WO2020181982A1

WO2020181982A1 - Distributed grounding line selection system and method

Info

Publication number: WO2020181982A1
Application number: PCT/CN2020/076424
Authority: WO
Inventors: 侯炜; 石勇; 董凯达; 金震; 陈俊; 顾浩; 许宗光
Original assignee: 南京南瑞继保电气有限公司; 南京南瑞继保工程技术有限公司
Priority date: 2019-03-12
Filing date: 2020-02-24
Publication date: 2020-09-17
Also published as: CN109888747A

Abstract

Disclosed are a distributed grounding line selection system and method. The system comprises a grounding line selection apparatus and zero-sequence current collection apparatuses corresponding to all branches, wherein the grounding line selection apparatus is connected to each zero-sequence current collection apparatus by means of a ring network; the zero-sequence current collection apparatus in each branch is used for collecting a zero-sequence current sampling value and switch quantity information of the branch; and collected data is sent to the grounding line selection apparatus by means of the ring network, and a grounding line selection function is completed by means of the grounding line selection apparatus. By means of this technical solution, the problem of the wiring of the present small-current grounding line selection apparatus being complex can be solved, a current is collected by means of communication, and the difficult problem of a high sampling rate transmission being required by a grounding line selection apparatus is solved by means of a new transmission mode.

Description

Distributed grounding line selection system and method

Technical field

The invention belongs to the field of power system relay protection, and particularly relates to a system and method for single-phase grounding fault line selection in a small current grounding system.

Background technique

In the 3kV～66kV low current grounding system, single-phase grounding is a common type of fault. When single-phase grounding occurs in a low-current grounding system, the fault-phase-to-ground voltage decreases, and the non-fault phase-to-ground voltage increases, and the line voltage is still symmetrical. In this state, because the grounding current is small, in order to ensure the reliability of power supply, it is allowed to run 1~ 2 hours. However, due to the arc overvoltage of the non-fault phase, it is easy to cause the breakdown of the weak part of the insulation, the saturation of the voltage transformer core, the system overvoltage, and the arc of the fault phase burns the cable, and is easy to cause personal electric shock accidents. Therefore, after the single-phase grounding It is necessary to isolate the single-phase ground fault of the faulty phase in time to ensure the safe and stable operation of the system and the reliability of power supply.

Existing grounding line selection devices are generally conventional sampling methods. As shown in Figure 1, it is necessary to connect the zero sequence current of one or more sections of busbars to the small current grounding line selection device through cables. It is difficult to connect on-site. For example, there are too many bus intervals, and it may be realized by multiple devices due to the limitation of the sampling loop of the small current grounding line selection. The public information has tried to use the distributed grounding line selection method, but the host and slave RS485 or GOOSE transmission is used between the machines. These methods cannot transmit the zero sequence current with high sampling rate to the line selection device, and the line selection accuracy cannot be guaranteed.

Summary of the invention

The purpose of the present invention is to provide a distributed grounding line selection system and method, which can solve the current problem of complicated wiring of small current grounding line selection devices, adopting communication methods to collect current, and solving the grounding line selection devices through a new transmission method The problem of high sampling rate transmission required.

In order to achieve the above objective, the solution of the present invention is:

A distributed grounding line selection system includes a grounding line selection device and a zero-sequence current acquisition device corresponding to each branch, wherein the grounding line selection device and each zero-sequence current acquisition device are connected through a ring network, and each branch The zero-sequence current acquisition device in the circuit is used to collect the zero-sequence current sampling value and switch information of the branch where it is located. The collected data is sent to the grounding line selection device through the ring network, and the grounding line selection device completes the grounding line selection function.

The zero-sequence current collecting device is used to collect the three-phase current, zero-sequence current, circuit breaker position, and bus voltage of the branch, and send it to the grounding line selection device through the ring network; the zero-sequence current collecting device is set separately or shared branch The existing protection device in the road realizes the protection function of the branch and also has the measurement and control function of the branch.

Each zero-sequence current acquisition device and grounding line selection device has at least two network ports, which are respectively connected to two adjacent devices.

The above-mentioned ring network analog quantity sampling value transmission rate is lower than the zero sequence current sampling rate of each branch zero sequence current acquisition device.

The zero sequence current sampling rate of each branch zero sequence current acquisition device is greater than 6000 points per second.

The switch quantity information of each branch required by the grounding line selection device and the analog quantity are transmitted in the same frame of message.

