Calculation method and system for three-phase residual current abrupt change protection

Abstract

The invention provides a three-phase residual current abrupt change protection calculation method and system, and the method comprises the steps: S1, collecting the electric parameters of a street lamp line, calculating the vector sum of three-phase current at an initial moment according to the electric parameters of the street lamp line, and recording the amplitude and phase of the vector sum of the three-phase current; the amplitude and the phase of the residual current on the three-phase line at the same moment are calculated and recorded; s2, setting interval time, and after the interval time, calculating the amplitude and the phase of the vector sum of the three-phase current at the interval time and the amplitude and the phase of the residual current of the three-phase line; s3, calculating the amplitude change and the phase change of the three-phase current vector sum between the initial moment and the interval moment, and the difference between the amplitude change and the phase change of the three-phase line residual current and the amplitude change and the phase change of the three-phase line residual current; and S4, judging whether a residual current abrupt change protection mechanism needs to be triggered or not according to the difference between the amplitude change and the phase change. According to the invention, the residual current change of each phase during three-phase power supply can be effectively identified.

Description

Technical Field

[0001] The present invention relates to the technical field of three-phase residual current monitoring, and in particular to a calculation method for effectively identifying the residual current changes of each phase during three-phase power supply, and in particular to a calculation method and system for three-phase residual current mutation protection. Background Art

[0002] Municipal street lights, as an important part of urban infrastructure, have brought a lot of convenience to people's lives. However, their unique characteristics also bring some hidden dangers. Aging of street light power supply cables and random excavation during construction may generate residual current, causing street light poles to be electrified, which may lead to pedestrian injuries / deaths. The issue of electricity safety of municipal street lights has received more and more attention from relevant departments.

[0003] Existing residual current protectors generally monitor the residual current amplitude on the power supply line, and alarm when the residual current amplitude of the line exceeds the alarm threshold, and perform a tripping operation when the residual current amplitude of the line exceeds the tripping threshold. Some residual current protectors monitor the sudden change of the residual current of the line, and perform a tripping protection when the amplitude and phase of the residual current change and exceed the set value.

[0004] The above two residual current monitoring methods cannot fully cover residual current related scenarios. Municipal street lamp lines are mostly three-phase power supply, and residual current may be generated in all three phases to the ground. The residual current monitored by the residual current protector is the final value after the three-phase vector is superimposed. The increase of the residual current of one phase to the ground may cause the residual current vector sum of the three-phase line to decrease. Figure 1 As shown in the figure (after the C phase residual current Irc increases, the vector sum of the residual currents in the three-phase line will decrease. The existing residual current protector detects that the amplitude of the residual current in the three-wire line decreases and the phase does not change, so it will not provide protection and may even eliminate the alarm). Figure 1 Where Ua, Ub, Uc are three-phase voltages, Ira, Irb, Irc are residual currents of the three-phase lines, and Ir is the vector sum of the residual currents of the three-phase lines.

[0005] The electricity safety of municipal street lamps is receiving more and more attention from municipal street lamp management departments. The current residual current protector monitors the residual current amplitude and phase changes, but cannot identify and alarm the changes in the residual current of each phase when the three-phase power supply is in operation.

[0006] Explanation of relevant terms:

[0007] Residual current: The current whose vector sum of currents in each phase (including neutral line) in the low-voltage distribution line is not zero.

[0008] Vector: A quantity that has both size (amplitude) and direction (phase).

[0009] Street light control and management terminal: A device installed in the street light distribution cabinet that has the functions of automatically controlling street light circuit switches, collecting operation information, and exchanging data with the main station. Summary of the invention

[0010] In view of the defects in the prior art, the present invention provides a calculation method and system for three-phase residual current mutation protection.

[0011] According to a calculation method and system for three-phase residual current mutation protection provided by the present invention, the scheme is as follows:

[0012] In a first aspect, a calculation method for three-phase residual current mutation protection is provided, the method comprising:

[0013] Step S1: Collecting electrical parameters of the street light line, calculating the vector sum of the three-phase current at the initial moment according to the electrical parameters of the street light line, and recording the amplitude and phase of the vector sum of the three-phase current; calculating the amplitude and phase of the residual current on the three-phase line at the same moment and recording them;

[0014] Step S2: setting an interval time, and after the interval time has passed, calculating the amplitude and phase of the three-phase current vector sum and the amplitude and phase of the three-phase line residual current at the interval time;

[0015] Step S3: Calculate the amplitude change and phase change of the three-phase current vector sum between the initial moment and the interval moment, and the difference between the amplitude change and phase change of the residual current of the three-phase line;

[0016] Step S4: Set the difference allowable error. When the above amplitude change and phase change differences are within the difference allowable error, analyze the sudden change of residual current on each phase line, and determine whether the residual current sudden change protection mechanism needs to be triggered according to the sudden change of residual current in each phase.

