CN204190766U - The system that test low-voltage powerline carrier communication affects earth leakage protective device - Google Patents
The system that test low-voltage powerline carrier communication affects earth leakage protective device Download PDFInfo
- Publication number
- CN204190766U CN204190766U CN201420640336.XU CN201420640336U CN204190766U CN 204190766 U CN204190766 U CN 204190766U CN 201420640336 U CN201420640336 U CN 201420640336U CN 204190766 U CN204190766 U CN 204190766U
- Authority
- CN
- China
- Prior art keywords
- protective device
- earth leakage
- leakage protective
- carrier communication
- voltage powerline
- 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
- 230000001681 protective effect Effects 0.000 title claims abstract description 93
- 238000004891 communication Methods 0.000 title claims abstract description 62
- 238000012360 testing method Methods 0.000 title claims abstract description 46
- 230000008878 coupling Effects 0.000 claims abstract description 13
- 238000010168 coupling process Methods 0.000 claims abstract description 13
- 238000005859 coupling reaction Methods 0.000 claims abstract description 13
- 230000003321 amplification Effects 0.000 claims abstract description 8
- 238000003199 nucleic acid amplification method Methods 0.000 claims abstract description 8
- 230000006641 stabilisation Effects 0.000 claims description 4
- 238000011105 stabilization Methods 0.000 claims description 4
- 238000005516 engineering process Methods 0.000 description 7
- 238000010276 construction Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 4
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 230000007246 mechanism Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 230000008901 benefit Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002847 impedance measurement Methods 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
Landscapes
- Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
Abstract
The utility model provides a kind of system of testing low-voltage powerline carrier communication and affecting earth leakage protective device, comprising: signal generator, for generation of sinusoidal analog carrier signal; Power amplifier, is connected with signal generator, for sinusoidal analog carrier signal is carried out power amplification; Coupler, is connected with power amplifier, earth leakage protective device, for the sinusoidal analog carrier signal after power amplification being coupled, and the sinusoidal analog carrier signal after coupling is injected into tested earth leakage protective device; Load, is connected with earth leakage protective device; Decoupling circuit, is connected with earth leakage protective device, carries out decoupling for the sinusoidal analog carrier signal exported by earth leakage protective device, and the sinusoidal analog carrier signal after decoupling is injected into oscilloscope; Oscilloscope, is connected with described decoupling circuit, for showing the amplitude being injected into oscillographic sinusoidal analog carrier signal.This system achieves the test of the Electro Magnetic Compatibility of low-voltage powerline carrier communication and earth leakage protective device.
Description
Technical field
The utility model, about technical field of power systems, particularly about the compatible technique of carrier communication and electric power system, is a kind of system of testing low-voltage powerline carrier communication and affecting earth leakage protective device concretely.
Background technology
Power line carrier communication is the distinctive a kind of communication mode of electric power system, and its Internet resources utilizing electric power system natural realize data communication, has small investment, instant effect, the advantage such as synchronous with power grid construction.Voltage power-line carrier communication technology is a kind of specific communication mode of carrying out the transmission such as data or voice using low-voltage distribution wire (380V/220V power line) as information transmitting medium.At present, one of voltage power-line carrier communication technology Primary communication mode having become power user power consumption information acquisition system.
Whether this communication mode of voltage power-line carrier communication technology can have an impact to the power supply reliability of electric power system and the quality of power supply, is the problem that current each electric company is extremely concerned about.Concrete, after power information acquisition system puts into operation gradually, whether the operating state of earth leakage protective device can be affected the construction of the popularization that is directly connected to low-voltage powerline carrier communication mode and power information acquisition system.From grid side, earth leakage protective device is directly connected to power consumer power quality, and after power information acquisition system puts into operation gradually, the carrier communication that intelligent electric energy meter once occurred causes resident's earth leakage protective device that the phenomenon of tripping operation occurs.The construction of generation on the popularization of low-voltage powerline carrier communication mode and power information acquisition system of these problems causes very large impact.
