CN210690719U - Electric power overhead line ground fault range unit - Google Patents
Electric power overhead line ground fault range unit Download PDFInfo
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- CN210690719U CN210690719U CN201921185713.4U CN201921185713U CN210690719U CN 210690719 U CN210690719 U CN 210690719U CN 201921185713 U CN201921185713 U CN 201921185713U CN 210690719 U CN210690719 U CN 210690719U
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Abstract
The utility model discloses an electric power overhead line ground fault range unit, including signal source, auto-change over device, controller, the signal source is used for exporting high-pressure low frequency alternating current power supply signal, and auto-change over device is used for switching ranging system's internal parameter, and the controller is equipped with the electrical parameter that analog signal collection module is used for gathering two states around the auto-change over device switches. And the controller calculates the distance between the ground fault point and the power distribution station according to the electric quantity parameters before and after switching. The utility model discloses location trouble point position of being gross that can be quick shortens circuit trouble search time, improves the power supply quality.
Description
Technical Field
The utility model relates to a fault location technical field specifically is an electric power overhead line ground fault range unit among electric power system.
Background
A neutral point non-effective grounding mode, also called a low-current grounding system, is widely adopted in a 6 kV-35 kV power distribution network in China, and the system has the advantages that when a single-phase grounding fault occurs, a fault line does not need to be disconnected immediately, and operation with the fault is allowed for one to two hours. The disadvantage is that when a single-phase earth fault occurs, it is impossible to determine which line the fault occurs on, and the fault point cannot be found quickly. Since the rise in the phase voltage caused by such a fault poses a great threat to the insulation performance of the system, the faulty line must be quickly detected and removed. At present, relatively mature line selection devices and pointing devices are available on the market, but corresponding distance measuring devices are lacked. At present, a method of segmenting a fault line, hanging a detection sensor on a climbing rod and removing the fault line segment by segment is adopted, the operation process is relatively complex, and the fault fixed-point efficiency is low. Since there are multiple levels of branches in the distribution network and a large number of distribution transformers are installed on the lines, the impedance method, the traveling wave method, and other techniques widely used for transmission lines are difficult to apply to the distribution lines. Therefore, it is an urgent need to design a power transmission line fault distance measuring device.
Disclosure of Invention
The to-be-solved technical problem of the utility model is: an overhead line ground fault distance measuring device capable of measuring the distance between an overhead line ground fault point and a power distribution station outlet end.
The to-be-solved technical problem of the utility model is that: the utility model provides an electric power overhead line ground fault range unit, includes the controller, its characterized in that: still include signal source, auto-change over device and first sampling resistor, the second sampling resistor with controller electrical connection, the output of signal source exports high-pressure low frequency alternating current power supply signal, the two poles of the earth of signal source output end are signal pole and earthing pole respectively, the earthing pole ground connection, the switching device is the switching-over circuit that the relay constitutes, controller and switching device's relay electrical connection, the one end of first sampling resistor, second sampling resistor is respectively with signal pole electrical connection, the other end of first sampling resistor, second sampling resistor respectively with the two poles of the earth electrical connection of switching device input, the two poles of the earth of switching device's output are used for connecting the trouble phase and arbitrary non-trouble phase of earth fault circuit head end respectively, the first sampling resistor, the second sampling resistor under two states before the controller switches over through gathering switching device, back two states, The voltage value of the second sampling resistor and the voltage value output by the signal source provide original data for calculating the distance of the fault point, and the resistance values of the first sampling resistor and the second sampling resistor are different.
Preferably, the frequency of the high-voltage low-frequency alternating current power supply signal generated by the signal source is 0.5Hz to 15Hz, and the maximum output voltage is 80 percent to 110 percent of the rated voltage of the overhead line.
Preferably, the frequency of the high-voltage low-frequency alternating current power supply signal generated by the signal source is 1 Hz-5 Hz, and the maximum output voltage is 85% -100% of the rated voltage of the overhead line.
Preferably, the first sampling resistor and the second sampling resistor are precision resistors.
Preferably, the controller is provided with three analog signal acquisition modules for acquiring the voltage output by the signal source and the voltages of the first sampling resistor and the second sampling resistor.
Preferably, the controller is provided with five analog signal acquisition modules, wherein three analog signal acquisition modules are used for acquiring the voltages of the first sampling resistor and the second sampling resistor and the voltage output by the signal source, the fourth analog signal acquisition module is used for acquiring the voltage between one pole of the output end of the switching device and the fault connection point of the ground fault line and the signal pole, and the fifth analog signal acquisition module is used for acquiring the voltage between the other pole of the output end of the switching device and the non-fault connection point of the ground fault line and the signal pole.
Preferably, the short-circuit device further comprises a short-circuit piece for short-circuiting the fault phase and the non-fault phase at the tail end of the ground fault line, and the short-circuit piece is a wire with jointing clamps at two ends.
