CN111257690B - Fault diagnosis and positioning method for cross-connection high-voltage cable sheath protector - Google Patents

Abstract

The invention relates to the technical field of high-voltage cable lines, in particular to a fault diagnosis and positioning method for a cross-connection high-voltage cable sheath protector. A fault diagnosis and positioning method for a cross-connection high-voltage cable sheath protector comprises the following steps: step 1: acquiring a current signal of a high-voltage cable sheath; step 2: and diagnosing and positioning the faults of the sheath protector according to a preset standard and a diagnosis method. The invention can effectively utilize the detection current data in the current inspection of the high-voltage cable sheath, and timely find and position the fault of the sheath protector so as to be convenient for subsequently replacing the fault protector, thereby effectively protecting the safety of the high-voltage cable sheath and the insulation and ensuring the safe operation of a cable line. The technical scheme of the invention overcomes the difficulty of data application in protector fault diagnosis in the current protection layer current detection, and solves the problem that the current protection layer protector fault detection depends on manual observation and offline detection.

Description

Fault diagnosis and positioning method for cross-connection high-voltage cable sheath protector

Technical Field

The invention relates to the technical field of high-voltage cable lines, in particular to a fault diagnosis and positioning method for a cross-connection high-voltage cable sheath protector.

Background

The high-voltage cable line is an important component of an urban power grid, and the scale of the high-voltage cable line is rapidly increased due to the requirements of urban beauty and power supply quality. The high-voltage cable is grounded through the metal protective layer to provide a stable zero potential reference point and reliable shielding for the operation of the high-voltage cable. The cross-connection grounding can reduce the current loss of the sheath layer by mutually offsetting induced voltages of the three-phase sheath layer when the circuit is in normal operation, and can also provide a fault current loop for high-voltage cable faults, so that the cross-connection grounding is widely adopted. In order to protect the insulation of the outer sheath of the high-voltage cable and the metal sheath from being damaged by lightning or operation overvoltage, a sheath protector is arranged at the cross interconnection of the high-voltage cables.

The sheath protector has important function of ensuring the safety of the high-voltage cable sheath through the excellent volt-ampere characteristic. However, due to the reasons of the failure of the theoretical calculation of the current and voltage of the sheath, the improper selection of the parameters of the protector and the like, the sheath protector often fails in the actual circuit operation process. Once the protector fails, not only the high-voltage cable sheath is unprotected, but also the current passing through the high-voltage cable sheath may cause high temperature and even fire, which affects the safety of the high-voltage cable line. Therefore, it is very important to determine whether the sheath protector has failed, and to ensure the safe and stable operation of the high-voltage cable. However, at present, the detection means for the fault of the sheath protector is lacking, and the existing state detection means for the high-voltage cable is difficult to accurately diagnose and position the fault of the sheath protector.

At present, two methods are mainly used for diagnosing whether the high-voltage cable sheath protector has faults or not. One is an online patrol mode: when the high-voltage cable inspection personnel inspect the cable line, the cross interconnection box is opened, and whether the appearance of the protective layer protector has traces such as burning, cracking and the like is observed to judge whether the protector breaks down. However, blind areas are prone to exist due to visual observation, and not all of the sheath protectors fail, leaving obvious marks on the surface. Therefore, the inspection method cannot find the fault of the sheath protector completely and effectively. The other mode is an off-line detection mode: when the preventive test is carried out, operation and maintenance personnel detect the insulation resistance of each protector so as to judge whether the protector has defects. However, power failure detection usually wastes time and labor, and consumes a large amount of resources. Both of these methods have difficulty meeting the diagnosis requirement of the operation and maintenance personnel on the fault of the protector.

When the high-voltage cable sheath protector breaks down, the current flowing through the high-voltage cable sheath loop changes, so that the fault of the sheath protector can be represented by the sheath current. The existing high-voltage cable sheath current detection means comprises sheath current on-line monitoring and sheath current live detection in high-voltage cable inspection, but the research on the change of the sheath current after the high-voltage cable sheath protector breaks down is not deep enough at present, and a targeted diagnosis method is not available at present. The current detection means mainly pay attention to the change condition of the amplitude of the sheath current, but when the sheath protector fails, the equivalent impedance is still large, so that the amplitude change range is small, and whether the protector fails or not is difficult to judge only through the amplitude change. Therefore, the current diagnosis method for fault of the protective layer protector is not perfect and needs to be developed.

