CN220040715U - Ground fault monitoring system of direct current system of transformer substation - Google Patents
Ground fault monitoring system of direct current system of transformer substation Download PDFInfo
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Abstract
The utility model discloses a transformer substation direct current system ground fault monitoring system, which comprises a transformer substation direct current system ground fault detection device and an upper computer, wherein the transformer substation direct current system ground fault detection device comprises a current and voltage detection module, a power supply module, a central processing unit, a low-frequency signal source and an amplifying circuit; the power supply module is used for supplying power, the current and voltage detection module, the low-frequency signal source and the upper computer are connected with the central processing unit, and the low-frequency signal source is connected with the amplifying circuit. The utility model constructs the grounding fault detection device based on the direct current system of the transformer substation through reasonable constitution and connection, further builds a man-machine interaction hardware platform through the grounding fault detection device based on the direct current system of the transformer substation and the upper computer, and can rapidly position a fault branch and give an alarm when the direct current system of the transformer substation has insulation or grounding faults, so that an maintainer can timely process the fault position, and an important guarantee is provided for reliable operation of the transformer substation.
Description
Technical Field
The utility model relates to a transformer substation direct current system ground fault monitoring system, and belongs to the technical field of power monitoring system design.
Background
The transformer substation direct current system mainly comprises a charging module, a storage battery, an online insulation monitoring system, a direct current feeder line and the like, and a load adopts a radiation type power supply mode to provide a stable and reliable direct current power supply for a protection device, a signal loop, a control loop, a communication system and the like in the substation. The direct current system is an independent power supply, is not influenced by a generator, station service electricity and a system operation mode, is powered on by a storage battery under the condition of external alternating current interruption, and is an emergency device in the power system. Meanwhile, the system has important functions of power supply control, protection, adjustment and the like for the power system and has important functions of monitoring and maintaining power supply, so that reliable operation of the station direct current system plays a vital role in long-term stable operation of the transformer substation. At present, as a large and complex direct current power supply network is formed by a plurality of branch networks, a plurality of connected devices and other factors, the direct current power supply network is distributed layer by layer, the loops are complex, the cost of manual inspection and the probability of occurrence of faults of the direct current system are objectively increased, and faults such as ground faults of the direct current system exist all the time and occur in the running process of the direct current system.
In view of the above problems, there is a need for a system for monitoring a ground fault of a direct current system of a transformer substation, which can accurately detect the insulation level of a branch and locate the feeder branch with an insulation fault when the fault occurs, so as to provide timely and efficient information support for operation and maintenance management personnel. And the construction of the ground fault monitoring system of the direct current system of the transformer substation needs to consider the constitution and connection of the system.
Disclosure of Invention
The utility model provides a substation direct current system ground fault monitoring system, which is based on a substation direct current system ground fault detection device and an upper computer, and can reduce the working intensity and difficulty brought by the traditional manual operation and maintenance inspection, and provide timely and efficient information support for operation and maintenance management staff.
The technical scheme of the utility model is as follows: the system comprises a substation direct current system ground fault detection device and an upper computer, wherein the substation direct current system ground fault detection device comprises a current and voltage detection module, a power supply module, a central processing unit, a low-frequency signal source and an amplifying circuit; the power supply module is used for supplying power, the current and voltage detection module, the low-frequency signal source and the upper computer are connected with the central processing unit, and the low-frequency signal source is connected with the amplifying circuit.
The current and voltage detection module comprises a current sensor, a voltage sensor, a filter and an A/D conversion module; the current sensor and the voltage sensor are respectively connected with the A/D conversion module through the filter and connected with the central processing unit through the A/D module; the central processing unit communicates with the upper computer through RS 485.
The current sensor adopts an ACS70331 type current sensor, the voltage sensor adopts an LTC2057HVIS8# PBF type voltage sensor, the filter adopts a MEM1608P50R0T001 type filter, and the A/D conversion module adopts a MAX11612EUA+T type A/D converter; the ACS70331 type current sensor and the LTC2057HVIS8# PBF type voltage sensor are used for collecting current and voltage data, two IP+ pins and two IP-pins of the ACS70331 type current sensor are respectively connected in parallel, and a VIOUT pin of the ACS70331 type current sensor is connected into a MEM1608P50R0T001 type filter as an input signal of current sampling; the pins V+ and V-of the LTC2057HVIS8# PBF type voltage sensor are respectively connected with +20V and-20V power supplies, the pins IN+ and IN-are differential input ends, the OUT pin is connected with the MEM1608P50R0T001 type filter, and the outputs of the two parts of filters are connected with the MAX11612EUA+T type A/D converter, namely AIN0 and AIN1 pins respectively.
