CN107204609B - A distribution network busbar protection device and method for self-identification of grounding method - Google Patents

Abstract

The invention discloses a grounding mode self-identifying busbar protection device of a distribution network, which comprises: a collection circuit for collecting the electrical quantity characteristics of the current busbar line respectively, wherein the electrical quantity characteristics include the current busbar zero-sequence differential current and the current bus zero-sequence voltage; the judgment circuit is used to judge whether the grounding method of the current bus line is the neutral point through small resistance grounding method according to the electrical quantity characteristics in the current bus line; the zero-sequence differential protection circuit is used for the current bus line. The grounding method of the current bus line is that when the neutral point is grounded through a small resistance, the zero-sequence differential protection is activated and a control signal is output to control the switch off of the current bus line. The invention also discloses a busbar protection method of a distribution network with self-identification of the grounding mode. The distribution network busbar protection device with self-identification of the grounding mode provided by the present invention solves the problem that the busbar of the distribution network cannot be protected when the grounding mode is changed.

Description

A distribution network busbar protection device and method for self-identification of grounding method

technical field

The invention relates to the field of power system relay protection, in particular to a distribution network busbar protection device with grounding mode self-identification and a distribution network busbar protection method with grounding mode self-identification.

Background technique

At present, the grounding method of medium-voltage distribution network usually adopts neutral point ungrounded system, neutral point grounding system through arc suppression coil or neutral point grounding system through small resistance according to the difference of grounding capacitance current. When a single-phase grounding fault occurs in the distribution line, the neutral point ungrounded system or the arc suppression coil system does not need to remove the fault, and can continue to operate for 1.5 to 2 hours, while the neutral point grounding system with a small resistance needs to remove the fault immediately, otherwise It will cause the small resistance device to burn out.

At present, the busbar protection in the power distribution station usually adopts the principle of phase differential protection. After the power grid fails, the differential current of any phase exceeds the fixed value, and the fault will be removed, which will bring the following problems:

(1) For the neutral point grounding system with a small resistance, the grounding current is usually limited to a lower level due to the existence of the grounding resistor. Therefore, for the differential phase differential protection, in order to realize the single-phase fault protection under the small current grounding system For protection, it is necessary to reduce the phase differential protection setting, which will bring risks to the reliable operation of the bus differential protection, and a certain heavy-load line current transformer (CT) disconnection may cause protection misoperation.

(2) The busbar protection cannot automatically identify the grounding method of the distribution network. If the grounding method is changed from the neutral point ungrounded system or the arc suppression coil grounding system to the small resistance grounding system, the differential phase differential protection setting cannot be automatically reduced. The busbar protection refuses to act after the single-phase grounding of the busbar occurs; if the grounding method is changed from the neutral point via the small resistance grounding system to the neutral point ungrounded system or the grounding system via the arc suppression coil, the phase differential protection setting cannot be automatically improved , reduce operational risk.

(3) The two busbars of a substation may be powered by two substations with different grounding methods. Usually, busbar protection can only set a set of phase-phase differential action settings, which is not conducive to realizing single-phase grounding under different grounding methods. Differentiated relay protection methods.

The current neutral point ungrounded system or the grounding system through the arc suppression coil usually adopts the differential protection principle for busbar protection. In the arc suppression coil grounding system, the busbar phase differential protection setting is high, and the busbar single-phase fault does not trip; station B is a neutral point grounding system with a small resistance, the busbar phase phase differential protection setting is low, and the busbar single-phase fault divides Phase differential protection action trips. When the operation mode is adjusted to the power point of station B with station A for series operation, if a single-phase grounding fault occurs on the busbar of station A, the busbar protection device of station A cannot immediately act to remove the fault, and the fault will be removed by the circuit protection of the B1 switch after a delay. In this way, the fault can be quickly removed by the switch of station A. As a result, the B1 switch needs to delay for a period of time to remove the fault, and the scope of the power outage is also expanded. The bus fault in station A is usually the main equipment fault, and the removal time is significantly longer. Very unfavorable.

Therefore, when the grounding method is changed, how to protect the busbar of the distribution network has become an urgent technical problem to be solved.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the technical problems existing in the prior art, and provides a distribution network busbar protection device with a grounding mode self-identification and a distribution network busbar protection method with a grounding mode self-identification, so as to solve the problem of the existing problems in technology.