Preferably, the test box comprises a shell body and a test wire, wherein the shell body consists of a box body and a box cover, an operation panel is arranged in the box body, the signal source, the switching device and the controller are arranged at the lower part of the operation panel, a display, a switch and a test wire jack are embedded on the operation panel, the display is electrically connected with the controller, the test line jacks comprise two signal output jacks and two signal acquisition jacks, the two signal output jacks are electrically connected with the output end of the switching device, the two signal acquisition jacks are electrically connected with the input ends of the fourth and fifth analog signal acquisition modules, the test wire comprises a pincer-shaped jointing clamp, two wires are respectively led out from two clamp arms of the pincer-shaped jointing clamp, the end parts of the two wires are provided with plugs, one of the wires is used for being plugged with the signal output jack, and the other wire is used for being plugged with the signal acquisition jack.
A method for carrying out ground fault point ranging by applying a power overhead line ground fault ranging device is characterized in that: the line resistance from the ground fault point of the ground fault phase to the head end is a front section resistance, the line resistance from the ground fault point of the ground fault phase to the tail end is a rear section resistance, the total resistance of the ground fault line is the front section resistance plus the rear section resistance,
step 1, electrically connecting the output end of the switching device with a fault phase and any non-fault phase of the ground fault line at the head end of the ground fault line, grounding the grounding electrode of a signal source, and well short-circuiting the fault phase and the non-fault phase of the ground fault line at the tail end of the ground fault line;
step 2, starting a signal source to output a high-voltage low-frequency alternating-current power supply signal, and collecting and recording voltage values U of a first sampling resistor and a second sampling resistor before switching of a switching device11、U12And the voltage U output by the signal source10Then stopping the signal source;
step 3, starting the switching device, then starting the signal source to output a high-voltage low-frequency alternating-current power supply signal, and acquiring and recording the voltage values U of the first sampling resistor and the second sampling resistor after the switching device is switched21、U22And the voltage U output by the signal source20And then the signal source is stopped,
step 4, converting the voltage parameters collected in the step 2 and the step 3 into phasors, respectively listing equations according to kirchhoff voltage law, forming a linear equation set by the two equations, and calculating the resistance values of the front-section resistor, the rear-section resistor and the total resistor;
and 5, calculating the ratio of the length from the ground fault point to the head end to the total length of the line by using the front-segment resistor and the total resistor calculated in the step 4 according to the principle that the resistance value of the wire resistor is in direct proportion to the length of the wire.
A method for carrying out ground fault point ranging by applying a power overhead line ground fault ranging device is characterized in that: the line resistance from the ground fault point of the ground fault phase to the head end is a front section resistance, the line resistance from the ground fault point of the ground fault phase to the tail end is a rear section resistance, the total resistance of the fault line is the front section resistance plus the rear section resistance,
step 1, electrically connecting the output end of the switching device with a fault phase and any non-fault phase of the ground fault line at the head end of the ground fault line, grounding the grounding electrode of a signal source, and well short-circuiting the fault phase and the non-fault phase of the ground fault line at the tail end of the ground fault line;
step 2, starting a signal source to output a high-voltage low-frequency alternating-current power supply signal, and collecting and recording voltage values U of a first sampling resistor and a second sampling resistor before switching of a switching device11、U12And the voltage U output by the signal source10One of the output ends of the switching deviceVoltage U between the pole and ground fault line fault connection point and the signal pole13A voltage U between the other pole of the output end of the switching device and the non-fault connection point of the ground fault line and the signal pole14Then stopping the signal source;
step 3, starting the switching device, then starting the signal source to output a high-voltage low-frequency alternating-current power supply signal, and acquiring and recording the voltage U of the first sampling resistor and the voltage U of the second sampling resistor after the switching device is switched21、U22And the voltage U output by the signal source20A voltage U between one pole of the output end of the switching device and the ground fault line fault connection point and the signal pole23A voltage U between the other pole of the output end of the switching device and the non-fault connection point of the ground fault line and the signal pole24And then the signal source is stopped,
step 4, converting the voltage parameters collected in the step 2 and the step 3 into phasors, respectively listing equations according to kirchhoff voltage law, forming a linear equation set by the two equations, and calculating the resistance values of the front-section resistor, the rear-section resistor and the total resistor;
and 5, calculating the ratio of the length from the ground fault point to the head end to the total length of the line by using the front-segment resistor and the total resistor calculated in the step 4 according to the principle that the resistance value of the wire resistor is in direct proportion to the length of the wire.
The utility model has the advantages that: the general position of the fault point can be quickly positioned, the time for finding the line fault is shortened, and the power supply quality is improved.
Drawings
Figure 1 is a system schematic of an embodiment of the invention,
FIG. 2 is an equivalent circuit diagram before the switching of the switching device in the ranging,
figure 3 is an equivalent circuit diagram after the switching means switches at ranging,
figure 4 is a system schematic of a second embodiment of the invention,
FIG. 5 is an equivalent circuit diagram before the switching of the switching device in the ranging of the second embodiment,
FIG. 6 is an equivalent circuit diagram after the switching of the switching device in the ranging of the second embodiment,
fig. 7 is a schematic system diagram of a third embodiment of the present invention.
