CN206040418U - Three -phase harmonic elimination formula voltage transformer - Google Patents
Three -phase harmonic elimination formula voltage transformer Download PDFInfo
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- CN206040418U CN206040418U CN201621010254.2U CN201621010254U CN206040418U CN 206040418 U CN206040418 U CN 206040418U CN 201621010254 U CN201621010254 U CN 201621010254U CN 206040418 U CN206040418 U CN 206040418U
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical group [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 11
- 238000009413 insulation Methods 0.000 claims description 14
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- 238000012360 testing method Methods 0.000 description 1
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Abstract
The utility model provides a three -phase harmonic elimination formula voltage transformer, including primary winding, secondary winding, iron core and insulating, wherein, primary winding A, B, C leading -out terminal correspond the looks line connection with high voltage electric network respectively, and primary winding A and primary winding C's star connection neutral point and primary winding B's head end are connected, primary winding B's terminal ground connection, secondary winding is divided into three group winding, wherein, meets kilowatt -hour meter wh between the terminal outgoing lines a1 of secondary metering winding and the b1, meets kilowatt -hour meter wh between terminal outgoing lines b1 and the c1, and the terminal outgoing lines a2 of secondary measuring winding, b2, c2, n connect looks space voltmeter V, and traditional symmetrical neutal point earthing, only primary winding B's terminal ground connection have been broken for opening triangle wiring, this utility model to the surplus winding, do you and have only B the N winding can provide zero sequence current's passageway, has destroyed the condition that zero sequence current produced, has simply solved ferroresonance's problem among the isolated neutral system effectively.
Description
Technical Field
The utility model relates to a voltage transformer technical field, concretely relates to three-phase harmonic elimination formula voltage transformer.
Background
The insulation systems of 10-35kv power grids in China are neutral point insulation systems. In a power system with neutral point to ground insulation, in order to monitor the insulation of the line, as shown in fig. 1, three star-connected grounded voltage transformers are used, in which the neutral point is directly grounded, as shown in fig. 1: cA、CB、CCThree phase to ground equivalent capacitances; A. b, C three-phase inductance LA、LB、LCCorresponding reactance is XmA、XmB、XmCWhen the neutral point non-effective grounding system is in normal operation, XmA≈XmB≈XmC，CA≈CB≈CCThe neutral point voltage is zero. When any one phase of bus has single complete grounding accident, the voltage of the fault phase to the ground is 0V, and the phase voltage of the non-fault phase rises to the line voltage, namely, the voltage is increasedThe 3-block voltmeter measuring each phase voltage by the secondary winding of the voltage transformer can conveniently monitor which phase is insulated and has a problem. However, the bus line to ground capacitance CA、CB、CCThe capacitor and the primary winding of the voltage transformer form a parallel circuit, and the transformer is a typical nonlinear ferromagnetic element, and when some excitation occurs, such as closing of an air drop bus or a short circuit, generation and disappearance of a single-phase arc grounding, sudden rise of voltage and the like, the voltage of a certain two-phase voltage transformer is likely to change. And since PT is Y0/Y0The wiring is in neutral point symmetrical grounding, the grounding capacitor is also in neutral point symmetrical grounding, two-phase voltage in three phases changes, PT neutral point displacement generates zero-sequence current and zero-sequence voltage, and the small zero-sequence current generates enough zero-sequence magnetic flux in the non-fault phase voltage transformer to saturate an iron core, so that the non-lineInductive reactance X of ferromagnetic elementLReduce, at a certain moment, when the inductive reactance in the line is equal to the capacitive reactance (X)L＝XC) Ferromagnetic resonance will occur.
In order to monitor the system for insulation grounding, grounding voltage transformers are commonly used in the system, and currently, a mode of connecting three single-phase voltage transformers into a three-phase group is mostly adopted. The voltage transformers are all electromagnetic type, are nonlinear inductance elements, are connected in parallel with a power grid wire to ground capacitor to form a ferromagnetic resonance loop, generate resonance under a certain excitation condition, and generate overvoltage and overcurrent. Operation experience shows that voltage transformer burnout and power grid power failure accidents caused by ferromagnetic resonance are common.