As a first aspect of the present invention, there is provided a distribution network busbar protection device with self-identifying grounding mode, wherein the distribution network busbar protection device with self-identifying grounding mode includes:

a collection circuit, which is used to collect electrical quantity characteristics of the current bus line respectively, wherein the electrical quantity characteristics include the current bus zero-sequence differential current and the current bus zero-sequence voltage;

a judgment circuit, the judgment circuit is connected with the acquisition circuit, and is used for judging whether the grounding mode of the current bus line is the grounding mode of the neutral point through a small resistance according to the electric quantity characteristic in the current bus line;

Zero-sequence differential protection circuit, the zero-sequence differential protection circuit is connected with the judgment circuit, and is used to start the zero-sequence when the grounding method of the current bus line is the grounding method at the neutral point through a small resistance Differential protection and output control signal to control the switch off of the current bus line.

Preferably, the judgment circuit includes: a zero-sequence differential current value judgment circuit,

The zero-sequence differential current value judgment circuit is used to judge whether the current bus zero-sequence differential current is greater than the first threshold, and when the current bus zero-sequence differential current is greater than the first threshold, determine the grounding of the current bus line The method is that the neutral point is grounded through a small resistance.

Preferably, the first threshold value is 10A.

Preferably, the judgment circuit includes: a zero-sequence differential current phase judgment circuit,

The zero-sequence differential current phase judgment circuit is used to judge the phase relationship between the current bus zero-sequence differential current and the current bus zero-sequence voltage, when the current bus zero-sequence differential current and the current bus zero-sequence When the sequence voltages are in the same phase, it is determined that the wiring mode of the current bus line is that the neutral point is grounded through a small resistance.

Preferably, the zero-sequence differential protection circuit includes a zero-sequence differential protection start-up circuit and an output control circuit,

The zero-sequence differential protection starting circuit is used for starting the zero-sequence differential protection and sending an output signal when the current bus zero-sequence differential current is greater than the starting zero-sequence differential protection value;

The output control circuit is connected to the zero-sequence differential protection starting circuit, and is used for outputting a control signal according to the output signal to control the switch off of the current bus line.

As a second aspect of the present invention, a method for protecting a distribution network busbar with self-identifying grounding mode is provided, wherein the method for protecting a distribution network busbar with self-identifying grounding mode includes:

Collect the electrical quantity characteristics of the current bus line respectively, wherein the electrical quantity characteristics include the current bus zero-sequence differential current and the current bus zero-sequence voltage;

According to the electric quantity characteristic in the current bus line, determine whether the grounding method of the current bus line is the neutral point grounding method through a small resistance;

When the grounding method of the current bus line is the grounding method at the neutral point through a small resistance, the zero-sequence differential protection is activated and a control signal is output to control the switch off of the current bus line.

Preferably, the step of judging whether the grounding method of the current bus line is the grounding method of the neutral point via a small resistance according to the electrical quantity characteristics in the current bus line includes:

Determine whether the current bus zero-sequence differential current is greater than the first threshold, and when the current bus zero-sequence differential current is greater than the first threshold, determine that the grounding method of the current bus line is the neutral point grounding method through a small resistance .

Preferably, the step of judging whether the grounding method of the current bus line is the grounding method of the neutral point via a small resistance according to the electrical quantity characteristics in the current bus line includes:

Determine the phase relationship between the current bus zero-sequence differential current and the current bus zero-sequence voltage, and when the current bus zero-sequence differential current and the current bus zero-sequence voltage are in the same phase, determine the wiring of the current bus line The method is that the neutral point is grounded through a small resistance.

Preferably, when the grounding method of the current bus line is the grounding method at the neutral point through a small resistance, start zero-sequence differential protection and output a control signal to control the switch off of the current bus line The steps include:

When the current bus zero-sequence differential current is greater than the starting zero-sequence differential protection value, start the zero-sequence differential protection and send an output signal;

A control signal is output according to the output signal to control the turning off of the switch of the current bus line.

