CN114518533B - Hybrid direct-current circuit breaker locking time measuring method based on electromagnetic field synchronous measurement - Google Patents
Hybrid direct-current circuit breaker locking time measuring method based on electromagnetic field synchronous measurement Download PDFInfo
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Abstract
The invention belongs to the technical field of electromagnetic field measurement and high-voltage direct-current circuit breakers, and discloses a method for measuring the locking time of a hybrid direct-current circuit breaker based on electromagnetic field synchronous measurement, the method is based on a switch transient electromagnetic field synchronous measurement probe of a symmetrical double-gap loop antenna to realize synchronous measurement of a switch transient electromagnetic field generated by the operation of a circuit breaker in a converter station, since the locking of the main branch of the hybrid dc circuit breaker does not cause a significant change in the voltage of the circuit breaker and its lines, however, the strong magnetic field pulse is induced around the breaker in the current transfer process, so that the locking time of the main branch can be accurately measured only by measuring the magnetic field pulse around the breaker, and the blocking of the transfer branch can cause the rapid change of the voltage at two ends of the circuit breaker, so the blocking time of the transfer branch can be accurately measured by measuring the electric field pulse at the periphery of the circuit breaker.
Description
Technical Field
The invention belongs to the technical field of electromagnetic field measurement and high-voltage direct-current circuit breakers, and relates to a method for measuring the locking time of a hybrid direct-current circuit breaker based on electromagnetic field synchronous measurement.
Background
The damping of a direct current transmission system is much lower than that of an alternating current transmission system, so when a short-circuit fault occurs, the rising rate of a short-circuit current is very high, the short-circuit current can reach a peak value within several milliseconds, and if relay protection operation is not carried out in time, the converter valve can be burnt. The development of short-circuit currents is normally limited by blocking the converter valves in the converter station, but the short-circuit currents cannot be completely interrupted by the effect of the freewheeling diodes in the converter valves, and therefore, it is also necessary to open the ac-side circuit breakers. The action time of the alternating-current side circuit breaker is often more than ten-odd milliseconds, and short-circuit faults cannot be removed quickly. Therefore, a direct current breaker needs to be installed in the converter station to quickly cut off the short-circuit current of the direct current line, reduce the fault current level of the direct current transmission system, and limit the fault diffusion area. And the direct current circuit breaker can also realize quick electrified switching on and off of the converter station and the line, and can quickly start the system after the fault is quickly cleared. At present, direct current circuit breakers can be divided into three categories: the hybrid direct-current circuit breaker combines the advantages of mechanical and all-solid-state direct-current circuit breakers, is widely applied and concerned in practical engineering, and is practically applied to a Zhoushan five-end flexible-straight system and a Zhang-north four-end flexible-straight system in China. A schematic block diagram of a hybrid dc circuit breaker is shown in fig. 2.
As can be seen from fig. 2, the hybrid dc circuit breaker includes three branches, namely a main branch, a transfer branch and an energy consumption branch, where the breaking of the short-circuit current is the core function of the circuit breaker, and the breaking process of the hybrid dc circuit breaker can be divided into two current transfer processes. Under the normal state, heavy current is carried by the main branch road, when needing to be broken, the semiconductor solid-state switch in the main branch road is firstly disconnected, current can flow to the transfer branch road, then the quick mechanical switch in the main branch road is disconnected, when the mechanical switch is separated by enough distance to bear direct current high voltage, the transfer branch road is locked, the current can be forced to flow to the energy consumption branch road, then the metal oxide lightning arrester in the energy consumption branch road can be punctured, the energy stored in the inductor in the direct current system is consumed, and when the metal oxide lightning arrester is recovered to the insulation state, the breaking process of the circuit breaker is completed.
The whole breaking process of the hybrid direct-current circuit breaker is completed within a few milliseconds, the action of the quick mechanical switch is divided into slow breaking and fast breaking, the slow breaking is generally adopted for breaking of small current, and the fast breaking is adopted when large short-circuit current needs to be cut off. The alternating current system has large damping, slow development of fault current and low requirements on the breaking time of the circuit breaker. However, the damping of the dc system is small, the fault current develops quickly, and the requirement on the action time of the hybrid dc short-circuiting device is very accurate, so that the main branch locking time and the branch transferring locking time need to be measured accurately, and if the branch locking time is measured inaccurately or shakes too much, the reliable operation of the hybrid dc circuit breaker cannot be guaranteed.
At present, a self-contained state monitoring system in a direct current circuit breaker and a self-contained voltage and current wave recording system in a converter station are generally adopted for judging the locking time of a main branch and a transfer branch of a hybrid direct current circuit breaker, however, the self-contained wave recording system in the converter station aims at direct current and low-frequency signals, the measurement bandwidth is limited, the sampling rate is generally not more than 10ksps, and the measurement error of the action time of the circuit breaker can reach more than 0.1 ms.
Therefore, a method capable of measuring the action time of the direct current circuit breaker from the external voltage and current changes is needed, on one hand, the defects that the voltage and current monitoring system in the converter station is low in sampling rate and limited in bandwidth are overcome, and on the other hand, the method is used as a verification method for the monitoring system of the hybrid direct current circuit breaker.
