阅读说明：本技术 一种中性点接地电阻器自动控制装置 (Automatic control device of neutral point grounding resistor ) 是由 叶远波 陈实 王吉文 谢民 王同文 汪胜和 程小平 王薇 项忠华 陈晓东 蔡翔 于 2020-04-21 设计创作，主要内容包括：本发明公开了一种中性点接地电阻器自动控制装置,涉及电力技术领域；本装置接在配电网中性点和大地之间,包括小电阻器、可控硅过压自动投切开关、接触器和控制器,控制器与接触器串联,接触器与可控硅过压自动投切开关并联,并联后的接触器和可控硅过压自动投切开关一端与配电网中性点相连,接触器和可控硅过压自动投切开关的另一端连接于小电阻器,小电阻器的另一端直接接地。本发明在电网正常运行的时候,可控硅不导通,中性点经均压电阻接地,将均压电阻的阻值按高阻接地的方式选取,则此时的电网运行于经高阻接地方式,从而可避免铁磁谐振的发生,并且小电阻接地方式下继电保护灵敏度高,保护算法简单。(The invention discloses an automatic control device of a neutral point grounding resistor, relating to the technical field of electric power; the device is connected between a neutral point of a power distribution network and the ground and comprises a small resistor, a silicon controlled overvoltage automatic switching switch, a contactor and a controller, wherein the controller is connected with the contactor in series, the contactor is connected with the silicon controlled overvoltage automatic switching switch in parallel, one end of the contactor and one end of the silicon controlled overvoltage automatic switching switch which are connected in parallel are connected with the neutral point of the power distribution network, the other ends of the contactor and the silicon controlled overvoltage automatic switching switch are connected with the small resistor, and the other end of the small resistor is directly grounded. When the power grid normally operates, the silicon controlled rectifier is not conducted, the neutral point is grounded through the voltage-sharing resistor, the resistance value of the voltage-sharing resistor is selected in a high-resistance grounding mode, the power grid operates in the high-resistance grounding mode at the moment, ferromagnetic resonance can be avoided, relay protection sensitivity is high in a small-resistance grounding mode, and a protection algorithm is simple.)

1. The utility model provides a neutral point ground resistor automatic control device, includes little resistor, silicon controlled rectifier overvoltage automatic on-off switch, contactor and controller, and the controller is established ties with the contactor, and the contactor is parallelly connected with silicon controlled rectifier overvoltage automatic on-off switch, and contactor and silicon controlled rectifier overvoltage automatic on-off switch one end after parallelly connected link to each other with the distribution network neutral point, and the other end of contactor and silicon controlled rectifier overvoltage automatic on-off switch is connected in little resistor, the other end direct ground connection of little resistor.

2. The automatic control device of the neutral point grounding resistor as claimed in claim 1, wherein the silicon controlled over-voltage automatic switching switch monitors the neutral point voltage in real time through a voltage dependent resistor, switching on when the neutral point voltage exceeds the over-voltage threshold, switching on a small resistor, keeping off when the neutral point voltage does not exceed the over-voltage threshold, monitoring the neutral point voltage in real time by a controller, the contactor is driven to close immediately after the neutral voltage exceeds the overvoltage threshold, the contactor is driven to close when the neutral voltage is lower than the overvoltage threshold but higher than the grounding threshold, keeping the contactor open during the period when the neutral point voltage is lower than the grounding threshold value, wherein the overvoltage threshold value ranges from 100% to 150% of the phase voltage, the value range of the neutral point voltage which is lower than the overvoltage threshold value and higher than the grounding threshold value is 5% -30%, and the delay time is 1-10 seconds.

3. The automatic control device of a neutral point grounding resistor as claimed in claim 2, wherein the automatic control device is provided with neutral point to ground impedances of 10kV system, 20kV system and 35kV system: the 10kV system has an impedance to ground of 600 to 1500 ohms, a 20kV system, an impedance to ground of 1000 to 3000 ohms, a 35kV system, and an impedance to ground of 2000 to 5000 ohms.

