CN107132458A - A kind of electric power system low frequency insulation detection device and method - Google Patents
A kind of electric power system low frequency insulation detection device and method Download PDFInfo
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
- G01R31/1227—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/12—Testing dielectric strength or breakdown voltage ; Testing or monitoring effectiveness or level of insulation, e.g. of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing
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Abstract
The invention discloses a kind of electric power system low frequency insulation detection device and method, device includes：First resistor and second resistance in parallel with tested electric power system again after being serially connected；It is serially connected rear one end to be connected between first resistor and second resistance, measurement resistance, low-pass filter unit and pulse signal source that the other end is connected to the ground；And it is connected in parallel on the detection computing unit at measurement resistance two ends.Pulse signal source is injected into tested electric power system after sending pulse signal, measured resistance, low-pass filter unit, and first resistor, second resistance.Computing unit is detected by detecting that the signal of change at measurement resistance two ends is tested the insulaion resistance of electric power system over the ground, and judges that tested electric power system whether there is insulation fault according to insulaion resistance.The present invention can effectively solve the problem that existing detection method time of measuring length, easily be interfered, and the technical problem of wrong report is easily produced in the case of bad environments.
Description
Technical Field
The invention relates to the field of electrical detection, in particular to a low-frequency insulation detection device and method applied to an electric power system, particularly a ship frequency converter system.
Background
In the marine industry, frequency converters are occupying an increasingly important position as a power supply system. As the working environment of the ship is generally severe, the influence of the weather deterioration on equipment is particularly obvious, and the insulation fault occurrence rate of a power supply system is high, the quick alarm of the insulation fault is related to the safety of the whole voyage of the ship.
At present, the power grid for the ship mostly adopts an IT (i.e. a neutral point is not grounded) power supply system to improve the safety of power supply. When the insulation resistance value of the marine power grid meets the standard requirement, even if a single-phase earth fault occurs, the short-circuit current is still small, and tripping is not needed in a short time, so that the reliability of power supply is ensured to a certain extent. However, with the development of the times, ships develop towards high automation, power networks are more and more dense, and meanwhile, the working environment of the ships is more and more severe. The electrical equipment on the ship is affected by salt fog, humidity and other factors, so that the system insulation is low, and accidents such as fire disasters and the like can be caused if the system is not processed in time, so that the life of crews is seriously threatened.
In the prior art, the following documents are mainly relevant to the technical solution of the present invention:
document 1 is published as 2013, 05 and 01, and chinese patent application publication No. CN103076497A discloses "an insulation detection method based on low pulse signal injection". The invention discloses an insulation detection method in the field of electric automobiles, which takes an intermittent direct current signal as a signal source and acquires corresponding data through a continuous charging and discharging process to calculate an insulation resistance value. The invention effectively solves the technical problems that the insulation performance of the whole vehicle is reduced, insulation fault points cannot be positioned, the structure is complex, and the positive electrode and the negative electrode cannot be accurately detected when electric leakage occurs simultaneously, which is caused by the conventional detection circuit. However, the disadvantages are: the calculation is complicated, the data to be sampled is more, the requirement on the sampling precision is higher, and errors are easy to generate.
Document 2 discloses chinese patent application No. CN104865506A, published 26.08/2015, "an insulation detection device for dc electrical systems. The invention discloses a detection method using square waves. The injection sampling circuit injects the square wave signal into the direct current electrical system and samples a response signal generated by the direct current electrical system under the excitation of the injected square wave signal. The calculation unit obtains sampling signals in the first half period and the second half period of the nth period in the nth period of the square wave signal, and calculates the value of the insulation resistance of the direct current electrical system according to the obtained sampling signals. The invention effectively solves the technical problem that the prior detection circuit has high requirements on the precision of the resistor and the ADC. However, the disadvantages are: the influence on the measurement result when the distributed capacitance is large is not considered, and the calculation procedures are more, so that the calculation result is inaccurate.
