CN103197195A - Detecting method and detecting system for multipoint earthing of voltage second loop neutral conductor network - Google Patents
Detecting method and detecting system for multipoint earthing of voltage second loop neutral conductor network Download PDFInfo
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Abstract
The invention discloses a detecting method for multipoint earthing of a voltage second loop neutral conductor network. The method comprises the steps: selecting at least one current injecting point from the voltage second loop neutral conductor network, and injecting a first current from the at least one current injecting point; detecting a current near a permanent earth point in the voltage second loop neutral conductor network to obtain a second current; comparing a difference value of the second current and the first current with a preset threshold value, and if the difference value is within the preset threshold value, confirming that the multipoint earthing exists in the voltage second loop neutral conductor network; and positioning each earthing point according to a topological structure of the voltage second loop neutral conductor network. The invention further discloses a detecting system for the multipoint earthing of the voltage second loop neutral conductor network. According to the scheme, whether the multipoint earthing exists in the voltage second loop neutral conductor network or not can be detected.
Description
Technical field
The application relates to the power technology field, particularly a kind of detection method and system of voltage secondary circuit neutral line network multipoint earthing.
Background technology
In the power technology field; usually with the equipment (as generator, transformer and the power transmission and distribution line of force etc.) of production, conversion, conveying, distribution electric energy; and the equipment (as motor, electric furnace, relay protection and control device etc.) that uses electric energy, and even the same integral body that energy management system is formed is called electric system.The composition of electric system can be divided into primary system (or primary circuit) and electrical secondary system (or secondary circuit) according to function difference: the former undertakes power delivery and allocating task; the latter is used for primary system (or primary circuit) is monitored, controls, measures and task such as protection; equipment in primary system is called primary equipment, and the equipment in electrical secondary system is called secondary device.Usually have connection device between primary circuit in the electric system and the secondary circuit, voltage transformer (VT) namely is this equipment for contact primary circuit and secondary circuit.Outside voltage transformer (VT), with its formation loop of connecting with devices such as measuring scale, can realize monitoring and management to the primary circuit.This secondary circuit that comprises voltage transformer (VT) is called the voltage secondary circuit.
In order to guarantee the operate as normal of voltage secondary circuit; the neutral line network of voltage secondary circuit must keep nonvolatil ground connection; and can only have this earth point; if other earth points except continuous earth point; to cause that circuit zero-sequenceprotection malfunction in the other direction, connection become accidents such as protection malfunction and pilot protection malfunction, cause significant impact.
Yet, although the earth point of voltage secondary circuit neutral line network is so important for secondary voltage circuit, but in actual application, except at the beginning of the wiring of voltage secondary circuit, can connect the phenomenon of avoiding occurring multipoint earthing by noting circuit, better detection method at voltage secondary circuit neutral line multipoint earthing in the operation of power networks process, also occur.
Summary of the invention
For solving the problems of the technologies described above, the embodiment of the present application provides a kind of voltage secondary circuit neutral line network multipoint earthing detection method and corresponding system thereof, to realize the detection to multipoint earthing, guarantees the safety of voltage secondary circuit.
The detection method of the voltage secondary circuit neutral line network multipoint earthing that the embodiment of the present application provides comprises:
Select at least one electric current decanting point at voltage secondary circuit neutral line network, inject first electric current from this at least one electric current decanting point; Detect near the electric current of continuous earth point of voltage secondary circuit neutral line network, obtain second electric current; Difference and the pre-set threshold value of described second electric current and described first electric current are compared, if described difference in pre-set threshold value, is then determined at voltage secondary circuit neutral line network internal storage at multipoint earthing; Locate each earth point according to voltage secondary circuit neutral line topology of networks.
Preferably, describedly select at least one electric current decanting point to be specially at voltage secondary circuit neutral line network:
Determine the neutral line of voltage secondary circuit neutral line network;
At least one decanting point of selecting at the described neutral line is as the electric current decanting point.
Preferably, inject first electric current from least one electric current decanting point and inject by direct supply or low-frequency ac power, described low-frequency ac power is frequency less than 1 hertz AC power.
Further preferably, described direct supply is the dc pulse current source, and near the electric current the continuous earth point of described detection voltage secondary circuit neutral framework detects by the difference measurement method, and described difference measurement method is for measuring the poor of pulse high level and reference level.
Further preferably, set the threshold limit value of the output current of direct supply or low-frequency ac power, when direct supply or low-frequency ac power output current surpass threshold limit value, with described threshold limit value as first electric current that injects the electric current decanting point.
