CN112345977A - Electrical equipment and PT secondary circuit disconnection judgment method, system and device thereof - Google Patents
Electrical equipment and PT secondary circuit disconnection judgment method, system and device thereof Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
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Abstract
The invention discloses an electrical device, a PT secondary circuit disconnection judging method, a PT secondary circuit disconnection judging system and a PT secondary circuit disconnection judging device, wherein the PT secondary circuit disconnection judging method comprises the following steps: acquiring positive sequence voltage and negative sequence voltage of a PT secondary circuit; and judging whether the ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2], if so, judging that the PT secondary loop has asymmetric disconnection. The PT secondary circuit disconnection judging method can accurately judge the situation that the PT secondary circuit is subjected to asymmetric disconnection, so that related protection is locked, protection misoperation cannot be caused, and economic loss caused by misoperation of a protection device is reduced and even avoided.
Description
Technical Field
The invention relates to the technical field of electrical equipment, in particular to electrical equipment, a PT secondary circuit disconnection judging method, a PT secondary circuit disconnection judging system and a PT secondary circuit disconnection judging device.
Background
A voltage transformer (PT for short) converts a high voltage of a primary system into a required low voltage, and supplies the low voltage to a measuring instrument, a telecontrol device, a relay protection device, an automatic device, and the like.
The secondary circuit disconnection of the voltage transformer is one of fault types which are easy to occur in a production field, wherein the PT secondary circuit disconnection can be divided into a three-phase disconnection and an asymmetric disconnection (the asymmetric disconnection comprises a single-phase disconnection and a two-phase disconnection), and particularly, the probability of the occurrence of the two-phase disconnection is highest under the condition that the PT secondary circuit adopts a B-phase grounding mode. The principle of judging the secondary circuit disconnection of the voltage transformer used in the prior art mainly adopts the following three criteria:
criterion one is as follows: negative sequence voltage 13V (or other value).
Criterion two: the sum of the phasors of the three phase voltages is greater than 18V, and the difference between the modulus values of at least one line voltage is greater than 20V.
Criterion three: there is a difference in the mode values of the line voltage greater than 18V.
However, there are major problems at present: under the condition that the PT secondary circuit angular load and the star load are in mixed connection (namely the PT secondary circuit is simultaneously connected with the star load and the angular load), if two phases of the voltage transformer secondary circuit are disconnected, the disconnection of the PT secondary circuit can not be judged according to the current disconnection principle of the voltage transformer secondary circuit.
Therefore, how to avoid the problem that the PT secondary circuit can not be determined to be broken when the PT secondary circuit angular load and the star load are connected in a mixed manner is a technical problem that needs to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to provide an electrical device, a PT secondary circuit disconnection judging method, a PT secondary circuit disconnection judging system and a PT secondary circuit disconnection judging device, which can accurately judge the condition that the PT secondary circuit is subjected to asymmetric disconnection, thereby preventing the misoperation of a relay protection and safety automatic device and ensuring the necessary locking protection.
In order to achieve the above object, the present invention provides a PT secondary circuit disconnection determining method, including:
acquiring positive sequence voltage and negative sequence voltage of a PT secondary circuit;
and judging whether the ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2], if so, judging that the PT secondary loop has asymmetric disconnection.
Optionally, the step of obtaining the positive sequence voltage and the negative sequence voltage of the PT secondary circuit includes:
acquiring a PT secondary circuit three-phase voltage;
and calculating the positive sequence voltage and the negative sequence voltage according to the PT secondary circuit three-phase voltage.
Optionally, after the step of determining that the PT secondary circuit is asymmetrically broken, the method includes:
and carrying out simulation verification on the result of judging the occurrence of the asymmetric disconnection of the PT secondary circuit.
Optionally, the step of performing simulation verification on the result of determining that the PT secondary circuit is asymmetrically disconnected includes:
establishing a model in which the PT secondary circuit is connected with an angular load and a star load in parallel;
and acquiring output values of single-phase broken lines and two-phase broken lines in the corresponding state of the PT secondary circuit based on the model, wherein the output value is a first preset value when the PT secondary circuit is subjected to asymmetric broken lines, and the output value is a second preset value when the PT secondary circuit is not subjected to broken lines.