For a long time, a power system has conducted many experimental studies on this, and a series of harmonic elimination measures have been taken and put into practice. The main resonance elimination measures are: (1) the excitation characteristic of the voltage transformer is improved: the most fundamental is to select a voltage transformer with good excitation volt-ampere characteristic, and the iron core of the voltage transformer is not enough to enter a deep saturation region under a common overvoltage level, so that the voltage transformer and line parameters do not form matching parameters for generating resonance. (2) The number of voltage transformers connected in parallel in the same network is reduced: in the same power grid, the more the number of voltage transformers which are operated in parallel, the worse the total voltage-current characteristic becomes, the smaller the total equivalent inductive reactance becomes, and if the capacitance current in the power grid is larger, ferromagnetic resonance is easy to occur. The number of voltage transformers in the same system should be reduced as much as possible. (3) Every phase of a 10kV bus is provided with a capacitor: when X in the systemC/XLWhen the frequency is less than or equal to 0.01, ferromagnetic resonance is not easy to occur. Therefore, a capacitor bank with a grounded neutral point can be additionally arranged in a small substation below 10kV or a reliable cable is selected to replace a section of outgoing line overhead bus. For the condition that a large substation is connected with a plurality of voltage transformers, the method of additionally arranging the capacitor is not suitable for being adopted due to the fact that the capacitance which needs to be additionally arranged is large. (4) A harmonic eliminator or a series resistor is arranged at the neutral point of a voltage transformer in the system and is grounded: when an earth fault occurs, the resonance is eliminated due to the higher voltage appearing on the resonance elimination deviceThe switch is turned on, so that the functions of energy consumption, damping and current suppression can be achieved, the voltage on the voltage transformer is reduced, and the volt-ampere characteristic of the voltage transformer is improved. But the resistance should be chosen to be large. However, when the resistance is too large, the open-delta voltage is reduced when the single phase is grounded, which has a certain influence on the correct operation of the protection. Therefore, a reasonable resistor is selected, a nonlinear resistor is suitable, the resistance value is large in normal conditions, and the resistance value is reduced under the action of high voltage when a fault occurs, so that the functions of energy consumption, damping and the like can be achieved, and the reliability of the protection function of the opening triangle is not influenced. This approach is often used in systems of 10kV and below. (5) The three open corners of the voltage transformer are provided with a resonance elimination device or a resistor: the resonance eliminating device or the resistor is arranged at the three opening corners of the voltage transformer, so that the effects of damping, resonance elimination and resonance inhibition can be achieved, the effect of limiting the current in the voltage transformer can be achieved, and the current of each phase of the voltage transformer is reduced, so that the volt-ampere characteristic is improved. (6) The high-voltage side neutral point is connected with a single-phase voltage transformer in series: a single-phase voltage transformer (namely a zero-sequence voltage transformer) is connected in series with a neutral point on the high-voltage side of the voltage transformer.
The measures described above each have a certain effect in practice on suppressing resonance. However, the resonance elimination measures used in neutral point insulation systems are mostly passive resonance elimination, i.e. the resonance elimination device only functions after the occurrence of a resonance. If the resonance is not effectively eliminated once the resonance-eliminating measures have failed, the harm remains.
SUMMERY OF THE UTILITY MODEL
The application provides a three-phase harmonic elimination formula voltage transformer to solve the technical problem of ferromagnetic resonance among the neutral point insulating system.
In order to solve the technical problems, the application adopts the following technical scheme:
a three-phase harmonic elimination type voltage transformer comprises a primary winding, a secondary winding, an iron core and insulation, wherein an outlet end of the primary winding A, B, C is connected with a corresponding phase line of a high-voltage power grid respectively, star junction neutral points of the primary winding A and the primary winding C are connected with a head end of the primary winding B, the tail end of the primary winding B is directly grounded, the secondary winding is divided into three groups of windings, an electric meter wh is connected between outlet terminals a1 and B1 of the secondary metering winding, an electric meter wh is connected between outlet terminals B1 and C1, outlet terminals a2, B2, C2 and n of the secondary metering winding are connected with a voltmeter V between the phase lines, the rest winding is in open delta connection, and the outlet terminals are da and dn.
The utility model discloses a cancelled the ground voltage transformer that traditional electromagnetic type voltage transformer generally adopted 3 star couplings, the way of neutral point direct ground connection, but only winding B's one end N termination ground, and only B-N winding can provide zero sequence current's passageway, destroyed the condition that zero sequence current produced, proved through experiment and practice that this kind of unique wiring design has succeeded in solving the problem of ferromagnetic resonance among the neutral point insulation system.
Further, the winding AB and the winding BC work at the online voltage, the winding B0 works at the phase voltage, and the phase voltage is:wherein,is the voltage of the inter-phase B0 phase,is the voltage of the inter-phase a0 phase,is the line voltage between the line voltage AB,is the voltage of the inter-phase C0 phase,is the line voltage between BC.