Therefore, how according to operation principle and the technical characteristic of voltage power-line carrier communication technology and earth leakage protective device, testing the impact of low-voltage powerline carrier communication on earth leakage protective device, is this area technical barrier urgently to be resolved hurrily.
Utility model content
In order to overcome the above-mentioned technical problem existed in prior art, by analyzing operation principle and the technical characteristic of carrier communication and earth leakage protective device, in conjunction with Field Research and laboratory proofing test, the utility model provides a kind of system of testing low-voltage powerline carrier communication and affecting earth leakage protective device, by signal generator analog sine analog carrier signal, tested earth leakage protective device is tested, achieve the test of the Electro Magnetic Compatibility of low-voltage powerline carrier communication and earth leakage protective device, follow-up by contrast oscilloscope and signal generator multicarrier communication signal separately, and then the mechanism of the problems referred to above caused is analyzed.
The purpose of this utility model is, provides a kind of system of testing low-voltage powerline carrier communication and affecting earth leakage protective device, comprising: signal generator, for generation of sinusoidal analog carrier signal; Power amplifier, is connected with described signal generator, for described sinusoidal analog carrier signal is carried out power amplification; Coupler, is connected with described power amplifier, tested earth leakage protective device, for the sinusoidal analog carrier signal after power amplification being coupled, and the sinusoidal analog carrier signal after coupling is injected into tested earth leakage protective device; Load, is connected with described earth leakage protective device; Decoupling circuit, is connected with described earth leakage protective device, carries out decoupling for the sinusoidal analog carrier signal exported by described earth leakage protective device, and the sinusoidal analog carrier signal after decoupling is injected into oscilloscope; Described oscilloscope, is connected with described decoupling circuit, for showing the amplitude being injected into described oscillographic sinusoidal analog carrier signal.
Preferably, described test low-voltage powerline carrier communication also comprises the line impedance stabilization net work LISN be connected with described earth leakage protective device on the system that earth leakage protective device affects.
Preferably, described test low-voltage powerline carrier communication also comprises the transformer be connected with described LISN on the system that earth leakage protective device affects.
Preferably, described transformer is isolating transformer.
Preferably, described coupler is common mode coupler.
Preferably, described coupler is differential mode coupler.
Preferably, described oscilloscope is digital oscilloscope.
Preferably, described load is capacitive load and/or ohmic load and/or zero load.
The beneficial effects of the utility model are, by analyzing operation principle and the technical characteristic of carrier communication and earth leakage protective device, in conjunction with Field Research and laboratory proofing test, provide a kind of system of testing low-voltage powerline carrier communication and earth leakage protective device being affected, by signal generator analog sine analog carrier signal, tested earth leakage protective device is tested, achieve the test of the Electro Magnetic Compatibility of low-voltage powerline carrier communication and earth leakage protective device, follow-up by contrast oscilloscope and signal generator multicarrier communication signal separately, and then the mechanism of the problems referred to above caused is analyzed, for the popularization of low-voltage powerline carrier communication mode and the construction of power information acquisition system provide Data support.
For above and other object of the present utility model, feature and advantage can be become apparent, preferred embodiment cited below particularly, and coordinate institute's accompanying drawings, be described in detail below.
Accompanying drawing explanation
In order to be illustrated more clearly in the utility model embodiment or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only embodiments more of the present utility model, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.
What Fig. 1 provided for the utility model embodiment a kind ofly tests the structured flowchart of low-voltage powerline carrier communication on the execution mode one of the system that earth leakage protective device affects;
The structured flowchart of a kind of execution mode two tested in the system that low-voltage powerline carrier communication affects earth leakage protective device that Fig. 2 provides for the utility model embodiment;
The structured flowchart of a kind of execution mode three tested in the system that low-voltage powerline carrier communication affects earth leakage protective device that Fig. 3 provides for the utility model embodiment;
The low voltage power line carrier that Fig. 4 provides for the utility model affects on earth leakage protective device the circuit diagram that common mode injects test;
The low voltage power line carrier that Fig. 5 provides for the utility model affects on earth leakage protective device the circuit diagram that differential mode injects test.
