CN201773134U - A high-voltage direct current transmission thyristor damping loop current measuring device - Google Patents

Abstract

The utility model belongs to the technical field of measurement and test, and particularly relates to a device for measuring current of a high-voltage direct current power transmission thyristor damping circuit. The device comprises a shielding shell butted by a shielding shell I and a shielding shell II; a C-shaped magnetic core I wound with a coil I is arranged in the shielding shell I; a C-shaped magnetic core II wound with a coil II, an integrating circuit and a voltage divider are arranged in the shielding shell II; both an input end of the integrating circuit and the shielding shell II are connected with the coil II; an output end of the integrating circuit is connected with the voltage divider; measurement signals are output through an output end of the voltage divider; the output end of the voltage divider is connected with an elastic sheet structure; and the elastic sheet structure comprises a spring and a copper sheet. The damping circuit current measuring device has good shielding property, has little influence on the field strength distribution in the valve body of a converter valve, and has the advantages of small volume, good linearity, high reliability, good stability and the like; and the measurement range of the device is +/- 300kA, the frequency band is 40Hz to 20MHz, the sensitivity is 10mV/kA, and the maximum error is 0.48 percent.

Description

A high-voltage direct current transmission thyristor damping loop current measuring device

technical field

The utility model belongs to the technical field of measurement and testing, in particular to a current measuring device for a damping circuit of a high-voltage direct current transmission thyristor.

Background technique

The HVDC converter valve is a hoisting structure, and the interior is composed of dozens to hundreds of thyristors connected in series. There is an RC damping circuit at both ends of each thyristor, which acts as a pressure equalizer. When conducting tests such as periodic triggering and non-periodic triggering, when the thyristor is in the off state, the system voltage charges the damping capacitor C. During the triggering and opening process of the thyristor, the high voltage charged on the damping capacitor C is discharged through the thyristor immediately, which is quite Because a positive overshoot current is applied to the thyristor, the current rise rate (di/dt) at the moment of turn-on is increased. At this time, because the thyristor is not completely turned on, the injection of overshoot current is easy to burn the thyristor, which has great safety Hidden danger. At present, the method of determining this current is limited to simulation calculation, but in the test, the converter valve is located at a high potential, and its electromagnetic environment is very harsh, and it is easily affected by stray capacitance and inductance between layers and layers. Therefore, there are often large errors in simulation calculations, which cannot meet the actual needs of the project. Therefore, there is an urgent need for a thyristor damping circuit current measuring device that can be placed in the valve layer. However, the measuring device in this application field at home and abroad is still blank.

Utility model content

The technical problem to be solved by the utility model is to provide a high-voltage direct current transmission thyristor damping circuit current measuring device with small volume, wide measurement range, small error, high sensitivity, stability and reliability.

In order to solve the above technical problems, the utility model proposes a high-voltage direct current transmission thyristor damping circuit current measuring device, including a shielding case formed by butt jointing of a shielding case I and a shielding case II, and the shielding case I is provided with a winding coil The C-shaped magnetic core I of I, the shielding shell II is provided with a C-shaped magnetic core II wound with a coil II, an integrating circuit and a voltage divider, and the input end of the integrating circuit and the shielding shell II are both in phase with the coil II The output end of the integration circuit is connected to a voltage divider, and the output end of the voltage divider outputs the measurement signal, and the output end of the voltage divider is connected to a shrapnel structure, and the shrapnel structure is composed of a spring and a copper sheet.

Wherein, both the magnetic core I and the magnetic core II are C-shaped ferrite cores, the magnetic core fixing part I for fixing the magnetic core I is provided in the shielding case I, and the magnetic core fixing part I is provided in the shielding case II. Core holder II for fixing the core II.

Wherein, a fastening insert is arranged inside the shielding shell, and the coil I and the coil II are respectively connected with the fastening insert.

Wherein, the magnetic core fixing part I and the magnetic core fixing part II are annular structures made of insulating materials, the magnetic core fixing part I is bonded to the inside of the shielding shell I by insulating glue, and the magnetic core fixing part II It is bonded to the inside of the shielding shell II by insulating glue.

Wherein, both the shielding shell I and the shielding shell II adopt a C-shaped structure, and the opening ends of the shielding shell I and the shielding shell II are butted together and fixed by external fasteners to form an annular shielding shell.

Wherein, a slot is provided on the center line of the inner ring of the shielding shell, and an insulating sleeve for insulating and isolating the measured object is embedded in the slot.

Wherein, the number of turns of coil I wound on the magnetic core I is 5 turns, the number of turns of coil II wound on the magnetic core II is 5 turns, and the turn spacing between the coil I and coil II is 10 mm.

Wherein, the integrating circuit is composed of 10 resistors connected in parallel.