In the figure:
102. a ground electrode; 101. a signal electrode; r04, second contact resistance; r03, first contact resistance; rab, total resistance; rkb, back end resistance; rak, front section resistance; r01, a first sampling resistor; r02 and a second sampling resistor; 400. a controller; 300. an analog signal acquisition module; 200. a switching device; 100. a signal source; k01, relay;
Detailed Description
In order to make the technical solution and the beneficial effects of the present invention clearer, the following is a further detailed explanation of the embodiments of the present invention.
Example one
The electric power overhead line ground fault distance measuring device comprises a controller 400, a signal source 100 electrically connected with the controller 400, a switching device 200, a first sampling resistor R01 and a second sampling resistor R02. The controller 400 is a module or device having an input/output interface and a data processing function, and may be implemented by a microcomputer or a CPU chip such as a single chip microcomputer. In the field of microcomputer relay protection devices, controllers are arranged in intelligent electrical equipment such as the microcomputer relay protection devices and the like, and are used for realizing acquisition of remote signaling and remote measuring signals, output of the remote control signals and calculation of a relay protection function. The signal source 100 generates a high voltage, low frequency ac power signal under the control of the controller. The switching device 200 is used to apply the high-voltage low-frequency power signal generated by the signal source 100 to the faulty phase and the non-faulty phase of the ground fault line, and can switch the connection state of the two phases. The first sampling resistor R01, the second sampling resistor R02 and the controller 400 are electrically connected to acquire voltages of the first sampling resistor R01 and the second sampling resistor R02, and simultaneously acquire the voltage output by the signal source 100 to convert the acquired voltage signal into phasor form to provide original data for subsequent calculation.
In the prior art, a person skilled in the art considers that due to the effect of a hanging transformer and a line conductor on the ground capacitance on an overhead line, whether a direct current signal source or an alternating current signal source is adopted, the position of a ground fault is measured by adopting an impedance method, and the position has a large error. The utility model discloses an innovation point lies in: the conventional understanding and technical bias of the overhead line distance measurement of the technical personnel in the field are overcome, and the position of a fault point can be obtained by using an impedance method in a fault line loaded by a high-voltage low-frequency alternating-current power supply signal. Research and practice of developers of the company shows that when a high-voltage low-frequency alternating-current power supply signal is loaded between a fault phase and a non-fault phase and the ground, a signal injection mode is that two phase lines are injected to the ground, and at the moment:
first, the primary side inductance Zl of the transformer is 2 pi fL, and the higher the frequency and the larger the inductance, the larger the inductance value, and when the inductance value is much larger than the loop impedance, it is equivalent to an open circuit, and when the frequency is 0, it is a direct current, which is equivalent to a short circuit. In the prior art, the inductance of the transformer often reaches hundreds of henries, and even if the frequency is very low, the inductive reactance value is in the range of hundreds of henries and is far greater than the resistance of the overhead transmission line, so that the transformer can be considered to be in an open circuit state. In actual operation, due to the influence of the material and environment of the transmission line of the line, the voltage difference between the two phase lines is small, meanwhile, due to the fact that the injected current is small and generally below 100mA, and the maximum resistance of the cable is smaller than 10 Ω, the voltage difference between the two phase lines loaded with the high-voltage low-frequency alternating-current power supply signal is 1V or smaller than 1V. The current generated by the voltage difference of 1V to the transformer and the transformer load is very small and can be ignored, so that the influence of the transformer and the load on the distance measurement is avoided. When direct current is adopted, the transformer is equivalent to short circuit and also influences the measurement result, so that direct current is unavailable, namely 0Hz is unavailable.
The ground current generated by the distributed capacitance of the overhead transmission line after the alternating current signal is loaded cannot be avoided, wherein the total capacitance reactance Zc of the loop is 1/(2 pi fC), and the higher the frequency is, the larger the generated capacitive current is, and the measurement result is influenced. Therefore, the signal source 100 with lower frequency is selected, so that the capacitive reactance is higher, and the influence of the capacitive current on the measurement result is reduced. In the process of practical application, the influence of a transformer hung on a line can be ignored by using a high-voltage low-frequency alternating-current power supply signal, but the influence on the ground capacitance cannot be eliminated, and the influence of the capacitive current on the ground capacitance on the resistive current can only be infinitely reduced. In order to make the calculation more accurate, a phasor method is adopted for calculation in the calculation process. Or the acquired voltages are subjected to orthogonal operation to separate capacitive components and resistive components, and then resistive current is used for calculation and processing, and based on the controller 400, an analog signal acquisition module 300 for acquiring the voltage signals of the signal source 100 is further arranged.
And when a high-voltage low-frequency alternating-current power supply signal is adopted, the total capacitive reactance of the circuit is large, the capacitive current is small, the influence on the resistive current is small, and the resistive component can be separated through phasor calculation. Meanwhile, the inductance of the transformer in the hundred-henry level is equivalent to an open circuit, so that the high-voltage low-frequency alternating current power supply signal can be adopted, and the calculation and measurement can be carried out by adopting an impedance method. The frequency range is selected from 0.5 Hz-15 Hz through company comprehensive measurement and calculation. In order to reproduce the ground fault, the ground fault point is grounded again under the state of loading a high-voltage low-frequency alternating-current power supply signal, and the output voltage is 80% -110% of the rated voltage of the overhead line. Wherein the preferred output voltage is the rated voltage of the overhead line.