Therefore, the insulation detection device and method for the power supply system are provided to continuously monitor the insulation state of the power system on line, and when the insulation performance is lower than a certain degree, an alarm can be given in time to remind an operator, so that the defects that the currently used insulation detection method is long in measurement time, is easy to interfere and is easy to generate false alarm under the condition of severe environment are overcome, and the technical problem to be solved at present is solved urgently.
Disclosure of Invention
In view of the above, the present invention provides a power supply system low frequency insulation detection apparatus and method, which solve the technical problems of the existing detection method that the measurement time is long, the interference is easy to occur, and the false alarm is easy to occur under the severe environment.
In order to achieve the above object, the present invention specifically provides a technical implementation scheme of a low-frequency insulation detection device for a power supply system, where the low-frequency insulation detection device for the power supply system includes:
the first resistor and the second resistor are connected in series and then connected with the power supply system to be tested in parallel;
the measuring resistor, the low-pass filtering unit and the pulse signal source are connected in series, one end of the measuring resistor is connected between the first resistor and the second resistor, and the other end of the measuring resistor is connected with the ground;
the detection calculation unit is connected in parallel with two ends of the measuring resistor;
the pulse signal source sends out a pulse signal, the pulse signal passes through the measuring resistor, the low-pass filtering unit, the first resistor and the second resistor and then is injected into the power supply system to be tested, the detection and calculation unit calculates the insulation resistance of the power supply system to be tested to the ground by detecting signals at two ends of the measuring resistor, and judges whether the power supply system to be tested has insulation faults or not according to the insulation resistance.
Preferably, the pulse signal emitted by the pulse signal source is a periodic square wave pulse signal with alternating positive and negative.
Preferably, the measured power supply system is equivalent to a parallel circuit of an insulation resistor and a branch distributed capacitor.
Preferably, the frequency of the periodic square wave pulse signal emitted by the pulse signal source is(5 τ for each half cycle, 10 τ for the entire cycle), τ is the time constant,detecting the computing unit with T1The voltage across the measuring resistor is sampled at equal intervals for each half pulse signal period of the interval time, wherein V2Is relative to 2T1At the moment the voltage, V, across the measuring resistor1Is relative to T1At the moment the voltage, V, across the measuring resistor0The voltage across the measuring resistor is measured at a time relative to zero.
Preferably, the charging and discharging time of the branch distributed capacitor is 5 tau.
Preferably, the detection and calculation unit detects steady-state voltage signals of two ends of the measuring resistor in the first half period of the periodic square wave pulse signal, and obtains the resistance value R of the insulation resistor in the first half period through calculation+And detecting steady-state voltage signals of two ends of the measuring resistor in the latter half period of the periodic square wave pulse signal, and calculating to obtain the resistance value R of the insulation resistor in the latter half period-Finally, R is taken as the effective value of the insulation resistance,and the detection calculation unit judges whether the tested power supply system has insulation faults or not according to the effective value of the insulation resistance.
Preferably, the resistance value R of the insulation resistor in the first half period+Calculated according to the following formula:
resistance R of the insulation resistor in the second half period-Calculated according to the following formula:
wherein E ismIs the absolute value of the amplitude of the periodic square wave pulse signal,for measuring the voltage across a resistor, RiIs the parallel resistance value of the first resistor and the second resistor, RmTo measure the resistance of the resistor.
Preferably, the power supply system to be tested is a marine neutral point ungrounded (IT) power supply system.
The invention also provides a technical implementation scheme of the low-frequency insulation detection method of the power supply system, and the low-frequency insulation detection method of the power supply system comprises the following steps:
the pulse signal source sends out a pulse signal, and the pulse signal passes through the low-pass filtering unit and the measuring resistor and is injected into a power supply system to be measured through the first resistor and the second resistor;
and the detection calculation unit calculates the insulation resistance of the power supply system to be detected to the ground by detecting signals at two ends of the measuring resistor, and judges whether the power supply system to be detected has insulation faults or not according to the insulation resistance.
