Low-voltage three-phase four-wire system open-phase detection method
By collecting and analyzing the voltage and current data of low-voltage three-phase four-wire circuits and calculating the phase loss value, the problem of difficult phase loss is solved, and timely alarm and equipment protection is achieved.
Patent Information
- Application Number
- CN202411290062.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-09-13
- Filing Date
- 2024-09-14
- Publication Date
- 2024-12-17
AI Technical Summary
In low-voltage three-phase four-wire circuits, faults and phase defects are difficult to identify in a timely manner, resulting in an increase in the risk of equipment failure.
By collecting three-phase voltage, current, neutral line voltage and current, calculate the voltage, loss of voltage and current situations at neutral points, use specific conditions and formulas to calculate the phase loss value, and when the number of consecutive times reaches a certain threshold value, it is possible to achieve a certain threshold value. Issue a missing phase alarm.
It realizes timely identification and alarm of fault phases, reduces misjudgment, and protects the safety of electrical equipment.
Abstract
Description
Technical Field
[0001] The invention relates to the technology of power system, in particular to the technology of a phase loss detection method of a low-voltage three-phase four-wire system. Background Art
[0002] The three-phase four-wire low-voltage lines mostly supply power to user-side equipment. The operating environment of the power-consuming equipment is complex and prone to short circuit and disconnection faults. If the power supply line cannot be cut off in time when a fault occurs, it is easy to cause the power-consuming equipment to fail. When the three-phase power supply line is disconnected, or the line or equipment is modified, it is easy to cause a phase loss fault. If the fault phase loss is not identified in time, it is easy to cause equipment failure. Summary of the invention
[0003] In view of the defects existing in the above-mentioned prior art, the technical problem to be solved by the present invention is to provide a phase loss detection method for a low-voltage three-phase four-wire system which can promptly identify the faulty phase loss, thereby promptly issuing a phase loss alarm notification to cut off the abnormal line.
[0004] In order to solve the above technical problems, the present invention provides a low-voltage three-phase four-wire phase loss detection method, which is characterized by the following specific steps:
[0005] 1) Collect the three-phase voltages Ua, Ub, Uc, and the three-phase currents Ia, Ib, Ic of the three-phase four-wire low-voltage line, and obtain the neutral line voltage U0 and neutral line current I0 of the three-phase four-wire low-voltage line;
[0006] 2) Set the pressure coefficient ku, pressure loss coefficient ks, flow coefficient ki, delayed alarm time T, and set the initial values of the pressure value Uex and the pressure loss value Usy to 0, and set the value of the delay number N to: N = int (T / speriod);
[0007] In the formula, speriod is the calculation period of the missing phase value, and int is the rounding down function;
[0008] 3) Calculate the pressure value Uex and the pressure-deficient value Usy;
[0009] If condition 1 or condition 2 is true, then set Uex = 1, otherwise set Uex = 0;
[0010] Condition 1:
[0011] If the current Uex==0, and (Ua>ku×Un||Ub>ku×Un||Uc>ku×Un);
[0012] Condition 2:
[0013] If the current Uex==1, and (Ua>0.975×ku×Un||Ub>0.975×ku×Un
[0014] ||Uc>0.975×ku×Un);
[0015] If condition 3 or condition 4 is met, then set Usy = 1, otherwise set Usy = 0;
[0016] Condition 3:
[0017] If the current Usy==0, and (Ua<ks×Un&&Ub> ks×Un&&Uc>ks×Un);
[0018] Condition 4:
[0019] If the current Usy==1, and (Ua<ks×Un&&Ub> ks×Un&&Uc>ks×Un);
[0020] Where Un is the rated voltage of the three-phase four-wire low-voltage line, && is the logical AND operator, and ‖ is the logical OR operator;
[0021] 4) Calculate the neutral point value Is0. If condition 5 is met, set Is0 = 0, otherwise set Is0 = 1;
[0022] Condition 5:
[0023] U0>ks×Un||I0>3×ki×In||I0>ki×Vec(Ia+Ib+Ic);
[0024] In the formula, In is the rated current of the three-phase four-wire low-voltage line; Vec (Ia + Ib + Ic) is the amplitude of the vector sum of the three-phase currents of the three-phase four-wire low-voltage line;
[0025] 5) Calculate the missing phase value F. The specific calculation formula is:
[0026] F = Uex × Usy × Is0;
[0027] 6) If F == 1 for N consecutive times, a phase loss alarm will be issued.
[0028] The phase loss detection method for a low-voltage three-phase four-wire system provided by the present invention performs phase loss identification based on the collected three-phase voltage, three-phase current, neutral line voltage, and neutral line current, and judges whether there is pressure, no pressure, and whether there is voltage and current at the neutral point. The faulty phase loss can be identified in time, so that a phase loss alarm can be issued in time to cut off the abnormal line, thereby reducing misjudgment and protecting the safety of electrical equipment on the line. DETAILED DESCRIPTION
[0029] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments, but this embodiment is not intended to limit the present invention. All similar structures and similar variations of the present invention should be included in the protection scope of the present invention. The commas in the present invention represent the relationship of and, and the English letters in the present invention are case-sensitive.