As shown in fig. 1, two poles of the output end of the signal source 100 are a signal pole 101 and a ground pole 102, respectively, and the ground pole 102 is grounded. The output terminal of the signal source 100 outputs a high-voltage low-frequency ac power signal. There are various ways and products for the signal source 100 to generate a high-voltage low-frequency ac power signal, and a low-frequency signal generator may generate a low-frequency signal, and then a step-up transformer or a voltage doubling circuit may be used to increase the voltage level. In this embodiment, the signal source 100 includes a digital power amplifier, a step-up transformer, and a voltage-multiplying circuit. The digital power amplifier is used for generating an alternating current signal. The step-up transformer steps up the alternating current signal voltage, and the voltage is further increased by the piezoelectric current. The on-off of the digital power amplifier output is controlled to generate a low-frequency signal, and the interrupted frequency is between 0.5Hz and 15 Hz.
Preferably, the frequency of the high-voltage low-frequency alternating-current power supply signal output by the signal source 100 is 1-5 Hz, and the voltage is 85% -100% of the rated voltage of the overhead line.
An external power supply or a power supply of a storage battery supplies power to the signal source 100 and each module in the controller 400, and an output interface of the controller 400 is connected with a control interface of each module to realize control. The control terminal or the control interface of the signal generator is electrically connected to the controller 400 for data communication and control signal transceiving. The controller 400 is a control device having an input/output interface and capable of performing data processing, and a control system constituted by a single chip microcomputer as a main chip is commonly used, and will not be described in detail herein.
Adopt the impedance method to need measuring current voltage parameter, for the convenience of detecting, the utility model discloses set up two sampling resistance, be first sampling resistance R01, second sampling resistance R02 respectively to first sampling resistance R01, second sampling resistance R02 are accurate resistance. As shown in fig. 1, one ends of the first sampling resistor R01 and the second sampling resistor R02 are electrically connected to the signal electrode 101, and the other ends of the first sampling resistor R01 and the second sampling resistor R02 are electrically connected to the input terminal of the switching device 200. The two poles of the output of the switching device 200 are used to connect the faulted phase and any non-faulted phase of the ground fault line, respectively. Therefore, the corresponding current and voltage parameters of the fault line can be obtained by collecting the voltages of the first sampling resistor and the second sampling resistor and the known resistance values of the first sampling resistor and the second sampling resistor, and a basis is provided for calculation.
The utility model discloses a form of unbalanced bridge tests to the unknown is two, is the ground fault point of earth fault looks to the line resistance of head end for anterior segment resistance Rak respectively, and the ground fault point of earth fault looks is back end resistance Rkb to terminal line resistance. Therefore, voltage parameters of the first sampling resistor R01 and the second sampling resistor R02 under two different states need to be measured to form a system of linear equations with two unknowns. The utility model discloses a switching device 200 changes the utility model discloses the parameter of the system of constituteing with the trouble circuit. The switching device 200 has the function of changing internal electrical parameters, in particular, changing the connection structure of the circuit. The switching device 200 in this embodiment includes a relay K01. Two pairs of normally open and normally closed contacts of the relay K01 form a reversing circuit. The input end or the output end of the commutation circuit is respectively connected with the first sampling resistor R01 and the second sampling resistor R02, and the other end is used as the output end of the switching device 200. As shown in fig. 1, two common terminals of the relay K01 are used as output terminals, a normally closed point of one switching contact of the relay K01 is short-circuited with a normally open point of the other switching contact to be used as one pole of an input terminal, and contacts of the remaining two switching contacts of the relay K01 are short-circuited to be used as the other pole of the input terminal. The coil winding of relay K01 is electrically connected to the control output of controller 400 to control the operation of relay K01. After the relay K01 is activated, the connection state between the output terminal and the input terminal of the relay K01 is changed. The output end of the commutation circuit is electrically connected with the output end of the switching device 200, the input end of the commutation circuit is respectively connected with the first sampling resistor R01 and the second sampling resistor R02, and the other ends of the first sampling resistor R01 and the second sampling resistor R02 are electrically connected with the signal electrode 101 of the input end of the switching device 200 after being connected. After the high-voltage low-frequency alternating-current power supply signal enters the switching device 200, the signal is divided into two paths through the signal electrode 101, and the two paths respectively pass through a commutation circuit consisting of a first sampling resistor R01, a second sampling resistor R02 and a relay K01 and reach the output end of the switching device 200. The switching device 200 in this embodiment changes the connection sequence of the first sampling resistor R01 and the second sampling resistor R02 with the failed phase and the non-failed phase by changing the switching device 200 to change the internal parameters of the circuit formed by the switching device and the failed line. In order to ensure that the parameters of the system change after the connection sequence is changed, the resistance values of the first sampling resistor R01 and the second sampling resistor R02 are different.
