CN113346364A - Cable terminal explosion-proof system and method - Google Patents
Cable terminal explosion-proof system and method Download PDFInfo
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- CN113346364A CN113346364A CN202110484236.7A CN202110484236A CN113346364A CN 113346364 A CN113346364 A CN 113346364A CN 202110484236 A CN202110484236 A CN 202110484236A CN 113346364 A CN113346364 A CN 113346364A
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- 238000000034 method Methods 0.000 title claims abstract description 15
- 230000005540 biological transmission Effects 0.000 claims abstract description 83
- 238000004880 explosion Methods 0.000 claims abstract description 25
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical group [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 40
- 239000011787 zinc oxide Substances 0.000 claims description 20
- 238000001514 detection method Methods 0.000 claims description 10
- 230000035699 permeability Effects 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 3
- 208000025274 Lightning injury Diseases 0.000 abstract 1
- 230000032683 aging Effects 0.000 description 2
- 230000000172 allergic effect Effects 0.000 description 2
- 208000010668 atopic eczema Diseases 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000977 initiatory effect Effects 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 230000002265 prevention Effects 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 238000004891 communication Methods 0.000 description 1
- 230000001934 delay Effects 0.000 description 1
- 230000005520 electrodynamics Effects 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02B—BOARDS, SUBSTATIONS OR SWITCHING ARRANGEMENTS FOR THE SUPPLY OR DISTRIBUTION OF ELECTRIC POWER
- H02B1/00—Frameworks, boards, panels, desks, casings; Details of substations or switching arrangements
- H02B1/26—Casings; Parts thereof or accessories therefor
- H02B1/30—Cabinet-type casings; Parts thereof or accessories therefor
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02B—BOARDS, SUBSTATIONS OR SWITCHING ARRANGEMENTS FOR THE SUPPLY OR DISTRIBUTION OF ELECTRIC POWER
- H02B1/00—Frameworks, boards, panels, desks, casings; Details of substations or switching arrangements
- H02B1/20—Bus-bar or other wiring layouts, e.g. in cubicles, in switchyards
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02B—BOARDS, SUBSTATIONS OR SWITCHING ARRANGEMENTS FOR THE SUPPLY OR DISTRIBUTION OF ELECTRIC POWER
- H02B1/00—Frameworks, boards, panels, desks, casings; Details of substations or switching arrangements
- H02B1/26—Casings; Parts thereof or accessories therefor
- H02B1/30—Cabinet-type casings; Parts thereof or accessories therefor
- H02B1/32—Mounting of devices therein
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/20—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess voltage
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/22—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
- H02H9/041—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage using a short-circuiting device
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
- H02H9/06—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage using spark-gap arresters
Abstract
The invention discloses an explosion-proof system and method for a cable terminal, wherein the system comprises a transmission cable, a cable terminal, a switch cabinet and an explosion-proof branch circuit; the power transmission cable is respectively connected with the photovoltaic power station and the cable terminal; the switch cabinet comprises a circuit breaker, and the circuit breaker is connected to the cable terminal; the cable terminal comprises an inlet connecting terminal connected to the transmission cable, a first outlet connecting terminal connected to the circuit breaker and a second outlet connecting terminal connected to the explosion-proof branch circuit; when the cable terminal normally operates, the explosion-proof branch circuit is in an open circuit state; when the breaker is disconnected due to lightning strike of the photovoltaic power station, the anti-explosion branch circuit is in a short-circuit state, so that lightning voltage waves generated by the lightning strike in the power transmission cable are transmitted to the grounding end through the anti-explosion branch circuit. The invention can avoid the cable terminal from exploding caused by the lightning stroke of the photovoltaic power station.
Description
Technical Field
The invention relates to the technical field of explosion prevention of cable terminals, in particular to an explosion prevention system and method of a cable terminal.
