquisition card;
step 2-3: when the power frequency signal acquisition card detects the power frequency acquisition trigger signal, starting to acquire the waveform of the power frequency voltage signal, ending acquisition until the acquisition duration reaches the sampling duration T', and sequentially storing the acquired power frequency voltage signal and the corresponding power frequency acquisition trigger signal into a corresponding power frequency storage space;
step 2-4: and returning to the step 2-3 if the storage space in the power frequency signal acquisition card is not used up, and stopping acquisition if the storage space in the power frequency signal acquisition card is used up.
3. The partial discharge signal acquisition apparatus according to claim 2, wherein: and the sampling rate S' required for acquiring the power frequency voltage signal corresponding to each power frequency storage space is lower than the sampling rate S required for acquiring the partial discharge signal of the tested equipment.
4. The partial discharge signal acquisition apparatus according to claim 2, wherein: the partial discharge signal acquisition device further comprises a signal concentrator which is respectively connected with the discharge signal acquisition card and the power frequency signal acquisition card, and the signal concentrator is used for summarizing the partial discharge signals acquired by the discharge signal acquisition card, the power frequency voltage signals acquired by the power frequency signal acquisition card and the corresponding power frequency acquisition trigger signals and then outputting the summarized signals.
5. The partial discharge signal acquisition apparatus according to claim 1, wherein: the discharge signal acquisition card is connected with the partial discharge sensor.
6. The partial discharge signal acquisition apparatus according to claim 2, wherein: and the power frequency signal acquisition card is connected with the power frequency voltage waveform measuring unit.
7. The utility model provides a partial discharge gathers analysis appearance for gather and analysis the partial discharge signal of equipment under test, its characterized in that: the partial discharge acquisition analyzer comprises the partial discharge signal acquisition device as claimed in claim 2, 3, 4 or 5, and a signal processing unit connected with the partial discharge signal acquisition device;
the signal processing unit is used for matching the partial discharge signal acquired by the discharge signal acquisition card with the power frequency voltage signal acquired by the power frequency signal acquisition card and analyzing the phase of the power frequency voltage signal corresponding to the partial discharge signal acquired by the discharge signal acquisition card according to the matching result.
8. The partial discharge acquisition analyzer of claim 7, wherein: the method for matching the partial discharge signal acquired by the discharge signal acquisition card and the power frequency voltage signal acquired by the power frequency signal acquisition card by the signal processing unit comprises the following steps:
step 3-1: according to the triggering time t of the 1 st section of partial discharge signal acquired by the discharge signal acquisition card1And the triggering time tau of the 1 st section of power frequency voltage signal acquired by the power frequency signal acquisition card1Calculating the trigger time error t of the discharge signal acquisition card and the power frequency signal acquisition card1-τ1；
Step 3-2: let n be 2;
step 3-3: according to the trigger time tau of the nth section of power frequency voltage signal acquired by the power frequency signal acquisition cardnTrigger time error t of the discharge signal acquisition card and the power frequency signal acquisition card1-τ1And calculating the matching trigger time t 'of the discharge signal acquisition card corresponding to the nth section of power frequency voltage signal'n＝τn-τ1+t1；
Step 3-4: searching each section of partial discharge signal acquired by the discharge signal acquisition card to find the actualTime of triggering tmAnd the matching trigger time t'nThe closest section of partial discharge signal is used as a partial discharge signal matched with the nth section of power frequency voltage signal;
step 3-5: n are accumulated and the step 3-3 is returned.
9. The partial discharge acquisition analyzer of claim 8, wherein: and for the I section of the partial discharge signal which is not matched with the corresponding power frequency voltage signal, obtaining the phase of the power frequency voltage signal corresponding to the I section of the partial discharge signal according to the phase of the power frequency voltage signal corresponding to the I-1 section of the partial discharge signal and the trigger time delay of the I-1 section of the partial discharge signal and the I section of the partial discharge signal.
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