Overview

In China's 3~35kV power supply system, most of them are neutral point non-grounding systems, this system can still operate with faults when single-phase grounding occurs, which greatly reduces the operating cost and improves the reliability of the power supply system, but this power supply mode is easy to produce arc grounding overvoltage and interphase short circuit when the single-phase grounding current is large, which causes harm to the power supply equipment. The previous solution was to install an arc suppression coil at the neutral point to compensate the capacitive current to suppress the probability of arc flash occurrence at the fault point. Obviously, the purpose of this method is to eliminate the arc light, but due to the many characteristics of the arc suppression coil itself, it is difficult to effectively compensate the capacitance current, especially the harm caused by the high-frequency component part to the power supply equipment can not be overcome. Intelligent arc suppression device, when the arc is grounded, the device grounds the fault phase through a set of vacuum contactors that can be controlled by phase splitting, so as to achieve the purpose of completely eliminating the arc light.

Product Model Description

Use Environment

1. During normal operation, the microcomputer controller constantly detects the voltage signal provided by PT, once the system is disconnected, single-phase metal grounding or single-phase arc grounding, the auxiliary secondary open triangle voltage immediately turns from low level to high level, the microcomputer controller starts, and according to the change of PT secondary voltage, judge the fault type and difference.

2. If it is a PT single-phase disconnection fault, the device outputs a switching contact signal, and at the same time, the data can be remotely transmitted through the RS485 (or RS232) interface and the microcomputer monitoring system.

3. If it is a single-phase metallic grounding fault, the device outputs a switching contact signal, and can also send an action command to the vacuum contactor by the microcomputer controller according to the user's requirements, and at the same time, the data can be transmitted remotely through the RS485 (or RS232) interface and the microcomputer monitoring system.

4. If it is a single-phase arc grounding fault, the microcomputer controller will send an action command to the vacuum contactor, so that its rapid action will convert the unstable arc grounding into a stable metallic grounding. The device outputs a switching contact signal, and at the same time, it can realize remote data transmission through RS485 (or RS232) interface and microcomputer monitoring system.

The Basic Functions and Features of the Device

1. It can limit the atmospheric overvoltage and operating overvoltage of the system to a lower voltage level, and ensure the insulation safety of the power grid and electrical equipment.

2. The device has a fast action speed, which can operate within 30ms~40ms, which can quickly eliminate intermittent arc light and stable arc grounding faults, suppress arc grounding overvoltage, prevent further expansion of accidents, and reduce the accident trip rate of the line.

3. It can quickly and effectively eliminate the resonant overvoltage of the system, prevent the long-term resonant overvoltage from damaging the system insulation, and prevent the damage of the resonant overvoltage to the lightning arrester and small inductive load installed in the power grid.

4. After the device is operated, the capacitor current of 200A is allowed to pass continuously for at least 2 hours, and the user can deal with the fault line after completing the reverse operation of transferring the load.

5. It is of great significance to be able to accurately find single-phase grounding fault lines to prevent the further expansion of accidents and reduce the workload of operation and maintenance personnel.

6. From the working principle of the device, it can be seen that the mechanism of limiting the overvoltage has nothing to do with the size of the capacitance current of the power grid to the ground, so its protection performance does not change with the change of the operation mode of the power grid, and the large and small power grids can be used, and the expansion of the power grid has no impact.

7. The voltage transformer in this device can provide the voltage signal of the system to the metering instrument and relay protection devices, which can replace the conventional PT cabinet.

8. It can measure the single-phase grounding capacitance current of the system.

9. The device equipment is simple, small in size, easy to install and debug, that is, it is suitable for substation, and it is also suitable for the high-voltage plant power system of power plant, and it is suitable for both new station and old power station transformation.