Background
In a photovoltaic power station power system, a transmission cable normally works under a rated voltage, voltage deviation is very small, and a cable terminal entering a switch cabinet also normally works. However, the photovoltaic module works outdoors, so that the photovoltaic module is struck by lightning, under the condition, a lightning overvoltage wave can appear in the system, the amplitude is generally 300-400 kV, the lightning overvoltage wave is transmitted along the power transmission cable in a traveling wave mode, and the duration is very short and is about 50-100 mu s. Because the amplitude of the high-voltage power supply is high, huge energy can be brought in a short time, and insulation faults and power failure accidents of electrical equipment can be caused.
In an electric power system taking a cable as a power transmission line, a cable terminal is connected with a circuit breaker in a switch cabinet, and power transformation and distribution are carried out through the switch cabinet and a power transformation and distribution device, so that the condition that the circuit of the cable terminal is intact is guaranteed, and the stability and reliability of the whole system are guaranteed. When the photovoltaic power station is attacked by thunder, the transmission cable transmits thunder overvoltage waves to the cable terminal, and huge overcurrent is generated under the action of high voltage to disconnect the circuit breaker. At the moment, voltage waves in the transmission cable are reflected and superposed, and ultrahigh voltage which is twice of incident waves appears, so that huge electrodynamic force and heat are generated, the explosion phenomenon of a cable terminal is caused, and the transmission cable and the switch cabinet are damaged.
Disclosure of Invention
The invention provides a cable terminal explosion-proof system and method, and aims to solve the technical problem that a cable terminal explodes due to lightning strike of a photovoltaic power station in the prior art.
The invention provides an explosion-proof system for a cable terminal, which comprises a transmission cable, a cable terminal, a switch cabinet and an explosion-proof branch circuit, wherein the cable terminal is connected with the transmission cable;
the two ends of the power transmission cable are respectively connected with the photovoltaic power station and the cable terminal;
the switch cabinet comprises a circuit breaker, and the circuit breaker is connected to the cable terminal;
the cable terminal comprises an inlet connecting terminal, a first outlet connecting terminal and a second outlet connecting terminal, the inlet connecting terminal is connected to the power transmission cable, the first outlet connecting terminal is connected to the circuit breaker, and the second outlet connecting terminal is connected to the explosion-proof branch;
when the cable terminal normally operates, the explosion-proof branch circuit is in the open circuit state; when the photovoltaic power station is struck by lightning, the breaker is disconnected, the explosion-proof branch circuit is in a short-circuit state, and therefore lightning voltage waves generated by the lightning strike in the power transmission cable are transmitted to the grounding end through the explosion-proof branch circuit.
In some possible implementation manners of the invention, the explosion-proof branch comprises an explosion-proof wire connected with the second outlet connection terminal and the grounding terminal, and a pressure-sensitive valve plate and an adjustable resistor which are sequentially arranged on the explosion-proof wire;
the pressure-sensitive valve plate is used for being disconnected when the lightning voltage wave is not generated in the power transmission cable; conducting when the lightning voltage wave is generated in the power transmission cable;
and the adjustable resistor is used for matching the resistance of the explosion-proof branch with the line wave impedance of the transmission cable when the pressure-sensitive valve plate is conducted.
In some possible implementation manners of the invention, the explosion-proof branch further comprises a discharge gap arranged on the explosion-proof routing, the discharge gap is arranged between the second outlet connection terminal and the pressure-sensitive valve plate, and the discharge gap is used for being disconnected when the lightning voltage wave is not generated in the transmission cable; conducting when the lightning voltage wave is generated in the power transmission cable.
In some possible implementation manners of the present invention, the cable terminal explosion-proof system further includes a detection device and a control device, the detection device is configured to detect a voltage in the explosion-proof branch and generate a voltage signal, the control device is in communication connection with the detection device and configured to receive the voltage signal and determine whether the voltage signal is smaller than a threshold voltage, if the voltage signal is smaller than the threshold voltage, a close instruction is sent to control the circuit breaker to close, and the explosion-proof branch is in a circuit break state; and if the voltage signal is greater than or equal to the threshold voltage, the explosion-proof branch circuit is in a short-circuit state.
In some possible implementations of the invention, the line wave impedance Z of the power transmission cable is:
wherein, mu0Magnetic permeability in vacuum; mu.srIs relative magnetic permeability; epsilon0Dielectric constant of vacuum or gas; epsilonrIs a relative dielectric constant; h iscIs the distance between the transmission cable and the ground; r is the radius of the transmission cable.
