CN115932385B - Residual current monitoring method and system and single-phase intelligent electric energy meter - Google Patents
Residual current monitoring method and system and single-phase intelligent electric energy meter Download PDFInfo
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Abstract
The invention provides a residual current monitoring method, a residual current monitoring system and a single-phase intelligent electric energy meter, which are used for simultaneously collecting the same current signal source under the same environment, and respectively obtaining phase line current and zero line current of the electric energy meter through a first current sampling element and a second current sampling element; acquiring a fixed reference value based on a mutual deviation value of the phase line current and the zero line current; acquiring two paths of measured current relation characteristic values based on a comparison result of the phase line current and the zero line current; acquiring a real-time phase line current and a real-time zero line current; according to the fixed reference value, the two-path measured current relation characteristic value, the real-time phase line current and the real-time zero line current; and obtaining residual current. And the phase line current and the zero line current are adopted for simultaneous homologous calibration, so that the function of accurately monitoring the residual current of the electric energy meter is realized.
Description
Technical Field
The invention relates to the field of electrical instruments and meters, in particular to a residual current monitoring method and system and a single-phase intelligent electric energy meter.
Background
Residual current refers to the vector sum of the currents of the phases (including the neutral) in the low voltage distribution line and the current that is not zero. When accident happens to the electricity utilization side, the current flows from the electrified body to the ground through the human body, so that the current I in the main circuit incoming and outgoing line Phase (C) And I In (a) The instantaneous vector synthesized effective value of the current is called residual current, commonly called leakage. The residual current protection device is arranged at the inlet end of the electric circuit and forms a grading protection mode with the tail end protection, so that the protection device can prevent personal electric shock accidents and prevent electric fire accidents caused by single-phase grounding. However, the common residual current protection device cannot dynamically monitor and check and prevent potential safety hazards of electric leakage, and fire disasters caused by grounding arcs are avoided.
The typical technical scheme for realizing residual current function monitoring of the current single-phase intelligent electric energy meter comprises two types, wherein one type is that a residual current transformer is used for replacing a zero line current sampling current transformer on the basis of the technical scheme of the current single-phase intelligent electric energy meter, and the residual current is monitored by collecting vector sum of phase line current and zero line current or symmetrical circuit design of two-way current measurement of the phase line current and the zero line current and applying formula I leakage = I fire-I zero calculation. The technical principle of the scheme can be realized, and the difficulty of converting the product into the product is too great to be widely popularized and applied.
As in example 1, chinese patent publication No. CN107328969B discloses an electric energy meter capable of measuring residual current. The technical scheme has several risks, firstly, the cost risk of the product materials is increased; secondly, as the assembly process of the product becomes complex, the production efficiency is reduced to a certain extent, and the time of exchange is prolonged and the manufacturing cost risk is increased; thirdly, the zero line and the phase line need to pass through the electric principle of the residual current transformer at the same time (the current directions are opposite to each other) and the complex assembly process, so that the electromagnetic interference environment in the electric energy meter becomes more complex, the difficulty is increased for the electromagnetic interference resistance design of the electric energy meter, and the electric energy meter brings uncontrollable risks of different degrees in the aspects of metering accuracy, residual current measurement accuracy, electromagnetic compatibility and the like; fourth, when the phase line of the entering household is not connected to the special working condition of the outlet end (No. 2 terminal) of the phase line of the electric energy meter, misjudgment of zero line current and residual current occurs to the electric energy meter, so that the function of the electric energy meter does not meet the technical requirements of a power grid.
Another typical technical scheme is as in example 2, the publication number of the Chinese patent document is CN114487529A, and the instantaneous value with a time scale/phase angle is a single-phase electric energy meter for preventing electricity stealing and leakage; example 3, chinese patent publication No. CN217238207U, a single-phase electric energy meter using double-manganin resistor sampling.
