Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention discloses a field test device for the volt-ampere characteristic of a lightning arrester. As shown in fig. 1, the field test device for volt-ampere characteristics of a lightning arrester comprises: the device comprises a power supply DC, a volt-ampere characteristic test main circuit and a state monitoring and control circuit.
Wherein, volt-ampere characteristic test main circuit includes: MOSFET switch K1, high-voltage direct current switch group 1, energy storage capacitor group C, freewheeling diode D, reactor L and zinc oxide parallel connection valve post group 2.
The high-voltage direct-current switch group 1 comprises a plurality of high-voltage direct-current switches Q connected in series1~Qn. The zinc oxide parallel valve column group 2 comprises a plurality of zinc oxide valve column branches connected in parallel. Each zinc oxide spool branch includes at least one zinc oxide spool 21. When the zinc oxide spool branch comprises at least two zinc oxide spools 21, the at least two zinc oxide spools 21 are connected in series.
The power supply DC is a direct current charging power supply. The positive terminal of the power supply DC is connected to one terminal of a MOSFET switch K1. Preferably, a current limiting resistor R is connected in series between the power supply DC and the MOSFET switch K1 to avoid damage to the MOSFET switch K1. The other end of the MOSFET switch K1 is connected with one end of the high-voltage direct-current switch group 1. The other end of the high-voltage direct-current switch group 1 is connected with one end of a zinc oxide parallel valve column group 2. The negative pole of the power supply DC is connected with the other end of the zinc oxide parallel valve post group 2. One plate of the energy storage capacitor bank C is connected with the other end of the MOSFET switch K1. The other polar plate of the energy storage capacitor bank C is connected with the negative pole of the power supply DC. The fly-wheel diode D is reversely connected in parallel on the two polar plates of the energy storage capacitor bank C, namely the anode of the fly-wheel diode D is connected with the polar plate of the energy storage capacitor bank C connected with the cathode of the power supply DC, and the cathode of the fly-wheel diode D is connected with the polar plate of the energy storage capacitor bank C connected with the anode of the power supply DC, so that the electric reactor L is prevented from reversely charging the energy storage capacitor bank C. One end of the reactor L is connected with the other end of the high-voltage direct-current switch group 1. The other end of the reactor L is connected with the other end of the zinc oxide parallel valve column group 2.
The state monitoring and control circuit is connected with the MOSFET switch K1, the high-voltage direct-current switch group 1, the energy storage capacitor group C, the reactor L and the zinc oxide parallel valve column group 2. The state monitoring and control circuit is used for collecting the voltage of the two pole plates of the energy storage capacitor bank C, the voltage of the two ends of the zinc oxide parallel valve column group 2 and the current flowing through the reactor L, and controlling the on-off of the MOSFET switch K1 and the high-voltage direct-current switch bank 1 according to the voltage of the two pole plates of the energy storage capacitor bank C and the current flowing through the reactor L. The state monitoring and control circuit is also used for obtaining a voltage-current characteristic curve of the lightning arrester according to the voltage at the two ends of the zinc oxide parallel valve column group 2 and the current flowing through the reactor L. Specifically, the highest peak voltage in the clamping voltage of the zinc oxide arrester, namely the maximum residual voltage value, is taken as the voltage of the volt-ampere characteristic longitudinal axis during each discharge; the discharge current corresponding to the maximum residual voltage value is the current of the volt-ampere characteristic cross shaft, and a volt-ampere characteristic point corresponding to a certain discharge energy can be obtained. The voltage of the energy storage capacitor bank C is controlled by the microprocessor 4 to control the discharge energy, and the clamping voltage and the discharge current of the zinc oxide arrester are different under different discharge energies. The clamping voltage of the zinc oxide arrester is the voltage at two ends of the zinc oxide parallel valve post group 2. The discharge current is the current flowing through the reactor L. And sequentially measuring the clamping voltage-discharge current data of a plurality of groups of zinc oxide arresters to obtain a plurality of volt-ampere characteristic points, and sequentially connecting the plurality of volt-ampere characteristic points to obtain a volt-ampere characteristic curve of the zinc oxide arrester.
