CN111934283A - Superconducting cable fault self-recovery control method - Google Patents

Superconducting cable fault self-recovery control method Download PDF

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CN111934283A
CN111934283A CN202010749868.7A CN202010749868A CN111934283A CN 111934283 A CN111934283 A CN 111934283A CN 202010749868 A CN202010749868 A CN 202010749868A CN 111934283 A CN111934283 A CN 111934283A
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superconducting cable
fault
value
current
quench
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CN111934283B (en
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何晓峰
程韧俐
郑晓辉
吴新
陈择栖
林子钊
马伟哲
史军
程维杰
翁毅选
张安龙
刘金生
齐晖
黄双
张哲�
黄鸿奕
张臻哲
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Shenzhen Power Supply Bureau Co Ltd
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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
    • H02H7/001—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 superconducting apparatus, e.g. coils, lines, machines
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/60—Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment

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Abstract

The invention provides a self-recovery control method for a superconducting cable fault, which is used for obtaining a phase current sudden change amount, a phase current effective value and a line voltage value at the installation position of a superconducting cable protection device and judging the cause of the quench; calculating the heating cumulant of the superconducting cable according to the detected short-circuit protection action signal, and detecting whether the external fault is removed; comparing the phase current effective value with a no-current threshold value, and judging whether the superconducting cable exits the operation or not according to the comparison result; calculating the quench recovery time of the superconducting cable corresponding to the current heat accumulation according to the current heat accumulation of the superconducting cable; and detecting whether the condition of restarting the superconducting cable is met. The invention avoids the superconducting cable from continuously running in the quench state after the external fault is removed, so as to reduce the heating and reduce the quench recovery time of the superconducting cable, and meanwhile, the superconducting cable is put into operation again after the superconducting state is recovered, so as to improve the power supply reliability of a power grid.

Description

Superconducting cable fault self-recovery control method
Technical Field
The invention relates to the technical field of superconducting cables, in particular to a self-recovery control method for a fault of a superconducting cable.
Background
Compared with the conventional cable, the superconducting cable has the advantages of low line loss, large transmission capacity, small corridor occupation area, environmental friendliness and the like, and provides an efficient, compact, reliable and green electric energy transmission mode for a power grid. However, when a short-circuit fault occurs in adjacent elements of the superconducting cable, the overall loss time of the cable is over, and if the short-circuit current is too large or the duration is longer and exceeds the current-carrying capacity of the superconducting cable, the superconducting cable needs to be cut continuously, so that the power supply is interrupted. The superconducting cable quench fault caused by the adjacent line short circuit has self-recovery capability, so once the superconducting cable body recovers the superconducting state, the switch is switched on in time to be put into operation, and the power supply reliability of a power grid can be effectively improved.
For the protection problem of the quench fault of the superconducting cable caused by the short-circuit current, the existing related research mainly focuses on the detection and protection of the quench fault, for example: a quench protection method (SEEBER B. hand book of applied superconducting [ M ] Bristol and Philadelphia: Institute of Physics Publishing,1998: 527-555) for reacting to increase of resistance after quench of a superconductor and increasing voltage drop across the conductor, provides an overcurrent quench protection scheme that adopts different countermeasures according to the overcurrent level of a superconducting cable. However, the above research mainly aims at the detection and protection of the quench fault, and does not consider the problem of switching-on input control of the superconducting cable after the quench fault is self-recovered.
Disclosure of Invention
The invention aims to provide a superconducting cable fault self-recovery control method, which reduces the quench recovery time of a superconducting cable, and puts the superconducting cable into a superconducting state again after the superconducting cable recovers the superconducting state, so as to solve the technical problems that the existing method aims at the detection and protection of the quench fault and the control problem of switching-on input of the superconducting cable after the quench fault self-recovery is not considered.
