CN212808568U - A ground fault detection device for alternating current-direct current sensor hybrid system - Google Patents
A ground fault detection device for alternating current-direct current sensor hybrid system Download PDFInfo
- Publication number
- CN212808568U CN212808568U CN202021421802.7U CN202021421802U CN212808568U CN 212808568 U CN212808568 U CN 212808568U CN 202021421802 U CN202021421802 U CN 202021421802U CN 212808568 U CN212808568 U CN 212808568U
- Authority
- CN
- China
- Prior art keywords
- acquisition module
- signal acquisition
- direct current
- signal
- ground
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Abstract
The utility model discloses a ground fault detection device for an AC/DC sensor hybrid system, which comprises a host and a signal acquisition module; the host computer includes: balanced and unbalanced bridge, variable bridge, synchronizing signal detection circuit, signal acquisition module communication interface. And the signal acquisition module is set to be in an alternating current sampling mode when the sensor carried by the signal acquisition module is in an alternating current CT (computed tomography), and is set to be in a direct current sampling mode when the sensor carried by the signal acquisition module is in a direct current CT. The utility model discloses can solve among the direct current system under the main screen and the used sensor non-uniform condition of branch screen, collect the technical problem of two kinds of CT detection function as an organic whole detection.
Description
Technical Field
The utility model relates to a direct current system's insulation detection technique.
Background
Insulation monitoring devices are generally divided into two parts from the point of view of detection: system insulation detection and branch fault detection. The system insulation detection generally applies the detection principle of a balanced bridge and an unbalanced bridge; the branch fault detection is divided into a leakage current detection method and an alternating current signal detection method. The leakage current detection method is a system for installing a direct current sensor (namely a direct current Hall sensor) on site, and the alternating current signal detection method is a system for installing an alternating current sensor on site. The detection device on the market detects a sensor on branch circuit fault, namely a signal acquisition module configured by the detection device detects either a direct current sensor or an alternating current sensor, and no module can set different detection modes.
The plant station direct current system is generally provided with a whole set of direct current screens (including a main screen and a sub-screen) by a manufacturer, and branch sensors carried by a factory are closed-loop sensors. Under the condition that the direct current screen can not be powered off in normal work, the closed-loop sensor can not be replaced. In the process of transforming the direct current screen of an old station, the situations that only the main screen is changed and the split screen is not changed or the split screen is added can be met, different manufacturers can possibly cause that the sensors used for the main screen and the split screen are not uniform, and the conventional method for the situation is to add corresponding opening sensors to all the split screens according to the detection scheme of the main direct current screen. The modification increases the operation risk of the direct current system, and increases additional hardware and labor cost, and the old stations lack related data due to the fact that the old stations are old and inconvenient to modify. Therefore, when the two sensors are used in a mixed manner on site in the reconstruction process, a user may wish to provide a detection device integrating two CT detection functions.
Disclosure of Invention
The utility model aims at providing a ground fault detection device for alternating current-direct current sensor hybrid system to under the main screen of solution direct current system and the used sensor non-uniform condition of branch screen, collect the technical problem of two kinds of CT detection function as an organic whole detection.
In order to achieve the above object, the present invention adopts the following technical solutions.
A ground fault detection device for an alternating current-direct current sensor hybrid system comprises a host and a signal acquisition module;
the host computer includes:
the balance and unbalance bridge is used for detecting the bus insulation value and providing two different states of leakage current for the direct current leakage current sensor;
a variable bridge for oscillating the bus voltage to ground at a constant frequency to generate a low frequency ac detection signal;
the synchronous signal detection circuit is used for detecting bus line-to-ground alternating current zero-crossing point signals;
the signal acquisition module communication interface is used for interacting with the signal acquisition module through the CAN port, sending synchronous information and branch information to be detected and receiving branch insulation calculation results;
the signal acquisition module:
acquiring and calculating CT induction signals fixedly arranged on each branch path and transmitting a calculation result to a signal acquisition module of a host through a CAN port; the signal acquisition module has an alternating current sampling circuit and a direct current sampling circuit, and can detect alternating current CT and direct current CT; when the sensor of the signal acquisition module is AC CT, the signal acquisition module is set to be AC sampling mode, and when the sensor of the signal acquisition module is DC CT, the signal acquisition module is set to be DC sampling mode.
