RU2015119649A

RU2015119649A - METHOD AND DEVICE FOR DETERMINING THE LOCATION OF A SINGLE-PHASE EARTH CIRCUIT IN THE DISTRIBUTION NETWORK BASED ON THE WAVELET TRANSFORM OF TRANSITION SIGNALS

Info

Publication number: RU2015119649A
Application number: RU2015119649A
Authority: RU
Inventors: Цзинсюй МУ; Цзэнпин ВАН; Иннань ВАН; Цинци ЧЖАО; Чжэн ЦИ; Кунья ГО; Тао ЧЖЭН
Original assignee: Стейт Грид Корпорейшн Оф Чайна; Стейт Грид Ляонин Электрик Пауэр Ко., Лтд. Шэньян Пауэр Компани; Норт Чайна Электрик Пауэр Юниверсити
Priority date: 2012-12-10
Filing date: 2013-11-08
Publication date: 2017-01-16
Also published as: WO2014089899A1; CN102944817A; CN102944817B; RU2632989C2

Claims

1. A method for determining the location of a single-phase earth fault section in a distribution network based on a wavelet transform of a transition signal, comprising the steps of:

(1) detect in real time the zero sequence currents created artificially in the secondary circuit of the current transformer, in numerous locations of power lines using the terminals installed on them;

(2) they capture transient signals of the zero sequence current, which are ahead and delayed by 2 periods from the preset initial value immediately after the zero sequence current detected by any terminal exceeds the initial value;

(3) perform the wavelet transform on the transient signals of the zero sequence current of four periods based on the Mall algorithm, in which the transient signals of the zero sequence current are decomposed into the third scale to obtain the maximum modulus M _{j, k} of detail coefficients at various scales, where j is the interlinear scale index; k are the various maximum points of the module on the scale j; using the maximum modulus of the coefficients M _1.1 and M _{2.1 of} detail in the first and second scales, write down the data of these two points and then select the point with the larger module by comparison, while the point in time at the selected point is the damage time T ₀ ;

(4) choose T ₀ as the starting point for integration and 10 ms as the integration interval, integrate the approximation component of the transition signals of the zero-sequence current on the first scale, and then transmit the integrated value to the base station;

(5) comparing the symbols of the integrated values downloaded from the individual terminals, and then evaluating them in accordance with the following various situations:

i) if the symbols of the integrated value downloaded from all terminals are the same, damage occurs on other power lines without an installed terminal on the same bus;

ii) if the symbols of the integrated values downloaded from one or more terminals in the line do not correspond to the symbols from other terminals of the power lines and the number of one or more terminals is less than the number of other terminals, damage occurs in the sections of the power line in which said one or several terminals; mark sections of the power line as sections of the power line with possible damage and conduct a sequential search, starting from the terminal closest to the bus, in sections of the power line with possible damage until two adjacent terminals with different symbols of integrated values are detected, then determine the damage that occurred in the power line section between two adjacent terminals;

iii) if the search result in step ii) shows that the symbols of the integrated values downloaded from all terminals on the power lines with possible damage are consistent, then it is determined that the damage occurred down the terminal on the power line with the damage that is farthest from the bus, that is, it is located in the power line section between the most distant terminal and the load.

2. A device for determining the location of a single-phase earth fault section in a distribution network using the method of claim 1, wherein the device comprises two parts: a main station and terminals, where:

the terminals are installed on a tower support of an overhead power transmission line or inside a cable network cabinet with a ring organization and are connected to the main station via fiber-optic communication or mobile communication, receive phase current signals from the secondary side CT in the distribution circuit at their inputs and generate phase current signals, synthesized

so as to obtain zero sequence current signals;

the main station is installed in the premises of a substation or control center that receives signals transmitted by terminals.

3. The device according to claim 2, in which the terminals include a series-connected current transducer, an A / D conversion module, a CPU module, a fiber optic communication module, and a mobile communication module; and the terminals perform the wavelet transform on the transient signal of the zero sequence current and download the analysis results to the base station.

4. The device according to claim 2, in which the main station is an industrial control computer and includes a fiber optic communication module and a mobile communication module receiving data transmitted by terminals; and the main station compares the sign of zero sequence current damage from the individual terminals and determines the damaged section after calculation and displays it to the operator.