CN105676071A - High-resistance control method for fault line selection - Google Patents

Abstract

The invention provides a high-resistance control method for fault line selection. The method comprises: when occurrence of a permanent ground fault in a distribution network system is determined, a controller carries out high resistance switching, inputs a specific-resistance current signal into the system, and determines a fault line; and the specific-resistance current signal flows on a fault line between a system power supply and a ground point. According to the invention, a problem of inaccurate line selection in line selection and arcing ground over-voltage according to a way of grounding of a neutral point by an arc suppression coil in a distribution network can be solved effectively.

Description

A high resistance control method for fault line selection

technical field

The invention relates to the technical field of power grid systems, in particular to a high-resistance control method for fault line selection.

Background technique

In recent years, with the continuous development of the power system, the scale of the distribution network is also increasing. In the distribution network, cables are widely used to replace traditional overhead lines. The capacitance of the system line to ground increases significantly. When a single-phase ground fault occurs in the system When , the capacitance current to ground increases, which will affect the safe and reliable operation of the power system.

At present, in the distribution network system, the operation mode in which the neutral point is grounded through the arc-suppression coil is mostly used. When the system has an instantaneous single-phase ground fault, it can be eliminated by the action of the arc-suppression coil to ensure that the system is continuously powered; when it is a permanent single-phase When a ground fault occurs, the action of the arc suppression coil can still maintain the system running for 2 hours, which can make the operating department have enough time to start the backup power supply or transfer the load, so as not to cause passiveness; when the system is single-phase grounded, the arc suppression coil can effectively avoid arc grounding Overvoltage, which protects the power equipment of the whole network.

Compared with the traditional turn-adjusting and air-gap adjusting arc suppressing coils, a large number of adjustable intelligent arc suppressing coils are used in the current distribution network. The structure of the arc-suppressing coil is the same as that of a common transformer, with high-voltage windings and low-voltage windings, no air gap in the core column, and a simple structure. Not only can the inductor current be continuously adjustable, but also a filter device is added to control the current of the secondary winding by adjusting the firing angle of the thyristor, so as to realize the continuous controllability of the primary side inductor current. The tertiary winding is an LC filter circuit, which is used to suppress the harmonic current generated when the thyristor is turned on. When the power grid is operating normally, the filter circuit of the tertiary winding is capacitive at the fundamental frequency, and the equivalent circuit is also capacitive, which has no effect on the normal operation of the power system; when the thyristor is initially turned on, due to the effect of leakage reactance, the equivalent The circuit is inductive. Gradually adjusting the trigger control angle of the thyristor can change the conduction angle of the thyristor between 0° and 180°, so as to realize continuous adjustment of the inductance of the arc suppression coil. When the system is running normally, the arc suppressing coil works away from the resonance point, and when a single-phase ground fault occurs, it is immediately adjusted to the compensation state, which can effectively avoid the series resonance between the arc suppressing coil and the ground capacitance, compared with the conventional arc suppressing coil , with the adjustable arc suppression coil with real-time tracking distribution network, the advantages of flexible compensation.

However, in practical applications, it is found that in the grounding system of the neutral point through the adjustable arc suppression coil, when a single-phase ground fault occurs in the system, if the arc suppression coil is not reliably connected, the charge on the ground capacitance cannot pass through the neutral point. The release can only be released from the voltage transformer, so a high-amplitude surge current will be formed in the voltage transformer, causing the voltage transformer to burn out.

Contents of the invention

The purpose of the embodiments of the present invention is to provide a high resistance control method for fault line selection with accurate line selection.

In order to achieve the above purpose, the present invention provides a high resistance control method for fault line selection, the method includes: when it is determined that a permanent ground fault has occurred in the distribution network system, the controller switches the high resistance and injects multiple times into the system The specific resistive current signal is used to determine the fault line; the specific resistive current signal circulates on the fault line between the system power supply and the grounding point.

Preferably, the switching of the high resistance by the controller includes: the controller injects a specific resistive current signal into the system 3 times, each input time t2 is 0.5 seconds, and each time interval t1 is 1 second.

Preferably, the above determination that a permanent ground fault has occurred in the distribution network system includes: the controller detects the open triangle voltage of the three-phase power transformer, and when the voltage is higher than the phase voltage of the distribution network system, and the voltage state remains If the time cannot be eliminated by itself within 5 seconds, it is determined that a permanent ground fault has occurred in the distribution network system.