In some possible implementation manners of the invention, the pressure-sensitive valve plate is further configured to be disconnected after the lightning voltage wave in the explosion-proof trace is eliminated, so that the explosion-proof branch circuit is in the open circuit state.
In some possible implementation manners of the present invention, the voltage-sensitive valve sheet is a zinc oxide voltage-sensitive resistor sheet, and the volt-ampere characteristic of the zinc oxide voltage-sensitive resistor sheet is as follows:
u＝Ciδ
where u is the voltage, i is the current, C is the material constant, and δ is the nonlinear exponent.
In some possible implementations of the invention, the discharge gaps are arranged vertically, and the gap of the discharge gaps is up to 10 μm.
In some possible implementations of the invention, the adjustable resistor has a resistance value of 0 Ω -100 Ω.
On the other hand, the invention also provides an explosion-proof method for the cable terminal, which is suitable for any one of the explosion-proof systems for the cable terminal, and the explosion-proof method for the cable terminal comprises the following steps:
when a photovoltaic power station is struck by lightning, lightning voltage waves are generated in a power transmission cable, and a circuit breaker in a switch cabinet is disconnected, so that the explosion-proof branch circuit is in a short-circuit state, and the lightning voltage waves generated by the lightning strike in the power transmission cable are transmitted to a grounding end through the explosion-proof branch circuit;
judging whether the lightning voltage waves in the power transmission cable are eliminated or not, and if the lightning voltage waves in the power transmission cable are eliminated, enabling the explosion-proof branch circuit to be in an open circuit state; and if the lightning voltage wave in the power transmission cable is not eliminated, the anti-explosion branch circuit is in a short-circuit state.
According to the invention, the explosion-proof branch circuit connected with the second outlet connecting terminal is arranged, when the photovoltaic power station is struck by lightning and the breaker is disconnected, the explosion-proof branch circuit is in a short-circuit state, so that a lightning voltage wave generated by the lightning strike in the power transmission cable is transmitted to the grounding end through the explosion-proof branch circuit, the phenomenon that the lightning voltage wave is reflected and superposed due to the disconnection of the breaker caused by the lightning voltage wave is avoided, the explosion of the cable terminal is avoided, and the safety of the power transmission cable and the switch cabinet is ensured.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of an embodiment of a cable termination explosion-proof system provided by an embodiment of the invention;
fig. 2 is a schematic flow chart of an embodiment of an explosion-proof method for a cable termination provided by an embodiment of the present invention.
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 only a part of the embodiments of the present invention, and not all of the embodiments. 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 following description is presented to enable any person skilled in the art to make and use the invention. In the following description, details are set forth for the purpose of explanation. It will be apparent to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and processes are not shown in detail to avoid obscuring the description of the invention with unnecessary detail. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.
The embodiment of the invention provides a cable terminal explosion-proof system and a method thereof, which are explained in detail below.
Fig. 1 is a schematic structural diagram of an embodiment of a cable termination explosion-proof system according to an embodiment of the present invention, as shown in fig. 1,
the cable terminal explosion-proof system 10 is used for preventing the cable terminal 300 from exploding when the photovoltaic power station 100 is struck by lightning, and the cable terminal explosion-proof system 10 comprises a transmission cable 200, a cable terminal 300, a switch cabinet 400 and an explosion-proof branch 500;
both ends of the transmission cable 200 are respectively connected with the photovoltaic power station 100 and the cable terminal 300;
the switchgear 400 comprises a circuit breaker 410, the circuit breaker 410 being connected to the cable terminal 300;
the cable termination 300 comprises an inlet connection terminal 310, a first outlet connection terminal 320 and a second outlet connection terminal 330, the inlet connection terminal 310 being connected to the transmission cable 200, the first outlet connection terminal 320 being connected to the circuit breaker 410, the second outlet connection terminal 330 being connected to the explosion-proof branch 500;
when the cable terminal 300 normally operates, the explosion-proof branch 500 is in an open circuit state; when the photovoltaic power station 100 is struck by lightning and the circuit breaker 410 is disconnected, the anti-explosion branch 500 is in a short-circuit state, so that the lightning voltage wave generated by the lightning strike in the power transmission cable 200 is transmitted to the ground terminal through the anti-explosion branch 500.
