CN203911463U - Single-phase earthing circuit protection device of power distribution network for arc-suppression coil-based neutral-point earthing system - Google Patents

Abstract

The utility model provides a single-phase grounding line protection device for a distribution network with a neutral point through an arc suppression coil grounding system, a controlled DC power supply installed at the grounding end of the neutral point arc suppression coil and a DC current detector. The controlled DC power supply is connected in series between the connection point 11 and the connection point 12 of the ground terminal of the neutral point arc suppression coil, including a DC blocking capacitor C, a control switch K, a current limiting resistor R, a voltage stabilizing module, a power transformer T, a diode D1 and D2; the DC current detector includes a power supply +Vc, a DC current sensor and a comparator. The line protection device of the utility model can accurately determine the specific faulty line, and send a grounding signal. According to the specific requirements of the actual line, trigger the follow-up protection to send an alarm signal or directly trip and cut off the power. reliability.

Description

Single-phase grounding line protection device for distribution network with neutral point via arc-suppressing coil grounding system

technical field

The utility model relates to the technical field of relay protection for distribution lines, in particular to a protection device for a single-phase grounding line of a power distribution network in a neutral point grounding system through an arc suppression coil.

Background technique

In the power system, the distribution network below 66KV often adopts the neutral point indirect grounding operation mode. For the neutral point non-grounded distribution network, when a single-phase grounding occurs, the current flowing through the fault point is the sum of the zero-sequence current of the non-fault phase of the entire grid, that is, the capacitive current of the entire network. If the current value is very large, an arc will be ignited on the ground, causing intermittent arc overvoltage, causing non-fault phase insulation damage, and then developing into a phase-to-phase fault or a multi-point ground fault, leading to the expansion of the accident. Therefore, when the 22-66kV distribution network is single-phase grounded, if the sum of the zero-sequence capacitor current at the fault point is greater than 10A, the 10kV distribution network is greater than 20A, and the 3-6kV distribution network is greater than 30A, the neutral point of the power supply should be Grounded through the arc suppression coil.

In the distribution network whose neutral point is grounded through the arc suppressing coil, the inductive current of the arc suppressing coil is generally used to compensate the capacitive current of the whole grid, and the compensation method is overcompensation. In this case, when the line is single-phase grounded, zero-sequence power directional protection cannot be used to select the faulty line, and because the residual current is not large, it is difficult to meet the sensitivity requirements by using zero-sequence current protection. Therefore, in this type of distribution network, it is very difficult to realize ground protection.

When a single-phase ground fault occurs in a non-directly grounded neutral point distribution network, since the ground fault current is small and the line voltage between the three phases remains symmetrical, the impact on the load power supply is minimal, so in general, it is allowed to exist In the case of a grounding point, continue to run for a period of time (1 to 2 hours) without tripping immediately. However, after a single-phase ground occurs, the other two phase-to-ground voltages that are not grounded will rise times, in order to prevent the expansion of the fault, the protection should send a signal in time, so that the operator on duty can take measures to remove the fault in time. Therefore, when single-phase grounding occurs in the neutral point non-directly grounded distribution network, generally only the relay protection device is required to issue a warning signal without tripping. But when there is danger to the safety of the person and equipment, it should act on the circuit breaker to trip.

For the distribution network whose neutral point is grounded through the arc-suppression coil, when the distribution network is multi-line (almost always in actual operation), when any line in the distribution network is single-phase grounded, zero sequence will appear in the whole network. Voltage, at this time, the zero-sequence voltage protection can be used to send out an alarm signal. But what it sends is the alarm signal that does not select the specific faulty line. In order to find out the faulty line, the personnel on duty must disconnect each line for a short time in sequence, and then automatically reclose the disconnected line and put it into operation again. When a line is disconnected and the zero-sequence voltage signal disappears, it means that the line is a faulty line. The above operations are also called line selection operations.

Using the line selection operation method will cause a short-term power outage on the line, and operating the circuit breaker back and forth will reduce the service life of the circuit breaker and cause accidents. If some lines are not allowed to be powered off, the line selection operation cannot be performed.

In order to overcome the above-mentioned defects that the prior art exists, the utility model is proposed.

Utility model content

In view of this, the utility model provides a single-phase grounding line protection device for the distribution network of the neutral point through the arc suppressing coil grounding system, which can accurately determine the specific fault line by connecting the controlled DC power supply and the DC current detector and The grounding signal is issued to ensure reliability under the premise of avoiding human intervention.

A single-phase grounding line protection device for a distribution network with a neutral point grounded through an arc suppression coil, including a controlled DC power supply installed at the ground end of the neutral point arc suppression coil and a DC current detection device installed at the outlet of each distribution line device.

