Protection method of external voltage synchronous acquisition circuit for partial discharge withstand voltage test

Abstract

The invention relates to a protection method of an external voltage synchronous acquisition circuit for a partial discharge withstand voltage test. According to the method, the voltage amplitude signal output end of an A / D conversion circuit, the frequency signal output end of a V-F voltage-frequency circuit and the frequency signal output end of an I-F current-frequency circuit are connected with three signal input pins of a gating chip respectively, and a single-chip microcomputer is connected with the control end of the gating chip. The signal output pin of the gating chip is connected with the input end of the optical coupling isolator, and the output end of the optical coupling isolator is connected with the partial discharge detection module. The single-chip microcomputer controls only one signal of the V-F voltage-frequency circuit or the I-F current-frequency circuit to be conducted through the gating chip. A high-voltage-resistant optical coupling isolator is adopted, the isolation distance between a light emitting end and a light receiving end is 35-37 mm, and the isolation voltage is 100 KV. Under the condition that the size is reduced and integration is facilitated, good isolation performance and anti-impact effect between high voltage and low voltage of the external synchronous voltage acquisition circuit are ensured.

Description

Technical Field

[0001] The invention belongs to the field of electric power equipment measurement methods, and in particular relates to a protection method for an external voltage synchronous acquisition circuit used for a partial discharge withstand voltage test. Technical Background When conducting a high-voltage withstand partial discharge test, when the object under test reaches the highest withstand voltage, the high-voltage ball gap will be broken down, resulting in a high-voltage discharge shock. During the test, external voltage synchronous acquisition is required to make the synchronous discharge signal match the reference phase, which is conducive to the accurate judgment of the partial discharge signal. However, the high-voltage discharge shock enters the external voltage synchronous acquisition circuit, which will damage the electronic components and low-voltage electronic circuits, and circuit protection is required.

[0003] The existing external voltage synchronous acquisition circuit has a voltage input terminal Vin and a current input terminal Iin, including an A / D analog-to-digital conversion circuit, a VF voltage-frequency circuit and an IF current-frequency circuit. The voltage amplitude signal output terminal of the A / D analog-to-digital conversion circuit is connected to the input terminal of an optocoupler isolator, the frequency signal output terminal of the VF voltage-frequency circuit and the frequency signal output terminal of the IF current-frequency circuit are connected to the input terminal of another optocoupler isolator, and the output terminals of the two optocoupler isolators are connected to the partial discharge detection module. When the external voltage is synchronously acquired, the A / D analog-to-digital conversion square wave signal and the VF voltage frequency or the IF current frequency (one of the two) in the external voltage synchronous acquisition circuit are respectively connected and output to two ordinary optocoupler isolators, and the isolation distance between the light-emitting end and the light-receiving end is about 5mm, and the isolation voltage is about 10KV. If the high voltage generated by the breakdown of the ball gap reaches 25KV or above, the ordinary optocoupler isolator cannot isolate such a high voltage. At present, optical fiber isolation devices are mostly used to isolate ultra-high voltage, but the optical fiber cable of the optical fiber isolation device is long, and an additional power supply is required to be powered separately, which is huge in size and not conducive to integrated circuit integration. Summary of the invention

[0004] The object of the present invention is to provide a protection method for an external voltage synchronous acquisition circuit used for a partial discharge withstand voltage test.

[0005] The external voltage synchronous acquisition circuit has a voltage input terminal Vin and a current input terminal Iin, and includes an A / D analog-to-digital conversion circuit, a VF voltage-frequency circuit and an IF current-frequency circuit. The input terminal of the A / D analog-to-digital conversion circuit and the input terminal of the VF voltage-frequency circuit are connected to the voltage input terminal Vin, and the input terminal of the IF current-frequency circuit is connected to the current input terminal Iin.

[0006] The method of the present invention connects the voltage amplitude signal output end of the A / D analog-to-digital conversion circuit, the frequency signal output end of the VF voltage-frequency circuit and the frequency signal output end of the IF current-frequency circuit to three signal input pins of a gating chip respectively, a single-chip microcomputer is connected to the control end of the gating chip, a signal output pin of the gating chip is connected to the input end of an optocoupler isolator, and an output end of the optocoupler isolator is connected to a partial discharge detection module.