The embodiment of the present application also provides a kind of detection system of voltage secondary circuit neutral line network multipoint earthing.This system comprises: signal generator and detecting device, and the storer that stores voltage secondary circuit neutral line topology of networks, wherein:
Described signal generator, at least one the electric current decanting point that is used for selecting at voltage secondary circuit neutral line network injects first electric current;
Described detecting device comprises current measurement device, comparer and counter, described current measurement device is for detection of the electric current of the continuous earth point annex of voltage secondary circuit neutral line network, to obtain second electric current, described comparer is used for difference and the pre-set threshold value of described second electric current and described first electric current are compared, if described difference is in pre-set threshold value, determine then at voltage secondary circuit neutral line network internal storage that at multipoint earthing described counter is used for calculating according to voltage secondary circuit neutral line topology of networks determines each earth point.
Preferably, described signal generator comprises power supply, and described power supply is direct supply or frequency less than 1 hertz low-frequency ac power.
Further preferably, described signal generator also comprises the limit value element, and when the output current of direct supply or low-frequency ac power surpassed threshold limit value, signal generator was with first electric current of described threshold limit value as injection electric current decanting point.
The embodiment of the present application is selected at least one electric current decanting point at voltage secondary circuit neutral line network earlier, inject electric current from this decanting point, detect electric current then near the continuous earth point of voltage secondary circuit neutral line network, if the difference between detected electric current and the injection electric current is outside preset range, then determine voltage secondary circuit neutral line network internal storage at multipoint earthing, and then can be according to voltage secondary circuit neutral line topology of networks compute location to each earth point.The embodiment of the present application provides detection method and the detection system of the many earth points of a kind of secondary circuit of voltage easily neutral line network, solved the problem of secondary circuit earth point detection difficulty after in a single day transformer station puts into operation, fill up domestic and international blank in this field, guaranteed the stable and safety of electric system.
Description of drawings
In order to be illustrated more clearly in the embodiment of the present application or technical scheme of the prior art, to do to introduce simply to the accompanying drawing of required use in embodiment or the description of the Prior Art below, apparently, the accompanying drawing that describes below only is some embodiment that put down in writing among the application, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain other accompanying drawing according to these accompanying drawings.
Fig. 1 is voltage secondary circuit neutral line network multipoint earthing testing circuit schematic diagram;
Fig. 2 is the application's voltage secondary circuit neutral line network multipoint earthing testing process figure;
The voltage secondary circuit neutral line network structure that Fig. 3 detects transformer station for the application;
Fig. 4 (a) is that the structure of the signal generator of voltage secondary circuit neutral line network multipoint earthing detection system is formed synoptic diagram;
Fig. 4 (b) is that the structure of the detecting device of voltage secondary circuit neutral line network multipoint earthing detection system is formed synoptic diagram.
Embodiment
In order to make those skilled in the art person understand technical scheme among the application better, below in conjunction with the accompanying drawing in the embodiment of the present application, technical scheme in the embodiment of the present application is clearly and completely described, obviously, described embodiment only is the application's part embodiment, rather than whole embodiment.Based on the embodiment among the application, those of ordinary skills are not making the every other embodiment that obtains under the creative work prerequisite, all should belong to the scope of the application's protection.
The application's main thought is: the difference at the voltage secondary circuit neutral line injects little electric current, detects the electric current situation of change of continuous earth point, determines whether to exist other earth points except continuous earth point with this.Following elder generation briefly introduces this injection ratio juris.
Referring to Fig. 1, the figure shows the schematic diagram that multipoint earthing detects.A, B, C, D are several places contact in the branch road of neutral line network in the figure, R1, and R2, R3 are respectively the resistance of three section leads in the branch road, and D is the continuous earth point, and R is at the second earth point stake resistance.Generally, each neutral line of transformer substation voltage secondary circuit forms a network that interconnects, at the pulpit one point earth.When having and only having an earth point in the neutral spider lines, arbitrarily a bit inject electric current between over the ground from this neutral framework, according to Kirchhoff's current law (KCL), the electric current that flows into continuous earth point should be identical with the current value that injects, if there are differences, then the somewhere has parasitic earth point (i.e. the earth point of other except continuous earth point) to cause shunting in the middle of the explanation.Based on such principle, the injection current distributions according to the relevant neutral return path of neutral line network structure detection can find out parasitic earth point.