The beneficial effects of the utility model are as follows: the utility model constructs the grounding fault detection device based on the substation direct current system through reasonable constitution and connection, further builds a man-machine interaction hardware platform through the grounding fault detection device based on the substation direct current system and the upper computer, and can rapidly position the fault branch and give an alarm when the substation direct current system has insulation or grounding faults, so that an maintainer can timely process the fault position, the direct current system can recover to stably operate in a short time, and important guarantee is provided for reliable operation of the substation.
Drawings
FIG. 1 is a block diagram of the structure of the present utility model;
FIG. 2 is a circuit diagram of an unbalanced bridge of the present utility model;
FIG. 3 is a schematic diagram of the circuit of the present utility model;
fig. 4 is a schematic diagram of a circuit of the present utility model.
Detailed Description
The utility model will be further described with reference to the drawings and examples, but the utility model is not limited to the scope.
Example 1: 1-4, the transformer substation direct current system ground fault monitoring system comprises a transformer substation direct current system ground fault detection device and an upper computer, wherein the transformer substation direct current system ground fault detection device comprises a current and voltage detection module, a power supply module, a central processing unit, a low-frequency signal source and an amplifying circuit; the power supply module is used for supplying power, the current and voltage detection module, the low-frequency signal source and the upper computer are connected with the central processing unit, and the low-frequency signal source is connected with the amplifying circuit.
Further, the current and voltage detection module comprises a current sensor, a voltage sensor, a filter and an A/D conversion module; the current sensor and the voltage sensor are respectively connected with the A/D conversion module through the filter and connected with the central processing unit through the A/D module; the central processing unit communicates with the upper computer through RS 485.
Further, the current sensor adopts an ACS70331 type current sensor, the voltage sensor adopts an LTC2057HVIS8# PBF type voltage sensor, the filter adopts a MEM1608P50R0T001 type filter, and the A/D conversion module adopts a MAX11612EUA+T type A/D converter; the ACS70331 type current sensor and the LTC2057HVIS8# PBF type voltage sensor are used for collecting current and voltage data, two IP+ pins and two IP-pins of the ACS70331 type current sensor are respectively connected in parallel, and a VIOUT pin of the ACS70331 type current sensor is connected into a MEM1608P50R0T001 type filter as an input signal of current sampling; the pins V+ and V-of the LTC2057HVIS8# PBF type voltage sensor are respectively connected with +20V and-20V power supplies, the pins IN+ and IN-are differential input ends, the OUT pin is connected with the MEM1608P50R0T001 type filter, and the outputs of the two parts of filters are connected with the MAX11612EUA+T type A/D converter, namely AIN0 and AIN1 pins respectively.
As shown in fig. 2, which is a circuit diagram of an unbalanced bridge, the insulation condition of the dc system to the ground is monitored by a double asymmetrical bridge. A resistor Rq and a switch K are arranged between the unbalanced bridge and the ground, the resistor Rq is used for collecting the voltage value to the ground, the voltage difference value is used for judging the insulation condition of the direct current system to the ground, the switch K is closed only when fault detection is needed, and the other conditions are all in an open state, so that the voltage value to the ground can be obtained when fault detection is not neededWhen the insulation detection device is used or the insulation detection device breaks down, the unbalanced bridge is isolated from the direct current system, and the insulation of the direct current system is not affected. R in FIG. 2 + ，R - Respectively represent the insulation resistance between the anode and the cathode of the direct current system and the ground, R 1 、R 2 And R is q Is bridge resistance, R 1 ≠R 2 U is the voltage between the positive electrode and the negative electrode, the resistance values of the two R1 are the same, the resistance values of the two R2 are the same, U q Is R q And a voltage on the same. Obtained by derivation, R + //R - ＝UR q (R 2 -R 1 )(U q1 -U q2 )(R 1 +R 2 )。R + //R - Reflecting the insulation condition of the DC system to the ground, and indicating that the DC system is abnormal to the ground at the moment once the insulation resistance value is smaller than 20kΩ. Whether the insulation resistance value of the positive bus is reduced, the insulation resistance value of the negative bus is reduced, or the insulation of the positive bus and the negative bus is reduced simultaneously, the collected U can be used for detecting the current q1 、U q2 Substituting the above value to calculate the parallel value R of the ground resistance + //R - Size, and thus the ground state. For the voltage U between the positive bus and the negative bus, the voltage value U between the positive bus and the ground is calculated by sampling respectively + Negative bus voltage to ground value U - Then according to the formula u= |u + |+|U - And I is calculated.