[0017] Preferably, the step S1 collects electrical parameters of the street lamp line, including the residual current value of the three-phase line, the phase value of the residual current and voltage of the three-phase line, the current value of the three-phase line, and the phase value of the current and voltage of the three-phase line.

[0018] Preferably, in step S2, the interval time is set to be a regular refresh, and data is collected, calculated and updated in real time.

[0019] Preferably, step S3 comprises:

[0020] Calculate the difference a between the amplitude change of the three-phase current vector sum and the amplitude change of the three-phase line residual current from the initial time t0 to the interval time t1;

[0021] a=|(A I1 -A I0 )-(A Ir1-A Ir0 )|

[0022] Calculate the difference p between the phase change of the three-phase current vector sum and the phase change of the three-phase line residual current from the initial time t0 to the interval time t1;

[0023] p=|(P I1 -P I0 )-(P Ir1 -P Ir0 )|

[0024] Among them, A I1 is the amplitude of the three-phase current vector sum at time t1, A I0 is the amplitude of the three-phase current vector sum at time t0; A Ir1 is the amplitude of the residual current on the three-phase line at time t1, A Ir0 is the amplitude of the residual current on the three-phase line at time t0; P I1 is the phase of the three-phase current vector sum at time t1, P I0 is the phase of the three-phase current vector sum at time t0; P Ir1 is the phase of the residual current on the three-phase line at time t1, P Ir0 It is the phase of the residual current on the three-phase line at time t0.

[0025] Preferably, the step S4 comprises:

[0026] When the amplitude change difference a≤A and the phase change difference p≤P, it is determined that the residual current change of the three-phase line is consistent with the three-phase line current change at the same time. At this moment, the current change of each phase of the three-phase line is the residual current change; A is the allowable error of the amplitude change difference, which is set according to the protection sensitivity; P is the allowable error of the phase change difference, which is set according to the protection sensitivity;

[0027] Calculate the residual current mutation value r of phases A, B, and C a 、r b 、r c , if the residual current mutation value of any phase exceeds the set mutation protection threshold, the circuit breaker protection will be performed;

[0028] r a =|I a1 ×cos(θ a1 )-I a0 ×cos(θ a0 )|

[0029] r b =|I b1 ×cos(θ b1 )-I b0 ×cos(θ b0 )|

[0030] r c =|I c1 ×cos(θ c1 )-I c0 ×cos(θ c0 )|

[0031] Among them, r a 、r b 、r c are the same-phase mutation values ​​of the residual current of phases A, B, and C from t0 to t1, I a1 ,I b1 ,I c1 are the current values ​​of phases A, B, and C at time t1, θ a1 ,θ b1 ,θ c1 are the phase angles of the current and the same-phase voltage of phase A, B, and C at time t1, I a0 ,I b0 ,I c0 are the current values ​​of phases A, B, and C at time t0, θ a0 ,θ b0 ,θ c0 are the phase angles of the current and the in-phase voltage of phases A, B, and C at time t0 respectively;

[0032] When the amplitude change difference a>A or the phase change difference p>P, it is determined that the current of each phase of the three-phase line is load current fluctuation or does not reach the protection sensitivity, and the residual current mutation protection mechanism is not triggered.

[0033] In a second aspect, a calculation system for three-phase residual current mutation protection is provided, the system comprising:

[0034] Module M1: Collect electrical parameters of the street light line, calculate the vector sum of the three-phase current at the initial moment according to the electrical parameters of the street light line, and record the amplitude and phase of the vector sum of the three-phase current; calculate the amplitude and phase of the residual current on the three-phase line at the same moment and record them;

[0035] Module M2: Set the interval time, and after the interval time has passed, calculate the amplitude and phase of the three-phase current vector sum and the amplitude and phase of the three-phase line residual current at the interval time;

[0036] Module M3: Calculate the amplitude change and phase change of the three-phase current vector sum between the initial moment and the interval moment, and the difference between the amplitude change and phase change of the residual current of the three-phase line;

[0037] Module M4: Set the difference allowable error. When the above amplitude change and phase change differences are within the difference allowable error, analyze the sudden change of residual current on each phase line, and determine whether the residual current sudden change protection mechanism needs to be triggered according to the sudden change of residual current in each phase.