In the embodiment of the present invention, by providing the explosion-proof branch 500 connected between the second outlet terminal 330 and the ground terminal, when the photovoltaic power station 100 is struck by lightning and the circuit breaker 410 is disconnected, the explosion-proof branch 500 is in a short-circuit state, so that the lightning voltage waves generated by the lightning strike in the power transmission cable 200 are transmitted to the ground terminal through the explosion-proof branch 500, and the lightning voltage waves are prevented from being reflected and superimposed due to the disconnection of the circuit breaker 410 caused by the lightning voltage waves, thereby preventing the cable terminal 300 from being exploded, and ensuring the safety of the power transmission cable 200 and the switch cabinet 400.
Further, in some embodiments of the present invention, as shown in fig. 1, the anti-explosion branch 500 includes an anti-explosion wire 510 connecting the second outlet connection terminal 330 and the ground terminal, and a pressure-sensitive valve plate 520 and an adjustable resistor 530 sequentially disposed on the anti-explosion wire 510;
the voltage-sensitive valve sheet 520 is used for being disconnected when no lightning voltage wave is generated in the power transmission cable 200; conducting when a lightning voltage wave is generated in the power transmission cable 200;
the adjustable resistor 530 is used for matching the resistance of the explosion-proof branch 500 with the line wave impedance of the power transmission cable 200 when the voltage-sensitive valve plate 520 is conducted. The specific working principle of the adjustable resistor 530 is as follows: the adjustable resistor 530 can adjust its own resistance value at will, thereby realizing the matching of the resistance value of the explosion-proof branch 500 and the line wave impedance of the power transmission cable 200.
Wherein, the line wave impedance Z of the power transmission cable 200 is:
wherein, mu0Magnetic permeability in vacuum; mu.srIs relative magnetic permeability; epsilon0Dielectric constant of vacuum or gas; epsilonrIs a relative dielectric constant; h iscIs the distance between the transmission cable 200 and the ground; r is the radius of the power transmission cable 200.
After the pressure-sensitive valve plate 520 and the adjustable resistor 530 are arranged, the explosion-proof principle of the explosion-proof branch 500 is as follows:
setting a line wave impedance as Z1Line 1 and the other line have a wave impedance of Z2Line 2 is connected at node a, a travelling wave propagates from line 1 to line 2; for node A, the forward wave of the first line is the incident wave projected on point A; the forward wave of the second line is the incident wave refracted to Z through the node A2A refracted wave from above; the backward wave of the first line is generated by the reflection of the incident wave at node a and may be referred to as the reflected wave. There may also be a reverse wave on the second line, which may be a reflected wave caused by the refracted wave reaching the termination of the second line, or another overvoltage wave intruding from the termination of the second line, where another overvoltage wave intruding from the termination of the second line is temporarily disregarded.
The voltage refractive index α and the voltage refractive index β at node a are:
and the relationship between the voltage refractive index α and the voltage reflection coefficient β is 1+ β ═ α, with Z1And Z2The α and β ranges satisfy:
when the end of line 2 is short-circuited, it is equivalent to Z2In the case of ∞, α is 2 and β is 1. This result indicates that the voltage incident wave reaches the end of the open circuit and is totally reflected, resulting in a voltage rise at the end of the line 1 of twice the voltage incident wave.
Namely: when the lightning voltage wave is transmitted to the cable terminal 300, the circuit breaker 410 is opened such that the cable terminal 300 is opened, and the voltage refractive index α is 1, that is, the lightning voltage wave transmitted to the cable terminal 200 may be totally reflected, and as a result, the voltage of the cable terminal 200 is increased to twice the voltage of the lightning voltage wave. Under the action of the large voltage, the cable termination 200 receives a large electromotive force and generates a large amount of heat, so that the cable termination 200 may explode.