The technical principle of the schemes described in the above examples 2 and 3 is that by designing two symmetrical current detection circuits of the phase line current and the zero line current, an arithmetic difference obtained by the formula I drain=i fire-I zero is regarded as the residual current value generated by the power line on the user side. The technical solutions have several drawbacks, and first, the two current detection circuits in the two solutions of example 2 and example 3 are symmetrical in theory, and in fact, there are inherent attribute differences in the performance parameters of the two current detection elements, and there are differences in the electromagnetic environments of the installation positions of the two current detection elements in the solutions and the positions of the relevant additional circuits. The difference cannot be detected, and accumulation of the difference can cause that the calculation leakage current formula (I leakage=i fire-I zero) in the scheme cannot truly and accurately detect the actual working condition (leakage or electricity theft) in the power line at the user side; second, both of the two solutions employ a design pattern that increases the number of components, which increases the risk of product cost improvement, while increasing the risk of controlling product reliability.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention is based on the prior intelligent electric energy meter, does not need to change the hardware principle of the prior intelligent electric energy meter technical scheme, does not use a residual current transformer (a phase line and a zero line penetrate into the residual current transformer at different time), and realizes the function of accurately monitoring the residual current of the electric energy meter by improving the design of product embedded system software and adopting special phase line current and zero line current and homologous calibration special process technology.
The invention provides a residual current monitoring method, which comprises the following steps:
step S1: the method comprises the steps of simultaneously collecting the same current signal source under the same environment, and respectively obtaining phase line current and zero line current of the electric energy meter through a first current sampling element and a second current sampling element;
step S2: acquiring a fixed reference value based on a mutual deviation value of the phase line current and the zero line current; acquiring two paths of measured current relation characteristic values based on a comparison result of the phase line current and the zero line current;
step S3: respectively acquiring real-time phase line current and real-time zero line current through the first current sampling element and the second current sampling element;
step S4: according to the fixed reference value, the two-path measured current relation characteristic value, the real-time phase line current and the real-time zero line current; and obtaining residual current.
Further, the first current sampling element is different from the second current sampling element;
the first current sampling element is a phase line current sampling manganese-copper resistor; and/or the second current sampling element is a zero line current sampling current transformer (anti-direct current component type).
Further, the step S1 of simultaneously collecting the same current signal source under the same environment includes: the electric energy meter can acquire the same current signal source when the phase line current and the zero line current are calibrated in a factory mode.
Further, the electric energy meter can acquire the same current signal source when the factory mode calibrates the phase line current and the zero line current, and the electric energy meter comprises: when the phase line current and the zero line current are calibrated by the electric energy meter, the zero line voltage line is electrically disconnected with the primary input side of the zero line current sampling current transformer, and the phase line current sampling manganese-copper resistor and the zero line current sampling current transformer of the electric energy meter collect the same current signal source at the same time.
Further, after the calibration is finished, the electric connection between the zero line voltage line and the primary input side of the zero line current sampling current transformer is restored.
Further, the obtaining a fixed reference value based on the mutual deviation value of the phase line current and the neutral line current in the step S2 includes: dividing the current measuring range of the electric energy meter into n sections of current intervals, wherein each section of current interval parameter comprises four parameter information including voltage, current, power factor and harmonic component, and the mutual deviation value of the effective values of the phase line current and the zero line current obtained by sampling the phase line current sampling manganese copper resistor and the zero line current sampling current transformer in the n sections of current intervals is used as a fixed reference value I of the n sections of current intervals OEn The fixed reference value I OEn =||I Ln |-|I Nn I, wherein I Ln For phase line current in the nth current interval, I Nn Is zero line current in the nth segment current interval.
Further, the step S2 of obtaining two-way measured current relation characteristic values based on the comparison result of the phase line current and the zero line current includes: the current measuring range of the electric energy meter is divided into n sections of current intervals, the phase line current obtained by sampling the phase line current sampling manganese-copper resistor and the zero line current sampling current transformer in the n sections of current intervals is compared with the effective value of the zero line current, if the absolute value of the phase line current ILn in the n sections of current intervals is larger than the absolute value of the zero line current INn in the n sections of current intervals, the current relation characteristic value IOECn is 1, and if the absolute value of the phase line current ILn in the n sections of current intervals is smaller than the absolute value of the zero line current INn in the n sections of current intervals, the two paths of measured current relation characteristic values IOECn are 0.