Embodiment
Below in conjunction with the accompanying drawing in the utility model embodiment, be clearly and completely described the technical scheme in the utility model embodiment, obviously, described embodiment is only the utility model part embodiment, instead of whole embodiments.Based on the embodiment in the utility model, those of ordinary skill in the art are not making the every other embodiment obtained under creative work prerequisite, all belong to the scope of the utility model protection.
In prior art, whether this communication mode of voltage power-line carrier communication technology can have an impact to the power supply reliability of electric power system and the quality of power supply, is the problem that current each electric company is extremely concerned about.Concrete, after power information acquisition system puts into operation gradually, whether the operating state of earth leakage protective device can be affected the construction of the popularization that is directly connected to low-voltage powerline carrier communication mode and power information acquisition system.
For the problems referred to above, the utility model, by analyzing operation principle and the technical characteristic of voltage power-line carrier communication technology and earth leakage protective device, proposes a kind of system of testing the impact of low-voltage powerline carrier communication on earth leakage protective device.
What Fig. 1 provided for the utility model embodiment a kind ofly tests the structured flowchart of low-voltage powerline carrier communication on the execution mode one of the system that earth leakage protective device affects, and as shown in Figure 1, this system specifically comprises:
Signal generator 100, for generation of sinusoidal analog carrier signal;
Power amplifier 200, is connected with described signal generator 100, for described sinusoidal analog carrier signal is carried out power amplification;
Coupler 300, is connected with described power amplifier 200, tested earth leakage protective device 400, for the sinusoidal analog carrier signal after power amplification being coupled, and the sinusoidal analog carrier signal after coupling is injected into tested earth leakage protective device 400;
Load 500, is connected with described earth leakage protective device 400;
Decoupling circuit 600, is connected with described earth leakage protective device 400, carries out decoupling for the sinusoidal analog carrier signal exported by described earth leakage protective device, and the sinusoidal analog carrier signal after decoupling is injected into oscilloscope;
Described oscilloscope 700, is connected with described decoupling circuit, for showing the amplitude being injected into described oscillographic sinusoidal analog carrier signal.
Also be; in the system that the test low-voltage powerline carrier communication that the utility model provides affects earth leakage protective device; first produce sinusoidal analog carrier signal by signal generator, after being amplified by power amplifier, be injected in Device under test and earth leakage protective device after coupler coupling.By decoupling circuit, utilize oscilloscope to observe the actual carrier signal being injected into earth leakage protective device, observe the affected situation of earth leakage protective device.
The structured flowchart of a kind of execution mode two tested in the system that low-voltage powerline carrier communication affects earth leakage protective device that Fig. 2 provides for the utility model embodiment; as shown in Figure 2; in execution mode two, this system also comprises the line impedance stabilization net work LISN800 be connected with described earth leakage protective device.LISN (line impedance stabilization net work, Line ImpedanceStabilization Network) is an important auxiliary equipment in electric power system in electromagnetic compatibility test.It can isolate electrical network interference, provides stable Impedance measurement.
The structured flowchart of a kind of execution mode three tested in the system that low-voltage powerline carrier communication affects earth leakage protective device that Fig. 3 provides for the utility model embodiment; as shown in Figure 3; in execution mode three, this system also comprises the transformer 900 be connected with described LISN.In a particular embodiment, transformer can be isolating transformer.Isolating transformer and LISN can ensure that the power supply supplying tested earth leakage protective device is pure.
The low voltage power line carrier that Fig. 4 provides for the utility model affects on earth leakage protective device the circuit diagram that common mode injects test, and as shown in Figure 4, this specific embodiment is tested in carrier signal common mode injection situation, and coupler is common mode CND coupler.Coupling capacitance is over the ground connected, to verify the sensitivity of earth leakage protective device to high frequency Ground leakage current at earth leakage protective device live wire leading-out terminal.Shown in connection test circuit Fig. 4.
