阅读说明：本技术 一种矿井直流架线用整流电源装置及其架线短路检测方法 (Rectifying power supply device for mine direct-current overhead line and overhead line short circuit detection method thereof ) 是由 盛晨兴 乔力江汉 于 2020-07-07 设计创作，主要内容包括：本发明提供一种矿井直流架线用整流电源装置及其架线短路检测方法,其中矿用整流电源系统直流架线短路检测方法包括通过整流电源架线电流故障识别及输入交流电源电压跌落故障识别,综合对架线短路情况进行判断,具体包括以下步骤：检测整流电源架线电流故障识别算法是否达到架线电流故障预定条件；以及检测整流电源输入交流电源线电压是否跌落至预设的整定阈值；若存在任意检测结果为否,则判断为不符合架线短路的情形,从而不进行保护动作。本发明能有效区分矿井下架线整流电源供电系统的直流远距离架线短路电流和多机车近距离启动电流,实现架线短路故障的可靠检测及保护。(The invention provides a mine direct current overhead line rectifying power supply device and an overhead line short circuit detection method thereof, wherein the mine direct current overhead line short circuit detection method comprises the following steps of comprehensively judging the overhead line short circuit condition through rectifying power supply overhead line current fault identification and input alternating current power supply voltage drop fault identification: detecting whether the identification algorithm of the overhead line current fault of the rectification power supply reaches the predetermined condition of the overhead line current fault; detecting whether the voltage of an input alternating current power line of the rectifying power supply falls to a preset setting threshold value or not; if any detection result is negative, the situation of the short circuit of the overhead line is judged not to be met, and therefore the protection action is not carried out. The invention can effectively distinguish the direct-current long-distance overhead short-circuit current of the mine underground overhead line rectification power supply system from the multi-locomotive short-distance starting current, and realizes the reliable detection and protection of the overhead line short-circuit fault.)

1. A rectification power supply device for a mine direct current overhead line is characterized by comprising:

the three-phase vacuum alternating current contactor is used for controlling the access of a three-phase alternating current power supply;

the three-phase full-bridge rectifying circuit is used for rectifying three-phase alternating current into pulsating direct current, provides a direct-current working power supply for overhead line loads and is connected in series behind the three-phase vacuum alternating-current contactor;

the direct current sensor is used for detecting and outputting working current and is connected in series in the overhead line output loop;

the alternating voltage sensor is used for sensing the input alternating line voltage of the rectification power supply and is connected in parallel with an AB phase of the input three-phase alternating power supply;

the microprocessor is used for controlling the on-off of the three-phase full-bridge rectification circuit, simultaneously collecting the outputs of the direct current sensor and the direct current voltage sensor in real time, calculating the current rise rate and the current increment of the direct current output by the rectification power supply and the direct current voltage output by the rectification power supply in real time, and comprehensively judging the short circuit condition of the overhead line through the overhead line current fault identification of the rectification power supply and the voltage drop fault identification of the input alternating current power supply;

and the upper computer is communicated with the microprocessor circuit.

2. The rectified power supply device for mine dc overhead line of claim 1, wherein said three-phase full-bridge rectifier circuit is a three-phase full-bridge thyristor rectifier circuit, and said dc current sensor is an overhead line dc hall sensor.

3. The rectified power supply device for mine dc overhead line of claim 1, wherein the upper computer is a portable mobile device capable of directly issuing operation commands, and the upper computer has a keyboard for input, a keyboard processing circuit, a display processing circuit and a display.

4. A mine direct-current overhead line short circuit detection method is characterized in that the mine direct-current overhead line short circuit detection method is based on the rectifying power supply device for the mine direct-current overhead line of any one of claims 1 to 3, and comprises the following steps of comprehensively judging the overhead line short circuit condition through rectifying power supply overhead line current fault identification and input alternating-current power supply voltage drop fault identification:

detecting whether the identification algorithm of the overhead line current fault of the rectification power supply reaches the predetermined condition of the overhead line current fault; and

detecting whether the voltage of an input alternating current power line of a rectifying power supply falls to a preset setting threshold value or not;

if any detection result is negative, the situation of the short circuit of the overhead line is judged not to be met, and therefore the protection action is not carried out.