Further, the electric energy meter monitors the real-time phase line current I according to the working condition of running in the nth section current interval Ln * And real-time zero line current I Nn * And according to the two-way measured current relation characteristic value I of the current interval of the corresponding section OECn And a fixed reference value I OEn Calculating residual current I △ If I OECn =1, then I △ =||I Ln *|-|I Nn *||-I OEn If I OECn =0, then I △ =||I Ln *|-|I Nn *||+I OEn 。
The invention also provides a residual current monitoring system, which comprises a processor and a memory, wherein the memory stores instructions executable by the processor, and the instructions are executed by the processor so that the processor can execute the residual current monitoring method.
The invention also provides a single-phase intelligent electric energy meter, which comprises an electronic board component, a first current sampling element, a second current sampling element, a wiring terminal row and an electric energy meter shell, wherein the electronic board component, the first current sampling element, the second current sampling element and the wiring terminal row are all arranged in the electric energy meter shell, and the single-phase intelligent electric energy meter is characterized in that: the electronic board component comprises a main control module and a storage module, wherein the storage module stores the fixed reference value and the two paths of measured current relation characteristic values, and the main control module is used for executing a computer (microprocessor) program for realizing the residual current monitoring method.
The beneficial effects are that:
1. the invention collects the same current signal source under the same environment, and respectively obtains the phase line current and the zero line current of the electric energy meter through the first current sampling element and the second current sampling element, thereby determining a fixed reference value and a two-path measurement current relation characteristic value. The phase line current and the zero line current are simultaneously subjected to homologous calibration by a special process technology, so that different property loads (inductive or capacitive) in a line and interference sources caused under different electromagnetic environments can be overcome, the same current signal source can be acquired to become a key link for accurately obtaining two important parameters of a fixed reference value and a two-path measurement current relation characteristic value, and the function of accurately monitoring the residual current is realized.
2. The invention adopts the phase line current sampling manganese copper resistor and the zero line current sampling current transformer to respectively detect the phase line current and the zero line current, and does not need to add or change a residual current transformer, the phase line and the zero line do not need to penetrate into the residual current transformer at the same time, and the hardware principle of the technical scheme of the intelligent electric energy meter is not required to be changed.
3. According to the invention, the current subsection interval calibration is carried out according to the current measurement range of the electric energy meter, and in the n-section current interval, due to different property loads (inductive or capacitive) in the circuit and different interference sources under different electromagnetic environments, the accuracy and consistency of monitoring the residual current of the electric energy meter under different working conditions can be ensured by adopting the mode.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart and a method for calculating residual current according to an embodiment of the present invention;
FIG. 2 is a flowchart of obtaining phase line current, zero line current calibration and fixed reference values and two paths of measured current relation characteristic values according to an embodiment of the present invention;
fig. 3 is a diagram of an intelligent electric energy meter according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which are derived by a person skilled in the art based on the embodiments of the invention, fall within the scope of protection of the invention.
Example 1
Referring to fig. 1-2, a residual current monitoring method is disclosed, wherein a first current sampling element and a second current sampling element are used in an electric energy meter, the first current sampling element is a phase line current sampling manganese copper resistor and/or the second current sampling element is a zero line current sampling current transformer, including but not limited to a current transformer (anti-direct current component type), and when the two current sampling elements are adopted to sample the same current signal source simultaneously in the same environment, an inherent mutual deviation value exists between two paths of zero line current and phase line current as a fixed reference value due to loads (inductance or capacitance) with different properties in a circuit and interference sources caused in different electromagnetic environments.
Preferably, the current measuring range of the electric energy meter is divided into n sections of current intervals, the n sections of current intervals comprise four information of voltage, current, power factor and harmonic component in a line, loads with different properties (inductive or capacitive) and interference sources caused under different electromagnetic environments, the phase line current samples the difference between two current effective values obtained by sampling the manganese copper resistor and the zero line current sampling current transformer in the n sections of current intervals, the difference between the two current effective values obtained by sampling in the n sections of current intervals is used as a mutual deviation value of two current measuring values when the electric energy meter works in the n sections of current intervals, and is used as a fixed reference value I for calculating the residual current of the electric energy meter working in the n sections of current intervals OEn =||I Ln |-|I Nn I, wherein I Ln For phase line current in the nth current interval, I Nn Is zero line current in the nth segment current interval.
