CN201673216U - Online insulation monitoring instrument of group variable frequency motors - Google Patents
Online insulation monitoring instrument of group variable frequency motors Download PDFInfo
- Publication number
- CN201673216U CN201673216U CN2010201731779U CN201020173177U CN201673216U CN 201673216 U CN201673216 U CN 201673216U CN 2010201731779 U CN2010201731779 U CN 2010201731779U CN 201020173177 U CN201020173177 U CN 201020173177U CN 201673216 U CN201673216 U CN 201673216U
- Authority
- CN
- China
- Prior art keywords
- resistance
- voltage
- phase
- groups
- microprocessor
- 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.)
- Expired - Fee Related
Links
Images
Landscapes
- Control Of Ac Motors In General (AREA)
Abstract
The utility model discloses an online insulation monitoring instrument of group variable frequency motors. A group of resistors and a sampling resistor are connected in series to form a phase, three groups of resistors and three sampling resistors form three phases, the three sampling resistors are parallelly connected at one end to form manual simulation neutral grounding, and the three groups of resistors are connected to a secondary side of a neutral ungrounded power supply loop of a transformer or an input side of a public rectifier to lead in alternating current three-phase voltage. Three-phase leads are led out from the three groups of resistors and the three sampling resistors, the three-phase leads are respectively connected with three fuses, pass by three voltage insulation converters and three analog-to-digital converters to enter a microprocessor input passage, a microprocessor calculates, processes and compares three-phase voltage to ground, and inputs output results to a display or generates alarm signals, voltage-stabilized source is inputted by an alternating current power supply switch and the fuses, and voltage-stabilized source input is connected with the microprocessor, the analog-to-digital converters and the voltage insulation converters.
Description
Technical field
The utility model relates to a kind of drive motor of frequency converter in groups on-line insulation monitoring instrument.
Background technology
Along with frequency converter is widely used in commercial production, production efficiency and product quality have been improved.In order to raise the efficiency, reduce cost, commercial production generally adopts frequency converter drive motor in groups, is concentrated to this regional inverter supply by public rectifier, and every frequency converter can drive multiple electric motors according to technological requirement.But frequency conversion drive is also brought some negative effects, and the pwm pulse voltage build-up rate of frequency converter output is very high, produces voltage distribution unevenly on the motor winding, may produce the superpotential of nearly 2 times of higher-orders of oscillation at motor side; The harmonic current of output has increased the iron loss and the copper loss of motor, and motor temperature is risen, and electrical machine insulation is constituted a serious threat; And, influence its normal operation to the electromagnetic interference (EMI) of electrical equipment generation on every side.
According to reports, punctured because of the single-phase winding insulation of variable-frequency motor in actual field in service once repeatedly appearance, cause unit miscellaneous equipment speed and tension fluctuation, public rectifier output dc voltage, electric current big ups and downs, even electricity and the fault of damaging appear jumping, have a strong impact on the stable operation of unit grown place.At present, most commercial power system all adopts IT system, and promptly transformer neutral point is earth-free or through big impedance earth.In case when the advantage of this power supply mode is load generation singlephase earth fault,, can keeps and continue operation owing to do not constitute ground loop.But to get rid of earth point as early as possible, otherwise personal safety is threatened, in case and single-point grounding worsen and to develop into multiple spot simultaneously during ground connection, can cause this loop power supply to interrupt.So press for when motor or current supply circuit generation single-phase earthing, in time find the trouble spot, and excision in time, avoid fault to enlarge.
The online insulation tester of alternating-current variable frequency motor commonly used at present generally has following several method.
1, the ground connection measuring ability that utilizes the part frequency converter to provide is monitored the insulation of motor, and by detecting the frequency converter output current, in case the three-phase current deviate surpasses setting value, frequency converter judges that motor has grounding phenomenon.This detection method is easy to use at the scene; do not need to add any equipment; but detect effect and unreliable; when driving multiple electric motors for a frequency converter especially; when long or PWM switching frequency is higher when cable between motor and the frequency converter; through regular meeting's misoperation, thus the stable operation that influence is produced.In addition, it can not be simultaneously monitors the insulation of the interchange IT input mains side (being the earth-free power supply side of transformer neutral point) of giving inverter supply.