In one aspect of the present invention, there is provided a superconducting cable fault self-recovery control method, including:
step S1, obtaining the electrical property of the installation position of the superconducting cable protection device, wherein the electrical property at least comprises a phase current abrupt change amount, a phase current effective value and a line voltage value;
step S2, comparing the phase current abrupt change quantity with a first set threshold, judging whether a starting action exists according to the comparison result, if so, detecting whether the quench reason is a short-circuit fault for the first time, and generating a short-circuit protection action signal or acquiring the electrical property of the installation position of the protection device again according to the first detection result; if the starting action does not exist, detecting whether the quench reason is short-circuit current impact for the second time, and generating a short-circuit protection action signal or re-acquiring the electrical property of the installation position of the protection device according to the second detection result;
step S3, detecting a short-circuit protection operation signal, and if receiving the short-circuit protection operation signal, locking the superconducting cable and putting it into operation again; if the short-circuit protection action signal is not received, marking a protection starting mark on the superconducting cable;
step S4, calculating the heating cumulant of the superconducting cable, detecting whether the external fault is cut off, if the external fault is cut off, sending a command of cutting off the superconducting cable, and putting a mark again for the superconducting cable mark; if the external fault is not removed, detecting the fault duration and judging whether the adjacent element protection/circuit breaker fails according to the detected fault duration;
step S5, comparing the phase current effective value with the no-current threshold value, and judging whether the superconducting cable quits operation according to the comparison result; if the superconducting cable quits running, calculating the superconducting cable quench recovery time corresponding to the current heat accumulation according to the current heat accumulation of the superconducting cable, and starting timing;
step S6, when the timing time reaches the superconducting cable quench recovery time corresponding to the current heat accumulation amount, detecting whether the condition of the superconducting cable re-investment is satisfied, if so, sending a re-investment signal; if not, the lock is locked and put again.
Preferably, the step S2 includes:
the phase current abrupt change amount
Figure BDA0002609656760000021
With a mutation amount threshold value delta isetComparing, if the phase current abrupt change quantity is
Figure BDA0002609656760000022
If the continuous N points satisfy the following formula, judging that the starting action exists:
Figure BDA0002609656760000031
wherein the content of the first and second substances,
Figure BDA0002609656760000032
is a phase current abrupt change amount in which,
Figure 100002_1
Δisetis a mutation amount threshold; and N is a phase current mutation measurement value node, wherein the value range of N is 3-5.
Preferably, the step S2 includes:
during the first detection, comparing the effective value of any phase current with the critical current value of the superconducting cable, and if the effective value of any phase current is greater than the critical current value of the superconducting cable, judging that the failure cause is short-circuit fault and generating a short-circuit protection action signal; and if the effective value of any phase current is not greater than the critical current value of the superconducting cable, judging that the quench reason is not a short-circuit fault, and acquiring the electrical property at the installation position of the protection device again to judge the electrical property values one by one.
Preferably, the step S2 includes:
during the second detection, comparing the effective value of any phase current with the critical current value of the superconducting cable, and judging that the quenching reason is short-circuit current impact and generating a short-circuit protection action signal if the true effective value of any phase current continuously exceeds the critical current value in two power frequency periods; if the true effective value of any phase current cannot continuously exceed the critical current value, judging that the quench reason is not short-circuit current impact, and acquiring the electrical attribute of the installation position of the protection device again to judge the electrical attribute values one by one.
Preferably, the step S4 includes:
calculating the heat generation cumulative quantity of each phase of the superconducting cable according to the following formula:
Figure BDA0002609656760000034
wherein the content of the first and second substances,
Figure BDA0002609656760000035
is composed of
Figure BDA0002609656760000036
Accumulating the results of the calculation for the last heating of the phase;
Figure BDA0002609656760000037
is composed of
Figure BDA0002609656760000038
Latest current sample value of a phase,. DELTA.t, is the sampling interval, RsetThe superconducting cable is a steady state quench resistor.
Preferably, the step S4 includes:
when detecting whether the external fault is removed, judging whether the protection device meets the condition that the phase current effective value of each phase is lower than the critical current and the line voltage value of each phase is greater than the voltage recovery threshold value; if each phase of the protection device meets the condition, judging that the external fault is removed, sending a command of removing the superconducting cable, and putting marks on the superconducting cable marks again; if each phase of the protection device does not meet the condition, detecting the fault duration and removing the fault time according to whether the detected fault duration is greater than the main protection action of the adjacent element; if the fault duration is longer than the fault removing time of the main protection action of the adjacent element, judging that the adjacent element protection/circuit breaker refuses to act, and sending a command of removing the superconducting cable; and if the fault duration time is not longer than the fault clearing time of the main protection action of the adjacent element, newly acquiring the electrical attribute of the installation position of the protection device and judging the electrical attribute values one by one.