The self-identifying busbar protection device of the distribution network provided by the present invention collects the current busbar zero-sequence differential current and the current busbar zero-sequence voltage through the acquisition circuit, and the judgment circuit is based on the current busbar zero-sequence differential current and the current busbar zero-sequence The voltage determines whether the grounding method of the current line is the neutral point grounding method through a small resistance. When the neutral point is grounded through a small resistance, the zero-sequence differential protection circuit starts the zero-sequence differential protection function. The protection device can automatically identify the grounding mode of the current bus line according to the electrical quantity characteristics, and then perform corresponding zero-sequence differential protection according to the grounding mode, which solves the problem that the bus line cannot be protected when the grounding mode changes.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and together with the following specific embodiments, are used to explain the present invention, but do not constitute a limitation to the present invention. In the attached image:

FIG. 1 is a schematic diagram of a line grounding method in the prior art.

FIG. 2 is a schematic structural diagram of a distribution network busbar protection device with self-identifying grounding method provided by the present invention.

FIG. 3 is a schematic diagram of a zero-sequence protection enabling area provided by the present invention.

FIG. 4 is the main wiring diagram of the power distribution site provided by the present invention.

FIG. 5 is a working principle diagram of the distribution network busbar protection device with self-identifying grounding method provided by the present invention.

FIG. 6 is a flowchart of a method for protecting a distribution network busbar with a self-identifying grounding method provided by the present invention.

Detailed ways

The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, but not to limit the present invention.

As a first aspect of the present invention, a distribution network busbar protection device with self-identifying grounding method is provided, as shown in FIG. 2 , wherein the distribution network busbar protection device 10 with self-identifying grounding method includes:

A collection circuit 100, the collection circuit 100 is used to collect electrical quantity characteristics of the current bus line respectively, wherein the electrical quantity characteristics include the current bus zero-sequence differential current and the current bus zero-sequence voltage;

a judgment circuit 110, the judgment circuit 110 is connected with the acquisition circuit 100, and is used for judging whether the grounding method of the current bus line is the neutral point grounding method through a small resistance according to the electric quantity characteristic in the current bus line;

A zero-sequence differential protection circuit 120, the zero-sequence differential protection circuit 120 is connected to the judgment circuit 110, and is used for when the grounding method of the current bus line is the grounding method at the neutral point via a small resistance, The zero-sequence differential protection is activated and a control signal is output to control the switch-off of the current bus line.

The self-identifying busbar protection device of the distribution network provided by the present invention collects the current busbar zero-sequence differential current and the current busbar zero-sequence voltage through the acquisition circuit, and the judgment circuit is based on the current busbar zero-sequence differential current and the current busbar zero-sequence The voltage determines whether the grounding method of the current line is the neutral point grounding method through a small resistance. When the neutral point is grounded through a small resistance, the zero-sequence differential protection circuit starts the zero-sequence differential protection function. The protection device can automatically identify the grounding mode of the current bus line according to the electrical quantity characteristics, and then perform corresponding zero-sequence differential protection according to the grounding mode, which solves the problem that the bus line cannot be protected when the grounding mode changes.

As a specific implementation of the judgment circuit 110, the judgment circuit 110 includes: a zero-sequence differential current value judgment circuit, and the zero-sequence differential current value judgment circuit is used to judge the current bus zero-sequence differential Whether the current is greater than the first threshold value, when the current bus zero-sequence differential current is greater than the first threshold value, it is determined that the grounding method of the current bus line is the neutral point grounding method through a small resistance.

Specifically, the zero-sequence differential current of the fault busbar in the neutral point grounding method is usually large, but usually does not exceed the first threshold value. The zero-sequence differential current of the faulted bus is very small under the single-phase fault of the arc coil grounding method (the neutral point runs through the arc suppression coil in a state of skipping compensation), and the neutral point is grounded through the arc suppression coil. The non-faulted bus is under single-phase fault There is no zero-sequence differential current, and the zero-sequence differential current of the fault bus is relatively large when the neutral point is grounded through a small resistance.

Preferably, the first threshold value is 10A.

As another specific implementation of the judgment circuit 110, the judgment circuit 110 includes: a zero-sequence differential current phase judgment circuit, and the zero-sequence differential current phase judgment circuit is used to judge the current bus zero-sequence The phase relationship between the differential current and the current bus zero-sequence voltage, when the current bus zero-sequence differential current and the current bus zero-sequence voltage are in the same phase, determine that the current bus line wiring mode is the neutral point Grounded via a small resistance.

Specifically, the zero-sequence differential current of the faulted busbar lags the zero-sequence voltage of the busbar by about 90° under a single-phase fault in the neutral point ungrounded mode, and the non-faulted busbar has no zero-sequence differential current; the neutral point is grounded through the arc suppression coil. The zero-sequence differential current leads the zero-sequence voltage of the bus by about 90°, and the non-faulted bus has no zero-sequence differential current; the zero-sequence differential current of the fault bus is in the same phase as the zero-sequence voltage in the neutral point grounding system through a small resistance.

