Capacitive equipment and monitoring device for insulation parameters of capacitive equipment

Abstract

The present invention relates to a capacitive device and a monitoring device for the insulation parameters of the capacitive device. The capacitive device comprises a main insulation capacitor C1, a capacitor C2, a reference voltage capacitor C3 and a capacitor C4 which are arranged in the capacitive device. Two ends of the main insulation capacitor C1 and the capacitor C2 which are connected in series are connected between a high voltage end and a grounding end of the capacitive device. Two ends of the reference voltage capacitor C3 and the capacitor C4 which are connected in series are connected between a high voltage end and a grounding end of the capacitive device. One end of the capacitor C2 connected to the main insulation capacitor C1 is a current signal output end, and one end of the capacitor C4 connected to the reference voltage capacitor C3 is a voltage signal output end, thereby improving the accuracy of measuring the insulation parameters of the capacitive device, without adding an additional current transformer, and without using a signal cable to connect to a voltage transformer to obtain a voltage signal. The monitoring device for the insulation parameters of the capacitive device is used for monitoring the capacitive device.

Description

Technical Field

[0001] The invention relates to the field of high-voltage electrical appliances, and in particular to a capacitive device and a device for monitoring insulation parameters of the capacitive device. Background Art

[0002] In the power system, capacitive equipment refers to equipment whose insulation structure can be regarded as a group of series capacitors. It accounts for a large proportion in substations, including bushings, lightning arresters, current transformers (CT), voltage transformers (PT), cable terminals and cable intermediate heads. During the operation of capacitive equipment, its insulating medium must withstand the effects of various factors such as heat, electricity, chemistry, and mechanics. The insulation of the equipment will inevitably deteriorate, which may lead to the loss of insulation function in severe cases, thus causing equipment failure and even power grid accidents.

[0003] The insulation status of capacitive equipment can be determined by detecting the dielectric loss and capacitance change of the equipment. The insulation test of capacitive equipment can be divided into offline and online types.

[0004] The offline test is performed using a dielectric loss meter, which has high measurement accuracy and is the most commonly used test method. However, its test circuit is not suitable for detecting the insulation status of capacitive equipment during equipment operation.

[0005] In the online monitoring method, a highly sensitive current transformer is used to couple the ground current of the capacitive device, and the voltage applied to the device is obtained from the secondary side of the voltage transformer (PT), so as to calculate the capacitance and dielectric loss of the measured capacitive device. When using PT to obtain voltage, a signal cable is required to connect the PT output to the device installation location. The signal cable is generally long, requires wiring on site, and is prone to interference. At the same time, the stability of the current transformer and PT will affect the accuracy of the dielectric loss measurement. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a capacitive device which can output a current signal and a voltage signal for monitoring the insulation parameters of the capacitive device respectively through capacitor C2 and capacitor C4, and the signal has good accuracy.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A capacitive device comprises a main insulating capacitor C1, a capacitor C2, a reference voltage capacitor C3 and a capacitor C4 which are arranged in the capacitive device, wherein two ends of the main insulating capacitor C1 and the capacitor C2 connected in series are connected between a high voltage end and a ground end of the capacitive device, and two ends of the reference voltage capacitor C3 and the capacitor C4 connected in series are connected between a high voltage end and a ground end of the capacitive device, an end of the capacitor C2 connected to the main insulating capacitor C1 is a current signal output end, and an end of the capacitor C4 connected to the reference voltage capacitor C3 is a voltage signal output end.

[0009] Preferably, it includes an insulating core, in which a plurality of capacitor screens alternately arranged with the insulating layer are embedded. The main insulating capacitor C1, capacitor C2, reference voltage capacitor C3 and capacitor C4 are all embedded in the insulating core, and are all composed of a plurality of capacitor screens embedded in the insulating core.

[0010] Preferably, the capacitive device is provided with a current signal interface and a voltage signal interface; the current signal output terminal between the main insulating capacitor C1 and the capacitor C2 is connected to the current signal interface; the voltage signal output terminal between the reference voltage capacitor C3 and the capacitor C4 is connected to the voltage signal interface.

[0011] Preferably, the main insulating capacitor C1 is composed of a plurality of coaxial capacitor screens with gradually increasing diameters and alternately arranged with insulating layers; the capacitor C2 is composed of a group of capacitor screens arranged outside the outermost capacitor screen of the main insulating capacitor C1; the reference voltage capacitor C3 is composed of a group of mutually insulated and mutually overlapping capacitor screens wound or laid axially from the high-voltage end of the capacitive device to the ground end outside the capacitor screen of the corresponding main insulating capacitor C1; the capacitor C4 is composed of a group of capacitor screens wound outside the outermost capacitor screen of the reference voltage capacitor C3.

