CN-121813520-B - Electric energy meter phase sequence switching control method for ensuring safety of CT/PT secondary circuit

CN121813520BCN 121813520 BCN121813520 BCN 121813520BCN-121813520-B

Abstract

The invention relates to the technical field of electric power metering, and particularly discloses a phase sequence switching control method of an electric energy meter, which is used for ensuring the safety of a CT/PT secondary circuit, synchronously acquiring and converting three-phase voltage and current signals, and generating an accurate phase sequence state value by constructing a multidimensional space vector of a phase angle and calculating a space included angle between the multidimensional space vector and a positive sequence reference vector and combining phase dispersion to judge an inverse phase sequence; after the reverse phase sequence is determined, a staged safety switching instruction sequence is generated based on real-time electric state verification, namely, a breaking instruction is sent after the voltage is stabilized, a current short circuit instruction is sent after the voltage is verified to be effectively reduced, a motion unit is driven to execute breaking voltage and short circuit current operation in sequence, a double-contact unit is driven to synchronously switch three-phase wiring, a loop is restored after switching is completed, the phase sequence is verified again, and if multiple failures occur, an adjustment and safety locking mechanism is started.

Inventors

Wang Jingbian
XU PING
WANG LIJUN
Ruan Jiankang
TONG ZEREN
WEN CHENCHEN
LU TAO
CHEN WEILONG

Assignees

国网山西省电力有限公司运城供电分公司

Dates

Publication Date: 20260505
Application Date: 20260309

Claims (10)