Preferably, the pulse signal emitted by the pulse signal source is a periodic square wave pulse signal with alternating positive and negative.
Preferably, under the action of a periodic square wave pulse signal emitted by the pulse signal source, the branch distributed capacitor of the power supply system to be tested is continuously charged and discharged, and the distributed capacitor is equivalent to the isolation in the power supply system to be tested after charging is completed. The detection and calculation unit calculates the resistance values of the insulation resistors in the first half period and the second half period of the periodic square wave pulse signal, the average value of the resistance values of the insulation resistors in the first half period and the second half period is used as the effective value of the insulation resistor, and then whether the tested power supply system has insulation faults or not is judged.
Preferably, the process of calculating the insulation resistance of the power supply system to be tested by the detection calculation unit includes:
the detection and calculation unit detects steady-state voltage signals of two ends of the measuring resistor in the first half period of the periodic square wave pulse signal, and the resistance value R of the insulation resistor in the first half period is obtained through calculation+，Wherein E ismIs the absolute value of the amplitude of the periodic square wave pulse signal,for measuring the voltage across a resistor, RiIs the parallel resistance value of the first resistor and the second resistor, RmTo measure the resistance of the resistor.
The detection and calculation unit detects steady-state voltage signals of two ends of the measuring resistor in a latter half period of the periodic square wave pulse signal, and the resistance value R of the insulation resistor in the latter half period is obtained through calculation-，
The detection calculation unit takes R as an effective value of the insulation resistance,and judging whether the tested power supply system has insulation fault according to the effective value of the insulation resistance.
Preferably, the pulse signal source can automatically adjust the frequency of the periodic square wave pulse signal, and the frequency of the periodic square wave pulse signal emitted by the pulse signal source is
The detection calculation unit is represented by T1The voltage across the measuring resistor, V, is sampled at equal intervals for each half pulse signal period of the interval time0For measuring the voltage across the resistor at a time relative to zero, V1Is relative to T1At the moment the voltage, V, across the measuring resistor2Is relative to 2T1The voltage across the measuring resistor is measured at the moment.
Preferably, the charging and discharging time of the branch distributed capacitor is 5 tau.
Preferably, the power supply system low-frequency insulation detection method is applied to detection of the ground fault of the ship frequency converter system.
By implementing the technical scheme of the low-frequency insulation detection device and the method for the power supply system, provided by the invention, the following beneficial effects are achieved:
(1) the circuit structure is simple, the principle is simple, and the ground fault of the power supply system can be effectively detected;
(2) the invention can adaptively change the frequency of the pulse signal source according to the voltage at the two ends of the measuring resistor, and has high measuring speed;
(3) the invention can effectively solve the problems of high-frequency interference and direct-current interference in the insulation detection process, and greatly improves the reliability;
(4) the invention has strong universality and can be suitable for all frequency converters without influencing the normal operation of the frequency converters.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other embodiments can be obtained from these drawings without inventive effort.
FIG. 1 is a schematic circuit diagram of one embodiment of a low frequency insulation detection apparatus for a power supply system of the present invention;
FIG. 2 is a schematic diagram of an equivalent circuit of an embodiment of the low frequency insulation detection apparatus of the power supply system of the present invention;
FIG. 3 is a schematic diagram showing the waveforms of the test power source in the low frequency insulation detection apparatus of the power supply system of the present invention;
FIG. 4 is a schematic voltage waveform of two ends of a detection resistor and a capacitor in the low frequency insulation detection device of the power supply system according to the present invention;
fig. 5 is a schematic diagram of a measuring point selecting method in the low-frequency insulation detecting method of the power supply system according to the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1 to 5, embodiments of a low frequency insulation detection device and method for a power supply system according to the present invention are shown, and the present invention will be further described with reference to the drawings and the embodiments.
