CN105759121B - A kind of insulated monitoring method of ungrounded supply system - Google Patents
A kind of insulated monitoring method of ungrounded supply system Download PDFInfo
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- CN105759121B CN105759121B CN201410805594.3A CN201410805594A CN105759121B CN 105759121 B CN105759121 B CN 105759121B CN 201410805594 A CN201410805594 A CN 201410805594A CN 105759121 B CN105759121 B CN 105759121B
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Abstract
The present invention relates to a kind of insulated monitoring methods of ungrounded supply system, and this approach includes the following steps：1) low-frequency ac signal that setting original frequency is injected to ungrounded supply system, using the signal acquisition and measures the capacitance of power supply system over the ground；2) according to the capacitance size being calculated, it is adaptively adjusted signal frequency, and AC signal is injected to ungrounded supply system with the frequency after adjustment；3) new signal is utilized, the capacitance and resistance value of power supply system over the ground is measured, the frequency of measuring signal is further adjusted according to the capacitance of calculating, until the resistance value measured meets the required precision limited.Compared with prior art, the present invention has many advantages, such as to reduce influence of the power supply system direct-to-ground capacitance to resistance measurement, significantly improves the precision of insulation measurement and the reliability of insulating monitoring.
Description
Technical field
The present invention relates to a kind of insulating monitoring technologies of power supply system, more particularly, to a kind of ungrounded supply system
Insulated monitoring method.
Background technology
The power supply system of isolated neutral, generally use insulation monitoring device monitor the insulation status of system over the ground.
With system branch increase or the lengthening of line cord, the capacitance of system over the ground also increase therewith.In some power supply systems
In, the continuous switching of big capacity load also results in the continuous variation of system direct-to-ground capacitance.The presence of system direct-to-ground capacitance, it is right
The precision of insulation measurement causes prodigious influence.Traditional insulating monitoring technology is divided by injecting low-frequency ac signal
The resistance and capacitance of other measuring system over the ground.Common technology has single-frequency method and dual-frequency method etc..Both technologies are in system capacitance
When being relatively fixed, the precision of insulation measurement is stablized relatively, but when system direct-to-ground capacitance becomes larger or constantly changes, insulated electro
The precision that resistance measures will be greatly affected, and cause to measure distortion, or even the case where insulation fault wrong report occur.
Invention content
It is an object of the present invention to overcome the above-mentioned drawbacks of the prior art and provide a kind of earth-free power supplies to be
The insulated monitoring method of system reduces influence of the power supply system direct-to-ground capacitance to resistance measurement, significantly improves insulation resistance
The precision of measurement and the reliability of insulating monitoring.
The purpose of the present invention can be achieved through the following technical solutions：
A kind of insulated monitoring method of ungrounded supply system, which is characterized in that include the following steps：
1) low-frequency ac signal that setting original frequency is injected to ungrounded supply system, using the signal acquisition and measures
The capacitance of power supply system over the ground；
2) according to the capacitance size being calculated, it is adaptively adjusted signal frequency, and with the frequency after adjustment to not
It is grounded power supply system and injects AC signal；
3) new signal is utilized, power supply system capacitance and resistance value over the ground is measured, according to the capacitance of calculating into one
The frequency of successive step measuring signal, until the resistance value measured meets the required precision of design.
The signal frequency that is adaptively adjusted refers to：According to the capacitance of different range, using the letter of different frequency
Number.
The frequency for the measuring signal that the range and different range of the capacitance are suitble to is according to test data come really
Fixed, determining foundation is：In the capacitance range, using the measuring signal of the frequency, the measurement accuracy of insulation resistance can be made
Meet the requirement limited.
It can be matched by certain relationship between the capacitance range and measuring signal frequency, specially：
Wherein C is capacitance over the ground, f0For original frequency, f is the frequency test signal after adjustment.
Such as f0The μ of=2.5Hz, C≤150 F.