Optionally, before the step of determining whether the ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2], the method further includes:
acquiring a PT secondary loop three-phase line voltage;
and judging whether the PT secondary circuit three-phase line voltages are all smaller than the corresponding first threshold, if not, and if the voltage of a certain line of the PT secondary circuit three-phase line voltages or the voltage of a certain line of the PT secondary circuit three-phase line voltages is smaller than the corresponding first threshold, executing the step of judging whether the ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2 ].
The present invention also provides a PT secondary circuit disconnection judging system, including:
the acquisition module is used for acquiring positive sequence voltage and negative sequence voltage of the PT secondary circuit;
and the judging module is used for judging whether the ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2], and if so, judging that the PT secondary circuit is subjected to asymmetric disconnection.
Optionally, the obtaining module includes:
the acquisition unit is used for acquiring three-phase voltage of the PT secondary circuit;
and the calculating unit is used for calculating the positive sequence voltage and the negative sequence voltage according to the PT secondary circuit three-phase voltage.
The present invention also provides a PT secondary circuit disconnection judging device, including:
a memory for storing a computer program;
and the processor is used for realizing the steps of the PT secondary circuit disconnection judging method when the computer program is executed.
The invention also provides electrical equipment comprising the PT secondary circuit disconnection judging device.
Compared with the prior art, the PT asymmetric disconnection criterion configured for the relay protection device at present has certain defects, so that PT disconnection and related protection locking cannot be correctly judged under certain conditions, and certain potential safety hazards exist. To solve the problem, the method for determining PT secondary circuit disconnection provided in the embodiment of the present invention includes: acquiring positive sequence voltage and negative sequence voltage of the PT secondary circuit, judging whether the ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2], and if so, judging that the PT secondary circuit has asymmetric disconnection. The PT disconnection criterion based on the sequence voltage ratio principle is provided by analyzing the characteristics of positive sequence voltage and negative sequence voltage after disconnection under the condition that the PT secondary circuit is connected with different types of loads in parallel or only connected with a star-type load device. It can be seen that, for the type of PT secondary circuit disconnection, i.e. three-phase non-disconnection, single-phase disconnection, two-phase disconnection or three-phase disconnection, the ratio of the positive sequence voltage and the negative sequence voltage is different, and by judging that the ratio of the positive sequence voltage and the negative sequence voltage is within [1, 2], it can be determined that the PT secondary circuit has asymmetric disconnection, that is, no matter what the type of equipment the PT secondary circuit is connected in parallel, when the asymmetric disconnection occurs, the ratio of the positive sequence voltage and the negative sequence voltage has the above obvious characteristics, so that the condition that the PT secondary circuit has asymmetric disconnection can be accurately determined, and related protection is locked, therefore, protection malfunction cannot be caused, and economic loss caused by protection device malfunction can be reduced or even avoided.
The invention also provides a PT secondary circuit disconnection judging system, a PT secondary circuit disconnection judging device and electrical equipment, and the beneficial effects are as above, and the details are not repeated herein.
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 described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a flowchart of a PT secondary circuit disconnection determining method according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a symmetrical three-phase sinusoidal power supply with a PT secondary loop Y connection according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of the PT secondary circuit connection provided by the embodiment of the present invention;
FIG. 4 is an electrical model built based on PSCAD according to the embodiment of the present invention;
fig. 5 is a block diagram of a PT secondary circuit disconnection determining system according to an embodiment of the present invention.
Wherein:
101-an acquisition module, 102-a judgment module,
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 core of the invention is to provide an electrical device, a PT secondary circuit disconnection judging method, a PT secondary circuit disconnection judging system and a PT secondary circuit disconnection judging device, which can accurately judge the condition that the PT secondary circuit is subjected to asymmetric disconnection, thereby preventing the misoperation of a relay protection and safety automatic device and ensuring the necessary locking protection.