Specifically, the state monitoring and control circuit includes: the analog-to-digital conversion module 3 and the microprocessor 4, wherein the analog-to-digital conversion module 3 is connected with the microprocessor 4. The analog-to-digital conversion module 3 is configured to convert the received voltage of the two electrode plates of the energy storage capacitor bank C, the voltage at the two ends of the zinc oxide parallel valve post group 2, and the analog quantity of the current flowing through the reactor L into digital quantities, and then send the digital quantities to the microprocessor 4. The microprocessor 4 is used for controlling the on-off of the MOSFET switch K1 and the high-voltage direct-current switch group 1 according to the digital quantity of the voltage of the two electrode plates of the energy storage capacitor group C; and obtaining a volt-ampere characteristic curve of the lightning arrester according to the voltage at two ends of the zinc oxide parallel valve column group 2 and the digital quantity of the current flowing through the reactor L. Specifically, when the energy storage capacitor bank C starts to be charged, the microprocessor 4 controls the MOSFET switch K1 to be turned on; when the voltage of the two electrode plates of the energy storage capacitor bank C reaches a preset value, the MOSFET switch K1 is controlled to be switched off, and the microprocessor 4 controlsFor each high-voltage DC switch Q1~QnConducting to control the energy storage capacitor bank C to discharge; when the inductive energy of the reactor L reaches a peak value (i.e. the current through the inductor L reaches a peak value), the microprocessor 4 controls each of the high voltage dc switches Q1~QnAnd (5) disconnecting. The microprocessor 4 comprises logic elements such as ARM and FPGA.
The state monitoring and control circuit further comprises: a first pulse divider 5. The first pulse voltage divider 5 is connected in parallel to the two plates of the energy storage capacitor bank C. The first pulse voltage divider 5 is further connected with the analog-to-digital conversion module 3, and the first pulse voltage divider 5 is used for collecting the voltage of the two electrode plates of the energy storage capacitor bank C.
The state monitoring and control circuit further comprises: a second pulse divider 6. And the second pulse voltage divider 6 is connected in parallel at two ends of the zinc oxide parallel valve column group 2. The second pulse voltage divider 6 is also connected to the analog-to-digital conversion module 3. And the second pulse voltage divider 6 is used for collecting the voltage at two ends of the zinc oxide parallel valve column group 2.
The state monitoring and control circuit further comprises: a first acquisition sensor 7. The first acquisition sensor 7 includes: a first rogowski coil and a first integrator. The first rogowski coil is connected with the other end of the reactor L and the input end of the first integrator respectively. The output end of the first integrator is connected with the analog-to-digital conversion module 3. The first rogowski coil is used to collect a differential signal of the current flowing through the reactor L. The first integrator is used for integrating a differential signal of the current flowing through the reactor L to obtain the current flowing through the reactor and sending the current to the analog-to-digital conversion module 3.
In addition, the discharge current corresponding to the maximum residual voltage value can also be obtained by the sum of the currents flowing through each zinc oxide valve column branch. Therefore, the condition monitoring and control circuit further comprises: a plurality of second acquisition sensors 8. The second acquisition sensor 8 includes: a second rogowski coil and a second integrator. Each second rogowski coil is connected to the other end of each zinc oxide spool branch (i.e., the end connected to the other end of the inductor L) and the input end of the second integrator, respectively. The output end of the second integrator is connected with the analog-to-digital conversion module 3. The second rogowski coil is used to collect differential signals of the current flowing through each zinc oxide spool branch. Each second integrator is configured to integrate a differential signal of the current flowing through each zinc oxide spool branch to obtain the current flowing through each zinc oxide spool branch, and send the current to the analog-to-digital conversion module 3. The analog-to-digital conversion module 3 is used for converting the analog quantity of the current flowing through each zinc oxide valve column branch into digital quantity and sending the digital quantity to the microprocessor 4. And the microprocessor 4 is used for obtaining the volt-ampere characteristic curve of the lightning arrester according to the voltage at two ends of the zinc oxide parallel valve post group 2 and the digital quantity of the sum of the currents flowing through each zinc oxide valve post branch.
