CN110086155B - Self-triggering three-phase quick harmonic elimination device - Google Patents
Self-triggering three-phase quick harmonic elimination device Download PDFInfo
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- CN110086155B CN110086155B CN201910499494.5A CN201910499494A CN110086155B CN 110086155 B CN110086155 B CN 110086155B CN 201910499494 A CN201910499494 A CN 201910499494A CN 110086155 B CN110086155 B CN 110086155B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
- H02H7/05—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers for capacitive voltage transformers, e.g. against resonant conditions
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/005—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection avoiding undesired transient conditions
- H02H9/007—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection avoiding undesired transient conditions avoiding or damping oscillations, e.g. fenoresonance or travelling waves
Abstract
The invention discloses a self-triggering three-phase rapid harmonic elimination device which comprises a self-triggering circuit, a three-phase harmonic elimination circuit and a monostable delay circuit, wherein the self-triggering circuit is connected between a neutral point of a three-phase voltage transformer and the ground in series, the three-phase harmonic elimination circuit is connected in a phase line of the three-phase voltage transformer in series, and the monostable delay circuit is used for triggering the three-phase harmonic elimination circuit to act to eliminate harmonic under the action of the self-triggering circuit and limits one-time harmonic elimination time. The method does not need Fourier calculation, can quickly put in resonance elimination when resonance occurs, can avoid influencing the voltage measurement precision of the system on the basis of ensuring that the resonance is reliably eliminated once, and improves the running stability of the system.
Description
Technical Field
The invention relates to the technical field of power quality of a power distribution network, in particular to a self-triggering three-phase quick harmonic elimination device.
Background
In an electric power system provided with an electromagnetic voltage transformer (PT), the PT is an iron core inductive element, and if there is some large disturbance or operation (such as single-phase earth fault disappearance or no-load bus closing), the iron core of the PT may be saturated, so as to form a special single-phase or three-phase resonant loop with the line and the earth capacitance of the equipment, and to excite an overvoltage with continuously higher amplitude, that is, a ferromagnetic resonant overvoltage. Under the coordination of different parameters, the system can generate fundamental frequency resonance, high frequency resonance and frequency division resonance. In addition, in a system without a neutral point grounded, when the grounding capacitance current of the system is large, a primary high-voltage fuse fusing accident of the voltage transformer is easy to occur at the moment of single-phase grounding fault recovery. Therefore, eliminating resonance is the most direct solution to avoid the above-mentioned accidents.
Currently, conventional resonance elimination devices are mainly classified into two types, one is a secondary resonance elimination device, and the other is a primary resonance elimination device. The secondary harmonic elimination device is connected to the secondary opening angle side of the PT, the PT opening angle voltage is sampled and Fourier calculation is carried out, the PT opening angle voltage is compared with a set value according to the numerical values of components such as fundamental wave, 1/2 frequency division, 1/3 frequency division, 1/4 frequency division, 3 frequency multiplication and the like, the resonance is judged when the PT opening angle is out of limit, then the PT opening angle is short-circuited in a short time through a relay, the resonance is equivalent to the fact that large damping is connected in series in a resonance loop, resonance conditions are destroyed, and harmonic elimination is achieved; however, this method has the following drawbacks: 1) when power frequency ferromagnetic resonance and single-phase earth faults occur, the rising amplitude of PT opening angle voltage is close, the frequency characteristics are close, and the secondary resonance elimination devices are difficult to separate; 2) the Fourier calculation delay time is long, generally more than 200ms, and the problem that the second harmonic elimination device is difficult to solve is solved. The primary resonance eliminator is a nonlinear resistor with a high resistance value connected between a PT primary side neutral point and the ground, so that most ferromagnetic resonance can be eliminated, but the primary resonance eliminator is permanently connected with the PT neutral point, so that the voltage measurement precision is influenced, the problem of raising the PT tail end voltage exists, even the tail end insulation breakdown of semi-insulating PT is caused, and a serious potential safety hazard is formed; and the other harmonic eliminator can not solve the problem of interphase resonance. Therefore, it is necessary to develop a resonance elimination device which is reliable in resonance elimination and does not affect the voltage measurement accuracy of the system.
Disclosure of Invention
The invention provides a self-triggering three-phase quick resonance elimination device, which avoids the influence on the system voltage measurement precision and improves the system operation stability on the basis of reliably eliminating resonance.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows.