2, be connected in series the insulation that special-purpose zero sequence current mutual inductor comes monitoring motor by output at frequency converter.Because frequency converter output pwm pulse ripple produces common mode voltage at motor side, the zero-sequence current of corresponding generation some can't be used for distribution loop zero-sequence current detecting device commonly used on the market, needs special-purpose zero-sequence current to detect.When a frequency converter drives multiple electric motors, need special-purpose zero-sequence current detecting device of every motor configuration.This method is the insulation of on-line monitoring variable-frequency motor more exactly, and protection automatically.But also there is the problem that price is very high, need installing space in it; And it can not be simultaneously monitors the insulation of IT power supply side.
3, utilize Ben Deer (BENDER) series of products such as IRDH275 to monitor IT power supply side or separate unit variable-frequency motor insulation variation tendency, it can compare monitoring exactly to the insulation variation tendency.Its detection principle is the control by microprocessor, applies action of low-voltage pulse between tested loop and ground, calculates insulation resistance by detecting electric current, and when motor insulation against ground resistance was lower than setting value, detector was reported to the police or the output fault-signal.This product is applicable to the online insulation monitoring to IT supply side or separate unit motor, but when insulation monitoring is carried out in many variable-frequency motor loops, because of actual cable trend, length variations, the phenomenon that false alarm often occurs or do not report to the police.
4, adopt in the conventional earth-free current supply circuit the apparatus insulated method for monitoring of power frequency.In case principle is a power frequency equipment phase ground connection, this phase-to-ground voltage is zero, and other two phase-to-ground voltages voltage may rise to line voltage, comes surveillance insulation against ground situation by at the three-phase alternating-current supply input side three voltage tables being installed, referring to Fig. 1.This method to the ground insulation of power frequency equipment monitor effective, and can judge it is which phase ground connection; But to variable-frequency motor and inapplicable.Such as by public rectifier centrally connected power supply, when frequency converter drives multiple electric motors in groups, in case during certain variable-frequency motor generation single-phase earthing, one phase-to-ground voltage that the communication power supply side can't occur reduces, and other two phase-to-ground voltage rises to the phenomenon of line voltage, thereby occur failing to report alert or the phenomenon of not reporting to the police, and need artificial the supervision, can not real time monitoring and send and report to the police and trip signal.
5, adopt the voltage relay method, as shown in Figure 2, by a three-phase five-pole voltage transformer T, the star winding of its secondary side is connected to three voltage tables, and another Secondary Winding is connected into open-delta, inserts voltage relay.When exchanging input side generation ground connection, can produce residual voltage, the voltage relay action is sent and is reported to the police or trip signal, can judge it is which phase ground connection of power supply by three voltage tables.This method is fit to the insulation of power frequency equipment is monitored, but is not suitable for many variable-frequency motors are carried out insulation monitoring simultaneously.This is because during variable-frequency motor generation single-phase earthing, three phase-to-ground voltages of communication power supply side are symmetry still, the voltage ratio that induces in the opening winding side of three-phase five-pole voltage transformer is lower, is difficult for causing the voltage relay action, thereby alert phenomenon occurs failing to report.
In the IT ungrounded supply system,,, allow motor to continue operation owing to do not form ground loop when motor generation single-phase earthing; But if the motor multipoint earthing takes place, and must cause frequency converter two-phase or three-phase shortcircuit, huge short-circuit current makes converter plant protect tripping operation immediately.Although during variable-frequency motor phase ground connection, allow motor to continue operation, also there are some problems.On the one hand, because other two phase-to-ground voltage of motor rises to line voltage, when cable length or this frequency converter are with the multiple electric motors operation simultaneously between frequency converter and the motor, the distributed capacitance that relatively reaches between phase and phase is big, high-frequency PWM (width modulation) pulse voltage wave of frequency converter output causes the increase of frequency converter output current; On the other hand, because high-frequency leakage current produces the EMC(electromagnetic compatibility) problem, the normal operation of electrical equipment causes unit speed and tension fluctuation around the influence, causes public rectifier or contravarianter voltage, electric current big ups and downs and damages.In addition, in the IT ungrounded supply system,, easily personal safety is threatened in case the current supply circuit single-phase earthing takes place, in case and ground connection deterioration develop into multiple spot simultaneously during ground connection, can cause this loop power supply to interrupt.So press for when motor side or current supply circuit generation single-phase earthing, in time find the trouble spot, and excision in time, avoid fault to enlarge.
