CN203759193U - Direct-current partial discharge detection device of converter transformer - Google Patents

Abstract

A DC partial discharge detection device for a converter transformer, in which a detection impedance is connected in series on the valve side winding and the grid side winding of the converter transformer at the same time, and the pulse voltage on the detection impedance is monitored, if the pulse voltage detected on the two detection impedances If the polarities are opposite, it is considered that there is a partial discharge signal inside the converter transformer; if the polarity of the pulse voltage detected on the two impedances is the same, it is considered to be an external interference discharge signal. The utility model discloses a DC partial discharge measurement technology of a converter transformer, which fills the blank of the current DC partial discharge detection, can effectively eliminate the interference of external discharge signals, and accurately separate the partial discharge signals inside the converter transformer. Use the electro-acoustic combination method to further judge the partial discharge signal. Ultrasound is used to further detect the analysis and determination of the occurrence of partial discharge signals and the exact location. This combination of sound and electricity has high detection effectiveness and reliability.

Description

Converter Transformer DC Partial Discharge Detection Device

technical field

The utility model relates to the field of high-voltage equipment insulation monitoring, in particular to a DC partial discharge detection device for a converter transformer.

Background technique

With the rapid development of UHV DC transmission, the insulation performance testing and assessment of DC transmission and transformation equipment has brought new technical problems. The converter transformer is one of the core DC power transmission and transformation equipment, and its insulation is oil-paper insulation. If there are local defects in the oil-paper insulation, it will affect the overall electrical strength and cause major safety hazards to the operation. Therefore, it is necessary to test the insulation performance of the converter transformer when it is put into operation or overhauled.

Partial discharge (hereinafter referred to as partial discharge) refers to the discharge caused by a certain part of the insulating material due to the concentration of the electric field. This discharge phenomenon does not penetrate the entire insulation, reflecting the existence of weak links in the insulating material. It is an important means to judge whether there is a defect inside the insulation to judge whether there is a partial discharge by detecting various sound, light, and electrical phenomena accompanying the partial discharge process.

The voltage distribution of the insulating medium under the action of DC voltage and AC voltage is different. Therefore, in the DC power transmission and transformation system, in order to simulate the actual operating conditions, it is necessary to conduct DC withstand voltage tests and partial discharge measurements on the converter transformers.

The characteristic parameters of DC partial discharge are the apparent discharge amount and the number of pulses, and the partial discharge status is evaluated by detecting various phenomena and physical quantities accompanying partial discharge. Due to the low repetition rate of DC PD pulses, strong randomness of individual pulses, and no characteristics of AC PD pulse groups, the problem of anti-interference is prominent during on-site measurement, and it is difficult to judge whether the detected signal is a real PD signal. How to truly and effectively identify DC PD is a major problem to be solved urgently in the DC PD measurement of converter transformers in the world.

Contents of the invention

The technical problem to be solved by the utility model is to provide an effective DC partial discharge detection device for a converter transformer.

The DC partial discharge detection device of the converter transformer is connected to a DC high-voltage generator on the valve side of the converter transformer, and the output end of the high-voltage generator is connected in parallel with a voltage divider, and the feature is: the valve side of the converter transformer The bushings at both ends are connected to the output line of the DC high-voltage generator, the bushings at both ends of the grid side of the converter transformer are short-circuited, and the end screens of the bushings on the valve side and the grid side of the converter transformer are connected to the ground respectively. The detection impedance matched by the equivalent capacitance of the tube is sampled from the output terminals of the two detection impedances to the input terminal of the partial discharge tester.

An embodiment of detection impedance considering higher signal-to-noise ratio and impedance matching is that the detection impedance is composed of bushing equivalent capacitance, first tuning resistor, and primary winding of coupling transformer to form an RLC resonant circuit, through coupling capacitance and coupling transformer It is connected to the impedance matching module, and the output signal of the impedance matching module is output to the partial discharge detector through the amplifier.

Further, considering impedance protection, a gas discharge tube is connected between the primary two ends of the coupling transformer, or between the primary two ends of the coupling transformer and the ground.

An embodiment of an RLC circuit is that the RLC resonant circuit is composed of the primary winding of the coupling transformer connected in parallel with the first tuning resistor, and one end is connected with the bushing equivalent capacitance equivalent to the bushing.

As an embodiment of impedance matching, the impedance matching module is provided with a second tuning resistor, the second tuning resistor is connected in parallel with the secondary winding of the coupling transformer, and the two ends of the second tuning resistor are connected to the two input terminals of the amplifier, The output terminal of the impedance matching module is led out through the output terminal of the amplifier.

The second tuning resistor is connected to the coupling capacitor through the test tuning resistor connected in series, and the two ends of the test tuning resistor are connected to the calibration input terminal, and the calibration input terminal is used to output calibration by the partial discharge detector. The signal is tested for matching impedance.