1. The electric energy meter phase sequence switching control method for ensuring the safety of the CT/PT secondary circuit is characterized by comprising the following steps of: S1, acquiring three-phase voltage analog quantity and three-phase current analog quantity of an electric energy meter in real time, and respectively converting the three-phase voltage analog quantity and the three-phase current analog quantity into corresponding voltage digital signals and current digital signals; S2, analyzing the voltage digital signal and the current digital signal, extracting real-time phase angles between voltage and current of each phase, constructing coordinates on a unit circle by each phase angle to form a multidimensional space vector, calculating an included angle between the multidimensional space vector and a preset positive sequence reference vector in the multidimensional space, carrying out normalization processing by combining the dispersion of each phase angle, and mapping a normalization processing result into a unique phase sequence state value; S3, when the reverse phase sequence state is judged, a safety switching instruction sequence containing multi-stage instructions is generated, wherein the safety switching instruction sequence comprises a voltage loop disconnection instruction and a current loop short circuit instruction; s4, executing a safety switching instruction sequence in sequence, namely driving a first group of action units to execute voltage loop disconnection operation, and driving a second group of action units to execute current loop short-circuit operation after confirming that the effective value of a voltage digital signal meets a descending condition; S5, after phase sequence exchange is completed, a voltage loop is connected, the short circuit operation of a current loop is released, three-phase voltage and current digital signals are collected again, a phase sequence state value is recalculated, if the phase sequence state value falls within a normal phase sequence threshold value range, switching is completed, if the phase sequence state value is still in an inverse phase sequence state and continuous switching attempts are unsuccessful after reaching preset times, a safety alarm is triggered, and the current state is locked.
2. The method for controlling phase sequence switching of an electric energy meter for ensuring safety of a CT/PT secondary circuit according to claim 1, wherein the forming process of the multidimensional space vector is as follows: extracting real-time phase angles corresponding to the voltage digital signals and the current digital signals of each phase; For each real-time phase angle, calculating cosine coordinates and sine coordinates of the real-time phase angle on a unit circle; And arranging the cosine coordinates and the sine coordinates of the three phases in sequence according to the sequence of the first phase, the second phase and the third phase to form a multidimensional space vector.
3. The method for controlling phase sequence switching of an electric energy meter for ensuring safety of a CT/PT secondary circuit according to claim 1, wherein the calculating process of the phase sequence state value is as follows: calculating a cosine value of a space included angle between the multidimensional space vector and a preset positive sequence reference vector; calculating a dispersion index of each phase real-time phase angle, wherein the dispersion index is the sum of absolute values of differences between each phase angle and the average phase angle; carrying out weighted summation on the cosine value of the space included angle and the dispersion index to obtain a weighted summation value; And carrying out inverse cotangent function transformation on the weighted sum value to obtain a phase sequence state value.
4. The method for controlling phase sequence switching of an electric energy meter for ensuring safety of a secondary circuit of a CT/PT according to claim 1, wherein the triggering condition of the voltage loop breaking command is determined by: acquiring the effective value of the current voltage digital signal of each phase in a complete power frequency period; comparing the voltage effective values of all phases with a preset voltage effective value threshold, and judging whether the power supply effective values of all phases exceed the voltage effective value threshold for a first preset time period; Calculating the fluctuation rate of the voltage effective value of each phase in a first preset time period; and if the fluctuation rate is lower than a preset fluctuation threshold value, confirming that a voltage loop disconnection instruction is generated.
5. The method for controlling phase sequence switching of an electric energy meter for ensuring safety of a CT/PT secondary circuit according to claim 1, wherein the triggering condition judgment process of the current loop short circuit instruction is as follows: After executing the voltage loop disconnection instruction, delaying a second preset time period, collecting each phase of voltage digital signals again, and calculating the effective value of each phase of voltage digital signals; Comparing the collected effective value of each phase voltage with the original effective value recorded before executing the disconnection instruction, and calculating the effective value reduction ratio of each phase voltage; Judging whether the effective value falling ratios of the voltages of all phases reach or exceed a preset falling ratio threshold value, maintaining a third preset duration, and confirming generation of a current loop short circuit instruction.
6. The method for controlling phase sequence switching of an electric energy meter for ensuring safety of a secondary circuit of a CT/PT according to claim 1, wherein S4 specifically comprises: after confirming that the short circuit operation of the current loop is finished, sending a synchronous switching instruction to a third group of double-contact action units; Three independent units in the third group of double-contact action units respectively control three phases, and each unit synchronously disconnects the movable contact from the first fixed contact and is connected to the second fixed contact after receiving the instruction; After connection switching is completed, detecting whether analog quantities of voltages and currents of all phases establish an effective path or not again; after all phases confirm to establish effective paths, phase sequence exchange is completed, and the connection relation between voltage and current is exchanged synchronously.
7. The method for controlling phase sequence switching of an electric energy meter for ensuring safety of a secondary circuit of a CT/PT according to claim 6, wherein after the connection switching is completed, detecting whether the analog quantity of the voltage and the current of each phase establishes an effective path again comprises the following steps: The analog quantity of each phase voltage and current after connection switching is collected again and is converted into a corresponding voltage verification digital signal and a corresponding current verification digital signal respectively; The method comprises the steps of carrying out validity verification on a voltage verification digital signal and a current verification digital signal, wherein the method comprises the steps of judging whether a signal amplitude is in a preset effective amplitude interval or not, and judging whether a signal waveform is continuous and uninterrupted in a complete power frequency period or not; based on the validity verification result of each phase of voltage and current verification digital signals, calculating and generating a comprehensive path validity index; When the composite path validity index is greater than or equal to the validity threshold, then it is determined that all phases establish a valid path.
8. The method for controlling phase sequence switching of an electric energy meter for ensuring safety of a CT/PT secondary circuit according to claim 7, wherein the calculation process of the comprehensive path effectiveness index is as follows: Obtaining an amplitude verification result by judging whether the effective value of each phase of voltage and current verification digital signal is in a preset effective amplitude interval; Obtaining a waveform continuity verification result by analyzing whether sampling point sequences of each phase of voltage verification digital signal and current verification digital signal are continuous and uninterrupted in a complete power frequency period; respectively quantizing amplitude verification results and waveform continuity verification results of the voltage verification digital signals and the current verification digital signals of each phase into a first quantized value and a second quantized value; performing product operation on the first quantized value and the second quantized value of each phase to obtain single-phase path reliability coefficients of each phase; sequencing the reliability coefficients of the three-phase single-phase paths, and giving different weighting weights to the sequenced coefficients; And accumulating and summing all weighted single-phase path reliability coefficients, and mapping the summation result to a preset interval through a preset normalization function to obtain a comprehensive path effectiveness index.
9. The method for controlling phase sequence switching of an electric energy meter for ensuring safety of a secondary circuit of a CT/PT according to claim 1, wherein the triggering of the safety alarm and locking of the current state specifically comprises: When the continuous switching trial number reaches the preset number and the phase sequence state value is still in the reverse phase sequence state, recording each phase sequence state value corresponding to the current and historical failed trial; analyzing the distribution characteristics of each phase sequence state value in the historical failure record, and adjusting the offset of the negative phase sequence judgment threshold value based on the distribution characteristics; If the phase sequence state value still falls into the reverse phase sequence range according to the dynamically adjusted threshold value, generating a safety alarm instruction and simultaneously sending a state locking instruction to all action units; the state locking instruction keeps all action units in an instant state when the security alarm instruction is executed, and locks the subsequent receiving and executing of any external switching instruction.
10. The method for controlling phase sequence switching of an electric energy meter for ensuring safety of a secondary circuit of a CT/PT according to claim 9, wherein the adjusting the offset of the negative phase sequence decision threshold based on the distribution characteristics specifically comprises: Extracting all phase sequence state values from the historical failure record, and forming a state value sequence according to the sequence of the occurrence of the attempt; analyzing the numerical distribution of the state value sequence, and calculating the aggregation degree and the aggregation center position of the numerical value near the inverse phase sequence judgment threshold value; calculating according to a preset proportion according to the offset direction and the offset distance of the aggregation center position relative to the original inverse phase sequence judgment threshold value to obtain a threshold value offset; Algebraic addition is carried out on the threshold offset and the original negative phase sequence judgment threshold to obtain an adjusted negative phase sequence judgment threshold.