And when the thunder voltage wave is generated, the voltage-sensitive valve plate 520 is conducted, so that the explosion-proof branch circuit 500 is short-circuited, and the impedance of the explosion-proof branch circuit is matched with the impedance of the power transmission cable 200 by adjusting the adjustable resistor 530, that is: z1＝Z2If α is 1, β is 0; this indicates that the voltage refracted wave is equal to the incident wave, and the voltage reflected wave is zero, i.e. no reflection or refraction occurs, i.e. the lightning voltage wave is not reflected at this time and flows into the ground terminal along the path of the explosion-proof branch 500. Thereby realizing that an ultra-high voltage is not generated at the cable terminal 200, thereby preventing the cable terminal 200 from exploding.
Further, in some embodiments of the present invention, the pressure-sensitive valve sheet 520 is further configured to be opened after the lightning voltage wave in the anti-explosion wire 510 is eliminated, so that the anti-explosion branch 500 returns to the open state. Through the arrangement, the photovoltaic power station 100 can be quickly recovered to normally operate after being struck by lightning, the maintenance cost is reduced, and the safe and stable operation of the switch cabinet 400 is ensured.
In some embodiments of the invention, the piezo sheet 520 is a zinc oxide piezo-resistor sheet.
Further, the volt-ampere characteristics of the zinc oxide varistor are as follows:
u＝Ciδ
where u is the voltage, i is the current, C is the material constant, and δ is the nonlinear exponent.
The non-linearity index delta is related to the current density, the non-linearity index of the zinc oxide varistor is only 0.01-0.04 generally, and the non-linearity index cannot exceed 0.1 even under a large impact current (such as l0 kA).
The working principle of the zinc oxide varistor can be seen from the volt-ampere characteristic of the zinc oxide varistor: under the action of normal working voltage, the zinc oxide varistor has large resistance (the resistivity is up to 1010-1011 omega cm), the passing leakage current is small (less than lmA), and under the action of overvoltage (such as lightning voltage wave), the resistance can be sharply reduced.
Further, the design parameters of the zinc oxide varistor comprise rated operation voltage UεStandard discharge current level, maximum allowable continuous operation voltage UMCONInitial operating voltage and residual voltage URProtection level, voltage ratio and chargeability AVR, each design parameter is selected according to the following rules:
1. rated operating voltage UεSelecting: when the protected power transmission cable 200 is at a voltage level of UNRated operating voltage U of oxidizing voltage-sensitive resistor disc with power frequency of 50HzεTaking 1.8 times of the peak value of rated phase voltage of the transmission cable, namely:
2. selecting standard discharge current grades: the standard discharge current level should be selected based on the line wave impedance of the power transmission cable 200, and in some embodiments of the present invention, the standard discharge current level may be selected to be on the order of 10 kA.
3. Allowable maximum continuous operation voltage UMCONSelecting: allowable maximum continuous operation voltage UMCONThe maximum power frequency voltage effective value of the zinc oxide voltage-sensitive resistance sheet which can continuously run for a long time is generally equal to the highest working phase voltage of the system, namely
4. Selecting an initial action voltage: usually at a voltage U at which current lmA is passed1mAAs the initial operating voltage.
5. Selecting residual pressure: residual voltage refers to a voltage peak value appearing between terminals of the zinc oxide varistor when discharge current passes through the zinc oxide varistor, and the residual voltage comprises three residual voltage values:
residual voltage U under lightning impulse currentR(l): the current waveform is 7-9/8-22 mus, the standard discharge current is 5kA, l0kA and 20 kA;
residual voltage U under operation impact currentR(s): the current waveform is 30-100/60-200 mus, and the current peak value is 0.5kA, lkA and 2 kA;
residual voltage U under steep wave impact currentR(st): the current wave front time is l mus and the peak is the same as the standard (lightning impulse) current.
6. Selecting the protection level: lightning protection level U of zinc oxide piezoresistor sheetp(l)The greater of the two values:
(1) lightning impulse residual voltage UR(l)；
(2) Steep wave impact residual voltage UR(st)Divided by 1.15.