The utility model correctly identifies the DC partial discharge signal inside the converter transformer through the method of combining electro-acoustic comprehensive judgment and polarity judgment, and effectively solves the discrimination and detection of the DC partial discharge signal. The detection impedance is generated by the RLC circuit to resonate and amplify the partial discharge signal. The parameters of the RLC match the capacitance of the bushing of the converter transformer, so that the voltage collected on the impedance is easy to detect. The utility model also has the following significant advantages:

(1) A DC partial discharge measurement technology of a converter transformer is disclosed, which fills the current blank of DC partial discharge detection.

(2) Based on the pulse current method, supplemented by polarity judgment, by simultaneously detecting the pulse voltage polarity on the matching detection impedance connected in series on the grid side and the valve side, it is judged whether the partial discharge occurs inside the converter transformer. This method can effectively eliminate the interference of external discharge signals, and accurately separate the partial discharge signals inside the converter transformer.

(3) Use the electro-acoustic combination method to further judge the partial discharge signal. When the pulse current method supplemented by polarity judgment is used to preliminarily determine the presence of partial discharge signals inside the converter, ultrasonic waves are used to further detect the occurrence of partial discharge signals and determine the exact location. This combination of sound and electricity has high detection effectiveness and reliability.

Description of drawings

Figure 1 Schematic diagram of the overall measurement circuit for on-site DC partial discharge,

Fig. 2 is the embodiment circuit diagram of impedance module,

Figure 3 Schematic diagram of DC partial discharge measurement,

Figure 4. The power supply input mode of the DC partial discharge instrument.

In the figure: 1—Equivalent capacitance of bushing, 2—Impedance detection input terminal, 3—Coupling capacitor, 4—Gas discharge tube, 5—First tuning resistor, 6—Coupling transformer, 7—Second tuning resistor, 8— Amplifier, 9—test tuning resistor, 10—calibration input terminal, 11—DC high voltage generator, 12—voltage divider, 13—converter transformer, 14—detection impedance, 15—partial discharge tester.

Detailed ways

Below in conjunction with accompanying drawing and embodiment the utility model is further described: converter transformer DC partial discharge detection device as shown in Fig. A voltage divider 12 is connected in parallel at the output end of the DC high voltage generator, and the DC high voltage generator is used to generate DC high voltage, which is sent to the bushings at both ends of the valve side of the converter transformer 13. The voltage divider 12 is used to measure the DC high voltage generated by the high voltage generator 11. .

The bushings at both ends of the valve side of the converter transformer 13 are connected to the output line of the DC high voltage generator 11, the bushings at both ends of the grid side of the converter transformer 13 are short-circuited, and the valve side and the grid side of the converter transformer 13 The end screens of the bushings are respectively connected to the ground with the detection impedance 14 matching the bushing equivalent capacitance 1, and samples are taken from the output ends of the two detection impedances 14 to the input ends of the partial discharge tester 15 respectively. As shown in Figure 1, Z ₁ is connected in series between the bushing on the valve side and the ground, and Z ₂ is connected in series between the bushing on the grid side and the ground; the discharge signals obtained on Z ₁ and Z ₂ are sent to the partial discharge detector 15 .

A kind of detection impedance embodiment that considers higher signal-to-noise ratio and impedance matching is, as shown in Fig. 2, described detection impedance 14 is formed RLC resonance by bushing equivalent capacitance 1 and first tuning resistance 5, the primary winding of coupling transformer 6 The circuit is connected to the impedance matching module through the coupling capacitor 3 and the coupling transformer 6, and the output terminal of the impedance matching module outputs a signal to the partial discharge detector through the amplifier 8. The gas discharge tube 4 is connected between the primary two ends of the coupling transformer 6 or between the primary two ends of the coupling transformer 6 and the ground. To prevent excessive discharge voltage from damaging the detection impedance. An embodiment of an RLC circuit is that the primary winding of the coupling transformer 6 is connected in parallel with the first tuning resistor 5 , and one end is connected with the bushing equivalent capacitance 1 equivalent to the bushing. This is just one example of implementing an RLC resonant circuit.

As shown in Fig. 2, as an embodiment of impedance matching, the impedance matching module is provided with a second tuning resistor 7, and the second tuning resistor 7 is connected in parallel with the secondary winding of the coupling transformer 6. Both ends lead out the output end of the matching module through the output end of the amplifier 8 . The second tuning resistor 7 is connected to the coupling capacitor 3 through a test tuning resistor 9 connected in series, and the two ends of the test tuning resistor 9 are connected to a calibration input terminal 10, which is used for local The output detector 15 outputs a calibration signal to test the matching impedance.

Utilize above-mentioned device, utilize pulse current method, on the valve side winding of converter transformer 13 and network side winding, simultaneously insert detection impedance 14 in series, and monitor the pulse voltage on detection impedance 14, if two detection impedances 14 detect If the polarity of the pulse voltage is opposite, it is considered that there is a partial discharge signal inside the converter transformer; if the polarity of the pulse voltage detected on the two impedances is the same, it is considered to be an external interference discharge signal.