4. The automatic control device of the neutral point grounding resistor of claim 3, wherein the thyristor overvoltage automatic switching switch comprises more than two thyristors, a piezoresistor and a resistance-capacitance voltage-sharing circuit, the more than two thyristors are connected in series, a piezoresistor is connected between the gate pole and the anode of each thyristor, and the voltage-sharing value of the piezoresistor is about: the overvoltage threshold/N, the selection of each component parameter in the resistance-capacitance voltage-sharing circuit should satisfy when the silicon controlled rectifier does not conduct, the silicon controlled rectifier overvoltage automatic switching switch is divided into the equivalent impedance of 10kV system, 20kV system and 35kV system: the equivalent impedance range of the silicon controlled overvoltage automatic switching switch of the 10KV system is between 600 ohms and 1500 ohms; the equivalent impedance range of the silicon controlled overvoltage automatic switching switch of the 20KV system is between 1000 ohms and 3000 ohms; the equivalent impedance range of the thyristor overvoltage automatic switching switch of the 35KV system is 2000 ohms to 5000 ohms.

5. The automatic control device of the neutral point grounding resistor as claimed in claim 4, wherein the automatic control device comprises a10 kV315kVA grounding transformer, a10 kV30 ohm 200A10 second stainless steel resistor, a10 kV/100V voltage transformer, a silicon controlled automatic overvoltage switching switch, a controller, a10 kV630A contactor and a10 kV lightning arrester under the 10Kv state.

6. The automatic control device of the neutral point grounding resistor as claimed in claim 5, wherein the controller is provided with a voltage measuring interface and an outgoing interface, the measuring range of the voltage measuring interface is 200V, the precision is 2%, the voltage measuring interface is connected with the secondary winding of a10 kV/100V voltage transformer, and the driving capability of the outgoing interface is AC220V 5A.

7. The automatic control device of the neutral point grounding resistor as claimed in claim 6, wherein the thyristor overvoltage automatic switching switch comprises 16 thyristors, 8 equalizing resistors, 16 piezoresistors and 16 groups of RC absorption loops, wherein the thyristor rated voltage is 2500V, the rated current is 500A, the equalizing resistor resistance is 125O ohm, the rated voltage is AC1000V, the rated power is 8000W, and the piezoresistor voltage is 1300V.

8. The automatic control device of the neutral point grounding resistor as claimed in claim 7, wherein the action logic of the thyristor overvoltage automatic switching switch is that the instantaneous value of the neutral point voltage exceeds 10400V, the voltage dependent resistor is conducted, the thyristor is disconnected at the zero crossing point of the current, the next instantaneous value of the voltage exceeds 10400V, and the thyristor is disconnected when the voltage is lower than 10400V.

9. A neutral grounding resistor automatic control device controller control logic comprising the steps of:

s1: starting a controller;

s2: monitoring the voltage of a neutral point in real time by the whole device;

s3: judging the voltage value of the neutral point voltage;

s4: judging the voltage value of the neutral point voltage again;

s5: closing the driving contactor;

s6: returning to S2.

10. The control logic for the automatic control device of neutral point grounding resistor of claim 9, wherein in S3, when the neutral point voltage is judged to exceed 1200V, the control logic proceeds to S4; when the neutral point voltage is judged to be lower than 1200V, the contactor is kept in an open state, and the operation returns to S1, wherein the S4: when the neutral point voltage is judged to exceed 6800V, the contactor is immediately driven to be closed; when the neutral point voltage is judged to be lower than 6800V, the contactor is driven to close after 3 seconds of delay.

Technical Field

The invention relates to the technical field of electric power, in particular to an automatic control device of a neutral point grounding resistor.

Background

The neutral point grounding mode of the medium-voltage distribution network is closely related to the safety, economy and reliability of the operation of the distribution network, and currently, the following neutral point grounding modes mainly exist in China: the grounding modes of the neutral point ungrounded mode, the neutral point grounded mode through an arc suppression coil and the neutral point grounded mode through a small resistor are different in application occasions and have advantages and disadvantages.