In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Referring to fig. 1 to 5, fig. 1 is a flowchart of a PT secondary circuit disconnection determining method according to an embodiment of the present invention; FIG. 2 is a schematic diagram of a symmetrical three-phase sinusoidal power supply with a PT secondary loop Y connection according to an embodiment of the present invention; FIG. 3 is a schematic diagram of the PT secondary circuit connection provided by the embodiment of the present invention; FIG. 4 is an electrical model built based on PSCAD according to the embodiment of the present invention; fig. 5 is a block diagram of a PT secondary circuit disconnection determining system according to an embodiment of the present invention.
The PT secondary circuit disconnection judging method provided by the embodiment of the invention comprises the following steps:
s1, acquiring positive sequence voltage and negative sequence voltage of the PT secondary loop;
and S2, judging whether the ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2], and if so, judging that the PT secondary circuit has asymmetric disconnection.
For step S1, the positive sequence voltage and the negative sequence voltage of the PT secondary circuit when different types of loads are connected in parallel and three-phase disconnection, single-phase disconnection, two-phase disconnection or three-phase disconnection occurs may be obtained.
Aiming at the step S2, by analyzing the characteristics of the positive sequence voltage and the negative sequence voltage of the PT secondary circuit after disconnection under different conditions, and based on the characteristics, a PT disconnection criterion based on the sequence voltage ratio principle is provided, namely when the ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2], the PT secondary circuit can be judged to generate asymmetric disconnection.
It can be seen that, for different line breaking types of the PT secondary circuit connected in parallel with a certain type of load, namely, the conditions of three-phase line break, single-phase line break, two-phase line break or three-phase line break, the ratio of the positive sequence voltage and the negative sequence voltage is different, and the occurrence of the asymmetric line break of the PT secondary circuit can be determined by judging that the ratio of the positive sequence voltage and the negative sequence voltage is within [1, 2 ].
Obviously, no matter what the type of the equipment connected with the PT secondary circuit in parallel, when the asymmetric disconnection occurs, the ratio of the positive sequence voltage to the negative sequence voltage has the obvious characteristics, so that the condition that the PT secondary circuit has the asymmetric disconnection can be accurately judged, and related protection is locked, therefore, the protection misoperation cannot be caused, and the economic loss caused by the misoperation of the protection device can be favorably reduced or even avoided.
Specifically, the step of obtaining the positive sequence voltage and the negative sequence voltage of the PT secondary circuit includes: obtaining PT secondary loop three-phase voltage UAN，UBNAnd UCNOr line voltage UAB，UBC，UCAAnd according to PT secondary circuit three-phase voltage UAN，UBNAnd UCNOr line voltage UAB，UBC，UCAThe positive and negative sequence voltages are calculated.
Y-connected symmetrical three-phase sinusoidal power supply As shown in figure 2 of the specification, the ends of A, B, C three-phase windings are connected together, and the point N in the figure is called neutral point (or neutral point)Midpoint), the head ends A, B, C each draw a line to carry electrical energy outward, these A, B, C three lines are called end lines (commonly called live lines), and a line is drawn from the neutral point N, called neutral or neutral for short. End-to-neutral voltage (U)AN，UBN，UCN) Referred to as phase voltages. Voltage (U) between two end linesAB，UBC，UCA) Referred to as line voltage.
In addition, before the step of determining whether the ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2], the method further comprises:
calculating PT secondary loop three-phase line voltage U according to PT secondary loop three-phase voltageAB，UBCAnd UCA；
Judging PT secondary loop three-phase line voltage UAB，UBCAnd UCAOr three-phase voltage UAN，UBN，UCNWhether all are less than the corresponding first threshold value Um1、Um2And Um3If not, and when a certain line voltage or certain two line voltages of the PT secondary circuit three-phase line voltages or a certain phase voltage or certain two phase voltages of the PT secondary circuit three-phase voltage are smaller than the corresponding first threshold value, judging whether the ratio of the positive sequence voltage to the negative sequence voltage is [1, 2]]The steps of (1).
