CN100498358C - Insulation monitoring method for low current neutral grounding systems and apparatus for realizing the method - Google Patents
Insulation monitoring method for low current neutral grounding systems and apparatus for realizing the method Download PDFInfo
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- CN100498358C CN100498358C CNB2005100048868A CN200510004886A CN100498358C CN 100498358 C CN100498358 C CN 100498358C CN B2005100048868 A CNB2005100048868 A CN B2005100048868A CN 200510004886 A CN200510004886 A CN 200510004886A CN 100498358 C CN100498358 C CN 100498358C
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Abstract
The invention relates to a method and system of insulating monitoring the low current neutral grounding system, including the non-inductance cluster 1 which accesses system in star patching and the neutral point grounding directly. The method comprises the following steps: (a) measuring the current or voltage parameter of the cluster1 by the measuring device2, providing the current or voltage information of the system relative to the ground; (b) transferring the current to the voltage through the current-to-voltage converter;(c) displaying the three-phase voltage of the system by the voltage display4 and monitoring the insulation of the system;(d) applying the neutral conductor of alarming device5 connected to the cluster1 to measure the residual current of cluster1; (e) displaying the insulation condition by the alarm 6 and monitoring the low current neutral grounding system. Said invention can avoid the basic frequency, double frequency and frequency division resonance of the voltage transformer.
Description
One, technical field
The present invention relates to a kind of insulation monitoring method of small current neutral grounding system and realize the device of this method, belong to the power technology field, particularly relate to the insulation monitoring technology and the superpotential technology for eliminating of ferromagnetic resonance for electromagnetic voltage transformer of small current neutral grounding system.
Two, background technology
In small current neutral grounding system, usually all provide system's phase-to-ground voltage, residual voltage, line voltage, phase voltage information for the electromagnetic potential transformer of star-star connection and neutral-point solid ground to insulation monitor, metering, protective device by a winding that on generating plant, substation bus bar, connects.By accompanying drawing 1 as seen, this moment system over the ground parameter except sending out a converting equipment and a line wire ground capacitance C
0Outside, also have the magnetizing inductance L of electromagnetic potential transformer (PT1).Because of a winding neutral-point solid ground of electromagnetic potential transformer, its magnetizing inductance L just and lead ground capacitance C
0Formed L-C resonant circuit, when system occurs single-phase earthing or generator, transformer to disturbances such as aircraft carrier line chargings, just may excite resonance overvoltage and cause the electromagnetic potential transformer fuse melting, explode or cause electromagnetic potential transformer self to burn fault, also expand as " baked wheaten cake is operated " accident of bus and associated devices thereof when serious.
For eliminating the resonance fault of electromagnetic potential transformer, vast work about electric power person is generally paid close attention to, and many removing measures have been proposed, but in existing these harmonic elimination measures, it all is some parameter proposition in the L-C resonant circuit in the change system, because the complicacy and the polytrope of systematic parameter, most harmonic elimination measures all exist this moment these feelings that positive effect is arranged, and lose the situation of effect in that feelings at that time.
Three, summary of the invention
The objective of the invention is deficiency at the prior art existence, and, a kind of insulation monitoring method of small current neutral grounding system is provided and realizes the device of this method according to usually occurring the problem that electromagnetic potential transformer is easy to take place resonance when the disturbances such as system's generation single-phase earthing in the small current neutral grounding system.
The technical solution used in the present invention is:
A kind of insulation monitoring method of small current neutral grounding system is taked the earth-free mode of connection with the neutral point of a pitch of the laps of electromagnetic potential transformer in electric system, electromagnetic potential transformer only is used for the metering and the protection of system; Adopt one group of non-inductive element group to insert system by star-star connection and neutral-point solid ground, measure the curtage parameter of non-inductive element group by measuring element, system's curtage information relatively is provided, when adopting the measurement current system, by current/voltage converter current value is converted to magnitude of voltage, by the display displaying system three-phase voltage, the state of insulation of surveillance; Employing grounding alarm device is connected to the neutral line of non-inductive element group, measures the zero-sequence current of non-inductive element group, by alarm display system state of insulation, thus the insulation monitoring of realization small current neutral grounding system.
Described non-inductive element group, every phase can be made of single capacitor or resistor.
Described non-inductive element group, every phase can be made of two above resistors or capacitors in series.
Described non-inductive element group, every phase can be made of one or several capacitors and resistor in series.
Described non-inductive element group when containing more than two non-inductive element mutually, can provide system's phase-to-ground voltage when every by measuring the spread voltage parameter on one of them element.
Described measuring element adopts current transformer to realize the measurement of phase current.