Namely:
operation protection level U of zinc oxide varistorp(s)Equal to the operating impact residual pressure UR(s)I.e. by
Up(s)＝UR(s)
7. Selecting a pressure ratio: the voltage ratio is the residual voltage U of the zinc oxide varistor sheet under the action of a specified value (e.g. l0kA) of surge current with the waveform of 8/20 mus10kAAnd initial operating voltage U1mAThe ratio of. The smaller the pressure ratio, the better the nonlinearity and the better the protection performance of the zinc oxide varistor. In general: pressure ratio of about 1.6～2.0。
8. Selecting the chargeability: the chargeability refers to the ratio of the amplitude of the maximum allowable continuous operation voltage to the initial action voltage, namely:
the chargeability is a parameter representing the voltage load degree on the zinc oxide varistor, and the selected chargeability has great influence on the aging speed of the zinc oxide varistor, and is generally 45-75%.
Further, in some embodiments of the present invention, the adjustable resistor 530 has a resistance value of 0 Ω -100 Ω.
It should be understood that: the resistance value range of the adjustable resistor 530 covers the range value of the line wave impedance of the power transmission cable 200, so that the resistance value of the adjustable resistor 530 is ensured to be the same as the line wave impedance of the power transmission cable 200 by adjusting the resistance value of the adjustable resistor, and impedance matching is realized.
Further, in some embodiments of the present invention, as shown in fig. 1, the anti-explosion branch 500 further includes a discharge gap 540 disposed on the anti-explosion wire 510, the discharge gap 540 is disposed between the second outlet terminal 330 and the pressure-sensitive valve sheet 520, and the discharge gap 540 is configured to be disconnected when no lightning voltage wave is generated in the power transmission cable 200; and is turned on when a lightning voltage wave is generated in the power transmission cable 200.
Through setting up discharge gap 540, can guarantee that when explosion-proof branch 500 is in the state of opening a circuit, no electric current passes through pressure-sensitive valve block 520, delays allergic valve block 520's ageing speed, improves allergic valve block 520's life.
It should be noted that: in some embodiments of the present invention, the discharge gap 540 is arranged in a vertical manner, and the gap of the discharge gap 540 is up to 10 μm.
Further, in order to ensure that the lightning voltage wave in the power transmission cable 200 is completely eliminated, and further improve the safety of the cable terminal 300, in some embodiments of the present invention, the cable terminal explosion-proof system 10 further includes a detection device and a control device, the detection device is configured to detect the voltage in the explosion-proof branch 500 and generate a voltage signal, the control device is communicatively connected to the detection device, and is configured to receive the voltage signal and determine whether the voltage signal is less than a threshold voltage, if the voltage signal is less than the threshold voltage, a close instruction is issued to control the circuit breaker 410 to close, and the explosion-proof branch 500 is in an open circuit state; if the voltage signal is greater than or equal to the threshold voltage, the anti-explosion branch 500 is in a short-circuit state.
Through the above arrangement, it can be ensured that the lightning voltage wave in the power transmission cable 200 is completely eliminated, and the safety of the cable terminal 300 is improved.
In some embodiments of the present invention, the threshold voltage is 0.
On the other hand, an embodiment of the present invention further provides a cable terminal explosion-proof method, which is applicable to the cable terminal explosion-proof system 10 described in any of the above embodiments, and as shown in fig. 2, the cable terminal explosion-proof method includes:
s201, when the photovoltaic power station 100 is struck by lightning, lightning voltage waves are generated in the power transmission cable 200, so that a circuit breaker 410 in the switch cabinet 400 is disconnected, and the anti-explosion branch 500 is in a short-circuit state, so that the lightning voltage waves generated by the lightning strike in the power transmission cable 200 are transmitted to a ground end through the anti-explosion branch 500;
s202, judging whether the lightning voltage waves in the power transmission cable 200 are eliminated or not, and if the lightning voltage waves in the power transmission cable 200 are eliminated, enabling the anti-explosion branch 500 to be in an open circuit state; if the lightning voltage wave in the power transmission cable 200 is not eliminated, the explosion-proof branch 500 assumes a short-circuit state.