5. The mining direct-current overhead line short circuit detection method according to claim 4, wherein the identification of the overhead line current fault of the rectification power supply comprehensively judges the overhead line short circuit condition based on the overhead line current rise rate and the overhead line current steady-state increment, and specifically comprises the following steps:

detecting whether the current rise rate of the overhead line reaches a preset current rise rate setting value or not; and

detecting whether the steady-state increment of the rack line current reaches a preset setting threshold value or not;

if any detection result is negative, the situation of the short circuit of the overhead line is judged not to be met, and therefore the protection action is not carried out.

6. The mining direct-current overhead line short-circuit detection method according to claim 5, characterized in that the method further judges the overhead line short-circuit condition based on a time when the overhead line current rise rate falls below a preset current rise rate setting value, and specifically comprises:

detecting whether the time for the rise rate of the rack line current to fall below a preset current rise rate setting value is within a preset return delay setting value or not;

if the detection result is negative, the situation of the short circuit of the overhead line is judged not to be met, and therefore the protection action is not carried out.

7. The mining direct current overhead line short circuit detection method according to claim 4 or 5,

and under the conditions that the rise rate of the current of the detection frame line reaches a preset current rise rate setting value, the steady-state increment of the current of the detection frame line reaches a preset setting threshold value, and the time for the rise rate of the current of the detection frame line to fall below the preset current rise rate setting value is within a preset return delay setting value, if the delay time of the steady-state increment of the current of the detection frame line reaches the preset delay setting value, the situation that the current of the detection frame line is in fault is judged to be met.

8. The mining direct-current overhead line short-circuit detection method according to claim 4 or 5, characterized in that under the condition that the detection overhead line current rise rate reaches a preset current rise rate setting value, the detection overhead line current steady-state increment reaches a preset setting threshold value, and the time for the detection overhead line current rise rate to fall below the preset current rise rate setting value is within a preset return delay setting value, if the overhead line voltage of the rectification power supply is within a normal range, the situation that the overhead line is in long-distance short circuit is judged to be met.

9. The method for identifying the rack current fault of the mining rectifying power supply according to claim 4 or 5, wherein under the condition that the detection rack current rise rate reaches a preset current rise rate setting value, the detection rack current steady-state increment reaches a preset setting threshold value, and the time for detecting the rack current rise rate to fall below the preset current rise rate setting value is within a preset return delay setting value, if the rack output voltage of the rectifying power supply is lower than a normal range, the situation that the high current is in accordance with the starting of the rack short-distance locomotive is judged, so that the short-circuit protection operation is not performed.

10. The mining direct-current overhead line short-circuit detection method according to claim 4 or 5, characterized in that when the detection rectification power supply overhead line current fault recognition algorithm reaches the overhead line current fault preset condition, whether the voltage of the input alternating-current power supply line of the rectification power supply falls to a preset setting threshold value when the suspected overhead line current fault occurs is detected, and if the voltage of the input alternating-current power supply line of the rectification power supply falls to the preset setting threshold value, the situation of the overhead line short-circuit is judged to be met, so that protection action is carried out.

Technical Field

The invention relates to the technology of power supply and detection of direct-current overhead lines in mines and the like, in particular to a rectifying power supply device for the direct-current overhead lines in the mines and an overhead line short circuit detection method thereof.

Background

The power supply system of the direct current overhead line electric locomotive is mainly composed of a traction rectifier transformer, a rectifier device, a traction line network and an electric locomotive. Because the underground production environment of the coal mine is severe and has high humidity, power transmission and supply equipment is very easy to be affected with damp and damaged, and the overhead line is easy to be short-circuited due to the fact that a direct-current overhead line is busy in transportation of a locomotive, so that production safety accidents are caused.