Disclosure of Invention

The invention provides a fault diagnosis and positioning method for a cross-connection high-voltage cable sheath protector, aiming at overcoming at least one defect in the prior art, and the fault diagnosis and positioning method for the sheath protector is used for realizing the fault diagnosis and positioning of the sheath protector by carrying out live detection on the current of the high-voltage cable sheath and comparing phase differences of different detection currents, thereby solving the problem of difficulty in fault diagnosis and positioning of the conventional sheath protector.

In order to solve the technical problems, the invention adopts the technical scheme that: a fault diagnosis and positioning method for a cross-connection high-voltage cable sheath protector comprises the following steps:

step 1: acquiring a current signal of a high-voltage cable sheath;

step 2: and diagnosing and positioning the faults of the sheath protector according to a preset standard and a diagnosis method.

Further, the step 1 comprises the following steps,

step 1.1: acquiring high-voltage cable sheath current one by one box body phase by using a power frequency current clamp;

step 1.2: after the power frequency current clamp obtains the detection current of each phase, the current signal enters a data acquisition and processing unit;

step 1.3: the collected currents are grouped according to the sheath loops, and the corresponding phase differences are calculated respectively.

Further, in the step 1.1, twelve-phase sheath currents of three-phase sheath currents of four box bodies and each box body are obtained for each cross interconnection large section; detecting sheath current of one or more periods by using a power frequency current clamp, and respectively recording the detection current of twelve detection points as I_m11、I_m12、I_m13、I_m21、I_m22、I_m23、I_m31、I_m32、I_m33、I_m41、I_m42、I_m43(ii) a And the detected current is input into a data acquisition and processing unit for processing.

In the step 1.2, the data acquisition and processing unit has a timing function, compares the input detection current signal with time, and acquires the amplitude and the phase angle difference of each phase current signal.

In the step 1.3, the method specifically comprises,

a) the sheath loop A1-B2-C3 corresponds to the detection current I_m11、I_m21、I_m32、I_m43(ii) a With the detection current I of the first grounded tank_m11As a reference current, calculating the current phase angle difference (I)_m21-I_m11)、∠(I_m32-I_m11)、∠(I_m43-I_m11)；

b) Sheath loop B1-C2-A3Corresponding to the detected current I_m12、I_m22、I_m33、I_m41(ii) a With the detection current I of the first grounded tank_m12As a reference current, calculating the current phase angle difference (I)_m22-I_m12)、∠(I_m33-I_m12)、∠(I_m41-I_m12)；

c) A sheath loop C1-A2-B3 corresponding to the detection current I_m13、I_m23、I_m31、I_m42(ii) a With the detection current I of the first grounded tank_m13As a reference current, calculating the current phase angle difference (I)_m23-I_m13)、∠(I_m31-I_m13)、∠(I_m42-I_m13)。

Further, the step 2 specifically includes:

after being processed by the data acquisition and processing unit, the phase difference between the detection current of the three sheath loops and the reference current in each loop is obtained; the current phase difference is used as the input of a protector fault diagnosis unit for diagnosis;

a current phase angle difference database is preset in the fault diagnosis unit; deriving a corresponding current phase angle difference diagnosis standard from a database according to a cross interconnection line to be diagnosed; the reference standard of the current phase angle difference can be determined by operation experience according to the cable voltage grade, the cable line laying mode, the laying length and the load condition;

comparing the current phase angle difference given by the database with the detection current phase angle difference input by the data acquisition and processing unit by using the current phase angle difference as a standard; when the phase angle difference of the detection current of the protective layer loop exceeds a set standard, judging that a protector of the loop has a fault; and determining the position of the fault protector according to the specific position of the abnormal current in the loop and the phase change condition of the abnormal current.