[0012] Preferably, the capacitive device is a bushing, a lightning arrester, a current transformer, a voltage transformer, a cable terminal or a cable intermediate head.

[0013] Preferably, the insulating core is formed by using glass fibers impregnated with epoxy resin as the insulating layer and a semi-conductive tape or a metal tape as the capacitive screen, and the insulating layer and the capacitive screen are alternately wound.

[0014] Preferably, the capacitive device is a sleeve, the sleeve includes a conductor, the insulating core is arranged outside the conductor, the upper flange and the lower flange are respectively provided at both ends of the insulating core, and the middle jacket of the insulating core is provided with a mounting flange; the main insulating capacitor C1 is composed of a plurality of coaxial capacitor screens which are alternately arranged with the insulating layer and have gradually increasing diameters and gradually shortening lengths, and the capacitor C2 is composed of a group of capacitor screens arranged outside the outermost capacitor screen of the main insulating capacitor C1; the reference voltage capacitor C3 is composed of a group of mutually insulated and mutually overlapping capacitor screens arranged outside the capacitor screen of the corresponding main insulating capacitor C1 along the axial direction from one end of the upper flange to the grounding end of the mounting flange, and the capacitor C4 is composed of a group of capacitor screens wound outside the outermost capacitor screen of the reference voltage capacitor C3.

[0015] Preferably, a current signal interface and a voltage signal interface are provided on the mounting flange of the sleeve; the first innermost capacitor screen of the main insulating capacitor C1 is electrically connected to the conductor at the same potential, the current signal output end between the main insulating capacitor C1 and capacitor C2 is connected to the current signal interface, and the outermost capacitor screen of capacitor C2 is connected to the ground terminal; the first innermost capacitor screen of the reference voltage capacitor C3 is electrically connected to conductor 1, the voltage signal output end between the reference voltage capacitor C3 and capacitor C4 is connected to the voltage signal interface, and the other end of capacitor C4 is connected to the ground terminal.

[0016] Preferably, the capacitive device is a lightning arrester, which includes multiple valve plates and an insulating core sleeved outside the multiple valve plates; the main insulating capacitor C1 and capacitor C2 are composed of multiple valve plates of the lightning arrester, and the reference voltage capacitor C3 and capacitor C4 are arranged inside the insulating core, and are composed of multiple capacitor screens alternately arranged in the insulating core and with the insulating layer.

[0017] Preferably, the main insulating capacitor C1 is formed by stacking a plurality of valve sheets in sequence, and the capacitor C2 is composed of at least one valve sheet stacked below the plurality of valve sheets of the main insulating capacitor C1.

[0018] Preferably, the reference voltage capacitor C3 is composed of a series of mutually insulated and overlapping capacitor screens arranged from one end to the other end of the insulating core; the capacitor C4 is composed of a group of capacitor screens arranged outside the outermost capacitor screen of the reference voltage capacitor C3.

[0019] Preferably, both ends of the insulating core are provided with lightning arrester incoming terminals and a lightning arrester base, the lightning arrester base is grounded and a current signal interface and a voltage signal interface are provided on the lightning arrester base; the lightning arrester incoming terminal is connected to the valve plate at the upper end of the main insulating capacitor C1, the upper end surface of the valve plate of capacitor C2 is connected to the current signal interface, and the valve plate of capacitor C2 is grounded through the lightning arrester base; the innermost capacitor screen of the reference voltage capacitor C3 is electrically connected to the lightning arrester incoming terminal at the same potential, the end of the reference voltage capacitor C3 and capacitor C4 is connected to the voltage signal interface, and the outermost capacitor screen of capacitor C4 is grounded through the lightning arrester base.

[0020] A monitoring device for insulation parameters of capacitive equipment is also provided, the measurement result of which is accurate and suitable for off-line monitoring and on-line monitoring of insulation parameters of capacitive equipment.

[0021] A capacitive device insulation parameter monitoring device of the present invention is used for monitoring capacitive devices, and comprises a current sampling unit, a voltage sampling unit and a capacitive device insulation parameter measuring device; the current sampling unit is connected to the current signal output end of the capacitive device, the voltage sampling unit is connected to the voltage signal output end of the capacitive device, and the output end of the current sampling unit and the output end of the voltage sampling unit are respectively connected to the capacitive device insulation parameter measuring device.

[0022] Preferably, the dielectric loss, or capacitance, or total current, or capacitive current, or resistive current of the capacitive device are monitored by using the signals of the capacitive device collected by the current sampling unit and the voltage sampling unit.