Compared with prior art, the present invention has the following advantages：
It is improved on the basis of existing ripe low-frequency ac signal measuring technique using fixed frequency, according to not
The variation of the size and capacitance that are grounded power supply system direct-to-ground capacitance can reduce power supply to adjust the frequency of low-frequency ac signal
Influence of the system direct-to-ground capacitance to resistance measurement, significantly improves the precision of insulation measurement and the reliability of insulating monitoring.
Description of the drawings
Fig. 1 is the fundamental diagram of the present invention；
Fig. 2 is the equivalent schematic diagram of the present invention.
Specific implementation mode
The present invention is described in detail with specific embodiment below in conjunction with the accompanying drawings.
Embodiment
It is as shown in Figure 1 the fundamental diagram of isolated neutral system insulation against ground monitoring, in isolated neutral three-phase system
In, with the presence of capacitance and resistance between three-phase cable and the earth, C is used respectively in figurea、Cb、CcAnd Ra、Rb、RcTo indicate.In it
Portion includes DC internal resistance Ri, it is used for the sample resistance R of signal acquisitions, and the test circuit G for generating test signal.It is not examining
In the case of considering the internal resistance of source, analyzes for convenience, schematic diagram shown in FIG. 1 is simplified, schematic diagram such as Fig. 2 after simplifying
It is shown.In fig. 2, the capacitor equivalent of three-phase cable in parallel over the ground is Cf, then have Cf=Ca//Cb//Cc, three-phase cable in parallel
Equivalent resistance is R over the groundf, there is Rf=Ra//Rb//Rc, the then total impedance z of the three-phase ungrounded power systems over the groundf=Rf//Cf=
Rf+j/(2πfCf).In insulating monitor IMD, the output voltage U of test signalgIt can be measured by Acquisition Circuit, in figure
IgIt can be calculated by acquiring the voltage on sampling resistor, i.e.,：Ig=Ug/Rs, therefore it is added in CfAnd RfOn voltage Uf=
Ug-Ig×Ri.Then the total impedance of three-phase ungrounded power systems over the ground can be calculated, i.e.,Assuming that by calculating to obtain Zf=a+bj, the Z obtained with frontf's
Formula contrast can be obtained：Rf=a, 1/ (2 π fCf)=b can then calculate the equivalent total electricity of the isolated neutral system over the ground
Resistance and total capacitance value.It can be seen that due to the earth-free presence to system capacitance, it includes capacity current to lead to electric current actually
Component and resistive current component, in fig. 2 both components respectively flow through equivalent capacity CfWith equivalent resistance Rf, just because of Cf
Shunting, be used in insulation resistance RfThe effective current in resistance property calculated becomes smaller so that passes through point of the Current calculation insulation resistance
Resolution reduces, thus insulation resistance R has been calculatedfError increase.Only capacitive current component is made to become smaller, i.e. capacitive reactances
Become larger, current in resistance property could be increased.From zf=Rf//Cf=Rf+j/(2πfCf) on analyze, to increase capacitive reactances, only be reduced
The frequency f of test signal.
Operation principle：
Using the device, insulating monitor IMD first injects the low-frequency ac that a certain original frequency is f to isolated neutral system
Signal utilizes signal acquisition sampling resistor RsVoltage Ug, electric current I is calculatedg, while synchronous acquisition signal generating circuit
The signal voltage U of generationg, utilize Ig、UgCalculate the total impedance Z of the not welding systemf=a+bj, a, b are datums here.
Utilize (the 2 π fC of correspondence formula 1/f)=b calculates the capacitance C of system over the groundf, according to the size of the capacitance, adaptively
Adjustment signal frequency, so that the frequency after adjustment is matched with the capacitance range where the capacitance.Then again with adjustment after
Frequency injects AC signal to isolated neutral system；Using the test signal of new frequency, the simultaneously capacitance of computing system over the ground is measured
CfWith resistance Rf, and according to the capacitance C of calculatingfThe frequency for further adjusting test signal, until capacitance and the signal frequency measured
Rate meets matching and requires.Different capacitance ranges uses the measuring signal of different frequency, this capacitance range and measuring signal frequency
The correspondence of rate is determined according to test data.Determining foundation is：In the capacitance range, the survey of the frequency is used
Trial signal can make the precision of insulation measurement reach the requirement of restriction.