Compared with the prior art, the beneficial effects are: the invention diagnoses and positions the fault of the sheath protector by detecting the current of the high-voltage cable sheath and calculating the current phase difference. By applying the technical scheme of the invention, the detection current data can be effectively utilized in the current inspection of the high-voltage cable sheath, and the fault of the sheath protector can be found and positioned in time so as to be convenient for the subsequent replacement of the fault protector, thereby effectively protecting the safety of the high-voltage cable sheath and the insulation and ensuring the safe operation of a cable line. The technical scheme of the invention overcomes the difficulty of data application in protector fault diagnosis in the current protection layer current detection, and solves the problem that the current protection layer protector fault detection depends on manual observation and offline detection.

Drawings

FIG. 1 is a flow chart of the diagnostic method of the present invention.

Fig. 2 is a schematic view of a cross-connect high voltage cable according to the present invention.

FIG. 3 is a simplified schematic diagram of a cross-connect circuit according to the present invention.

Fig. 4 is a schematic view of a direct grounding box GB1 of the present invention.

Fig. 5 is a schematic diagram of a cross-connect box CB1 of the present invention.

Fig. 6 is a schematic diagram of a cross-connect box CB2 of the present invention.

Fig. 7 is a schematic view of a direct grounding box GB2 of the present invention.

Detailed Description

The drawings are for illustrative purposes only and are not to be construed as limiting the patent; for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted. The positional relationships depicted in the drawings are for illustrative purposes only and are not to be construed as limiting the present patent.

A fault diagnosis and positioning method for a cross-connection high-voltage cable sheath protector based on sheath current phase difference is mainly shown in a flow chart of figure 1.

A schematic diagram of a cross-linking section of a high voltage cable is shown in fig. 2, and a simplified schematic diagram of the sheath loop is shown in fig. 3. Recording the sheath protector to be diagnosed in the cross-connection box as SVL₁、SVL₂、SVL₃、SVL₄、SVL₅、SVL₆See fig. 5 and 6.

The method specifically comprises the following steps:

(1) obtaining high voltage cable sheath current signal

And acquiring the current of the high-voltage cable sheath one by one box body phase by phase. The power frequency current clamp is utilized to detect the sheath current in one or more periods (the detection current frequency is generally 50Hz, the corresponding time period is 0.02s), and the detection current of the first box body (grounding box) is I_m11、I_m12、I_m13(ii) a The second box (cross-connect box) has a current I_m21、I_m22、I_m23(ii) a The third box (cross-connect box) has a detection current of I_m31、I_m32、I_m33(ii) a The detection current of the fourth box body (direct grounding box) is marked as I_m41、I_m42、I_m43。

The method comprises the steps of taking a certain time point as a time origin, recording the acquisition time of each phase of sheath current in each box body, enabling a power frequency current clamp to obtain each phase of detected current, enabling a current signal of each phase to enter a data acquisition processing unit, calculating and recording a zero crossing point of the current signal, and determining the phase of the current according to the current acquisition time, the current zero crossing point and the time origin. And similarly, acquiring and acquiring the amplitude and phase angle difference of each phase current signal according to the zero-crossing positions of the currents at other positions and the current change period and recording.

Then, grouping the collected currents according to the sheath loops, and calculating the corresponding phase difference:

the sheath loop A1-B2-C3 corresponds to the detection current I_m11、I_m21、I_m32、I_m43. With the detection current I of the first grounded tank_m11As a reference current, calculating the current phase angle difference (I)_m21-I_m11)、∠(I_m32-I_m11)、∠(I_m43-I_m11)。

A sheath loop B1-C2-A3 corresponding to the detection current I_m12、I_m22、I_m33、I_m41. With the detection current I of the first grounded tank_m12As a reference current, calculating the current phase angle difference (I)_m22-I_m12)、∠(I_m33-I_m12)、∠(I_m41-I_m12)。

A sheath loop C1-A2-B3 corresponding to the detection current I_m13、I_m23、I_m31、I_m42. With the detection current I of the first grounded tank_m13As a reference current, calculating the current phase angle difference (I)_m23-I_m13)、∠(I_m31-I_m13)、∠(I_m42-I_m13)。

(2) Fault diagnosis and location of protective layer protector according to preset diagnosis method

A corresponding current phase angle difference diagnostic criterion is derived from the current database. According to the line characteristics and the actual line operation condition, giving a standard value P of the current phase difference₁、P₂₁、P₂₂、P₃₁、P₃₂(P₂₁<P₂₂,P₃₁<P₃₂) As the determination criteria for the phase angle difference of the three currents in each sheath loop.