The state monitoring and control circuit further comprises: and a fiber control module 9. The optical fiber control module 9 is respectively connected with the drive circuit D of the MOSFET switch K10Each high-voltage direct-current switch Q of the high-voltage direct-current switch group 11~QnDriving circuit D of1~DnAnd is connected to the microprocessor 4. The optical fiber control module 9 is used for driving a circuit D of the MOSFET switch K1 sent by the microprocessor 40On/off control signal d0Drive circuit D forwarded to MOSFET switch K10And, each high voltage dc switch Q sent by the microprocessor 41~QnDriving circuit D of1~DnOn/off control signal d1~dnTo each high voltage dc switch Q1~QnDriving circuit D of1~Dn. Before charging, MOSFET switch K1 and each high-voltage DC switch Q1~QnAre all disconnected. When the energy storage capacitor bank C starts to be charged, the optical fiber control module 9 receives the instruction of the microprocessor 4 and sends a conducting instruction to the MOSFET switch K1. When the voltage of the energy storage capacitor bank C reaches a preset value, the optical fiber control module 9 receives an instruction of the microprocessor 4, sends a disconnection instruction to the MOSFET switch K1 and sends a disconnection instruction to each high-voltage direct-current switch Q1~QnAnd sending a conducting instruction. When the inductance energy of the reactor L reaches the peak value, the optical fiber control module 9 receives the instruction of the microprocessor 4 and sends the instruction to each high-voltage direct-current switch Q1~QnAnd sending a disconnection instruction.
In particular, a high voltage dc switch Q1~QnIs an IGBT insulated gate bipolar transistor. The value of n depends on the voltage of the test device, etcAnd the rated voltage withstanding class Vce of the IGBT. To preserve a certain voltage margin, n × Vce should be greater than 2 times the highest voltage rating of the test device. Each high voltage dc switch Q1~QnEach static voltage equalizing resistor R is respectively connected in parallel1~RnAnd each dynamic voltage-sharing capacitor C1~CnCompared with the traditional series voltage-sharing mode of R + RCD (resistor + resistor/capacitor/diode), the embodiment of the invention achieves the effect of series voltage-sharing by connecting RC in parallel, and reduces the device cost by reducing high-voltage semiconductor diodes in parallel.
Specifically, the reason for carrying out series voltage equalization of the IGBTs by adopting the RC instead of the R + RCD is as follows:
in the traditional high-frequency switch circuit, an RCD circuit is needed to carry out voltage-sharing on series-connected IGBTs, and a diode is indispensable as an important follow-current component. In the testing device of the embodiment of the invention, only one pulse needs to be generated each time, and the interval time of each pulse can reach several seconds.
When the power supply DC charges the energy storage capacitor bank C, the MOSFET switch K1 is kept on, and the high-voltage direct-current switch Q1~QnKeep off, all static equalizing resistors R1~RnAnd dynamic voltage-sharing capacitor C1~CnWill bear the charging voltage of the energy storage capacitor bank C together, and the dynamic voltage-sharing capacitor C1~CnEnergy will be stored. When the MOSFET switch K1 is turned off, the high-voltage direct-current switch Q1~QnAfter the capacitor is conducted, the energy storage capacitor bank C and the dynamic voltage-sharing capacitor C1~CnThe energy stored in the medium starts to go to the high-voltage direct-current switch Q1~QnDischarging due to high voltage DC switch Q1~QnPresence of transconductance when switching on the high voltage DC switch Q1~QnCan be equivalent to a transient constant current source, and the impact current can not be infinitely increased. Demonstration is carried out by building 2400V-100A low-voltage current level experimental platform and building simulation, and the high-voltage direct-current switch Q is connected with a power supply1~QnReceived from the dynamic equalizing capacitor C when conducting1~CnThe current surge of (2) is shown in figure 2.