Wherein, the voltage divider is composed of two resistors connected in series, one of which is used as a high-voltage arm and connected to the integrating circuit, and the other resistor is used as a low-voltage arm and connected to the shielding shell II.

Wherein, the cross-sectional diameter of the magnetic core I and the magnetic core II is 15.5mm, the shell thickness of the shielding shell I and the shielding shell II is 3mm, the width of the slot is 2mm, and the thickness of the insulating sleeve is 3mm, the distance between the coil I and the shielding shell I and the distance between the coil II and the shielding shell II are both 5mm.

The beneficial effects of the utility model are:

1) The measuring device has high reliability and good stability, the measuring range can reach ±300A, and it has good linearity;

2) The frequency band of the measuring device can reach 40Hz-20MHz, and the high and low frequencies correspond well. The maximum measurement error is only 0.48%, which is far less than the 3% required by the high-voltage measurement standard;

3) The casing of the measuring device has good shielding performance. Since the insulating sleeve is embedded in the slot of the center line of the inner ring, the measuring device and the circuit under test can be in close contact without electrical connection, which is safe and reliable;

4) Both the internal magnetic core and the external shielding shell of the measuring device adopt a ring structure composed of two C-shaped members butted, which has the advantages of small size and light weight. The measuring device is nested in the converter valve by fastening the plug-in The damping circuit wire in the valve layer is easy to install and easy to operate.

Description of drawings

Fig. 1 is the equivalent circuit diagram of the self-integrating Rogowski coil;

Fig. 2 is a schematic diagram of the installation position of the current measuring device of the present invention;

Fig. 3 is the outline drawing of the current measuring device of the present utility model;

Fig. 4 is a schematic diagram of the internal structure of the current measuring device of the present invention, that is, a longitudinal sectional view of the current measuring device;

Among them, 1-shielding shell, 1a-shielding shell I, 1b-shielding shell II, 2a-magnetic core I, 2b-magnetic core II, 3-integrating circuit, 4-voltage divider, 4a-high voltage arm, 4b-low voltage Arm, 5a-coil I, 5b-coil II, 6a-core holder I, 6b-core holder II, 7-fastening insert, 7a-pin, 7b-slot, 8-external fastener , 9-slot, 10-spring, 11-end cover, 12-voltage divider output, 13-copper sheet.

Detailed ways

The current measuring device of the present invention will be further described in detail in conjunction with the accompanying drawings.

The damping loop current measuring device described in the utility model adopts the principle of the self-integrating Rogowski coil, and its equivalent circuit is shown in Figure 1. A coil L ₀ is wound on the skeleton surrounding the measured current, and the two ends of the coil will induce The induced potential e(t), which is proportional to the derivative di/dt of the measured current, is integrated by the integrating circuit R _r connected to both ends of the coil L ₀ , and the voltage waveform U _out (t) at both ends of the integrating circuit R _r It is consistent with the waveform of the measured current. The C ₀ is the capacitance generated between the coil L ₀ and the shielding case, and the R ₀ is the resistance generated between the coil L ₀ and the shielding case.

As shown in Figure 2, the current measuring device of the present invention is installed on the thyristor damping circuit wire in the valve layer of the converter valve, so the shape is designed as a paired structure, which is small in size and easy to install.

As shown in Figures 3 and 4, the current measuring device mainly includes two parts A and B:

Part A mainly includes C-shaped shielding shell I 1a and C-shaped magnetic core I 2a. The shielding shell I 1a is provided with two magnetic core fixing parts I 6a for fixing the magnetic core I 2a, the magnetic core fixing parts I are symmetrically bonded in the shielding case I through insulating glue, and the magnetic core fixing parts I 6a A fastening insert 7 is arranged side by side in the front, and the fastening insert is made up of pins 7a and slots 7b. In this example, the pins 7a of the fastening insert are bonded in the shielding shell I 1a by insulating glue; Set on the magnetic core I 2a, the coils I 5a wound on the magnetic core I 2a are evenly distributed after winding. Open the end cover 11 on the left side of the shielding shell 1, extend the magnetic core I wound with the coil 1 into the shielding shell 1, and fix the two short sides of the magnetic core 1 through the magnetic core holder 16a, and place the The two coil I joints at the head and tail of the copper enameled wire are respectively connected to the two pins 7a bonded in the shielding case I, and then the end cap 11 on the left side of the shielding case I is closed.

Part B mainly includes C-shaped shielding shell II 1b, C-shaped magnetic core II 2b, integrating circuit 3 and voltage divider 4. The shielding case II 1b is provided with two magnetic core fixing parts II 6b for fixing the magnetic core I 2a, and the magnetic core fixing parts II are symmetrically bonded in the shielding case II 1b through insulating glue. In this example, the fastening The slot 7b of the plug-in is bonded in the shielding shell II 1b with insulating glue; two copper enameled wires are symmetrically wound on the magnetic core II 2b, and the coils II 5b wound on the magnetic core II 2b are evenly distributed after winding. Open the end cover 11 on the right side of the shielding case II, extend the magnetic core II wound with the coil II into the shielding case II, and pass the two short sides of the magnetic core II through the magnetic core fixing part II 6b, and insert the two The two coil II connectors at the head end of the copper enameled wire are respectively connected to the slots 7b of the two fastening inserts, and then the two coil II connectors at the ends of the two copper enameled wires are respectively connected to the input terminal of the integrating circuit and the shielding shell II, and the integral The output end of the circuit is connected to the high-voltage arm 4a of the voltage divider, the low-voltage arm 4b of the voltage divider is connected to the end cover of the shielding shell II, the output end 12 of the voltage divider outputs the measurement signal, and the output end of the voltage divider is connected to a shrapnel structure , the elastic sheet structure is composed of a spring 10 and a copper sheet 13 . After the above-mentioned components are connected, the end cover 12 on the right side of the shielding case II is finally closed.

The shielding case I 1a and the shielding case II 1b are made of duralumin, with a thickness of 3mm, which can shield the complex electromagnetic interference from the outside. In this example, a ring of slots 9 is opened on the center line of the inner ring of the annular shielding shell 1. In practical applications, a 3mm thick insulating sleeve is first embedded in the slots 9 of the shielding shell I and the shielding shell II (Fig. (not shown in ), then nest the above-mentioned installed parts A and B on the thyristor damping circuit wire, insert the pin 7a of the fastening plug into the slot 7b, and connect the two parts A and B and fixation, and finally the two parts A and B can be fastened by two external fasteners 8 . After fastening, the shielding shell I and the shielding shell II are butted to form an annular shielding shell 1, and the magnetic core I and the magnetic core II are butted to form an annular magnetic core. The functions of the slot 9 are: firstly, to ensure that the coil in the shielding shell can well couple the magnetic field excited by the damping loop current; secondly, to cut off the induced circulating current on the shielding shell; thirdly, to provide an embedding position for the insulating sleeve. The magnetic core fixing part II6a and the magnetic core fixing part II 6b are annular structures made of insulating materials, and epoxy resin rings are used in this example.

Coil design: The design frequency band of the measuring device is 40Hz-20MHz. The high-frequency cut-off frequency of the self-integrating Rogowski coil mainly depends on the space capacitance C ₀ between the coil and the shielding shell. The smaller the space capacitance, the higher the high-frequency cut-off frequency; Its low-frequency cut-off frequency mainly depends on the ratio of the integrating circuit and the coil inductance. Therefore, the number of turns of the coil cannot be too many, otherwise the space capacitance _C0 between the coil and the shielding shell 1 is too large, and the high-frequency characteristics are not good; the number of turns of the coil cannot be too small, otherwise the current on the coil is too large, and the coil will It generates heat and requires the resistance generated by the integrating circuit to be extremely small. When the number of turns of the coil is small, its low-frequency cut-off frequency is not easy to reduce, so ferrite soft magnetic material is used as the core to increase the inductance. After calculation, the utility model determines to use C-shaped ferrite cores to form the frame structure, wherein the cross-sectional diameters of the C-shaped ferrite cores I and II are 15.5 mm, and the relative permeability is 2000. Coils I and II are both made of copper enameled wire, and the number of turns of the coil wound on the magnetic core I with a copper enameled wire is 5 turns: the two short sides of the magnetic core I 2a are respectively wound with 1 turn of coil I and the long side There are 3 turns of coil I; two copper enameled wires are used to wind symmetrically on the magnetic core II, and a total of 5 turns of coil II are wound: the first copper enameled wire is wound on one short side of the magnetic core II with 1 turn of coil II, and the length Two turns of coil II are wound on one side, and the second copper enameled wire is wound on the other short side and long side of the magnetic core II by one turn of coil II respectively; the turn spacing between coil I and coil II is uniformly wound, and coil I The distance between the shielding case I and the distance between the coil II and the shielding case II are both 5 mm.

The design of the integral circuit 3: If it is difficult to process the resistor with a very small resistance value, and it is greatly affected by the parasitic inductance, so after calculation, this device chooses to connect ten 1Ω resistors in parallel to form an integral circuit of 0.1Ω, and the integral circuit can be effectively to eliminate the effects of parasitic inductance.

The design of the voltage divider 4: the voltage divider 4 is composed of two resistors connected in series, one of which is connected to the integrating circuit 3 as the high-voltage arm 4a, and the other resistor is connected to the shielding shell II 1b as the low-voltage arm 4b, The voltage divider output terminal 13 outputs the measurement signal.