The controlled DC power supply includes a DC blocking capacitor C, a control switch K, a current limiting resistor R, diodes D1 and D2, a voltage stabilizing module, and a power transformer T. One end of the current limiting resistor R is connected to the DC output grounding terminal of the voltage stabilizing module, and the other end of the current limiting resistor R is respectively connected to the cathode terminals of the diodes D1 and D2; the anode terminals of the diodes D1 and D2 are respectively connected to the The DC output ground terminal of the voltage stabilizing module is connected to the DC output anode terminal; the AC input terminal of the voltage stabilizing module is connected to 220V AC through a power transformer T.

The DC current detector includes a power supply +Vc, a DC current sensor and a comparator; the signal output terminal of the DC current sensor is connected to the signal input terminal of the comparator on the one hand, and the output terminal of the comparator is grounded signal; on the other hand, the signal output terminal of the DC current sensor directly outputs the detected leakage DC current value; the working power supply of the DC current sensor and the comparator is connected to the power supply +Vc.

The controlled DC power supply is connected in series between the connection point 11 and the connection point 12 of the ground terminal of the neutral point arc suppressing coil.

The DC current sensor is a Hall DC current sensor.

The control switch K is connected with the zero-sequence voltage protection of the power distribution network.

The control switch K is also manually controlled as an experimental switch.

The beneficial effects that the utility model produces are:

A single-phase grounding line protection device for a distribution network with a neutral point via an arc-suppression coil grounding system, which can accurately determine the specific faulty line and send a grounding signal, so that the subsequent protection device can operate, or send an alarm signal according to the specific requirements of the actual line Or directly trip and cut off the power.

Description of drawings

The present invention is more fully and better understood when considered in conjunction with the accompanying drawings. The accompanying drawings described here are used to provide a further understanding of the utility model, and the embodiments and description thereof are used to explain the utility model, and do not constitute improper limitations to the utility model, wherein:

Figure 1-a is a single power supply multi-line distribution network of the single-phase grounding line protection device of the utility model neutral point through the arc suppression coil grounding system distribution network;

Fig. 1-b is the phasor diagram of the voltage and current of A, B and C phases of Fig. 1-a;

Fig. 2 is a schematic diagram of the installation of the single-phase grounding line protection device of the distribution network in the distribution network of the neutral point through the arc suppression coil grounding system of the present invention;

Fig. 3 is a schematic diagram of the installation of the DC current detector of the single-phase grounding line protection device of the distribution network through the arc suppressing coil grounding system of the utility model at the outlet of the cable line;

Fig. 4 is a schematic diagram of the structure of the controlled DC power supply of the single-phase grounding line protection device of the utility model neutral point through the arc suppressing coil grounding system;

Fig. 5 is a schematic structural diagram of a DC current detector of a single-phase grounding line protection device for a distribution network grounding system with a neutral point via an arc suppressing coil according to the present invention.

In the figure: 1. Controlled DC power supply (11, 12) wiring point 13, DC blocking capacitor C 14, control switch K 15, current limiting resistor R 16, diode D1 17, diode D2 18, voltage stabilizing module 19, power transformer T 2. DC current detector 21, DC current sensor 22, comparator 3, cable head 31, power supply terminal 32, magnetic ring.

Detailed ways

The technical solution of the present utility model will be described in further detail below in conjunction with the accompanying drawings and embodiments. A more complete and better understanding of the invention and many of its accompanying advantages are readily apparent when considered in conjunction with the accompanying drawings, but the accompanying drawings illustrated herein are intended to provide a further understanding of the invention and constitute a part of the invention , the exemplary embodiment of the utility model and its description are used to explain the utility model, and do not constitute an improper limitation of the utility model.

First of all, the specific working principle of the utility model is: the single-power multi-line distribution network with the neutral point grounded through the arc suppressing coil shown in Figure 1-a, the equivalent capacitance of the power supply side and each line to the ground is C _0G , C ₀₁ , C ₀₂ , C ₀₃ , represented by concentrated capacitance. Assuming that phase A of line WL3 is short-circuited to ground, and ignoring the voltage drop of load current and capacitive current on the line impedance, the voltage of A relative to ground of all lines and power sources in the distribution network is zero, and the relative capacitive current of each component A is also zero. to zero. The arc suppression coil is L. When a single-phase grounding occurs, the B-phase and C-phase voltage and capacitive current of each component increase At this time, the capacitive current distribution of the distribution network is shown in Figure 1-a. The capacitive currents of phase B and phase C of each component pass through the ground, fault point, power supply, arc suppression coil and this component to form a loop. The phasor diagram is as follows Figure 1-b shows.

at zero sequence voltage Under the action, the arc suppression coil has an inductive current It flows back to the arc suppressing coil through the grounding point. Assuming the inductance value of the arc suppression coil is L, then the inductor current is:

${\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span>\frac{{\stackrel{<span\; class="notranslate">\; \&CenterDot;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}}_{\mathrm{<span\; class="notranslate">\; A</span>}}}{\mathrm{<span\; class="notranslate">\; j\&omega;L</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{{\stackrel{<span\; class="notranslate">\; \&CenterDot;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}}_{\mathrm{<span\; class="notranslate">\; A</span>}}}{\mathrm{<span\; class="notranslate">\; \&omega;L</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Total current through ground for:

${\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}}_{\mathrm{<span\; class="notranslate">\; K</span>}}<span\; class="notranslate">\; =</span>{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}}_{\mathrm{<span\; class="notranslate">\; C\&Sigma;</span>}}<span\; class="notranslate">\; -</span>{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Right now:

${\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; I</span>}}}_{\mathrm{<span\; class="notranslate">\; K</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; j</span>}{\stackrel{<span\; class="notranslate">\; \&Center\; Dot;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}}_{\mathrm{<span\; class="notranslate">\; A</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}\mathrm{<span\; class="notranslate">\; \&omega;L</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

In the formula: C _0Σ is the sum of each phase-to-ground capacitance of the whole grid, It is the sum of the capacitance current of the whole grid to the ground, and the value of ω is 314.

It can be seen from the above formula that choosing a suitable inductance can make the total current flowing through the fault point when the single phase is grounded Reduced, or even zero, so that the intensity of the arc generated by the capacitive current can be reduced, so the inductance is called arc suppression inductance. However, in actual operation, an overcompensation method is adopted, that is, the compensated inductor current is greater than the capacitor current of the entire network.

It can be seen that the function of the arc suppression coil is to use the inductance current to compensate the capacitive current at the grounding point, so as to eliminate or weaken the arc at the grounding point. The over-compensation method is adopted. After compensation, since the grounding current is very small, and the zero-sequence current direction of the faulty line and the non-faulty line are the same, when a single-phase grounding occurs in a certain line, the zero-sequence power direction protection cannot be used to select the faulty line. And because the residual current is not large, it is difficult to meet the sensitivity requirements by using zero-sequence current protection. Therefore, in this type of distribution network, it is very difficult to realize grounding protection, and only the line selection method can be used.

Example 1

As shown in Figure 2, a single-phase grounding line protection device for a distribution network with a neutral point grounded through an arc suppression coil is connected in series between two connection points (11, 12) at the ground end of the neutral point arc suppression coil A controlled DC power supply 1 and a DC current detector 2 are installed at the power outlet of each power distribution cable line. Connecting the controlled DC power supply 1 to the ground terminal can greatly reduce the withstand voltage level of the equipment of the present invention, reduce the cost and improve the operation reliability.

As further shown in Figures 3-5, the DC current detector 2 installed on the power supply terminal 31 includes a power supply +Vc, a DC current sensor 21 and a comparator 22, and the magnetic ring 32 of the DC current sensor 21 is set on the cable terminal 3. DC current in the cable can be detected. As a preferred embodiment, the DC current sensor 21 uses a Hall DC current sensor to detect the DC current component of the distribution cable line, and the comparator 22 is used to detect the DC current component detected by the Hall DC current sensor. The DC current component of the cable line is compared with the DC current threshold inside the comparator 22. If the former is greater than the latter, the comparator 22 will output a grounding signal to the subsequent control equipment, and send an alarm signal or action to protect the trip.

The above-mentioned DC current threshold inside the comparator can be adjusted, and the power supply +Vc can use an ordinary DC power supply.

The structure of the controlled DC power supply 1 is shown in Figure 4, including a DC blocking capacitor 13, a control switch 14, a current limiting resistor 15, a voltage stabilizing module 18, a power transformer 19, 220V AC and diodes D1 and D2 (16, 17). The diodes D1 and D2 are DC power protection components, and the current limiting resistor R15 and diodes D1 and D2 ( 16 , 17 ) are DC power protection components for protecting the voltage stabilizing module 18 . Wherein the voltage stabilizing module 18 is a conventional voltage stabilizing element.

The control switch 14 can be connected with the zero-sequence voltage protection in the system, and can also be used as an experimental switch.

Since the DC-blocking capacitor C is connected in series with the ignition coil L, when there is a zero-sequence voltage at the neutral point, there is also a zero-sequence voltage divider on C. When selecting the parameters of C, the zero-sequence partial voltage on C should be reduced as much as possible. As far as the utility model is concerned, when the zero-sequence voltage at the neutral point is the largest, the zero-sequence voltage division on C does not exceed 15V.

When the control switch 14 is connected with the zero-sequence voltage protection in the system, once a grounding short circuit occurs in the distribution network and the zero-sequence voltage protection action such as an alarm signal is issued, the control switch 14 will be closed, and the stability of the controlled DC power supply 1 The DC voltage output by the voltage module 18 will be added to the DC blocking capacitor C, and the lines with grounding short circuit in the system will have DC current flowing, while the lines without grounding short circuit in the system will not have DC current flowing.

The power transformer 19 is used to transform the 220V AC power into a suitable voltage so as to make the controlled DC power supply 1 work normally.

When there is no single-phase ground fault in the distribution network, the zero-sequence voltage protection of the distribution network does not operate, and the controlled DC power supply 1 of the utility model does not add DC voltage to the system, and is installed at the power outlet of each distribution line The DC current detector 2 at the terminal cannot detect the DC component, so it does not send out a grounding signal.

When a single-phase ground fault occurs in the distribution network, if the zero-sequence voltage protection of the distribution network operates, the controlled switch K in the controlled DC power supply 1 of the utility model is closed, and a DC voltage is added to the system, which is installed in the fault The DC current detector 2 at the power outlet of the distribution line detects the DC component and sends out a grounding signal; while the DC current detector 2 installed at the power outlet of the non-faulty distribution line does not detect the DC component and does not send out a grounding signal.

Due to the diversity of system wiring, the wiring diagram given in the accompanying drawings of the utility model is only a schematic diagram, but those skilled in the art can completely and clearly understand the specific connection mode of the system wiring through the wiring diagram.

Example 2

When the outlet end of the distribution line is not a cable line, then as shown in Figure 3, a DC current detector 2 installed at the outlet end of each distribution cable line will be installed on each phase of each distribution line The installed three DC current detectors 2 are consistent with the first embodiment.

Example 3

When the control switch K14 in Fig. 4 is used as the experimental switch of the present utility model, it can not only check the operating status of the entire protection device, but also check the ground leakage current status of each distribution line in the entire distribution network. The method is to set the output voltage value of the controlled DC power supply 1 of the utility model and the operating current value of the DC current detector 2 .

When the distribution network is running normally, manually close the control switch K14, the output voltage value of the controlled DC power supply 1 is added to the entire network, and the DC current detector 2 at the outlet of each distribution cable line will detect the leakage of each line For the DC current value, the output DC current in Figure 5 can be taken out and analyzed, and the specific leakage current of each transmission line in the distribution network can be judged, so that measures can be taken in time.

As mentioned above, the embodiments of the present utility model have been described in detail. Obviously, as long as they do not substantially deviate from the invention points and effects of the present utility model, the modifications that are obvious to those skilled in the art are also included in the present utility model. within the scope of the new protection.

Claims (5)

1. neutral by arc extinction coil grounding system power net single-phase earthing line protective devices; it is characterized in that; comprise a direct current detector that is arranged on the controlled DC power supply of neutral point grounding through arc end and is arranged on every distribution line port of export, wherein:

Described controlled DC power supply comprises partiting dc capacitor C, control switch K, current-limiting resistance R, diode D1 and D2, Voltage stabilizing module and power transformer T, the two ends of described partiting dc capacitor C are connected with one end of current-limiting resistance R and the direct current of Voltage stabilizing module output earth terminal by control switch K respectively, and the other end of described current-limiting resistance R is connected with the cathode terminal of described diode D1 and D2 respectively; The anode tap of described diode D1 and D2 is connected with direct current output anode end with the direct current output earth terminal of Voltage stabilizing module respectively; The ac input end of described Voltage stabilizing module is connected with 220V alternating current by power transformer T;

Described direct current detector comprises power supply+Vc, DC current sensor and comparator; The signal output part of described DC current sensor is connected with the signal input part of described comparator on the one hand, the output output ground signalling of described comparator; The signal output part of the described DC current sensor leakage DC current values that directly output detections arrives on the other hand; The working power of described DC current sensor and comparator is connected with described power supply+Vc.

2. a kind of neutral by arc extinction coil grounding system power net single-phase earthing line protective devices according to claim 1, is characterized in that, described controlled DC power supply is connected between first wiring point and the second wiring point of neutral point grounding through arc end.

3. a kind of neutral by arc extinction coil grounding system power net single-phase earthing line protective devices according to claim 1, is characterized in that, described DC current sensor is Hall DC current sensor.

4. a kind of neutral by arc extinction coil grounding system power net single-phase earthing line protective devices according to claim 1, is characterized in that, described control switch K is connected with the zero-sequence voltage protection of power distribution network.

5. a kind of neutral by arc extinction coil grounding system power net single-phase earthing line protective devices according to claim 1, is characterized in that, described control switch K manually controls as experiment switch simultaneously.