After the above-mentioned grounding line selection device completes line selection, the trip mode adopted is issued by the ring network, issued by GOOSE, or output by hard contact.

The zero sequence current of each branch is transmitted in both directions through the ring network, and the normal operation of the system will not be affected if a network port or network cable is interrupted.

A distributed grounding line selection method includes the following steps: a grounding line selection device and a zero-sequence current collection device corresponding to each branch are set up, wherein the grounding line selection device and each zero-sequence current collection device pass through a ring network Connected, the zero sequence current acquisition device in each branch is used to collect the zero sequence current sampling value and switch information of the branch where it is located. The collected data is sent to the grounding line selection device through the ring network, and the grounding line selection device completes the grounding selection Line function.

The zero-sequence current of each branch is separately transmitted through the ring network in both directions. If a network port or network cable is interrupted, it will not affect the normal operation of the system.

After adopting the above scheme, the present invention reduces the on-site construction workload of the grounding line selection device and reduces the construction difficulty; for the grounding line selection device, the zero sequence current signal adopts digital input, so there is no need to configure conventional sampling in the grounding line selection device CT, the device volume is significantly reduced, the weight is significantly reduced, and it can be installed on the switch cabinet, saving on-site space.

Description of the drawings

Figure 1 is a schematic diagram of the wiring of a conventional low-current grounding line selection device;

Figure 2 is a schematic diagram of the wiring of the distributed grounding line selection system of the present invention.

detailed description

The technical solutions and beneficial effects of the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 2, the present invention provides a distributed grounding line selection system and method, including a grounding line selection device and a zero-sequence current collection device corresponding to each branch, wherein the grounding line selection device and the bus The zero sequence current acquisition devices of each branch are connected through a ring network. The zero sequence current acquisition devices in each branch are used to collect the zero sequence current sampling value and switch information of the branch where they are located, and the collected data is sent through the ring network For the grounding line selection device, the grounding line selection device completes the grounding line selection function; the zero-sequence current acquisition device can be set separately, or the existing protection device in the branch can be used to realize the function.

Each device (including the zero-sequence current acquisition device and the distributed grounding line selection device) has at least two network ports, which are connected to two adjacent devices in the ring network as shown in Figure 2; in order to improve the ring network Therefore, the transmission rate of the analog quantity sampling value of the ring network can only be maintained at an appropriate value. The transmission rate is lower than the zero sequence current sampling rate of the zero sequence current acquisition device of each branch. Two analog channels jointly transmit a zero sequence current to achieve high sampling rate data transmission.

In order to improve the transmission efficiency, the switching quantity information of each branch required by the grounding line selection device and the analog quantity are transmitted in the same frame of message. The characteristic frequency of a ground fault may be as high as 3000 Hz, so the zero sequence current sampling rate of each branch zero sequence current acquisition device must be greater than 6000 points/sec.

The trip mode of the grounding line selection device after the line selection is completed supports three modes: issued by the ring network, issued by GOOSE, or output by hard contact.

The ring network in the present invention adopts high-reliability seamless redundancy specifications. When a network port or network cable is interrupted, the distributed grounding line selection function will not be affected, and the normal operation of the system is ensured.

The distributed grounding system and method of the present invention solve the problems of complicated wiring of the current low-current grounding device, heavy weight, large volume, and inconvenient switchgear installation, and the object is 3kV-66kV low-current grounding system. As shown in Figure 2, the zero-sequence CT signal of each branch on a busbar does not need to be connected to the grounding line selection device through the cable, but is connected to the integrated protection and monitoring device on the switchgear of this branch. Each integrated protection and monitoring device is at least Equipped with two Ethernet ports, which are respectively connected to two devices of adjacent branches, and form a ring network with the grounding line selection device.

In order to improve the accuracy of the line selection of the grounding line selection device, the zero sequence current sampling rate of each branch required by the device is not less than 9.6k, but the excessively high transmission speed will limit the number of devices in the ring network. Therefore, the device adopts 2.4 K transmission speed for SV data transmission, through the common transmission of 4 channels, to achieve high sampling rate data transmission. The application frame message format is shown in Table 1 below.