[0038] Preferably, the module M1 collects electrical parameters of the street lamp line, including the residual current value of the three-phase line, the phase value of the residual current and voltage of the three-phase line, the current value of the three-phase line, and the phase value of the current and voltage of the three-phase line.

[0039] Preferably, the module M2 is configured with an interval time for periodic refresh, so as to collect, calculate and update data in real time.

[0040] Preferably, the module M3 comprises:

[0041] Calculate the difference a between the amplitude change of the three-phase current vector sum and the amplitude change of the three-phase line residual current from the initial time t0 to the interval time t1;

[0042] a=|(A I1 -A I0 )-(A Ir1 -A Ir0 )|

[0043] Calculate the difference p between the phase change of the three-phase current vector sum and the phase change of the three-phase line residual current from the initial time t0 to the interval time t1;

[0044] p=|(P I1 -P I0 )-(P Ir1 -P Ir0 )|

[0045] Among them, A I1 is the amplitude of the three-phase current vector sum at time t1, A I0 is the amplitude of the three-phase current vector sum at time t0; A Ir1 is the amplitude of the residual current on the three-phase line at time t1, A Ir0 is the amplitude of the residual current on the three-phase line at time t0; P I1 is the phase of the three-phase current vector sum at time t1, P I0 is the phase of the three-phase current vector sum at time t0; P Ir1 is the phase of the residual current on the three-phase line at time t1, P Ir0 It is the phase of the residual current on the three-phase line at time t0.

[0046] Preferably, the module M4 comprises:

[0047] When the amplitude change difference a≤A and the phase change difference p≤P, it is determined that the residual current change of the three-phase line is consistent with the three-phase line current change at the same time. At this moment, the current change of each phase of the three-phase line is the residual current change; A is the allowable error of the amplitude change difference, which is set according to the protection sensitivity; P is the allowable error of the phase change difference, which is set according to the protection sensitivity;

[0048] Calculate the residual current mutation value r of phases A, B, and C a 、r b 、r c , if the residual current mutation value of any phase exceeds the set mutation protection threshold, the circuit breaker protection will be performed;

[0049] r a =|I a1 ×cos(θ a1 )-I a0 ×cos(θ a0 )|

[0050] r b =|I b1 ×cos(θ b1 )-I b0 ×cos(θ b0 )|

[0051] r c =|I c1 ×cos(θ c1 )-I c0 ×cos(θ c0 )|

[0052] Among them, r a 、r b 、r c are the same-phase mutation values ​​of the residual current of phases A, B, and C from t0 to t1, I a1 ,I b1 ,I c1 are the current values ​​of phases A, B, and C at time t1, θ a1 ,θ b1 ,θ c1 are the phase angles of the current and the same-phase voltage of phase A, B, and C at time t1, I a0 ,I b0 ,I c0 are the current values ​​of phases A, B, and C at time t0, θ a0 ,θ b0 ,θ c0 are the phase angles of the current and the in-phase voltage of phases A, B, and C at time t0 respectively;

[0053] When the amplitude change difference a>A or the phase change difference p>P, it is determined that the current of each phase of the three-phase line is load current fluctuation or does not reach the protection sensitivity, and the residual current mutation protection mechanism is not triggered.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] 1. The present invention monitors the electrical parameters of the three-phase line in real time, judges and analyzes the change of the current vector sum and the residual current of the three-wire line, and solves the current three-phase line scenario that can only analyze the total residual current change but cannot effectively locate the residual current change of each single-phase, resulting in the safety problem that some single-phase residual current increases but the total residual current of the three-phase decreases and cannot alarm / trip;

[0056] 2. The present invention reduces the monitoring blind spots of the residual current of the three-phase line by analyzing the changes of each single-phase residual current in the three-phase line, and effectively improves the safety of three-phase electricity use such as municipal street lamps.

