CN-121995267-A - Transformer short-circuit fault identification method and system

CN121995267ACN 121995267 ACN121995267 ACN 121995267ACN-121995267-A

Abstract

A transformer short-circuit fault identification method and system comprises the steps of establishing a field-circuit coupling model of a distribution transformer, obtaining state quantities of the distribution transformer when single-phase short circuits occur at different positions of a low-voltage winding according to the field-circuit coupling model simulation, calculating the maximum change rate of the state quantities when the single-phase short circuits occur at different positions, selecting an optimal state quantity according to the maximum change rate of all the state quantities when the single-phase single-turn short circuits occur at different positions, obtaining the maximum change rate of the optimal state quantity of the distribution transformer under different insulation resistances and different short-circuit turns according to the field-circuit coupling model simulation, obtaining a first change rate threshold value and a second change rate threshold value, and judging whether the distribution transformer has faults or not and the fault is identical according to the optimal state quantity obtained in real time and the first change rate threshold value and the second change rate threshold value when the distribution transformer actually operates.

Inventors

ZHAO ZIJIAN
WANG NAN
HAN JINGWEI
WANG HAIXIN
Bai Qinyu
ZHENG FEI
YANG JUNYOU
ZHAO CHUNFANG
FENG JIAWEI
WANG YIJIA
WANG SHIJI
YUAN JINGWEI
MA YIMING
CUI NAN
YU HAICHUAN
LI CHANGMING
YANG SONGHAN
GUO TIE
SONG YUNDONG

Assignees

国网辽宁省电力有限公司电力科学研究院
沈阳工业大学

Dates

Publication Date: 20260508
Application Date: 20260119

Claims (10)