Table 1 Application message frame format

Among them, the data format definition of APDU is shown in Table 2:

Table 2 APDU format definition

For example, the zero sequence current is I0, and the 9.6k sampling values per second are respectively I00, I01, I02, I03, I04...I09599; the protection device of each branch in the ring network transmits the externally at a rate of 2.4k times per second. Analog quantity, the sampling count corresponding to this 2.4k is 0～2399. Corresponding to sampling count 0, the values of channel 2 to channel 5 are respectively I00, I01, I02, I03; corresponding to sampling count 1, the values of channel 2 to channel 5 are respectively I04, I05, I06, I07; corresponding to sampling count 2, channel The values of channels 2 to 5 are I08, I09, I010, and I011; and so on, the corresponding sampling count is 2399, and the values of channels 2 to 5 are I09596, I09597, I09598, and I09599, respectively.

The two network ports of each branch protection measurement and control device are respectively connected to the adjacent devices, and the sending data is sent through the two network ports respectively. The ring network adopts high-reliability seamless redundancy specifications for signal transmission, and one port of the forwarding node receives the report. The message immediately forwards the message from another port. When a port of the destination node receives a message, if it is the first time that the two ports of the node receive the frame message, then the frame message is extracted and sent, and at the same time, it continues to be transmitted along the ring network through another port; The port has received this frame message, then the frame message received by this port will be discarded and will not be forwarded at the same time; any network port or communication line is damaged, and the small current received data will not be lost.

The zero-sequence voltage required by the small-current grounding line selection device can be collected in a conventional way. After the zero-sequence voltage is started, the line selection is judged by all the synchronized zero-sequence currents. When the faulty branch is identified, the low-current grounding line selection device can cut off the faulty branch through three methods: ring network distribution, GOOSE distribution or hard contact output.

The above embodiments are only to illustrate the technical ideas of the present invention, and cannot be used to limit the scope of protection of the present invention. Any changes made on the basis of the technical solutions based on the technical ideas proposed by the present invention fall into the protection scope of the present invention. Inside.

Claims

A distributed grounding line selection system, which is characterized in that it includes a grounding line selection device and a zero sequence current acquisition device corresponding to each branch, wherein the grounding line selection device and each zero sequence current acquisition device pass through a ring network Connected, the zero sequence current acquisition device in each branch is used to collect the zero sequence current sampling value and switch information of the branch where it is located. The collected data is sent to the grounding line selection device through the ring network, and the grounding line selection device completes the grounding selection Line function.
The distributed grounding line selection system according to claim 1, wherein the zero-sequence current collecting device is installed separately, or the existing protection device in the branch is shared.
The distributed grounding line selection system according to claim 1, wherein each of the zero sequence current acquisition device and the grounding line selection device has at least two network ports, which are respectively connected to two adjacent devices.
The distributed grounding line selection system according to claim 1, characterized in that: the transmission rate of the analog quantity sampling value of the ring network is lower than the zero sequence current sampling rate of the zero sequence current acquisition device of each branch.
The distributed grounding line selection system according to claim 4, wherein the zero sequence current sampling rate of each branch zero sequence current collecting device is greater than 6000 points/sec.
The distributed grounding line selection system according to claim 1, characterized in that: the switching quantity information of each branch required by the grounding line selection device and the analog quantity are transmitted in the same frame of message.
The distributed grounding line selection system according to claim 1, wherein after the grounding line selection device completes the line selection, the trip mode adopted is issued by the ring network, issued by GOOSE or output by hard contact.
The distributed grounding line selection system according to claim 1, wherein the zero sequence current of each branch is bidirectionally transmitted through the ring network, and the normal operation of the system will not be affected if one network port or network line is interrupted.
A distributed grounding line selection method, which is characterized in that it comprises the following steps: setting a grounding line selection device and a zero sequence current collection device corresponding to each branch, wherein the grounding line selection device and each zero sequence current collection device The zero sequence current acquisition device in each branch is used to collect the zero sequence current sampling value and switch information of the branch where it is located. The collected data is sent to the grounding line selection device through the ring network, and the grounding line selection The device completes the grounding line selection function.
A distributed grounding line selection method according to claim 9, characterized in that: the transmission rate of the analog quantity sampling value of the ring network is lower than the zero sequence current sampling rate of the zero sequence current acquisition device of each branch.
A distributed grounding line selection method according to claim 9, characterized in that: after the grounding line selection device completes line selection, the trip mode adopted is issued by the ring network, issued by GOOSE, or output by hard contact.
A distributed grounding line selection method according to claim 9, characterized in that: the zero sequence current of each branch is separately transmitted through the ring network in both directions, and if a network port or network cable is interrupted, the normal system will not be affected. run.