[0057] Other beneficial effects of the present invention will be explained in the specific implementation manner through the introduction of specific technical features and technical solutions. Through the introduction of these technical features and technical solutions, those skilled in the art should be able to understand the beneficial technical effects brought about by the technical features and technical solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0059] Figure 1 It is the residual current vector analysis diagram of three-phase line;

[0060] Figure 2 It is a schematic diagram of the process of the present invention;

[0061] Figure 3a-3b They are respectively a current vector analysis diagram of a three-phase line at an initial moment and a residual current vector analysis diagram of a three-phase line at an initial moment of the present invention;

[0062] Figure 4a-4b They are respectively a current vector analysis diagram of a three-phase line at an interval and a residual current vector analysis diagram of a three-phase line at an interval of the present invention;

[0063] Figure 5a-5b They are respectively a schematic diagram of the current vector sum of the three-phase line of the present invention before and after the change, and a schematic diagram of the residual current of the three-phase line before and after the change. DETAILED DESCRIPTION

[0064] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0065] The embodiment of the present invention provides a calculation method for three-phase residual current mutation protection, which monitors the electrical parameters of the municipal street light line through the street light control management terminal, including the residual current value of the three-phase line, the phase value of the residual current and voltage of the three-phase line, the current value of the three-phase line, and the phase value of the current and voltage of the three-phase line. Figure 2 As shown, the method specifically includes:

[0066] Step S1: Calculate the vector sum I0 of the three-phase current at time t0 in real time, and record the amplitude and phase of the three-phase current vector sum I0; calculate the amplitude and phase of the residual current Ir0 on the three-phase line at the same time and record them. Figure 3a-3b As shown, Figure 3a-3b Where Ua, Ub, Uc are the A, B, C phase voltages respectively, Ia0, Ib0, Ic0 are the real-time currents of A, B, C phases at t0 respectively, I0 is the vector sum of the three-phase currents at t0; Ir0 is the real-time residual current on the three-phase line at t0.

[0067] Step S2: Refresh regularly (the refresh interval can be set, the default is 100mS) to calculate the amplitude and phase of the three-phase current vector sum I1 at time t1, and the amplitude and phase of the three-phase line residual current Ir1. Figure 4a-4b As shown, Figure 4a-4b In the figure, Ua, Ub, Uc are the A, B, C phase voltages respectively, Ia1, Ib1, Ic1 are the A, B, C phase real-time currents respectively, I1 is the three-phase current vector sum; Ir1 is the real-time residual current on the three-phase line.

[0068] Municipal lighting generally uses three-phase four-wire (A, B, C, N) to supply power at the distribution cabinet, and uses a phase and neutral wire to power the lamps at the street light pole. There are many loads under each circuit, and sometimes different types of lamps (sodium lamps, LED lamps, etc.) coexist. The operating status of each lamp may cause the three-phase circuit current to change (for example, if a lamp is off, the phase current decreases, and if a lamp is on, the corresponding phase current increases; there are also dimming changes, and the load is resistive, capacitive, inductive and other types of different situations). However, when there is no leakage fault in the line, there is no residual current on the three-phase four-wire (A, B, C, N), and the change of phase current has no correlation with the residual current. When the power supply line cable is damaged or an electric shock alarm occurs, the phase line current flows into the ground, and residual current is generated at this time. The lines and loads of municipal lighting are complex, and there are countless possibilities for changes in phase current and residual current. Therefore, the present invention provides a method for effectively identifying a sudden change in residual current and determining it as a change in residual current of a specific phase line. That is, when the vector sum change of the three-phase current is basically consistent with the change of the residual current, it is determined that the sudden change in phase current is caused by the residual current, thereby ensuring the safety of electricity use.

[0069] Step S3: Calculate the amplitude change and phase change of the three-phase current vector sum between the initial moment and the interval moment, and the difference between the amplitude change and phase change of the residual current of the three-phase line.

[0070] Specifically, refer to Figure 5a-5b As shown, Figure 5a-5b Where Ua, Ub, Uc are the A, B, C phase voltages respectively, I0, I1 are the vector sum of the three-phase currents at t0, t1 respectively, Ir0, Ir1 are the real-time residual currents on the three-phase lines at t0, t1 respectively.