[0030] An embodiment of the present invention provides a method for detecting phase loss in a low-voltage three-phase four-wire system, characterized in that the specific steps are as follows:
[0031] 1) Collect the three-phase voltages Ua, Ub, Uc, and the three-phase currents Ia, Ib, Ic of the three-phase four-wire low-voltage line, and obtain the neutral line voltage U0 and neutral line current I0 of the three-phase four-wire low-voltage line;
[0032] 2) Set the pressure coefficient ku, pressure loss coefficient ks, flow coefficient ki, delayed alarm time T, and set the initial values of the pressure value Uex and the pressure loss value Usy to 0, and set the value of the delay number N to: N = int (T / speriod);
[0033] Where, speriod is the calculation period of the missing phase value, int is the rounding function, the typical value of speriod is 0.1ms, the typical value of ku is 0.7, the typical value of ks is 0.0625, the typical value of ki is 0.05, and the typical value of T is 100ms~1000s;
[0034] 3) Calculate the pressure value Uex and the pressure-deficient value Usy;
[0035] If condition 1 or condition 2 is true, then set Uex = 1, otherwise set Uex = 0;
[0036] Condition 1:
[0037] If the current Uex==0, and (Ua>ku×Un||Ub>ku×Un||Uc>ku×Un);
[0038] Condition 2:
[0039] If the current Uex==1, and (Ua>0.975×ku×Un||Ub>0.975×ku×Un
[0040] ||Uc>0.975×ku×Un);
[0041] If condition 3 or condition 4 is met, then set Usy = 1, otherwise set Usy = 0;
[0042] Condition 3:
[0043] If the current Usy==0, and (Ua<ks×Un&&Ub> ks×Un&&Uc>ks×Un);
[0044] Condition 4:
[0045] If the current Usy==1, and (Ua<ks×Un&&Ub> ks×Un&&Uc>ks×Un);
[0046] Where Un is the rated voltage of the three-phase four-wire low-voltage line, && is the logical AND operator, and ‖ is the logical OR operator;
[0047] 4) Calculate the neutral point value Is0. If condition 5 is met, set Is0 = 0, otherwise set Is0 = 1;
[0048] Condition 5:
[0049] U0>ks×Un||I0>3×ki×In||I0>ki×Vec(Ia+Ib+Ic);
[0050] In the formula, In is the rated current of the three-phase four-wire low-voltage line; Vec (Ia + Ib + Ic) is the amplitude of the vector sum of the three-phase currents of the three-phase four-wire low-voltage line;
[0051] 5) Calculate the missing phase value F. The specific calculation formula is:
[0052] F = Uex × Usy × Is0;
[0053] 6) If F == 1 for N consecutive times, a phase loss alarm will be issued.
Claims
1. A method for detecting phase loss in a low-voltage three-phase four-wire system, characterized in that: The specific steps are as follows: 1) Collect the three-phase voltages Ua, Ub, Uc, and the three-phase currents Ia, Ib, Ic of the three-phase four-wire low-voltage line, and obtain the neutral line voltage U0 and neutral line current I0 of the three-phase four-wire low-voltage line; 2) Set the pressure coefficient ku, pressure loss coefficient ks, flow coefficient ki, delayed alarm time T, and set the initial values of the pressure value Uex and the pressure loss value Usy to 0, and set the value of the delay number N to: N = int (T / speriod); In the formula, speriod is the calculation period of the missing phase value, and int is the rounding down function; 3) Calculate the pressure value Uex and the pressure-deficient value Usy; If condition 1 or condition 2 is true, then set Uex = 1, otherwise set Uex = 0; Condition 1: If the current Uex==0, and (Ua>ku×Un||Ub>ku×Un||Uc>ku×Un); Condition 2: If the current Uex==1, and (Ua>0.975×ku×Un||Ub>0.975×ku×Un||Uc>0.975×ku×Un); If condition 3 or condition 4 is met, then set Usy = 1, otherwise set Usy = 0; Condition 3: If the current Usy==0, and (Ua<ks×Un&&Ub> ks×Un&&Uc>ks×Un); Condition 4: If the current Usy==1, and (Ua<ks×Un&&Ub> ks×Un&&Uc>ks×Un); Where Un is the rated voltage of the three-phase four-wire low-voltage line, && is the logical AND operator, and ‖ is the logical OR operator; 4) Calculate the neutral point value Is0. If condition 5 is met, set Is0 = 0, otherwise set Is0 = 1; Condition 5: U0>ks×Un||I0>3×ki×In||I0>ki×Vec(Ia+Ib+Ic); In the formula is the rated current of the three-phase four-wire low-voltage line; Vec(Ia+Ib+Ic) is the amplitude of the vector sum of the three-phase currents of the three-phase four-wire low-voltage line; 5) Calculate the missing phase value F. The specific calculation formula is: F = Uex × Usy × Is0; 6) If F == 1 for N consecutive times, a phase loss alarm will be issued.