A three-phase voltage phase sequence memory and alarm device

Abstract

The invention discloses a three-phase voltage phase sequence memory and alarm device, comprising a differential circuit, a first, a second, a third, a fourth, and a fifth voltage comparator, a 50VDC, a working power supply, a phase sequence relay, a five-input AND gate circuit and an alarm. The input end of the differential circuit is connected to U A The output end is connected to the positive electrode of the fifth voltage comparator, the negative electrode of the fifth voltage comparator is grounded, and the input ends of the first voltage comparator are respectively connected to U A and U C , the input terminals of the second voltage comparator are connected to U B and U A , the input terminals of the third voltage comparator are respectively connected to U A and ground; the input terminals of the fourth voltage comparator are respectively connected to U A The present invention provides a plurality of comparators and differential circuits, and obtains a voltage output representing the phase sequence of the three-phase voltage according to the level principle of phase sequence change, thereby realizing the three-phase voltage phase sequence memory and change alarm, and the circuit of the present invention is simple and reliable.

Description

Technical Field

[0001] The invention relates to the technical field of three-phase voltage phase sequence memory, and in particular to a three-phase voltage phase sequence memory and alarm device. Background Art

[0002] At present, disconnectors and transformers are common primary equipment in substations, and electric mechanisms are generally used for opening and closing or gear adjustment operations. The motor is powered by three-phase voltage, and the phase sequence of the three-phase voltage is adjusted to achieve forward or reverse rotation of the motor, thereby achieving the opening and closing of the disconnector and the lifting and lowering of the main transformer gear through the connecting rod.

[0003] The three-phase power supply of the isolating switch is taken from the AC power panel cabinet in the main control room or protection room of the substation. The service life of the AC / DC system of the substation and the primary equipment such as the isolating switch are inconsistent. When the AC / DC system of the station is modified or encounters other situations, the phase sequence of the three-phase voltage may change, which will cause the isolating switch of the substation to be unable to operate or even damage the operating mechanism. There is no three-phase voltage phase sequence memory and alarm device in the prior art, which can determine and memorize the correct phase sequence during the debugging stage before the isolating switch is put into operation. When the power phase sequence changes after commissioning, it cannot be discovered and alarmed in time. Summary of the invention

[0004] The purpose of the present invention is to provide a three-phase voltage phase sequence memory and alarm device, which can realize the phase sequence collection, memory and alarm of the three-phase power supply of the isolating switch, and has a simple circuit and reliable performance.

[0005] The technical solution adopted by the present invention is:

[0006] A three-phase voltage phase sequence memory and alarm device comprises a differential circuit, a first, second, third, fourth and fifth voltage comparators, 50VDC, a working power supply, a phase sequence relay, a five-input AND gate circuit and an alarm, wherein the input end of the differential circuit is connected to UA, the output end is connected to the positive electrode of the fifth voltage comparator, the negative electrode of the fifth voltage comparator is grounded, the input end of the first voltage comparator is respectively connected to UA and UC, the input end of the second voltage comparator is respectively connected to UB and UA, the input end of the third voltage comparator is respectively connected to UA and ground; the input end of the fourth voltage comparator is respectively connected to UA and 50VDC, the working power supply supplies power to the above-mentioned original components respectively, the output ends of the first, second, third, fourth and fifth voltage comparators are respectively connected to the input ends of the five-input AND gate circuit, the output end of the five-input AND gate circuit is connected to the control input end of the phase sequence relay, the output end of the phase sequence relay controls the control input end of the alarm, wherein UA, UB and UC are respectively the three-phase voltages of the three-phase motor power supply.

[0007] It also includes a phase sequence reset circuit, which includes an alarm holding relay, a single-pole double-throw switch and a reset button. The first moving contact of the single-pole double-throw switch is connected to one end of the normally open contact of the phase sequence relay, the second moving contact is connected to one end of the normally open and closed point of the phase sequence relay, the static contact is connected in series with the alarm holding relay coil and the reset switch in sequence, one end of the normally open contact of the alarm holding relay is respectively connected to the other end of the normally open contact and the other end of the normally open and closed point of the phase sequence relay, and the other end of the normally open contact is connected to the static contact.

[0008] The differential circuit adopts the chip LM393.

[0009] The chip is LM393.

[0010] The first, second, third and fourth voltage comparator integrated chips can be LM339.

[0011] The four-input AND gate chip is 74LS21.