Specifically, the explosion-proof branch 500 includes an explosion-proof trace 510 connecting the cable terminal 300 and the ground terminal, and a pressure-sensitive valve sheet 520 and an adjustable resistor 530 sequentially disposed on the explosion-proof trace 510,
s201 specifically comprises the following steps: when the photovoltaic power station 100 is struck by lightning, a lightning voltage wave is generated in the power transmission cable 200, and the circuit breaker 410 in the switch cabinet 400 is disconnected, so that the voltage-sensitive valve sheet 520 is conducted, and meanwhile, the resistance value is adjusted through the adjustable resistor 530, so that the impedance of the explosion-proof branch 500 is equal to the line wave impedance of the power transmission cable 200, and the lightning voltage wave generated by the lightning strike in the power transmission cable 200 is transmitted to the ground end through the explosion-proof branch 500;
s202 specifically comprises the following steps: detecting the voltage in the explosion-proof branch 500 by the detection device, generating a voltage signal, receiving the voltage signal by the control device, and judging whether the voltage signal is less than a threshold voltage, if the voltage signal is less than the threshold voltage, the thunder and lightning voltage wave in the power transmission cable 200 is eliminated, sending a closing instruction, controlling the circuit breaker 410 to be closed, enabling the switch cabinet 400 to work normally, and at the moment, the pressure-sensitive valve plate 520 is opened; if the voltage signal is greater than or equal to the threshold voltage, the lightning voltage wave in the power transmission cable 200 is not eliminated, and at this time, the voltage-sensitive valve sheet 520 is kept on, the explosion-proof branch 500 is in a short-circuit state, and the lightning voltage wave is continuously transmitted to the ground terminal through the explosion-proof branch 500.
According to the embodiment of the invention, by arranging the anti-explosion branch 500 connected between the cable terminal 300 and the ground terminal, when the photovoltaic power station 100 is struck by lightning and the breaker 410 is disconnected, the anti-explosion branch 500 is in a short-circuit state, so that the lightning voltage waves generated by the lightning strike in the power transmission cable 200 are transmitted to the ground terminal through the anti-explosion branch 500, and the lightning voltage waves are prevented from being reflected and superposed due to the disconnection of the breaker 410 caused by the lightning voltage waves, thereby preventing the cable terminal 300 from being exploded, and ensuring the safety of the power transmission cable 200 and the switch cabinet 400. Moreover, the anti-explosion branch 500 is also used for recovering to be in an open circuit state after the lightning voltage wave in the power transmission cable 200 is eliminated, so that the photovoltaic power station 100 can quickly recover to normally operate after being struck by lightning, the maintenance cost is reduced, and the safe and stable operation of the switch cabinet 400 is ensured.
The cable terminal explosion-proof system and method provided by the embodiment of the invention are described in detail above, a specific example is applied in the text to explain the principle and the embodiment of the invention, and the description of the above embodiment is only used to help understanding the method and the core idea of the invention; meanwhile, for those skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (10)
1. A cable terminal explosion-proof system is characterized by comprising a transmission cable, a cable terminal, a switch cabinet and an explosion-proof branch;
the two ends of the power transmission cable are respectively connected with the photovoltaic power station and the cable terminal;
the switch cabinet comprises a circuit breaker, and the circuit breaker is connected to the cable terminal;
the cable terminal comprises an inlet connecting terminal, a first outlet connecting terminal and a second outlet connecting terminal, the inlet connecting terminal is connected to the power transmission cable, the first outlet connecting terminal is connected to the circuit breaker, and the second outlet connecting terminal is connected to the explosion-proof branch;
when the cable terminal normally operates, the explosion-proof branch circuit is in an open circuit state; when the photovoltaic power station is struck by lightning, the breaker is disconnected, the explosion-proof branch circuit is in a short-circuit state, and therefore lightning voltage waves generated by the lightning strike in the power transmission cable are transmitted to the grounding end through the explosion-proof branch circuit.