The signal acquisition module comprises a multi-path selection switch which is connected with each path of CT input signals and selects one path to be sent to the selection switch, and the selection switch has AC/DC sampling mode output; when the sampling mode is direct current, the selection switch is selectively connected to the output a, filtered and amplified, and then sent to the A/D; when the sampling mode is AC, the sampling mode is selected to be connected to the output of b, and the sampling mode is transmitted to A/D after band-pass filtering, amplification, phase locking and integration; the digital signal after A/D conversion is sent to the processor, and when the host accesses the signal acquisition module, the signal acquisition module uploads the result to the host through the CAN.
The variable bridge is characterized in that two resistors are respectively added on the anode ground and the cathode ground of a bus, the on-off of the two resistors is controlled by two complementary PWM signals, and the access resistance value of the resistor can be equivalently changed by changing the duty ratio of PWM; when the duty ratio of the PWM wave is changed in a sinusoidal mode, the tap of the R slide rheostat also moves in a sinusoidal rule, and a sinusoidal signal is generated when the positive pole and the negative pole of the bus are opposite to the ground.
The utility model discloses an advantage and positive effect:
the utility model discloses an old station direct current system's direct current screen transformation provides a detection device that collects two kinds of CT and detect the function as an organic whole, has reduced direct current system's operational risk and extra hardware and cost of labor, has reduced the degree of difficulty of reforming transform.
Drawings
Fig. 1 is a schematic block circuit diagram of the present invention.
Fig. 2 is a differential bus voltage circuit diagram of the present invention.
Fig. 3 is a circuit diagram of a balanced and unbalanced bridge of the present invention.
Fig. 4-a is a circuit diagram of a variable bridge of the present invention.
Fig. 4-b is an equivalent circuit diagram of fig. 4-a.
Fig. 5 is a schematic block circuit diagram of the signal acquisition module of the present invention.
Detailed Description
A ground fault detection device for handing over, direct current sensor hybrid system, its circuit block diagram is shown with reference to fig. 1. The device comprises a host and a signal acquisition module. The host comprises a balanced and unbalanced bridge, a variable bridge, a synchronous signal detection circuit and a signal acquisition module communication interface. The balance and unbalance bridge is mainly used for detecting the bus insulation value and providing two different states for the direct current leakage current sensor to generate different leakage currents (the output current of the direct current leakage current sensor is changed when the positive and negative voltages to the ground of the bus are changed); the variable bridge is used for enabling the voltage of the bus to earth to fluctuate at a constant frequency so as to generate a low-frequency alternating current detection signal, and a branch with the ground can form a loop, so that an alternating current CT of the branch generates an induced current, as shown in the first figure: the dotted line of the red arrowhead is the flowing direction of the alternating current signal when the grounding exists; the synchronous signal detection circuit is used for detecting a zero-crossing point signal of bus line ground alternating current (a low-frequency alternating current detection signal generated by the variable bridge), and the zero-crossing point signal has the function of counteracting the influence of inductive and capacitive loads and other high-frequency alternating current signals on the system on detection; and the module communication interface is interacted with the signal acquisition module through the CAN port, sends synchronous information and branch information to be detected, and receives branch insulation calculation results.
The signal acquisition module is used for acquiring and calculating CT induction signals fixedly arranged on each branch circuit and transmitting a calculation result to the host through the CAN port. The circuit has an alternating current sampling circuit and a direct current sampling circuit, and can detect alternating current CT and direct current CT. When the sensor of the module is AC CT, the module is set to AC sampling mode, and when the sensor is DC CT, the module is set to DC sampling mode.
The utility model discloses the theory of operation:
under the automatic operation mode, insulating detection device host computer real-time supervision system busbar voltage and insulating condition: the host machine closes K1 and K2 of the unbalanced bridge, so that the balanced bridge is connected to a bus system, when the measured insulation is lowered, the host machine firstly disconnects K2, samples Uc (voltage deviation between positive and negative voltages of a bus and a ground), and issues a sampling starting instruction to a module in a direct current sampling mode through a CAN port, and the module samples leakage current I of CT carried by the module; and after all modules are sampled, the host closes K2, opens K1 and then samples Uc ', and tells the modules in the direct current sampling mode to sample the leakage current I' of the carried CT through the CAN port. As shown in the first drawing: when the voltage of the direct current bus line to the ground is unbalanced, the direct current CT generates leakage current, the leakage current in two sampling states is used for eliminating the influence of zero drift of the direct current CT on calculation, and the acquisition module calculates the grounding resistance of each branch according to the leakage current I and I' of each path and stores the grounding resistance in a processor. The host machine calculates insulation resistance values at two ends according to the bus voltage value and Uc', and automatically starts a branch inspection function once the calculated insulation value is reduced below a bus insulation threshold set value, wherein the host machine inputs a bridge-changing resistor and switches the bridge-changing resistor at a certain frequency to enable a bus to swing towards the ground voltage so as to generate a low-frequency signal with constant frequency, and automatically switches to a branch inspection interface, and simultaneously sends a sampling instruction to all modules in an alternating current sampling mode through a CAN port. And after all modules are sampled, the host accesses the modules in sequence according to the module serial numbers, and the accessed modules upload the calculated resistance values of all paths to the host through the CAN.