The hybrid direct current circuit breaker can cause the sudden change of system voltage and current in the operation process, the current conversion generated when the main branch is locked can cause the strong magnetic field pulse, the voltage sudden change generated when the branch is transferred is locked can generate the strong electric field and the strong magnetic field pulse, the 'switch transient electromagnetic field' belongs to an electromagnetic disturbance for the secondary control equipment of the circuit breaker and can interfere the normal work of the circuit breaker, and therefore the transient electric field and the magnetic field pulse need to be measured and researched.
Because the transient electromagnetic field has the characteristics of short duration, fast rising edge and wide frequency band, an electric small antenna is generally used as a measuring tool, for example, a D-dot antenna or a dipole antenna is often used for measuring electric field pulses, and a small loop antenna is often used for measuring magnetic field pulses; of course, there are also optical fiber sensors based on electro-optical effect and magneto-optical effect for measuring transient electric field and transient magnetic field or giant magnetoresistance sensors for measuring transient magnetic field.
However, the existing electromagnetic field sensor can only be used for measuring one field quantity of an electric field or a magnetic field, and cannot synchronously measure the electric field and the magnetic field, and when the electric field antenna and the magnetic field antenna are actually arranged and measured, a certain distance is required to avoid mutual interference between the antennas, so that the measured electric field and the measured magnetic field are not the field quantities at the same point, and the field quantities at the same moment are not actually measured due to the time delay of electromagnetic wave propagation, which brings great inconvenience and errors for the analysis of subsequent electromagnetic pulses.
Disclosure of Invention
The invention aims to provide a method for measuring the locking time of a hybrid direct-current circuit breaker based on electromagnetic field synchronous measurement.
In order to achieve the purpose, the invention adopts the following technical scheme:
the method for measuring the locking time of the hybrid direct current circuit breaker based on electromagnetic field synchronous measurement is realized by adopting a switching transient electromagnetic field synchronous measuring probe based on a symmetrical double-gap loop antenna, and comprises the following steps:
the axis of the symmetrical double-gap loop antenna is parallel to the ground, and the connecting line of two gaps of the symmetrical double-gap loop antenna is parallel to the direction from the incoming line to the outgoing line of the hybrid direct-current circuit breaker;
step 2, connecting a magnetic field signal output end and an electric field signal output end of the switching transient electromagnetic field synchronous measuring probe to a wave recorder in the shielding chamber through an output coaxial cable respectively;
one output coaxial cable connected with the magnetic field signal output end is connected to a channel 1 of the wave recorder, and the other output coaxial cable connected with the electric field signal output end is connected to a channel 2 of the wave recorder;
wherein, the lengths of the two output coaxial cables are equal;
meanwhile, according to the recording signals of the original voltage and current wave recording system in the converter station, voltage and current signals of incoming lines and outgoing lines at two ends of the hybrid direct-current circuit breaker are drawn on the same coordinate axis;
step 7, accurately judging the locking time of the hybrid direct current circuit breaker according to the switch transient electromagnetic field signal, wherein the recorded initial time of the magnetic field pulse is used as the locking time of the main branch circuit; obvious electric field pulse can appear 2-10 ms after the locking time of the main branch, which is generated by the locking of the transfer branch, and the starting time of the electric field pulse is taken as the locking time of the transfer branch;
further comparing the locking time of the main branch circuit measured in the step 7 with the locking time of the main branch circuit roughly measured in the step 6, and if the difference between the two times is not more than 1ms, considering that the measurement result of the locking time of the main branch circuit of the hybrid direct current circuit breaker obtained based on the electromagnetic field synchronous measurement is real;
if the difference between the locking time of the main branch measured in the step 7 and the locking time of the main branch roughly measured in the step 6 exceeds 1ms, the locking time of the main branch obtained in the step 6 is taken as a time reference, a magnetic field pulse with the time difference of not more than 1ms with the locking time of the main branch obtained in the step 6 is searched on the magnetic field pulse sequence measured in the step 7, the starting time of the magnetic field pulse is taken as the locking time of the main branch, and similarly, an obvious electric field pulse can appear 2-10 ms after the locking time of the main branch, and is generated by the locking of the transfer branch, and the starting time of the electric field pulse is taken as the locking time of the transfer branch.
The invention has the following advantages:
as described above, the present invention provides a method for measuring the latching time of a hybrid dc circuit breaker based on electromagnetic field synchronous measurement, which includes introducing a switching transient electromagnetic field synchronous measurement probe capable of synchronously measuring the transient electric field and the magnetic field pulse generated during the operation of the circuit breaker, further distinguishing the magnetic field pulse generated by the latching of the main branch and the electric field pulse generated by the latching of the transfer branch based on the synchronous measurement probe, and then accurately measuring the latching time of the main branch and the transfer branch at the starting time of the magnetic field and the electric field pulse.