A self-triggering three-phase rapid harmonic elimination device comprises a self-triggering circuit, a three-phase harmonic elimination circuit and a monostable time delay circuit, wherein the self-triggering circuit is connected between a neutral point of a three-phase voltage transformer and the ground in series; the monostable delay circuit is connected between the self-triggering circuit and the three-phase harmonic elimination circuit and used for triggering the three-phase harmonic elimination circuit to act for harmonic elimination under the action of the self-triggering circuit and limiting one-time harmonic elimination time.
The self-triggering three-phase rapid harmonic elimination device comprises a self-triggering circuit, a harmonic elimination circuit and a harmonic elimination circuit, wherein the self-triggering circuit comprises a sampling resistor, a self-triggering thyristor and a high-frequency normally-open reed switch relay, and the sampling resistor is connected between a neutral point of a three-phase voltage transformer and the ground in series; the self-triggering thyristor and the coil of the high-frequency normally-open reed switch relay are connected in series and then connected in parallel to two ends of the sampling resistor, and the normally-open contact of the high-frequency normally-open reed switch relay is connected with the input end of the monostable delay circuit.
According to the self-triggering three-phase quick harmonic elimination device, the resistance value of the sampling resistor is 1-10 omega.
The monostable delay circuit comprises a monostable trigger chip, a pulse width control capacitor and a pulse width control resistor, wherein the pulse width control capacitor and the pulse width control resistor are respectively connected with the input end of the monostable trigger chip, and the input end of the monostable trigger chip is also connected with a normally open contact of a high-frequency normally open reed switch relay; and the output end of the monostable trigger chip is connected with the power supply end of the three-phase harmonic elimination circuit.
The three-phase harmonic elimination circuit comprises three nonlinear resistors and three high-frequency normally-closed reed switch relays, the nonlinear resistors are connected in series in a three-phase voltage transformer phase line, normally-closed contacts of the high-frequency normally-closed reed switch relays are connected to two ends of the nonlinear resistors in parallel, one end of a coil of each high-frequency normally-closed reed switch relay is connected with the output end of a monostable trigger chip, and the other end of each high-frequency normally-closed reed switch relay is connected with a direct-current power supply Vc.
Due to the adoption of the technical scheme, the technical progress of the invention is as follows.
The invention is based on the necessary condition of ferromagnetic resonance generation of magnetic saturation as a criterion, adopts a pure hardware circuit for automatic triggering, and does not influence the measurement precision of PT in the normal operation process because the resistance value of the sampling resistor is smaller; when resonance occurs, the starting delay from the out-of-limit of the instantaneous value of the saturation current to the harmonic elimination action is about 1ms, the action is very fast, and the action delay problem cannot occur; in the harmonic elimination process, the three-phase PT simultaneously damps and eliminates harmonic, the time of strong damping input is determined by the pulse width output by the monostable trigger circuit, namely, the single harmonic elimination time can be formulated according to the system operation characteristics, the phenomena of misjudgment and misjudgment are avoided, various ferromagnetic resonance phenomena including single-phase, two-phase, three-phase and interphase resonance can be effectively inhibited and eliminated, the success of one-time harmonic elimination can be ensured, and the reliable guarantee is provided for the stable operation of the system.
Drawings
FIG. 1 is an electrical schematic of the present invention;
fig. 2 is a waveform diagram of the detuning action of the present invention.
Wherein: the circuit comprises a PTa.A phase voltage transformer, a PTb.B phase voltage transformer, a PTc.C phase voltage transformer, a Rxa.A phase nonlinear resistor, a Rxb.B phase nonlinear resistor, a Rxc.C phase nonlinear resistor, a Jma.A phase high-frequency normally closed reed switch relay, a Jmb.B phase high-frequency normally closed reed switch relay, a Jmc.C phase high-frequency normally closed reed switch relay, an Rs. sampling resistor, an SCR self-triggered thyristor, a Jm0 high-frequency normally open reed switch relay, a MC. monostable trigger chip, a Ct. pulse width control capacitor and a Rt. pulse width control resistor.
Detailed Description
The invention will be described in further detail below with reference to the figures and specific examples.
A self-triggering three-phase rapid harmonic elimination device comprises a self-triggering circuit, a three-phase harmonic elimination circuit and a monostable delay circuit, wherein the self-triggering circuit is connected between a neutral point of a three-phase voltage transformer and the ground in series, the three-phase harmonic elimination circuit is connected in series in a phase line of the three-phase voltage transformer, and the monostable delay circuit is connected between the self-triggering circuit and the three-phase harmonic elimination circuit and used for triggering the three-phase harmonic elimination circuit to act to eliminate harmonic under the action of the self-triggering circuit and limiting one-time harmonic elimination time.