In other words, in order to determine whether the PT secondary circuit is asymmetrically broken, i.e., single-phase or two-phase broken, it is determined whether the ratio of the positive sequence voltage to the negative sequence voltage is [1, 2]]The steps within are preceded by limiting the type of disconnection to single-phase and two-phase disconnections, in particular when the three-phase line voltage or the three-phase voltages are both less than the corresponding first threshold, as exemplified by a three-phase line voltage, i.e. UAB＜Um1、UBC＜Um2、UCA＜Um3When the conditions are met, the type of the broken line is PT secondary circuit three-phase broken line, or the primary system is in voltage loss, the step of obtaining PT secondary circuit three-phase voltage is returned, or the criterion of three-phase broken line is entered, and the criterion of three-phase broken line refers to the content of the prior art; when U is turnedAB＜Um1、UBC＜Um2、UCA＜Um3All the above-mentioned two components are not true, at the moment, the disconnection does not occur; when U is turnedAB＜Um1、UBC＜Um2、UCA＜Um3If one or two of the three conditions are not satisfied, entering the asymmetric disconnection criterion.
It should be noted that the first threshold value can be set to 0.25-0.3U of the no-voltage fixed value of the working voltage according to the rule of the law such as DLT1502-2016 factory electrical relay protection setting calculation guide rulen(UnIs the bus voltage secondary rated voltage).
And (S2) recording the ratio of the positive sequence voltage to the negative sequence voltage as alpha, judging that the PT secondary circuit is subjected to asymmetric disconnection if the ratio of the positive sequence voltage to the negative sequence voltage is more than or equal to 1 and less than or equal to 2 according to the calculation result, and sending a locking instruction for a self module or other relay protection and safety automatic devices.
If alpha is not less than 1 and not more than 2, returning to the step of obtaining the three-phase voltage of the PT secondary circuit.
Description of the values of α:
in the first case: and (3) single-phase disconnection, according to the calculation result, when the angular load impedance is far greater than the star load impedance, the alpha value is infinitely close to 2, and when the angular load impedance is far less than the star load impedance, the alpha value is infinitely close to 1.
In the second case: and two phases are disconnected, and according to the calculation result, when the angular load impedance is far greater than the star load impedance, the alpha value is 1, and when the angular load impedance is far less than the star load impedance, the alpha value is 1.
Therefore, the value range of the PT secondary circuit asymmetric disconnection is judged to be more than or equal to 1 and less than or equal to 2.
The value of the PT secondary circuit alpha in the mixed connection of different types of devices is described in detail below.
According to the regulations of relay protection and safety automata, the rated value of the alternating voltage of the relay protection and safety automata is 100V or 100/√ 3V, so that the protection manufacturer selects 100V for the rated value of the alternating voltage of the device, i.e., the line voltage of the device leading into the PT secondary circuit, and 100/√ 3V, i.e., the phase voltage of the device leading into the PT secondary circuit. At present, PT secondary circuit load wiring in a production field has three conditions, wherein devices of different types of a primary circuit and a PT secondary circuit are in mixed connection; secondly, the PT secondary circuit is only connected with a star load; and thirdly, the PT secondary circuit is only connected with an angle type load (very rare). A typical PT secondary circuit wiring diagram is shown in figure 3 of the specification.
For ease of analysis, the following assumptions were made:
(1) the three-phase impedances of the internal voltage converters of the protection and safety automaton are the same.
(2) Z in equivalent model of angle type loadA△B△＝ZB△C△＝ZC△A△＝Z△(Z△＝0～∞)。
(3) In the equivalent model of the star-type load,
(4) the three-phase voltages of the PT secondary winding have equal amplitude and same frequency, and are sequentially different by 120 degrees from each other, and the potential V isN＝VN’Secondary rated voltage amplitude UN＝57.7V。
(I) PT secondary circuit different types of devices mixed connection
1. Star-shaped load PT single-phase broken line
Suppose PT secondary loop B is disconnected. Non-broken line phase voltage acquired by star load
According to the node voltage method, the broken line phase voltage collected by the protection device can be calculated:
the positive sequence voltage is:
the negative sequence voltage is:
then:
the method is simplified to obtain:
let ZY＝nZ△Then:
the value range of α is:
namely, the value range of alpha is [1, 2 ].