Such as: A point over the ground (earth point) inject small electric current I, (single-point grounding) earth lead AB section of flowing through under normal circumstances, the electric current of BC section and CD section equates, all be the electric current I of injection.But in branch road, there is the earth point C except continuous earth point D.In this case, the stake resistance R that exists between C and ground will play shunting action, thereby make the electric current of the earth lead CD section of flowing through must be less than the electric current I of injecting.Therefore, as long as detect the AB that flows through, BC, the electric current of CD section also compares with the electric current that injects, and can find impermanent earth point.
Referring to Fig. 2, the figure shows the embodiment of detection method of the application's voltage secondary circuit neutral line multipoint earthing.This embodiment comprises:
Step S201: select at least one electric current decanting point at voltage secondary circuit neutral line network;
The electric current decanting point can be selected according to actual conditions on voltage secondary circuit neutral line network, and the selection of two kinds can be arranged usually: the one, select at the neutral line of voltage secondary circuit neutral line network; The 2nd, select at the phase voltage line of voltage secondary circuit neutral line network.The embodiment of the present application is preferably selected the electric current decanting point at the neutral line, reason is: if select the phase voltage line, inject power supply and may bring error to the measurement of secondary device, special when electric network fault, because voltage transformer secondary voltage reduces, injecting the constant measuring error that will make of power supply increases greatly, in addition, testing apparatus endangers very big if fault will cause the voltage circuit short circuit.
Step S202: inject first electric current from this at least one electric current decanting point;
After determining good decanting point, need to inject electric current by this point to the voltage secondary circuit, need consider to adopt which kind of power supply to inject electric current when injecting electric current, generally, can adopt direct supply, frequency is less than 1 hertz low-frequency ac power or other power supplys, but different electrical power has different characteristics: for direct supply, because it can solve the measuring error that drift brings, it is less to the measuring accuracy influence, from reducing the signal injection to the angle of the influence of secondary equipment in power system, the Chang Zuowei power supply pay the utmost attention to object, but it also may influence its magnetic characteristic.When selecting direct supply for use, can further select the dc pulse current source, the dc pulse current source can produce some direct current signals and pulse signals such as 10mA, 100mA.Under the situation that adopts the dc pulse current source, can adopt the difference measurement method to the detection method of voltage secondary circuit, so-called difference measurement method refers to measure the high Horizon of pulse and the difference of reference level.Also need to prove: no matter adopting direct supply still is the power supply of other classifications, because being added in the load of big impedance, current source may produce high voltage, the safety and stability that is unfavorable for electrical secondary system, therefore, the application is also preferably increasing the limit value protecting component on the power supply or between power supply and decanting point, the maximum current that setting is injected to decanting point, when namely the injection electric current that provides when power supply is less than the highest threshold values set, the electric current injection of adopting power supply to provide; The injection electric current that provides when power supply adopts this highest threshold values as the electric current that injects to decanting point, thereby guarantees safety during more than or equal to the highest threshold values set.
Step S203: detect near the electric current of continuous earth point of voltage secondary circuit neutral line network, obtain second electric current;
Step S204: difference and the pre-set threshold value of described second electric current and described first electric current are compared, if described difference in pre-set threshold value, is then determined at voltage secondary circuit neutral line network internal storage at multipoint earthing;
Step S205: locate each earth point according to voltage secondary circuit neutral line topology of networks.
For the technique effect of the embodiment of the present application is described, the applicant has carried out two tests: the one, test its effect in the method that the transformer station that do not put into operation utilizes above-mentioned multipoint earthing to detect; The 2nd, test its effect in the method that the transformer station that has moved utilizes above-mentioned multipoint earthing to detect.Narration respectively below.
Show that a seated connection line improves but the voltage secondary circuit neutral framework synoptic diagram of the 220kV transformer station that also do not put into operation for first kind of test: Fig. 3.Such other the test under, be divided into three kinds of situations:
One of situation is the test that whether voltage secondary circuit neutral framework is existed multipoint earthing when nominal situation.The neutral framework of transformer station has and has an earth point under the nominal situation.Under situation, select following 5 representative point A, B, C, D, E, F as the electric current decanting point, the electric current that injects is the 10mA pulse current, and table 1 has been listed near the current value decanting point annex and the continuous earth point, and split ratio (split ratio=continuous earth point electric current/decanting point electric current):
Table 1: the test data of voltage secondary circuit neutral framework under nominal situation
As seen from the above table, when each representative point injects the 10mA pulse current source, electric current difference between decanting point and the continuous earth point is in the 0.1mA scope, split ratio maintains in 1%, namely under nominal situation, inject electric current even if be chosen in the different decanting points of neutral framework, the split ratio that records all levels off to 0, keeps constant relatively.Can be shown by this result: if the split ratio ultimate value of selecting the different decanting points of voltage secondary circuit neutral framework to record is all identical, illustrate that then there is not multipoint earthing in this voltage secondary circuit neutral framework, has and only have a some reliable ground.