For a long time, a direct-current overhead line power supply system used in a coal mine mainly uses a high-current tripping protection function of an alternating-current feed switch to perform short-circuit protection. The large-current tripping protection function needs to preset a tripping setting value, and only when the steady-state value of the overhead line current is greater than the tripping setting value, the short-circuit current can be identified, and further measures such as power-off protection can be taken.

However, this protection is mainly for short-circuit protection at short distances, and is not ideal for short-circuit protection at long distances. In the prior art, in order to detect and identify the short-circuit current as accurately as possible, and in order to avoid mistaking the current (such as starting current) in some cases as the short-circuit current as possible, the tripping setting value is usually set to be large. However, if the trip setting value is set to be too high, when a long-distance overhead line short-circuit current occurs, the steady-state value of the long-distance overhead line short-circuit current is not large due to the presence of the overhead line impedance, and thus there is a case where protection cannot be performed due to the long-distance overhead line short-circuit current being smaller than the set trip setting value. If the tripping setting value is set to be too low, the multi-locomotive short-distance starting current and the multi-locomotive short-circuit current of the long-distance overhead line cannot be distinguished, and some normal currents are mistaken for the short-circuit current.

However, in order to realize long-distance overhead line short-circuit protection in the existing underground coal mine overhead line power supply system, a short-circuit current protection value (namely a book searching tripping setting value) is often set to be low, so that the problems of frequent tripping and the like are caused, and normal production is seriously influenced.

Disclosure of Invention

The invention aims to provide a novel direct-current overhead line short-circuit current identification technology of a rectifying power supply for a mine direct-current overhead line, which can effectively distinguish direct-current long-distance overhead line short-circuit current of a coal mine underground overhead line rectifying power supply system from multi-locomotive short-distance starting current, thereby realizing reliable detection and protection of overhead line short-circuit faults.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

provided is a rectifying power supply device for a mine direct current overhead line, comprising:

the vacuum alternating current contactor is used for controlling the access of a three-phase alternating current power supply;

the three-phase full-bridge rectifying circuit is used for rectifying three-phase alternating current into pulsating direct current, provides a direct-current working power supply for overhead line loads and is connected in series behind the three-phase vacuum alternating-current contactor;

the direct current sensor is used for detecting and outputting working current and is connected in the overhead line output loop in series;

the alternating voltage sensor is used for sensing the input alternating line voltage of the rectifying power supply and is connected in parallel with the AB phase of the input alternating power supply;

the microprocessor is used for controlling the on-off of the three-phase full-bridge rectification circuit, simultaneously collecting the outputs of the direct current sensor and the direct current voltage sensor in real time, calculating the current rise rate and the current increment of the direct current output by the rectification power supply and the direct current voltage output by the rectification power supply in real time, and comprehensively judging the short circuit condition of the overhead line through the overhead line current fault identification of the rectification power supply and the voltage drop fault identification of the input alternating current power supply;

and the upper computer is communicated with the microprocessor circuit.

According to the technical scheme, the three-phase full-bridge rectification circuit is a three-phase full-bridge thyristor rectification circuit.

According to the technical scheme, the direct current sensor is an overhead direct current Hall sensor.

According to the technical scheme, the upper computer is a portable mobile device capable of directly sending the control command, and the upper computer is provided with a keyboard for input, a keyboard processing and display processing circuit and a display.

According to the technical scheme, the upper computer is communicated with the microprocessor through the RS232 interface.

The invention also provides a mine direct-current overhead line short circuit detection method, which is based on the rectification power supply device for the mine direct-current overhead line of the embodiment, the detection method comprises the step of comprehensively judging the overhead line short circuit condition through rectification power supply overhead line current fault identification and input alternating-current power supply voltage drop fault identification, and the detection method specifically comprises the following steps:

detecting whether the identification algorithm of the overhead line current fault of the rectification power supply reaches the predetermined condition of the overhead line current fault; and

detecting whether the voltage of an input alternating current power supply line of the rectifying power supply falls to a preset setting threshold value,

if any detection result is negative, the situation of the short circuit of the overhead line is judged not to be met, and therefore the protection action is not carried out.