As a specific implementation of the zero-sequence differential protection circuit 120, the zero-sequence differential protection circuit 120 includes a zero-sequence differential protection startup circuit and an output control circuit, and the zero-sequence differential protection startup circuit is used when all the When the current bus zero-sequence differential current is greater than the starting zero-sequence differential protection value, the zero-sequence differential protection is activated and an output signal is sent; the output control circuit is connected to the zero-sequence differential protection start-up circuit for A control signal is output according to the output signal to control the turning off of the switch of the current bus line.

It should be noted that, in order to enhance the reliability of the line, an outlet loop is usually set directly in the zero-sequence differential protection circuit 120 and the switch. reliability.

It should also be noted that the zero-sequence differential protection circuit 120 usually further includes a relay, the control signal output by the output control circuit can control the conduction of the relay, and the control signal can be turned on after the relay is turned on. It is transmitted to the switch of the current bus line, thereby controlling the turn-off of the switch.

As a specific implementation of the zero-sequence differential protection startup circuit, when the zero-sequence differential protection is turned on, the zero-sequence differential current needs to meet the following conditions:

(1) I _10cd >I _qdh ,

Among them, I _10cd is the zero-sequence differential current, I _qdh is the starting zero-sequence differential protection value, and the value of I _qdh is generally selected as 15A for the neutral point ungrounded mode, and for the neutral The grounding method of the point via the arc suppression coil generally takes 1.05 times the rated current of the arc suppression coil. If there are multiple possible operation modes in the power grid, select it according to 1.05 times the rated current of the arc suppression coil with the maximum capacity.

(2) I _10cd >I _0ezd and

Wherein, I _10cd is the zero-sequence differential current, I _0ezd is the zero-sequence protection value at the extreme end of the bus line protection in the mode of the neutral point being grounded through a small resistance, and U ₀ is the zero-sequence voltage. The corresponding zero-sequence differential protection enable area is shown in Figure 3.

In addition, as shown in Figure 4 is the main wiring diagram of the power distribution station, the connection relationship in the main wiring diagram of the redistribution station of the busbar protection device self-identified by the grounding method can be seen from Figure 4, wherein, I bus zero The action equation of sequential differential protection is:

II mother zero-sequence differential protection action equation is:

In the above formula, I _i10 is the zero-sequence current of the incoming line of the I bus, I _i20 is the zero-sequence current of the incoming line of the II bus, I _f0 is the zero-sequence current of the segment switch, and I _j0 is the zero-sequence current of the jth outgoing line of the I bus where the device is located, m is the total number of outgoing lines of bus I, I _k0 is the zero-sequence current of the kth outgoing line of bus II where the device is located, n is the total number of outgoing lines of bus II, I _opo is the starting value of zero-sequence differential protection, which is set by avoiding the maximum zero-sequence unbalanced current. , S is the braking coefficient, which is set according to the maximum zero-sequence unbalanced current that escapes the fault outside the zone. All currents flow into the bus as the positive direction.

After the above formula is satisfied, the bus zero-sequence differential protection function is activated, and immediately trips the incoming line and sectional switches or all switches on the faulty bus (selected according to site requirements) without delay. For example, for the I bus fault, after the bus zero-sequence differential protection function is activated, the No. 1 incoming line switch, the segment switch and all the outgoing line switches connected to the I bus are tripped.

As shown in Figure 5, it is the working principle diagram of the distribution network busbar protection device with the self-identification of the grounding method. When the grounding mode is changed, the grounding mode can be judged by predetermined conditions to determine the input and withdrawal of the zero-sequence protection.

Specifically, as shown in Figure 5, in order to improve the reliability and adaptability of the busbar protection operation of the distribution network, a zero-sequence differential protection is added based on the original phase-phase differential protection in the busbar protection. Under various grounding methods, the phase-phase differential protection setting takes a unified large value, which is only used to protect various phase-to-phase short-circuit faults. For single-phase grounding faults, zero-sequence differential protection removes them. The zero-sequence differential protection is set according to the busbar segment. If the segment switch is in the sub-position, it can be activated or deactivated according to the system grounding method. If the sectional switch is in the closed position, if either of the zero-sequence differential protection of the two-stage bus is enabled, the two-stage zero-sequence differential protection functions are all enabled.