The circuit diagram of the self-triggering circuit is shown in fig. 1 and comprises a sampling resistor Rs, a self-triggering thyristor SCR and a high-frequency normally-open reed switch relay Jm0. The sampling resistor Rs is connected between the neutral point of the three-phase voltage transformer and the ground in series, the resistance value is 1-10 omega, the mounting position of the sampling resistor Rs in a circuit is the same as that of a conventional primary harmonic eliminator, but the resistance value is 5 orders of magnitude smaller than that of the primary harmonic eliminator, so that the influence of the Rs on PT secondary output precision can be completely ignored when a system operates normally; the self-triggering thyristor SCR and the coils of the high-frequency normally-open reed switch relay Jm0 are connected in series and then connected in parallel at two ends of a sampling resistor Rs, and the normally-open contact of the high-frequency normally-open reed switch relay Jm0 is connected with the input end of the monostable delay circuit.
The monostable delay circuit is shown in fig. 1, and comprises a monostable trigger chip MC, a pulse width control capacitor Ct and a pulse width control resistor Rt, wherein the pulse width control capacitor Ct and the pulse width control resistor Rt are respectively connected with the input end of the monostable trigger chip MC, the input end of the monostable trigger chip MC is also connected with a normally open contact of a high-frequency normally open reed switch relay Jm0, and the output end of the monostable trigger chip MC is connected with a power supply end of a three-phase harmonic elimination circuit.
The circuit diagram of the three-phase resonance elimination circuit is shown in fig. 1, and the three-phase resonance elimination circuit comprises three nonlinear resistors Rxa, Rxb and Rxc and three high-frequency normally-closed reed switch relays Jma, Jmb and Jmc, wherein the nonlinear resistors are connected in series in a three-phase voltage transformer phase line, normally-closed contacts of the high-frequency normally-closed reed switch relays are connected to two ends of the nonlinear resistors in parallel, one end of a coil of each high-frequency normally-closed reed switch relay is connected with the output end of a monostable trigger chip MC, and the other end of the coil is connected with a direct-current power supply Vc.
The working principle of the present invention is as follows.
Under the normal condition, the three-phase voltage transformers PTa, PTb and PTc are in a high-impedance state, the current flowing through each phase PT is very small and is less than 10mA, the current flowing through the sampling resistor Rs is almost 0 at the moment, the voltage drop of the sampling resistor Rs is not enough to trigger the self-triggering thyristor SCR, therefore, the monostable triggering chip MC has no output, the high-frequency normally-closed reed switch relays Jma, Jmb and Jmc are normally closed, and the three nonlinear resistors Rxa, Rxb and Rxc are respectively in short circuit. At the moment, only the sampling resistor Rs plays a role in a primary loop of the three-phase voltage transformer of the system, and the influence of the sampling resistor Rs on the secondary side output voltage precision of the three-phase voltage transformer side can be completely ignored due to the fact that the resistance value of the sampling resistor Rs is very small.
When ferromagnetic resonance occurs in a system, a three-phase voltage transformer PT enters a saturated state, the saturation current is more than 100 times of the normal current, at the moment, the current flowing through a sampling resistor Rs rapidly rises, the voltage drop at two ends of the sampling resistor Rs rapidly rises, a self-triggering thyristor SCR is triggered and conducted, a coil of a high-frequency normally-open reed switch Jm0 is electrified, a normally-open contact of the high-frequency normally-open reed switch Jm0 is attracted, a monostable triggering chip is triggered to work, the monostable triggering chip MC outputs a pulse signal, coils of the high-frequency normally-closed reed switch Jma, Jmb and Jmc are electrified to act, the normally-closed contact is opened, three nonlinear resistors Rxa, Rxb and Rxc are respectively put into an earth circuit of the three-phase voltage transformer, strong damping is formed, and single-phase, two-phase and three-phase ferromagnetic resonance is effectively inhibited and eliminated.
The input time of the nonlinear resistor is determined by the pulse width of an output signal of the monostable trigger chip MC, the pulse width is equal to the product of a pulse width control capacitor Ct and a pulse width control resistor Rt, generally, the Ct value range is 1-100 uF, and the Rt value range is 1-100 k omega.