Wherein the storage capacitor bank CThe capacitance is 5950uf, the internal resistance of the reactor L is 50.4mH/7.04 omega, and the initial voltage U of the energy storage capacitor bank C0400V, drive gate resistance R g10 omega, voltage-sharing capacitor CnAt 47nf, the arrester peak current is 44.2A. The peak value of the impact current generated by the capacitor in the simulation turn-on process is 2.35A. In the experiment, the peak value of the impulse current of the open pass is 2.38A, the duration is about 2us, and the experimental curve has certain oscillation due to the influence of circuit parasitic parameters.
Thus, the high voltage dc switch Q1~QnCan bear the impact current generated by capacitor discharge in the process of switching on, and can adopt a dynamic voltage-sharing capacitor C only connected in parallel1~CnThe dynamic voltage-sharing method greatly reduces the semiconductor cost of the traditional RCD voltage-sharing topology.
Because the whole voltage level of the high-voltage direct-current switch group 1 is higher and can reach dozens of kV to hundreds of kV, each high-voltage direct-current switch Q1~QnSeparate driving circuits are required for isolated driving while avoiding high voltage dc switching Q1~QnPartial electric field discharge phenomenon under high voltage requires the high voltage DC switch Q to be connected in series1~QnAnd high voltage dc switch Q1~QnDriving circuit D of1~DnAnd immersing in insulating transformer oil. Therefore, it is necessary to charge the high voltage dc switch Q through a wireless charging circuit1~QnDriving circuit D of1~DnAnd (5) supplying power. In particular, each high voltage dc switch Q1~QnDriving circuit D of1~DnThere is a battery, typically a lithium battery. Each battery passes through each detachable wireless charger X1~XnAnd (6) charging. Will wireless charger X after the electric quantity is full1~XnWhen the testing device works, the primary coil is removed, and the testing device only changes the battery to the high-voltage direct-current switch Q1~QnDriving circuit D of1~DnPower supply is carried out, so that the high-voltage direct-current switch Q can be immersed in transformer oil1~QnDriving circuit D of1~DnTo supply power.
The embodiment of the invention also discloses a field test method for the volt-ampere characteristic of the lightning arrester. The testing method adopts the lightning arrester volt-ampere characteristic field testing device of the embodiment to test.
In particular, the high voltage dc switch Q in the initial state1~QnTurning off, switching on MOSFET switch K1 to charge the energy storage capacitor group C with the power supply DC, and when the terminal voltage reaches a preset value, switching off MOSFET switch K1 and simultaneously switching on high voltage DC switch Q1~QnThe energy of the energy storage capacitor bank C is released to the reactor L, the discharging process is an under-damped oscillation process, and when the energy of the inductor reaches the peak value, the high-voltage direct-current switch Q is switched off1~QnWhen the reactor L excites a sufficiently high voltage to cause the zinc oxide parallel spool 21 to enter a breakdown region (voltage-clamped state), and when the energy of the reactor L is released to the zinc oxide parallel spool 21, a large-amplitude impact current can be generated. Because each zinc oxide valve post branch is connected in parallel, no matter how long the duration of the wave head and the wave tail of the impact current is, the current relative value flowing through each zinc oxide valve post branch of the lightning arrester can reflect the current balance of each zinc oxide valve post branch, and after the excitation voltage and the current are measured and the data are processed, the volt-ampere characteristic curve of the zinc oxide lightning arrester can be obtained.
Specifically, the principle of the discharging process of the main circuit for testing the volt-ampere characteristic is as follows:
the zinc oxide arrester is in a low-resistance conduction state under the action of a high enough excitation voltage, the voltage clamp is kept unchanged, and the current is approximately linearly reduced after being increased in a steep wave manner. Therefore, the energy storage E required by the reactor L to break down the zinc oxide arrester is as follows:
wherein ipRepresents the peak current, U, of zinc oxidebDenotes the clamping voltage, T, of zinc oxidesIndicating the duration of the current.