As shown in a dashed line frame of fig. 1, a low-frequency insulation detection device of a power supply system is applied to an IT power supply system for a ship. The power supply system low-frequency insulation detection device 10 includes:
and the first resistor R1 and the second resistor R2 are connected in series and then connected with the power supply system to be tested in parallel.
The measuring resistor R3, the low-pass filter unit 1 and the pulse signal source G are connected in series, and then one end of the measuring resistor R3 is connected between the first resistor R1 and the second resistor R2, and the other end of the measuring resistor R3 is connected with the ground.
And a detection calculation unit 3 connected in parallel across the measurement resistor R3.
The pulse signal source G sends out a pulse signal, the pulse signal passes through the measuring resistor R3, the low-pass filtering unit 1, the first resistor R1 and the second resistor R2 and then is injected into the power supply system to be detected, the detection and calculation unit 3 calculates the insulation resistance of the power supply system to be detected to the ground through detecting signals at two ends of the measuring resistor R3, and judges whether the power supply system to be detected has insulation faults or not according to the insulation resistance. The low-pass filtering unit is used for filtering high-frequency interference signals of the detected power supply system, and the low-frequency insulation detection device 10 of the power supply system can not be interfered by high frequency due to the adoption of the low-pass filtering unit 1.
The pulse signal source G superposes a self-adaptive square wave signal between the power supply system to be measured and the ground, and measures the insulation impedance to the ground by comparing the waveforms of the sent signal and the returned signal. The pulse signal source G is a pulse signal emission source, the pulse signal emitted by the pulse signal source G is a periodic low-frequency square wave pulse signal with alternating positive and negative, and the low-frequency square wave pulse signal passes through the measuring resistor R3, the low-pass filtering unit 1, and the first resistor R1 and the second resistor R2 which are used as voltage dividing resistors and is injected into a power supply system to be tested. The impedance of the low-pass filtering unit 1 to the injected low-frequency square wave pulse signal is small, but the alternating-current impedance to the power frequency signal in the power grid is very large.
The tested power supply system is equivalent to a parallel circuit of an insulation resistor and a distributed capacitor. The equivalent simplified circuit of fig. 1 is shown in fig. 2 when an insulation fault occurs. It is composed ofIn, G is the signal source, RiEquivalent to a voltage dividing resistor, the resistance value of which is the parallel resistance value of the first resistor R1 and the second resistor R2 in FIG. 1, RmThe resistance is equivalent to the measuring resistance R3 in the attached figure 1, R is a fault grounding resistance which is the resistance when the whole line of the power supply system to be measured generates a grounding fault, and C is a branch distributed capacitance. Under the action of a pulse signal source G, the branch distributed capacitor C is continuously charged and discharged, after the charging is finished, the branch distributed capacitor C plays an isolation role (the branch distributed capacitor C is equivalent to isolation from a tested power supply system), the insulation resistance at the moment can be directly calculated (when the tested power supply system has an insulation fault, the insulation resistance is the fault grounding resistance), and the value of the insulation resistance is obtained by averaging the values of the first half period and the second half period of the periodic low-frequency square wave pulse signal.
As shown in fig. 3, the pulse signal source G emits a periodic low-frequency square wave pulse signal with alternating positive and negative, and the generated voltage f (t) has an expression in the first period:
wherein E ismIs the amplitude of the low-frequency square wave pulse signal, T is the period of the low-frequency square wave pulse signal, and T is time.
As shown in fig. 4, curve B is the voltage across the branch distribution capacitor C, curve a is the voltage across the measurement resistor R3, t1 is the time when the branch distribution capacitor C is in the discharging state, and t2 is the time when the branch distribution capacitor C is in the charging state. According to the attached drawings, in each period under the action of the periodic low-frequency square wave pulse signal, the branch distributed capacitor C is in a charge-discharge state.