Furthermore, the three-phase harmonic elimination type voltage transformer is formed by casting epoxy resin, and belongs to maintenance-free products.
Compared with the prior art, the technical scheme that this application provided, the technological effect or advantage that have are:
1) the utility model discloses a cancelled the wiring form of traditional mutual-inductor symmetry neutral point ground connection, only the B-N winding can provide zero sequence current's passageway, has destroyed the condition of frequency division resonance, has eliminated frequency division resonance and other resonances, consequently, any operation of this system can not cause the resonance.
2) In which single-phase earthing occurs, with relative earth inductance XLThe size of the transformer core cannot be reduced, the iron core cannot be magnetized and saturated or resonate, and the voltage transformer cannot be damaged. The GB20840.3-2013 standard is implemented, the service condition of a 10kV insulation system is met, and resonance can not occur under various disturbance factors in system operation. The self-recovery capability to the pollution flashover grounding fault is unique.
3) Tests and practices prove that the voltage transformer is irrelevant to the size of the system grounding capacitor and can compensate the grounding capacitor current at will.
In conclusion, the three-phase harmonic elimination type voltage transformer can meet the normal use function, can eliminate the adverse effect of the traditional voltage transformer on the system, and creates a powerful supporting point for the safe and reliable operation of the power system.
Drawings
FIG. 1 is an equivalent circuit diagram of a conventional electromagnetic voltage transformer;
FIG. 2 is a schematic diagram of the primary winding wiring of the present invention;
FIG. 3 is a schematic diagram of the secondary metering winding wiring of the present invention;
FIG. 4 is a schematic diagram of the secondary measurement winding wiring of the present invention;
FIG. 5 is a schematic diagram of the residual winding wiring of the present invention;
fig. 6 is a wiring circuit diagram of the present invention;
fig. 7 is a voltage vector diagram of the present invention;
fig. 8 is an equivalent vector diagram of three-phase voltages of the present invention.
Detailed Description
The embodiment of the application provides a three-phase harmonic elimination type voltage transformer to solve the technical problem of ferromagnetic resonance in a neutral point insulation system.
In order to better understand the technical solutions, the technical solutions will be described in detail below with reference to the drawings and specific embodiments.
Example 1:
a three-phase harmonic elimination type voltage transformer comprises a primary winding, a secondary winding, an iron core and an insulator, wherein outlet ends of the primary winding A, B, C are respectively connected with corresponding phase lines of a high-voltage power grid, as shown in fig. 2, star junction neutral points of a primary winding A and a primary winding C are connected with the head end of a primary winding B, the tail end of the primary winding B is directly grounded, the secondary winding is divided into three groups of windings, as shown in fig. 3, a watt-hour meter wh is connected between outlet terminals a1 and B1 of the secondary metering winding, a watt-hour meter wh is connected between outlet terminals B1 and C1, as shown in fig. 4, a voltmeter V is connected between the outlet terminals a2, B2, C2 and n of the secondary metering winding, as shown in fig. 5, the rest windings are in open delta connection mode, and the outlet terminals are da and dn. Fig. 6 is a wiring circuit diagram of the present invention.
The utility model discloses a cancelled traditional electromagnetic type voltage transformer and generally adopted 3 ground voltage transformer that star connection, the way of neutral point direct ground connection, but only winding B's one end N end ground connection, only B-N winding can provide zero sequence current's passageway, has destroyed the condition that zero sequence current produced, has proved through experiment and practice that this kind of unique wiring design has successfully solved the problem of ferromagnetic resonance among the neutral point insulation system.
The AB winding and the CB winding are connected with the phase-to-phase voltage (namely the line voltage) for measurement and measurement. The impedance of the voltage transformer is in parallel connection with the system impedance, the winding impedance is greater than the system impedance, the initial saturation voltage of the winding volt-ampere characteristic is greater than 2 times of the line voltage, the iron core of the voltage transformer cannot enter a deep saturation region under the general overvoltage level, and the overload capacity is strong. In addition, when the A phase or the C phase generates single-phase grounding, the inductive reactance X of the grounding windingLIt is not reduced and the core is not saturated or causes resonance.
The utility model discloses a three-phase harmonic elimination formula voltage transformer adopts three single-phase voltage transformer to combine as an organic whole through special wiring (namely: the way of canceling the direct ground connection of neutral point, but only the one end N of winding B holds ground connection) on the overall structure in order to eliminate ferromagnetic resonance. The rectangular integral iron core is adopted by the inner iron core of each single-phase voltage transformer, so that the manufacturing is convenient, the working time is saved, the exciting current is reduced, the no-load loss of the exciting current is reduced, the product quality is improved, and the error is reduced; the primary winding is provided with an inner shielding layer and an outer shielding layer, so that the partial discharge level is improved, and the voltage gradient is improved; the winding aspect adopts the full-automatic winding machine equipment controlled by the CPU, so that the work efficiency and the product quality can be improved.