Preferably, the injection of specific resistive current signals into the system multiple times to determine the fault line includes: the line selection device collects the ground current signals of each line, and when one or more lines present resistive current signal characteristics, determine a One or more lines are fault lines.

Preferably, the above distribution network includes an arc suppression coil, the neutral point of the power grid is grounded through the arc suppression coil, and the high resistance is connected in parallel to the arc suppression coil, specifically, the above arc suppression coil body includes a primary winding and several The secondary winding, the high-voltage resistor is connected in parallel to the high-voltage end and the low-voltage end of the primary winding, and the low-voltage end is grounded.

Preferably, the above-mentioned arc suppression coil also includes a first secondary winding, and the first secondary winding is a control winding that can be connected to the silicon-controlled control circuit; the above-mentioned arc suppression coil also includes a second secondary winding, and the second two The secondary winding is connected with the filter circuit.

Preferably, the filtering circuit includes a first harmonic filtering branch and a second harmonic filtering branch respectively connected in parallel to both ends of the second secondary winding.

Preferably, a switching switch is connected in series between the filtering circuit and the second secondary winding.

The beneficial effect of the embodiment of the present invention is: by judging that a permanent ground fault has occurred in the distribution network system, injecting multiple specific resistive current signals into the system, specifying the interval time, and each input time, thereby judging the faulty line, effective It solves the problem of inaccurate line selection in the line selection and arc-elimination grounding overvoltage of the distribution network through the arc-suppressing coil parallel high-resistance grounding mode.

Description of drawings

Fig. 1 is the schematic diagram of the parallel resistor of the adjustable arc suppressing coil of the present invention;

Fig. 2 is a schematic diagram of the high resistance control method for fault line selection in the present invention.

detailed description

In order to facilitate the understanding of those skilled in the art, the present invention will be further described below in conjunction with the accompanying drawings, which cannot be used to limit the protection scope of the present invention. It should be noted that, in the case of no conflict, the embodiments in the present application and various manners in the embodiments can be combined with each other.

As shown in Figure 1, the arc suppression coil device of the present invention includes an arc suppression coil, a thyristor control circuit and a filter circuit. The arc suppression coil includes a primary winding and several secondary windings. The high-voltage end and low-voltage end of the resistor are connected in parallel, and the low-voltage end is grounded. Specifically, the resistor is a high resistance; several secondary windings include the first secondary winding and the second secondary winding, and the first secondary winding is the control winding. Thyristor control loop, the thyristor control loop mainly includes a pair of anti-parallel thyristor SCR, by adjusting the trigger angle of the thyristor to adjust the inductance value of the first and secondary windings. The second secondary winding is connected to the filter circuit, and the filter circuit includes a first harmonic filter branch and a second harmonic filter branch respectively connected in parallel at both ends of the second secondary winding, and the first and second harmonic filter branches are respectively A capacitor and inductor connected in series. Optionally, the first harmonic filtering branch may be a 3rd harmonic filtering branch for filtering out the 3rd harmonic; the second harmonic filtering branch may be a 5th harmonic filtering branch for filtering Divide the 5th harmonic. Optionally, in this embodiment, a switching switch may also be connected in series between the filter circuit and the second secondary winding for controlling switching of the filter circuit. The neutral point of the distribution network is grounded through the arc suppressing coil device.

The resistors connected in parallel at both ends of the arc-suppression coil of the present invention are put into operation for a short time only when the line selection needs to be started after a ground fault occurs. When no ground fault occurs in the grid system, the ground resistance is disconnected from the neutral point, Therefore, the resistance will not generate a lot of heat, and its own reliability coefficient is high.

The neutral point of the distribution network is grounded through the arc-suppression coil, and there are still certain difficulties in line selection and arc-light grounding overvoltage elimination. The arc-suppression coil is connected in parallel with a high-resistance grounding method to eliminate arc-light grounding, but there is a problem of inaccurate line selection. The present invention simultaneously High resistance control methods for fault line selection are also provided.

As shown in Figure 2, when working, when the distribution network system fails, the present invention adopts the high-resistance control method of fault line selection, and the controller controls high-resistance switching through the vacuum contactor, and outputs resistive current signals to the power grid , specifically, the high resistance control method for fault line selection includes:

When it is determined that a permanent ground fault has occurred in the distribution network system, the controller switches high resistance, injects multiple specific resistive current signals into the system, and specifies the time and interval of each injection to determine the fault line; the specific resistance A neutral current signal circulates on the fault line at the system power and ground points.