Description

Electric energy meter phase sequence switching control method for ensuring safety of CT/PT secondary circuit Technical Field The invention relates to the technical field of electric power metering, in particular to an electric energy meter phase sequence switching control method for ensuring the safety of a CT/PT secondary circuit. Background With the promotion of smart grid construction, although some researches discuss the phase sequence automatic identification and switching technology, most of the techniques stay in a theoretical or simulation stage. Few devices in practical application are also often focused on phase sequence judgment, and in a switching action execution link, the core safety problem that the secondary side of a Current Transformer (CT) is strictly forbidden to open a circuit and the secondary side of a voltage transformer (PT) is strictly forbidden to short a circuit in a switching process cannot be thoroughly solved. The switching process of the existing scheme is still required to be confirmed by manual intervention, or the safety logic is not complete enough, so that the switching process is difficult to ensure in a complex field environment. Therefore, how to design an intelligent phase sequence switching method capable of absolutely ensuring the operation safety of the CT/PT secondary circuit on the premise of full automation and no power failure becomes a key technical requirement for improving the safety, reliability and intelligence level of metering operation. Disclosure of Invention The invention aims to provide an electric energy meter phase sequence switching control method for ensuring the safety of a CT/PT secondary circuit, so as to solve the technical problems. The aim of the invention can be achieved by the following technical scheme: A phase sequence switching control method for ensuring the safety of a CT/PT secondary circuit of an electric energy meter comprises the following steps: S1, acquiring three-phase voltage analog quantity and three-phase current analog quantity of an electric energy meter in real time, and respectively converting the three-phase voltage analog quantity and the three-phase current analog quantity into corresponding voltage digital signals and current digital signals; S2, analyzing the voltage digital signal and the current digital signal, extracting real-time phase angles between voltage and current of each phase, constructing coordinates on a unit circle by each phase angle to form a multidimensional space vector, calculating an included angle between the multidimensional space vector and a preset positive sequence reference vector in the multidimensional space, carrying out normalization processing by combining the dispersion of each phase angle, and mapping a normalization processing result into a unique phase sequence state value; S3, when the reverse phase sequence state is judged, a safety switching instruction sequence containing multi-stage instructions is generated, wherein the safety switching instruction sequence comprises a voltage loop disconnection instruction and a current loop short circuit instruction; s4, executing a safety switching instruction sequence in sequence, namely driving a first group of action units to execute voltage loop disconnection operation, and driving a second group of action units to execute current loop short-circuit operation after confirming that the effective value of a voltage digital signal meets a descending condition; S5, after phase sequence exchange is completed, a voltage loop is connected, the short circuit operation of a current loop is released, three-phase voltage and current digital signals are collected again, a phase sequence state value is recalculated, if the phase sequence state value falls within a normal phase sequence threshold value range, switching is completed, if the phase sequence state value is still in an inverse phase sequence state and continuous switching attempts are unsuccessful after reaching preset times, a safety alarm is triggered, and the current state is locked. As a further scheme of the invention, the formation process of the multidimensional space vector comprises the following steps: extracting real-time phase angles corresponding to the voltage digital signals and the current digital signals of each phase; For each real-time phase angle, calculating cosine coordinates and sine coordinates of the real-time phase angle on a unit circle; And arranging the cosine coordinates and the sine coordinates of the three phases in sequence according to the sequence of the first phase, the second phase and the third phase to form a multidimensional space vector. The invention further provides a method for calculating the phase sequence state value, which comprises the following steps: calculating a cosine value of a space included angle between the multidimensional space vector and a preset positive sequence reference vector; calculating a dispersion index of each phas