[0007] The A / D analog-to-digital conversion circuit converts the Vin input voltage analog signal into a voltage amplitude digital square wave high and low level signal, and outputs it to the gating chip; the VF voltage-frequency circuit proportionally converts the Vin input voltage analog signal into a high and low level square wave frequency signal, and outputs it to the gating chip; the IF current-frequency circuit proportionally converts the Iin input current analog signal into a high and low level square wave frequency signal, and outputs it to the gating chip; the single-chip microcomputer controls the VF voltage-frequency circuit or the IF current-frequency circuit through the gating chip so that only one signal is turned on.

[0008] The optical coupler isolator is a high voltage resistant optical coupler isolator, the isolation distance between the light emitting end and the light receiving end is 35-37 mm, and the isolation voltage is 100KV.

[0009] In the present invention, the isolation distance between the light-emitting end and the light-receiving end of the optocoupler isolator is about 36 mm, and the isolation voltage can be as high as 100KV, while the isolation distance between the light-emitting end and the light-receiving end of the ordinary optocoupler isolator is only about 5 mm, and the isolation voltage is about 10KV. The single volume of the present invention is nearly 30 mm larger than that of the ordinary optocoupler isolator. In order to reduce the volume and facilitate integration, a gating chip is introduced to transmit the A / D digital square wave signal and the VF / IF frequency square wave signal in time periods in sequence, and only one signal is turned on each time, so that only one high-voltage resistant optocoupler isolator is needed, which greatly reduces the volume and facilitates the integration of the circuit. While reducing the volume and facilitating integration, the present invention ensures good isolation performance and anti-shock effect between the high and low voltages of the external synchronous voltage acquisition circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a hardware schematic diagram of the method of the present invention; Figure 2 This is a test flow chart of the present invention. DETAILED DESCRIPTION

[0011] The specific implementation of the method of the present invention is described below in conjunction with the accompanying drawings and embodiments.

[0012] like Figure 1As shown, the existing external voltage synchronous acquisition circuit has a voltage input terminal Vin and a current input terminal Iin, including an A / D analog-to-digital conversion circuit, a VF voltage-frequency circuit and an IF current-frequency circuit, the A / D analog-to-digital conversion circuit input terminal and the VF voltage-frequency circuit input terminal are connected to the voltage input terminal Vin, and the IF current-frequency circuit input terminal is connected to the current input terminal Iin. The method of the present invention connects the voltage amplitude signal output terminal of the A / D analog-to-digital conversion circuit, the frequency signal output terminal of the VF voltage-frequency circuit and the frequency signal output terminal of the IF current-frequency circuit to the three signal input pins of the gating chip respectively, the single-chip microcomputer is connected to the control terminal of the gating chip, the signal output pin of the gating chip is connected to the input terminal of the optocoupler isolator, and the output terminal of the optocoupler isolator is connected to the partial discharge detection module. The A / D analog-to-digital conversion circuit converts the Vin input voltage analog signal into a voltage amplitude digital square wave high and low level signal, and outputs it to the gating chip; the VF voltage-frequency circuit converts the Vin input voltage analog signal proportionally into a high and low level square wave frequency signal, and outputs it to the gating chip; the IF current-frequency circuit converts the Iin input current analog signal proportionally into a high and low level square wave frequency signal, and outputs it to the gating chip. The single-chip microcomputer controls the VF voltage-frequency circuit or the IF current-frequency circuit through the gating chip so that only one signal is turned on.

[0013] The first input pin of the gating chip is connected to the A / D analog-to-digital conversion circuit, the second input pin is connected to the VF voltage-frequency circuit, and the third input pin is connected to the IF current-frequency circuit; the three gating control pins of the gating chip are connected to the single-chip microcomputer, and the single-chip microcomputer controls the conduction or disconnection of the A / D analog-to-digital conversion circuit and the optical coupler isolator through the first gating control pin, controls the conduction or disconnection of the VF voltage-frequency circuit and the optical coupler isolator through the second gating control pin, and controls the conduction or disconnection of the IF current-frequency circuit and the optical coupler isolator through the third gating control pin. The single-chip microcomputer multiplexes the gating chip to realize the control of three input signals at one output port.

[0014] The optocoupler isolator adopts a high-voltage resistant optocoupler isolator. The isolation distance between the light-emitting end and the light-receiving end is 36mm, and the isolation voltage is 100KV.