The low-frequency insulation detection device 10 of the power supply system can adaptively change the frequency of the pulse signal source G according to the voltage at two ends of the measuring resistor R3, and greatly improve the measuring speed. The low-frequency square wave pulse signal on the measuring resistor R3 is equally spaced in each half periodTime (interval time T)1) Three points were taken to obtain the time constant τ, as shown in fig. 5. The point taking method is more convenient to calculate, the number of the points is less, and the precision of the calculation result is higher. Wherein,for detecting the resistance RmThe voltage across the terminals. When the detection time t is equal to 0, the voltage across the measuring resistor R3 is V0(ii) a Detecting time T ═ T1When the voltage across the measuring resistor R3 is V1(ii) a The detection time T is 2T1When the voltage across the measuring resistor R3 is V2；UsThe voltage value at which the capacitor C can eventually fill up is distributed to the branches.
Then there are:
in this case, the time constant τ is found to be:
in each half cycle of the low-frequency square wave pulse signal, the branch distributed capacitor C has the charging and discharging states. The charging and discharging time of the branch distribution capacitor C is 5 tau, and the value of 5 tau is a key point, and the branch distribution capacitor C is considered to be fully charged at the moment, and the branch where the branch distribution capacitor C is located is equivalently disconnected. By finding the time constant τ, selectingAs the frequency of the periodic low-frequency square wave pulse signal emitted by the pulse signal source G, thereby being effectiveThe time of measurement is reduced.
The detection and calculation unit 3 detects the steady-state voltage signal of the two ends of the measurement resistor R3 in the first half period of the periodic square wave pulse signal, and obtains the resistance value R of the insulation resistor in the first half period through calculation+And detecting a steady-state voltage signal of two ends of the measuring resistor R3 in the second half period of the periodic square wave pulse signal, and calculating to obtain the resistance value R of the insulation resistor in the second half period-Finally, R is taken as the effective value of the insulation resistance,the detection calculation unit 3 judges whether the tested power supply system has insulation fault according to the effective value R of the insulation resistance.
After the circuit is stabilized, in the first half period of the low-frequency square wave pulse signal, the measured insulation resistance value is as follows:
in the second half period of the low-frequency square wave pulse signal, the measured insulation resistance value is:
the effective value of the finally measured insulation resistance is as follows:
wherein E ismIs the absolute value of the amplitude of the periodic square wave pulse signal,for measuring the voltage across the resistor R3, RiIs the parallel connection of a first resistor R1 and a second resistor R2Resistance value, RmTo measure the resistance of the resistor R3.
In general, a resistance value is set in the detection and calculation unit 3, and when the measured insulation resistance effective value is lower than the set value, the detection and calculation unit 3 generates an alarm signal.
A specific embodiment of a power supply system low-frequency insulation detection method comprises the following steps:
the pulse signal source G sends out a pulse signal, the pulse signal passes through the low-pass filtering unit 1 and the measuring resistor R3, and then is injected into a power supply system to be measured through the first resistor R1 and the second resistor R2;
the detection calculation unit 3 calculates the insulation resistance of the power supply system to be detected to the ground by detecting signals at two ends of the measuring resistor R3, and judges whether the power supply system to be detected has insulation faults or not according to the insulation resistance.
The pulse signal sent by the pulse signal source G is a periodic square wave pulse signal with alternating positive and negative.
Under the action of periodic square wave pulse signals emitted by the pulse signal source G, the branch distributed capacitor C of the power supply system to be tested is continuously charged and discharged. The detection calculation unit 3 calculates the resistance values of the insulation resistors in the first half period and the second half period of the periodic square wave pulse signal, the average value of the resistance values of the insulation resistors in the first half period and the second half period is used as the effective value of the insulation resistor, and whether the insulation fault exists in the power supply system to be detected is judged according to the effective value of the insulation resistor.