In this specific embodiment, the model of signal generator is Agilent 81150A, is 50k ~ 500kHz for generation of frequency range, and level is the sinusoidal analog carrier signal of 1V to the maximum;
The model of power amplifier is CBA1G-018:18W; 100kHz to 1GHz, amplifies for signal generator being exported analog carrier signal;
The pad value of common mode CDN is very little, is maximumly no more than 15dB, for the analog carrier signal exported through power amplifier is injected into earth leakage protective device input;
The model of isolating transformer is NDK-3000, and no-load voltage ratio is 1:1, and Main Function is kept apart at earth leakage protective device test macro and electrical network;
The model of LISN is NNB5, the network added between electrical network and Device under test, and this network can ensure that the power supply supplying earth leakage protective device is pure on the one hand, provides the line impedance that stable on the other hand in certain frequency range;
The model of digital oscilloscope is Agilent DS07104B, for showing the amplitude of the carrier signal that decoupling circuit exports.This signal is the high-frequency carrier signal being injected into earth leakage protective device actual size, makes comparisons, judge the coupling coefficient of CDN subsequently through the signal amplitude exported with signal generator.
Adjustment live wire coupling capacitance value over the ground, choose 10nF, 0.1uF, 0.2uF, 0.33uF, 0.5uF, 1uF, 10uF, discovery when coupling capacitance CL over the ground chooses be more than or equal to 0.33uF time, no matter whether have high-frequency interferencing signal to inject, leak and protect sky and hold and all can directly trip.Whether, when coupling capacitance CL is less than or equal to 0.05uF over the ground, no matter have high-frequency interferencing signal to inject, leakage guarantor sky is opened all does not have action.
Under resistive load condition, arranging power frequency loop current is 15A, after coupling capacitance CL chooses 0.2uF over the ground, is 250kHz in injected frequency, and power is that after the high-frequency interferencing signal 10s of 1W, earth leakage protective device trips.After removing high-frequency interferencing signal, earth leakage protective device trips, and proves that earth leakage protective device can be subject to the interference of high-frequency signal under the suitable condition of coupling capacitance over the ground, causes erroneous judgement tripping operation.
The low voltage power line carrier that Fig. 5 provides for the utility model affects on earth leakage protective device the circuit diagram that differential mode injects test, and as shown in Figure 5, this specific embodiment is tested in carrier signal differential mode injection situation, and coupler is differential mode CND coupler.Under load is zero load, capacitive load, inductive load three kinds of situations; Injection Signal is the simple signal of 100kHz ~ 500kHz respectively; injecting power is from 1mW ~ 10W; in three kinds of situations all there is not trip phenomenon in earth leakage protective device, and the electromagnetic interference of instruction book carrier only frequency range is not the main cause causing earth leakage protective device to trip.
In this specific embodiment, the model of signal generator is Agilent 81150A, is 50k ~ 500kHz for generation of frequency range, and level is the sinusoidal analog carrier signal of 1V to the maximum;
The model of power amplifier is CBA1G-018:18W; 100kHz to 1GHz, amplifies for signal generator being exported analog carrier signal;
The pad value of differential mode CDN is very little, is maximumly no more than 15dB, for the analog carrier signal exported through power amplifier is injected into earth leakage protective device input;
The model of isolating transformer is NDK-3000, and no-load voltage ratio is 1:1, and Main Function is kept apart at earth leakage protective device test macro and electrical network;
The model of LISN is NNB5, the network added between electrical network and Device under test, and this network can ensure that the power supply supplying earth leakage protective device is pure on the one hand, provides the line impedance that stable on the other hand in certain frequency range;
The model of digital oscilloscope is Agilent DS07104B, for showing the amplitude of the carrier signal that decoupling circuit exports.This signal is the high-frequency carrier signal being injected into earth leakage protective device actual size, makes comparisons, judge the coupling coefficient of CDN subsequently through the signal amplitude exported with signal generator.