According to the technical scheme, the comprehensive judgment of the short-circuit condition of the overhead line based on the overhead line current rise rate and the overhead line current steady-state increment comprises the following steps:

detecting whether the current rise rate of the overhead line reaches a preset current rise rate setting value or not; and

detecting whether the steady-state increment of the rack line current reaches a preset setting threshold value,

if any detection result is negative, the situation of the short circuit of the overhead line is judged not to be met, and therefore the protection action is not carried out.

In connection with the above technical solution, in the method for detecting an overhead line short circuit, the method further includes determining an overhead line short circuit condition based on a time when an overhead line current rise rate falls below a preset current rise rate setting value, and specifically includes:

detecting whether the time for the rise rate of the rack line current to fall below a preset current rise rate setting value is within a preset return delay setting value or not;

if the detection result is negative, the situation of the short circuit of the overhead line is judged not to be met, and therefore the protection action is not carried out.

According to the technical scheme, under the conditions that the rising rate of the current of the detection frame line reaches a preset current rising rate setting value, the steady-state increment of the current of the detection frame line reaches a preset setting threshold value, and the time for the rising rate of the current of the detection frame line to fall below the preset current rising rate setting value is within a preset return delay setting value, if the delay time of the steady-state increment of the current of the detection frame line reaches the preset delay setting value, the situation that the current of the detection frame line is in fault is judged to be met.

According to the technical scheme, under the conditions that the current rise rate of the detection rack line reaches a preset current rise rate setting value, the steady-state increment of the current of the detection rack line reaches a preset setting threshold value, and the time for the current rise rate of the detection rack line to fall below the preset current rise rate setting value is within a preset return delay setting value, if the voltage of the rack line of the rectification power supply is within a normal range, the situation of long-distance short circuit of the rack line is judged to be met.

According to the technical scheme, under the conditions that the current rise rate of the detection frame line reaches a preset current rise rate setting value, the steady-state increment of the current of the detection frame line reaches a preset setting threshold value, and the time for the current rise rate of the detection frame line to fall below the preset current rise rate setting value is within a preset return delay setting value, if the output voltage of the frame line of the rectification power supply is lower than a normal range, the situation that the high current is started by the short-circuit protection operation is judged to be in accordance with the situation that the short-circuit protection operation is not carried out.

According to the technical scheme, when the detection of the identification algorithm of the trolley line current faults of the rectification power supply reaches the trolley line current fault preset condition, because the input three-phase alternating current power supply of the rectification power supply is supplied by the rectifier transformer, and the rectifier transformer has internal resistance, when the trolley line is in a short circuit condition, the voltage of the input alternating current power supply line falls to a large extent, whether the voltage of the input alternating current power supply line of the rectification power supply in suspected trolley line current faults falls to a preset setting threshold value is detected, if so, the condition that the trolley line is in short circuit is judged to be met, and therefore protection action is carried out. If not, the short circuit of the overhead line is judged not to be met, and the protection action is not carried out.

The invention has the following beneficial effects: according to the rectifying power supply for the mine direct-current overhead line and the overhead line short-circuit current detection method thereof, the current rise rate and the current increment of the direct current output by the rectifying power supply and the direct-current voltage output by the rectifying power supply are calculated in real time, and the direct-current long-distance overhead line short-circuit current and the multi-locomotive short-distance starting current of the power supply system of the mine direct-current overhead line rectifying power supply can be effectively distinguished by a method for comprehensively judging and combining the current rise rate, the current increment and the overhead line voltage, so that the reliable detection and protection of the overhead line short-circuit fault are realized, and the safety guarantee is provided for the mine underground direct-current overhead line power supply system.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

fig. 1 is a general block diagram of a rectifying power supply device for a mine down-hole direct current overhead line with short-circuit protection;

FIG. 2 is a diagram of several exemplary overhead line DC current and fault determinations;

FIG. 3(a) is a flow chart of a main process of the rectified power supply;

fig. 3(b) is a logic flow diagram of the stringing current real-time fault identification subroutine.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

First, a general hardware structure of a rectifying power supply device for a mine direct-current overhead line with short-circuit protection is described.