[0023] Preferably, the output end of the current sampling unit and the output end of the voltage sampling unit are integrated in a capacitive device insulation parameter measurement device.

[0024] Preferably, the current sampling unit is a resistive element and the input impedance of the current sampling unit is smaller than the impedance of the capacitor C2 , and the voltage sampling unit is a capacitive element and the input impedance of the voltage sampling unit is larger than the impedance of the capacitor C4 .

[0025] Preferably, the capacitive device insulation parameter measurement device performs the following operations after receiving the output signals of the current sampling unit and the voltage sampling unit:

[0026] The output signal of the current sampling unit is: U0;

[0027] I=U0 / Z1;

[0028] The phase offset parameter between the output signal U0 of the current sampling unit and the leakage current I is: Δθ0=θU0-θi;

[0029] Wherein, U0 is the output signal of the current sampling unit, I is the leakage current generated on the main insulation capacitor C1; Z1 is the input impedance of the current sampling unit; θU0 is the initial phase of the output signal of the current sampling unit; θi is the initial phase of I;

[0030] The output signal of the voltage sampling unit is: U1;

[0031] U=U1 / K;

[0032] The phase offset parameter between the output signal of the voltage sampling unit and the bus voltage is:

[0033] Δθ1=θU-θU1;

[0034] Among them, U1 is the output signal of the voltage signal output terminal, U is the bus voltage; K is the impedance voltage conversion coefficient of the voltage sampling unit; θU is the initial phase of the bus voltage; θU1 is the initial phase of the output signal of the voltage sampling unit;

[0035] The phase difference between the leakage current I and the bus voltage U is:

[0036] ΔθiU=θi-θU=θi-θU1-Δθ0-Δθ1;

[0037] The dielectric loss of the capacitive device is: tanδ=tan(90-ΔθiU);

[0038] The capacitance of the main insulating capacitor C1 of the capacitive device is:

[0039] The resistive current of the capacitive device is: Ir = I*sin(90-ΔθiU);

[0040] The capacitive current of the capacitive device is: Ic=I*cos(90-ΔθiU);

[0041] Where, f is the frequency of the bus voltage;

[0042] The total current is the leakage current I detected.

[0043] The capacitive device of the present invention forms at least four capacitors in the capacitive device, namely, a main insulating capacitor C1, a capacitor C2, a reference voltage capacitor C3 and a capacitor C4, wherein one end of the capacitor C2 connected to the main insulating capacitor C1 is a current signal output end, and one end of the capacitor C4 connected to the reference voltage capacitor C3 is a voltage signal output end, so that the current signal and the voltage signal of the capacitive device are collected inside the capacitive device, and the consistency is good, and there is no need to add an additional current transformer, and there is no need to obtain the voltage signal from the voltage transformer. Moreover, compared with the prior art of using coupling elements (such as current transformers and voltage transformers) to collect current signals and voltage signals, the output current signals and voltage signals of the present invention are more accurate, and will not be affected by the external environment (or are less affected by the external environment), and the influence of the coupling element's own error and stability on the measurement result is avoided, and the on-site installation of the device is simplified, so that the insulation parameters of the capacitive device of the present invention can be more accurately monitored, and the reliable and stable operation of the capacitive device is guaranteed. The capacitive device of the present invention can be a bushing, a lightning arrester, a current transformer (CT), a voltage transformer (PT), a cable terminal and a cable intermediate head, etc., which are devices with a capacitive voltage-dividing insulating structure. In addition, the capacitive device of the present invention is used to collect 4 capacitors of current signals and voltage signals, and the capacitors of existing capacitive devices are used. For example, when the capacitive device is a bushing, the main insulating capacitor C1 is the main insulating capacitor C1 for insulating voltage division that the bushing itself has, and at the same time, the function of signal collection of insulating voltage division is obtained, and the reference voltage capacitor C3 is a shielding capacitor for shielding external interference signals, and at the same time, the functions of shielding interference signals and collecting signals are obtained. For example, when the capacitive device is a lightning arrester, the main insulating capacitor C1 and the capacitor C2 both use the valve plate of the lightning arrester.