Preferably, the adjacent element main protection action fault clearing time comprises an adjacent element main protection action time and a breaker full-open time.
Preferably, the step S5 includes:
determining the current heat accumulation of the superconducting cable according to a preset quench recovery time table of the superconducting cable and the heat accumulation of each phase of the superconducting cable;
calculating the corresponding superconducting cable quench recovery time according to the following formula:
Figure BDA0002609656760000041
Figure BDA0002609656760000042
wherein Q isi.setAnd ti.setSetting parameter values for a superconducting cable quench recovery schedule; t is the quench recovery time of the superconducting cable;
Figure BDA0002609656760000043
the cumulative amount of heat generation of the superconducting cable.
Preferably, in step S6, the detecting the condition of resuming the superconducting cable specifically includes that a cryogenic refrigeration system for cooling the superconducting cable is ready and a cryogenic refrigeration system ready signal is sent, and the bus voltage of the cryogenic refrigeration system and the flow, temperature, and pressure of the liquid nitrogen are normal.
Preferably, the step S6 includes:
when the bus voltage of the low-temperature refrigeration system meets the following formula, the bus voltage is in a normal state:
{(UL≤UAB≤UH)∩(UL≤UBC≤UH)∩(UL≤UCA≤UH)}
when the flow, the temperature and the pressure of the liquid nitrogen of the low-temperature refrigeration system meet the following formulas, the flow, the temperature and the pressure of the liquid nitrogen of the low-temperature refrigeration system are in a normal state:
{(qL≤q≤qH)∩(TL≤T≤TH)∩(PL≤P≤PH)}
wherein, ULA voltage low constant value; u shapeHThe voltage is high and constant; q. q.sLThe flow is low and constant; q. q.sHA high flow constant value; t isLThe flow is low and constant; t isHA high flow constant value; pLFor low flow rateA value; pHThe flow rate is high.
In summary, the embodiment of the invention has the following beneficial effects:
the self-recovery control method for the fault of the superconducting cable is suitable for superconducting cables with different structures, and can effectively deal with the superconducting cable quench fault caused by the short circuit of adjacent elements; after external faults are removed, the superconducting cable is removed through successive actions, so that the operation safety of the superconducting cable can be ensured, and the quench recovery time of the superconducting cable is reduced; after the superconducting cable recovers the superconducting state, the superconducting cable is put into operation again, and the power supply reliability of the power grid can be improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art 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 within the scope of the present invention for those skilled in the art to obtain other drawings based on the drawings without inventive exercise.
Fig. 1 is a schematic main flow diagram of a superconducting cable fault self-recovery control method provided by the invention.
Fig. 2 is a logic diagram of a superconducting cable fault self-recovery control method provided by the invention.
Fig. 3 is a schematic view of a power grid of a superconducting cable according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings.
Fig. 1 and fig. 2 are schematic diagrams illustrating an embodiment of a method for controlling self-recovery of a superconducting cable from a fault according to the present invention. In this embodiment, the method comprises the steps of:
step S1, obtaining the electrical property of the installation position of the superconducting cable protection device, wherein the electrical property at least comprises a phase current abrupt change amount, a phase current effective value and a line voltage value;
step S2, comparing the phase current abrupt change with a first set threshold, judging whether a starting action exists according to the comparison result, if so, detecting whether the cause of quench is a short-circuit fault for the first time, and generating a short-circuit protection action signal (performing step S3) or acquiring the electrical property of the installation place of the protection device again (performing step S1) according to the first detection result; if the starting action does not exist, detecting whether the quenching reason is short-circuit current impact for the second time, and generating a short-circuit protection action signal according to the second detection result (carrying out step S3) or acquiring the electrical property of the installation place of the protection device again (carrying out step S1);
in a specific embodiment, the phase current sudden change amount
Figure BDA0002609656760000061
With a mutation amount threshold value delta isetComparing, if the phase current abrupt change quantity is