Referring to fig. 1, fig. 1 is a general block diagram of a rectification power supply device with short-circuit protection for a mine dc overhead line according to an embodiment of the present invention. The rectification power supply device includes: the three-phase vacuum alternating current contactor comprises a three-phase vacuum alternating current contactor 1, a three-phase full-bridge rectification circuit 2, an overhead line direct current Hall current sensor 3, an alternating current input line voltage sensor 4, a microprocessor 5 and an upper computer 6.

The three-phase full-bridge rectifier circuit 2 may be a three-phase full-bridge thyristor rectifier circuit.

The microprocessor 5 is a minimum system of a microprocessor (DSP) and comprises a rectifying power supply direct current and voltage acquisition circuit, signals such as acquisition contactor input state and control register start and stop, fault storage, information transmission to an upper computer and the like.

The upper computer 6 can be a computer, a mobile phone and other portable mobile devices which directly send out control commands. The upper computer 6 has a keyboard for input, a keyboard processing and display processing circuit, and a display such as an LCD.

In the rectification power supply device of the invention, the three-phase vacuum AC contactor 1 is used for controlling whether to access a three-phase AC power supply; the three-phase full-bridge rectifying circuit 2 is used for providing direct current for rectifying three-phase alternating current into pulsation, and is connected in series behind the three-phase vacuum alternating current contactor 1; the overhead line direct current Hall sensor 3 is used for detecting the direct current output of the rectification power supply, namely the real-time current of the overhead line, and is connected to the overhead line in series; the AC input line voltage sensor 4 is used for sampling the AC input line voltage of the rectification power supply and is connected in parallel with two ends of the AC input phase; the microprocessor 5 is used for controlling the work of the three-phase full-bridge rectifying circuit 2, further outputting a forward pulsating direct current power supply to a direct current overhead line, detecting an output direct current and an output direct voltage of the rectifying power supply, respectively connecting the output of the overhead line direct current Hall sensor 3, the output of the alternating current input line voltage sensor 4 and the output of the three-phase full-bridge rectifying circuit 2, and respectively controlling the work states of a switching tube in the alternating current contactor 1 and the three-phase full-bridge rectifying circuit 2 through the outputs; the upper computer 6 communicates with the microprocessor 5 through an RS232 interface.

The stringing direct current hall sensor 3 and the alternating current input line voltage sensor 4 respectively detect the output direct current and the output direct voltage of the rectifying power supply, and the microprocessor 5 extracts the characteristics of the output direct current and the output direct voltage to obtain the characteristics of a sample and obtain several typical direct current stringing currents and corresponding protection action conditions. The method for detecting the overhead line short circuit comprises the steps of comprehensively judging the overhead line short circuit condition by rectifying power supply overhead line current fault identification and input alternating current power supply voltage drop fault identification, comprehensively judging the overhead line short circuit condition, and detecting whether the input alternating current power supply line voltage drops to a preset setting threshold value when suspected overhead line current faults occur or not by detecting whether the input alternating current power supply line voltage of the rectifying power supply is in line with the preset setting threshold value or not when the detection result shows that the input alternating current power supply voltage drops to the preset setting threshold value when the detection result shows that the suspected overhead line current faults occur, so that protection action is carried out. If not, the short circuit of the overhead line is judged not to be met, and the protection action is not carried out.

The mine direct-current overhead line short circuit detection method is mainly based on the rectification power supply device for the mine direct-current overhead line of the embodiment, and comprises the following steps of comprehensively judging the overhead line short circuit condition by rectification power supply overhead line current fault identification and input alternating-current power supply voltage drop fault identification:

detecting whether the identification algorithm of the overhead line current fault of the rectification power supply reaches the predetermined condition of the overhead line current fault; and

detecting whether the voltage of an input alternating current power supply line of the rectifying power supply falls to a preset setting threshold value,

if any detection result is negative, the situation of the short circuit of the overhead line is judged not to be met, and therefore the protection action is not carried out.