The process of calculating the insulation resistance of the tested power supply system by the detection calculating unit 3 further comprises the following steps:
the detection and calculation unit 3 detects the steady-state voltage signal of the two ends of the measurement resistor R3 in the first half period of the periodic square wave pulse signal, and obtains the resistance value R of the insulation resistor in the first half period through calculation+，Wherein,Emis the absolute value of the amplitude of the periodic square wave pulse signal,for measuring the voltage across the resistor R3, RiIs the parallel resistance value of a first resistor R1 and a second resistor R2, RmTo measure the resistance of the resistor R3.
The detection and calculation unit 3 detects a steady-state voltage signal of two ends of the measurement resistor R3 in the second half period of the periodic square wave pulse signal, and obtains the resistance value R of the insulation resistor in the second half period through calculation-，
The detection calculation unit 3 takes R as an effective value of the insulation resistance,and judging whether the tested power supply system has insulation faults or not according to the effective value of the insulation resistance.
In order to further increase the measurement speed, the power supply system low-frequency insulation detection device 10 can adaptively change the signal generation frequency of the pulse signal source G according to the voltage across the measurement resistor R3. As a preferred embodiment of the present invention, the charging and discharging time of the branch distributed capacitor C is 5 τ, and the frequency of the periodic square wave pulse signal emitted by the pulse signal source G is at this time(5 τ for each half cycle, 10 τ for the entire cycle).
The time constant τ is calculated as follows: detecting the computing unit 3 by T1The voltage across the measurement resistor R3 is sampled equally for each half pulse signal period of the pitch time. Wherein, V0For measuring the voltage, V, across the resistor R3 at relatively zero times1Is relative to T1The voltage, V, across the resistor R3 is measured at all times2Is relative to 2T1Two time measuring resistors R3The voltage at the terminal, τ, is calculated according to the following equation:
by implementing the technical scheme of the power supply system low-frequency insulation detection device and method described in the specific embodiment of the invention, the following technical effects can be achieved:
(1) the power supply system low-frequency insulation detection device and method described in the specific embodiment of the invention have the advantages of simple circuit structure, simple principle and convenient application, and can effectively detect the ground fault of the power supply system;
(2) the power supply system low-frequency insulation detection device and the method described in the specific embodiment of the invention can change the frequency of the pulse signal source in a self-adaptive manner according to the voltage at two ends of the measuring resistor, and have the advantages of high measuring speed and high engineering application value;
(3) the power supply system low-frequency insulation detection device and method described in the specific embodiment of the invention can effectively solve the problems of high-frequency interference and direct-current interference in the insulation detection process, and have high measurement precision and greatly improved reliability;
(4) the power supply system low-frequency insulation detection device and method described in the specific embodiment of the invention have strong universality, and can be applied to all frequency converters without influencing the normal operation of the frequency converters.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make many possible variations and modifications to the disclosed embodiments, or equivalent modifications, without departing from the spirit and scope of the invention, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the protection scope of the technical solution of the present invention.
Claims (15)
1. A power supply system low frequency insulation detection device, comprising:
the first resistor (R1) and the second resistor (R2) are connected in series and then connected with the power supply system to be tested in parallel;
the measuring resistor (R3), the low-pass filtering unit (1) and the pulse signal source (G) are connected in series, and then one end of the measuring resistor (R3) is connected between the first resistor (R1) and the second resistor (R2), and the other end of the measuring resistor (R3) is connected with the ground;
and a detection calculation unit (3) connected in parallel across the measurement resistor (R3);
the pulse signal source (G) sends out a pulse signal, the pulse signal passes through the measuring resistor (R3), the low-pass filtering unit (1), the first resistor (R1) and the second resistor (R2) and then is injected into the power supply system to be tested, and the detection and calculation unit (3) calculates the insulation resistance of the power supply system to be tested to the ground by detecting signals at two ends of the measuring resistor (R3) and judges whether the power supply system to be tested has insulation faults or not according to the insulation resistance.