In sum, by analyzing operation principle and the technical characteristic of carrier communication and earth leakage protective device, in conjunction with Field Research and laboratory proofing test, the utility model provides a kind of system of testing low-voltage powerline carrier communication and affecting earth leakage protective device, by signal generator analog sine analog carrier signal, tested earth leakage protective device is tested, achieve the test of the Electro Magnetic Compatibility of low-voltage powerline carrier communication and earth leakage protective device, follow-up by contrast oscilloscope and signal generator multicarrier communication signal separately, and then the mechanism of the problems referred to above caused is analyzed, for the popularization of low-voltage powerline carrier communication mode and the construction of power information acquisition system provide Data support.
Of the present utility model for protection point:
1, low-voltage powerline carrier communication signal affects test macro to earth leakage protective device, possesses the power of test under common and different mode such as mode;
2, the analog capability to capacitive load, zero load and resistive load is possessed;
3, the analog capability of Multi-carrier communication signal is possessed.
Those skilled in the art can also recognize that the various functions that the utility model embodiment is listed are the designing requirements realizing depending on specific application and whole system by hardware or software.Those skilled in the art for often kind of specifically application, can use the function described in the realization of various method, but this realization can should not be understood to the scope exceeding the protection of the utility model embodiment.
Apply specific embodiment in the utility model to set forth principle of the present utility model and execution mode, the explanation of above embodiment just understands method of the present utility model and core concept thereof for helping; Meanwhile, for one of ordinary skill in the art, according to thought of the present utility model, all will change in specific embodiments and applications, in sum, this description should not be construed as restriction of the present utility model.
Claims (8)
1. test the system that low-voltage powerline carrier communication affects earth leakage protective device, it is characterized in that, described test low-voltage powerline carrier communication comprises the system that earth leakage protective device affects:
Signal generator, for generation of sinusoidal analog carrier signal;
Power amplifier, is connected with described signal generator, for described sinusoidal analog carrier signal is carried out power amplification;
Coupler, is connected with described power amplifier, tested earth leakage protective device, for the sinusoidal analog carrier signal after power amplification being coupled, and the sinusoidal analog carrier signal after coupling is injected into tested earth leakage protective device;
Load, is connected with described earth leakage protective device;
Decoupling circuit, is connected with described earth leakage protective device, carries out decoupling for the sinusoidal analog carrier signal exported by described earth leakage protective device, and the sinusoidal analog carrier signal after decoupling is injected into oscilloscope;
Described oscilloscope, is connected with described decoupling circuit, for showing the amplitude being injected into described oscillographic sinusoidal analog carrier signal.
2. test low-voltage powerline carrier communication according to claim 1 system that earth leakage protective device is affected; it is characterized in that, described test low-voltage powerline carrier communication also comprises the line impedance stabilization net work LISN be connected with described earth leakage protective device on the system that earth leakage protective device affects.
3. the system that affects earth leakage protective device of test low-voltage powerline carrier communication according to claim 2, it is characterized in that, described test low-voltage powerline carrier communication also comprises the transformer be connected with described LISN on the system that earth leakage protective device affects.
4. the system that affects earth leakage protective device of test low-voltage powerline carrier communication according to claim 3, it is characterized in that, described transformer is isolating transformer.
5. the system that the test low-voltage powerline carrier communication according to claims 1 to 3 any one affects earth leakage protective device, is characterized in that, described coupler is common mode coupler.
6. the system that the test low-voltage powerline carrier communication according to claims 1 to 3 any one affects earth leakage protective device, is characterized in that, described coupler is differential mode coupler.
7. the system that the test low-voltage powerline carrier communication according to claims 1 to 3 any one affects earth leakage protective device, is characterized in that, described oscilloscope is digital oscilloscope.