Further, fig. 7 shows that the voltage vector diagram of the present invention, winding AB and winding BC work at online voltage, winding B0 works at phase voltage, and its phase voltage is:wherein,is the voltage of the inter-phase B0 phase,is the voltage of the inter-phase a0 phase,is the line voltage between the line voltage AB,is the voltage of the inter-phase C0 phase,is the line voltage between BC.
Fig. 8 shows the three-phase voltage equivalent vector diagram of the present invention, which is the same as the conventional voltage-variable line set, and is also the same for protection and insulation monitoring functions.
Furthermore, the three-phase harmonic elimination type voltage transformer is formed by casting epoxy resin, and belongs to maintenance-free products.
In the above embodiments of the present application, by providing a three-phase harmonic elimination type voltage transformer, which includes a primary winding, a secondary winding, an iron core and an insulator, wherein the outgoing line end of the primary winding A, B, C is connected to the corresponding phase line of the high voltage grid, the star neutral point of the primary winding a and the primary winding C is connected to the head end of the primary winding B, the tail end of the primary winding B is grounded, the secondary winding is divided into three groups of windings, wherein the outgoing line terminal a1 and B1 of the secondary metering winding is connected to the watt hour meter wh, the outgoing line terminal B1 and C1 are connected to the watt hour meter wh, the outgoing line terminals a2, B2, C2 and N of the secondary metering winding are connected to the inter-phase voltmeter V, and the remaining windings are connected by an open triangle, the utility model cancels the traditional symmetrical neutral point grounding, only the B-N winding can provide the channel of the zero sequence current, and destroys the, the problem of ferromagnetic resonance in a neutral point insulation system is simply and effectively solved.
It should be noted that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and the changes, modifications, additions or substitutions made by those skilled in the art within the spirit of the present invention should also belong to the protection scope of the present invention.
Claims (3)
1. A three-phase harmonic elimination type voltage transformer comprises a primary winding, a secondary winding, an iron core and insulation, wherein outlet ends of the primary winding A, B, C are respectively connected with corresponding phase lines of a high-voltage power grid, and the three-phase harmonic elimination type voltage transformer is characterized in that star junction neutral points of the primary winding A and the primary winding C are connected with the head end of the primary winding B, the tail end of the primary winding B is grounded, the secondary winding is divided into three groups of windings, wherein an outlet terminal a1 and a B1 of the secondary metering winding are connected with an electricity meter wh, an outlet terminal B1 and a C1 are connected with the electricity meter wh, outlet terminals a2, B2, C2 and n of the secondary metering winding are connected with an inter-phase voltmeter V, the rest of the outlet windings are in open delta connection, and the outlet terminals are da.
2. The three-phase harmonic elimination voltage transformer of claim 1 wherein windings AB and BC operate at on-line voltage and windings B0 operate at phase voltages: wherein,is the voltage of the inter-phase B0 phase,is the voltage of the inter-phase a0 phase,is the line voltage between the line voltage AB,is the voltage of the inter-phase C0 phase,is the line voltage between BC.
3. The three-phase resonance-eliminating voltage transformer according to claim 1, wherein the three-phase resonance-eliminating voltage transformer is molded by epoxy resin casting.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201621010254.2U CN206040418U (en) | 2016-08-31 | 2016-08-31 | Three -phase harmonic elimination formula voltage transformer |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201621010254.2U CN206040418U (en) | 2016-08-31 | 2016-08-31 | Three -phase harmonic elimination formula voltage transformer |
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| CN206040418U true CN206040418U (en) | 2017-03-22 |
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| CN201621010254.2U Expired - Fee Related CN206040418U (en) | 2016-08-31 | 2016-08-31 | Three -phase harmonic elimination formula voltage transformer |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106158335A (en) * | 2016-08-31 | 2016-11-23 | 天水长开互感器制造有限公司 | A kind of three-phase resonance-eleminating type voltage inductor |
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2016
- 2016-08-31 CN CN201621010254.2U patent/CN206040418U/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106158335A (en) * | 2016-08-31 | 2016-11-23 | 天水长开互感器制造有限公司 | A kind of three-phase resonance-eleminating type voltage inductor |
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| CF01 | Termination of patent right due to non-payment of annual fee | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20170322 Termination date: 20170831 |