Figure BDA0002609656760000062
If the continuous N points satisfy the following formula, judging that the starting action exists:
Figure BDA0002609656760000063
wherein the content of the first and second substances,
Figure BDA0002609656760000064
is a phase current abrupt change amount in which,
Figure 2
Δisetis a mutation amount threshold; n is a phase current mutation measuring value node, wherein the value range of N is 3-5;
specifically, during the first detection, the effective value of any phase current is determined
Figure BDA0002609656760000066
And critical current value I of superconducting cablecrComparing if any phase current effective value
Figure BDA0002609656760000067
Greater than the critical current value I of the superconducting cablecrIf so, judging that the quench reason is a short-circuit fault, and generating a short-circuit protection action signal; effective value of any phase current
Figure BDA0002609656760000068
Not more than critical current value I of the superconducting cablecrJudging whether the quench reason is a short-circuit fault, and acquiring the electrical attribute of the installation position of the protection device again to judge the electrical attribute values one by one;
during the second detection, the effective value of any phase current is determined
Figure BDA0002609656760000069
And critical current value I of superconducting cablecrComparing, in two power frequency periods, if any phase current is true effective value
Figure BDA00026096567600000610
Continuously exceeding the critical current value IcrIf so, judging that the quench reason is short-circuit current impact, and generating a short-circuit protection action signal; if any phase current is true value
Figure BDA00026096567600000611
Can not continuously exceed the critical current value I of the superconducting cablecrAnd judging whether the quench reason is short-circuit current impact, and acquiring the electrical property at the installation position of the protection device again to judge the electrical property values one by one.
Step S3, detecting a short-circuit protection operation signal, and if receiving the short-circuit protection operation signal, locking the superconducting cable and putting it into operation again; if the short-circuit protection action signal is not received, marking a protection starting mark on the superconducting cable;
step S4, calculating the heating cumulant of the superconducting cable, detecting whether the external fault is cut off, if the external fault is cut off, sending a command of cutting off the superconducting cable, and putting a mark again for the superconducting cable mark; if the external fault is not removed, detecting the fault duration and judging whether the adjacent element protection/circuit breaker fails according to the detected fault duration;
in a specific embodiment, the cumulative amount of heat generation of each phase of the superconducting cable is calculated according to the following formula:
Figure BDA0002609656760000071
wherein the content of the first and second substances,
Figure BDA0002609656760000072
is composed of
Figure BDA0002609656760000073
Accumulating the results of the calculation for the last heating of the phase;
Figure BDA0002609656760000074
is composed of
Figure BDA0002609656760000075
Latest current sample value of a phase,. DELTA.t, is the sampling interval, RsetThe superconducting cable is a steady state quench resistor;
specifically, when detecting whether the external fault is removed, judging whether the protection device meets the condition that the phase current effective value of each phase is lower than the critical current and the line voltage value of each phase is greater than the voltage recovery threshold value; if each phase of the protection device meets the condition, judging that the external fault is removed, sending a command of removing the superconducting cable, and putting marks on the superconducting cable marks again; if each phase of the protection device does not meet the condition, detecting the fault duration and removing the fault time according to whether the detected fault duration is greater than the main protection action of the adjacent element; if the fault duration is longer than the fault removing time of the main protection action of the adjacent element, judging that the adjacent element protection/circuit breaker refuses to act, and sending a command of removing the superconducting cable; if the fault duration is not longer than the fault clearing time of the main protection action of the adjacent element, newly acquiring the electrical property of the installation position of the protection device and judging the electrical property values one by one (step S1); and the adjacent element main protection action fault clearing time comprises adjacent element main protection action time and breaker full-open-close time.