The controller 400 has three analog signal collecting modules 300 for collecting the voltage parameters of the first sampling resistor R01 and the second sampling resistor R02 and the voltage output by the signal source 100. The analog signal acquisition module 300 is a common functional module in a microcomputer relay protection device, and is used for acquiring voltage and current, and converting the voltage and the current into digital signals for subsequent calculation and processing. The specific circuit configuration is not illustrated here. The controller 400 provides a basis for calculating the distance of the fault point by acquiring the voltage parameters of the first sampling resistor R01 and the second sampling resistor R02 in the two states before and after switching of the switching device 200, and two sets of parameters form two equations to form a equation set to solve the front-stage resistor Rak and the rear-stage resistor Rkb.
Better, the utility model discloses during the range finding, need will the utility model discloses be connected with the trouble of earth fault circuit looks and non-trouble at the head end, with trouble looks and non-trouble looks short circuit at the end. Therefore, the utility model discloses still include short union piece, wherein short union piece has the wire of binding clip for both ends.
Based on the structure, the method for the electric power overhead line ground fault distance measurement device to carry out ground fault point distance measurement comprises the following steps:
the line resistance from the earth fault point of the earth fault phase to the head end is a front-stage resistance Rak, and the resistance value is RakThe line resistance from the earth fault point to the end of the earth fault phase is the back-end resistance Rkb with the resistance value of RkbThe total resistance Rab of the fault line is Rab。 Rab＝Rak+Rkb. The resistance values of the first sampling resistor R01 and the second sampling resistor R02 are R respectively01And R02And R is01≠R02. Use the utility model discloses head end at overhead transmission line is the example.
Step 1, as shown in fig. 1, the output end of the switching device 200 is electrically connected to the faulty phase and any one of the non-faulty phases of the ground fault line at the head end of the ground fault line, the ground electrode 102 of the signal source 100 is grounded, and the faulty phase and the non-faulty phase of the ground fault line are short-circuited well at the tail end of the ground fault line. The fault phase and the non-fault phase are in short circuit at the tail end, the three phases can be in short circuit simultaneously, and the fault phase and the non-fault phase of the device can be connected with the head end of the short circuit. After the short circuit is completed, a ranging loop is formed. Namely, the high-voltage low-frequency ac power signal of the signal source 100 is loaded to the ranging loop through the grounding network. The first ground electrode 102 is grounded, which corresponds to a ground point of a ground fault line connected to the ground, and thus forms a circuit.
And 2, starting the signal source 100 to output a high-voltage low-frequency alternating-current power supply signal, collecting and recording waveform data of voltage values of the first sampling resistor R01 and the second sampling resistor R02 before the switching device 200 switches and voltage waveform data output by the signal source 100, and then stopping the signal source 100.
Before the switching device 200 switches, as shown in fig. 2, the first sampling resistor R01 is connected to the non-fault phase and the second sampling resistor R02 is connected to the fault phase. The voltage waveform u ═ Uf (ω t + Φ), where Φ is the initial phase. The function f (ω t + φ) is a periodic function. In this embodiment, the initial phase of the output voltage of the signal source 100 is defined as 0 degree, and the initial phase is converted into phasor
The voltage output by the signal source 100 is used as a reference signal to obtain phasor values of the voltages of the first sampling resistor R01 and the second sampling resistor R02
And 3, starting the switching device 200, then starting the signal source 100 to output a high-voltage low-frequency alternating-current power supply signal, collecting and recording the voltages of the first sampling resistor R01 and the second sampling resistor R02 and the output voltage of the signal source 100 after the switching device 200 is switched, and then stopping the signal source 100.
As shown in fig. 3, after the switching device 200 switches, the first sampling resistor R01 is connected to the failed phase, and the second sampling resistor R02 is connected to the non-failed phase. After the connection is confirmed, the signal source 100 is started to output high-voltage low-frequency alternating current, the initial phase of the collected output voltage of the signal source 100 is set to be 0 degree, and the initial phase is converted into phasor
The phasor values of the voltages of the first sampling resistor R01 and the second sampling resistor R02 are
And 4, listing equations according to the principle that the voltages of the parallel circuits are equal by using the voltage parameters acquired in the step 2 and the step 3, forming a linear equation system by using the two equations, and calculating the resistance values of the front-section resistor Rak, the rear-section resistor Rkb and the total resistor Rab. The method specifically comprises the following steps:
after the phasor values of the voltage values in step 2 are obtained, phasor calculation can be performed, and then a real part and an imaginary part are separated from the calculated phasor value result, wherein the real part is the resistance of the power transmission line. Or, obtaining the resistive component of the voltage value by the quadrature calculation of the acquired phasor value, and then calculating by using the resistive component of the voltage. The latter is taken as an example first:
for example, to facilitate the calculation, wherein phasor values
U of (1)11And U12Is an effective value.