[0044] Compared with the existing method of measuring the insulation parameters of capacitive equipment by signal coupling, the monitoring device of the insulation parameters of the capacitive equipment of the present invention can improve the accuracy of the insulation parameter measurement of the capacitive equipment without changing the operation mode of the capacitive equipment, without adding an additional current transformer, and without using a signal cable to connect to the voltage transformer to obtain the voltage signal, effectively avoiding the influence of the error and performance of the signal-coupled current transformer and the voltage transformer in the prior art on the measurement result, and is suitable for offline monitoring and online monitoring of the insulation parameters of the capacitive equipment; and the current signal collected by the current sampling unit and the voltage signal collected by the voltage sampling unit are both from the inside of the capacitive equipment, avoiding or significantly reducing external interference, and having high consistency, which is conducive to further improving the accuracy of the monitoring result. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the internal structure of the casing of the present invention;

[0046] Figure 2It is a schematic diagram of the structure of the bushing of the present invention, which at least shows the connection relationship between the main insulation capacitor C1, the capacitor C2, the reference voltage capacitor C3, and the capacitor C4 and the current signal interface, the ground signal interface, and the voltage signal interface respectively;

[0047] Figure 3 The present invention Figure 2 A schematic diagram of the enlarged structure of part A;

[0048] Figure 4 is a schematic structural diagram of the arrester of the present invention, which at least shows the external structure of the arrester;

[0049] Figure 5 It is a schematic diagram of the internal structure of the arrester of the present invention;

[0050] Figure 6 The present invention Figure 5 A schematic diagram of the enlarged structure of part B;

[0051] Figure 7 It is a circuit structure schematic diagram of a monitoring device for insulation parameters of capacitive equipment of the present invention; DETAILED DESCRIPTION

[0052] The following is combined with Figure 1-7 The following embodiments are provided to further illustrate the specific implementation of the capacitive device of the present invention. The capacitive device of the present invention is not limited to the description of the following embodiments.

[0053] The capacitive device of the present invention comprises a main insulating capacitor C1, a capacitor C2, a reference voltage capacitor C3 and a capacitor C4 which are arranged in the capacitive device, wherein two ends of the main insulating capacitor C1 and the capacitor C2 connected in series are connected between a high voltage end and a grounding end of the capacitive device, and two ends of the reference voltage capacitor C3 and the capacitor C4 connected in series are connected between a high voltage end and a grounding end of the capacitive device, that is, two ends of the main insulating capacitor C1 and the capacitor C2 connected in series are connected in parallel with two ends of the reference voltage capacitor C3 and the capacitor C4 connected in series, one end of the capacitor C2 connected to the main insulating capacitor C1 is a current signal output end, and one end of the capacitor C4 connected to the reference voltage capacitor C3 is a voltage signal output end, and the signals output by the current signal output end and the voltage signal output end can be used for monitoring the capacitive device, thereby realizing online monitoring of dielectric loss, capacitance, total current, capacitive current and resistive current of the capacitive device.

[0054] The capacitive device of the present invention forms at least four capacitors in the capacitive device, namely, a main insulating capacitor C1, a capacitor C2, a reference voltage capacitor C3 and a capacitor C4, wherein one end of the capacitor C2 connected to the main insulating capacitor C1 is a current signal output end, and one end of the capacitor C4 connected to the reference voltage capacitor C3 is a voltage signal output end, so that the current signal and the voltage signal of the capacitive device are collected inside the capacitive device, and the consistency is good, and there is no need to arrange a coil outside the capacitive device, or to arrange an additional current transformer, and there is no need to use a signal cable to connect to the voltage transformer to obtain the voltage signal. Moreover, compared with the prior art of using coupling elements (such as current transformers, voltage transformers) to collect current signals and voltage signals, the output current signals and voltage signals of the present invention are more accurate, and will not be affected by the external environment (or are less affected by the external environment), and the influence of the coupling element's own error and stability on the measurement result is avoided, and the on-site installation of the device is simplified, so that the capacitive device of the present invention can be monitored more accurately, and the reliable and stable operation of the capacitive device is guaranteed.

[0055] Specifically, the main insulating capacitor C1 and capacitor C2 are connected in series to form a current signal sampling capacitor group, and the reference voltage capacitor C3 and capacitor C4 are connected in series to form a voltage signal sampling capacitor group. The current signal sampling capacitor group and the voltage signal sampling capacitor group are connected in parallel between the high voltage end (bus voltage U) and the ground end (ground GND) of the capacitive device. The end of the capacitor C2 connected to the main insulating capacitor C1 is the current signal output end, and the end of the capacitor C4 connected to the reference voltage capacitor C3 is the voltage signal output end. Usually, the capacitance of the capacitor C2 needs to be much larger than the capacitance of the main insulating capacitor C1, and the capacitance of the capacitor C4 is much larger than the capacitance of the reference voltage capacitor C3.