The energy storage capacitor bank C is at an initial voltage U0To reactor LIn the electric process, energy is stored in a capacitor Ein=0.5×CU0 2Considering the inductance internal resistance R, the current i of the reactor L and the voltage u of the storage capacitor bank C during the discharging process of the storage capacitor bank CcIn the under-damped state the expression is:
time t at which reactor L current attains a maximum valuemComprises the following steps:
tm=β/ω
current of reactor L is at tmThe maximum value I is obtained at the momentpComprises the following steps:
the discharge efficiency eta of the energy storage capacitor bank C to the reactor L is as follows:
energy E required by energy storage capacitor bank CinComprises the following steps:
wherein, delta is the root real part of the second-order circuit differential equation characteristic, omega is the root imaginary part of the second-order circuit differential equation characteristic,
order to
Then ω is equal to ω
0sinβ,δ=ω
0cos beta. L represents the reactor inductance, and C represents the storage capacitor bank capacitance.
Measuring the voltage across the energy storage capacitor bank C by the first pulse voltage divider 5, and outputting a voltage signal u1Sent to the analog-to-digital conversion module 3. The voltage u at the two ends of the zinc oxide parallel valve column group 2 is subjected to voltage division by a second pulse voltage divider 62Measuring and converting the voltage signal u2Sent to the analog-to-digital conversion module 3. The differential signal of the current flowing through the reactor L is collected through the first Rogowski coil, and the first integrator integrates and reduces the differential signal into a current waveform i0And then sent to the analog-to-digital conversion module 3. Collecting differential signals of current flowing through each zinc oxide valve column branch through each second Rogowski coil, and integrating and reducing the differential signals into a current waveform i by the second integrator1~imAnd then sent to the analog-to-digital conversion module 3. The analog-to-digital conversion module 3 sends the acquired voltage and current signals to the microprocessor 4 for calculation, and meanwhile, the FPGA of the microprocessor 4 carries out high-voltage direct-current switch Q1~QnThe voltage unevenness phenomenon caused by the time delay of optical fibers and devices at the turn-on and turn-off time is accurately delayed and compensated and then output to a MOSFET switch K1 and a high-voltage direct-current switch Q1~QnControl signal d of0’~dn', the fibre-optic control module 9 will control the signal d0’~dn' conversion to control signal d0~dnThen, the control signal d is transmitted0A drive circuit for transmitting the control signal d to the MOSFET switch K11~dnRespectively transmitted to a high-voltage direct-current switch Q1~QnDriving circuit D of1~DnThe original strong and weak electric signals of the secondary side are isolated, and the interference of high voltage to a control circuit is reduced.
Specifically, the voltage-current characteristic of the zinc oxide arrester can be obtained by testing the waveform of the arrester valve post resistor disc after the arrester valve post resistor disc enters a clamping state to verify that the voltage-current characteristic of the zinc oxide arrester is as follows:
A2400V-100A test system is set up for testing, firstly, 3 groups of lightning arrester valve columns numbered 1, 2 and 3 are subjected to discharge test respectively by using the same inductance energy storage, current flowing through the lightning arrester is collected by using a Rogowski coil and an integrator, residual voltage is collected by using a pulse voltage divider, and a schematic diagram of residual voltage and current waveform of the No. 1 valve column after collection is shown in figure 3. The residual voltage of the lightning arrester is approximately constant after rising, and the current linearly decreases after rising with steep wave of about 10 us. Three groups of valve posts are connected in parallel and are simultaneously tested, and the discharge test is carried out under different inductance energy storage conditions, and as shown in fig. 4, the residual voltage of the arrester and the current waveform flowing through each valve post in a certain discharge test are shown. Experimental waveforms show that the lightning arrester can be in a clamping state by the testing method, and voltage-current characteristics of the zinc oxide lightning arrester can be obtained by acquiring and processing voltage and current in the clamping state.
To sum up, the embodiment of the invention controls the energy storage and release of the energy storage electrolytic capacitor group and the reactor group of the passive device through the on-off of the MOSFET switch and the high-voltage direct-current switch, thereby generating the high-voltage excitation pulse to enable the zinc oxide resistance card to enter a clamping state, and being capable of measuring the volt-ampere characteristic of the zinc oxide arrester.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.