Step S5, comparing the phase current effective value with the no-current threshold value, and judging whether the superconducting cable quits operation according to the comparison result; if the superconducting cable quits running, calculating the superconducting cable quench recovery time corresponding to the current heat accumulation according to the current heat accumulation of the superconducting cable, and starting timing;
in the specific embodiment, the current heating cumulant of the superconducting cable is determined according to a preset superconducting cable quench recovery time table and the heating cumulant of each phase of the superconducting cable;
calculating the corresponding superconducting cable quench recovery time by a linear interpolation method according to the following formula:
Figure BDA0002609656760000076
Figure BDA0002609656760000077
wherein Q isi.setAnd ti.setSetting parameter values for a superconducting cable quench recovery schedule; t is the quench recovery time of the superconducting cable;
Figure BDA0002609656760000078
cumulative amount of heat generated for superconducting cable
Step S6, when the timing time reaches the superconducting cable quench recovery time corresponding to the current heat accumulation amount, detecting whether the condition of the superconducting cable re-investment is satisfied, if so, sending a re-investment signal; if not, locking and putting again;
in a specific embodiment, the detecting the condition of the superconducting cable being put into operation again specifically includes that a cryogenic refrigeration system for cooling the superconducting cable is ready and sends a cryogenic refrigeration system ready signal, and the bus voltage of the cryogenic refrigeration system and the flow, temperature and pressure of liquid nitrogen are normal;
when the bus voltage of the low-temperature refrigeration system meets the following formula, the bus voltage is in a normal state:
{(UL≤UAB≤UH)∩(UL≤UBC≤UH)∩(UL≤UCA≤UH)}
when the flow, the temperature and the pressure of the liquid nitrogen of the low-temperature refrigeration system meet the following formulas, the flow, the temperature and the pressure of the liquid nitrogen of the low-temperature refrigeration system are in a normal state:
{(qL≤q≤qH)∩(TL≤T≤TH)∩(PL≤P≤PH)}
wherein, ULA voltage low constant value; u shapeHThe voltage is high and constant; q. q.sLThe flow is low and constant; q. q.sHA high flow constant value; t isLThe flow is low and constant; t isHA high flow constant value; pLThe flow is low and constant; pHThe flow rate is high.
In one embodiment of the present invention, as shown in fig. 3, a schematic diagram of a power grid model of a superconducting cable is shown, wherein the power grid model generates an AB two-phase metallic ground short circuit at a point f1 of an outlet f of a 10kV feeder L3; the basic parameters of the power grid simulation model are explained as follows:
the parameters of the equivalent power supply are as follows: equivalent internal potential Es10.5kV, equivalent internal impedance Zs＝0.258∠80°Ω。
The parameters per unit length of the 10kV feeders L1, L2, and L3 are: r is(1)＝r(2)＝0.103Ω/km，x(1)＝ x(2)＝0.069Ω/km，r(0)＝0.253Ω/km，x(0)The lengths of L1, L2, and L3 are 0.5km, 8km, and 5km, respectively, at 0.242 Ω/km; the operation time of the time-limited current quick-break protection of L2 and L3 is 0.3 s.
The load parameters are as follows: load 1: 10+ j3 MVA, Load 2: 10+ j5 MVA.
The parameters of the superconducting cable are: l isA＝2.46μH/m，LB＝1.91μH/m，LC＝1.53μH/m， LAB＝0.77μH/m，LBC＝0.59μH/m，LCA＝0.97μH/m，Quench resistance R is 0.05 omega/m, critical current IcrA preset quench recovery schedule for the superconducting cable, 6kA, is shown in the following table:
Figure BDA0002609656760000081
the following is a control method of an embodiment of the present invention to reflect a superconducting cable quench fault caused by short circuit of adjacent elements, and automatically perform closing control after the cable recovers a superconducting state, specifically as follows:
(1) obtaining phase current abrupt change (delta i) of superconducting cable quench protection installation positionA，ΔiB，ΔiC) True effective value of phase current (I)A.RMS，IB.RMS，IC.RMS) Line voltage (U)AB，UBC，UCA)。
(2) Comparing the sudden change of the phase current with a sudden change threshold value, finding delta iA>ΔisetAnd Δ iB>Δiset(ii) a Comparing the phase current true effective value with the critical current of the superconducting cable, finding IA.RMS>IcrAnd IB.RMS>IcrTherefore, the superconducting cable can be judged to be quenched due to short-circuit current impact.
(3) And acquiring a short-circuit protection action signal of the superconducting cable, finding that the short-circuit protection of the superconducting cable does not act, and setting a protection starting mark.
(4) The heat generation accumulation of each phase of the superconducting cable is calculated, and whether or not an external fault has been removed is detected. Finally after about 0.32s it was found that:
satisfies the current drop criterion { (I)A.RMS<Icr)∩(IB.RMS<Icr)∩(IC.RMS<Icr) And satisfy a voltage recovery criterion (U)AB>Uset)∩(UBC>Uset)∩(UCA>Uset) And judging that the external fault is removed, sending a command of removing the superconducting cable, and resetting a drop-in mark.