Summary of the invention
The purpose of this utility model is to provide a kind of on-line insulation monitoring of variable-frequency motor in groups instrument, the insulation against ground situation of many groups variable-frequency motor that this insulating monitoring instrument can drive all frequency converters by same public rectifier centrally connected power supply is carried out in-service monitoring, the detection effect is accurate, and do not need every motor is provided with insulation tester separately, and can carry out in-service monitoring to the insulation of power frequency supply side apparatus.
The utility model is achieved in that a kind of on-line insulation monitoring of variable-frequency motor in groups instrument, comprise three groups of resistance and three sample resistances, three voltage changers, three A/D converters, microprocessor and stabilized voltage supply, one group of resistance constitutes one mutually with a sample resistance series connection back, three groups of resistance and three sample resistance formation three-phases and three sample resistance one ends also connect composition manual simulation neutral ground, three groups of resistance connect and the secondary side of the earth-free current supply circuit of transformer neutral point or the input side of public rectifier through threephase switch, thereby introduce the interchange three-phase voltage of the earth-free current supply circuit of transformer neutral point; Between three groups of resistance and three sample resistances, draw three phase terminals, three phase terminals independently enter the microprocessor input channel by three A/D converters behind the voltage isolation transducer again through three after connecing three fuses respectively, microprocessor is by calculating and handle three phase-to-ground voltages, compare mutually then, output is input display or send alerting signal as a result; Stabilized voltage supply is imported behind switch and fuse by AC power, and stabilized voltage supply output connects microprocessor, A/D converter and voltage isolation transducer.
Described three groups of resistance have six resistance, and every group of resistance is two resistance series connection.
Insulating monitoring instrument of the present utility model is tested by three phase-to-ground voltages are imported in the interchange of IT ungrounded supply system (the earth-free or big impedance earth electric power system of warp of transformer neutral point); judge whether to exist variable-frequency motor ground connection or power frequency supply side grounding phenomenon to occur; send corresponding warning message according to the insulation against ground degree then, and can delay time as required and send compressor emergency shutdown and trip signal.Its advantage is:
1) the insulation against ground situation of many groups variable-frequency motor that can drive all frequency converters by same public rectifier centrally connected power supply is carried out in-service monitoring.
2) also can carry out in-service monitoring, and can judge which phase ground connection of three phase supply power supply the current supply circuit of same IT isolated neutral system and the insulation of power frequency motor.
3), send alerting signal to host computer or central control chamber immediately in case detect motor or there is grounding phenomenon in the power supply side.On the one hand, keep production and continue operation; On the other hand, so notification technique personnel inspection and eliminating in time is earth fault.
4) the utility model insulating monitoring instrument detects effect accurately, reliably, and does not need every motor is provided with insulation tester separately, has saved investment.
5) the utility model insulating monitoring instrument can be set the grounding alarm value as required, is suitable for the wide (AC220V～AC690V) of voltage range.
6) the utility model insulating monitoring instrument volume is little, not only can onlinely install and use, and also can be used as mobile device and uses.
Description of drawings
Fig. 1 is that prior art is installed the synoptic diagram that three voltage tables detect insulation against ground in the three phase supply loop;
Fig. 2 detects the synoptic diagram of insulation against ground by three-phase five-pole voltage transformer and cooperating of voltage relay for prior art;
Fig. 3 is for adopting the utility model synoptic diagram of variable-frequency motor on-line insulation monitoring instrument detection insulation against ground in groups.
Among the figure: R, S, T are R, S, the T phase (three-phase) of the input side of IT current supply circuit secondary side or public rectifier, R1, R2, R3 are the R phase resistance, S1, S2, S3 are the S phase resistance, T1, T2, T3 are the T phase resistance, K0 is a switch, K1 is a threephase switch, and F1, F2, F3, F4 are fuse, and IM is a variable-frequency motor.
Embodiment
The utility model is described in further detail below in conjunction with the drawings and specific embodiments.
Referring to Fig. 3, a kind of on-line insulation monitoring of variable-frequency motor in groups instrument comprises three groups of resistance and three sample resistances, three voltage changers, three A/D converters, microprocessor and stabilized voltage supplys.One group of resistance constitutes one mutually with a sample resistance series connection back, three groups of resistance and three sample resistance formation three-phases and three sample resistance one ends also connect composition manual simulation neutral ground, described three groups of resistance have six resistance, and every group of resistance is two resistance series connection; I.e. manual simulation's neutral ground of forming by resistance R 1, R2, R3, S1, S2, S3, T1, T2, T3 resistance.