2. The power supply system low frequency insulation detection device of claim 1, wherein: the pulse signal sent by the pulse signal source (G) is a periodic square wave pulse signal with alternating positive and negative.
3. The power supply system low frequency insulation detection device of claim 2, characterized in that: the tested power supply system is equivalent to a parallel circuit of an insulation resistor and a branch distributed capacitor (C).
4. The power supply system low frequency insulation detection device according to claim 2 or 3, characterized in that: the frequency of the periodic square wave pulse signal emitted by the pulse signal source (G) isTau is a time constant and is a time constant,the detection calculation unit (3) uses T1Sampling the voltage across the measurement resistor (R3) at equal intervals for each half pulse signal period of interval time; wherein, V2Is relative to 2T1At the moment of time of the voltage, V, across the measuring resistor (R3)1Is relative to T1At the moment of time of the voltage, V, across the measuring resistor (R3)0The voltage across the measurement resistor (R3) is measured at a time relative to zero.
5. The power supply system low frequency insulation detection device of claim 4, wherein: and the charging and discharging time of the branch distributed capacitor (C) is 5 tau.
6. The power supply system low frequency insulation detection device according to any one of claims 2, 3 or 5, characterized in that: the detection and calculation unit (3) detects steady-state voltage signals of two ends of the measuring resistor (R3) in the first half period of the periodic square wave pulse signal, and the resistance value R of the insulation resistor in the first half period is obtained through calculation+And detecting a steady-state voltage signal of two ends of the measuring resistor (R3) in the latter half period of the periodic square wave pulse signal, and calculating to obtain the resistance value R of the insulation resistor in the latter half period-Finally, R is taken as the effective value of the insulation resistance,and the detection calculation unit (3) judges whether the tested power supply system has insulation fault according to the effective value of the insulation resistance.
7. The power supply system low frequency insulation detection device of claim 6, wherein:
resistance R of the insulation resistor in the first half period+Calculated according to the following formula:
<mrow> <msub> <mi>R</mi> <mo>+</mo> </msub> <mo>=</mo> <mfrac> <mrow> <msub> <mi>E</mi> <mi>m</mi> </msub> <mo>&times;</mo> <msub> <mi>R</mi> <mi>m</mi> </msub> </mrow> <msub> <mi>U</mi> <msub> <mi>R</mi> <mi>m</mi> </msub> </msub> </mfrac> <mo>-</mo> <msub> <mi>R</mi> <mi>i</mi> </msub> <mo>-</mo> <msub> <mi>R</mi> <mi>m</mi> </msub> <mo>;</mo> </mrow>
resistance R of the insulation resistor in the second half period-Calculated according to the following formula:
<mrow> <msub> <mi>R</mi> <mo>-</mo> </msub> <mo>=</mo> <mfrac> <mrow> <msub> <mi>E</mi> <mi>m</mi> </msub> <mo>&times;</mo> <msub> <mi>R</mi> <mi>m</mi> </msub> </mrow> <msub> <mi>U</mi> <msub> <mi>R</mi> <mi>m</mi> </msub> </msub> </mfrac> <mo>-</mo> <msub> <mi>R</mi> <mi>i</mi> </msub> <mo>-</mo> <msub> <mi>R</mi> <mi>m</mi> </msub> <mo>;</mo> </mrow>
wherein E ismIs the absolute value of the amplitude of the periodic square wave pulse signal,for measuring the voltage across a resistor (R3), RiIs the parallel resistance value of a first resistor (R1) and a second resistor (R2), RmTo measure the resistance of the resistor (R3).
8. The power supply system low frequency insulation detection device according to any one of claims 1, 2, 3, 5 or 7, characterized in that: the power supply system to be tested is a ship neutral point ungrounded power supply system.