(5) Comparing the phase current true effective value with the no-current threshold value to find IA.RMS、IB.RMSAnd IC.RMSAre all less than IsetAnd judging that the superconducting cable exits from operation, and stopping heat accumulation calculation. At this time, the heat generation accumulation calculation result is: qA＝2.79MJ、QA＝2.83MJ、QC0 MJ; calculating the corresponding superconducting cable quench recovery time t by a linear interpolation method according to the superconducting cable quench recovery time table and the heat accumulation calculation results of each phase of the superconducting cable:
Figure BDA0002609656760000091
Figure BDA0002609656760000092
tC＝0(min)
t＝max(tA,tB,tC)＝46.65(min)
(6) waiting for the timing time to reach the quench recovery time of 46.65 minutes, then detecting whether the cryogenic refrigeration system is ready and whether the bus voltage and the flow, temperature and pressure of liquid nitrogen are normal, if so, judging that the condition of the heavy input of the superconducting cable is met, and sending a heavy input signal; if not, locking and heavy investment are carried out.
In summary, the embodiment of the invention has the following beneficial effects:
the self-recovery control method for the fault of the superconducting cable is suitable for superconducting cables with different structures, and can effectively deal with the superconducting cable quench fault caused by the short circuit of adjacent elements; after external faults are removed, the superconducting cable is removed through successive actions, so that the operation safety of the superconducting cable can be ensured, and the quench recovery time of the superconducting cable is reduced; after the superconducting cable recovers the superconducting state, the superconducting cable is put into operation again, and the power supply reliability of the power grid can be improved.
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims (10)

1. A superconducting cable fault self-recovery control method is characterized by comprising the following steps:
step S1, obtaining the electrical property of the installation position of the superconducting cable protection device, wherein the electrical property at least comprises a phase current abrupt change amount, a phase current effective value and a line voltage value;
step S2, comparing the phase current abrupt change quantity with a first set threshold, judging whether a starting action exists according to the comparison result, if so, detecting whether the quench reason is a short-circuit fault for the first time, and generating a short-circuit protection action signal or acquiring the electrical property of the installation position of the protection device again according to the first detection result; if the starting action does not exist, detecting whether the quench reason is short-circuit current impact for the second time, and generating a short-circuit protection action signal or re-acquiring the electrical property of the installation position of the protection device according to the second detection result;
step S3, detecting a short-circuit protection operation signal, and if receiving the short-circuit protection operation signal, locking the superconducting cable and putting it into operation again; if the short-circuit protection action signal is not received, marking a protection starting mark on the superconducting cable;
step S4, calculating the heating cumulant of the superconducting cable, detecting whether the external fault is cut off, if the external fault is cut off, sending a command of cutting off the superconducting cable, and putting a mark again for the superconducting cable mark; if the external fault is not removed, detecting the fault duration and judging whether the adjacent element protection/circuit breaker fails according to the detected fault duration;
step S5, comparing the phase current effective value with the no-current threshold value, and judging whether the superconducting cable quits operation according to the comparison result; if the superconducting cable quits running, calculating the superconducting cable quench recovery time corresponding to the current heat accumulation according to the current heat accumulation of the superconducting cable, and starting timing;
step S6, when the timing time reaches the superconducting cable quench recovery time corresponding to the current heat accumulation amount, detecting whether the condition of the superconducting cable re-investment is satisfied, if so, sending a re-investment signal; if not, the lock is locked and put again.
2. The method of claim 1, wherein the step S2 includes:
the phase current abrupt change amount
Figure FDA0002609656750000021
With a mutation amount threshold value delta isetComparing, if the phase current abrupt change quantity is
Figure FDA0002609656750000022
If the continuous N points satisfy the following formula, judging that the starting action exists:
Figure FDA0002609656750000023
wherein the content of the first and second substances,
Figure FDA0002609656750000024
is a phase current abrupt change amount in which,
Figure 1
Δisetis a mutation amount threshold; and N is a phase current mutation measurement value node, wherein the value range of N is 3-5.