In the invention, no phase angle difference exists between the voltage on the sampling resistor Rs and the saturation current of the three-phase voltage transformer PT, namely no time delay exists; the time delay of SCR triggering conduction of the self-triggering thyristor is generally less than 5 us; the output delay of the monostable trigger chip is ns level; the action time of the reed switch relay is not more than 1 ms; the links are accumulated, the total time delay is about 1ms from the limit-exceeding of the instantaneous value of the saturation current to the starting of the harmonic elimination action, and the harmonic elimination device does not need Fourier calculation, can quickly put into harmonic elimination when resonance occurs, and is two orders of magnitude faster than the conventional secondary harmonic elimination device. The action oscillogram in the harmonic elimination process is shown in fig. 2, wherein t2-t1 is the delay time from the instant current of a three-phase voltage transformer PT to the start of the harmonic elimination action, and is generally not more than 1 ms; in the figure, t3-t2 are durations that nonlinear resistors Rxa, Rxb and Rxc are respectively put into a ground circuit of a three-phase voltage transformer PT, namely a single harmonic elimination duration, which is generally tens to hundreds of ms, and can ensure that one-time harmonic elimination is completed.
The invention takes magnetic saturation as a criterion, and the primary sides of the three-phase voltage transformers are respectively connected with a nonlinear resistor in series in a ground circuit, so that the phenomena of misjudgment and misjudgment can not occur in the harmonic elimination process; can eliminate various ferromagnetic resonance of single phase, two phase, three phase and interphase, etc.
When the harmonic elimination action is not carried out, the series impedance (namely sampling resistance) of the PT loop of the three-phase voltage transformer is 5 orders of magnitude smaller than that of the conventional primary harmonic eliminator, and is about 1/10 of the PT impedance of the three-phase voltage transformer6Therefore, the measuring precision of the three-phase voltage transformer PT cannot be influenced.
Claims (4)
1. The utility model provides a self-triggering three-phase fast harmonic elimination device which characterized in that: the three-phase harmonic elimination circuit comprises a self-triggering circuit connected between a neutral point of the three-phase voltage transformer and the ground in series, a three-phase harmonic elimination circuit connected in series in a phase line of the three-phase voltage transformer, and a monostable delay circuit for triggering the three-phase harmonic elimination circuit to act; the monostable delay circuit is connected between the self-triggering circuit and the three-phase harmonic elimination circuit and is used for triggering the three-phase harmonic elimination circuit to act for harmonic elimination under the action of the self-triggering circuit and limiting one-time harmonic elimination time; the self-triggering circuit comprises a sampling resistor (Rs), a self-triggering thyristor (SCR) and a high-frequency normally-open reed switch relay (Jm0), and the sampling resistor (Rs) is connected between the neutral point of the three-phase voltage transformer and the ground in series; the coils of the self-triggering thyristor (SCR) and the high-frequency normally-open reed switch relay (Jm0) are connected in series and then connected in parallel to two ends of the sampling resistor (Rs), and the normally-open contact of the high-frequency normally-open reed switch relay (Jm0) is connected with the input end of the monostable delay circuit.
2. The self-triggering three-phase fast harmonic elimination device according to claim 1, wherein: the resistance value of the sampling resistor (Rs) is 1-10 omega.
3. The self-triggering three-phase fast harmonic elimination device according to claim 2, wherein: the monostable delay circuit comprises a monostable trigger chip (MC), a pulse width control capacitor (Ct) and a pulse width control resistor (Rt), wherein the pulse width control capacitor (Ct) and the pulse width control resistor (Rt) are respectively connected with the input end of the monostable trigger chip (MC), and the input end of the monostable trigger chip (MC) is also connected with a normally open contact of a high-frequency normally open reed switch relay (Jm 0); and the output end of the monostable trigger chip (MC) is connected with the power supply end of the three-phase harmonic elimination circuit.
4. A self-triggering three-phase fast harmonic elimination apparatus according to claim 3, wherein: the three-phase harmonic elimination circuit comprises three nonlinear resistors and three high-frequency normally closed reed switch relays, wherein the nonlinear resistors are connected in series in a phase line of a three-phase voltage transformer, normally closed contacts of the high-frequency normally closed reed switch relays are connected to two ends of the nonlinear resistors in parallel, one end of a coil of each high-frequency normally closed reed switch relay is connected with an output end of a monostable trigger chip (MC), and the other end of each high-frequency normally closed reed switch relay is connected with a direct-current power supply Vc.
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| CN113452003B (en) * | 2020-03-26 | 2022-07-22 | 南京南瑞继保电气有限公司 | Method and device for quickly eliminating ferromagnetic resonance of neutral point grounding system |
| CN113097986B (en) * | 2021-03-31 | 2022-10-18 | 国网内蒙古东部电力有限公司电力科学研究院 | Protection method, device and system for primary harmonic elimination device of distribution network voltage transformer |
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| CN2847639Y (en) * | 2005-11-11 | 2006-12-13 | 李彦 | Arc extinction and resonance extinction protector in nuetral point non-effective earthing system |
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