Preferably, the phase line current and the zero line current of the electric energy meter are compared after being calibrated in the nth section current interval to obtain two paths of measured current relation characteristic values I OECn I.e. |I Ln |>|I Nn Time I OECn Assign 1, or I Ln |<|I Nn I at I OECn Assigning 0, the measurement relation characteristic value I OECn And the fixed reference value I OEn The two parameters are permanently stored in the memory chip and serve as important parameters for calculating the residual current in the operation process of the electric energy meter.
Preferably, the electric energy meter can collect the same current signal source simultaneously when the factory mode calibrates the phase line current and the zero line current to accurately obtain the relation characteristic value I of the two paths of measured currents OECn And the fixed reference value I OEn Key links of two important parameters.
Preferably, when the phase line current and the zero line current are calibrated by the electric energy meter, the zero line voltage line and the primary input side of the zero line current sampling current transformer are disconnected electrically, the zero line voltage line and the zero line current binding post of the electric energy meter calibrating device are separated, and normal operation of the same current signal source is ensured to be acquired by the electric energy meter phase line current sampling manganese-copper resistor and the zero line current sampling current transformer simultaneously. And after the calibration is finished, the electric connection between the zero line and the primary input side of the zero line current sampling current transformer is restored.
Preferably, the electric energy meter monitors the real-time phase line current I according to the working condition of the electric energy meter running in the nth section current interval Ln * And real-time zero line current I Nn * And according to the two-way measured current relation characteristic value I of the corresponding current segment OECn And a fixed reference value I OEn Calculating residual current I △ If I OECn =1, then I △ =||I Ln *|-|I Nn *||-I OEn If I OECn =0, then I △ =||I Ln *|-|I Nn *||+I OEn 。
Example two
Referring to fig. 1-3, a single-phase intelligent electric energy meter implements the residual current monitoring method described in the first embodiment.
The single-phase intelligent electric energy meter comprises an electronic board component 11, a phase line current sampling manganese-copper resistor, a relay 13, a zero line current sampling current transformer 12, a wiring terminal block 14, an electric energy meter shell and the like. The electronic board component 11, the phase line current sampling manganese copper resistor, the relay 13, the zero line current sampling current transformer 12 and the wiring terminal block 14 of the electric energy meter are all arranged in the electric energy meter shell.
The electronic board assembly 11 includes a clock module 111, a security authentication module 112, an infrared communication 113, a metering module 114, a power module 115, a battery 116, a power carrier/wireless communication module 117, a 485 communication module 118, a key module 119, a storage module 1110, a main control Module (MCU) 1111, and a display module 1112. The terminal block 14 includes a phase wire in 141, a phase wire out 142, a neutral wire in 143, and a neutral wire out 144, and a bridging device 145 (which may be disposed on the terminal block 14 or on the electronic board component 11 according to the design principle of the optimal electric energy meter solution). The single-phase intelligent electric energy meter comprises an electric energy metering function, an electric energy freezing function, a voltage and current measuring function, an intelligent fee control function, a real-time clock function, a communication function, an event alarming function and a precise residual current monitoring function, which are basic in the electric energy meter, so that the accuracy and consistency of detecting residual current of the electric energy meter under different working conditions are ensured, and the residual current measuring accuracy is +/-3 mA.
The phase line current sampling manganese-copper resistor transmits phase line current signals to the metering module 114, the zero line current sampling current transformer 12 transmits zero line current signals to the metering module 114, and a metering chip in the metering module 114 calculates phase line current, zero line current, power and power factor passing through the electric energy meter after analog-digital conversion according to current and voltage signals acquired in real time to read the phase line current, the zero line current, the power and the power factor of the electric energy meter for a main control Module (MCU) 1111, counts electric energy information and transmits the electric energy information to the main control Module (MCU) 1111 in a pulse mode.
The master control Module (MCU) 1111 counts the electricity consumption, and realizes the cost control function through a relay.