[0056] Preferably, the capacitive device is provided with a wiring terminal connected to the high voltage end, a grounding end, a current signal interface 210 and a voltage signal interface 230; the current signal sampling capacitor group and the voltage signal sampling capacitor group are connected in parallel between the high voltage wiring terminal and the grounding end. The current signal output end of the capacitor C2 is connected to the current signal interface 210, and the other end of the capacitor C2 is connected to the grounding end; the voltage signal output end of the capacitor C4 is connected to the voltage signal interface 230, and the other end of the capacitor C4 is connected to the grounding end. The grounding end can be provided with a separate grounding signal interface 220, or the grounding signal interface 220 is not required to be provided, and is directly connected to the mounting flange or metal shell of the capacitive device as the grounding end. The current signal interface 210 and the voltage signal interface 230 are usually provided on the mounting flange of the capacitive device, and a separate grounding interface line 220 can also be provided on the mounting flange. Of course, the current signal interface 210 and the voltage signal interface 230 can also be provided in an insulating housing or other convenient wiring position as needed. The capacitive device of the present invention, its current signal interface 210, ground signal interface 220 and voltage signal interface 230 are conducive to simplifying the wiring operation of the capacitive device.

[0057] The capacitive device of the present invention can be a bushing, a lightning arrester, a current transformer (CT), a voltage transformer (PT), a cable terminal and a cable intermediate head, etc., which are devices with a capacitive voltage-dividing insulation structure. A preferred solution is that the capacitive device includes an insulating core, in which a plurality of capacitive screens alternately arranged with the insulating layer are embedded, and the main insulating capacitor C1, capacitor C2, reference voltage capacitor C3 and capacitor C4 are all embedded in the insulating core, and are all composed of a plurality of capacitive screens embedded in the insulating core. A preferred solution is an insulating core, which uses glass fibers impregnated with epoxy resin as the insulating layer, a semi-conductive tape or a metal tape as the capacitive screen, and an insulating layer and a capacitive screen are alternately wound to form a sleeve-type insulating core.

[0058] Preferably, the main insulating capacitor C1 is composed of a plurality of coaxial capacitor screens with gradually increasing diameters and alternately arranged with the insulating layer, which plays the role of insulating voltage division; the capacitor C2 is composed of a group of capacitor screens arranged outside the outermost capacitor screen of the main insulating capacitor C1; the reference voltage capacitor C3 is composed of a group of mutually insulated and mutually overlapping capacitor screens wound or laid outside the capacitor screen of the corresponding main insulating capacitor C1 along the axial direction from the wiring terminal of the high-voltage end to the ground end, and at the same time plays the role of shielding interference signals; the capacitor C4 is composed of a group of capacitor screens wound outside the outermost capacitor screen of the reference voltage capacitor C3. Of course, the capacitor C2 can also be a capacitor tap of the main insulating capacitor C1, that is, a capacitor tap connected to the second to last screen of the main insulating capacitor C1, and the capacitor C2 is formed by the last two capacitor screens (or the last few screens) of the main insulating capacitor C1; similarly, the capacitor C4 can also be a capacitor tap of the reference voltage capacitor C3.

[0059] The following will be combined Figure 1-3 , taking the bushing as an example, the capacitive device of the present invention is further explained.

[0060] like Figure 1-3 As shown, the capacitive device is a bushing, which includes a conductor 1 and an insulating core wrapped around the conductor 1, a main insulating capacitor C1, a capacitor C2, a reference voltage capacitor C3 and a capacitor C4 are arranged inside the insulating core, and an insulating outer sheath is arranged outside the insulating core. The main insulating capacitor C1, the capacitor C2, the reference voltage capacitor C3 and the capacitor C4 are all arranged inside the insulating core, and are composed of a plurality of capacitive screens alternately arranged inside the insulating core and with the insulating layer.

[0061] Preferably, Figure 1 As shown, the bushing also includes an incoming terminal 10, an outgoing terminal 11, an upper flange 12, a lower flange 13, and a mounting flange 15; the insulating core is arranged outside the conductor 1, and the upper flange 12 and the lower flange 13 are respectively arranged at both ends of the insulating core, and the middle of the insulating core is covered with a mounting flange 15, and the insulating core is located on the upper side of the mounting flange 15 and is also covered with a tightly crimped insulating outer sheath, the incoming terminal 10 is connected to the conductor 1 and arranged at one end of the upper flange 12, and the outgoing terminal 11 is connected to the conductor 1 and arranged at one end of the lower flange 13. Preferably, the insulating outer sheath is a silicone rubber umbrella skirt 14, the upper flange 12 is a Jiang Jun seat, and the lower flange 13 is a pressure equalizing ball.