Scheme the above is only the implementation of the present invention, it should be noted that those skilled in the art are come
It says, various improvements and modifications may be made without departing from the principle of the present invention, these improvements and modifications also should be regarded as
Protection scope of the present invention.
Claims (3)
1. a kind of insulated monitoring method of ungrounded supply system, which is characterized in that include the following steps：
1) low-frequency ac signal that setting original frequency is injected to ungrounded supply system, using the signal acquisition and measures power supply
The capacitance of system over the ground；
2) according to the capacitance size being calculated, it is adaptively adjusted signal frequency, makes the frequency after adjustment and the capacitance
The capacitance range at place matches, and injects AC signal to ungrounded supply system with the frequency after adjustment；
3) new signal is utilized, the capacitance and resistance value of power supply system over the ground is measured, is further adjusted according to the capacitance of calculating
The frequency of whole measuring signal, until the resistance value measured meets the required precision of design；
The signal frequency that is adaptively adjusted refers to：According to the capacitance of different range, using the signal of different frequency.
2. the insulated monitoring method of ungrounded supply system according to claim 1, which is characterized in that the capacitance
The frequency for the measuring signal that the range and different range of value are suitble to determines that determining foundation is according to test data：
In the capacitance range, using the measuring signal of the frequency, the measurement accuracy of insulation resistance can be made to meet the requirement limited.
3. the insulated monitoring method of ungrounded supply system according to claim 2, which is characterized in that the capacitance
It can be matched by certain relationship between range and measuring signal frequency, specially：
Wherein C is capacitance over the ground, f0For original frequency, f is the frequency test signal after adjustment.
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| CN201410805594.3A CN105759121B (en) | 2014-12-18 | 2014-12-18 | A kind of insulated monitoring method of ungrounded supply system |
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| CN201410805594.3A CN105759121B (en) | 2014-12-18 | 2014-12-18 | A kind of insulated monitoring method of ungrounded supply system |
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| CN105759121B true CN105759121B (en) | 2018-11-02 |
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Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106443195A (en) * | 2016-11-03 | 2017-02-22 | 深圳市沃特玛电池有限公司 | Insulation resistance measuring method and insulation resistance measuring equipment |
| CN106556744B (en) * | 2016-11-28 | 2019-10-11 | 东北电力大学 | A kind of direct current system insulation detecting method based on resonance compensation theory |
| DE102017217473B3 (en) * | 2017-09-29 | 2019-01-17 | Bender Gmbh & Co. Kg | Method and monitoring device for selectively determining a partial system leakage capacity in an ungrounded power supply system |
| CN107894543A (en) * | 2017-11-14 | 2018-04-10 | 云南电网有限责任公司电力科学研究院 | A kind of power distribution network parameter measuring apparatus, method and system over the ground |
| CN110687353B (en) * | 2019-11-15 | 2022-04-15 | 华霆（合肥）动力技术有限公司 | Insulation resistance detection method, device, system and storage medium |
| CN113702873A (en) * | 2021-08-15 | 2021-11-26 | 南京理工大学 | Insulation monitoring method for wireless charging power supply cable of electric automobile |
| CN113671315B (en) * | 2021-08-18 | 2023-10-27 | 北京四方继保工程技术有限公司 | ITn power supply insulation fault positioning method based on proportional differential principle |
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| CN101769966B (en) * | 2010-01-27 | 2012-07-04 | 广东电网公司电力科学研究院 | Method and device for measuring ground capacitance of DC system |
| CN103135031B (en) * | 2012-12-31 | 2015-03-04 | 中国矿业大学 | Coal mine high-voltage grid system insulation state monitoring method |
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