As shown in fig. 1, the structure block diagram of the ground fault detection device of the substation direct current system is shown, and the working principle is as follows: first, the voltage sensor in the current and voltage detecting part detects the voltage value U of the positive bus to the ground + Negative bus voltage to ground value U - And bridge resistance R q U on q1 (switch K closed repositioning 1), U q2 (the switch K is closed to the position 2) and is transmitted to the ARM central processing unit to calculate the parallel value of the direct current system to the ground resistance, and if the insulation resistance value is abnormal (less than 20kΩ), the ground resistance value is judged; and otherwise, finishing the detection of the grounding fault of the direct current system of the transformer substation. If the signal is grounded, immediately starting the low-frequency signal source to generate a low-frequency voltage signal injected into positive and negative buses of the direct-current system, amplifying the low-frequency voltage signal by an amplifying circuit, and loading the low-frequency voltage signal into the direct-current systemAnd the situation that the branch low-frequency current generated when the low-frequency voltage generated by the low-frequency signal source is directly loaded on the positive and negative buses of the direct-current power grid is too weak so as to be submerged in noise interference is avoided. Then sampling branch current signals by taking current transformers embedded at the top ends of all branches in a current and voltage detection part as detection elements, and collecting voltage amplitude U loaded on positive and negative buses of a direct current power grid by a low-frequency signal source through the voltage transformers + And U - The voltage signal is used for extracting the sampled low-frequency current signal, the voltage amplitude U+, U-and the low-frequency voltage signal to an ARM central processing unit by using wavelet transformation as characteristics, respectively obtaining the amplitude of the low-frequency voltage, the phase of the sampling starting moment and the phase and amplitude of the low-frequency resistive current with the positive electrode grounded and the negative electrode grounded at the same sampling moment, obtaining the grounding resistance value of each branch according to ohm law, comparing the grounding resistance value with a grounding resistance standard 20k omega, judging that the branch has a grounding fault if the grounding resistance value is smaller than or equal to 20k omega, and sending an alarm signal and displaying the grounding branch number; otherwise, returning to the step of starting the low-frequency signal source to detect the ground fault of the next branch.
As shown in fig. 3, the current sensor adopts ACS70331, can realize 10mA high-precision mA-level current measurement, and the maximum measurement current is 20mA, so as to measure the low-frequency alternating current signal of the branch current. The signals collected by the sensor are firstly sent into a low-pass filter to eliminate noise and high-frequency interference signals, and then sent into an A/D conversion channel to be subjected to analog-digital conversion. The voltage sensor realizes the collection of bus voltage, positive bus voltage to ground and negative bus voltage to ground by utilizing a differential operational amplifier circuit, the high voltage is sent to the positive end and the negative end of the operational amplifier by a differential resistor, the operational amplifier outputs a weak voltage signal proportional to the input voltage, and the signal is sent to an A/D conversion channel after filtering treatment. For acquisition of current-voltage analog signals, 1 piece of 16bit high-speed high-precision A/D conversion chip is adopted to realize precise sampling of bus voltage and branch current, and the voltage sampling range is-5V. And analyzing and processing the received digital signals through the ARM center processing unit, and if the initial insulation fault detection of the direct current system is judged to be grounded, controlling the low-frequency signal source to detect the branch grounding fault by the ARM center processing unit. The selected low-frequency signal source is a trigonometric function generator, namely, the output is a sine or cosine voltage signal; the frequency value range is generally between 10Hz and 30Hz, and 30Hz is selected, so that the frequency value range is required to be accurate and stable and does not deviate along with time; the amplitude of the low frequency signal source should be kept constant (typically 5V) to facilitate accurate calculation of the ground resistance. And finally, uniformly transmitting the judging result of the ARM center processing unit to a liquid crystal display screen through a serial port communication machine, namely displaying a ground fault branch and corresponding alarm information on a ground fault detection and positioning system of the direct current system of the transformer substation, and carrying out fault alarm on information sent by operation and maintenance personnel through the system.