The specific diagnostic and localization criteria are as follows:

the sheath loop A1-B2-C3 has the following diagnostic criteria:

if (I)_m21-I_m11)<P₁And < I >_m32-I_m11)<P₂₁And < I >_m43-I_m11)<P₃₁", it is diagnosed as" there is no sheath protector fault in sheath loop a1-B2-C3 ";

if (I)_m21-I_m11)>P₁And P is₂₁<∠(I_m32-I_m11)<P₂₂And P is₃₁<∠(I_m43-I_m11)<P₃₂"the SVL1 (i.e. the protector at A1-B2) is in fault" in the sheath loop A1-B2-C3;

if (I)_m21-I_m11)<P₁And P is₂₁<∠(I_m32-I_m11)<P₂₂And P is₃₁<∠(I_m43-I_m11)<P₃₂"the SVL5 (i.e. the protectors at B2-C3) is diagnosed as" failure in sheath loop A1-B2-C3 ";

if (I)_m21-I_m11)>P₁And < I >_m32-I_m11)>P₂₂And < I >_m43-I_m11)>P₃₂"in sheath loop A1-B2-C3, SVL1 (i.e. protector at A1-B2) and SVL5 (i.e. protector at B2-C3) both failed";

② for the sheath loop B1-C2-A3, the following diagnosis standards are available:

if (I)_m22-I_m12)<P₁And < I >_m33-I_m12)<P₂And < I >_m41-I_m12)<P₃₁", it is diagnosed as" there is no sheath protector fault in sheath loop B1-C2-A3 ";

if (I)_m22-I_m12)>P₁And P is₂₁<∠(I_m33-I_m12)<P₂₂And P is₃₁<∠(I_m41-I_m12)<P₃₂"the SVL2 (i.e. the protectors at B1-C2) in the sheath loop B1-C2-A3 is diagnosed as failure";

if (I)_m22-I_m12)<P₁And P is₂₁<∠(I_m33-I_m12)<P₂₂And P is₃₁<∠(I_m41-I_m12)<P₃₂Then, the diagnosis is that SVL6 (i.e. protector at C2-A3) has a fault in the sheath loop B1-C2-A3;

if (I)_m22-I_m12)>P₁And < I >_m33-I_m12)>P₂₂And < I >_m41-I_m12)>P₃₂"the diagnosis is" failure occurs in both SVL2 (i.e. protectors at positions B1-C2) and SVL6 (i.e. protectors at positions C2-A3) in the sheath circuit B1-C2-A3 ";

③ for the sheath loop C1-a2-B3, the following diagnostic criteria apply:

if (I)_m23-I_m13)<P₁And < I >_m31-I_m13)<P₂And < I >_m42-I_m13)<P₃₁", then, the diagnosis is" sheath loop CNo sheath protector failure in 1-A2-B3 ";

if (I)_m23-I_m13)>P₁And P is₂₁<∠(I_m31-I_m13)<P₂₂And P is₃₁<∠(I_m42-I_m13)<P₃₂"the SVL3 (i.e. the protector at C1-A2) is failed in the sheath loop C1-A2-B3";

if (I)_m23-I_m13)<P₁And P is₂₁<∠(I_m31-I_m13)<P₂₂And P is₃₁<∠(I_m42-I_m13)<P₃₂"the SVL4 (i.e. the protector at A2-B3) is in fault" in the sheath loop C1-A2-B3;

if (I)_m23-I_m13)>P₁And < I >_m31-I_m13)>P₂₂And < I >_m42-I_m13)>P₃₂"in sheath loop C1-a2-B3, both SVL3 (i.e., protector at C1-a 2) and SVL4 (i.e., protector at a 2-B3) failed";

for implementation reference, taking a 220kV parallel high-voltage cable line as an example, according to various factors such as a line laying mode, a laying length, and a load condition, a current phase difference diagnosis standard is determined as follows: p₁＝18°，P₂₁＝18°，P₂₂＝30°，P₃₁＝10°，P₃₂＝22°。

The collected current signals can be diagnosed and positioned for the faults of the sheath protectors of the cross-connection high-voltage cable lines according to the diagnosis method.