The investment is saved in a neutral point ungrounded mode, the power grid can operate with faults, arc overvoltage is easy to occur on occasions with large capacitance current, ferromagnetic resonance overvoltage is easy to occur on occasions with small capacitance current, insulation breakdown of equipment is caused, major safety accidents are caused, and major economic loss is caused, so that the mode is only suitable for the power grid with small capacitance current and with a coordination eliminating means; the neutral point can reduce grounding residual current in a mode of grounding through an arc suppression coil, effectively suppress arc light overvoltage and ferromagnetic resonance overvoltage, can be suitable for occasions with large capacitance current, but also has the problems of difficult grounding and line selection and insufficient compensation capacity along with the development of a power grid; neutral point can effectively restrain the power grid overvoltage through a small resistance grounding mode, and the zero sequence overcurrent protection can remove faults, but the relay protection equipment needs to remove faults immediately due to large grounding fault current, so that a plurality of instantaneous grounding faults can also cause tripping, and the power supply reliability of the power grid is greatly reduced.

Disclosure of Invention

The invention aims to solve the defects in the prior art and provides an automatic control device of a neutral point grounding resistor.

In order to achieve the purpose, the invention adopts the following technical scheme:

the utility model provides a neutral point ground resistor automatic control device, includes little resistor, silicon controlled rectifier overvoltage automatic on-off switch, contactor and controller, and the controller is established ties with the contactor, and the contactor is parallelly connected with silicon controlled rectifier overvoltage automatic on-off switch, and contactor and silicon controlled rectifier overvoltage automatic on-off switch one end after parallelly connected link to each other with the distribution network neutral point, and the other end of contactor and silicon controlled rectifier overvoltage automatic on-off switch is connected in little resistor, the other end direct ground connection of little resistor.

Preferably: the silicon controlled overvoltage automatic switching switch monitors neutral point voltage in real time through a voltage dependent resistor, instantly conducts when the neutral point voltage exceeds an overvoltage threshold, puts in a small resistor, keeps non-conducting when the neutral point voltage does not exceed the overvoltage threshold, monitors the neutral point voltage in real time, immediately drives a contactor to be closed when the neutral point voltage exceeds the overvoltage threshold, drives the contactor to be closed when the neutral point voltage is lower than the overvoltage threshold but higher than a grounding threshold and delays, keeps the contactor to be opened when the neutral point voltage is lower than the grounding threshold, the value range of the overvoltage threshold is 100% -150% of phase voltage, the value range of the neutral point voltage lower than the overvoltage threshold but higher than the grounding threshold is 5% -30%, and the delay time is 1-10 seconds.

Preferably: neutral point to ground impedance of the automatic control device 10kV system, 20kV system and 35kV system: the 10kV system has an impedance to ground of 600 to 1500 ohms, a 20kV system, an impedance to ground of 1000 to 3000 ohms, a 35kV system, and an impedance to ground of 2000 to 5000 ohms.

Preferably: the silicon controlled rectifier overvoltage automatic switching switch comprises silicon controlled rectifiers, piezoresistors and a resistance-capacitance voltage-sharing circuit, the number of the silicon controlled rectifiers is more than two, the silicon controlled rectifiers are connected in series, each piezoresistor is connected between the gate pole and the anode of each silicon controlled rectifier, and the voltage-dependent voltage value of each piezoresistor is about: the overvoltage threshold/N, the selection of each element parameter in the resistance-capacitance voltage-sharing circuit should satisfy when the silicon controlled rectifier is not conducted, the silicon controlled rectifier overvoltage automatic switching switch is divided into equivalent impedances of a10 kV system, a 20kV system and a 35kV system: the equivalent impedance range of the silicon controlled overvoltage automatic switching switch of the 10KV system is between 600 ohms and 1500 ohms; the equivalent impedance range of the silicon controlled overvoltage automatic switching switch of the 20KV system is between 1000 ohms and 3000 ohms; the equivalent impedance range of the silicon controlled overvoltage automatic switching switch of the 35KV system is between 2000 ohms and 5000 ohms.

Preferably: the automatic control device comprises a10 kV315kVA grounding transformer, a10 kV30 Euro 200A10 second stainless steel resistor, a10 kV/100V voltage transformer, a silicon controlled overvoltage automatic switching switch, a controller, a10 kV630A contactor and a10 kV lightning arrester under the condition of 10 Kv.

Preferably: the controller is provided with a voltage measurement interface and an outgoing interface, the range of the voltage measurement interface is 200V, the precision is 2%, the voltage measurement interface is connected with a secondary winding of a10 kV/100V voltage transformer, and the driving capability of the outgoing interface is AC220V 5A.