Two of situation is the tests that whether voltage secondary circuit neutral framework existed multipoint earthing when some metallic earthing point of manual simulation.In this case, manual simulation's metallic earthing point is selected A, C, D, E, F point successively, the electric current decanting point is selected from the B point at the female voltage transformer (VT) terminal box of continuous earth point 110kV II farthest place, inject the 10mA pulse current source at this point, detect the electric current at decanting point, second earth point and continuous earth point place.Test result is as shown in table 2: (annotate: for ease of comparing, the test result when having listed " normally " in the table, what is called " normally " refer to not have second earth point except continuous earth point.)
Table 2: some metallic earthing point test datas of manual simulation
As seen from the above table, when second earth point that occurs in the voltage secondary circuit neutral framework except continuous earth point, the current value of continuous earth point and the current value of decanting point present than large deviation, split ratio is bigger, and the position distribution of the concrete numerical value of split ratio and decanting point, two earth points between distance have relation.Shown by this result: in actual application, in order to strengthen the accuracy of detection, can increase decanting point test multi-group data more and compare analysis, if the bigger situation of split ratio difference, then have the possibility of multipoint earthing.
Three of situation is the tests that whether voltage secondary circuit neutral framework existed multipoint earthing when some nonmetal character earth point of manual simulation.In this case, the nonmetal character earth point is by forming through 10 Ω resistance from the female voltage transformer (VT) terminal box of continuous earth point 110kV II farthest B o'clock, inject the 100mA pulse current as the electric current decanting point respectively at other representative points (B, F, A, D, E point), detect decanting point, second earth point and continuous earth point electric current.It is as shown in table 3 to record the result:
Table 3: manual simulation's nonmetal character earth point test data record sheet
By the data in the analytical table 3 as can be known, first: be under the nonmetal character ground connection situation at second earth point, be the metal earth point than earth point, detection sensitivity will be affected, because the shunting action of second earth point of nonmetal character ground connection is littler than metallic earthing, second: constant current source decanting point position is the closer to second earth point, shunts more greatly, and it is more good to detect effect.The 3rd: the stake resistance of nonmetal character ground connection is more little, shunts more obviously, and it is more good to detect effect, changes to 5 Ω such as the resistance with second earth point by 10 Ω, does identical test, and the shunting of second earth point will be more obvious.
Can also find by above-mentioned test, adopt pulse constant current mode and split-core type meter to detect with the method for difference, because being conducive to eliminate the influence of " souvenir drift " and external disturbance, the common constant current source height of ratio of precision.In addition, in actual detected, can't detect the electric current of second earth point usually, inject electric current and continuous earth point electric current as long as detect each representative point, detect its shunting situation and can judge the ground connection situation.Injection does not all have obviously shunting as each point, can think that network has only one point earth; Arbitrary decanting point has recorded obvious shunting, then can think to have second earth point near this point.
For second kind of test: tested object is the transformer station of an operation 110kV, according to above-mentioned essentially identical mode carry out under the nominal situation, test under three kinds of situations under nonmetal earth point and the metal earth point.By test as can be known: under the nominal situation, no matter which position to inject little electric current in, continuous earth point place all has the same electrical flow valuve; Artificial when increasing variable resistor as second ground connection, even when resistance is big, also can tell shunting by the application's method, and split ratio and the proportional relation of different resistance values, thereby easy-to-look-uply go out unnecessary earth point., also needing to consider to inject electric current to the influence of voltage secondary circuit during as tested object with the actual transformer station that puts into operation.For knowing that if whether inject electric current exerts an influence to secondary voltage circuit and how have under the situation of influence influence degree, transformer station does following test in operation: on the fault oscillograph screen, (110V over the ground) directly is shorted on the neutral line line direct supply, start manually record ripple, relatively the voltage before and after direct supply and the neutral line short circuit is recorded wave-wave shape, and by relatively finding: injecting direct current on the voltage secondary circuit neutral line network does not have influence substantially to secondary circuit.In addition, owing to inject electric current very little (generally selecting 10mA, 100mA etc.), the line resistance of neutral line network also very little (being generally less than 1 Ω) makes injecting voltage reality very little in addition, proved further that thus the DC current injection neutral line does not influence operational outfit, has very strong security.