2. Star-shaped load two-phase broken line
Assume that two phases of PT secondary loop A, B are open. The non-broken line phase voltage is U'CN'。
The A phase voltage collected by the protection device passes through N630-N' -A△–C△the-C-C630 forms a new loop.
The B phase voltage collected by the protection device passes through N630-N' -B△-C△-C-C630 forms a loop.
Calculating according to the circuit knowledge:
the positive sequence voltage is:
order to
Then
The negative sequence voltage is:
then:
3. angle type load PT single-phase broken line
Suppose PT secondary loop B is disconnected.
Non-line-break phase voltage:
phase voltage amplitude of UN。
For the voltage collected for the angle load:
from VA△＝VA,VC△＝VC,VB△＝VBThe combination of formula (1) can give
Order to
According to the trigonometric function knowledge, the following can be obtained:
UA△C△ 2＝3UN 2
calculating the positive sequence voltage of the positive sequence voltage:
let Z△＝mZYThen
Thus, it is possible to provide
Has a value range of [0, 0.5 ]]
Finally, simplifying to obtain:
the negative sequence voltage is:
finally, simplifying to obtain:
the sequence voltage ratio is:
the value range of α is:
i.e. the value range of alpha is [0, 2 ].
4. Angle type load PT two-phase broken line
Assuming that PT secondary side A, B is disconnected, the line voltage collected by the angular load is:
the following formula (2) and formula (3) can be obtained:
UA△B△＝0V
the negative sequence voltage is:
the positive sequence voltage can be calculated as follows:
the calculation results show that:
(II) PT secondary circuit only connected with star type load
1. Star-shaped load two-phase broken line
Assume that two phases of PT secondary loop A, B are open. The A, B phase voltage acquired by the device is 0V, and the non-broken line phase voltage is UCN’Then the negative sequence voltage is:
the positive sequence voltage is:
then it is
2. Star-shaped load single-phase broken line
Suppose PT secondary loop B is disconnected. The phase voltage of B phase collected by the device is 0V, and the phase voltage of non-broken line is
The negative sequence voltage is then:
the positive sequence voltage is:
then
(III) PT secondary circuit corner-only type load
Suppose two phases of the PT secondary loop are disconnected. The line voltage collected by the device is 0V. The characteristics are the same as three-phase broken lines.
Suppose that the PT secondary circuit has a single-phase disconnection such as a B-phase disconnection. From circuit knowledge, one can obtain:
calculated and simplified to obtain:
in summary, no matter what the type of devices connected in parallel to the PT secondary circuit, when an asymmetric disconnection occurs, the ratio of the positive sequence voltage to the negative sequence voltage has obvious characteristics, and according to the characteristics of the ratio of the sequence voltages, a new PT disconnection logic is designed as follows:
the PT secondary circuit asymmetric disconnection criterion comprises the following steps: the protection device respectively calculates the positive sequence voltage amplitude and the negative sequence voltage amplitude according to the collected voltage, calculates the ratio alpha of the positive sequence voltage to the negative sequence voltage, and judges PT asymmetrical disconnection when the alpha is more than or equal to 1 and less than or equal to 2.
II, PT secondary circuit three-phase disconnection: (conventional design) when the voltage is less than (0.25-0.3) U of rated valueNWhen the current value is larger than 0.04Ie of the rated value, the PT three-phase symmetrical disconnection is judged.
When only an angular load exists in the PT secondary circuit, two phases are disconnected, and the voltage collected by the device is 0V, so that it is impossible to determine the current amount by using only a single voltage amount, and it is necessary to determine the current amount. Therefore, the condition meets the criterion of the second criterion, the three-phase disconnection is judged, and the related protection is locked, so that the protection misoperation cannot be caused.