[0071] Calculate the difference a between the amplitude change of the three-phase current vector sum and the amplitude change of the three-phase line residual current from the initial time t0 to the interval time t1;

[0072] a=|(A I1 -A I0 )-(A Ir1 -A Ir0 )|

[0073] Calculate the difference p between the phase change of the three-phase current vector sum and the phase change of the three-phase line residual current from the initial time t0 to the interval time t1;

[0074] p=|(P I1 -P I0 )-(P Ir1 -P Ir0 )|

[0075] Among them, A I1is the amplitude of the three-phase current vector sum at time t1, A I0 is the amplitude of the three-phase current vector sum at time t0; A Ir1 is the amplitude of the residual current on the three-phase line at time t1, A Ir0 is the amplitude of the residual current on the three-phase line at time t0; P I1 is the phase of the three-phase current vector sum at time t1, P I0 is the phase of the three-phase current vector sum at time t0; P Ir1 is the phase of the residual current on the three-phase line at time t1, P Ir0 It is the phase of the residual current on the three-phase line at time t0.

[0076] Step S4: Determine whether the residual current mutation protection mechanism needs to be triggered according to the difference between the amplitude change and the phase change.

[0077] Specifically, when the amplitude change difference a≤A (A is the allowable error of the amplitude change difference, which can be set according to the protection sensitivity) and the phase change difference p≤P (P is the allowable error of the phase change difference, which can be set according to the protection sensitivity), it is determined that the residual current change of the three-phase line at the same time is consistent with the three-phase line current change. At this moment, the current change of each phase of the three-phase line is the residual current change. Calculate the residual current mutation value r of the three phases A, B, and C a 、r b 、r c If the sudden change value of residual current in any phase exceeds the set sudden change protection threshold, the circuit breaker will be opened for protection.

[0078] r a =|I a1 ×cos(θ a1 )-I a0 ×cos(θ a0 )|

[0079] r b =|I b1 ×cos(θ b1 )-I b0 ×cos(θ b0 )|

[0080] r c =|I c1 ×cos(θ c1 )-I c0 ×cos(θ c0 )|

[0081] Among them, r a 、r b 、r care the same-phase mutation values ​​of the residual current of phases A, B, and C from t0 to t1 (the residual current that is dangerous to the human body is generally resistive, so the residual current mutation with the same phase as the voltage of each phase is calculated), I a1 ,I b1 ,I c1 are the current values ​​of phases A, B, and C at time t1, θ a1 ,θ b1 ,θ c1 are the phase angles of the current and the same-phase voltage of phase A, B, and C at time t1, I a0 ,I b0 ,I c0 are the current values ​​of phases A, B, and C at time t0, θ a0 ,θ b0 ,θ c0 They are the phase angles of the current and the in-phase voltage of phases A, B, and C at time t0 respectively.

[0082] When the amplitude change difference a>A or the phase change difference p>P, it is determined that the current of each phase of the three-phase line is load current fluctuation or does not reach the protection sensitivity, and the residual current mutation protection mechanism is not triggered.

[0083] The present invention also provides a calculation system for three-phase residual current mutation protection, which can be implemented by executing the process steps of the calculation method for three-phase residual current mutation protection, that is, those skilled in the art can understand the calculation method for three-phase residual current mutation protection as a preferred implementation of the calculation system for three-phase residual current mutation protection. The system specifically includes:

[0084] Module M1: Calculate the vector sum I0 of the three-phase current at time t0 in real time, record the amplitude and phase of the three-phase current vector sum I0; calculate the amplitude and phase of the residual current Ir0 on the three-phase line at the same time and record them, as shown in Figure 3.

[0085] Module M2: Timed refresh (refresh interval can be set, default is 100mS) calculates the amplitude and phase of the three-phase current vector sum I1 at time t1, and the amplitude and phase of the three-phase line residual current Ir1, as shown in Figure 4.

[0086] Municipal lighting generally uses three-phase four-wire (A, B, C, N) to supply power at the distribution cabinet, and uses a phase and neutral wire to power the lamps at the street light pole. There are many loads under each circuit, and sometimes different types of lamps (sodium lamps, LED lamps, etc.) coexist. The operating status of each lamp may cause the three-phase circuit current to change (for example, if a lamp is off, the phase current decreases, and if a lamp is on, the corresponding phase current increases; there are also dimming changes, and the load is resistive, capacitive, inductive and other types of different situations). However, when there is no leakage fault in the line, there is no residual current on the three-phase four-wire (A, B, C, N), and the change of phase current has no correlation with the residual current. When the power supply line cable is damaged or an electric shock alarm occurs, the phase line current flows into the ground, and residual current is generated at this time. The lines and loads of municipal lighting are complex, and there are countless possibilities for changes in phase current and residual current. Therefore, the present invention provides a method for effectively identifying a sudden change in residual current and determining it as a change in residual current of a specific phase line. That is, when the vector sum change of the three-phase current is basically consistent with the change of the residual current, it is determined that the sudden change in phase current is caused by the residual current, thereby ensuring the safety of electricity use.

