CN110703014A - Capacitor monitoring method based on open delta voltage - Google Patents
Capacitor monitoring method based on open delta voltage Download PDFInfo
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- CN110703014A CN110703014A CN201910921626.9A CN201910921626A CN110703014A CN 110703014 A CN110703014 A CN 110703014A CN 201910921626 A CN201910921626 A CN 201910921626A CN 110703014 A CN110703014 A CN 110703014A
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Abstract
The invention relates to the technical field of circuit monitoring, in particular to a capacitor monitoring method based on open delta voltage, which utilizes the existing signals of a capacitor device and protection thereof to realize high-precision test and fault location of capacitor faults, introduces three-phase line voltage of a system, combines the open delta voltage to obtain a judgment state quantity, improves the judgment precision of the faults and obtains fault position information; converting the system line voltage into a positive sequence voltage and a negative sequence voltage, expressing the positive sequence voltage and the negative sequence voltage into a complex form, expressing the open triangular voltage into the complex form, and calculating a discrimination coefficient; the discrimination coefficient is only related to the impedance of the monitored capacitor bank; the judgment quantity is the difference of the judgment coefficients at different times; the threshold value of the discrimination coefficient is 0.0005 to 1 time of the phase capacity change rate after the single element is broken down; and judging the phase sequence of the component breakdown according to the position of the maximum value of the three-phase discrimination coefficient.
Description
Technical Field
The invention relates to the technical field of circuit monitoring, in particular to a capacitor monitoring method based on open delta voltage.
Background
At present, the internal protection methods of high-voltage power capacitors are all unbalanced protection, and the monitoring method generally adopts a scheme of monitoring capacitor units one by one, namely monitoring parameters such as voltage, current and temperature of each capacitor and judging whether the capacitor fails, and the method has various defects and mainly comprises the following steps: the number of the capacitor units is too large in one set of capacitor device, and the capacitor units are usually contained in a large number, and according to the voltage grade and the capacity of a transformer substation, the number of the capacitor units contained in one set of capacitor device is about 25 to 50 in a high-voltage transformer substation, and is up to hundreds in an extra-high voltage transformer substation and an extra-high voltage transformer substation. Therefore, each capacitor unit needs to be monitored, related monitoring equipment needs to be installed on all the capacitor units, a communication system and a software platform with large node number are built, and the system is high in difficulty, high in complexity, high in cost and difficult to construct and install. High-voltage capacitors with high test terminal complexity are often mounted on a high-voltage insulating platform, and each capacitor is provided with a monitoring terminal, so that the problems of energy taking, communication, heat dissipation and the like of the terminal need to be solved. Because the voltage difference of tens of kilovolts exists between the insulating platform and the ground, the cable cannot be directly laid from the ground to the insulating platform, the technologies such as local induction energy taking, wireless communication and the like are generally adopted, the capacitor often runs outdoors and is seriously influenced by sunlight, wind, rain and the like, special design needs to be carried out on water resistance, heat dissipation, weather resistance and the like, and the technical complexity of the test terminal is very high due to the factors. Influence on primary wiring parameters such as voltage, current, and temperature are measured for each capacitor, and it is inevitable to install a sensor such as a transformer or a coil at a terminal of the capacitor, which may adversely affect reliability, creepage distance, and mechanical strength of the primary wiring of the capacitor. Due to the fact that the number of the high-voltage power capacitors is large, the technical complexity of the terminal device is high, the overall reliability and the service life of a hardware system are reduced, the design life of the high-voltage power capacitor reaches 20 years to 30 years, and the failure rate is low under normal working conditions. Electronic devices generally have a lifetime of only 3 to 5 years in an outdoor environment and a high failure rate. Therefore, the scheme of monitoring each capacitor may cause the problem that the hardware maintenance workload and the maintenance cost of the monitoring system are larger than those of the capacitor. The internal protection methods of the capacitor adopted at present are all unbalanced protection, are ineffective for symmetric faults of a capacitor device, are low in monitoring data information quantity, cannot evaluate the operation condition of the capacitor, and cannot position the fault capacitor. The capacitor may still have serious failures such as unplanned shutdown, explosion and fire, etc., and the maintenance efficiency after trip is too low. For high voltage capacitor devices of 10kV and below, Y-wiring with ungrounded neutral and open delta protection are typically used, and the device itself needs to measure bus line voltage and phase current.
Disclosure of Invention
The present invention is directed to a capacitor monitoring method based on open delta voltage, which solves one or more of the above-mentioned drawbacks of the prior art.