Described alarm appliance adopts current transformer to realize the measurement of zero-sequence current.
A kind of device of small current neutral grounding system insulation monitoring method as mentioned above of realizing, mainly by cabinet, the non-inductive element group, measuring element, current/voltage converter, voltage display and the alarm appliance that are installed in the cabinet are formed; Non-inductive element group adopts star-star connection to be connected to electrical network, its neutral ground, after measuring element is measured the phase current of non-inductive element group, by current/voltage converter current value is converted to magnitude of voltage, by voltage display display system three-phase voltage, alarm appliance is connected to the neutral line of non-inductive element group, measures the zero-sequence current of non-inductive element group, by alarm display system state of insulation.
The top of described cabinet is provided with little bus-bar room, and the cabinet door is provided with indicating instrument, form, propelling crank jack, door lock and fastens, door lock hole, and the rear portion of cabinet is provided with main bus-bar.
Owing to adopted technique scheme; when generating plant, electric substation use the present invention; and according to protection, when the metering needs adopt incomplete triangle (V-V wiring) or a winding to no longer include (Y.Yn wiring) voltage transformer (VT) of earth point, at this moment just no longer there is the L-C resonant circuit in system.Elimination because of the L-C resonant circuit, system causes the Permanent fault described in the background technology of front with regard to voltage transformer (VT) can not take place again because of fundamental frequency, frequency multiplication, frequency division or ferro-resonance over-voltage, excess current, to operation and maintenance cost and workload be reduced greatly undoubtedly, will more effectively ensure the safe operation of mains supply.
Four, description of drawings
Fig. 1 is the L-C resonant circuit synoptic diagram that system exists in the background technology.
Fig. 2 is the synoptic diagram of the embodiment of the invention 1.
Fig. 3 is the synoptic diagram of the embodiment of the invention 2.
Fig. 4 is the synoptic diagram of the embodiment of the invention 3.
Fig. 5 realizes cabinet synoptic diagram of the present invention
Five, embodiment
Below in conjunction with drawings and Examples the present invention is described in further detail:
With reference to accompanying drawing, a kind of insulation monitoring method of small current neutral grounding system, adopt one group of non-inductive element group 1 by star-star connection connecting system and neutral-point solid ground, measure the curtage parameter of non-inductive element group 1 by measuring element 2, system's curtage information relatively is provided, when adopt measuring current system, current value is converted to magnitude of voltage by current/voltage converter 3, by voltage display 4 display system three-phase voltages, the state of insulation of surveillance; Employing grounding alarm device 5 is connected to the neutral line of non-inductive element group 1, measures the zero-sequence current of non-inductive element group 1, by alarm 6 display system state of insulations, thus the insulation monitoring of realization small current neutral grounding system.
Embodiment 1: with reference to accompanying drawing 2, described non-inductive element group 1 is every to be made of single capacitor C or resistor R.Form with the method for measuring electric current by single capacitor C among Fig. 2, unite the system voltage measuring system of formation with winding voltage transformer pt 2 that is star-star connection.Because of voltage transformer pt 2 measuring principles and method, be the known technology of electrotechnical measurement aspect, do not explain herein, below only be illustrated with regard to non-inductive element group 1 applicable cases.
The known capacitor electric capacity is C, its capacitive reactance Xc=1/ ω C; System just often, three phase-to-ground voltages are system line voltage U x's
Doubly, flowing through the electric current of capacitor this moment is
Zero-sequence current I
0=0; When system's generation single-phase earthing, know that according to the principles of electric and electronic engineering ground connection phase (for example A phase) voltage-to-ground will be reduced to 0, intact phase (B, C phase) voltage-to-ground will raise
Doubly, its value is system line voltage U x; To raise into phase voltage just often 3 times of its residual voltage, each phase current and zero-sequence current when relation can obtain A phase ground connection thus are: I '
CA=0, I '
CB=I '
CC=U x ω C, I '
0=3I
A
Change as seen from above electric current, its rule rule with the electromagnetic potential transformer measuring system phase-to-ground voltage of using star-star connection and neutral-point solid ground and residual voltage fully is the same, illustrates that the present invention can be used to provide system's voltage-to-ground and residual voltage information to insulation monitor.In order to adapt to generating plant, the person on duty's of transformer station supervision custom, the electric current that records above is through current/voltage converter 3 conversion, make insulation monitor show phase-to-ground voltage value and residual voltage value, the function of this moment just will be just the same and be convenient to the person on duty and monitor with the form of expression of existing insulation monitor.