In order to verify the effectiveness of the PT asymmetric disconnection method provided by the invention (the PT three-phase disconnection criterion is not verified), the method comprises the following steps of: and carrying out simulation verification on the result of judging the occurrence of the asymmetric disconnection of the PT secondary circuit. Preferably, the method specifically comprises the following steps:
establishing a model in which a PT secondary circuit is connected with an angular load and a star load in parallel;
obtaining output values of single-phase broken lines and two-phase broken lines under the corresponding state of the PT secondary circuit based on the model; when the PT secondary circuit is subjected to asymmetric disconnection, the output value is a first preset value, and when the PT secondary circuit is not subjected to disconnection, the output value is a second preset value. In practical applications, the first preset value may be set to "1", and the second preset value may be set to "0", so that 1 is output when it is determined that the PT is asymmetrically disconnected, and 0 is output when it is determined that the PT is not disconnected. Of course, the setting of the first preset value and the second preset value is not particularly limited herein.
Of course, a model as shown in fig. 4 may be established based on PSCAD/EMTDC, and single-phase disconnection and two-phase disconnection may be simulated in the case of a PT secondary circuit hybrid connection of different types of devices, a single star load (with an angular load portion removed), and a single angular load (with a star load portion removed), respectively. The PT secondary circuit asymmetric disconnection criterion is set according to that alpha is more than or equal to 1 and less than or equal to 2, 1 is output when the PT is judged to have asymmetric disconnection, and 0 is output when the PT is judged not to have the asymmetric disconnection.
The analysis and PSCAD/EMTDC simulation show that the PT disconnection criterion adopting the sequence voltage ratio has a wide application range, can reliably judge whether the PT is disconnected no matter how the voltage loop connection mode of the equipment connected with the PT secondary circuit equipment is, can also be used as the criterion for judging the PT primary side disconnection, and has a wide application range.
The invention provides a PT secondary circuit disconnection judging system, as shown in the attached figure 5 of the specification, comprising:
the acquisition module 101 is used for acquiring positive sequence voltage and negative sequence voltage of the PT secondary loop;
the determining module 102 is configured to determine whether a ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2], and if so, determine that the PT secondary circuit is asymmetrically disconnected.
Further, the obtaining module 101 includes:
the acquisition unit is used for acquiring three-phase voltage of the PT secondary circuit;
and the calculating unit is used for calculating the positive sequence voltage and the negative sequence voltage according to the PT secondary circuit three-phase voltage.
The invention provides a PT secondary circuit disconnection judging device, which comprises:
a memory for storing a computer program;
and the processor is used for realizing the steps of the PT secondary circuit disconnection judging method when the computer program is executed.
Specifically, the memory includes a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and computer-readable instructions, and the internal memory provides an environment for the operating system and the computer-readable instructions in the non-volatile storage medium to run. The processor, which in some embodiments may be a Central Processing Unit (CPU), controller, microcontroller, microprocessor or other data Processing chip, provides computing and control capabilities for the PT secondary loop disconnection determining device.
In addition to the above-described embodiments, as a preferred embodiment, the PT secondary circuit disconnection determining apparatus further includes:
and the input interface is connected with the processor and used for acquiring computer programs, parameters and instructions imported from the outside and storing the computer programs, the parameters and the instructions into the memory under the control of the processor. The input interface may be coupled to an input device for receiving parameters or instructions manually input by a user. The input device may be a touch layer covered on a display screen, or a button, a track ball or a touch pad arranged on a terminal shell, or a keyboard, a touch pad or a mouse, etc.
And the display unit is connected with the processor and is used for displaying the data processed by the processor and displaying the visual user interface. The display unit may be an LED display, a liquid crystal display, a touch-controlled liquid crystal display, an OLED (Organic Light-Emitting Diode) touch device, and the like.
And the network port is connected with the processor and is used for carrying out communication connection with each external terminal device. The communication technology adopted by the communication connection can be a wired communication technology or a wireless communication technology, such as a mobile high definition link (MHL) technology, a Universal Serial Bus (USB), a High Definition Multimedia Interface (HDMI), a wireless fidelity (WiFi), a bluetooth communication technology, a low power consumption bluetooth communication technology, an ieee802.11 s-based communication technology, and the like.