Further specifically, after the system failure protection is activated, if the phase-phase differential action equation is satisfied, the protection jumps off the corresponding switch of the I bus according to the predetermined setting;

When the system fails and the protection is activated, if the I bus zero-sequence differential is fixedly switched on, or the II bus zero-sequence differential is fixed and the segment switch is in the closed position, and the I bus zero-sequence differential protection action equation is satisfied, the protection will press The predetermined setting is to jump off the corresponding switch of the I mother;

When the system fails and the protection is activated, if the self-adaptive function of the I bus grounding mode is enabled, it is logically judged to be grounded through a small resistance, and the I bus zero-sequence differential protection action equation is satisfied, and the protection will trip the I bus according to the predetermined setting. switch.

As a second aspect of the present invention, as shown in FIG. 6 , a method for protecting a distribution network busbar with self-identifying grounding method is provided, wherein the method for protecting a distribution network busbar with self-identifying grounding method includes:

S110. Collect electrical quantity characteristics of the current bus line respectively, wherein the electrical quantity characteristics include the current bus zero-sequence differential current and the current bus zero-sequence voltage;

S120. Determine whether the grounding method of the current bus line is a neutral point grounding method through a small resistance according to the electrical quantity characteristics in the current bus line;

S130. When the grounding mode of the current bus line is the grounding mode at the neutral point via a small resistance, start zero-sequence differential protection and output a control signal to control the switch off of the current bus line.

The present invention provides a method for protecting the distribution network busbar with self-identification of the grounding mode. By collecting the current busbar zero-sequence differential current and the current busbar zero-sequence voltage of the current circuit, according to the current busbar zero-sequence differential current and the current busbar zero-sequence voltage It is judged whether the grounding method of the current bus is the neutral point grounding method through a small resistance, and when the neutral point is grounded through a small resistance, the zero-sequence differential protection function is activated. The protection method provided by the present invention can be based on electrical The quantitative feature automatically identifies the grounding mode of the distribution network busbar, and then performs corresponding zero-sequence differential protection according to the grounding mode, which solves the problem that the distribution network busbar cannot be protected when the grounding mode changes.

As a specific implementation manner, the step of judging whether the grounding method of the current bus line is the grounding method of the neutral point via a small resistance according to the electrical quantity characteristics in the current bus line includes:

Determine whether the current bus zero-sequence differential current is greater than the first threshold, and when the current bus zero-sequence differential current is greater than the first threshold, determine that the grounding method of the current bus line is the neutral point grounding method through a small resistance .

As another specific implementation manner, the step of judging whether the grounding method of the current bus line is the grounding method of the neutral point via a small resistance according to the electrical quantity characteristics in the current bus line includes:

Determine the phase relationship between the current bus zero-sequence differential current and the current bus zero-sequence voltage, and when the current bus zero-sequence differential current and the current bus zero-sequence voltage are in the same phase, determine the wiring of the current bus line The method is that the neutral point is grounded through a small resistance.

It can be understood that the above two specific embodiments are both criteria for judging the wiring mode of the current bus line, and through any of the above criteria, it can be judged whether the current bus line wiring mode is the neutral point through the small. Resistive grounding method.

Specifically, when the grounding method of the current bus line is the grounding method at the neutral point via a small resistance, start the zero-sequence differential protection and output a control signal to control the turn-off of the switch of the current bus line The steps include:

When the current bus zero-sequence differential current is greater than the starting zero-sequence differential protection value, start the zero-sequence differential protection and send an output signal;

A control signal is output according to the output signal to control the turning off of the switch of the current bus line.

For the specific implementation of the method for protecting the distribution network busbar with grounding mode self-identification, reference may be made to the foregoing description of the distribution network busbar protection device with grounding mode self-identification, which will not be repeated here.