[0015] like Figure 2 As shown, in the high-voltage withstand partial discharge test, the external voltage is collected synchronously. When the high voltage discharge occurs between the ball gaps, a high-voltage discharge shock of 25KV or above is generated. The high-voltage discharge shock enters the external voltage synchronous collection circuit, and the A / D voltage amplitude signal of the A / D conversion digital circuit, the voltage frequency square wave signal of the VF voltage-frequency conversion circuit, and the current frequency square wave signal of the IF current frequency conversion circuit arrive at the selection chip at the same time.

[0016] Step (1) The single chip microcomputer determines whether to collect the voltage frequency square wave signal according to the external instruction. If the voltage frequency square wave signal is collected, steps (2) to (4) are executed; otherwise, steps (5) to (7) are executed; Step (2) The single chip microcomputer conducts the voltage frequency square wave signal to the optocoupler isolator through the second strobe control pin, and stops collecting for 10 ms after the cumulative conduction time is 5 s; Step (3) The single chip microcomputer conducts the A / D voltage amplitude signal to the optocoupler isolator through the first strobe control pin, and stops collecting for 10 ms after the cumulative conduction is 5 s; Step (4) returns to step (2), the single chip microcomputer returns to switch to the strobe control pin 2, continues the VF voltage frequency conduction signal, and repeats this cycle until the current round of testing is completed; Step (5) The single chip microcomputer conducts the current frequency square wave signal to the optocoupler isolator through the third strobe control pin, and stops collecting for 10 ms after the cumulative conduction time is 5 s; Step (6) The single chip microcomputer conducts the A / D voltage amplitude signal to the optocoupler isolator through the first strobe control pin, and stops collecting for 10 ms after the cumulative conduction is 5 s; Step (7) returns to step (5), the single chip microcomputer returns to switch to the strobe control pin 3, continues the IF current frequency conduction signal, and repeats this cycle until the end of this round of experiments.

[0017] During normal operation, in the external voltage synchronous acquisition circuit, the high level voltage, low level voltage and ground voltage of the A / D analog-to-digital conversion circuit and the VF voltage-frequency conversion circuit or the IF current-frequency conversion circuit are 5V, 0V and 0V respectively. When the high voltage discharge occurs between the ball gaps, after the signal passes through the selection chip, the A / D analog-to-digital conversion digital signal and the IF current-frequency signal or the VF voltage-frequency signal and the ground voltage all increase by the same high voltage impact potential difference at the same time. For example, when the high voltage discharge impact is 20000V, the high level voltage, low level voltage and ground voltage of the A / D conversion digital circuit and the VF voltage-frequency conversion circuit or the IF current-frequency conversion circuit are 20005V, 20000V and 20000V respectively. At this time, the high level voltage at the input end of the high voltage resistant optocoupler isolator is 20005V, the low level voltage is 20000V, the ground voltage is 20000V, and the voltage drop across the light-emitting diode is still 5V. The high and low level voltages and ground voltage at the output end of the optocoupler isolator are still 5V, 0V and 0V. The voltage difference between the high and low level voltage and ground voltage at the input end of the high-voltage optocoupler isolator and the high and low level voltage and ground voltage at the output end is as high as 20000V. The insulation performance of ordinary optocoupler isolators is not strong and they are easily broken down, causing damage to electronic components and data loss. The high-voltage optocoupler isolator has an isolation distance of 36mm between the light-emitting end and the light-receiving end, and an isolation voltage of up to 100KVrms. It is very suitable for high-voltage isolation, so that the high-voltage circuit output by the gating circuit will not impact the partial discharge detection module of the optocoupler isolator.

[0018] At the same time, since the size of a single high-voltage optocoupler isolator increases due to the increase in the isolation distance between the light-emitting end and the light-receiving end, the use of a selection chip can reduce the original two high-voltage optocouplers to one optocoupler isolator, thereby reducing the total volume of the protection circuit and facilitating integrated circuit integration.

[0019] The present invention multiplexes the A / D analog-to-digital conversion digital signal of the external synchronous voltage acquisition, the VF voltage frequency conversion square wave signal, and the IF current frequency conversion square wave signal through the gate chip, and outputs three different signals in sequence to the same high-voltage optical coupler isolator at one output port, thereby reducing the volume of a piece of high-voltage optical coupler isolator. At the same time, the isolation distance between the light-emitting end and the light-receiving end of the high-voltage optical coupler isolator is 36mm, and the isolation voltage is as high as 100KV, replacing the existing ordinary optical coupler isolator, so that it can work normally under high-voltage impact environment, ensuring that while further reducing the integrated volume, the high-voltage impact resistance of the external synchronous voltage acquisition, the safety of the test and the data accuracy are improved.