[0062] like Figure 1 As shown, the main insulating capacitor C1 is composed of a plurality of coaxial capacitor screens with gradually increasing diameters and gradually decreasing lengths, which are alternately arranged with the insulating layer. The main insulating capacitor C1 plays a core role in voltage division insulation; the capacitor C2 is composed of a group of capacitor screens wound outside the outermost capacitor screen of the main insulating capacitor C1, and the capacitance of the capacitor C2 is much greater than that of the main insulating capacitor C1. The main insulating capacitor C1 and the capacitor C2 are arranged in the insulating core to extract the monitoring signal, which belongs to the prior art and will not be described in detail here.

[0063] The improvement of the present invention mainly lies in that a reference voltage capacitor C3 and a capacitor C4 are added to the insulating core. Preferably, the reference voltage capacitor C3 is composed of a series of mutually insulated and mutually overlapping capacitor screens wound or laid along the axial direction from one end of the upper flange to the grounding end of the mounting flange 15 while making the main insulating capacitor C1. The capacitor screen of the reference voltage capacitor C3 is wound or laid outside the capacitor screen of the corresponding main insulating capacitor C1, and is continuously offset and mutually overlapped from the wiring terminal of the high-voltage end along the axial direction; the capacitor C4 is composed of a group of capacitor screens wound outside the outermost capacitor screen of the reference voltage capacitor C3. The reference voltage capacitor C3 plays a role in shielding interference signals, and the capacitance of the capacitor C4 is much greater than the capacitance of the reference voltage capacitor C3. Of course, the reference voltage capacitor C3 can also adopt other setting methods, that is, other winding methods that may not achieve a shielding effect, such as a group of coaxial capacitor screens wound outside the main insulating capacitor C1, which still belongs to the protection scope of the present invention.

[0064] Specifically, Figure 1 In the direction shown, the capacitor screens of the reference voltage capacitor C3 are alternately wound or laid on the outside of the main insulating capacitor C1 with the insulating layer from the upper end to the lower end of the insulating core, and the adjacent capacitor screens are insulated from each other and overlap each other, and the multiple capacitor screens of the reference voltage capacitor C3 are successively offset downward from top to bottom along the axial direction of the conductor 1, that is, of the two adjacent capacitor screens, the lower end of the upper capacitor screen is located in the lower capacitor screen, and the lower end of the upper capacitor screen is overlapped with the upper end of the lower capacitor screen.

[0065] Preferably, the capacitor C2 is a capacitor tap of the main insulating capacitor C1, that is, a capacitor tap connected to the second to last screen (or the last few screens) of the main insulating capacitor C1, and the capacitor C2 is formed by the last two capacitor screens (or the last few screens) of the main insulating capacitor C1; or the capacitor C2 is an independent capacitor connected in series with the main insulating capacitor C1, and is composed of a plurality of capacitor screens separately wound outside the main insulating capacitor C1 in parallel. The capacitor C4 is a capacitor tap of the reference voltage capacitor C3, that is, a capacitor tap connected to the second to last screen (or the last few screens) of the reference voltage capacitor C3, and is formed by the last two capacitor screens (or the last few screens) of the reference voltage capacitor C3, or the capacitor C4 is an independent capacitor connected in series with the reference voltage capacitor C3, and the capacitor C4 is composed of a plurality of capacitor screens separately wound outside the reference voltage capacitor C3 in parallel. The capacitor C2 is a capacitor tap of the main insulating capacitor C1, and the capacitor C4 is a capacitor tap of the reference voltage capacitor C3, which is conducive to simplifying the production process and operation of the capacitive device of the present invention and improving production efficiency. The capacitor C2 or the capacitor C4 adopts the structure of an independently wound capacitor, so as to facilitate adjustment of the output current signal and voltage signal as required.

[0066] Preferably, Figure 1-3As shown, a current signal interface 210, a ground signal interface 220 and a voltage signal interface 230 are provided on the mounting flange 15 of the bushing; the capacitor C2 is composed of a plurality of capacitor screens alternately wound with the insulating layer outside the main insulating capacitor C1, and the capacitor C4 is composed of a plurality of capacitor screens alternately wound with the insulating layer outside the reference voltage capacitor C3, and the capacitor C4 is composed of a plurality of capacitor screens alternately wound with the insulating layer outside the reference voltage capacitor C3, and the capacitor screen on the innermost side of the main insulating capacitor C1 is electrically connected to the conductor 1 at the same potential, the outermost capacitor screen of the main insulating capacitor C1 and one end of the capacitor C2 are connected to the current signal interface 210 through the current signal line 21, and the outermost capacitor screen of the capacitor C2 is connected to the ground signal interface 220 through the ground line 22. Since capacitor C2 is composed of capacitors composed of multiple capacitor screens connected in parallel, during actual connection, the multiple capacitor screens of capacitor C2 are alternately connected to the current signal line 21 and the ground line 22 in turn to achieve parallel connection (that is, in capacitor C2, the capacitor screen connected to the current signal line 21 is the first capacitor screen, and the capacitor screen connected to the ground line 22 is the second capacitor screen, and the first capacitor screen and the second capacitor screen are alternately arranged in turn).

[0067] The first innermost capacitor screen of the reference voltage capacitor C3 is electrically connected to the conductor 1, the outermost capacitor screen of the reference voltage capacitor C3 and one end of the capacitor C4 are connected to the voltage signal interface 230 through the voltage signal line 23, and the other end of the capacitor C4 is connected to the ground signal interface 220 through the ground line 22. In actual connection, multiple capacitor screens of the capacitor C4 are alternately connected to the voltage signal line 23 and the ground line 22 in sequence to achieve parallel connection (that is, in the capacitor C4, the capacitor screen connected to the voltage signal line is the third capacitor screen, the capacitor screen connected to the ground line 22 is the fourth capacitor screen, and the third capacitor screen and the fourth capacitor screen are alternately arranged in sequence).

[0068] Preferably, the insulating core of the sleeve is formed by alternately winding the insulating layer and the capacitive screen on the conductor 1 using glass fibers impregnated with epoxy resin as the insulating layer and a semi-conductive tape or a metal tape as the capacitive screen. Of course, it can also be formed by using a mold, embedding glass fibers and the capacitive screen, and then pouring epoxy resin.

[0069] The capacitive device of the present invention can be a bushing, a lightning arrester, a current transformer (CT), a voltage transformer (PT), a cable terminal and a cable intermediate head, etc., which are devices having an insulating core with a capacitive voltage-dividing insulating structure. Of course, different capacitive devices may have different layouts of the capacitive screen of the main insulating capacitor C1.

[0070] The following will be combined Figure 4-6 , taking the lightning arrester as an example, the capacitive device of the present invention is further explained.

[0071] like Figure 4-6As shown, the capacitive device is a lightning arrester, which includes multiple valve plates and an insulating core sleeved outside the multiple valve plates. The two ends of the insulating core are provided with a lightning arrester inlet terminal 10a and a lightning arrester base 11a. The lightning arrester inlet terminal 10a is a high-voltage end, and the lightning arrester base 11a is grounded as a grounding end. A silicone rubber umbrella skirt sheath 14a is sleeved on the insulating core. A main insulating capacitor C1, a capacitor C2, a reference voltage capacitor C3 and a capacitor C4 are arranged inside the insulating core of the lightning arrester. One embodiment is that, similar to the sleeve of the first embodiment, the main insulating capacitor C1, the capacitor C2, the reference voltage capacitor C3 and the capacitor C4 are all arranged inside the insulating core, and are composed of a plurality of capacitor screens alternately arranged with the insulating layer in the insulating core.

[0072] like Figure 5 As shown, a preferred solution of this embodiment, the main insulating capacitor C1 and capacitor C2 are composed of multiple valve plates of the lightning arrester, and the reference voltage capacitor C3 and capacitor C4 are arranged inside the insulating core, and are composed of multiple capacitor screens alternately arranged with the insulating layer in the insulating core.

[0073] The main insulating capacitor C1 is composed of multiple valve plates stacked in sequence, and the main insulating capacitor C1 is a valve plate capacitor; the capacitor C2 is composed of at least one valve plate under the multiple valve plates stacked on the main insulating capacitor C1, and the main insulating capacitor C1 and the capacitor C2 are connected in series. Figure 5 In the figure, the capacitor C2 is composed of a valve plate arranged between the main insulating capacitor C1 and the lightning arrester base 11a. The valve plate of the capacitor C2 is connected to the current signal interface 210 through the current signal line 21. The valve plate of the capacitor C2 serves as the current signal output end. The multiple valve plates can prevent the hazards of high transient overvoltage and play the role of current sampling. The capacitance of the capacitor C2 is much larger than that of the reference voltage capacitor C1.

[0074] The reference voltage capacitor C3 is composed of a series of mutually insulated and mutually overlapping capacitor screens wound or laid from one end of the arrester incoming line terminal 10a of the insulating core body close to the high-voltage end to the ground end of the other end. The capacitor screen of the reference voltage capacitor C3 is constantly offset and mutually overlapped from the arrester incoming line terminal 10a to the arrester base 11a along the axial direction of the main insulating capacitor C1. The reference voltage capacitor C3 is a voltage divider valve plate capacitor, which is connected in parallel with the main insulating capacitor C1 and also has the effect of improving the performance of the arrester; the capacitor C4 is composed of a group of capacitor screens arranged outside the outermost capacitor screen of the reference voltage capacitor C3, and the capacitance of the capacitor C4 is much larger than the reference voltage capacitor C3. Of course, the reference voltage capacitor C3 can also be wound using other structures, and C4 can also use the penultimate screen of the reference voltage capacitor C3 to connect the capacitor tap with a wire as the current signal interface 210.