It can be understood that the above embodiments are only exemplary embodiments adopted to illustrate the principle of the present invention, but the present invention is not limited thereto. For those skilled in the art, without departing from the spirit and essence of the present invention, various modifications and improvements can be made, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims (9)

1. a kind of power distribution network busbar protective device of earthing mode self-identifying, which is characterized in that the earthing mode self-identifying Power distribution network busbar protective device includes:

Acquisition Circuit, the Acquisition Circuit are used to acquire the electrical measure feature of current two buss lines respectively, wherein the electrical quantity Feature includes current bus zero sequence difference current and current bus residual voltage；

Decision circuitry, the decision circuitry are connect with the Acquisition Circuit, for according to described electrical in current two buss lines Measure feature judges whether the earthing mode of the current two buss lines is Neutral Point Through Low Resistance mode；

Zero sequence differential protection circuit, the zero sequence differential protection circuit are connect with the decision circuitry, for working as the current mother When the earthing mode of line route is the Neutral Point Through Low Resistance mode, starts zero sequence differential protection and export control signal To control the switch-off of the current two buss lines.

2. the power distribution network busbar protective device of earthing mode self-identifying according to claim 1, which is characterized in that described to sentence Deenergizing includes: zero sequence differential current value decision circuitry,

The zero sequence differential current value decision circuitry is for judging whether the current bus zero sequence difference current is greater than the first threshold Value determines that the earthing mode of current two buss lines is described when the current bus zero sequence difference current is greater than first threshold Neutral Point Through Low Resistance mode.

3. the power distribution network busbar protective device of earthing mode self-identifying according to claim 2, which is characterized in that described One threshold value is 10A.

4. the power distribution network busbar protective device of earthing mode self-identifying according to claim 1, which is characterized in that described to sentence Deenergizing includes: zero sequence difference current phase decision circuitry,

The zero sequence difference current phase decision circuitry is for judging the current bus zero sequence difference current and the current mother The phase relation of line residual voltage, when the current bus zero sequence difference current and the current bus residual voltage same-phase When, determine that the mode of connection of current two buss lines is the Neutral Point Through Low Resistance mode.

5. the power distribution network busbar protective device of earthing mode self-identifying according to claim 1, which is characterized in that described zero Sequence differential protection circuit includes zero sequence differential protection start-up circuit and output control circuit,

The zero sequence differential protection start-up circuit is used to be greater than the starting differential guarantor of zero sequence when the current bus zero sequence difference current When shield value, starts the zero sequence differential protection and issue output signal；

The output control circuit is connect with the zero sequence differential protection start-up circuit, is controlled for being exported according to the output signal Signal processed is to control the switch-offs of the current two buss lines.

6. a kind of power distribution network bus bar protecting method of earthing mode self-identifying, which is characterized in that the earthing mode self-identifying Power distribution network bus bar protecting method includes:

The electrical measure feature of current two buss lines is acquired respectively, wherein the electrical measure feature includes that current bus zero sequence is differential Electric current and current bus residual voltage；

According to the electrical measure feature in current two buss lines judge the current two buss lines earthing mode whether be Property point is through low resistance grounding mode；

When the earthing mode of the current two buss lines is the Neutral Point Through Low Resistance mode, start the differential guarantor of zero sequence It protects and exports control signal to control the switch-off of the current two buss lines.

7. the power distribution network bus bar protecting method of earthing mode self-identifying according to claim 6, which is characterized in that described Whether the earthing mode that the current two buss lines are judged according to the electrical measure feature in current two buss lines is neutral point warp The step of low resistance grounding mode includes:

Judge whether the current bus zero sequence difference current is greater than first threshold, when the current bus zero sequence difference current is big When first threshold, determine that the earthing mode of current two buss lines is the Neutral Point Through Low Resistance mode.

8. the power distribution network bus bar protecting method of earthing mode self-identifying according to claim 6, which is characterized in that described Whether the earthing mode that the current two buss lines are judged according to the electrical measure feature in current two buss lines is neutral point warp The step of low resistance grounding mode includes:

The phase relation for judging the current bus zero sequence difference current and the current bus residual voltage, as the current mother When line zero sequence difference current and the current bus residual voltage same-phase, determine that the mode of connection of current two buss lines is described Neutral Point Through Low Resistance mode.

9. the power distribution network bus bar protecting method of earthing mode self-identifying according to claim 6, which is characterized in that described to work as The earthing mode of the current two buss lines is described in Neutral Point Through Low Resistance mode, and starting zero sequence differential protection is simultaneously The step of output control switch-off of the signal to control the current two buss lines includes:

When the current bus zero sequence difference current is greater than starting zero sequence differential protection value, start the zero sequence differential protection simultaneously Issue output signal；

Control signal is exported according to the output signal to control the switch-off of the current two buss lines.