Drawings
Fig. 1 is an installation schematic diagram of a hybrid dc circuit breaker locking time measuring method based on electromagnetic field synchronous measurement in the embodiment of the present invention;
fig. 2 is a functional block diagram of a hybrid dc circuit breaker;
FIG. 3 is a schematic diagram of a symmetric dual gap loop antenna for synchronous measurement of electromagnetic fields in an embodiment of the present invention;
FIG. 4 is a schematic diagram of a symmetrical dual gap ring antenna according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a first antenna assembly according to an embodiment of the present invention;
FIG. 6 is a schematic structural view of a nylon support according to an embodiment of the present invention;
fig. 7 is a circuit structure diagram of the switching transient electromagnetic field synchronous measurement probe in the embodiment of the invention.
The antenna comprises a first antenna assembly, a second antenna assembly, a main antenna assembly section, a 4-antenna assembly leading-out section, an inner conductor, an outer conductor, a 7-first gap, a 8-second gap, a 9-nylon supporting piece, a 10-circular ring-shaped clamping groove, an 11-round hole, a 12-symmetrical double-gap ring antenna, a 13-electromagnetic field separation circuit, a 14-first power divider, a 15-second power divider, a 16-magnetic field signal output coaxial cable, a 17-electric field signal output coaxial cable, an 18-probe and a 19-oscillograph, wherein the first antenna assembly, the 2-second antenna assembly, the 3-antenna assembly main body section, the 4-antenna assembly leading-out section, the 5-inner conductor, the 6-outer conductor, the 7-first gap, the 8-second gap, the 9-nylon supporting piece, the 10-circular ring-shaped clamping groove, the 11-round hole, the 12-symmetrical double-gap ring antenna, the 13-electromagnetic field separation circuit, the 14-first power divider, the 15-second power divider, the 16-magnetic field signal output coaxial cable, the 17-electric field signal output coaxial cable, the 18-probe and the 19-oscillograph.
Detailed Description
The basic concept of the invention is as follows: firstly, a synchronous measurement probe of a switching transient electromagnetic field based on a symmetrical double-gap loop antenna is provided to realize the synchronous measurement of the switching transient electromagnetic field generated by the operation of a circuit breaker in a converter station, because the locking of a main branch of a hybrid direct current circuit breaker can not cause the voltage of the circuit breaker and a circuit thereof to generate obvious change, but the transfer process of current can induce strong magnetic field pulse at the periphery of the circuit breaker, the locking time of the main branch can be accurately measured only by measuring the magnetic field pulse at the periphery of the circuit breaker, and the locking of the transfer branch can cause the rapid change of the voltage at two ends of the circuit breaker, therefore, the locking time of the transfer branch can be accurately measured by measuring the electric field pulse at the periphery of the circuit breaker.
Based on the above inventive concept, the invention firstly designs a switching transient electromagnetic field synchronous measurement probe based on a symmetrical double-gap loop antenna, as shown in fig. 7. As shown in fig. 7, the switching transient electromagnetic field synchronous measurement probe in this embodiment includes a symmetric double-gap loop antenna 12 and an electromagnetic field separation circuit 13.
As shown in fig. 3, the principle of the symmetric double-gap loop antenna 12 for synchronous measurement of the electric field and the magnetic field is as follows:
the antenna is designed into a circular symmetrical double-gap ring antenna, and two gaps are arranged at symmetrical positions.
Two gaps are defined as a first gap and a second gap respectively.
In practical use, the size of the antenna is required to be far smaller than the wavelength of the electromagnetic field to be measured so as to ensure that the antenna belongs to an electrically small antenna, and then the electromagnetic field around the antenna can be regarded as a uniform electromagnetic field.
The electric field induced by the symmetric double-gap loop antenna can be divided into two parts:
one part is the original electric field in space, denoted as EOriginal electric fieldThe double gap loop antenna is equivalent to two parallel dipole antennas for the "original electric field" corresponding to the real electric field at the measuring point. Therefore, in FIG. 3, two voltages V with the same magnitude and the same direction can be induced at the first gap and the second gapElectric field 1And VElectric field 2。
The other part of the electric field is an induced electric field generated by the change of the magnetic flux passing through the small ring area and is marked as EInduced electric fieldThe electric field is spiral, so that two voltages V with equal magnitude and opposite directions can be induced at the first gap and the second gap in FIG. 3Magnetic field 1And VMagnetic field 2。
The voltage actually measured at the first and second gaps of the symmetrical double-gap loop antenna is the voltage V1And a voltage V2Then, according to the positive voltage direction (positive left and negative right) labeled in fig. 3, there are:
V1= Velectric field 1- VMagnetic field 1，V2= VElectric field 2+ VMagnetic field 2。
Therefore, the method comprises the following steps: vElectric field=(V1+ V2)/2，VMagnetic field=(V2-V1)/2。
Therefore, the voltages V1 and V2 at the two gaps of the symmetrical double-gap loop antenna are measured, and then signal processing such as power distribution, addition and subtraction processing, signal amplification and the like is carried out, so that the quantity which is in a linear relation with the electric field and the magnetic field can be obtained, and synchronous measurement of the electric field and the magnetic field can be realized through one antenna.
The structure of the symmetric dual gap ring antenna in the embodiments of the present invention is discussed in detail below.