[0012] The present invention achieves a voltage output representing the phase sequence of the three-phase voltage by setting a plurality of comparators and differential circuits according to the level principle of phase sequence change, thereby realizing three-phase voltage phase sequence memory and change alarm, and the circuit of the present invention is simple and the performance is stable and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 It is the circuit principle diagram of the present invention;

[0015] Figure 2 This is a waveform diagram of the three-phase voltage of the present invention when it is a positive sequence;

[0016] Figure 3 This is a waveform diagram of the three-phase voltage of the present invention when it is a negative sequence;

[0017] Figure 4 This is the phase sequence reset circuit described in the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] like Figure 1 As shown, the present invention includes a three-phase voltage phase sequence memory and alarm device, which is characterized by: comprising a differential circuit, a first, second, third, fourth, and fifth voltage comparators, 50VDC, a working power supply, a phase sequence relay, a five-input AND gate circuit and an alarm, wherein the input end of the differential circuit is connected to U A The output end is connected to the positive electrode of the fifth voltage comparator, the negative electrode of the fifth voltage comparator is grounded, and the input ends of the first voltage comparator are respectively connected to U A and U C , the input terminals of the second voltage comparator are connected to U B and U A , the input terminals of the third voltage comparator are respectively connected to U A and ground; the input terminals of the fourth voltage comparator are respectively connected to U A and 50VDC, the working power supply is used to supply power to each of the above components respectively, the output ends of the first, second, third, fourth and fifth voltage comparators are respectively connected to the input ends of the five-input AND gate circuit (the letter & in the figure), the output end of the five-input AND gate circuit is connected to the control input end of the phase sequence relay, and the output end of the phase sequence relay controls the control input end of the alarm, wherein U A , U B , U C They are the three-phase voltages of the three-phase motor power supply.

[0020] The U A The voltage obtained after the differential circuit is recorded as U A1 , the outputs of the first, second, third, fourth, and fifth voltage comparators are respectively recorded as V 1. V 2. V 3. V 4. V 5. The output of the five-input AND gate circuit is V 6, then when both UA < U C (get V 1) U A > U B (get V 2) U A >0 (get V 3) U A <50 (get V 4) U A1 <0 (get V 5) When V 6 is high level, otherwise it is low level.

[0021] Within one cycle of the three-phase power supply, it can be divided into zones ① to ⑥. In each zone, the order of the three-phase voltage amplitudes is fixed and can be used as a basis for phase sequence judgment.

[0022] When the voltage amplitudes of any two phases are equal, the voltage amplitude is about 155V. No matter how the three-phase voltage fluctuates, the reference phase zero crossing point will not fluctuate. Therefore, you only need to select the vicinity of the reference phase zero crossing point to avoid being affected by voltage fluctuations.

[0023] like Figure 2 and Figure 3 As shown, the three-phase motor A phase voltage is selected as the reference phase. U A After the differential circuit, the voltage is obtained U A1 , from the differential circuit we know: i C = i R = C *(d U A / dt)=- U A1 / R

[0024] Thus: U A1 =- RC *(d U A / dt), where R is the resistance of the resistor, C is the capacitance of the capacitor, and i is the current value.

[0025] Satisfy at the same time U A < U C (getV 1) U A > U B (get V 2) U A >0 (get V 3) U A <50 (get V 4) U A1 <0 (get V 5) When V 6 is high level, otherwise it is low level. Figure 2 and Figure 3 It can be seen that only when the three-phase voltage is in positive sequence, each cycle exists V 6 is high level, so V 6 As the marking voltage of the positive phase sequence of voltage, the phase sequence can be memorized, and then according to V By observing the level change of 6, we can know whether the phase sequence has changed, and then realize the alarm of phase sequence change.

[0026] To implement the above technical solution, the differential circuit uses a chip LM393. The chip LM393 has two comparator circuits. The first, second, third and fourth voltage comparator integrated chips can be chip LM339, and the chip LM339 is integrated with a circuit comparison circuit. The four-input AND gate chip is 74LS21. When used specifically, a reasonable selection can be made according to actual needs.

[0027] When the device is actually used, the three-phase voltage phase sequence memory and alarm device is installed inside the mechanism box of the disconnector or transformer and other equipment. During the debugging stage before the disconnector is put into operation, the correct three-phase power phase sequence is determined as follows: the disconnector has a closed position and an open position. When debugging the disconnector, the moving contact is manually moved to the middle position, which is neither closed nor open. Press the closing button to observe whether the moving contact of the disconnector moves to the closed position. If not, adjust the power phase sequence; if so, it is the correct phase sequence. After the manual paddle (i.e. knife) is positioned, the phase sequence relay has two nodes, one normally open node, i.e., the normally open contact, and one normally closed node, i.e., the normally closed contact. Regardless of whether the phase sequence relay is energized or not, the two nodes cannot be turned on at the same time. At this time, the phase sequence relay should have only one pair of nodes turned on, and the node that is not turned on is selected as the phase sequence abnormality alarm. If the phase sequence of the three-phase power supply changes after the disconnector is in operation, the phase abnormality alarm node is turned on, which can drive an audible and visual alarm or other forms of alarm.