As shown in fig. 3, the ACS70331 type current sensor and the LTC2057hvis8# PBF type voltage sensor, whose output signals are analog signals, measure the current and the voltage of the circuit to be measured, the two ip+ pins and the two IP-pins of the ACS70331 type current sensor are respectively connected in parallel, and the VIOUT pin of the ACS70331 type current sensor is connected to the MEM1608P50R0T001 type filter as the input signals of current sampling; the pins V+ and V-of the LTC2057HVIS8# PBF type voltage sensor are respectively connected with +20V and-20V power supplies, the pins IN+ and IN-are differential input ends, the OUT pin is connected with a MEM1608P50R0T001 type filter, and the outputs of the two parts of filters are connected with a MAX11612EUA+T type A/D converter, namely AIN0 pin and AIN1 pin respectively; the output pins SDA and SCL of the A/D converter are respectively connected to pins PA1 and PA2 of STM32F103C8T6, and analysis results are transmitted to pins DB0, DB1, DB2, DB3, DB4, DB5, DB6 and DB7 of the liquid crystal display screen LCM1602K-FL-YBW through pins PB3, PB4, PB5, PB6, PB8, PB9 and PB 15. The MAX11612EUA+T type A/D converter needs to be connected with a +5V power supply. STM32F103C8T6 has ARMCortex-M372 MHzMSL=3 core, its pin PC14-OSC32_IN and PC15-OSC32_OUT access external RTC crystal oscillator circuit (generally connect 32.768 kHz), pin PD0-OSC_IN and PD0-OSC_OUT access external system crystal oscillator (generally connect 8 MHz), pin VBAT connects power +3.3V, pin BOOT0 connects system start-up circuit. The V0 pin of the LCM1602K-FL-YBW is connected with a contrast adjusting voltage.
As shown in FIG. 4, the low-frequency signal is obtained through a D/A converter, the utility model adopts an 8-bit DAC chip MX722KN+ with latch to realize the function, the digital value of each step sine function is stored in a table in advance, when the low-frequency signal source is injected, the low-frequency signal source is sequentially taken out through a table look-up method, and the corresponding waveform voltage can be obtained after the D/A conversion. The digital inputs are given by PA [8:13], PB [13:14] of STM32F103C8T 6; wr# of MX7226kn+ is connected at pin PB0 of STM32F103C8T 6; the VSS pin is connected to the HEADER plug-in connector and is connected to [ -5V, +5V ] power supply; the pin VOUTC is a low-frequency voltage signal output by the D/A, and the low-frequency voltage signal with lower amplitude through the operational amplifier LM324S is loaded on the positive and negative buses of the direct current system after power amplification and boost conversion.
By applying the technical scheme, the utility model adopts the equipment with the selected model and has the following characteristics: high-precision measurement: the use of LTC2057hvis8# PBF, ACS70331 can provide high accuracy voltage and current measurements. Multifunctional microcontroller: STM32F103C8T6 is a powerful microcontroller, has abundant peripheral equipment and processing capacity, and can be used for tasks such as data processing, communication and control; through using STM32F103C8T6 microcontroller, the user can program and function expansion as required for detection device more nimble adaptation different application demands. And a display module: the LCM1602K-FL-YBW is a 16x2 character liquid crystal display module that can be used to display measurement results and other relevant information, providing an intuitive user interface. Reliability and stability: the selected element has good reliability and stability, and can provide stable performance under long-term operation and various environmental conditions.
While the present utility model has been described in detail with reference to the drawings, the present utility model is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present utility model within the knowledge of those skilled in the art.
Claims (3)
1. The system for monitoring the grounding fault of the direct current system of the transformer substation is characterized by comprising a grounding fault detection device of the direct current system of the transformer substation and an upper computer, wherein the grounding fault detection device of the direct current system of the transformer substation comprises a current and voltage detection module, a power supply module, a central processing unit, a low-frequency signal source and an amplifying circuit; the power supply module is used for supplying power, the current and voltage detection module, the low-frequency signal source and the upper computer are connected with the central processing unit, and the low-frequency signal source is connected with the amplifying circuit.
2. The substation direct current system ground fault monitoring system according to claim 1, wherein the current voltage detection module comprises a current sensor, a voltage sensor, a filter, an a/D conversion module; the current sensor and the voltage sensor are respectively connected with the A/D conversion module through the filter and connected with the central processing unit through the A/D module; the central processing unit communicates with the upper computer through RS 485.
3. The substation direct current system ground fault monitoring system according to claim 2, wherein the current sensor is an ACS70331 type current sensor, the voltage sensor is an LTC2057HVIS8# PBF type voltage sensor, the filter is a MEM1608P50R0T001 type filter, and the a/D conversion module is a MAX11612eua+t type a/D converter; the ACS70331 type current sensor and the LTC2057HVIS8# PBF type voltage sensor are used for collecting current and voltage data, two IP+ pins and two IP-pins of the ACS70331 type current sensor are respectively connected in parallel, and a VIOUT pin of the ACS70331 type current sensor is connected into a MEM1608P50R0T001 type filter as an input signal of current sampling; the pins V+ and V-of the LTC2057HVIS8# PBF type voltage sensor are respectively connected with +20V and-20V power supplies, the pins IN+ and IN-are differential input ends, the OUT pin is connected with the MEM1608P50R0T001 type filter, and the outputs of the two parts of filters are connected with the MAX11612EUA+T type A/D converter, namely AIN0 and AIN1 pins respectively.
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