10. Cost-effective, compared with the arc suppression coil system, the performance-to-price ratio is very high.

The main components of the device and their functions

1. Combined overvoltage protector TBP composed of large-capacity ZNO nonlinear components

TBP is a high energy capacitance zinc oxide overvoltage protector that has the following advantages compared to general zinc oxide arresters (MOA):

(1) The TBP combined overvoltage protector adopts the structure of a combination of ZNO nonlinear resistance and discharge gap with high energy capacitance, and solves the problem of charge rate and power frequency aging of the protector due to the cooperation of the gap element and the ZNO valve.

(2) The impact coefficient of TBP combined overvoltage protector is 1, and the discharge voltage value under various voltage waveforms is equal, which is not affected by overvoltage waveforms, and the overvoltage protection value is accurate and the protection performance is excellent.

(3) The TBP combined overvoltage protector adopts the four-star connection method, which can greatly reduce the phase-to-phase overvoltage, and reduce the phase-to-phase overvoltage by 60-70% compared with the conventional lightning arrester, and greatly improve the protection reliability.

TBP combined overvoltage protector is a device in this device to limit all kinds of overvoltage, mainly used to limit atmospheric overvoltage and operating overvoltage.

2. High Voltage Vacuum Contactor with Split Phase Control (KA-KC)

This is a kind of high-pressure vacuum AC contactor, which is divided into three phases, one end of each phase is connected to the busbar and the other end is grounded. During normal operation, the vacuum switch is in a disconnected state, controlled by the microcomputer controller and acts, and the phases are locked, and when one of the phases is closed so that the phase bus is grounded, any phase in the other two phases will not be closed.

3. Multi-function Microcomputer Controller WZK (Core Technology)

The multi-function microcomputer controller is the core component of the device, which takes the PIC microcomputer with high anti-interference ability as the core processor, and the core processor is composed of two single-chip microcomputers, and the fault processing speed is fast.

It mainly has the following functions and features:

(1) High degree of automation. The functions of the microcomputer controller are all automatic, without manual operation, and the maintenance and operation are simple.

(2) Good anti-interference performance and high reliability. The microcomputer controller adopts secondary power supply technology, which can resist all kinds of electromagnetic interference, and the interfaces are optical/electrical isolated, which can eliminate the interference of the power supply and the primary system to the controller, and the controller is also set up with a Watchdog self-reset circuit, which can realize the automatic reset of the device and avoid various electromagnetic interference from the outside world.

(3) Perfect protection function. Because the microcomputer controller uses dual processors as the processing unit, it can complete the comprehensive control of arc suppression, detuning and line selection at the same time, and the speed is very fast. And the device can complete the stack voltage transformer high-voltage insurance fuse alarm and voltage transformer secondary voltage signal circuit fault alarm function.

(4) Voltage measurement function. The microcomputer controller measures the voltage of the system and displays it in digital form.

(5) Data remote transmission function. The microcomputer controller is equipped with RS485/232 communication interface, which can report the real-time fault information of the system and the working condition of the device to the control center.

(6) Fault record query function. The microcomputer controller has a memory, which can save the fault information of the system (including fault type, failure time, etc.) for a long time, and the user can query the fault record of the system according to his needs.

(7) Accurate line selection function. WZK microcomputer controller is designed with a line selection module, which can complete the single-phase grounding line selection of multiple outgoing lines (32 channels per bus), and adopts the line selection principle of "incremental mutation method", no matter what nature of grounding occurs in the system, the grounding line can be accurately selected.

4. High Voltage Current Limiting Fuse FU2

The high-voltage current-limiting fuse is a backup protection device for the whole device, which has the following functions:

◇ Large breaking capacity, up to 63KA;

◇ Rapid breaking, breaking time less than 0.3ms;

◇ The current limiting effect is good, which can limit the fault current to less than 1/5 of the short-circuit current and impulse current.

◇ The breaking arc voltage is low, the arc voltage is very low during the fuse breaking process, and when it is used in a system lower than the rated voltage, the arc voltage will be further reduced, so the 12Kv fuse can be used in the 7.2Kv system without the danger of damaging the system insulation.