8. the system that the test low-voltage powerline carrier communication according to claims 1 to 3 any one affects earth leakage protective device, is characterized in that, described load is capacitive load and/or ohmic load and/or zero load.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420640336.XU CN204190766U (en) | 2014-10-30 | 2014-10-30 | The system that test low-voltage powerline carrier communication affects earth leakage protective device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201420640336.XU CN204190766U (en) | 2014-10-30 | 2014-10-30 | The system that test low-voltage powerline carrier communication affects earth leakage protective device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN204190766U true CN204190766U (en) | 2015-03-04 |
Family
ID=52622733
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201420640336.XU Active CN204190766U (en) | 2014-10-30 | 2014-10-30 | The system that test low-voltage powerline carrier communication affects earth leakage protective device |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN204190766U (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104333400A (en) * | 2014-10-30 | 2015-02-04 | 国家电网公司 | System for testing impact of low-voltage power line carrier communication on electric leakage protector |
| CN110967578A (en) * | 2019-11-05 | 2020-04-07 | 天津绎迈科技有限公司 | Safe artificial power network circuit structure for electromagnetic compatibility pretesting |
-
2014
- 2014-10-30 CN CN201420640336.XU patent/CN204190766U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104333400A (en) * | 2014-10-30 | 2015-02-04 | 国家电网公司 | System for testing impact of low-voltage power line carrier communication on electric leakage protector |
| CN110967578A (en) * | 2019-11-05 | 2020-04-07 | 天津绎迈科技有限公司 | Safe artificial power network circuit structure for electromagnetic compatibility pretesting |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Song et al. | A novel busbar protection method based on polarity comparison of superimposed current | |
| CN105098985A (en) | System and method for identifying user change relationships in low-voltage power distribution based on power-frequency voltage distortion | |
| CN204119227U (en) | Intelligent electric meter carrier communication module test gimulator | |
| CN201707410U (en) | Digital dynamic simulation testing system of a simple bus difference protection device based on RTDS | |
| Huang et al. | Faulty feeder detection by adjusting the compensation degree of arc‐suppression coil for distribution network | |
| CN203276027U (en) | Digital dynamic closed-loop test system of electricity smooth and steady supply device | |
| CN204886424U (en) | System based on power frequency voltage distortion discernment low -voltage distribution family becomes relation | |
| CN102788903A (en) | Three-phase asymmetric power frequency parameter actual measuring method of high-voltage transmission line | |
| CN204190766U (en) | The system that test low-voltage powerline carrier communication affects earth leakage protective device | |
| CN104502861A (en) | Gaussian even pulse high-current high-power broadband power wire injection coupling network and construction method thereof | |
| CN104333400A (en) | System for testing impact of low-voltage power line carrier communication on electric leakage protector | |
| CN102788902A (en) | High-voltage transmission line power frequency parameter actual measuring device capable of resisting against high-induced voltage interference | |
| CN103412195B (en) | A kind of AMRS for detecting thunder and lightning environment and method | |
| Correa-Tapasco et al. | Robustness of a generalized impedance based fault locator considering distorted measurements | |
| CN103018571A (en) | Dual-coupling type on-line monitoring device of ground impedance of electric transmission line | |
| CN209570642U (en) | A kind of power cable crosstalk couplings test macro | |
| CN202975211U (en) | Photoelectric trigger device for transient disturbance test of transformer substation | |
| Chaudhary et al. | Challenges with harmonie compensation at a remote bus in offshore wind power plant | |
| CN204188724U (en) | A kind of on-line measurement device of electric power system surge protector insulation resistance | |
| CN205229368U (en) | Pollution flashover monitoring system | |
| CN204633468U (en) | A kind of area user identification zone device of multimode manner | |
| CN114675101A (en) | Fault arc protection electrical appliance characteristic test method | |
| CN202502175U (en) | Overvoltage transmission test system based on CVT | |
| CN205910290U (en) | Earth fault positioning device | |
| CN105353194A (en) | Voltage sampling device of three phase neutral point non-grounding system |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant |