Capacitor voltage transformer dielectric loss on-line monitoring device and method

Abstract

The invention discloses a capacitor voltage transformer dielectric loss on-line monitoring device and method, and the device comprises a first electrode, a second electrode, a capacitor voltage transformer, a cross-core current transformer, a filter, an amplifier, a current detection unit, and a signal processing unit. The first electrode and the second electrode are both sleeved on a supporting column of the capacitive voltage transformer, the cross-core current transformer is arranged on a low-voltage side of the capacitive voltage transformer, the filter is connected with the first electrode and the second electrode, and the amplifier is connected with the filter and the signal processing unit. The current detection unit is respectively connected with the straight-through current transformer and the signal processing unit; the online monitoring method comprises the following steps of signal acquisition, amplitude ratio calculation, phase difference calculation, dielectric loss tangent value calculation, fluctuation analysis and alarm. According to the invention, accurate online monitoring of the dielectric loss of the capacitor voltage transformer is realized, and the sensitivity and reliability of system fault detection are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of power equipment monitoring and diagnosis, and in particular relates to an online monitoring device and method for dielectric loss of a capacitor voltage transformer. Background Art

[0002] The capacitance and vibration sound of the capacitive voltage transformer are items that must be tested and inspected according to regulations. The current bus comparison method requires wiring, investment and manpower consumption, which restricts its promotion and application. In the routine inspection process, the I vector sum of the grounding current N-end and the grounding current X-end of the low-voltage capacitor of the capacitive voltage transformer is equal to the high-voltage side capacitor current. Therefore, the current to ground of the N and X ends can be obtained, and the current and current ratio of the high and low voltage capacitors can be obtained. By comparing the changes in the secondary terminal voltage, it can be used to determine whether the capacitance is abnormal. However, this existing method requires secondary terminal voltage collection. Since the secondary terminal voltage involves electricity metering and protection, secondary voltage access is usually not allowed for safety reasons, which poses a challenge to the existing algorithm structure. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a capacitor voltage transformer dielectric loss online monitoring device and method that can realize accurate online monitoring of capacitor voltage transformer dielectric loss and improve the sensitivity and reliability of system fault detection.

[0004] The technical solution of the present invention is: an online monitoring device for dielectric loss of a capacitor voltage transformer, comprising: a first electrode, a second electrode, a capacitor voltage transformer, a through-core current transformer, a filter, an amplifier, a current detection unit and a signal processing unit, wherein the first electrode is located at the bottom of the capacitor voltage transformer and is grounded through a grounding wire, the second electrode is fixed above the first electrode and is connected to the signal processing unit, the first electrode is parallel to the second electrode, the first electrode and the second electrode are both mounted on a support column of the capacitor voltage transformer, the secondary terminal cable of the capacitor voltage transformer passes through the hollow area of ​​the second electrode and is led to an underground cable trench, the secondary terminal cable of the capacitor voltage transformer does not pass through the hollow area of ​​the first electrode, the through-core current transformer is arranged on the low-voltage side of the capacitor voltage transformer, the filter is respectively connected to the first electrode and the second electrode, the amplifier is respectively connected to the filter and the signal processing unit, and the current detection unit is respectively connected to the through-core current transformer and the signal processing unit.

[0005] Furthermore, the plane distance between the first electrode and the second electrode is not less than 10 cm.

[0006] Furthermore, the second electrode is connected and fixed to the first electrode via an insulating stud, and the second electrode is located above the terminal box of the capacitive voltage transformer.

[0007] Furthermore, the first electrode and the second electrode are connected to the filter through a voltage line.

[0008] Furthermore, the low-voltage side conductor of the capacitive voltage transformer passes through the hollow part of the through-core current transformer, and the output side of the through-core current transformer is connected to the current detection unit.

[0009] An online monitoring method for a capacitor voltage transformer dielectric loss online monitoring device comprises the following steps:

[0010] Step 1: signal acquisition, including the following steps:

[0011] S1. Voltage signal acquisition: using a voltage line installed on the first electrode and the second electrode to obtain a voltage signal between the two, and then amplifying it through an amplifier to obtain a final voltage signal;

[0012] S2. Current signal acquisition: Use a through-hole current transformer to measure the ground current on the low-voltage side of the capacitive voltage transformer and the primary current on the low-voltage transformer;

[0013] Step 2, amplitude ratio calculation, includes the following steps:

[0014] S3, the signal processing unit samples the grounding current on the low voltage side of the capacitor voltage transformer, the primary side current of the low voltage transformer and the final voltage signal, and calculates the amplitude ratio;

[0015] S4, recording the change in the ratio of the ground current to the primary current amplitude over a period of time;

[0016] S5. If the average value of the change in the ratio of the ground current to the primary current amplitude within a period of time exceeds 0.5% of the preset threshold, it is considered that the system is abnormal, indicating that the dielectric loss increases;

[0017] The calculation formula of the amplitude ratio is:

[0018]

[0019] Among them, I c2 Represents the magnitude of the ground current on the low voltage side of the capacitor voltage transformer, I p1 represents the amplitude of the primary current of the low-voltage transformer, E represents the maximum value of the final voltage signal, Δ 1 Indicates the change in the ratio of the ground current to the primary current amplitude over a period of time;

[0020] Step 3: Phase difference calculation, including the following steps:

[0021] S6, the signal processing unit processes the final voltage signal E and the ground current signal I on the low voltage side of the capacitive voltage transformerc2 and the low voltage transformer primary side current signal I p1 Analyze the phase and calculate the phase difference;

[0022] S7. If the phase difference deviates from the preset normal range, it indicates that the dielectric loss increases;

[0023] The calculation formula of the phase difference is:

[0024] ΔP c2 =P E -P c2

[0025] ΔP p1 =P E -P p1 ,

[0026] Among them, P E Indicates the phase of the final voltage signal, P c2 Indicates the phase of the ground current on the low voltage side of the capacitor voltage transformer, P p1 Indicates the phase of the primary current of the low voltage transformer, ΔP c2 Indicates the phase difference between the ground current on the low voltage side of the capacitor voltage transformer and the final voltage signal, ΔP p1 Indicates the phase difference between the primary current and the final voltage signal of the low voltage transformer;

[0027] Step 4: Calculation of dielectric loss tangent value, including the following steps:

[0028] S8, performing tangent calculation on the phase difference to obtain the tangent value of the phase difference between the ground current on the low voltage side of the capacitive voltage transformer and the final voltage signal and the tangent value of the phase difference between the primary side current of the low voltage transformer and the final voltage signal;

[0029] S9. If the tangent value exceeds the set dielectric loss threshold, it is considered that the dielectric loss of the capacitor voltage transformer is too large and further inspection and maintenance are required;

[0030] The calculation formula of the dielectric loss tangent value is:

[0031]

[0032] Among them, tan(ΔP c2 ) represents the tangent value of the phase difference between the ground current on the low voltage side of the capacitor voltage transformer and the final voltage signal, tan(ΔP p1 ) represents the tangent value of the phase difference between the primary current and the final voltage signal of the low-voltage transformer, ΔP c2 Indicates the phase difference between the ground current on the low voltage side of the capacitor voltage transformer and the final voltage signal, ΔPp1 Indicates the phase difference between the primary current and the final voltage signal of the low voltage transformer;

[0033] Step 5: Fluctuation analysis and alarm. The expression of the fluctuation analysis is:

[0034]

[0035] Among them, max(Δ 1 ) represents the maximum value of the change in the ratio of the ground current to the primary current amplitude over a period of time, min(Δ 1 ) represents the minimum value of the change in the amplitude ratio of the ground current to the primary current over a period of time. The fluctuation value is used to determine the stability of the current-voltage amplitude ratio;

[0036] The alarm condition is: if the fluctuation value exceeds 2% of the preset stability threshold, or the tangent value tan (ΔP c2 ) and the tangent value of the phase difference between the primary current and the final voltage signal of the low-voltage transformer (ΔP p1 ) exceeds the specified threshold, the system will issue an alarm to indicate that there is abnormal dielectric loss in the capacitive voltage transformer.

[0037] Furthermore, the phase P of the final voltage signal in step S7 is E The calculation formula is:

[0038] V in (t) = V 0 sin(ωt+φ E ),

[0039]

[0040] Among them, V in (t) represents the voltage signal at time t, V 0 represents the maximum value of the voltage signal, ω represents the angular frequency of the voltage signal, φ E Indicates the initial phase of the voltage signal, F(V in ) indicates V in The Fourier transform result of (t) is Indicates V in The real part of the Fourier transform result of (t), Indicates V in The imaginary part of the Fourier transform result of (t);

[0041] The V in The real part of the Fourier transform result of (t) The expression is:

[0042]

[0043] Among them, V in (t) represents the voltage signal at time t, ω represents the angular frequency of the voltage signal;

[0044] The V in The expression of the imaginary part of the Fourier transform result of (t) is:

[0045]

[0046] Among them, V in (t) represents the voltage signal at time t, and ω represents the angular frequency of the voltage signal.

[0047] Furthermore, the phase P of the grounding current on the low voltage side of the capacitor voltage transformer in step S7 is c2 The calculation formula is:

[0048] I c2 (t) = I 0 sin(ωt+φ c2 ),

[0049]

[0050] Among them, I c2 (t) represents the ground current signal on the low voltage side of the capacitor voltage transformer at time t, I 0 Represents the magnitude of the ground current on the low voltage side of the capacitor voltage transformer, φ c2 represents the initial phase of the ground current on the low voltage side of the capacitor voltage transformer, ω represents the angular frequency of the ground current signal, F(I c2 ) indicates I c2 The Fourier transform result of (t) is Indicates I c2 The real part of the Fourier transform result of (t), Indicates I c2 The imaginary part of the Fourier transform result of (t);

[0051] I c2 The real part of the Fourier transform result of (t) The expression is:

[0052]

[0053] Among them, I c2 (t) represents the ground current signal on the low voltage side of the capacitive voltage transformer at time t, and ω represents the angular frequency of the ground current signal;

[0054] Ic2 The imaginary part of the Fourier transform result of (t) The expression is:

[0055]

[0056] Among them, I c2 (t) represents the ground current signal on the low voltage side of the capacitive voltage transformer at time t, and ω represents the angular frequency of the ground current signal.

[0057] Furthermore, the phase P of the primary side current of the low voltage transformer in step S7 is p1 The calculation formula is:

[0058] I p1 (t) = I p1，0 sin(ωt+φ p1 ),

[0059]

[0060] Among them, I p1 (t) represents the primary side current signal of the low voltage transformer at time t, I p1,0 Represents the amplitude of the current signal on the primary side of the low-voltage transformer, φ p1 represents the initial phase of the primary current signal of the low voltage transformer, ω represents the angular frequency of the primary current signal, F(I p1 ) indicates I p1 The Fourier transform result of (t) is Indicates I p1 The real part of the Fourier transform result of (t), Indicates I p1 The imaginary part of the Fourier transform result of (t);

[0061] I p1 The real part of the Fourier transform result of (t) The expression is:

[0062]

[0063] Among them, I p1 (t) represents the primary current signal of the low-voltage transformer at time t, ω represents the angular frequency of the primary current signal;

[0064] I p1 The imaginary part of the Fourier transform result of (t) The expression is:

[0065]

[0066] Among them, I p1(t) represents the primary side current signal of the low voltage transformer at time t, and ω represents the angular frequency of the primary side current signal.

[0067] Beneficial effects of the present invention:

[0068] 1. High detection accuracy: The present invention realizes multi-dimensional signal monitoring by simultaneously collecting the grounding current on the low-voltage side of the capacitor voltage transformer, the primary current on the low-voltage transformer, and the voltage signal; by calculating the phase difference and amplitude ratio between the voltage and current signals, it can more intuitively reflect the change in dielectric loss caused by the change in the internal capacitance of the capacitor voltage transformer, effectively improving the accuracy of detection;

[0069] 2. Real-time online monitoring: The present invention realizes online real-time monitoring of the dielectric loss of the capacitive voltage transformer through the through-core current transformer and the signal processing unit, which can be completed without stopping or disassembling the equipment. Compared with the traditional offline test, online monitoring can timely discover potential faults and improve the operation safety of the equipment; at the same time, the system can continuously collect current and voltage signals and analyze the fluctuations in real time, which enables the device to identify the trend of increasing dielectric loss at an early stage and prevent the further expansion of the fault;

[0070] 3. Reduce manual intervention and maintenance costs: The signal processing unit of the present invention can automatically analyze indicators such as phase difference and amplitude ratio. When abnormal dielectric loss is detected, it can automatically send out an alarm signal without manual intervention. Compared with manual regular inspection and maintenance, it greatly reduces manual workload and maintenance costs. By setting a reasonable threshold, the system can trigger an alarm when the phase difference tangent value or amplitude ratio changes beyond the set range, ensuring the sensitivity and reliability of monitoring. This automatic alarm method based on data changes improves the timeliness of maintenance.

[0071] 4. Improved safety: The present invention indirectly obtains the capacitance current change information by comparing the low-voltage side grounding current with the primary side current, avoiding direct access to the secondary terminal voltage and improving the safety of system operation; the first electrode and the second electrode are designed to be arranged in parallel with the supporting column of the capacitive voltage transformer and fixed by insulating studs, thereby ensuring the stability and safety of the device. The first electrode is grounded and the second electrode is connected to the signal processing unit, reducing the risk of electric shock for operators;

[0072] 5. Strong environmental adaptability: The electrodes and transformers of the present invention are mounted on the supporting columns of the capacitive voltage transformer and connected to the underground cable trench. They can adapt to various harsh environments in power substations, such as high humidity, high temperature, etc., improve the durability of the equipment, and reduce equipment failures caused by environmental factors; the application of filters and amplifiers effectively removes high-frequency noise interference and ensures the purity of the signal, thereby improving the acquisition accuracy of current and voltage signals, so that the system can operate stably even in a strong electromagnetic interference environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 It is a structural schematic diagram of an online monitoring device for dielectric loss of a capacitive voltage transformer of the present invention.

[0074] Figure 2 The present invention is a schematic diagram of a capacitor voltage transformer branch structure of an online monitoring device for capacitor voltage transformer dielectric loss.

[0075] Figure 3 It is a structural schematic diagram of a first electrode or a second electrode of an online monitoring device for dielectric loss of a capacitive voltage transformer of the present invention. DETAILED DESCRIPTION

[0076] like Figure 1-3 As shown, an online monitoring device for dielectric loss of a capacitor voltage transformer includes: a first electrode, a second electrode, a capacitor voltage transformer, a through-core current transformer, a filter, an amplifier, a current detection unit and a signal processing unit, wherein the first electrode is located at the bottom of the capacitor voltage transformer and is grounded through a grounding wire, the second electrode is fixed above the first electrode and is connected to the signal processing unit, the first electrode is parallel to the second electrode, the first electrode and the second electrode are both mounted on a support column of the capacitor voltage transformer, the secondary terminal cable of the capacitor voltage transformer passes through the hollow area of ​​the second electrode and is led to an underground cable trench, the secondary terminal cable of the capacitor voltage transformer does not pass through the hollow area of ​​the first electrode, the through-core current transformer is arranged on the low-voltage side of the capacitor voltage transformer, the filter is respectively connected to the first electrode and the second electrode, the amplifier is respectively connected to the filter and the signal processing unit, and the current detection unit is respectively connected to the through-core current transformer and the signal processing unit.

[0077] Preferably, the plane distance between the first electrode and the second electrode is not less than 10 cm.

[0078] Preferably, the second electrode is connected and fixed to the first electrode via an insulating stud, and the second electrode is located above the terminal box of the capacitive voltage transformer.

[0079] Preferably, the first electrode and the second electrode are connected to the filter via a voltage line.

[0080] Preferably, the low-voltage side conductor of the capacitive voltage transformer passes through the hollow part of the through-core current transformer, and the output side of the through-core current transformer is connected to the current detection unit.

[0081] An online monitoring method for a capacitor voltage transformer dielectric loss online monitoring device comprises the following steps:

[0082] Step 1: signal acquisition, including the following steps:

[0083] S1. Voltage signal acquisition: using a voltage line installed on the first electrode and the second electrode to obtain a voltage signal between the two, and then amplifying it through an amplifier to obtain a final voltage signal;

[0084] S2. Current signal acquisition: Use a through-hole current transformer to measure the ground current on the low-voltage side of the capacitive voltage transformer and the primary current on the low-voltage transformer;

[0085] Step 2, amplitude ratio calculation, includes the following steps:

[0086] S3, the signal processing unit samples the grounding current on the low voltage side of the capacitor voltage transformer, the primary side current of the low voltage transformer and the final voltage signal, and calculates the amplitude ratio;

[0087] S4, recording the change in the ratio of the ground current to the primary current amplitude over a period of time;

[0088] S5. If the average value of the change in the ratio of the ground current to the primary current amplitude within a period of time exceeds 0.5% of the preset threshold, it is considered that the system is abnormal, indicating that the dielectric loss increases;

[0089] The calculation formula of the amplitude ratio is:

[0090]

[0091] Among them, I c2 Represents the magnitude of the ground current on the low voltage side of the capacitor voltage transformer, I p1 represents the amplitude of the primary current of the low-voltage transformer, E represents the maximum value of the final voltage signal, Δ 1 Indicates the change in the ratio of the ground current to the primary current amplitude over a period of time;

[0092] Step 3: Phase difference calculation, including the following steps:

[0093] S6, the signal processing unit processes the final voltage signal E and the ground current signal I on the low voltage side of the capacitive voltage transformer c2and the low voltage transformer primary side current signal I p1 Analyze the phase and calculate the phase difference;

[0094] S7. If the phase difference deviates from the preset normal range, it indicates that the dielectric loss increases;

[0095] The calculation formula of the phase difference is:

[0096] AP c2 =P E -P c2

[0097] ΔP p1 =P E -P p1 ,

[0098] Among them, P E Indicates the phase of the final voltage signal, P c2 Indicates the phase of the ground current on the low voltage side of the capacitor voltage transformer, P p1 Indicates the phase of the primary current of the low voltage transformer, ΔP c2 Indicates the phase difference between the ground current on the low voltage side of the capacitor voltage transformer and the final voltage signal, ΔP p1 Indicates the phase difference between the primary current and the final voltage signal of the low voltage transformer;

[0099] Step 4: Calculation of dielectric loss tangent value, including the following steps:

[0100] S8, performing tangent calculation on the phase difference to obtain the tangent value of the phase difference between the ground current on the low voltage side of the capacitive voltage transformer and the final voltage signal and the tangent value of the phase difference between the primary side current of the low voltage transformer and the final voltage signal;

[0101] S9. If the tangent value exceeds the set dielectric loss threshold, it is considered that the dielectric loss of the capacitor voltage transformer is too large and further inspection and maintenance are required;

[0102] The calculation formula of the dielectric loss tangent value is:

[0103]

[0104]

[0105] Among them, tan(ΔP c2 ) represents the tangent value of the phase difference between the ground current on the low voltage side of the capacitor voltage transformer and the final voltage signal, tan(ΔP p1 ) represents the tangent value of the phase difference between the primary current and the final voltage signal of the low-voltage transformer, ΔP c2Indicates the phase difference between the ground current on the low voltage side of the capacitor voltage transformer and the final voltage signal, ΔP p1 Indicates the phase difference between the primary current and the final voltage signal of the low voltage transformer;

[0106] Step 5: Fluctuation analysis and alarm. The expression of the fluctuation analysis is:

[0107]

[0108] Among them, max(Δ 1 ) represents the maximum value of the change in the ratio of the ground current to the primary current amplitude over a period of time, min(Δ 1 ) represents the minimum value of the change in the amplitude ratio of the ground current to the primary current over a period of time. The fluctuation value is used to determine the stability of the current-voltage amplitude ratio;

[0109] The alarm condition is: if the fluctuation value exceeds 2% of the preset stability threshold, or the tangent value tan (ΔP c2 ) and the tangent value of the phase difference between the primary current and the final voltage signal of the low-voltage transformer (ΔP p1 ) exceeds the specified threshold, the system will issue an alarm to indicate that there is abnormal dielectric loss in the capacitive voltage transformer.

[0110] Preferably, the phase P of the final voltage signal in step S7 is E The calculation formula is:

[0111] V in (t) = V 0 sin(ωt+φ E ),

[0112]

[0113] Among them, V in (t) represents the voltage signal at time t, V 0 represents the maximum value of the voltage signal, ω represents the angular frequency of the voltage signal, φ E Indicates the initial phase of the voltage signal, F(V in ) indicates V in The Fourier transform result of (t) is Indicates V in The real part of the Fourier transform result of (t), Indicates V in The imaginary part of the Fourier transform result of (t);

[0114] The V in The real part of the Fourier transform result of (t) The expression is:

[0115]

[0116] Among them, V in (t) represents the voltage signal at time t, ω represents the angular frequency of the voltage signal;

[0117] The V in The expression of the imaginary part of the Fourier transform result of (t) is:

[0118]

[0119] Among them, V in (t) represents the voltage signal at time t, and ω represents the angular frequency of the voltage signal.

[0120] Preferably, the phase P of the grounding current on the low voltage side of the capacitive voltage transformer in step S7 is c2 The calculation formula is:

[0121] I c2 (t) = I 0 sin(ωt+φ c2 ),

[0122]

[0123] Among them, I c2 (t) represents the ground current signal on the low voltage side of the capacitor voltage transformer at time t, I 0 Represents the magnitude of the ground current on the low voltage side of the capacitor voltage transformer, φ c2 represents the initial phase of the ground current on the low voltage side of the capacitor voltage transformer, ω represents the angular frequency of the ground current signal, F(I c2 ) indicates I c2 The Fourier transform result of (t) is Indicates I c2 The real part of the Fourier transform result of (t), Indicates I c2 The imaginary part of the Fourier transform result of (t);

[0124] I c2 The real part of the Fourier transform result of (t) The expression is:

[0125]

[0126] Among them, I c2 (t) represents the ground current signal on the low voltage side of the capacitive voltage transformer at time t, and ω represents the angular frequency of the ground current signal;

[0127] I c2 The imaginary part of the Fourier transform result of (t) The expression is:

[0128]

[0129] Among them, I c2 (t) represents the ground current signal on the low voltage side of the capacitive voltage transformer at time t, and ω represents the angular frequency of the ground current signal.

[0130] Preferably, the phase P of the primary side current of the low voltage transformer in step S7 is p1 The calculation formula is:

[0131] I p1 (t) = I p1，0 sin(ωt+φ p1 ),

[0132]

[0133] Among them, I p1 (t) represents the primary side current signal of the low voltage transformer at time t, I p1,0 Represents the amplitude of the current signal on the primary side of the low-voltage transformer, φ p1 represents the initial phase of the primary current signal of the low voltage transformer, ω represents the angular frequency of the primary current signal, F(I p1 ) indicates I p1 The Fourier transform result of (t) is Indicates I p1 The real part of the Fourier transform result of (t), Indicates I p1 The imaginary part of the Fourier transform result of (t);

[0134] I p1 The real part of the Fourier transform result of (t) The expression is:

[0135]

[0136] Among them, I p1 (t) represents the primary current signal of the low-voltage transformer at time t, ω represents the angular frequency of the primary current signal;

[0137] I p1 The imaginary part of the Fourier transform result of (t) The expression is:

[0138]

[0139] Among them, I p1 (t) represents the primary side current signal of the low voltage transformer at time t, and ω represents the angular frequency of the primary side current signal.

[0140] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An online monitoring device for dielectric loss of a capacitor voltage transformer, characterized in that: include: A first electrode, a second electrode, a capacitive voltage transformer, a through-core current transformer, a filter, an amplifier, a current detection unit and a signal processing unit, wherein the first electrode is located at the bottom of the capacitive voltage transformer and is grounded through a grounding wire, the second electrode is fixed above the first electrode and is connected to the signal processing unit, the first electrode is parallel to the second electrode, the first electrode and the second electrode are both mounted on a supporting column of the capacitive voltage transformer, the secondary terminal cable of the capacitive voltage transformer passes through a hollow area of ​​the second electrode and is led to an underground cable trench, the secondary terminal cable of the capacitive voltage transformer does not pass through the hollow area of ​​the first electrode, the through-core current transformer is arranged on the low-voltage side of the capacitive voltage transformer, the filter is respectively connected to the first electrode and the second electrode, the amplifier is respectively connected to the filter and the signal processing unit, and the current detection unit is respectively connected to the through-core current transformer and the signal processing unit.

2. The on-line monitoring device for dielectric loss of a capacitor voltage transformer according to claim 1, characterized in that: The plane distance between the first electrode and the second electrode is not less than 10 cm.

3. The on-line monitoring device for dielectric loss of a capacitor voltage transformer according to claim 1, characterized in that: The second electrode is connected and fixed to the first electrode via an insulating stud, and the second electrode is located above the terminal box of the capacitive voltage transformer.

4. The on-line monitoring device for dielectric loss of a capacitor voltage transformer according to claim 1, characterized in that: The first electrode and the second electrode are connected to the filter through a voltage line.

5. The on-line monitoring device for dielectric loss of a capacitor voltage transformer according to claim 1, characterized in that: The low-voltage side conductor of the capacitive voltage transformer passes through the hollow part of the through-core current transformer, and the output side of the through-core current transformer is connected to the current detection unit.

6. An online monitoring method for the online monitoring device for dielectric loss of a capacitor voltage transformer according to claim 1, characterized in that: The following steps are involved: Step 1: signal acquisition, including the following steps: S1. Voltage signal acquisition: using a voltage line installed on the first electrode and the second electrode to obtain a voltage signal between the two, and then amplifying it through an amplifier to obtain a final voltage signal; S2. Current signal acquisition: Use a through-hole current transformer to measure the ground current on the low-voltage side of the capacitive voltage transformer and the primary current on the low-voltage transformer; Step 2, amplitude ratio calculation, includes the following steps: S3, the signal processing unit samples the grounding current on the low voltage side of the capacitor voltage transformer, the primary side current of the low voltage transformer and the final voltage signal, and calculates the amplitude ratio; S4, recording the change in the ratio of the ground current to the primary current amplitude over a period of time; S5. If the average value of the change in the ratio of the ground current to the primary current amplitude within a period of time exceeds 0.5% of the preset threshold, it is considered that the system is abnormal, indicating that the dielectric loss increases; The calculation formula of the amplitude ratio is: Among them, I c2 Represents the magnitude of the ground current on the low voltage side of the capacitor voltage transformer, I p1 represents the amplitude of the primary current of the low-voltage transformer, E represents the maximum value of the final voltage signal, and Δ1 represents the change in the ratio of the ground current to the primary current amplitude over a period of time; Step 3: Phase difference calculation, including the following steps: S6, the signal processing unit processes the final voltage signal E and the ground current signal I on the low voltage side of the capacitive voltage transformer c2 and the low voltage transformer primary side current signal I p1 Analyze the phase and calculate the phase difference; S7. If the phase difference deviates from the preset normal range, it indicates that the dielectric loss increases; The calculation formula of the phase difference is: ΔP p1 =P E -P p1 , Among them, P E Indicates the phase of the final voltage signal, P c2 Indicates the phase of the ground current on the low voltage side of the capacitor voltage transformer, P p1 Indicates the phase of the primary current of the low voltage transformer, ΔP c2 Indicates the phase difference between the ground current on the low voltage side of the capacitor voltage transformer and the final voltage signal, ΔP p1 Indicates the phase difference between the primary current and the final voltage signal of the low voltage transformer; Step 4: Calculation of dielectric loss tangent value, including the following steps: S8, performing tangent calculation on the phase difference to obtain the tangent value of the phase difference between the ground current on the low voltage side of the capacitive voltage transformer and the final voltage signal and the tangent value of the phase difference between the primary side current of the low voltage transformer and the final voltage signal; S9. If the tangent value exceeds the set dielectric loss threshold, it is considered that the dielectric loss of the capacitor voltage transformer is too large and further inspection and maintenance are required; The calculation formula of the dielectric loss tangent value is: Among them, tan(ΔP c2 ) represents the tangent value of the phase difference between the ground current on the low voltage side of the capacitor voltage transformer and the final voltage signal, tan(ΔP p1 ) represents the tangent value of the phase difference between the primary current and the final voltage signal of the low-voltage transformer, ΔP c2 Indicates the phase difference between the ground current on the low voltage side of the capacitor voltage transformer and the final voltage signal, ΔP p1 Indicates the phase difference between the primary current and the final voltage signal of the low voltage transformer; Step 5: Fluctuation analysis and alarm. The expression of the fluctuation analysis is: Among them, max(Δ1) represents the maximum value of the change in the amplitude ratio of the ground current and the primary side current over a period of time, min(Δ1) represents the minimum value of the change in the amplitude ratio of the ground current and the primary side current over a period of time, and the fluctuation value is used to judge the stability of the current and voltage amplitude ratio; The alarm condition is: if the fluctuation value exceeds 2% of the preset stability threshold, or the tangent value tan (ΔP c2 ) and the tangent value of the phase difference between the primary current and the final voltage signal of the low-voltage transformer (ΔP p1 ) exceeds the specified threshold, the system will issue an alarm to indicate that there is abnormal dielectric loss in the capacitive voltage transformer.

7. The online monitoring method of the online monitoring device for dielectric loss of a capacitor voltage transformer according to claim 6, characterized in that: The phase P of the final voltage signal in step S7 E The calculation formula is: V in (t)=V0sin(ωt+φ E ), Among them, V in (t) represents the voltage signal at time t, V0 represents the maximum value of the voltage signal, ω represents the angular frequency of the voltage signal, φ E Indicates the initial phase of the voltage signal, F(V in ) indicates V in The Fourier transform result of (t) is Indicates V in The real part of the Fourier transform result of (t), Indicates V in The imaginary part of the Fourier transform result of (t); The V in The real part of the Fourier transform result of (t) The expression is: Among them, V in (t) represents the voltage signal at time t, ω represents the angular frequency of the voltage signal; The V in The expression of the imaginary part of the Fourier transform result of (t) is: Among them, V in (t) represents the voltage signal at time t, and ω represents the angular frequency of the voltage signal.

8. The online monitoring method of the online monitoring device for dielectric loss of a capacitor voltage transformer according to claim 6, characterized in that: The phase P of the grounding current on the low voltage side of the capacitor voltage transformer in step S7 is c2 The calculation formula is: I c2 (t)=I0sin(ωt+φ c2 ), Among them, I c2 (t) represents the ground current signal on the low voltage side of the capacitor voltage transformer at time t, I0 represents the amplitude of the ground current on the low voltage side of the capacitor voltage transformer, φ c2 represents the initial phase of the ground current on the low voltage side of the capacitor voltage transformer, ω represents the angular frequency of the ground current signal, F(I c2 ) indicates I c2 The Fourier transform result of (t) is Indicates I c2 The real part of the Fourier transform result of (t), Indicates I c2 The imaginary part of the Fourier transform result of (t); I c2 The real part of the Fourier transform result of (t) The expression is: Among them, I c2 (t) represents the ground current signal on the low voltage side of the capacitive voltage transformer at time t, and ω represents the angular frequency of the ground current signal; I c2 The imaginary part of the Fourier transform result of (t) The expression is: Among them, I c2 (t) represents the ground current signal on the low voltage side of the capacitive voltage transformer at time t, and ω represents the angular frequency of the ground current signal.

9. The online monitoring method of the online monitoring device for dielectric loss of a capacitor voltage transformer according to claim 6, characterized in that: The phase P of the primary side current of the low voltage transformer in step S7 p1 The calculation formula is: I p1 (t)=I p1,0 sin(ωt+φ p1 ), Among them, I p1 (t) represents the primary side current signal of the low voltage transformer at time t, I p1,0 Represents the amplitude of the current signal on the primary side of the low-voltage transformer, φ p1 represents the initial phase of the primary current signal of the low voltage transformer, ω represents the angular frequency of the primary current signal, F(I p1 ) indicates I p1 The Fourier transform result of (t) is Indicates I p1 The real part of the Fourier transform result of (t), Indicates I p1 The imaginary part of the Fourier transform result of (t); I p1 The real part of the Fourier transform result of (t) The expression is: Among them, I p1 (t) represents the primary current signal of the low-voltage transformer at time t, ω represents the angular frequency of the primary current signal; I p1 The imaginary part of the Fourier transform result of (t) The expression is: Among them, I p1 (t) represents the primary side current signal of the low voltage transformer at time t, and ω represents the angular frequency of the primary side current signal.

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