As shown in fig. 4, the symmetric dual-gap loop antenna in this embodiment includes a first antenna component 1 and a second antenna component 2, where the first antenna component 1 and the second antenna component 2 have the same structure.
Taking the structure of the first antenna assembly 1 as an example, it is shown in fig. 5.
The first antenna assembly 1 includes an antenna assembly main body section 3 and an antenna assembly outgoing section 4, wherein the antenna assembly main body section 3 is a semicircular ring shape, and the antenna assembly main body section 3 is connected with the antenna assembly outgoing section 4.
The antenna assembly main body section 3 and the antenna assembly leading-out section 4 are preferably formed by bending the same coaxial cable, and the antenna assembly main body section 3 and the antenna assembly leading-out section 4 are obtained after bending.
At one end I of the antenna component main body section 3 away from the antenna component lead-out section 4, the inner conductor 5 of the antenna component main body section 3 protrudes from the end surface a of the outer conductor 6, i.e. the inner conductor is exposed to the outside of the outer conductor.
The second antenna component 2 has the same structure as the first antenna component 1 and will not be described in detail here.
As shown in fig. 4, the inner conductor 5 of the first antenna component 1 exposed to the outside (i.e., the inner conductor 5 whose I end protrudes from the outer conductor 6) is connected to the outer conductor 6 of the second antenna component 2 at a connection position B where the antenna component main body section 3 of the second antenna component 2 is connected to the antenna component lead-out section 4 by soldering.
A first gap 7 is formed between the end face a of the antenna element main body section of the first antenna element 1 where the outer conductor is located and the junction B of the antenna element main body section of the second antenna element and the antenna element lead-out section.
As shown in fig. 4, the inner conductor 5 of the second antenna component 2 exposed to the outside (i.e., the inner conductor 5 whose I end protrudes from the outer conductor 6) is connected to the outer conductor 6 of the first antenna component 1 at a connection position C where the antenna component main body section 3 of the first antenna component 2 is connected to the antenna component lead-out section 4 by soldering.
A second gap 8 is formed between the end face a of the antenna-assembly main body section of the second antenna assembly 2 where the outer conductor 6 is located and the junction of the antenna-assembly main body section and the antenna-assembly lead-out section of the first antenna assembly 1.
As known from the faraday electromagnetic shielding principle, the external electric field induces a voltage signal on the outer surface of the outer conductor 6 of the coaxial cable, which is picked up by the inner conductor 5 of the coaxial cable at the corresponding gap and transmitted along the inside of the coaxial cable at (the junction B, C of) the inner conductor 6.
The first antenna component 1 and the second antenna component 2 are in the same plane and are centrosymmetric, and the symmetric double-gap loop antenna formed by combining the first antenna component 1 and the second antenna component 2 is circular.
The influence of the curvature radius of the coaxial cable during bending is limited, two sections of semicircular coaxial cables (the first antenna assembly 1 and the second antenna assembly 2) may not be butted into a standard circular ring, however, the normal operation of the antenna can be ensured only by ensuring that the shapes of the two sections of coaxial cables are completely symmetrical.
The first gap 7 and the second gap 8 are located at the symmetrical positions of the symmetrical double-gap ring antenna.
Therein, the voltage at the first gap 7 may be output through the first antenna component 1 (inner conductor of the coaxial cable), and the voltage at the second gap 8 may be output through the second antenna component 2 (inner conductor of the coaxial cable).
In addition, in order to support the symmetric dual gap ring antenna and ensure the symmetry of the antenna, an antenna support is further configured for the symmetric dual gap ring antenna in this embodiment, as shown in fig. 6.
The antenna support piece comprises two nylon support pieces 9 with the same structure, and one side surface of each nylon support piece 9 is provided with a circular clamping groove 10 which is matched with the symmetrical double-gap-ring antenna in shape and size.
The symmetrical double-gap loop antenna is positioned between the two nylon supporting pieces which are placed up and down and is fixed.
Specifically, the nylon support pieces 9 are square, and the corners of each nylon support piece 9 are provided with mounting holes 11; the two nylon supporting pieces 9 are fixed through nylon bolts sequentially penetrating through the corresponding mounting holes 11.
The supporting effect and symmetry of the symmetrical double-gap loop antenna are ensured through the design.
As shown in fig. 7, the electromagnetic field separating circuit 13, which is used to separate the electric field signal and the magnetic field signal measured by the symmetric double gap loop antenna 12, includes a first power divider 14, a second power divider 15, an adder circuit including an operational amplifier, and a subtractor circuit including an operational amplifier.
The antenna component exit section 4 of the first antenna component 1 is connected to the input of the first power divider 14.
The first power divider 14 is used for outputting a first voltage signal V at the first gap 71Divided into two paths of signals with equal amplitude and same sign, and the amplitude is changed into a first voltage signal V1Is/are as follows
And (4) doubling.
The output end of the first power divider has two paths, and the amplitude of each path of output signal is
V1。
The antenna-component exit section 4 of the second antenna component 2 is connected to the input of a second power divider 15.