Further, the comprehensive judgment of the overhead line short circuit condition based on the overhead line current rise rate and the overhead line current steady-state increment comprises the following steps:

detecting whether the current rise rate of the overhead line reaches a preset current rise rate setting value or not; and

detecting whether the steady-state increment of the rack line current reaches a preset setting threshold value,

if any detection result is negative, the situation of the short circuit of the overhead line is judged not to be met, and therefore the protection action is not carried out.

In connection with the above technical solution, in the method for detecting an overhead line short circuit, the method further includes determining an overhead line short circuit condition based on a time when an overhead line current rise rate falls below a preset current rise rate setting value, and specifically includes:

detecting whether the time for the rise rate of the rack line current to fall below a preset current rise rate setting value is within a preset return delay setting value or not;

if the detection result is negative, the situation of the short circuit of the overhead line is judged not to be met, and therefore the protection action is not carried out.

Further, under the condition that the rise rate of the current of the detection rack line reaches a preset current rise rate setting value, the steady-state increment of the current of the detection rack line reaches a preset setting threshold value, and the time for the rise rate of the current of the detection rack line to fall below the preset current rise rate setting value is within a preset return delay setting value, if the delay time of the steady-state increment of the current of the detection rack line reaches the preset delay setting value, the situation that the current of the detection rack line is in fault is judged to be met.

Further, under the condition that the rise rate of the current of the detection rack line reaches a preset current rise rate setting value, the steady-state increment of the current of the detection rack line reaches a preset setting threshold value, and the time for the rise rate of the current of the detection rack line to fall below the preset current rise rate setting value is within a preset return delay setting value, if the voltage of the rack line of the rectification power supply is within a normal range, the situation of long-distance short circuit of the rack line is judged to be met.

Further, under the condition that the detection frame line current rise rate reaches a preset current rise rate setting value, the detection frame line current steady-state increment reaches a preset setting threshold value, and the time that the detection frame line current rise rate falls below the preset current rise rate setting value is within a preset return delay setting value, if the frame line output voltage of the rectifier power supply is lower than a normal range, the situation that the large current for starting the frame line close-range locomotive is met is judged, and therefore short-circuit protection operation is not conducted.

Further, when the detection rectification power supply overhead line current fault recognition algorithm reaches the overhead line current fault preset condition, because the input three-phase alternating current power supply of the rectification power supply is supplied by the rectifier transformer, and the rectifier transformer has internal resistance, when the overhead line is in a short circuit condition, the voltage of the input alternating current power supply line falls to a larger extent, whether the voltage of the input alternating current power supply line of the rectification power supply in suspected overhead line current fault falls to a preset setting threshold value is detected, if so, the situation of the overhead line short circuit is judged to be met, and therefore protection action is carried out. If not, the short circuit of the overhead line is judged not to be met, and the protection action is not carried out.

Referring to fig. 2, fig. 2 is a diagram illustrating several exemplary rack dc currents and their corresponding rack current fault determinations.

In fig. 2, the abscissa axis is a time axis, and the ordinate axis is a setting current value axis. Fig. 2 shows the curves for four typical cases, as follows:

curve (1): the current steady-state increment delta i exceeds a preset setting threshold, but the delay time of the current steady-state increment delta i is not enough (namely is less than a preset delay setting value); this situation is not consistent with a short-circuit condition of the overhead line, at which time the overhead line current fault determination is not established.

Curve (2): the current rise rate di/dt is kept higher than a preset current rise rate setting value, and the delay time of the current rise rate di/dt reaches the preset delay setting value; the current steady-state increment delta i exceeds a preset setting threshold, and the delay time of the current steady-state increment delta i reaches a preset delay setting value; this situation is consistent with the situation of the short circuit of the overhead wire, and the judgment of the current fault of the overhead wire is established at the moment.