Three groups of resistance through threephase switch K1 connect with former IT current supply circuit (be that transformer neutral point is earth-free or through the current supply circuit of big impedance earth, present embodiment is that example illustrates with the earth-free current supply circuit of transformer neutral point) secondary side or the input side of public rectifier, thereby introduce the interchange three-phase voltage of the earth-free current supply circuit of transformer neutral point; Between three groups of resistance R 1, R2, S1, S2, T1, T2 and three sample resistance R3, S3, T3, draw three phase terminals, by resistance R 1, R2, S1, S2, T1, T2 step-down, the resistance of R1, R2, S1, S2, T1, T2 value respectively is 200K Ω, and sample resistance R3, S3, T3 resistance value respectively are 10K Ω; Three phase terminals are drawn and are independently isolated with former ac voltage circuit behind the voltage isolation transducer through three after sampling voltage meets three fuse F1, F2, F3 respectively, enter the microprocessor input channel by three A/D converters again, microprocessor is by calculating and handle three phase-to-ground voltages, compare then, output is input display or send alerting signal as a result.
If three phase-to-ground voltages of being sampled are simultaneously all than normal three phase-to-ground voltage height, judge that then there is grounding phenomenon in the motor side that frequency converter is controlled, and differentiate the single-phase insulation against ground deterioration condition of variable-frequency motor according to the size of the three phase-to-ground voltage amplitudes of being sampled.When three phase-to-ground voltage amplitudes differ bigger, wherein a phase-to-ground voltage is lower, when other two phase-to-ground voltages raise simultaneously, can judge that then there are the single-phase earthing phenomenon in IT Alternating Current Power Supply side or power frequency motor, here the power frequency motor directly is connected on IT Alternating Current Power Supply side (being IT ac power supply circuit secondary side), referring to the dotted line coupling part among Fig. 3; Also can judge IT ac power supply circuit or the single-phase insulation against ground deterioration condition of power frequency motor according to three phase-to-ground voltage amplitude sizes.Send the single-phase earthing alerting signal then, send alerting signal to host computer or central control room by the communication machine; Also can send the tripping operation request instruction to host computer or central control room's time-delay according to the insulation degradation situation.
Stabilized voltage supply is imported behind K switch 0 and fuse F4 by AC power 220V, ac/dc conversion through stabilized voltage supply inside, stabilized voltage supply output direct current 5V, ± 15V, ± the 24V stabilized voltage supply provides working power for microprocessor, A/D converter and voltage isolation transducer.
The real data that variable-frequency motor on-line insulation monitoring instrument of the present utility model is applied in the production practices can be referring to table 1.All motors that unit moves back in the cold rolling company of certain enterprise drive by inverter, distinguish according to technology, give the inverter centrally connected power supply by entrance and two public rectifiers of outlet section.Adopt variable-frequency motor on-line insulation monitoring instrument of the present utility model respectively entrance and two public rectifiers of outlet section to be monitored, public rectifier three phase-to-ground voltages of entrance are obviously higher, and judging in the motor that entrance controlled by the inverter of public rectifier centrally connected power supply has motor ground connection.By checking that there is a motor ground connection in this frequency converter loop of certain discovery, after this ground connection motor was taked insulation processing, this rectifier three-phase alternating current primary voltage recovered normal value, and unit also recovers stable operation, referring to the data of table 1.
During variable-frequency motor on-line insulation monitoring instrument of the present utility model is mainly used in, the low-voltage variable frequency device, be suitable for voltage range between exchanging 220 volts to 690 volts, can realize by parameter setting and reseting module according to on-the-spot needs, also can use the dedicated line plate, make it be applied to more voltage levels loop.
Variable-frequency motor on-line insulation monitoring instrument of the present utility model detect effect accurately, reliable, and same IT current supply circuit only need be provided with a monitor, volume is little, low price uses but also can make mobile device, has popularization and application space widely.