Its principle is shown in Figure 3. The external interference current (i ₁ +i ₂ ) generates pulse signals in the same direction on the detection impedance Z ₁ and Z ₂ , and the inner bushing C ₁ on the valve side of the transformer and the bushing on the grid side C ₂ The partial discharge current i ₃ will generate pulse signals in opposite directions on the detection impedances Z ₁ and Z ₂ . When the polarity of the power supply is positive, the partial discharge in _C1 generates a positive polarity pulse signal on Z1, the partial discharge in _C2 generates a negative polarity pulse signal on _Z1 , the high-voltage lead corona, Ce (external disturbance equivalent The partial discharge in the capacitor) generates negative polarity pulse signals on Z ₁ and Z ₂ . Therefore, this method can be used to judge whether the pulse signal comes from the inside or outside of the test object, and whether the test object C ₁ or C ₂ .

The comprehensive ultrasonic judgment can greatly improve the reliability and accuracy of the judgment. While using the pulse current method for detection, at least three ultrasonic probes for partial discharge measurement are installed on the metal shell of the converter transformer 13 body, Discharge and/or location judgment is performed on the position of the DC discharge through the detected echo signal. The ultrasonic probe is attached to the transformer body through a suction cup. In order to obtain a better detection effect, it is generally attached to the root of the transformer bushing. To realize the localization of PD signals, at least three ultrasonic probes need to be arranged to obtain the three-dimensional coordinates of the PD exit point in space.

Z ₁ and Z ₂ are composed of RLC circuit components. It is necessary to select appropriate circuit parameters according to the capacitance design of the test product, so that the detection impedance is most sensitive to the high-frequency partial discharge signal. The detection impedance is connected in series in the loop, and the pulse current generated by PD flows through the detection impedance to generate a pulse voltage, which can reflect the characteristics of the PD signal and reproduce the PD pulse waveform.

The power input method of the partial discharge detector is shown in Figure 4: the external 220V mains enters the isolation transformer to isolate the interference signal in the mains; then enters the filter to filter out the harmonic interference in the power supply; finally step down to The weak current signal is supplied to each hardware circuit module of the partial discharge instrument. At the same time, the grounding of each hardware circuit is uniformly connected to the only grounding terminal, and is grounded at one point through the grounding terminal.

Claims (6)

1. A DC partial discharge detection device for a converter transformer, a DC high-voltage generator (11) is connected to the valve side of the converter transformer, and a voltage divider (12) is connected in parallel at the output end of the high-voltage generator (11), It is characterized in that: the bushings at both ends of the valve side of the converter transformer (13) are connected to the output line of the DC high-voltage generator (11), and the bushings at both ends of the grid side of the converter transformer (13) are short-circuited. The valve side of the converter transformer (13) and the end screen of the bushing on the grid side are respectively connected to the ground with the detection impedance (14) matching the bushing equivalent capacitance (1), and the output terminals of the two detection impedances (14) are respectively connected to the ground. Sampled to the input of the partial discharge tester (15). 2. The DC partial discharge detection device of the converter transformer according to claim 1, characterized in that: the detection impedance (14) is composed of the bushing equivalent capacitance (1), the first tuning resistor (5), the coupling transformer ( 6) The primary winding forms an RLC resonant circuit, which is connected to the impedance matching module through the coupling capacitor (3) and the coupling transformer (6), and the output signal of the impedance matching module is output to the partial discharge detector through the amplifier (8) . 3. The DC partial discharge detection device of the converter transformer according to claim 2, characterized in that it is connected between the primary two ends of the coupling transformer (6), or between the primary two ends of the coupling transformer (6) and the ground There are gas discharge tubes (4). 4. The DC partial discharge detection device of the converter transformer according to claim 2, characterized in that: the RLC resonant circuit is connected to the primary winding of the coupling transformer (6) in parallel with the first tuning resistor (5), and one end is connected to Consists of bushing equivalent capacitance (1) equivalent to the bushing. 5. The DC partial discharge detection device of the converter transformer according to claim 2, characterized in that: the impedance matching module is provided with a second tuning resistor (7), and the second tuning resistor (7) is connected to the coupling transformer ( 6) The secondary windings are connected in parallel, the two ends of the second tuning resistor (7) are connected to the two input ends of the amplifier (8), and the output end of the impedance matching module is drawn out through the output end of the amplifier (8). 6. The DC partial discharge detection device for converter transformers according to claim 5, characterized in that: the second tuning resistor (7) is connected to the coupling capacitor (3) through a series-connected test tuning resistor (9) , both ends of the test tuning resistor (9) are connected to a calibration input terminal (10), and the calibration input terminal (10) is used to output a calibration signal from a partial discharge detector (15) to test the matching impedance.