Curve (3): in the continuous current rising process, the current rising rate di/dt is kept higher than a preset current rising rate setting value, only the current rising rate di/dt temporarily falls below the preset current rising rate setting value in the middle stage, the falling time does not reach the preset return delay setting value, then the current rising rate di/dt continues to rise and is kept higher than the preset current rising rate setting value until the current steady-state increment delta i exceeds the preset setting threshold value, and the delay time of the current steady-state increment delta i also reaches the preset delay setting value; this situation is consistent with the situation of the short circuit of the overhead wire, and the judgment of the current fault of the overhead wire is established at the moment.

Curve 4): contrary to the curve (3), in the process of current rising, the current rising rate di/dt falls back to be below the current rising rate setting value, and the falling time exceeds the preset return delay setting value, so that the protection return condition is met, namely, the fault protection identification analysis is restarted at the end point e of the falling time, namely, the point e is used as a new reference point for detection and identification, and the situation of the short circuit of the overhead line is not met under the condition, so that the fault judgment of the overhead line current is not established.

Based on the analysis of the typical situations, the invention further provides a process flow of the real-time sampling fault diagnosis program of the overhead line current. Specifically, the method comprehensively judges the short-circuit condition of the overhead line by identifying the fault of the overhead line current of the rectifier power supply and identifying the drop fault of the input alternating-current power supply voltage, and is a method for detecting and comprehensively judging the short-circuit current of the direct-current overhead line power supply system under the mine based on the current rise rate of the overhead line, the current increment and the input alternating-current voltage. Mainly, a stringing current fault identification program part for performing rapid timing real-time sampling on stringing current is described, please refer to fig. 3, where fig. 3 includes a main program flow chart and a stringing current fault identification program chart for performing timing real-time sampling:

as shown in fig. 3(a), the main program of the microprocessor mainly includes: initializing registers such as an AD (analog-digital) register, a timer and the like of a processor, starting a power supply instruction, identifying an algorithm program of an overhead line current fault, detecting whether an effective value of an input alternating current power line voltage falls to a threshold value or not after determining that the overhead line current fault is established, if so, determining that the overhead line short-circuit fault is established, timely disconnecting a vacuum contactor, and stopping power supply of a rectification power supply;

as shown in fig. 3(b), the stringing current fault identification subroutine mainly includes steps of determining whether the two indexes of the current increase rate and the steady-state current increment reach the action threshold, if so, respectively performing delay setting to judge again, and determining that the stringing current fault is established only when all the conditions meet the predetermined conditions. The specific process is as follows: monitoring the overhead line current in real time, calculating the current rise rate di/dt according to the twice interval sampling current values, starting to identify the overhead line fault when the current rise rate di/dt exceeds a preset setting threshold value, sampling the current values at intervals again after a period of time delay, calculating the current rise rate di/dt, and judging the current steady-state increment if the current rise rate di/dt exceeds the preset setting threshold value; and if the di/dt does not exceed the preset setting threshold value at the moment, returning to re-sampling the current again and judging. Monitoring the overhead line current again, calculating the steady-state increment of the current, monitoring the overhead line current again and calculating the steady-state increment of the current after a period of time delay if the steady-state increment of the current exceeds the preset setting threshold, and judging that the fault of the overhead line current is established if the steady-state increment of the current exceeds the preset setting threshold; and judging that the overhead line current fault is not established as long as the current steady-state increment does not exceed the preset setting threshold. And sampling the stringing current in real time in a reciprocating manner and judging.

In summary, the dc overhead line short-circuit current identification technology of the rectifying power supply for the mine dc overhead line adopts a method of comprehensively judging and combining the overhead line current rise rate, the current increment and the overhead line voltage, and can effectively distinguish the dc long-distance overhead line short-circuit current and the multi-locomotive short-distance starting current of the power supply system of the coal mine underground overhead line rectifying power supply, thereby realizing the reliable detection and protection of the overhead line short-circuit fault.

It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.