It has been verified by many experiments that the damping loop current measuring device designed above has good shielding performance, has little influence on the field strength distribution in the valve body of the converter valve, and has the advantages of small size, good linearity, high reliability, and good stability. , The measurement range of the device is ±300A, the frequency band is 40Hz-20MHz, the sensitivity is 10mV/kA, and the maximum error is 0.48%.

When the measuring device is in use, the entire device needs to be nested on the thyristor damping circuit wire in the valve layer of the converter valve through the fastening insert, and then the copper bar of the converter valve is inserted into the inner ring of the annular shielding shell 1 , the copper bar is in contact with the insulating pad embedded in the slot 9, and the device can monitor the current passing through the damping circuit of the ancestor tube. When the current measured by the device exceeds the range that the thyristor can withstand, it will be The start-up protection device protects the thyristor. Generally, the overcurrent flowing through the thyristor damping circuit is ±5Ka. The structural design of the measuring device makes its measuring range ±300A, which can greatly extend the service life of the measuring device.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present utility model and not to limit them. Although the present utility model has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: it is still possible Any modification or equivalent replacement made to the specific implementation of the present utility model without departing from the spirit and scope of the present utility model shall be covered by the claims of the present utility model.

Claims (10)

1. damping circuit current measuring device of high-voltage direct-current power transmission thyristor, it is characterized in that: this measurement mechanism comprises the shielding case (1) that is made of shielding case I (1a) and shielding case II (1b), be provided with the C shape magnetic core I (2a) that is twining coil I (5a) in the described shielding case I (1a), be provided with the C shape magnetic core II (2b) that is twining coil II (5b) in the described shielding case II (1b), integrating circuit (3) and voltage divider (4), the input end of described integrating circuit all is connected with coil II (5b) with shielding case II (1b), described integrating circuit output terminal connects voltage divider (4), described voltage divider output terminal (12) is exported measuring-signal, described voltage divider output terminal connects an elastic piece structure, and described elastic piece structure is made up of spring (10) and copper sheet (13).

2. damping circuit current measuring device according to claim 1, it is characterized in that: described magnetic core I (2a) and magnetic core II (2b) all adopt C shape FERRITE CORE, be provided with the magnetic core fixing device I (6a) that magnetic core I (2a) is fixed in the described shielding case I (1a), be provided with the magnetic core fixing device I I (6b) that magnetic core II (2b) is fixed in the shielding case II (1b).

3. damping circuit current measuring device according to claim 2 is characterized in that: be provided with fastening plug-in unit (7) in the described shielding case (1), described coil I (5a) is connected with fastening plug-in unit (7) respectively with coil II (5b).

4. damping circuit current measuring device according to claim 3, it is characterized in that: the ring texture that described magnetic core fixing device I (6a) and magnetic core fixing device I I (6b) make for insulating material, described magnetic core fixing device I (6a) is adhered to shielding case I (1a) inside by insulating gel, and described magnetic core fixing device I I (6b) is adhered to shielding case II (1b) inside by insulating gel.

5. damping circuit current measuring device according to claim 4, it is characterized in that: described shielding case I (1a) and shielding case II (1b) all adopt C shape structure, and the openend butt joint back of described shielding case I (1a) and shielding case II (1b) is fixed into a ring shielding shell (1) by external fastening (8).

6. damping circuit current measuring device according to claim 5 is characterized in that: the interior ring center line of described shielding case (1) is provided with slot (9), embeds to be useful on the insulation sleeve gasket that insulation is isolated with testee in described slot.

7. damping circuit current measuring device according to claim 6, it is characterized in that: coil I (5a) number of turn that described magnetic core I (2a) goes up coiling is 5 circles, coil II (5b) number of turn that described magnetic core II (2b) goes up coiling is 5 circles, and the turn-to-turn distance of described coil I (5a) and coil II (5b) is 10mm.

8. damping circuit current measuring device according to claim 7 is characterized in that: described integrating circuit (3) is made of 10 parallel resistor.

9. damping circuit current measuring device according to claim 8, it is characterized in that: described voltage divider (4) is made of the resistance of two series connection, one of them resistance is connected with integrating circuit (3) as high-voltage arm (4a), and another resistance is connected with shielding case II (1b) as low-voltage arm (4b).

10. damping circuit current measuring device according to claim 9, it is characterized in that: the diameter of section of described magnetic core I (2a) and magnetic core II (2b) is 15.5mm, the shell of described shielding case I (1a) and shielding case II (1b) is thick to be 3mm, the width of described slot (9) is 2mm, the thickness of described insulation sleeve gasket is 3mm, and described coil I (5a) is 5mm with the spacing of shielding case I and the spacing of described coil II (5b) and shielding case II.

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