Embodiment 2: with reference to accompanying drawing 3, described non-inductive element group 1 every the series connection by two above resistor R or capacitor C constitutes.Be by two resistor R series connection among Fig. 3, form with measuring the sectional pressure element voltage method, unite the formation voltage measurement system with the voltage transformer pt 2 that winding is an incomplete triangle (V-V wiring), as seen from Figure 3, the resistance value of every phase (or capacitive reactance) is each element resistance addition, i.e. R
A=R
B=R
C=R
1+ R
2, system just often, every phase current is
I
0=0A, and U is arranged
R1=I
AR
1, U
R2=I
AR
2Relation.When system's generation one point earth, ground connection phase U
AD=0, U
BD=U
CD=U
X, this moment I '
A=U
AD/ R
A=0,
Be elevated under the normal condition
Times, and I '
0Rising is 3 times of normal value, resistor R
2On voltage, constant because of resistance, electric current raises
Doubly, so record resistor R
2Magnitude of voltage also can provide system's voltage-to-ground information to insulation monitor equally, its intrinsic standoff ratio is K=(R
1+ R
2)/R
2
Embodiment 3: with reference to accompanying drawing 4, described non-inductive element group 1 is every to be made of one or several capacitor C and resistor R series connection.Be to be connected in series among Fig. 4, form with the method for measuring phase current by a capacitor C and a resistor R, and with winding voltage transformer pt 2 associating construction system voltage measurement systems that are delta connection.Removing every phase of impedance in this example is Z
A=Z
B=Z
C=(R
2+ X
C 2)
1/2With X among the embodiment 1 (referring to accompanying drawing 2)
COutside=1/ ω C difference, all the other and embodiment 1 are identical.The also available dividing potential drop mode of this example obtains the method for phase-to-ground voltage, and only Ci Shi intrinsic standoff ratio should be K=(R
2+ X
C 2)
1/2/ R, all the other are identical with embodiment 2.
As seen, when containing more than two non-inductive element mutually, can provide system's phase-to-ground voltage when every when non-inductive element group 1 by measuring the spread voltage parameter on one of them element.
A kind of device of small current neutral grounding system insulation monitoring method as mentioned above of realizing, mainly by cabinet 7, the non-inductive element group 1, measuring element 2, current/voltage converter 3, voltage display 4 and the alarm appliance 5 that are installed in the cabinet 7 are formed; Non-inductive element group 1 adopts star-star connection to be connected to electrical network, its neutral ground, after measuring element 2 is measured the phase current of non-inductive element group 1, by current/voltage converter 3 current value is converted to magnitude of voltage, by voltage display 4 display system three-phase voltages, alarm appliance 5 is connected to the neutral line of non-inductive element group 1, measures the zero-sequence current of non-inductive element group 1, by alarm 6 display system state of insulations.
The top of described cabinet 7 is provided with little bus-bar room 8, and the cabinet door is provided with indicating instrument 9, form 10, advance that crank jack 11, door lock are fastened 12, door lock hole 13, and the rear portion of cabinet 7 is provided with main bus-bar 14.
Owing to adopted technique scheme; when generating plant, electric substation use the present invention; and according to protection, when the metering needs adopt incomplete triangle (V-V wiring) or a winding to no longer include (Y.Yn wiring) voltage transformer (VT) of earth point, at this moment just no longer there is the L-C resonant circuit in system.Elimination because of the L-C resonant circuit, system causes the Permanent fault described in the background technology of front with regard to voltage transformer (VT) can not take place again because of fundamental frequency, frequency multiplication, frequency division or ferro-resonance over-voltage, excess current, to operation and maintenance cost and workload be reduced greatly undoubtedly, will more effectively ensure the safe operation of mains supply.
Claims (9)
1, a kind of insulation monitoring method of small current neutral grounding system is characterized in that: in system the neutral point of a pitch of the laps of electromagnetic potential transformer is taked the earth-free mode of connection, electromagnetic potential transformer only is used for the metering and the protection of system; Adopt one group of non-inductive element group (1) connecting system by star-star connection and neutral-point solid ground, measure the curtage parameter of non-inductive element group (1) by measuring element (2), system's curtage information relatively is provided, when adopting the measurement current system, by current/voltage converter (3) current value is converted to magnitude of voltage, by display (4) display system three-phase voltage, the state of insulation of surveillance; Employing grounding alarm device (5) is connected to the neutral line of non-inductive element group (1), measures the zero-sequence current of non-inductive element group (1), by alarm (6) display system state of insulation, thus the insulation monitoring of realization small current neutral grounding system.
2, the insulation monitoring method of small current neutral grounding system according to claim 1 is characterized in that: described non-inductive element group (1) is every to be made of single capacitor (C) or resistor (R).