Claims

1. A protection method for an external voltage synchronous acquisition circuit for a partial discharge withstand voltage test, wherein the external voltage synchronous acquisition circuit has a voltage input terminal Vin and a current input terminal Iin, and includes an A / D analog-to-digital conversion circuit, a VF voltage-frequency circuit and an IF current-frequency circuit, wherein the input terminal of the A / D analog-to-digital conversion circuit and the input terminal of the VF voltage-frequency circuit are connected to the voltage input terminal Vin, and the input terminal of the IF current-frequency circuit is connected to the current input terminal Iin; characterized in that: The voltage amplitude signal output end of the A / D analog-to-digital conversion circuit, the frequency signal output end of the VF voltage-frequency circuit, and the frequency signal output end of the IF current-frequency circuit are respectively connected to the three signal input pins of the gating chip, the single-chip microcomputer is connected to the control end of the gating chip, the signal output pin of the gating chip is connected to the input end of the optocoupler isolator, and the output end of the optocoupler isolator is connected to the partial discharge detection module; The A / D analog-to-digital conversion circuit converts the Vin input voltage analog signal into a voltage amplitude digital square wave high and low level signal, and outputs it to the gating chip; the VF voltage-frequency circuit proportionally converts the Vin input voltage analog signal into a high and low level square wave frequency signal, and outputs it to the gating chip; the IF current-frequency circuit proportionally converts the Iin input current analog signal into a high and low level square wave frequency signal, and outputs it to the gating chip; the single-chip microcomputer controls the VF voltage-frequency circuit or the IF current-frequency circuit through the gating chip so that only one signal is turned on; The optical coupler isolator is a high voltage resistant optical coupler isolator, the isolation distance between the light emitting end and the light receiving end is 35-37 mm, and the isolation voltage is 100KV.

2. The protection method for the external voltage synchronous acquisition circuit for partial discharge withstand voltage test according to claim 1, characterized in that: The first input pin of the gating chip is connected to the A / D analog-to-digital conversion circuit, the second input pin is connected to the VF voltage-frequency circuit, and the third input pin is connected to the IF current-frequency circuit; the three gating control pins of the gating chip are connected to the single-chip microcomputer, and the single-chip microcomputer controls the conduction or disconnection of the A / D analog-to-digital conversion circuit and the optical coupler isolator through the first gating control pin, controls the conduction or disconnection of the VF voltage-frequency circuit and the optical coupler isolator through the second gating control pin, and controls the conduction or disconnection of the IF current-frequency circuit and the optical coupler isolator through the third gating control pin; the single-chip microcomputer multiplexes the gating chip to realize the control of three input signals at one output port.

3. The protection method for the external voltage synchronous acquisition circuit for partial discharge withstand voltage test according to claim 2, characterized in that: In the high-voltage withstand partial discharge test, the external voltage is collected synchronously. When the high voltage discharge occurs between the ball gaps, a high-voltage discharge shock of 25KV or above is generated. The high-voltage discharge shock enters the external voltage synchronous collection circuit, and the A / D voltage amplitude signal of the A / D conversion digital circuit, the voltage frequency square wave signal of the VF voltage-frequency conversion circuit, and the current frequency square wave signal of the IF current frequency conversion circuit arrive at the selection chip at the same time; Step (1) The single chip microcomputer determines whether to collect the voltage frequency square wave signal according to the external instruction. If the voltage frequency square wave signal is collected, steps (2) to (4) are executed; otherwise, steps (5) to (7) are executed; Step (2) The single chip microcomputer conducts the voltage frequency square wave signal to the optocoupler isolator through the second strobe control pin, and stops collecting for 10 ms after the cumulative conduction time is 5 s; Step (3) The single chip microcomputer conducts the A / D voltage amplitude signal to the optocoupler isolator through the first strobe control pin, and stops collecting for 10 ms after the cumulative conduction is 5 s; Step (4) returns to step (2) until this round of experiments is completed; Step (5) The single chip microcomputer conducts the current frequency square wave signal to the optocoupler isolator through the third strobe control pin, and stops collecting for 10 ms after the cumulative conduction time is 5 s; Step (6) The single chip microcomputer conducts the A / D voltage amplitude signal to the optocoupler isolator through the first strobe control pin, and stops collecting for 10 ms after the cumulative conduction is 5 s; Step (7) returns to step (5) until this round of experiments is completed.

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