[0087] Module M3: Calculate the amplitude change and phase change of the three-phase current vector sum between the initial moment and the interval moment, and the difference between the amplitude change and phase change of the residual current of the three-phase line.

[0088] Specifically, as shown in FIG5 , the difference a between the amplitude change of the three-phase current vector sum and the amplitude change of the three-phase line residual current from the initial time t0 to the interval time t1 is calculated;

[0089] a=|(A I1 -A I0 )-(A Ir1 -A Ir0 )|

[0090] Calculate the difference p between the phase change of the three-phase current vector sum and the phase change of the three-phase line residual current from the initial time t0 to the interval time t1;

[0091] p=|(P I1 -P I0 )-(P Ir1 -P Ir0 )|

[0092] Among them, A I1 is the amplitude of the three-phase current vector sum at time t1, A I0 is the amplitude of the three-phase current vector sum at time t0; A Ir1 is the amplitude of the residual current on the three-phase line at time t1, A Ir0 is the amplitude of the residual current on the three-phase line at time t0; P I1is the phase of the three-phase current vector sum at time t1, P I0 is the phase of the three-phase current vector sum at time t0; P Ir1 is the phase of the residual current on the three-phase line at time t1, P Ir0 It is the phase of the residual current on the three-phase line at time t0.

[0093] Module M4: Determine whether the residual current mutation protection mechanism needs to be triggered according to the difference between the above amplitude change and phase change.

[0094] Specifically, when the amplitude change difference a≤A (A is the allowable error of the amplitude change difference, which can be set according to the protection sensitivity) and the phase change difference p≤P (P is the allowable error of the phase change difference, which can be set according to the protection sensitivity), it is determined that the residual current change of the three-phase line at the same time is consistent with the three-phase line current change. At this moment, the current change of each phase of the three-phase line is the residual current change. Calculate the residual current mutation value r of the three phases A, B, and C a 、r b 、r c If the sudden change value of residual current in any phase exceeds the set sudden change protection threshold, the circuit breaker will be opened for protection.

[0095] r a =|I a1 ×cos(θ a1 )-I a0 ×cos(θ a0 )|

[0096] r b =|I b1 ×cos(θ b1 )-I b0 ×cos(θ b0 )|

[0097] r c =|I c1 ×cos(θ c1 )-I c0 ×cos(θ c0 )|

[0098] Among them, r a 、r b 、r c are the same-phase mutation values ​​of the residual current of phases A, B, and C from t0 to t1 (the residual current that is dangerous to the human body is generally resistive, so the residual current mutation with the same phase as the voltage of each phase is calculated), I a1 ,I b1 ,I c1 are the current values ​​of phases A, B, and C at time t1, θ a1 ,θ b1 ,θc1 are the phase angles of the current and the same-phase voltage of phase A, B, and C at time t1, I a0 ,I b0 ,I c0 are the current values ​​of phases A, B, and C at time t0, θ a0 ,θ b0 ,θ c0 They are the phase angles of the current and the in-phase voltage of phases A, B, and C at time t0 respectively.

[0099] When the amplitude change difference a>A or the phase change difference p>P, it is determined that the current of each phase of the three-phase line is load current fluctuation or does not reach the protection sensitivity, and the residual current mutation protection mechanism is not triggered.

[0100] The embodiment of the present invention provides a calculation method and system for three-phase residual current mutation protection, which can effectively analyze the residual current mutation of each single phase in the three-phase line, and solve the problem that when the residual current in the three-phase line suddenly increases, the total vector and residual current amplitude monitored by the residual current protector may become smaller or remain unchanged, resulting in the inability to play a protective role at this time, thereby further improving the safety of three-phase power use in municipal street lamps.

[0101] Those skilled in the art know that, in addition to realizing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, it is entirely possible to realize the same functions in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be regarded as structures within the hardware component; the devices, modules, and units for realizing various functions can also be regarded as both software modules for realizing the method and structures within the hardware component.