Claims (2)
1. variable-frequency motor on-line insulation monitoring instrument in groups, it is characterized in that: comprise three groups of resistance and three sample resistances, three voltage changers, three A/D converters, microprocessor and stabilized voltage supply, one group of resistance constitutes one mutually with a sample resistance series connection back, three groups of resistance and three sample resistance formation three-phases and three sample resistance one ends also connect composition manual simulation neutral ground, three groups of resistance connect and the secondary side of the earth-free current supply circuit of transformer neutral point or the input side of public rectifier through threephase switch, thereby introduce the interchange three-phase voltage of the earth-free current supply circuit of transformer neutral point; Between three groups of resistance and three sample resistances, draw three phase terminals, three phase terminals independently enter the microprocessor input channel by three A/D converters behind the voltage isolation transducer again through three after connecing three fuses respectively, microprocessor is by calculating and handle three phase-to-ground voltages, compare mutually then, output is input display or send alerting signal as a result; Stabilized voltage supply is imported behind switch and fuse by AC power, and stabilized voltage supply output connects microprocessor, A/D converter and voltage isolation transducer.
2. the on-line insulation monitoring of variable-frequency motor in groups instrument according to claim 1 is characterized in that: described three groups of resistance have six resistance, and every group of resistance is two resistance series connection.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010201731779U CN201673216U (en) | 2010-04-28 | 2010-04-28 | Online insulation monitoring instrument of group variable frequency motors |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010201731779U CN201673216U (en) | 2010-04-28 | 2010-04-28 | Online insulation monitoring instrument of group variable frequency motors |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN201673216U true CN201673216U (en) | 2010-12-15 |
Family
ID=43330628
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2010201731779U Expired - Fee Related CN201673216U (en) | 2010-04-28 | 2010-04-28 | Online insulation monitoring instrument of group variable frequency motors |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN201673216U (en) |
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102628915A (en) * | 2012-03-28 | 2012-08-08 | 中国海洋石油总公司 | Electrical submersible pump on-line insulation detection device |
| CN102914688A (en) * | 2011-08-01 | 2013-02-06 | 冠捷投资有限公司 | Electronic system, device with voltage detecting and warning functions, and voltage detection circuit |
| CN102944810A (en) * | 2012-12-12 | 2013-02-27 | 湖南省电力公司科学研究院 | Test device for secondary circuit zero line site of voltage transformer |
| CN102955100A (en) * | 2011-08-18 | 2013-03-06 | 现代摩比斯株式会社 | Device for detecting failure of motor coil in breaking system for vehicle and method thereof |
| CN105353194A (en) * | 2015-11-30 | 2016-02-24 | 广东电网有限责任公司梅州供电局 | Voltage sampling device of three phase neutral point non-grounding system |
| CN105486974A (en) * | 2015-12-31 | 2016-04-13 | 北京合康亿盛变频科技股份有限公司 | Grounding detection circuit and method for stator winding end of motor |
| CN105717837A (en) * | 2016-02-26 | 2016-06-29 | 王静爽 | Motor shutdown on-line insulation monitoring control method |
| CN109444635A (en) * | 2018-11-15 | 2019-03-08 | 珠海格力电器股份有限公司 | A kind of equipment ground real time monitoring apparatus |
| CN111256860A (en) * | 2020-02-11 | 2020-06-09 | 雅砻江流域水电开发有限公司 | Reliable operation method of temperature control box of single-phase air-cooled transformer |
| CN111650542A (en) * | 2020-07-07 | 2020-09-11 | 国电大渡河瀑布沟发电有限公司 | Detection device and method for preventing slow fusing of generator set terminal voltage transformer fuse |
| CN113138308A (en) * | 2020-01-17 | 2021-07-20 | 宝山钢铁股份有限公司 | Remote real-time monitoring system for insulation state of roller way motor in IT power supply system |
-
2010
- 2010-04-28 CN CN2010201731779U patent/CN201673216U/en not_active Expired - Fee Related
Cited By (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102914688A (en) * | 2011-08-01 | 2013-02-06 | 冠捷投资有限公司 | Electronic system, device with voltage detecting and warning functions, and voltage detection circuit |
| CN102955100A (en) * | 2011-08-18 | 2013-03-06 | 现代摩比斯株式会社 | Device for detecting failure of motor coil in breaking system for vehicle and method thereof |