Due to the way the signal is picked up at the second gap 8 in fig. 4 and the positive direction of the gap voltage is defined in fig. 7, the second voltage signal output from the second gap 8 should in fact be.
The second power divider 15 is used for dividing the second voltage signal V output at the second gap 82Divided into two paths of signals with equal amplitude and same sign, and the amplitude is changed into a second voltage signal V2Is/are as follows
And (4) doubling.
The output end of the second power divider 15 has two paths, and the amplitude of each path of output signal is-
V2。
The adder circuit has two inputs, one of which is connected to an output of the first power divider 15 and the other of which is connected to an output of the second power divider 15.
The adder circuit is used for realizing the addition operation of the two paths of signals and amplifying the signals.
The output end of the adder circuit is provided with one output end, and the output signal of the adder circuit is a signal obtained by adding and amplifying the output signal of the first power divider and the output signal of the second power divider.
As shown in fig. 7, the adder circuit includes a first resistor R1, a second resistor R2, and a first operational amplifier OPA 1; there are two first resistors R1, one second resistor R2 and one first operational amplifier.
One end of each of the two first resistors R1 is connected to one input terminal of the adder circuit.
The other ends of the two first resistors R1, one end of the second resistor R2 and the inverting input end of the first operational amplifier OPA1 are connected; the non-inverting input of the first operational amplifier OPA1 is connected to ground.
The other end of the second resistor R2 and the output of the first operational amplifier OPA1 are connected to the output of the adder circuit, which is a magnetic field signal output terminal and is connected to the magnetic field signal output coaxial cable 16.
The amplification factor of the first operational amplifier OPA1 is the ratio of the second resistor R2 to the first resistor R1, namely R2/R1, and the amplification factor is in linear proportion to the measured magnetic field signal.
Magnetic field signal output coaxial cable 16 outputs a magnetic field signal of
。
The subtractor circuit has two input terminals, one of which is connected to the other output terminal of the first power divider 14, and the other of which is connected to the other output terminal of the second power divider 15.
The subtracter circuit is used for realizing subtraction operation of the two paths of signals and amplifying the signals.
The output signal of the subtractor circuit is a signal obtained by subtracting and amplifying the output signal of the first power divider 14 and the output signal of the second power divider 15.
As shown in fig. 7, the subtractor circuit includes a first resistor R1, a second resistor R2, and a second operational amplifier OPA 2; two of the first resistor R1 and the second resistor R2 are provided, and one of the second operational amplifiers is provided.
One end of each of the two first resistors R11 is connected with one input end of the subtractor circuit; the other ends of the two first resistors R1 are connected to the inverting input terminal and the non-inverting input terminal of the second operational amplifier OPA2, respectively.
One end of a second resistor R2 is connected with the same-direction input end of the second operational amplifier OPA2, and the other end is grounded; a further second resistor R2 has one terminal connected to the inverting input of the second operational amplifier OPA2 and another terminal connected to the output of the second operational amplifier OPA2 and the output of the subtractor circuit.
The amplification factor of the second operational amplifier OPA2 is the ratio of the second resistor R2 to the first resistor R1, namely R2/R1, and the amplification factor is in linear proportion to the measured electric field signal.
The output end of the subtracter is an electric field signal output end and is connected with an electric field signal output coaxial cable 17. Electric field signal output coaxial cable 17 outputs an electric field signal of
。
The values of R1 and R2 can be adjusted according to the magnitude of the measured signal amplitude to obtain the best measurement effect.
The switching transient electromagnetic field synchronous measurement probe based on the symmetrical double-gap loop antenna is suitable for synchronous measurement of transient electromagnetic fields generated by high-voltage switch operation in a transformer substation and a converter station.
The maximum frequency of the switching transient electromagnetic field in the transformer substation or the converter station is generally below 300 MHz, and the corresponding wavelength is 1 m. To ensure that the symmetric double gap loop antenna 12 is electrically small, the diameter of the antenna in this embodiment should be no greater than 1/10, i.e., 10cm, of the wavelength of the switching transient electromagnetic field.
However, the diameter of the antenna cannot be too small, which increases the processing difficulty and reduces the sensitivity of the antenna.
Therefore, the diameter of the symmetrical double-gap loop antenna 12 in this embodiment should be 5-10 cm.
In addition, the present embodiment further includes a metal shielding box, and the circuit board including the electromagnetic field separating circuit 13 (shown by a dashed line frame in fig. 7) is placed in the small metal shielding box and is powered by a battery.
In the embodiment, by designing the structures of the symmetrical double-gap loop antenna 12 and the electromagnetic field separation circuit 13 in total, synchronous measurement of the electric field and the magnetic field can be realized by using only one probe, so that the measured electric field and the measured magnetic field are field quantities at the same point and the same moment, and accurate measurement and analysis of transient electromagnetic pulses are facilitated.
The switching transient electromagnetic field synchronous measurement probe based on the symmetrical double-gap loop antenna well solves the technical problems that the electric field measurement antenna and the magnetic field measurement antenna are separately arranged, so that the electric field and the magnetic field are inconvenient to be synchronously measured, and further great troubles and errors are brought to the analysis of the switching transient electromagnetic field when the electric field and the magnetic field are separately measured at present.
On the basis of the structure of the switching transient electromagnetic field synchronous measurement probe, the method for measuring the closing time of the hybrid direct current circuit breaker based on electromagnetic field synchronous measurement is explained in detail below.
As shown in fig. 1, the method for measuring the closing time of the hybrid dc circuit breaker based on electromagnetic field synchronous measurement is implemented by using the above switching transient electromagnetic field synchronous measurement probe based on the symmetric double-gap loop antenna, and includes the following steps:
Specifically, the switching transient electromagnetic field synchronous measurement probe based on the symmetrical double-gap loop antenna is erected 1-2 meters above the ground, and the horizontal distance between the probe and the hybrid direct-current circuit breaker is 3-5 meters.
The axis of the symmetrical double-gap loop antenna is parallel to the ground, and the connecting line of the two gaps of the symmetrical double-gap loop antenna is parallel to the direction from the incoming line to the outgoing line of the hybrid direct current circuit breaker.
And 2, respectively connecting the magnetic field signal output end and the electric field signal output end of the switching transient electromagnetic field synchronous measuring probe to a wave recorder 19 in the shielding chamber through an output coaxial cable.
One output coaxial cable connected to the magnetic field signal output end is connected to the channel 1 of the wave recorder, and the other output coaxial cable connected to the electric field signal output end is connected to the channel 2 of the wave recorder.
Wherein, the lengths of the two output coaxial cables are equal.
The wave recorder selected in the embodiment has a time recording function and can be accurate to microsecond level.
And 3, opening the wave recorder, taking the channel 1 of the wave recorder as a trigger channel, setting the trigger level to be higher than the background noise by 20-40 mV, and keeping a single trigger mode.
And 4, a switching transient electromagnetic field generated when the hybrid direct-current circuit breaker operates enables the wave recorder to be triggered, and the acquired switching transient electromagnetic field signals are recorded through the wave recorder.
And 5, uploading the switch transient electromagnetic field signals acquired by the wave recorder to a computer, and drawing a waveform diagram of the electric field signals and the magnetic field signals by taking time as a horizontal axis.
And meanwhile, according to the recording signals of the original voltage and current wave recording system in the converter station, voltage and current signals of incoming lines and outgoing lines at two ends of the hybrid direct-current circuit breaker are drawn on the same coordinate axis.
And 6, firstly, reading the locking time of the main branch of the hybrid direct current circuit breaker and the locking time of the transfer branch according to the voltage and current signals of the original wave recording system in the converter station.
Because the sampling rate of the existing wave recording system in the converter station is very low, and because of the time delay of a long signal transmission link, the method can only roughly read the action time of the hybrid direct current circuit breaker.
Step 7, accurately judging the locking time of the hybrid direct current circuit breaker according to the switch transient electromagnetic field signal, wherein the magnetic field signal channel is used as a trigger channel, but the trigger time is not the locking time of the main branch of the direct current circuit breaker, and the recorded initial time of the magnetic field pulse is used as the locking time of the main branch and is generally advanced by a period of time compared with the trigger time; and 2-10 ms after the locking moment of the main branch, obvious electric field pulse occurs, which is generated by the locking of the transfer branch, and the starting moment of the electric field pulse is taken as the locking moment of the transfer branch.
Sometimes, the measurement system is affected by accidental electromagnetic interference (such as electromagnetic pulse generated by partial discharge), and in order to eliminate the interference of the electromagnetic interference on the measurement of the locking moment of the main branch, the following steps are also designed:
and further comparing the locking time of the main branch circuit measured in the step 7 with the locking time of the main branch circuit roughly measured in the step 6, and if the difference between the locking time of the main branch circuit and the locking time of the main branch circuit does not exceed 1ms, determining that the measurement result of the locking time of the main branch circuit of the hybrid direct current circuit breaker obtained based on the electromagnetic field synchronous measurement is real.
If the difference between the locking time of the main branch measured in the step 7 and the locking time of the main branch roughly measured in the step 6 exceeds 1ms, the locking time of the main branch obtained in the step 6 is taken as a time reference, a magnetic field pulse with the time difference of not more than 1ms with the locking time of the main branch obtained in the step 6 is searched on the magnetic field pulse sequence measured in the step 7, the starting time of the magnetic field pulse is taken as the locking time of the main branch, similarly, an obvious electric field pulse can appear 2-10 ms after the locking time of the main branch, and the electric field pulse is generated by the locking of the transfer branch, and the starting time of the electric field pulse is taken as the locking time of the transfer branch.
According to the method, the switching transient electromagnetic field is used as the measurement basis of the branch circuit locking time of the hybrid direct-current circuit breaker, and tests prove that the measurement error of the branch circuit locking time can be reduced to be within 5 mu s, so that the measurement accuracy of the method is obviously improved compared with that of the traditional measurement method.
It should be understood, however, that the description herein of specific embodiments is by way of illustration only, and not by way of limitation, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.
Claims (9)
1. The method for measuring the locking time of the hybrid direct current circuit breaker based on electromagnetic field synchronous measurement is characterized by being realized by adopting a switching transient electromagnetic field synchronous measurement probe based on a symmetrical double-gap loop antenna, and comprises the following steps of:
step 1, before the operation of the circuit breaker, a switch transient electromagnetic field synchronous measuring probe based on a symmetrical double-gap loop antenna is arranged at the side of the hybrid direct current circuit breaker and close to the main branch and the transfer branch of the hybrid direct current circuit breaker;
the axis of the symmetrical double-gap loop antenna is parallel to the ground, and the connecting line of two gaps of the symmetrical double-gap loop antenna is parallel to the direction from the incoming line to the outgoing line of the hybrid direct-current circuit breaker;
step 2, connecting a magnetic field signal output end and an electric field signal output end of the switching transient electromagnetic field synchronous measuring probe to a wave recorder in the shielding chamber through an output coaxial cable respectively;
one output coaxial cable connected with the magnetic field signal output end is connected to a channel 1 of the wave recorder, and the other output coaxial cable connected with the electric field signal output end is connected to a channel 2 of the wave recorder;
wherein, the lengths of the two output coaxial cables are equal;
step 3, opening the wave recorder, taking the channel 1 of the wave recorder as a trigger channel, setting the trigger level to be 20-40 mV higher than the background noise, and keeping a single trigger mode;
step 4, a switching transient electromagnetic field generated when the hybrid direct current breaker operates enables the wave recorder to be triggered, and the acquired switching transient electromagnetic field signals are recorded through the wave recorder;
step 5, uploading the switch transient electromagnetic field signals acquired by the wave recorder to a computer, and drawing a waveform diagram of the electric field signals and the magnetic field signals by taking time as a horizontal axis;
meanwhile, according to the recording signals of the original voltage and current wave recording system in the converter station, voltage and current signals of incoming lines and outgoing lines at two ends of the hybrid direct-current circuit breaker are drawn on the same coordinate axis;
step 6, firstly, reading the locking time of a main branch of the hybrid direct current circuit breaker and the locking time of a transfer branch according to voltage and current signals of an original wave recording system of the converter station;
step 7, accurately judging the locking time of the hybrid direct current circuit breaker according to the switch transient electromagnetic field signal, wherein the recorded initial time of the magnetic field pulse is used as the locking time of the main branch circuit; obvious electric field pulse can appear 2-10 ms after the locking time of the main branch, which is generated by the locking of the transfer branch, and the starting time of the electric field pulse is taken as the locking time of the transfer branch;
comparing the locking time of the main branch circuit measured in the step 7 with the locking time of the main branch circuit roughly measured in the step 6, and if the difference between the two times is not more than 1ms, determining that the measurement result of the locking time of the main branch circuit of the hybrid direct current circuit breaker obtained based on the electromagnetic field synchronous measurement is real;
if the difference between the locking time of the main branch measured in the step 7 and the locking time of the main branch roughly measured in the step 6 exceeds 1ms, taking the locking time of the main branch obtained in the step 6 as a time reference, searching a magnetic field pulse which has a time difference of no more than 1ms with the locking time of the main branch obtained in the step 6 on the magnetic field pulse sequence measured in the step 7, taking the initial time of the magnetic field pulse as the locking time of the main branch, and similarly, obvious electric field pulses can appear 2-10 ms after the locking time of the main branch, and are generated by the locking of the transfer branch, and taking the initial time of the electric field pulse as the locking time of the transfer branch.
2. The method for measuring the closing time of a hybrid direct current breaker based on the electromagnetic field synchronous measurement as claimed in claim 1,
the switching transient electromagnetic field synchronous measuring probe based on the symmetrical double-gap loop antenna comprises a symmetrical double-gap loop antenna and an electromagnetic field separating circuit;
a symmetric dual-gap loop antenna comprising a first antenna component and a second antenna component;
the first antenna assembly and the second antenna assembly have the same structure and respectively comprise an antenna assembly main body section and an antenna assembly leading-out section, and the antenna assembly main body section is connected with the antenna assembly leading-out section;
the antenna assembly main body section and the antenna assembly leading-out section are formed by bending the same coaxial cable;
wherein the antenna assembly body segment is semi-circular;
at one end of the antenna component main body segment, which is far away from the antenna component leading-out segment, the inner conductor of the antenna component main body segment protrudes out of the end surface where the outer conductor is located, namely the inner conductor is exposed out of the outer conductor;
the inner conductor exposed outside of the first antenna component is connected to the outer conductor of the second antenna component, and the connection position of the first antenna component is located at the connection position of the antenna component main body segment and the antenna component leading-out segment of the second antenna component;
a first gap is formed between the end surface of the antenna component main body segment of the first antenna component, and the connection position of the antenna component main body segment and the antenna component leading-out segment of the second antenna component;
the inner conductor exposed outside of the second antenna component is connected with the outer conductor of the first antenna component, and the connection position of the second antenna component is positioned at the connection position of the antenna component main body segment and the antenna component leading-out segment of the first antenna component;
a second gap is formed between the end surface of the antenna component main body segment of the second antenna component, and the connection position of the antenna component main body segment and the antenna component leading-out segment of the first antenna component;
the first antenna component and the second antenna component are positioned in the same plane and are centrosymmetric, and a symmetrical double-gap ring antenna formed by combining the first antenna component and the second antenna component is in a circular ring shape;
the first gap and the second gap are positioned at two symmetrical positions of the symmetrical double-gap loop antenna;
the electromagnetic field separation circuit comprises a first power divider, a second power divider, an adder circuit comprising an operational amplifier and a subtractor circuit comprising an operational amplifier;
the leading-out section of the antenna component of the first antenna component is connected to the input end of the first power divider, and the leading-out section of the antenna component of the second antenna component is connected to the input end of the second power divider;
the output end of the first power divider is provided with two paths, the amplitude values of the two paths of output signals are equal, the signs of the two paths of output signals are the same, and the amplitude value of each path of output signal is the first voltage signal output by the first gap
Doubling;
the output end of the second power divider has two paths, the amplitudes of the two paths of output signals are equal, the signs of the two paths of output signals are the same, and the amplitude of each path of output signal is the second voltage signal output at the second gap
Doubling;
the adder circuit has two input ends, one input end is connected with one output end of the first power divider, and the other input end is connected with one output end of the second power divider;
the output end of the adder circuit is provided with one, and the output signal of the adder circuit is a signal obtained by adding and amplifying the output signal of the first power divider and the output signal of the second power divider;
the input ends of the subtractor circuit are two, one input end is connected with the other output end of the first power divider, and the other input end is connected with the other output end of the second power divider;
the output end of the subtractor circuit is provided with one, and the output signal of the subtractor circuit is a signal obtained by subtracting and amplifying the output signal of the first power divider and the output signal of the second power divider;
the output end of the adder is a magnetic field signal output end, and the output end of the subtracter is an electric field signal output end.
3. The method for measuring the closing time of a hybrid direct current breaker based on the electromagnetic field synchronous measurement as claimed in claim 2,
the symmetrical double-gap loop antenna is also provided with an antenna support;
the antenna support piece comprises two nylon support pieces with the same structure, and one side surface of each nylon support piece is provided with a circular clamping groove which is matched with the symmetrical double-gap-ring antenna in shape and size;
the symmetrical double-gap loop antenna is positioned between the two nylon supporting pieces which are placed up and down and is fixed.
4. The hybrid direct current breaker locking time measuring method based on electromagnetic field synchronous measurement according to claim 3,
the nylon support pieces are square, and the corners of each nylon support piece are provided with mounting holes; and the two nylon supporting pieces are fixed by nylon bolts sequentially penetrating through the corresponding mounting holes.
5. The method for measuring the closing time of a hybrid direct current breaker based on the electromagnetic field synchronous measurement as claimed in claim 2,
the diameter of the symmetrical double-gap loop antenna is 5-10 cm.
6. The method for measuring the closing time of a hybrid direct current breaker based on the electromagnetic field synchronous measurement as claimed in claim 2,
the adder circuit comprises a first resistor, a second resistor and a first operational amplifier; the number of the first resistors is two, and the number of the second resistors and the number of the first operational amplifiers are one;
one ends of the two first resistors are respectively connected with one input end of the adder circuit;
the other ends of the two first resistors, one end of the second resistor and the reverse input end of the first operational amplifier are connected; the same-direction input end of the first operational amplifier is grounded;
the other end of the second resistor and the output end of the first operational amplifier are connected with the output end of the adder circuit;
the amplification factor of the first operational amplifier is the ratio of the second resistor to the first resistor.
7. The method for measuring the closing time of a hybrid direct current breaker based on the electromagnetic field synchronous measurement as claimed in claim 2,
the subtractor circuit comprises a first resistor, a second resistor and a second operational amplifier; the number of the first resistors and the number of the second resistors are two, and the number of the second operational amplifiers is one;
one end of each of the two first resistors is connected with one input end of the subtractor circuit; the other ends of the two first resistors are respectively connected to the reverse input end and the same-direction input end of the second operational amplifier;
one end of a second resistor is connected with the homodromous input end of the second operational amplifier, and the other end of the second resistor is grounded;
one end of the other second resistor is connected with the reverse input end of the second operational amplifier, and the other end of the other second resistor is connected with the output end of the second operational amplifier and the output end of the subtractor circuit;
the amplification factor of the second operational amplifier is the ratio of the second resistor to the first resistor.
8. The method for measuring the closing time of a hybrid direct current breaker based on the electromagnetic field synchronous measurement as claimed in claim 2,
the switching transient electromagnetic field synchronous measuring probe also comprises a metal shielding box;
and placing the circuit board containing the electromagnetic field separation circuit in the metal shielding box.
9. The method for measuring the closing time of a hybrid direct current breaker based on the electromagnetic field synchronous measurement as claimed in claim 1,
in the step 1, the switching transient electromagnetic field synchronous measurement probe based on the symmetrical double-gap loop antenna is erected 1-2 meters above the ground, and the horizontal distance between the probe and the hybrid direct-current circuit breaker is 3-5 meters.
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