As shown in fig. 2, the voltage difference between the positive bus voltage and the negative bus voltage is sampled by: the positive and negative bus voltage is subtracted after following, and then the voltage is raised into positive voltage and sent to the A/D. Uc is the measured voltage of the circuit in the state that K1 of the unbalanced bridge is closed and K2 is open; uc' is the voltage measured by the circuit with K2 closed and K1 open for an unbalanced bridge.
As shown in fig. 3, for balanced and unbalanced bridges: k1 and K2 are balanced bridges when closed, and K1 and K2 are unbalanced bridges when working in turn.
As shown in fig. 4-a, 4-b, for a variable bridge: the variable bridge adopts the principle that two resistors are respectively added on the positive pole ground and the negative pole ground of a bus, the on-off of the two resistors is controlled by two complementary PWM signals, and the access resistance value of the resistor can be equivalently changed by changing the duty ratio of PWM.
The two paths of PWM signals are complementary signals, the circuit shown in figure 4-a can be equivalent to the circuit shown in figure 4-b, when the duty ratio of the PWM wave is changed in a sinusoidal mode, the tap of the R slide rheostat also moves in a sinusoidal mode, and a sinusoidal signal is generated when the positive pole and the negative pole of the bus face the ground.
I1＝DC_V+/R1*d
I2＝DC_V-/R2*(1-d)
Wherein: i is1Through a resistor R1Electric current
d-upper half bridge Q1Percentage of on time
DC_V+-bus barPositive electrode voltage to ground
I2Through a resistor R2Electric current
(1-d) -lower half-bridge Q2Percentage of on time
DC _ V- — bus negative voltage to ground
R1’＝DC_V+/I1＝R1/d
R2’＝DC_V-/I2＝R2/(1-d)
Let R1＝R2＝RR
Equivalent bridge anode resistance R1’＝RRD, equivalent bridge negative pole resistance R2’＝RR/(1-d)
DC_V+/DC_V-＝R1’/R2’＝(1-d)/d＝1/d-1
By changing d, DC _ V can be changed+And DC _ V-The proportion of V2 achieves the purpose of changing the voltage to earth of the positive and negative electrodes of the bus
Such a bridge in which the bus voltage is changed by changing the switching duty ratio d is a variable bridge.
The schematic block diagram of the signal acquisition module is shown in fig. 5: the multi-path selection switch selects one path from 16 paths of CT input signals and sends the selected path to the selection switch; the processor controls the selection switch to select which path of signal is connected to be output according to the sampling mode setting value, when the sampling mode is direct current, the selection switch is connected to the a output, the signal is filtered and amplified, and then the signal is sent to the A/D; when the sampling mode is AC, the output of b is selected to be connected, and the output is subjected to band-pass filtering, amplification, phase locking and integration and then sent to A/D; the digital signal after A/D conversion is sent to a processor for calculation, processing and storage, and when the host accesses the module, the module uploads the result to the host through the CAN.
Claims (3)
1. A ground fault detection device for an alternating current-direct current sensor hybrid system comprises a host and a signal acquisition module; it is characterized in that the preparation method is characterized in that,
the host computer includes:
the balance and unbalance bridge is used for detecting the bus insulation value and providing two different states of leakage current for the direct current leakage current sensor;
a variable bridge for oscillating the bus voltage to ground at a constant frequency to generate a low frequency ac detection signal;
the synchronous signal detection circuit is used for detecting bus line-to-ground alternating current zero-crossing point signals;
the signal acquisition module communication interface is used for interacting with the signal acquisition module through the CAN port, sending synchronous information and branch information to be detected and receiving branch insulation calculation results;
the signal acquisition module:
acquiring and calculating CT induction signals fixedly arranged on each branch path and transmitting a calculation result to a signal acquisition module of a host through a CAN port; the signal acquisition module has an alternating current sampling circuit and a direct current sampling circuit, and can detect alternating current CT and direct current CT; when the sensor of the signal acquisition module is AC CT, the signal acquisition module is set to be AC sampling mode, and when the sensor of the signal acquisition module is DC CT, the signal acquisition module is set to be DC sampling mode.