| CN102628915B (en) * | 2012-03-28 | 2014-04-16 | 中国海洋石油总公司 | Electrical submersible pump on-line insulation detection device |
| CN102628915A (en) * | 2012-03-28 | 2012-08-08 | 中国海洋石油总公司 | Electrical submersible pump on-line insulation detection device |
| CN102944810A (en) * | 2012-12-12 | 2013-02-27 | 湖南省电力公司科学研究院 | Test device for secondary circuit zero line site of voltage transformer |
| CN105353194B (en) * | 2015-11-30 | 2017-12-22 | 广东电网有限责任公司梅州供电局 | The voltage sampling apparatus of three-phase isolated neutral system |
| CN105353194A (en) * | 2015-11-30 | 2016-02-24 | 广东电网有限责任公司梅州供电局 | Voltage sampling device of three phase neutral point non-grounding system |
| CN105486974A (en) * | 2015-12-31 | 2016-04-13 | 北京合康亿盛变频科技股份有限公司 | Grounding detection circuit and method for stator winding end of motor |
| CN105486974B (en) * | 2015-12-31 | 2019-02-19 | 北京合康新能科技股份有限公司 | Detect the circuit and method of the stator winding end ground connection of motor |
| CN105717837A (en) * | 2016-02-26 | 2016-06-29 | 王静爽 | Motor shutdown on-line insulation monitoring control method |
| CN109444635A (en) * | 2018-11-15 | 2019-03-08 | 珠海格力电器股份有限公司 | A kind of equipment ground real time monitoring apparatus |
| CN113138308A (en) * | 2020-01-17 | 2021-07-20 | 宝山钢铁股份有限公司 | Remote real-time monitoring system for insulation state of roller way motor in IT power supply system |
| CN111256860A (en) * | 2020-02-11 | 2020-06-09 | 雅砻江流域水电开发有限公司 | Reliable operation method of temperature control box of single-phase air-cooled transformer |
| CN111650542A (en) * | 2020-07-07 | 2020-09-11 | 国电大渡河瀑布沟发电有限公司 | Detection device and method for preventing slow fusing of generator set terminal voltage transformer fuse |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN201673216U (en) | Online insulation monitoring instrument of group variable frequency motors | |
| CN108169615B (en) | Optical CT-based phase failure detection method for starting standby transformer | |
| CN103779965B (en) | Integrated high-voltage AC circuit-breaker controller | |
| US8014111B2 (en) | Method and device for preventing fire caused by defects in electric circuits and arrangements | |
| CN103840437B (en) | The quick diagnosis of power distribution network ferromagnetic resonance and singlephase earth fault and processing method | |
| CN106841883A (en) | Reactor method for monitoring operation states in high-voltage power capacitor complexes | |
| KR20120053606A (en) | Incoming and distributing panel with zero-phase harmonic active filter | |
| CN208571394U (en) | A kind of photovoltaic power generation box-type substation based on intelligent controller | |
| CN213151719U (en) | Power supply control circuit and power supply cabinet for motor no-load test | |
| CN111679163A (en) | On-line insulation monitoring device for turns of dry-type reactor | |
| CN105717426A (en) | Insulation monitoring device and method capable of preventing buses from misoperation | |
| CN110888086A (en) | Circuit electric leakage detection positioning system based on signal injection | |
| CN212433321U (en) | On-line insulation monitoring device for turns of dry-type reactor | |
| CN203012082U (en) | Insulation detector | |
| CN105425066A (en) | Special capacitor ripple current detection main circuit for flexible direct-current power transmission | |
| CN109031043A (en) | Based on instantaneous power Sudden Changing Rate half-wavelength transmission line of alternation current fault phase-selecting method | |
| CN101364726B (en) | Earthing fault detection and control method for electromagnetic stirring system | |
| CN104749453A (en) | Method for reducing influences imposed on user voltage sag by external grid single-phase grounding fault | |
| CN207424155U (en) | Power failure detection device | |
| CN206878468U (en) | A kind of reactive power compensator with fault electric arc detection function | |
| CN201845038U (en) | Electrical leakage tester for three-phase three-wire IT (information technology) system | |
| CN101435843B (en) | Method for recognizing short circuit fault of power distribution network by dynamically regulating over current fixed value | |
| CN206378536U (en) | A kind of high efficiency security appliance performance test equipment | |
| CN109188191A (en) | Based on chugging amount half-wavelength transmission line of alternation current fast failure phase-selecting method | |
| CN216485322U (en) | Power cable fault burn-through position finder |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20101215 Termination date: 20160428 |