As shown in FIG. 2, prior to switching, the resistive current flowing through the non-faulted phase is
I11＝U11cosα1/R01(1)
Current flowing through fault phase
I12＝U12cosβ1/R02(2)
At this time, as known from kirchhoff's voltage law, the voltages of the two circuits connected in parallel are equal, and the following equations are listed
U11cosα1+I11(Rak+2Rkb)＝U12cosβ1+I12Rak(3)
Substituting into the formula (1) and the formula (2),
U11cosα1+(U11cosα1/R01)(Rak+2Rkb)＝U12cosβ1+(U12cosβ1/R02)Rak(4)
as shown in fig. 3, after the switching device 200 is operated, the current of the non-failure phase flows
I22＝U22cosβ2/R02(5)
The current flowing through the failed phase is,
I21＝U21cosα2/R01(6)
the equations are set forth below in the following table,
U21cosα2+I21Rak＝U22cosβ2+I22(Rak+2Rkb) (7)
substituting the formula (5) and the formula (6) into the formula (7),
U21cosα2+(U21cosα2/R01)Rak＝U22cosβ2+(U22cosβ2/R02)(Rak+2Rkb) (8)
the formula (4) and the formula (8) form a system of linear equations of two-dimensional, and the equations are solved by a program set inside the controller 400. The resistance of the back-end resistor Rkb of the front-end resistor Rak is solved.
And 5, calculating the ratio of the length from the ground fault point to the head end to the total length of the line by using the front-segment resistor Rak and the total resistor Rab calculated in the step 4 according to the principle that the resistance value of the wire resistor is in direct proportion to the length of the wire. The length of the line can be obtained from a description, a construction drawing, and an as-built drawing, which are known conditions, and assuming that L is the length, the distance D from the point k to the tip becomes L (R)ak/(Rak+Rkb))。
In step 4, the same calculation can be performed by using a phasor method, in which the line impedance from the ground fault point to the head end of the ground fault phase is the front-end impedance Xak with a reactance value of
The line impedance from the ground fault point to the end of the ground fault phase is the back-end impedance Xkb with an impedance value of
Calculate out
And
after resistance value, the reactance is separated
The real part of, i.e. the resistance of, the line is Rak＝|X|cosφ。
Example two
Since there is a certain contact resistance at the node of the relay K01 inside the switching device 200 and the connection point of the switching device 200 and the wire on the line, in order to reduce the influence of the contact resistance and improve the measurement accuracy, in this embodiment, on the basis of the first embodiment, five analog signal acquisition modules 300 of the controller 400 are provided, of which three are used to acquire the voltages of the first sampling resistor R01 and the second sampling resistor R02 and the voltage output by the signal source 100. As is known, there is a contact resistance between the normally open contact and the normally closed contact of the relay K01, and likewise between the two connection points at which the switching device 200 is connected to the fault line via a conductor. The contact resistance generates voltage division after passing through current, so that the measurement result is influenced, and a fourth and a fifth analog signal acquisition modules 300 are arranged to avoid the influence of the contact resistance.
As shown in fig. 4, the fourth analog signal collecting module 300 is used to collect the voltage between the output terminal of the switching device 200 and the faulty connecting point of the faulty line and the signal pole 101, and the fifth analog signal collecting module 300 collects the voltage between the other output terminal of the switching device 200 and the non-faulty connecting point of the faulty line and the signal pole 101. The contact resistances at the two points are assumed to be voltages of the first contact resistance R03 and the second contact resistance R04. The voltage between the output terminal of the switching device 200 and the fault line fault connection point and the signal electrode 101 is the sum of the voltages of the first contact resistor R03 and the first sampling resistor R01.
Alternatively, as shown in fig. 7, the fourth analog signal collecting module 300 is used to switch the voltage between the first input terminal pole and the first output terminal pole of the apparatus 200 and the faulty phase connection point of the faulty line, and the fifth analog signal collecting module 300 is used to switch the voltage between the second input terminal pole and the second output terminal pole of the apparatus 200 and the non-faulty phase connection point of the faulty line.
In order to be convenient to carry and operate, the utility model discloses still include casing, the test wire of constituteing by box body and lid. An operation panel is arranged in the box body. The signal source 100, the switching device 200, and the controller 400 are disposed at a lower portion of the operation panel. The operation panel is embedded with a display, a switch and a test wire jack. The display is electrically connected to the controller 400.
The test line jacks include two signal output jacks and two signal acquisition jacks, the two signal output jacks are electrically connected with the output end of the switching device 200, and the two signal acquisition jacks are electrically connected with the input ends of the fourth and fifth analog signal acquisition modules 300. The test wire comprises a pincer-shaped jointing clamp. Two wires are respectively led out from two clamp arms of the clamp-shaped jointing clamp, plugs are arranged at the end parts of the two wires, one of the wires is used for being connected with the signal output jack in an inserting mode, and the other wire is used for being connected with the signal acquisition jack in an inserting mode. When the test wire is connected with a fault line, the clamp-shaped jointing clamp is clamped on a cable or a copper bar, and the other ends of the two leads of the test wire are respectively inserted into the corresponding signal output jack and the signal acquisition jack.
In this embodiment, a method for performing ground fault point ranging by using an electric power overhead line ground fault ranging device includes the following steps:
step 1 is the same as in example 1.
Step 2, starting the signal source 100 to output a high-voltage low-frequency alternating current power supply signal, collecting the voltage output by the signal source 100, and converting the voltage into a phasor
Wherein
The initial phase of (2) is 0 deg.. The voltage values of the first sampling resistor R01 and the second sampling resistor R02 before the switching device 200 is switched are collected and converted into the voltage values by taking the output voltage of the signal source 100 as the referenceVoltage phasor
Collecting the voltage between the fault connection point of one pole of the output end of the switching device 200 and the ground fault line and the signal pole 101 and taking the output voltage of the signal source 100 as the reference
Collecting the voltage between the other pole of the output end of the switching device 200 and the non-fault phase connection point of the ground fault line and the signal pole 101, and converting the voltage into a voltage phasor by taking the output voltage of the signal source 100 as a reference
The signal source 100 is then stopped.
Wherein
Step 3, starting the switching device 200, then starting the signal source 100 to output a high-voltage low-frequency alternating-current power supply signal, collecting the voltage output by the signal source 100, and converting the voltage into phasor
Wherein
The initial phase of (2) is 0 deg.. The voltage values of the first sampling resistor R01 and the second sampling resistor R02 before the switching device 200 switches are collected and converted into voltage phasors by taking the output voltage of the signal source 100 as a reference
Collecting the voltage between the fault connection point of one pole of the output end of the switching device 200 and the ground fault line and the signal pole 101 and taking the output voltage of the signal source 100 as the reference
Collecting the voltage between the other pole of the output end of the switching device 200 and the non-fault phase connection point of the ground fault line and the signal pole 101, and converting the voltage into a voltage phasor by taking the output voltage of the signal source 100 as a reference
The signal source 100 is then stopped.
Wherein
And 4, listing equations according to the principle that the voltages of the parallel circuits are equal by using the voltage parameters acquired in the step 2 and the step 3, forming a linear equation system by using the two equations, and calculating the resistance values of the front-section resistor Rak, the rear-section resistor Rkb and the total resistor Rab. The method specifically comprises the following steps:
after the phasor values of the voltage values in step 2 are obtained, phasor calculation can be performed, and then a real part and an imaginary part are separated from the calculated phasor value result, wherein the real part is the resistance of the power transmission line. Or, obtaining the resistive component of the voltage value by the quadrature calculation of the acquired phasor value, and then calculating by using the resistive component of the voltage. The latter is also taken as an example in this example:
as shown in fig. 5, before the switching device 200 switches, the first sampling resistor R01 is connected to the failed phase, and the contact resistor thereof is the second contact resistor R04, and the second sampling resistor R02 is connected to the non-failed phase, and the contact resistor thereof is the first contact resistor R03.
In this state:
the current flowing through the non-faulted phase,
I12＝U12cosβ1/R02
(9)
current flowing through fault phase
I11＝U11cosα1/R01
(10)
At this time, according to the principle that the voltages at both ends of the two parallel circuits are equal, and the equations are listed as follows in conjunction with equation (9) and equation (10),
U13cosδ1+(U11cosα1/R01)Rak＝U14cosε1+(U12cosβ1/R02)(Rak+2Rkb) (11)
as shown in fig. 6, after the switching device 200 switches, the first sampling resistor R01 is connected to the non-fault phase, and the contact resistor thereof is the first contact resistor R03, and the second sampling resistor R02 is connected to the fault phase, and the contact resistor thereof is the second contact resistor R04.
In this state:
the current flowing through the non-faulted phase,
I21＝U21cosα2/R01(12)
current flowing through fault phase
I22＝U22cosβ2/R02(13)
At this time, according to the principle that the voltages at both ends of the two parallel circuits are equal, and the equations are listed as follows in conjunction with the formula (12) and the formula (13),
U23cosδ2+(U22cosβ2/R02)Rak＝U24cosε2+(U21cosα2/R01)(Rak+2Rkb) (14)
and (3) forming a linear equation system of two variables by using the two equations of the formula (11) and the formula (14), and calculating the resistance values of the front-section resistor Rak, the rear-section resistor Rkb and the total resistor Rab.
It is also possible to calculate using a phasor method, where the line impedance from the ground fault point to the head end of the ground fault phase is the forward-stage impedance Xak with a reactance value of
The line impedance from the ground fault point to the end of the ground fault phase is the back-end impedance Xkb with an impedance value of
Calculate out
And
after resistance value, the reactance is separated
The real part of, i.e. the resistance of, the line is Rak＝|X|cosφ。
Step 5 is the same as step 5 in example one.
EXAMPLE III
On the basis of the embodiment, as shown in fig. 7, the fourth analog signal acquisition module 300 acquires the voltage between the signal output end of the first sampling resistor R01, the switching device 200 and the non-fault phase connection point; the fifth analog signal acquisition module 300 acquires voltages between the signal output end of the second sampling resistor R02, the switching device 200 and the fault phase connection point. Then, in step 4, the equations are set out, and the resistances of the front-stage resistor Rak and the rear-stage resistor Rkb are solved.
In summary, the present invention is only a preferred embodiment, and is not intended to limit the scope of the present invention, and various changes and modifications can be made by workers in the field without departing from the technical spirit of the present invention. The technical scope of the present invention is not limited to the content of the specification, and all the equivalent changes and modifications of the shape, structure, characteristics and spirit according to the scope of the present invention should be included in the scope of the claims of the present invention.
Claims (8)
1. An electric power overhead line ground fault ranging device, comprising a controller (400), characterized in that:
also comprises a signal source (100) electrically connected with the controller (400), a switching device (200), a first sampling resistor (R01) and a second sampling resistor (R02),
the output end of the signal source (100) outputs a high-voltage low-frequency alternating current power supply signal, two poles of the output end of the signal source (100) are a signal pole (101) and a grounding pole (102), the grounding pole (102) is grounded,
the switching device (200) is a reversing circuit formed by a relay (K01), the controller (400) is electrically connected with the relay (K01) of the switching device (200),
one end of the first sampling resistor (R01) and one end of the second sampling resistor (R02) are respectively and electrically connected with the signal electrode (101),
the other ends of the first sampling resistor (R01) and the second sampling resistor (R02) are respectively and electrically connected with two poles of the input end of the switching device (200), two poles of the output end of the switching device (200) are respectively used for connecting a fault phase and any non-fault phase at the head end of a ground fault line,
the controller (400) provides original data for calculating the distance of the fault point by acquiring the voltage values of the first sampling resistor (R01), the second sampling resistor (R02) and the voltage value output by the signal source (100) in the two states before and after switching of the switching device (200),
the first sampling resistor (R01) and the second sampling resistor (R02) are different in resistance value.
2. An electric overhead line ground fault location device of claim 1, wherein:
the frequency of the high-voltage low-frequency alternating current power supply signal generated by the signal source (100) is 0.5 Hz-15 Hz, and the maximum output voltage is 80% -110% of the rated voltage of the overhead line.
3. An electric overhead line ground fault location device of claim 2, wherein:
the frequency of the high-voltage low-frequency alternating current power supply signal generated by the signal source (100) is 1 Hz-5 Hz, and the maximum output voltage is 85% -100% of the rated voltage of the overhead line.
4. An electric overhead line ground fault location device of claim 1, wherein:
the first sampling resistor (R01) and the second sampling resistor (R02) are precision resistors.
5. An electric overhead line ground fault location device of claim 1, wherein:
the controller (400) is provided with three analog signal acquisition modules (300) for acquiring the voltage output by the signal source (100) and the voltages of the first sampling resistor (R01) and the second sampling resistor (R02).
6. An electric overhead line ground fault location device of claim 1, wherein:
the controller (400) is provided with five analog signal acquisition modules (300),
wherein the three analog signal acquisition modules (300) are used for acquiring the voltages of the first sampling resistor (R01), the second sampling resistor (R02) and the voltage output by the signal source (100),
the fourth analog signal acquisition module (300) is used for acquiring the voltage between the signal pole (101) and one pole of the output end of the switching device (200) and the fault connection point of the ground fault line,
and the fifth analog signal acquisition module (300) is used for acquiring the voltage between the other pole of the output end of the switching device (200) and the non-fault connection point of the ground fault line and the signal pole (101).
7. An electric overhead line ground fault location device of any one of claims 1-6, wherein:
the short connecting piece is a lead with jointing clamps at two ends.
8. An electric overhead line ground fault location device of claim 6, wherein:
comprises a shell body and a test wire, wherein the shell body is composed of a box body and a box cover, an operation panel is arranged in the box body, a signal source (100), a switching device (200) and a controller (400) are arranged at the lower part of the operation panel, a display, a switch and a test wire jack are embedded on the operation panel, the display is electrically connected with the controller (400),
the test line jacks comprise two signal output jacks and two signal acquisition jacks, the two signal output jacks are electrically connected with the output end of the switching device (200), the two signal acquisition jacks are electrically connected with the input ends of a fourth analog signal acquisition module and a fifth analog signal acquisition module (300),
the test wire comprises a pincerlike jointing clamp, two wires are respectively led out from two clamp arms of the pincerlike jointing clamp, plugs are arranged at the end parts of the two wires, one of the wires is used for being connected with the signal output jack in an inserting mode, and the other wire is used for being connected with the signal acquisition jack in an inserting mode.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201921185713.4U CN210690719U (en) | 2019-07-25 | 2019-07-25 | Electric power overhead line ground fault range unit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921185713.4U CN210690719U (en) | 2019-07-25 | 2019-07-25 | Electric power overhead line ground fault range unit |
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| CN201921185713.4U Active CN210690719U (en) | 2019-07-25 | 2019-07-25 | Electric power overhead line ground fault range unit |
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| Country | Link |
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| CN (1) | CN210690719U (en) |
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