In the invention, the fault of the sheath protector is diagnosed by utilizing the current phase angle difference of the high-voltage cable sheath; the detection currents are grouped according to the sheath loops, one current is used as a phase angle reference, and the phase angle difference between the currents at other positions and the reference current is calculated to be used as a diagnosis basis. And the fault position of the protector is positioned by detecting the change condition of the current phase angle difference at different positions in the same sheath loop. The method for determining the sheath current phase difference of each box body of the high-voltage cable, the protector fault diagnosis method and the positioning method based on the detection of the sheath current phase difference are all the points to be protected.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (5)

1. A fault diagnosis and positioning method for a cross-connection high-voltage cable sheath protector is characterized by comprising the following steps:

step 1: acquiring a current signal of a high-voltage cable sheath;

step 2: diagnosing and positioning the faults of the protective layer protector according to a preset standard and a diagnosis method;

the step 1 comprises the following steps,

step 1.1: acquiring high-voltage cable sheath current one by one box body phase by using a power frequency current clamp;

step 1.2: after the power frequency current clamp obtains the detection current of each phase, the current signal enters a data acquisition and processing unit;

step 1.3: the collected currents are grouped according to the sheath loops, and the corresponding phase differences are calculated respectively.

2. The method of claim 1, wherein the fault diagnosis and location method comprises the following steps: in the step 1.1, twelve-phase sheath currents of four box bodies and three-phase sheath currents of each box body are obtained for each cross interconnection large section; detecting sheath current of one or more periods by using a power frequency current clamp, and respectively recording the detection current of twelve detection points as I_m11、I_m12、I_m13、I_m21、I_m22、I_m23、I_m31、I_m32、I_m33、I_m41、I_m42、I_m43(ii) a And the detected current is input into a data acquisition and processing unit for processing.

3. The method of claim 2, wherein the fault diagnosis and location method comprises the following steps: in the step 1.2, the data acquisition and processing unit has a timing function, compares the input detection current signal with time, and acquires the amplitude and the phase angle difference of each phase current signal.

4. The method of claim 3, wherein the fault diagnosis and location method comprises the steps of: in the step 1.3, the method specifically comprises,

a) the sheath loop A1-B2-C3 corresponds to the detection current I_m11、I_m21、I_m32、I_m43(ii) a With the detection current I of the first grounded tank_m11As a reference current, calculating the current phase angle difference (I)_m21-I_m11)、∠(I_m32-I_m11)、∠(I_m43-I_m11)；

b) A sheath loop B1-C2-A3 corresponding to the detection current I_m12、I_m22、I_m33、I_m41(ii) a With the detection current I of the first grounded tank_m12As a reference current, calculating the current phase angle difference (I)_m22-I_m12)、∠(I_m33-I_m12)、∠(I_m41-I_m12)；

c) A sheath loop C1-A2-B3 corresponding to the detection current I_m13、I_m23、I_m31、I_m42(ii) a With the detection current I of the first grounded tank_m13As a reference current, calculating the current phase angle difference (I)_m23-I_m13)、∠(I_m31-I_m13)、∠(I_m42-I_m13)。

5. The method for diagnosing and locating the faults of the sheath protectors of the cross-interconnected high-voltage cables as claimed in claim 4, wherein the step 2 specifically comprises:

after being processed by the data acquisition and processing unit, the phase difference between the detection current of the three sheath loops and the reference current in each loop is obtained; the current phase difference is used as the input of a protector fault diagnosis unit for diagnosis;

a current phase angle difference database is preset in the fault diagnosis unit; deriving a corresponding current phase angle difference diagnosis standard from a database according to a cross interconnection line to be diagnosed; the reference standard of the current phase angle difference can be determined by operation experience according to the cable voltage grade, the cable line laying mode, the laying length and the load condition;

comparing the current phase angle difference given by the database with the detection current phase angle difference input by the data acquisition and processing unit by using the current phase angle difference as a standard; when the phase angle difference of the detection current of the protective layer loop exceeds a set standard, judging that a protector of the loop has a fault; and determining the position of the fault protector according to the specific position of the abnormal current in the loop and the phase change condition of the abnormal current.

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