Further, determining that a permanent ground fault has occurred in the distribution network system includes: the controller detects the open triangle voltage of the three-phase power transformer, and when the voltage is higher than the phase voltage of the distribution network system, and the voltage state is maintained for a period of time If it cannot be eliminated by itself within 5 seconds, it is determined that a permanent ground fault has occurred in the distribution network system.

Further, multiple times of specific resistive current signals are injected into the system to determine the fault line, including: the line selection device collects the ground current signals of each line, and when one or more lines show the characteristics of resistive current signals, judge one or more lines Multiple lines are faulty lines. Specifically, when a single-phase ground fault occurs in a certain line, the ground resistance there is the lowest, and the resistive current signal sent by the ground resistance of the neutral point will only flow through the faulty line, and the line selection device collects the voltage of each line. Grounding current signal, when a line is found to exhibit resistive current signal characteristics, it is judged that the line is a faulty line.

Preferably, the switching of the high resistance by the controller includes: the controller injects a specific resistive current signal into the system 3 times, each input time t2 is 0.5 seconds, and each time interval t1 is 1 second.

The specific operation steps are as follows:

In the first step, the vacuum contactor and high resistance are installed in the substation, and the controller is connected to the open triangle voltage of the three-phase voltage transformer;

In the second step, when the controller detects that the open delta voltage of the three-phase voltage transformer is higher than 35% of the phase voltage of the distribution network system, and this overvoltage state cannot be eliminated by itself within the holding time t0 of 5 seconds, it determines that the distribution A permanent ground fault occurs in the power grid system; after the judgment time, the controller switches the high resistance 3 times, each input time t2 is 0.5 seconds, and each interval time t1 is 1 second, and injects a specific resistive current signal into the system , the signal only circulates on the faulty line between the system power supply and the grounding point;

In the third step, the controller judges the fault line through the specific resistive current signal.

The control method of the invention can be used in the control logic of the 10kV power grid in parallel connection with high resistance grounding through the arc suppressing coil.

The above are only preferred embodiments of the present invention. Of course, the present invention also has other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various Corresponding changes and modifications, but these corresponding changes and modifications should belong to the scope of protection of the appended claims of the present invention.

Claims (10)

1. A high resistance control method for fault line selection, characterized in that, the method comprises: When it is determined that a permanent ground fault has occurred in the distribution network system, the controller switches high resistance, injects multiple specific resistive current signals into the system, and determines the fault line; flow on the faulty line. 2. The control method according to claim 1, wherein the switching of the high resistance by the controller comprises: the controller injects a specific resistive current signal into the system for 3 times, each input time t2 is 0.5 seconds, each time The interval time t1 is 1 second. 3. The control method according to claim 1, wherein the determining that a permanent ground fault occurs in the distribution network system comprises: The controller detects the triangular voltage at the opening of the three-phase power transformer. When the voltage is higher than the phase voltage of the distribution network system, and the voltage state cannot be eliminated within 5 seconds, it is determined that a fault has occurred in the distribution network system. Permanent ground fault. 4. The control method according to claim 1, wherein said injecting multiple specific resistive current signals into the system to determine the fault line comprises: the line selection device collects the ground current signals of each line, and when each line Or when multiple lines exhibit resistive current signal characteristics, it is judged that one or more lines are faulty lines. 5. The control method according to any one of claims 1 to 4, wherein the distribution network includes an arc suppression coil, the neutral point of the distribution network is grounded through the arc suppression coil, and the The high resistance is connected in parallel at both ends of the arc suppressing coil. 6. The control method according to claim 5, wherein the arc suppression coil includes a primary winding and several secondary windings, the high voltage resistor is connected in parallel to the high voltage end and the low voltage end of the primary winding, and the low voltage end is grounded . 7. The control method according to claim 6, wherein the arc suppressing coil further comprises a first secondary winding, and the first secondary winding is a control winding which can be connected to a silicon controlled control circuit. 8. The control method according to claim 7, wherein the arc suppressing coil further comprises a second secondary winding, and the second secondary winding is connected to a filter circuit. 9 . The control method according to claim 8 , wherein the filtering circuit comprises a first harmonic filtering branch and a second harmonic filtering branch respectively connected in parallel to both ends of the second secondary winding. 10. The control method according to claim 9, characterized in that a switching switch is connected in series between the filter circuit and the second secondary winding.