[0102] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A calculation method for three-phase residual current mutation protection, characterized in that: include: Step S1: collecting electrical parameters of the street light line, calculating the vector sum of the three-phase current at the initial moment according to the electrical parameters of the street light line, and recording the amplitude and phase of the vector sum of the three-phase current; Calculate the amplitude and phase of the residual current on the three-phase line at the same moment and record them; Step S2: setting an interval time, and after the interval time has passed, calculating the amplitude and phase of the three-phase current vector sum and the amplitude and phase of the three-phase line residual current at the interval time; Step S3: Calculate the amplitude change and phase change of the three-phase current vector sum between the initial moment and the interval moment, and the difference between the amplitude change and phase change of the residual current of the three-phase line; Step S4: Set the difference allowable error. When the above amplitude change and phase change differences are within the difference allowable error, analyze the sudden change of residual current on each phase line, and determine whether the residual current sudden change protection mechanism needs to be triggered according to the sudden change of residual current in each phase.

2. The calculation method for three-phase residual current sudden change protection according to claim 1 is characterized in that: The step S1 collects electrical parameters of the street lamp line, including the residual current value of the three-phase line, the phase value of the residual current and voltage of the three-phase line, the current value of the three-phase line, and the phase value of the current and voltage of the three-phase line.

3. The calculation method for three-phase residual current mutation protection according to claim 1 is characterized in that: In step S2, the interval time is set to be a regular refresh, and data is collected, calculated and updated in real time.

4. The calculation method for three-phase residual current sudden change protection according to claim 1 is characterized in that: The step S3 comprises: Calculate the difference a between the amplitude change of the three-phase current vector sum and the amplitude change of the three-phase line residual current from the initial time t0 to the interval time t1; a=|(A I1 -A I0 )-(A Ir1 -A Ir0 )| Calculate the difference p between the phase change of the three-phase current vector sum and the phase change of the three-phase line residual current from the initial time t0 to the interval time t1; p=|(P I1 -P I0 )-(P Ir1 -P Ir0 )| Among them, A I1 is the amplitude of the three-phase current vector sum at time t1, A I0 is the amplitude of the three-phase current vector sum at time t0; A Ir1 is the amplitude of the residual current on the three-phase line at time t1, A Ir0 is the amplitude of the residual current on the three-phase line at time t0; P I1 is the phase of the three-phase current vector sum at time t1, P I0 is the phase of the three-phase current vector sum at time t0; P Ir1 is the phase of the residual current on the three-phase line at time t1, P Ir0 It is the phase of the residual current on the three-phase line at time t0.

5. The calculation method for three-phase residual current sudden change protection according to claim 4 is characterized in that: The step S4 comprises: When the amplitude change difference a≤A and the phase change difference p≤P, it is determined that the residual current change of the three-phase line is consistent with the three-phase line current change at the same time. At this moment, the current change of each phase of the three-phase line is the residual current change; A is the allowable error of the amplitude change difference, which is set according to the protection sensitivity; P is the allowable error of the phase change difference, which is set according to the protection sensitivity; Calculate the residual current mutation value r of phases A, B, and C a 、r b 、r c , if the residual current mutation value of any phase exceeds the set mutation protection threshold, the circuit breaker protection will be performed; r a =|I a1 ×cos(θ a1 )-I a0 ×cos(θ a0 )| r b =|I b1 ×cos(θ b1 )-I b0 ×cos(θ b0 )| r c =|I c1 ×cos(θ c1 )-I c0 ×cos(θ c0 )| Among them, r a 、r b 、r c are the same-phase mutation values ​​of the residual current of phases A, B, and C from t0 to t1, I a1 ,I b1 ,I c1 are the current values ​​of phases A, B, and C at time t1, θ a1 ,θ b1 ,θ c1 are the phase angles of the current and the same-phase voltage of phase A, B, and C at time t1, I a0 ,I b0 ,I c0 are the current values ​​of phases A, B, and C at time t0, θ a0 ,θ b0 ,θ c0 are the phase angles of the current and the in-phase voltage of phases A, B, and C at time t0 respectively; When the amplitude change difference a>A or the phase change difference p>P, it is determined that the current of each phase of the three-phase line is load current fluctuation or does not reach the protection sensitivity, and the residual current mutation protection mechanism is not triggered.