1. A method for identifying a short-circuit fault of a transformer, comprising: Constructing a three-dimensional geometric model and a short-circuit equivalent circuit of the distribution transformer, performing field-path coupling on the three-dimensional geometric model and the short-circuit equivalent circuit, and constructing a field-path coupling model; According to the field-path coupling model simulation, obtaining each state quantity of the distribution transformer when the single-phase short circuit occurs at different positions of the low-voltage winding, wherein the state quantity comprises short circuit loop current, space magnetic field intensity, winding power loss and force acting on a turn; Selecting an optimal state quantity according to the maximum change rate of all state quantities when single-phase single-turn short circuits occur at different positions; Obtaining the maximum change rate of the optimal state quantity of the low-voltage winding of the distribution transformer under different insulation resistances and different short-circuit turns according to the field-path coupling model simulation, and obtaining a change rate first threshold value and a change rate second threshold value; When the distribution transformer actually operates, whether the distribution transformer has faults or not and whether the faults are identical are judged according to the optimal state quantity obtained in real time and the first threshold value and the second threshold value of the change rate.
2. The method for identifying a short-circuit fault of a transformer according to claim 1, wherein: the construction of the three-dimensional geometric model of the distribution transformer comprises the following steps: the three-dimensional geometric model of the distribution transformer comprises three-phase models, each phase model consists of a transformer iron core, a low-voltage inner winding, a low-voltage outer winding and a high-voltage winding, and each turn of the low-voltage inner winding and the low-voltage outer winding is numbered.
3. The method for identifying a short-circuit fault of a transformer according to claim 2, wherein: the short circuit equivalent circuit specifically comprises: The short circuit equivalent circuit comprises a high-voltage side equivalent circuit and a low-voltage side equivalent circuit; The high-voltage side equivalent circuit is that one end of the high-voltage side operation phase voltage of each phase is grounded, the other end is connected with one end of the self inductance of the high-voltage winding through the winding resistor of the high-voltage winding of the corresponding phase, and the other ends of the self inductance of the high-voltage windings of all phases are connected; The low-voltage side equivalent circuit is characterized in that for two phases which are not short-circuited, one end of a winding resistor of a low-voltage winding of each phase is connected, and the other end of the winding resistor of the low-voltage winding of each phase is connected with the ground sequentially through self inductance of the low-voltage winding of the corresponding phase and load impedance of the corresponding phase; one end of the first partial winding resistor of the low-voltage winding of the corresponding phase is connected with one end of the winding resistor of the low-voltage winding of the non-short-circuited two phases, the other end of the first partial winding resistor of the low-voltage winding of the corresponding phase is connected with one end of the short-circuit equivalent circuit through the first partial self-inductance of the low-voltage winding of the corresponding phase, and the other end of the short-circuit equivalent circuit is connected with the ground through the second partial self-inductance of the low-voltage winding of the corresponding phase, the second partial winding resistor of the low-voltage winding of the corresponding phase and the load impedance of the corresponding phase in sequence.
4. A method for identifying a short circuit fault in a transformer according to claim 3, wherein: If the short circuit is a single-turn short circuit, the short circuit loop is that the equivalent inductance and the equivalent resistance of the short circuit turn are connected in series to form a series structure, and the series structure is connected with the insulation resistance of the short circuit point in parallel when the single turn short circuit is performed; If the short circuit is a multi-turn short circuit, the short circuit loop is that the equivalent inductance and the equivalent resistance of each short circuit turn are connected in series to form a branch, and after all the branches corresponding to the short circuit turns are connected in parallel, the branch is connected in parallel with an equivalent insulation resistance representing the insulation state of the short circuit point.
5. The method for identifying a short-circuit fault of a transformer according to claim 2, wherein: The optimal state quantity is selected according to the maximum change rate of all state quantities when single-phase single-turn short circuit occurs at different positions, and specifically comprises the following steps: The different positions are each turn of the low-voltage inner winding and each turn of the low-voltage outer winding; For each state quantity, obtaining the maximum change rate of the corresponding state quantity when each turn of the low-voltage winding is in single-turn short circuit to form an inner winding sequence, and obtaining the maximum change rate of the corresponding state quantity when each turn of the low-voltage winding is in single-turn short circuit to form an outer winding sequence, wherein the inner winding sequence and the outer winding sequence are spliced to form a total sequence; Acquiring the maximum value in the total sequence of each state quantity as a sensitivity index of the corresponding state quantity; Calculating the reciprocal of the standard deviation of the total sequence of each state quantity as a stability index of the corresponding state quantity; Respectively calculating the absolute value of the difference between the average value of the inner winding sequence and the average value of the outer winding sequence of each state quantity, and calculating the reciprocal of the absolute value as a distinguishing degree index; And carrying out weighted summation on the sensitivity index, the stability index and the distinguishing degree index according to the set weights to obtain the final evaluation index of the corresponding state quantity, wherein the state quantity with the maximum evaluation index is used as the optimal state quantity.
6. The method for identifying a short-circuit fault of a transformer according to claim 4, wherein: the first threshold value of the change rate and the second threshold value of the change rate are obtained specifically: Setting an insulation degradation critical resistance value and an insulation collapse critical resistance value, wherein the insulation degradation critical resistance value is larger than the insulation collapse critical resistance value; Performing multiple simulation, setting an insulation resistance as an initial value and setting a short-circuit turn number as 1 when the initial simulation is performed, if the value of the current insulation resistance is larger than or equal to an insulation degradation critical resistance value, dividing the insulation resistance when the current simulation is performed by a set attenuation coefficient when the next simulation is performed, and keeping the short-circuit turn number unchanged when the next simulation is performed; obtaining the maximum value of the maximum change rate of the optimal state quantity corresponding to the simulation of all insulation resistance values which are larger than or equal to the insulation degradation critical resistance value as a change rate first threshold; obtaining the maximum value of the maximum change rate of the optimal state quantity corresponding to the simulation of which all the values of the insulation resistance are smaller than the insulation degradation critical resistance as a change rate second threshold; When the number of turns of the short circuit is 1, the insulation resistance is the insulation resistance of the short circuit point when the series structure is short-circuited with a single turn, otherwise, the insulation resistance is the equivalent insulation resistance representing the insulation state of the short circuit point.
7. The method for identifying a short-circuit fault of a transformer according to claim 6, wherein: Judging whether the distribution transformer has faults or not, specifically: Obtaining the current load rate and the optimal state quantity of each phase, obtaining the reference value of the optimal state quantity under the current load rate, calculating the difference between the optimal state quantity of each phase and the reference value divided by the reference value to obtain the real-time change rate of the corresponding phase, judging that the inter-turn insulation is abnormal if at least one phase has the real-time change rate which is larger than or equal to the first change rate threshold and smaller than the second change rate threshold, judging that the inter-turn insulation is short-circuit fault if at least one phase has the real-time change rate which exceeds the second change rate threshold, otherwise, judging that the inter-turn insulation is normal.
8. The method for identifying a short-circuit fault of a transformer according to claim 7, wherein: The obtaining the reference value of the optimal state quantity under the current load rate specifically comprises the following steps: Firstly, establishing a mapping relation between a reference value of each state quantity except for winding power loss and a load rate according to historical data; when the optimal state quantity is winding power loss, the reference value of the optimal state quantity is equal to the square of the current load rate multiplied by the winding load loss of the transformer under rated load plus the no-load loss of the transformer; and when the optimal state quantity is not the winding power loss, acquiring the optimal state quantity of the mapping corresponding to the current load rate.
9. The method for identifying a short-circuit fault of a transformer according to claim 7, wherein: Judging the fault phase, specifically: and calculating and judging that the real-time change rate of each phase at the moment of the inter-turn insulation abnormality or short circuit fault is divided by the total real-time change rate as the duty ratio of the corresponding phase, wherein the total real-time change rate is the sum of the real-time change rates of all phases, if the duty ratio of one phase exceeds a set duty ratio threshold value, the corresponding phase is indicated to be in a fault phase, otherwise, the corresponding phase is regarded as in an abnormal state.
10. A transformer short-circuit fault recognition system based on the method of any one of claims 1-9, comprising a field-path coupling model construction module, a maximum change rate acquisition module, an optimal state quantity selection module, a change rate threshold setting module and a fault recognition module, wherein the system is characterized in that: The field-circuit coupling model construction module is used for constructing a three-dimensional geometric model and a short circuit equivalent circuit of the distribution transformer, carrying out field-circuit coupling on the three-dimensional geometric model and the short circuit equivalent circuit, and constructing a field-circuit coupling model; The maximum change rate acquisition module is used for obtaining each state quantity of the low-voltage winding of the distribution transformer when single-phase short circuit occurs at different positions according to the field-path coupling model simulation, wherein the state quantity comprises short circuit loop current, space magnetic field intensity, winding power loss and force acting on a turn; The optimal state quantity selecting module is used for selecting the optimal state quantity according to the maximum change rate of all state quantities when single-phase single-turn short circuits occur at different positions; The change rate threshold setting module is used for obtaining the maximum change rate of the optimal state quantity under different insulation resistances and different short-circuit turns of the low-voltage winding of the distribution transformer according to the field-circuit coupling model simulation, and obtaining a change rate first threshold and a change rate second threshold; And the fault identification module is used for judging whether the distribution transformer has faults or not and judging the fault phase according to the optimal state quantity and the first threshold value and the second threshold value of the change rate which are obtained in real time when the distribution transformer actually operates.