Preferably: the silicon controlled rectifier overvoltage automatic switching switch comprises 16 silicon controlled rectifiers, 8 voltage-sharing resistors, 16 piezoresistors and 16 groups of resistance-capacitance absorption loops, wherein the rated voltage of the silicon controlled rectifiers is 2500V, the rated current is 500A, the resistance value of the voltage-sharing resistors is 125O ohm, the rated voltage is AC1000V, the rated power is 8000W, and the voltage-sharing voltage of the piezoresistors is 1300V.

Preferably: the action logic of the silicon controlled overvoltage automatic switching switch is that the neutral point voltage instantaneous value exceeds 10400V, the voltage dependent resistor is conducted, the silicon controlled rectifier is disconnected at the current zero crossing point, the next time voltage instantaneous value exceeds 10400V, the silicon controlled rectifier is disconnected when the voltage is lower than 10400V.

Preferably: the method comprises the following steps: s1: starting a controller; s2: monitoring the voltage of a neutral point in real time by the whole device; s3: judging the voltage value of the neutral point voltage; s4: judging the voltage value of the neutral point voltage again; s5: closing the driving contactor; s6: returning to S2.

Preferably: in S3, when the neutral point voltage is judged to exceed 1200V, the process proceeds to S4; when the neutral point voltage is judged to be lower than 1200V, the contactor is kept in an open state, and the operation returns to S1, wherein the S4: when the neutral point voltage is judged to exceed 6800V, the contactor is immediately driven to be closed; when the neutral point voltage is judged to be lower than 6800V, the contactor is driven to close after 3 seconds of delay.

The invention has the beneficial effects that:

1. the whole device is connected between a neutral point of a power grid and the ground, the silicon controlled rectifier is not conducted when the power grid normally operates, the neutral point is grounded through the voltage-sharing resistor, the resistance value of the voltage-sharing resistor is selected in a high-resistance grounding mode, and then the power grid operates in the high-resistance grounding mode at the moment, so that ferromagnetic resonance can be avoided.

2. After the grounding occurs, if the grounding is instantaneous, the device does not act, and the tripping caused by the instantaneous grounding is avoided; if the grounding is permanent grounding, a small resistor is thrown through the contactor to cause zero sequence protection to remove the grounding fault; if overvoltage occurs, the controllable silicon is conducted at the moment of overvoltage, and the controller immediately drives the contactor to be closed, so that the overvoltage is effectively inhibited; the relay protection sensitivity is high in a small-resistance grounding mode, and the protection algorithm is simple.

Drawings

Fig. 1 is a simplified structural diagram of a system of an automatic control device of a neutral point grounding resistor according to the present invention;

fig. 2 is a schematic system structure diagram of an automatic control device of a neutral point grounding resistor according to the present invention;

fig. 3 is a schematic structural diagram of a thyristor overvoltage automatic switching switch of the automatic control device of the neutral point grounding resistor provided by the invention;

fig. 4 is a schematic diagram of a10 KV system structure of an automatic control device of a neutral point grounding resistor according to the present invention;

fig. 5 is a schematic structural diagram of a10 KV silicon controlled overvoltage automatic switching switch of the automatic control device of the neutral point grounding resistor provided by the invention;

fig. 6 is a logic flow chart of a controller of an automatic control device of a neutral grounding resistor according to the present invention.

Detailed Description

The technical solution of the present patent will be described in further detail with reference to the following embodiments.

Reference will now be made in detail to embodiments of the present patent, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary only for the purpose of explaining the present patent and are not to be construed as limiting the present patent.

In the description of this patent, it is to be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in the orientations and positional relationships indicated in the drawings for the convenience of describing the patent and for the simplicity of description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are not to be considered limiting of the patent.

In the description of this patent, it is noted that unless otherwise specifically stated or limited, the terms "mounted," "connected," and "disposed" are to be construed broadly and can include, for example, fixedly connected, disposed, detachably connected, disposed, or integrally connected and disposed. The specific meaning of the above terms in this patent may be understood by those of ordinary skill in the art as appropriate.