6. A calculation system for three-phase residual current mutation protection, characterized in that: include: Module M1: collects electrical parameters of street light lines, calculates the vector sum of three-phase currents at the initial moment according to the electrical parameters of street light lines, and records the amplitude and phase of the vector sum of three-phase currents; Calculate the amplitude and phase of the residual current on the three-phase line at the same moment and record them; Module M2: Set the interval time, and after the interval time has passed, calculate the amplitude and phase of the three-phase current vector sum and the amplitude and phase of the three-phase line residual current at the interval time; Module M3: Calculate the amplitude change and phase change of the three-phase current vector sum between the initial moment and the interval moment, and the difference between the amplitude change and phase change of the residual current of the three-phase line; Module M4: Set the difference allowable error. When the above amplitude change and phase change differences are within the difference allowable error, analyze the sudden change of residual current on each phase line, and determine whether the residual current sudden change protection mechanism needs to be triggered according to the sudden change of residual current in each phase.

7. The calculation system for three-phase residual current sudden change protection according to claim 6, characterized in that: The module M1 collects electrical parameters of the street lamp line, including the residual current value of the three-phase line, the phase value of the residual current and voltage of the three-phase line, the current value of the three-phase line, and the phase value of the current and voltage of the three-phase line.

8. The calculation system for three-phase residual current sudden change protection according to claim 6, characterized in that: The module M2 is configured to set an interval time for periodic refresh, and collect, calculate and update data in real time.

9. The calculation system for three-phase residual current sudden change protection according to claim 6, characterized in that: The module M3 comprises: Calculate the difference a between the amplitude change of the three-phase current vector sum and the amplitude change of the three-phase line residual current from the initial time t0 to the interval time t1; a=|(A I1 -A I0 )-(A Ir1 -A Ir0 )| Calculate the difference p between the phase change of the three-phase current vector sum and the phase change of the three-phase line residual current from the initial time t0 to the interval time t1; p=|(P I1 -P I0 )-(P Ir1 -P Ir0 )| Among them, A I1 is the amplitude of the three-phase current vector sum at time t1, A I0 is the amplitude of the three-phase current vector sum at time t0; A Ir1 is the amplitude of the residual current on the three-phase line at time t1, A Ir0 is the amplitude of the residual current on the three-phase line at time t0; P I1 is the phase of the three-phase current vector sum at time t1, P I0 is the phase of the three-phase current vector sum at time t0; P Ir1 is the phase of the residual current on the three-phase line at time t1, P Ir0 It is the phase of the residual current on the three-phase line at time t0.

10. The calculation system for three-phase residual current sudden change protection according to claim 9, characterized in that: The module M4 comprises: When the amplitude change difference a≤A and the phase change difference p≤P, it is determined that the residual current change of the three-phase line is consistent with the three-phase line current change at the same time. At this moment, the current change of each phase of the three-phase line is the residual current change; A is the allowable error of the amplitude change difference, which is set according to the protection sensitivity; P is the allowable error of the phase change difference, which is set according to the protection sensitivity; Calculate the residual current mutation value r of phases A, B, and C a 、r b 、r c , if the residual current mutation value of any phase exceeds the set mutation protection threshold, the circuit breaker protection will be performed; r a =|I a1 ×cos(θ a1 )-I a0 ×cos(θ a0 )| r b =|I b1 ×cos(θ b1 )-I b0 ×cos(θ b0 )| r c =|I c1 ×cos(θ c1 )-I c0 ×cos(θ c0 )| Among them, r a 、r b 、r c are the same-phase mutation values ​​of the residual current of phases A, B, and C from t0 to t1, I a1 ,I b1 ,I c1 are the current values ​​of phases A, B, and C at time t1, θ a1 ,θ b1 ,θ c1 are the phase angles of the current and the same-phase voltage of phase A, B, and C at time t1, I a0 ,I b0 ,I c0 are the current values ​​of phases A, B, and C at time t0, θ a0 ,θ b0 ,θ c0 are the phase angles of the current and the in-phase voltage of phases A, B, and C at time t0 respectively; When the amplitude change difference a>A or the phase change difference p>P, it is determined that the current of each phase of the three-phase line is load current fluctuation or does not reach the protection sensitivity, and the residual current mutation protection mechanism is not triggered.

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