Voltage secondary circuit neutral line network multipoint earthing detects and adopts the mode of injecting little electric current, must relate to injection device and pick-up unit.For this reason, the embodiment of the present application also provides a kind of detection system of voltage secondary circuit neutral line network multipoint earthing.This system comprises signal generator and detecting device two big core components, and the storer that stores voltage secondary circuit neutral line topology of networks, wherein signal generator injects first electric current at least one electric current decanting point of selecting at voltage secondary circuit neutral line network; Detecting device comprises current measurement device, comparer and counter, described current measurement device is for detection of the electric current of the continuous earth point annex of voltage secondary circuit neutral line network, to obtain second electric current, described comparer is used for difference and the pre-set threshold value of described second electric current and described first electric current are compared, if described difference is in pre-set threshold value, determine then at voltage secondary circuit neutral line network internal storage that at multipoint earthing described counter is used for calculating according to voltage secondary circuit neutral line topology of networks determines each earth point.The power supply that signal generator comprises can be direct supply or low-frequency ac power.Signal generator can also comprise the limit value element, and when the output current of direct supply or low-frequency ac power surpassed threshold limit value, signal generator was with first electric current of described threshold limit value as injection electric current decanting point.Below the hardware design of said system embodiment is carried out brief description:
For signal generator: referring to Fig. 4 (a), the internal hardware that the figure shows signal generator is formed, and it comprises CPU, ADC, DAC, power supply, and display screen, button, high-precision voltage reference etc. are partly formed.Signal generator is used for test by the constant current source that CPU control DAC and high precision reference source produce required numerical value, and the electric current that produces can be some direct current signals and pulse signals such as 10mA, 100mA, injects ground loop from far-end then.For detecting device: referring to Fig. 4 (b), this detecting device is by CPU, ADC, power supply, and display screen, button and high precision pincers type reometer form, and wherein high precision pincers type reometer is critical piece, is related to the accuracy of detection of total system.Amplified through filtering by the detected weak current of pincers type reometer, enter ADC and be converted to digital signal, handle real-time being presented on the LCD screen in back by CPU again.Detecting device should have following function: adopt the direct current split-core type meter, but on-line measurement does not resemble traditional current measure device, need seal in tested loop; The high precision direct current detection, resolution can reach 0.1mA; Detecting device is furnished with big LCD display can show testing result in real time; Detecting device has bigger internal memory, can store many group testing results, is uploaded to computer and is further processed after detection is finished; Have writing function, can monitor certain section loop for a long time, thereby find the situation of instantaneous multipoint earthing; A-table-multi-purpose, but the detection system ground connection that matches with the signal generator of other portable earthing test instrument.
Detecting device for the ease of operation and identification, also needs to arrange corresponding panel except above-mentioned two big core component signal generators and detecting device, the multipoint earthing of finishing the voltage secondary circuit by this panel detects.Need to prove: although foregoing has been narrated the overall framework of voltage secondary circuit multipoint earthing checkout equipment, but in the product facility production run of reality, should also be noted that the design of technical parameter, different technical parameters will influence accuracy and the precision of detector.Provide the Reasonable Parameters scope of multipoint earthing checkout equipment herein, supply the practical application reference: voltage output :≤1VDC; Electric current output :≤100mA; Voltage output accuracy: ± 10 μ V; Electric current output accuracy: ± 0.1mA; Output mode: pattern 1 constant current 10mA, pattern 2 constant current 100mA, mode 3 standard constant current 10mA, pattern 4 standard constant current 100mA; Direct current split-core type meter current range: ± 0.1mA～± 5A; Record: 32M; Calibration accuracy: ± 0.1mA.
Easy for what narrate, what the various distortion implementations of above-described embodiment of this instructions and embodiment stressed all is and the difference of other embodiment or mode of texturing that identical similar part is mutually referring to getting final product between each situation.Especially, for several improved procedures of system embodiment, because it is substantially similar in appearance to method embodiment, so describe fairly simplely, relevant part gets final product referring to the part explanation of method embodiment.In actual application, can select wherein some or all of unit to realize the purpose of present embodiment scheme according to the actual needs, those of ordinary skills namely can understand and implement under the situation of not paying creative work.