In order to achieve the purpose, the invention provides the following technical scheme:
a capacitor monitoring method based on open delta voltage comprises the following steps:
s1: first measuring the open delta voltage
And three phase line voltage
S2: calculating the complex form of the open delta voltage0+jV0And calculating three-sequence components of the three-phase line voltage and converting the three-sequence components into a complex form of U10+jV10、U20+jV20；
S3: calculating the discrimination coefficient at the moment to be A0，B0，C0；
S4: after a period of time delay, the open delta voltage is measured
And three phase line voltage
S5: calculating the complex form of the open delta voltage1+jV1And calculating three-sequence components of the three-phase line voltage and converting the three-sequence components into a complex form of U11+jV11、U21+jV21；
S6: calculating the discrimination coefficient A1，B1，C1；
S7: calculating discrimination M according to the discrimination coefficients of the previous and subsequent times, and setting a discrimination threshold value Mth；
S8: if M is greater than MthJudging that the capacitor breakdown occurs, and calculating a phase judgment quantity H according to the calculated judgment quantity M;
s9: if the element breakdown occurs in the phase a, the maximum value of H is the first element, if the element breakdown occurs in the phase B, the maximum value of H is the second element, if the element breakdown occurs in the phase C, the maximum value of H is the third element, and the maximum element is necessarily a positive number, whereby the phase sequence in which the element breakdown occurs can be determined.
Preferably, the threshold value M is determinedthIs 0.0005k to 1 k.
Preferably, the open delta voltage is set to
The voltages of the three phase lines are respectively
Is provided with
And setting the positive sequence voltage and the negative sequence voltage obtained by calculating the three-phase line voltage as
It is expressed in complex form
While
As a preference, the first and second liquid crystal compositions are,
is the vector sum of the voltages of the three-phase capacitors.
Preferably, the capacitance discrimination coefficient is
Preferably, one of the three phase lines has element breakdown, and the capacitance change rate is k and t0Solution of time to A0，B0，C0,t1Solution of time to A1，B1，C1Then, the formula for calculating the discrimination M is: m ═ A1-A0|+|B1-B0|+|C1-C0|。
Preferably, the formula for calculating the phase determination amount H is:
compared with the prior art, the invention has the beneficial effects that:
1. the capacitor monitoring method based on the open delta voltage realizes fault monitoring and fault positioning of the high-voltage capacitor device with a simple system structure, lower cost and higher precision.
2. Compared with the traditional open delta protection, the capacitor monitoring method based on the open delta voltage eliminates the interference caused by the voltage fluctuation of the system and the change of the unbalance degree of the load, so that the judgment precision of the fault can be improved, the balance fault can be effectively monitored, and the fault position information can be obtained.
3. Compared with a method for monitoring the capacitor units one by one, the capacitor monitoring method based on the open delta voltage does not have any influence on primary equipment, does not increase a sensor, and is simple in structure, high in reliability and low in cost.
Drawings
FIG. 1 is a schematic flow chart of the steps of the present invention;
FIG. 2 is a schematic of the computational flow of the present invention;
FIG. 3 is a schematic diagram of the wiring principle of the capacitor device and open delta protection of the present invention;
fig. 4 is a formula of a discrimination coefficient of the capacitor 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 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.
Example 1
The wiring principle of the capacitor device and the open delta protection of the present embodiment is shown in fig. 3, and the capacitor monitoring method based on the open delta voltage is shown in fig. 1 and fig. 2, and includes the following steps:
s1: first measuring the open delta voltage
And three phase line voltage
S2: calculating the complex form of the open delta voltage0+jV0And calculating three-sequence components of the three-phase line voltage and converting the three-sequence components into a complex form of U10+jV10、U20+jV20；
S3: calculating the discrimination coefficient at the moment to be A0，B0，C0；
S4: after a period of time delay, the open delta voltage is measured
And three phase line voltage
S5: calculating the complex form of the open delta voltage1+jΔV1To do so byAnd calculating three-sequence components of the three-phase line voltage and converting the three-sequence components into a complex form of U11+jV11、U21+jV21；
S6: calculating the discrimination coefficient A1，B1，C1；
S7: calculating discrimination M according to the discrimination coefficients of the previous and subsequent times, and setting a discrimination threshold value Mth；
S8: if M is greater than MthJudging that the capacitor breakdown occurs, and calculating a phase judgment quantity H according to the calculated judgment quantity M;
s9: if the element breakdown occurs in the phase a, the maximum value of H is the first element, if the element breakdown occurs in the phase B, the maximum value of H is the second element, if the element breakdown occurs in the phase C, the maximum value of H is the third element, and the maximum element is necessarily a positive number, whereby the phase sequence in which the element breakdown occurs can be determined.