3, the insulation monitoring method of small current neutral grounding system according to claim 1 is characterized in that: described non-inductive element group (1) is every to be made of two above resistors (R) or capacitor (C) series connection.
4, the insulation monitoring method of small current neutral grounding system according to claim 1 is characterized in that: described non-inductive element group (1) is every by one or several capacitors (C) and resistor (R) series connection formation.
5, the insulation monitoring method of small current neutral grounding system according to claim 1, it is characterized in that: described non-inductive element group (1) is when every when containing more than two non-inductive element mutually, can provide system's phase-to-ground voltage by measuring the spread voltage parameter on one of them element.
6, the insulation monitoring method of small current neutral grounding system according to claim 1 is characterized in that: described measuring element (2) adopts current transformer to realize the measurement of phase current.
7, the insulation monitoring method of small current neutral grounding system according to claim 1 is characterized in that: described alarm appliance (5) adopts current transformer to realize the measurement of zero-sequence current.
8, a kind of device of realizing the described small current neutral grounding system insulation monitoring of claim 1 method, it is characterized in that: mainly by cabinet (7), the non-inductive element group (1), measuring element (2), current/voltage converter (3), voltage display (4) and the alarm appliance (5) that are installed in the cabinet (7) are formed; Non-inductive element group (1) adopts star-star connection to be connected to electrical network, its neutral ground, after measuring element (2) is measured the phase current of non-inductive element group (1), by current/voltage converter (3) current value is converted to magnitude of voltage, by voltage display (4) display system three-phase voltage, alarm appliance (5) is connected to the neutral line of non-inductive element group (1), measures the zero-sequence current of non-inductive element group (1), by alarm (6) display system state of insulation.
9, device according to claim 8, it is characterized in that: the top of described cabinet (7) is provided with little bus-bar room (8), the cabinet door is provided with indicating instrument (9), form (10), advances crank jack (11), door lock to fasten (12), door lock hole (13), and the rear portion of cabinet (7) is provided with main bus-bar (14).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100048868A CN100498358C (en) | 2005-02-03 | 2005-02-03 | Insulation monitoring method for low current neutral grounding systems and apparatus for realizing the method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100048868A CN100498358C (en) | 2005-02-03 | 2005-02-03 | Insulation monitoring method for low current neutral grounding systems and apparatus for realizing the method |
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|---|---|
| CN1664597A CN1664597A (en) | 2005-09-07 |
| CN100498358C true CN100498358C (en) | 2009-06-10 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB2005100048868A Expired - Fee Related CN100498358C (en) | 2005-02-03 | 2005-02-03 | Insulation monitoring method for low current neutral grounding systems and apparatus for realizing the method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3879285A4 (en) * | 2018-11-13 | 2021-12-15 | Shenzhen VMAX New Energy Co.,Ltd. | Insulation detection circuit of vehicle-mounted bidirectional charger and detection method therefor |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102121958B (en) * | 2010-01-07 | 2013-08-14 | 深圳供电局有限公司 | Device and method for monitoring neutral point earthing of secondary winding of electric power current and voltage mutual inductor |
| CN102709045B (en) * | 2012-06-15 | 2015-09-16 | 四川泰克电器有限公司 | A kind of combination transformer |
| EP3336563A1 (en) * | 2013-06-26 | 2018-06-20 | Fuji Electric FA Components & Systems Co. Ltd. | Insulation monitoring device |
| CN104280664B (en) * | 2013-07-04 | 2017-08-11 | 刘宝稳 | A kind of online insulation monitoring of resonant earthed system and selection method |
| US10935609B2 (en) | 2017-09-12 | 2021-03-02 | Abb Schweiz Ag | Methods and systems for ground fault detection in a power distribution system |
-
2005
- 2005-02-03 CN CNB2005100048868A patent/CN100498358C/en not_active Expired - Fee Related
Non-Patent Citations (4)
| Title |
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| 小电流接地系统单相接地故障选线方法综述. 肖白，束洪春，高峰.继电器，第29卷第4期. 2001 |
| 小电流接地系统单相接地故障选线方法综述. 肖白，束洪春，高峰.继电器，第29卷第4期. 2001 * |
| 新型小电流接地系统选线消谐装置的研制. 王建赜，吴启涛，纪延超，柳焯.继电器，第29卷第5期. 2001 |
| 新型小电流接地系统选线消谐装置的研制. 王建赜，吴启涛，纪延超，柳焯.继电器，第29卷第5期. 2001 * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3879285A4 (en) * | 2018-11-13 | 2021-12-15 | Shenzhen VMAX New Energy Co.,Ltd. | Insulation detection circuit of vehicle-mounted bidirectional charger and detection method therefor |
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| CN1664597A (en) | 2005-09-07 |
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