The above only is the application's embodiment; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the application's principle; can also make some improvements and modifications, these improvements and modifications also should be considered as the application's protection domain.
Claims (8)
1. the detection method of a voltage secondary circuit neutral line network multipoint earthing is characterized in that described method comprises:
Select at least one electric current decanting point at voltage secondary circuit neutral line network, inject first electric current from this at least one electric current decanting point; Detect near the electric current of continuous earth point of voltage secondary circuit neutral line network, obtain second electric current; Difference and the pre-set threshold value of described second electric current and described first electric current are compared, if described difference in pre-set threshold value, is then determined at voltage secondary circuit neutral line network internal storage at multipoint earthing; Locate each earth point according to voltage secondary circuit neutral line topology of networks.
2. method according to claim 1 is characterized in that, describedly selects at least one electric current decanting point to be specially at voltage secondary circuit neutral line network:
Determine the neutral line of voltage secondary circuit neutral line network;
At least one decanting point of selecting at the described neutral line is as the electric current decanting point.
3. method according to claim 1 is characterized in that, injects first electric current from least one electric current decanting point and injects by direct supply or low-frequency ac power, and described low-frequency ac power is frequency less than 1 hertz AC power.
4. method according to claim 3, it is characterized in that, described direct supply is the dc pulse current source, near the continuous earth point of described detection voltage secondary circuit neutral framework electric current detects by the difference measurement method, and described difference measurement method is for measuring the poor of pulse high level and reference level.
5. method according to claim 4, it is characterized in that, set the threshold limit value of the output current of direct supply or low-frequency ac power, when direct supply or low-frequency ac power output current surpass threshold limit value, with described threshold limit value as first electric current that injects the electric current decanting point.
6. the detection system of a voltage secondary circuit neutral line network multipoint earthing is characterized in that this system comprises: signal generator and detecting device, and the storer that stores voltage secondary circuit neutral line topology of networks, wherein:
Described signal generator, at least one the electric current decanting point that is used for selecting at voltage secondary circuit neutral line network injects first electric current;
Described detecting device comprises current measurement device, comparer and counter, described current measurement device is for detection of the electric current of the continuous earth point annex of voltage secondary circuit neutral line network, to obtain second electric current, described comparer is used for difference and the pre-set threshold value of described second electric current and described first electric current are compared, if described difference is in pre-set threshold value, determine then at voltage secondary circuit neutral line network internal storage that at multipoint earthing described counter is used for calculating according to voltage secondary circuit neutral line topology of networks determines each earth point.
7. system according to claim 6 is characterized in that, described signal generator comprises power supply, and described power supply is direct supply or frequency less than 1 hertz low-frequency ac power.
8. system according to claim 7, it is characterized in that, described signal generator also comprises the limit value element, and when the output current of direct supply or low-frequency ac power surpassed threshold limit value, signal generator was with first electric current of described threshold limit value as injection electric current decanting point.
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Cited By (5)
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| CN103592564A (en) * | 2013-11-26 | 2014-02-19 | 国家电网公司 | Grounding judgment device of voltage transformer grounded neutral wire for protecting transformer substation |
| CN103605041A (en) * | 2013-11-14 | 2014-02-26 | 国家电网公司 | Non-contact multi-point grounding detection method and system for secondary circuit of current transformer |
| CN104198877A (en) * | 2014-09-26 | 2014-12-10 | 国家电网公司 | Portable multipoint grounding detector |
| CN105182157A (en) * | 2015-09-07 | 2015-12-23 | 江苏省电力公司泰州供电公司 | Neutral point multi-point grounding detection device based on high-accuracy detection current |
| CN105589004A (en) * | 2014-10-13 | 2016-05-18 | 国家电网公司 | Method and device for judging substation relay protection-used PT secondary common circuit single-point grounding |
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| CN103605041B (en) * | 2013-11-14 | 2017-01-18 | 国家电网公司 | Non-contact multi-point grounding detection method and system for secondary circuit of current transformer |
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| CN104198877A (en) * | 2014-09-26 | 2014-12-10 | 国家电网公司 | Portable multipoint grounding detector |
| CN105589004A (en) * | 2014-10-13 | 2016-05-18 | 国家电网公司 | Method and device for judging substation relay protection-used PT secondary common circuit single-point grounding |
| CN105182157A (en) * | 2015-09-07 | 2015-12-23 | 江苏省电力公司泰州供电公司 | Neutral point multi-point grounding detection device based on high-accuracy detection current |
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