Further, the threshold M is judgedthThe value of (a) is 0.0005k to 1k, and the threshold value of the discrimination coefficient is 0.0005 to 1 time of the change rate of the phase capacitance after the single element is broken down.
Specifically, let the open delta voltage beThe voltages of the three phase lines are respectivelyIs provided with
And setting the positive sequence voltage and the negative sequence voltage obtained by calculating the three-phase line voltage as
It is expressed in complex form
WhileConverting the system line voltage toThe voltage is converted into a positive sequence voltage and a negative sequence voltage and expressed in a complex form, the open delta voltage is expressed in a complex form, and a discrimination coefficient is calculated.
It is worth noting that, as shown in figure 4,the vector sum of the voltages of the three-phase capacitor is obtained by a capacitance discrimination coefficient of
In addition, one of the three phase lines has component breakdown, and the capacitance change rate is set as k and t0Solution of time to A0，B0，C0,t1Solution of time to A1，B1，C1Then, the formula for calculating the discrimination M is: m ═ A1-A0|+|B1-B0|+|C1-C0|。
It should be noted that the formula for calculating the phase determination amount H is:
the invention realizes high-precision test and fault location of capacitor faults by using the capacitor device and the existing signals protected by the capacitor device, introduces three-phase line voltage of a system, obtains judgment state quantity by combining with open triangular voltage, improves the judgment precision of the faults and obtains fault position information; converting the system line voltage into a positive sequence voltage and a negative sequence voltage, expressing the positive sequence voltage and the negative sequence voltage into a complex form, expressing the open triangular voltage into the complex form, and calculating a discrimination coefficient; the discrimination coefficient is only related to the impedance of the monitored capacitor bank; the judgment quantity is the difference of the judgment coefficients at different times; the threshold value of the discrimination coefficient is 0.0005 to 1 time of the phase capacity change rate after the single element is broken down; and judging the phase sequence of the component breakdown according to the position of the maximum value of the three-phase discrimination coefficient.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and the preferred embodiments of the present invention are described in the above embodiments and the description, and are not intended to limit the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (6)
1. A capacitor monitoring method based on open delta voltage is characterized in that:
the method comprises the following steps:
s1: first measuring the open delta voltage
And three phase line voltage
S2: calculating the complex form of the open delta voltage0+jΔV0And calculating three-sequence components of the three-phase line voltage and converting the three-sequence components into a complex form of U10+jV10、U20+jV20；
S3: calculating the discrimination coefficient at the moment to be A0，B0，C0；
S4: after a period of time delay, the open delta voltage is measured
And three phase line voltage
S5: calculating the complex form of the open delta voltage0+jΔV0And calculating three-sequence components of the three-phase line voltage and converting the three-sequence components into a complex form of U11+jV11、U21+jV21；
S6: calculating the discrimination coefficient A1，B1，C1；
S7: calculating discrimination M according to the discrimination coefficients of the previous and subsequent times, and setting a discrimination threshold value Mth；
S8: if M is greater than MthJudging that the capacitor breakdown occurs, and calculating a phase judgment quantity H according to the calculated judgment quantity M;
s9: if the element breakdown occurs in the phase a, the maximum value of H is the first element, if the element breakdown occurs in the phase B, the maximum value of H is the second element, if the element breakdown occurs in the phase C, the maximum value of H is the third element, and the maximum element is necessarily a positive number, whereby the phase sequence in which the element breakdown occurs can be determined.
2. The open delta voltage based capacitor monitoring method of claim 1, wherein: judgment threshold value MthIs 0.0005k to 1 k.
3. The open delta voltage based capacitor monitoring method of claim 1, wherein: let the open delta voltage beThe voltages of the three phase lines are respectively
Is provided with
And setting the positive sequence voltage and the negative sequence voltage obtained by calculating the three-phase line voltage as
It is expressed in complex form as
While
4. The open delta voltage based capacitor monitoring method of claim 1, wherein: the capacitance coefficient is
5. The open delta voltage based capacitor monitoring method of claim 1, wherein: one of the three phase capacitors has component breakdown, and the capacitance change rate is set as k and t0Solution of time to A0，B0，C0,t1Solution of time to A1，B1，C1Then, the formula for calculating the discrimination M is: m ═ A1-A0|+|B1-B0|+|C1-C0|。
6. The open delta voltage based capacitor monitoring method of claim 1, wherein: the calculation formula of the phase judgment quantity H is as follows:
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