It will be appreciated by those skilled in the art that the PT secondary circuit disconnection judging means may include fewer or more components than those described above, or some components may be combined, or a different arrangement of components.
The present application also provides a computer-readable storage medium, which may include: various media capable of storing program codes, such as a usb disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk. The storage medium stores thereon a computer program, and the computer program, when executed by a processor, implements the steps of the PT secondary circuit disconnection determination method provided in the above-described embodiment.
The invention provides an electrical device, which comprises the PT secondary circuit disconnection judging device described in the specific embodiment; other parts of the electrical apparatus can be referred to the prior art and are not expanded herein.
It is noted that, in this specification, relational terms such as first and second, and the like are used solely to distinguish one entity from another entity without necessarily requiring or implying any actual such relationship or order between such entities.
The PT secondary circuit disconnection judging method, PT secondary circuit disconnection judging system, PT secondary circuit disconnection judging device, and electrical apparatus according to the present invention have been described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are provided only to help understand the concepts of the present invention and the core concepts thereof. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (9)
1. A PT secondary circuit disconnection judging method is characterized by comprising the following steps:
acquiring positive sequence voltage and negative sequence voltage of a PT secondary circuit;
and judging whether the ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2], if so, judging that the PT secondary loop has asymmetric disconnection.
2. The PT secondary circuit disconnection judging method of claim 1, wherein the step of obtaining the positive sequence voltage and the negative sequence voltage of the PT secondary circuit comprises:
acquiring a PT secondary circuit three-phase voltage;
and calculating the positive sequence voltage and the negative sequence voltage according to the PT secondary circuit three-phase voltage.
3. The PT secondary circuit disconnection judging method of claim 1, wherein the step of judging that the PT secondary circuit is asymmetrically disconnected, after the step of judging that the PT secondary circuit is asymmetrically disconnected, comprises:
and carrying out simulation verification on the result of judging the occurrence of the asymmetric disconnection of the PT secondary circuit.
4. The PT secondary circuit disconnection judging method of claim 3, wherein the step of performing simulation verification on the result of judging that the PT secondary circuit is asymmetrically disconnected comprises:
establishing a model in which the PT secondary circuit is connected with an angular load and a star load in parallel;
and acquiring output values of single-phase broken lines and two-phase broken lines in the corresponding state of the PT secondary circuit based on the model, wherein the output value is a first preset value when the PT secondary circuit is subjected to asymmetric broken lines, and the output value is a second preset value when the PT secondary circuit is not subjected to broken lines.
5. The PT secondary circuit disconnection judging method of any one of claims 1 to 4, wherein before the step of judging whether the ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2], further comprising:
acquiring a PT secondary loop three-phase line voltage;
and judging whether the PT secondary circuit three-phase line voltages are all smaller than the corresponding first threshold, if not, and if the voltage of a certain line of the PT secondary circuit three-phase line voltages or the voltage of a certain line of the PT secondary circuit three-phase line voltages is smaller than the corresponding first threshold, executing the step of judging whether the ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2 ].
6. A PT secondary circuit disconnection judging system is characterized by comprising:
the acquisition module (101) is used for acquiring the positive sequence voltage and the negative sequence voltage of the PT secondary loop;
and the judging module (102) is used for judging whether the ratio of the positive sequence voltage to the negative sequence voltage is within [1, 2], and if so, judging that the PT secondary loop has asymmetric disconnection.
7. The PT secondary loop disconnection determining system of claim 6, wherein the obtaining module (101) comprises:
the acquisition unit is used for acquiring three-phase voltage of the PT secondary circuit;
and the calculating unit is used for calculating the positive sequence voltage and the negative sequence voltage according to the PT secondary circuit three-phase voltage.
8. A PT secondary circuit disconnection judging device is characterized by comprising:
a memory for storing a computer program;
a processor for implementing the steps of the PT secondary circuit disconnection judging method according to any one of claims 1 to 5 when executing the computer program.
9. An electric device characterized by comprising the PT secondary circuit disconnection judging device according to claim 8.
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