The main control Module (MCU) 1111 compares the real-time phase line current I by real-time monitoring Ln * And real-time zero line current I Nn * The absolute difference value of the current range is determined according to specific values of voltage, phase line current, power factor and harmonic component, the pre-allocated current range to which the working condition belongs is read from the storage module 1110, and the IOEC according to the invention corresponding to the working condition is read n 、IOE n According to the residual current formula I △ =||I Ln *|-|I Nn *||-I OEn Or I △ =||I Ln *|-|I Nn *||+I OEn The method comprises the steps of carrying out a first treatment on the surface of the And accurately calculating the residual current value of the output side under the operation condition of the electric energy meter. The main control Module (MCU) 1111 makes corresponding leakage tripping protection, local alarm (audible and visual alarm) of residual current exceeding threshold event and active report of residual current exceeding threshold event according to the set residual current threshold value, and meanwhile, the electric energy meter supports the remote acquisition system to read the residual current, electricity consumption and other related measurement information in real time.
The invention relates to a flow and a method for calibrating phase line current and zero line current (two paths of measured current relation characteristic values and two paths of current measured value mutual deviation values) of an electric energy meter, which comprises the following steps:
the first step is to disconnect the power meter jumper 145, separate the power meter calibration device neutral voltage line from the neutral current post and electrically connect to the power module 115 neutral interface via the jumper 145; the power meter calibration device phase voltage line is electrically connected to the phase interface of the power module 115 through phase inlet 141.
Step two, shorting the phase line outlet 142 to the neutral line outlet 144 (or implementing the electrical connection in the ammeter calibration device); the current signal source output end of the electric energy meter calibrating device is connected with the phase line input 141 of the electric energy meter, and the current signal source input end of the electric energy meter calibrating device is connected with the zero line input 143 of the electric energy meter.
And thirdly, electrifying the calibrated electric energy meter through the electric energy meter calibrating device, and sending a phase line current and zero line current calibrating instruction through the 485 communication module 118 by the upper computer. The current segmentation preset scheme calibration is carried out according to the current measurement range of the electric energy meter, so that the electric energy meter can be ensured to achieve higher current measurement accuracy.
Fourth, when the third step is executed, the electric energy meter program calibrates each section of current according to the flow shown in fig. 2, and at the same time, the electric energy meter program compares and judges the obtained multiple groups of measurement difference values after calibrating each section of phase line current and zero line current, and compares the obtained multiple groups of measurement difference values with each other, and the obtained multiple groups of measurement difference values are compared with each other to obtain the IOEC n Performing corresponding assignment and corresponding storage in the storage module 1110, and simultaneously performing operation on multiple groups of differences by using an arithmetic average method to obtain IOE n And correspondingly stored in the memory module 1110.
And fifthly, according to the analysis of the test data of the specific electric energy meter scheme, carrying out current segmentation preset scheme calibration on the electric energy meter to be calibrated, and repeating the fourth step. Respectively obtain IOE n With IOEC n N=1, n=2, … ….
In a sixth step, after the phase and neutral currents are calibrated, the jumper 145 is shorted to electrically connect the neutral voltage line to the neutral interface of the power module 115 via the neutral input 143.
It should be noted that the above-described apparatus embodiments are merely illustrative, and the units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed over a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. In addition, in the drawings of the embodiment of the device provided by the invention, the connection relation between the modules represents that the modules have communication connection, and can be specifically implemented as one or more communication buses or signal lines. Those of ordinary skill in the art will understand and implement the present invention without undue burden.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the invention.