2. The cable termination explosion-proof system of claim 1, wherein the explosion-proof branch comprises an explosion-proof wire connecting a second outlet connection terminal and the ground terminal, and a pressure-sensitive valve plate and an adjustable resistor sequentially arranged on the explosion-proof wire;
the pressure-sensitive valve plate is used for being disconnected when the lightning voltage wave is not generated in the power transmission cable; conducting when the lightning voltage wave is generated in the power transmission cable;
and the adjustable resistor is used for matching the resistance of the explosion-proof branch with the line wave impedance of the transmission cable when the pressure-sensitive valve plate is conducted.
3. The cable termination explosion-proof system of claim 2, wherein the explosion-proof branch further comprises a discharge gap disposed on the explosion-proof trace, the discharge gap being disposed between the second outlet terminal and the pressure-sensitive valve sheet, the discharge gap being configured to open when the lightning voltage wave is not generated in the power transmission cable; conducting when the lightning voltage wave is generated in the power transmission cable.
4. The cable termination explosion-proof system according to claim 1, further comprising a detection device and a control device, wherein the detection device is configured to detect a voltage in the explosion-proof branch and generate a voltage signal, and the control device is communicatively connected to the detection device and configured to receive the voltage signal and determine whether the voltage signal is less than a threshold voltage, and if the voltage signal is less than the threshold voltage, a close command is issued to control the circuit breaker to close and the explosion-proof branch is in an open circuit state; and if the voltage signal is greater than or equal to the threshold voltage, the explosion-proof branch circuit is in a short-circuit state.
5. The cable termination explosion-proof system of claim 4, wherein the line wave impedance Z of the power transmission cable is:
wherein, mu0Magnetic permeability in vacuum; mu.srIs relative magnetic permeability; epsilon0Dielectric constant of vacuum or gas; epsilonrIs a relative dielectric constant; h iscIs the height between the transmission cable and the ground; r is the radius of the transmission cable.
6. The cable termination explosion-proof system of claim 2, wherein the pressure-sensitive valve sheet is further configured to open after the lightning voltage wave in the explosion-proof trace is eliminated, so that the explosion-proof branch circuit assumes the open circuit state.
7. The cable termination explosion-proof system of claim 6, wherein the varistor sheet is a zinc oxide varistor sheet, and the voltage-current characteristic of the zinc oxide varistor sheet is:
u＝Ciδ
where u is the voltage, i is the current, C is the material constant, and δ is the nonlinear exponent.
8. The cable termination explosion-proof system of claim 3, wherein the arrangement of the discharge gaps is a vertical arrangement and the gap of the discharge gaps is up to 10 μm.
9. The cable termination explosion-proof system of claim 2, wherein the adjustable resistor has a resistance value of 0 Ω -100 Ω.
10. A cable termination explosion-proof method applied to the cable termination explosion-proof system according to any one of claims 1 to 9, comprising:
when a photovoltaic power station is struck by lightning, lightning voltage waves are generated in a power transmission cable, a circuit breaker in a switch cabinet is disconnected, and the explosion-proof branch circuit is in a short-circuit state, so that the lightning voltage waves generated by the lightning strike in the power transmission cable are transmitted to a grounding end through the explosion-proof branch circuit;
judging whether the lightning voltage waves in the power transmission cable are eliminated or not, and if the lightning voltage waves in the power transmission cable are eliminated, enabling the explosion-proof branch circuit to be in an open circuit state; and if the lightning voltage wave in the power transmission cable is not eliminated, the anti-explosion branch circuit is in a short-circuit state.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110484236.7A CN113346364A (en) | 2021-04-30 | 2021-04-30 | Cable terminal explosion-proof system and method |
| AU2021103063A AU2021103063A4 (en) | 2021-04-30 | 2021-06-03 | Cable terminal explosion protection system and method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110484236.7A CN113346364A (en) | 2021-04-30 | 2021-04-30 | Cable terminal explosion-proof system and method |
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| CN113346364A true CN113346364A (en) | 2021-09-03 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110484236.7A Pending CN113346364A (en) | 2021-04-30 | 2021-04-30 | Cable terminal explosion-proof system and method |
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| CN (1) | CN113346364A (en) |
| AU (1) | AU2021103063A4 (en) |
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| AU2021103063A4 (en) | 2021-07-15 |
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