2. The ground fault detection device for the AC/DC sensor hybrid system according to claim 1, wherein the signal acquisition module comprises a multi-way selector switch connected with each CT input signal and selecting one way to send to the selector switch, and the selector switch has AC/DC sampling mode output; when the sampling mode is direct current, the selection switch is selectively connected to the output a, filtered and amplified, and then sent to the A/D; when the sampling mode is AC, the sampling mode is selected to be connected to the output of b, and the sampling mode is transmitted to A/D after band-pass filtering, amplification, phase locking and integration; the digital signal after A/D conversion is sent to the processor, and when the host accesses the signal acquisition module, the signal acquisition module uploads the result to the host through the CAN.
3. The ground fault detection device for the AC/DC sensor hybrid system according to claim 1, wherein the variable bridge is formed by adding two resistors to the positive ground and the negative ground of the bus respectively, the on and off of the two resistors are controlled by two complementary PWM signals, and the access resistance of the resistors can be equivalently changed by changing the duty ratio of PWM; when the duty ratio of the PWM wave is changed in a sinusoidal mode, the tap of the R slide rheostat also moves in a sinusoidal rule, and a sinusoidal signal is generated when the positive pole and the negative pole of the bus are opposite to the ground.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021421802.7U CN212808568U (en) | 2020-07-17 | 2020-07-17 | A ground fault detection device for alternating current-direct current sensor hybrid system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021421802.7U CN212808568U (en) | 2020-07-17 | 2020-07-17 | A ground fault detection device for alternating current-direct current sensor hybrid system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN212808568U true CN212808568U (en) | 2021-03-26 |
Family
ID=75103292
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202021421802.7U Active CN212808568U (en) | 2020-07-17 | 2020-07-17 | A ground fault detection device for alternating current-direct current sensor hybrid system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN212808568U (en) |
-
2020
- 2020-07-17 CN CN202021421802.7U patent/CN212808568U/en active Active
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN107957546A (en) | A kind of detection method and equipment of grid-connected inverters AC relay | |
| CN105203911B (en) | Three phase mains open phase fault detection method, device and a kind of automatic change-over | |
| CN103872759B (en) | The conversion method of discrimination of automatic transfer switching electric appliance controller and device | |
| CN105548719A (en) | Detection circuit and method of grounding insulation resistors | |
| CN101915884A (en) | Identification method of ground fault phases in three-phase ungrounded system and identification device thereof | |
| CN110739697B (en) | Low-voltage distribution network low-voltage treatment device and treatment method | |
| CN107526010A (en) | A kind of distributed small current earthing wire-selecting method based on double CT samplings | |
| US11114858B2 (en) | Bidirectional capacitor bank control | |
| CN105785133A (en) | Insulation resistance to ground detecting circuit, method and device for dual-path photovoltaic inverter | |
| CN201740840U (en) | Earth fault phase identification device in three-phase unearthed system | |
| CN109752648B (en) | On-load tap-changer switching arc energy on-line monitoring method and device | |
| CN212808568U (en) | A ground fault detection device for alternating current-direct current sensor hybrid system | |
| CN110579679A (en) | power distribution network line fault detection system based on negative sequence current vector analysis and detection method thereof | |
| CN112103915B (en) | Leakage protection method and system for mining variable-frequency driving system | |
| CN106291282A (en) | The insulation monitoring and warning device of a kind of dynamical system and method | |
| CN103439614A (en) | Electric power monitoring device and monitoring method | |
| CN112255571A (en) | Earth fault detection system with neutral point indirectly grounded | |
| CN102594157B (en) | Signal acquisition device and processing method for alternating current power current-sharing output system | |
| CN102539867B (en) | Smart phase volt ampere meter and measuring method thereof | |
| CN102082420B (en) | Longitudinal differential protection method of power transmission line | |
| CN207853843U (en) | Photovoltaic array ground insulation impedance detection circuit, device and non-isolated photovoltaic DC-to-AC converter | |
| CN108957187A (en) | A kind of test device of ac analog channel hardware | |
| CN102621373B (en) | Signal collection device and signal processing method of current-sharing input system of alternating-current power supply | |
| CN101282042A (en) | Impedance frequency eqmivalent value novel method for designing AC filter | |
| CN204732875U (en) | A kind of phase-lacking protective device |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant | ||
| GR01 | Patent grant |