Claims (6)
1. A method for monitoring residual current, comprising the steps of:
step S1: sampling the same current signal source under the same environment, and respectively obtaining the phase line current and the zero line current of the electric energy meter through a first current sampling element and a second current sampling element;
the first current sampling element is different from the second current sampling element;
the first current sampling element is a phase line current sampling manganese-copper resistor; and/or the second current sampling element is a zero line current sampling current transformer;
step S2: acquiring a fixed reference value based on a mutual deviation value of the phase line current and the zero line current; acquiring two paths of measured current relation characteristic values based on a comparison result of the phase line current and the zero line current; the step S2 of obtaining the fixed reference value based on the mutual deviation value of the phase line current and the neutral line current includes: dividing the current measuring range of the electric energy meter into n sections of current intervals, and taking the mutual deviation value of the effective values of the phase line current and the zero line current obtained by sampling the phase line current sampling manganese-copper resistor and the zero line current sampling current transformer in the n sections of current intervals as a fixed reference value I of the n sections of current intervals OEn The fixed reference value I OEn =||I Ln |-|I Nn I, wherein I Ln For phase line current in the nth current interval, I Nn Zero line current in the nth section current interval; the step S2 of obtaining two paths of measured current relation characteristic values based on the comparison result of the phase line current and the neutral line current includes: dividing the current measuring range of the electric energy meter into n sections of current intervals, comparing the effective values of the phase line current and the zero line current obtained by sampling the phase line current sampling manganese-copper resistor and the zero line current sampling current transformer in the n sections of current intervals, if the absolute value of the phase line current ILn in the n sections of current intervals is larger than the absolute value of the zero line current INn in the n sections of current intervals, taking 1 by two paths of measured current relation characteristic values IOECn, and if the absolute value of the phase line current ILn in the n sections of current intervals is smaller than the absolute value of the zero line current INn in the n sections of current intervals, then taking 1 by two paths of measured current relation characteristic valuesThe path measurement current relation characteristic value IOECn is taken to be 0;
step S3: respectively acquiring real-time phase line current and real-time zero line current through the first current sampling element and the second current sampling element;
step S4: according to the fixed reference value, the two-path measured current relation characteristic value, the real-time phase line current and the real-time zero line current; obtaining residual current;
the electric energy meter monitors the real-time phase line current I according to the working condition of running in the nth section current interval Ln * And real-time zero line current I Nn * And according to the two-way measured current relation characteristic value I of the current interval of the corresponding section OECn And a fixed reference value I OEn Calculating residual current I △ If I OECn =1, then I △ =||I Ln *|-|I Nn *||-I OEn If I OECn =0, then I △ =||I Ln *|-|I Nn *||+I OEn 。
2. A residual current monitoring method as claimed in claim 1, characterized in that: the step S1 of simultaneously sampling the same current signal source under the same environment includes: the electric energy meter can acquire the same current signal source when the phase line current and the zero line current are calibrated in a factory mode.
3. A residual current monitoring method as claimed in claim 2, characterized in that: the electric energy meter can gather same electric current signal source when factory mode calibration phase line electric current and zero line electric current includes: when the phase line current and the zero line current are calibrated by the electric energy meter, the zero line voltage line is electrically disconnected with the primary input side of the zero line current sampling current transformer, and the phase line current sampling manganese-copper resistor and the zero line current sampling current transformer of the electric energy meter collect the same current signal source at the same time.
4. A residual current monitoring method as claimed in claim 3, characterized in that: and after the calibration is finished, the electric connection between the zero line and the primary input side of the zero line current sampling current transformer is restored.
5. A residual current monitoring system, characterized by: comprising a processor and a memory storing instructions executable by the processor to enable the processor to perform the residual current monitoring method of any one of claims 1-4.
6. A single-phase intelligent ammeter, its characterized in that: including electronic plate part, first current sampling element, second current sampling element, binding post row, electric energy meter shell, electronic plate part, first current sampling element, second current sampling element, binding post row all install in the electric energy meter shell, its characterized in that: the electronic board component comprises a main control module and a storage module, wherein the storage module stores the fixed reference value and the two-path measured current relation characteristic value, and the main control module is used for executing a computer program for realizing the residual current monitoring method according to any one of claims 1-4.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211610643.9A CN115932385B (en) | 2022-12-12 | 2022-12-12 | Residual current monitoring method and system and single-phase intelligent electric energy meter |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202211610643.9A CN115932385B (en) | 2022-12-12 | 2022-12-12 | Residual current monitoring method and system and single-phase intelligent electric energy meter |
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| CN115932385A CN115932385A (en) | 2023-04-07 |
| CN115932385B true CN115932385B (en) | 2023-11-17 |
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