[0028] In actual use, such as Figure 4As shown, a phase sequence reset circuit is also included, and the phase sequence reset circuit includes an alarm holding relay, a single-pole double-throw switch and a reset button. The first moving contact of the single-pole double-throw switch is connected to one end of the normally open contact of the phase sequence relay, the second moving contact is connected to one end of the normally open and closed point of the phase sequence relay, and the static contact is connected in series with the alarm holding relay coil and the reset switch in sequence. One end of the normally open contact of the alarm holding relay is respectively connected to the other end of the normally open contact and the other end of the normally open and closed point of the phase sequence relay, and the other end of the normally open contact is connected to the static contact.

[0029] After receiving the alarm, the maintenance personnel adjust the phase sequence and press the reset button. The alarm should no longer sound. If the alarm still sounds, continue to adjust the phase sequence until the alarm no longer sounds after reset.

[0030] For example: After actual debugging of a substation disconnector, the correct wiring method of the power supply is determined (assuming that the negative sequence is the correct wiring). Then the power supply is connected to the three-phase voltage phase memory and alarm device as shown in the figure, and the voltage of the manual paddle position 1 and position 2 is measured. At this time, position 2 should be positive, and the manual paddle is moved to position 1.

[0031] During operation, if the voltage phase sequence changes, the power phase sequence changes from negative sequence to positive sequence, relay XXJ operates, XXJ-1 is turned on, position 1 of the manual paddle is positively charged, the alarm holding relay GJBJ operates, and its normally open node GJBJ-1 is turned on. After that, relay GJBJ continues to operate through its normally open node to generate a phase sequence abnormality alarm.

[0032] After receiving the alarm, the maintenance personnel adjusted the power connection. After the adjustment, the power phase sequence changed from positive to negative, the relay XXJ was reset, and its normally open contact XXJ-1 was disconnected. After the maintenance personnel pressed the reset button, the relay GJBJ circuit was disconnected and then reset, GJBJ-1 was disconnected, the manual paddle position 1 was not energized, the phase sequence abnormality alarm was reset, and the maintenance work was completed.

[0033] In the description of the present invention, it should be noted that directional words, such as the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like, indicating directions and positional relationships based on the directions or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and cannot be understood as limiting the specific protection scope of the present invention.

[0034] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] Note that the above are only preferred embodiments of the present invention and the principles of the application technology. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention is described in more detail through the above embodiments, the present invention is not limited to the specific embodiments described herein, and may include more other effective embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A three-phase voltage phase sequence memory and alarm device, characterized in that: It includes a differential circuit, a first, second, third, fourth, and fifth voltage comparators, a 50VDC, a working power supply, a phase sequence relay, a five-input AND gate circuit, and an alarm. The input end of the differential circuit is connected to U A The output end is connected to the positive electrode of the fifth voltage comparator, the negative electrode of the fifth voltage comparator is grounded, and the input ends of the first voltage comparator are respectively connected to U A and U C , the input terminals of the second voltage comparator are connected to U B and U A , the input terminals of the third voltage comparator are respectively connected to U A and ground; the input terminals of the fourth voltage comparator are respectively connected to U A and 50VDC, the working power supply is used to supply power to the above components respectively, the output ends of the first, second, third, fourth and fifth voltage comparators are respectively connected to the input ends of the five-input AND gate circuit, the output end of the five-input AND gate circuit is connected to the control input end of the phase sequence relay, the output end of the phase sequence relay controls the control input end of the alarm, wherein U A , U B , U C They are the three-phase voltages of the three-phase motor power supply.

2. The three-phase voltage phase sequence memory and alarm device according to claim 1 is characterized in that: It also includes a phase sequence reset circuit, which includes an alarm holding relay, a single-pole double-throw switch and a reset button. The first moving contact of the single-pole double-throw switch is connected to one end of the normally open contact of the phase sequence relay, the second moving contact is connected to one end of the normally open and closed point of the phase sequence relay, the static contact is connected in series with the alarm holding relay coil and the reset switch in sequence, one end of the normally open contact of the alarm holding relay is respectively connected to the other end of the normally open contact and the other end of the normally open and closed point of the phase sequence relay, and the other end of the normally open contact is connected to the static contact.

3. The three-phase voltage phase sequence memory and alarm device according to claim 1 is characterized in that: The differential circuit adopts the chip LM393.

4. The three-phase voltage phase sequence memory and alarm device according to claim 3 is characterized in that: The first, second, third and fourth voltage comparator integrated chips are chips LM339.

5. The three-phase voltage phase sequence memory and alarm device according to claim 1 is characterized in that: The chip of the five-input AND gate circuit is 74LS21.

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