9. A low-frequency insulation detection method for a power supply system is characterized by comprising the following steps:
the pulse signal source (G) sends out a pulse signal, and the pulse signal passes through the low-pass filtering unit (1) and the measuring resistor (R3) and is injected into a power supply system to be tested through the first resistor (R1) and the second resistor (R2);
and the detection calculation unit (3) calculates the insulation resistance of the power supply system to be detected to the ground by detecting signals at two ends of the measuring resistor (R3), and judges whether the power supply system to be detected has insulation faults or not according to the insulation resistance.
10. The power supply system low frequency insulation detection method of claim 9, characterized in that: the pulse signal sent by the pulse signal source (G) is a periodic square wave pulse signal with alternating positive and negative.
11. The power supply system low frequency insulation detection method of claim 10, wherein: under the action of periodic square wave pulse signals emitted by the pulse signal source (G), continuously charging and discharging a branch distributed capacitor (C) of the power supply system to be tested, wherein the branch distributed capacitor (C) is equivalent to isolation from the power supply system to be tested after charging is finished; the detection calculation unit (3) calculates the resistance values of the insulation resistors in the first half period and the second half period of the periodic square wave pulse signal, the average value of the resistance values of the insulation resistors in the first half period and the second half period is used as the effective value of the insulation resistor, and then whether the tested power supply system has insulation faults or not is judged.
12. The power supply system low-frequency insulation detection method according to claim 11, wherein the process of calculating the insulation resistance of the power supply system to be detected by the detection calculation unit (3) comprises:
the detection and calculation unit (3) detects steady-state voltage signals of two ends of the measuring resistor (R3) in the first half period of the periodic square wave pulse signal, and the resistance value R of the insulation resistor in the first half period is obtained through calculation+，Wherein E ismIs the absolute value of the amplitude of the periodic square wave pulse signal,for measuring the voltage across a resistor (R3), RiIs the parallel resistance value of a first resistor (R1) and a second resistor (R2), RmTo measure the resistance of the resistor (R3).
The detection and calculation unit (3) detects that the two ends of the measuring resistor (R3) are in periodic square wave pulseThe steady state voltage signal in the latter half period of the impulse signal is calculated to obtain the resistance value R of the insulation resistor in the latter half period-，
The detection calculation unit (3) takes R as an effective value of the insulation resistance,and judging whether the tested power supply system has insulation fault according to the effective value of the insulation resistance.
13. The power supply system low-frequency insulation detection method according to any one of claims 10, 11 or 12, wherein the pulse signal source (G) is capable of automatically adjusting the frequency of the periodic square-wave pulse signal, and the frequency of the periodic square-wave pulse signal emitted by the pulse signal source (G) is equal to
The detection calculation unit (3) uses T1Equally spaced samples of the voltage across the measuring resistor (R3) for each half pulse signal period of the spacing time0For measuring the voltage, V, across the resistor (R3) at a time relative to zero1Is relative to T1At the moment of time of the voltage, V, across the measuring resistor (R3)2Is relative to 2T1The voltage across the measuring resistor (R3) is measured at time.
14. The power supply system low frequency insulation detection method of claim 13, wherein: and the charging and discharging time of the branch distributed capacitor (C) is 5 tau.
15. The power supply system low frequency insulation detection method according to any one of claims 10, 11, 12 or 14, characterized by: the low-frequency insulation detection method of the power supply system is applied to the detection of the ground fault of the ship frequency converter system.
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| CN111426882A (en) * | 2020-05-13 | 2020-07-17 | 常熟瑞特电气股份有限公司 | RIM type insulation monitoring system |
| CN113092973A (en) * | 2019-12-23 | 2021-07-09 | 国创新能源汽车智慧能源装备创新中心(江苏)有限公司 | Insulation monitoring device and method of direct current IT system |
| CN113848490A (en) * | 2021-09-24 | 2021-12-28 | 中车长春轨道客车股份有限公司 | Storage battery pack insulation online detection system |
| CN119471055A (en) * | 2025-01-15 | 2025-02-18 | 北京四方继保工程技术有限公司 | Method, device and equipment for monitoring insulation resistance of energy storage system |
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