3. The method of claim 2, wherein the step S2 includes:
during the first detection, comparing the effective value of any phase current with the critical current value of the superconducting cable, and if the effective value of any phase current is greater than the critical current value of the superconducting cable, judging that the failure cause is short-circuit fault and generating a short-circuit protection action signal; and if the effective value of any phase current is not greater than the critical current value of the superconducting cable, judging that the quench reason is not a short-circuit fault, and acquiring the electrical property at the installation position of the protection device again to judge the electrical property values one by one.
4. The method of claim 3, wherein the step S2 includes:
during the second detection, comparing the effective value of any phase current with the critical current value of the superconducting cable, and judging that the quenching reason is short-circuit current impact and generating a short-circuit protection action signal if the true effective value of any phase current continuously exceeds the critical current value in two power frequency periods; if the true effective value of any phase current cannot continuously exceed the critical current value of the superconducting cable, judging that the quench reason is not short-circuit current impact, and acquiring the electrical property of the installation position of the protection device again to judge the electrical property values one by one.
5. The method of claim 4, wherein the step S4 includes:
calculating the heat generation cumulative quantity of each phase of the superconducting cable according to the following formula:
Figure FDA0002609656750000026
wherein the content of the first and second substances,
Figure FDA0002609656750000027
is composed of
Figure FDA0002609656750000028
Accumulating the results of the calculation for the last heating of the phase;
Figure FDA0002609656750000029
is composed of
Figure FDA00026096567500000210
Latest current sample value of a phase,. DELTA.t, is the sampling interval, RsetThe superconducting cable is a steady state quench resistor.
6. The method of claim 5, wherein the step S4 includes:
when detecting whether the external fault is removed, judging whether the protection device meets the condition that the phase current effective value of each phase is lower than the critical current and the line voltage value of each phase is greater than the voltage recovery threshold value; if each phase of the protection device meets the condition, judging that the external fault is removed, sending a command of removing the superconducting cable, and putting marks on the superconducting cable marks again; if each phase of the protection device does not meet the condition, detecting the fault duration and removing the fault time according to whether the detected fault duration is greater than the main protection action of the adjacent element; if the fault duration is longer than the fault removing time of the main protection action of the adjacent element, judging that the adjacent element protection/circuit breaker refuses to act, and sending a command of removing the superconducting cable; and if the fault duration time is not longer than the fault clearing time of the main protection action of the adjacent element, newly acquiring the electrical attribute of the installation position of the protection device and judging the electrical attribute values one by one.
7. The method of claim 6, wherein the adjacent element primary protection action clearing fault time comprises an adjacent element primary protection action time and a circuit breaker full open time.
8. The method of claim 7, wherein the step S5 includes:
determining the current heat accumulation of the superconducting cable according to a preset quench recovery time table of the superconducting cable and the heat accumulation of each phase of the superconducting cable;
calculating the corresponding superconducting cable quench recovery time according to the following formula:
Figure FDA0002609656750000031
Figure FDA0002609656750000032
wherein Q isi.setAnd ti.setIs superconductingParameter values given by a cable quench recovery schedule; t is the quench recovery time of the superconducting cable;
Figure FDA0002609656750000033
the cumulative amount of heat generation of the superconducting cable.
9. The method as claimed in claim 1, wherein the step S6, the detecting the condition of resuming the superconducting cable specifically includes that a cryogenic refrigeration system for cooling the superconducting cable is ready and sending a cryogenic refrigeration system ready signal, and the bus voltage of the cryogenic refrigeration system and the flow, temperature and pressure of the liquid nitrogen are normal.
10. The method of claim 9, wherein the step S6 includes:
when the bus voltage of the low-temperature refrigeration system meets the following formula, the bus voltage is in a normal state:
{(UL≤UAB≤UH)∩(UL≤UBC≤UH)∩(UL≤UCA≤UH)}
when the flow, the temperature and the pressure of the liquid nitrogen of the low-temperature refrigeration system meet the following formulas, the flow, the temperature and the pressure of the liquid nitrogen of the low-temperature refrigeration system are in a normal state:
{(qL≤q≤qH)∩(TL≤T≤TH)∩(PL≤P≤PH)}
wherein, ULA voltage low constant value; u shapeHThe voltage is high and constant; q. q.sLThe flow is low and constant; q. q.sHA high flow constant value; t isLThe flow is low and constant; t isHA high flow constant value; pLThe flow is low and constant; pHThe flow rate is high.
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