Description

Transformer short-circuit fault identification method and system Technical Field The invention belongs to the technical field of on-line monitoring and fault diagnosis of power equipment, and particularly relates to a transformer short-circuit fault identification method and system. Background Distribution transformers are key devices in a distribution network, the operational reliability of which is directly related to the quality of the power supply. Winding turn-to-turn short circuit faults are one of the most common internal faults of the transformer, and can account for more than 50% of the internal faults according to statistics. When such faults occur, the current in the shorted turns can reach tens of times of rated values, and huge heat and electrodynamic force are generated, so that dielectric breakdown and equipment accidents are rapidly caused. At present, the detection method for the turn-to-turn short circuit fault of the transformer mainly comprises a direct current resistance test, a short circuit impedance method, a voltage ratio measurement, a sweep frequency short circuit impedance method and the like. However, most of these methods belong to offline or preventive test projects, the transformer is required to be taken out of operation, and real-time online monitoring cannot be realized. In addition, when an inter-turn short circuit occurs in the line, the main loop current of the transformer is slightly changed due to the large impedance of the fault loop, and is usually insufficient to trigger a traditional overcurrent protection device (such as a fuse or an overcurrent relay), so that the fault cannot be timely removed, and serious equipment damage and power supply interruption accidents are evolved. Disclosure of Invention In order to solve the defects in the prior art, the invention provides a transformer short-circuit fault identification method and a system. The invention adopts the following technical scheme. The first aspect of the invention provides a method for identifying a short-circuit fault of a transformer, which comprises the following steps: Constructing a three-dimensional geometric model and a short-circuit equivalent circuit of the distribution transformer, performing field-path coupling on the three-dimensional geometric model and the short-circuit equivalent circuit, and constructing a field-path coupling model; According to the field-path coupling model simulation, obtaining each state quantity of the distribution transformer when the single-phase short circuit occurs at different positions of the low-voltage winding, wherein the state quantity comprises short circuit loop current, space magnetic field intensity, winding power loss and force acting on a turn; Selecting an optimal state quantity according to the maximum change rate of all state quantities when single-phase single-turn short circuits occur at different positions; Obtaining the maximum change rate of the optimal state quantity of the low-voltage winding of the distribution transformer under different insulation resistances and different short-circuit turns according to the field-path coupling model simulation, and obtaining a change rate first threshold value and a change rate second threshold value; When the distribution transformer actually operates, whether the distribution transformer has faults or not and whether the faults are identical are judged according to the optimal state quantity obtained in real time and the first threshold value and the second threshold value of the change rate. Preferably, the construction of the three-dimensional geometric model of the distribution transformer is specifically as follows: the three-dimensional geometric model of the distribution transformer comprises three-phase models, each phase model consists of a transformer iron core, a low-voltage inner winding, a low-voltage outer winding and a high-voltage winding, and each turn of the low-voltage inner winding and the low-voltage outer winding is numbered. Preferably, the short-circuit equivalent circuit specifically comprises: The short circuit equivalent circuit comprises a high-voltage side equivalent circuit and a low-voltage side equivalent circuit; The high-voltage side equivalent circuit is that one end of the high-voltage side operation phase voltage of each phase is grounded, the other end is connected with one end of the self inductance of the high-voltage winding through the winding resistor of the high-voltage winding of the corresponding phase, and the other ends of the self inductance of the high-voltage windings of all phases are connected; The low-voltage side equivalent circuit is characterized in that for two phases which are not short-circuited, one end of a winding resistor of a low-voltage winding of each phase is connected, and the other end of the winding resistor of the low-voltage winding of each phase is connected with the ground sequentially through self inductance of the low-voltage