[0075] Specifically, Figure 4-6As shown, the arrester incoming terminal 10a and the arrester base 11a are respectively arranged at the upper end and the lower end of the insulating core, the arrester base 11a is grounded, and the arrester base 11a is provided with a current signal interface 210 and a voltage signal interface 230; the arrester incoming terminal 10a is connected to the valve plate at the upper end of the main insulating capacitor C1, the upper end surface of the valve plate of the capacitor C2 is connected to the current signal interface 210 through the current signal line 21, and the valve plate of the capacitor C2 is grounded through the arrester base 11a.

[0076] The capacitor screen of the reference voltage capacitor C3 is shifted downward in sequence from the upper end to the lower end of the insulating core along the axial direction of the insulating core, and overlapped and insulated with each other; the capacitor C2 is arranged between the main insulating capacitor C1 and the arrester base 11a; the capacitor C4 is wound outside the lower end of the reference voltage capacitor C3 and is located above the capacitor C2. The innermost capacitor screen of the reference voltage capacitor C3 is electrically connected to the arrester inlet terminal 10a with the same potential, and the end of the reference voltage capacitor C3 and the capacitor C4 connected is connected to the voltage signal interface 230 through the voltage signal line 23, and the outermost capacitor screen of the capacitor C4 is grounded through the arrester base 11a.

[0077] like Figure 4 and 5 As shown, the arrester also includes a voltage-equalizing cover 12a and a compression spring 16a. The voltage-equalizing cover 12a is arranged between the arrester incoming line terminal 10a and the insulating core. A silicone rubber shed sheath 14a is tightly sleeved outside the insulating core. One end of the voltage-equalizing cover 12a is connected to the arrester incoming line terminal 10a, and the other end is connected to the silicone rubber shed sheath 14a. The compression spring 16a is arranged between the voltage-equalizing cover 12a and the valve plate of the main insulating capacitor C1, and the valve plate of the main insulating capacitor C1 is pressed against the arrester base 11a.

[0078] Preferably, the insulating core of the arrester is formed by alternately winding the insulating layer and the capacitive screen with glass fibers impregnated with epoxy resin as the insulating layer and a semi-conductive tape or a metal tape as the capacitive screen.

[0079] The invention also discloses a monitoring device for insulation parameters of capacitive equipment, which is used for monitoring the capacitive equipment of the invention.

[0080] like Figure 7As shown, the capacitive device insulation parameter monitoring device of the present invention comprises a current sampling unit 3, a voltage sampling unit 4 and a capacitive device insulation parameter measuring device 5; the current sampling unit 3 is connected to the current signal output end of the capacitive device, the voltage sampling unit 4 is connected to the voltage signal output end of the capacitive device, and the output end of the current sampling unit 3 and the output end of the voltage sampling unit 4 are respectively connected to the capacitive device insulation parameter measuring device 5. In a further preferred solution, the output end of the current sampling unit 3 and the output end of the voltage sampling unit 4 are integrated in the capacitive device insulation parameter measuring device 5 and connected to the capacitive device through a wire.

[0081] Compared with the existing method of measuring the insulation parameters of capacitive equipment by signal coupling, the monitoring device for the insulation parameters of capacitive equipment of the present invention can improve the accuracy of measuring the insulation parameters of capacitive equipment without changing the operation mode of the capacitive equipment, and does not need to add an additional current transformer, and does not need to use a signal cable to connect to the voltage transformer of the substation to obtain a voltage signal, which effectively avoids the influence of the error and performance of the signal-coupled current transformer and the voltage transformer in the prior art on the measurement result, and is suitable for online monitoring of the insulation parameters of capacitive equipment; and the current signal collected by the current sampling unit and the voltage signal collected by the voltage sampling unit are both from the inside of the capacitive equipment, so as to avoid or significantly reduce external interference, have high consistency, and be conducive to further improving the accuracy of the monitoring result.

[0082] Specifically, Figure 7As shown, the capacitive device insulation parameter monitoring device of the present invention can be used for online monitoring of capacitive devices. When in use, the high-voltage end of the capacitive device is connected to a high-voltage bus, whose voltage is the bus voltage U, and the grounding end is grounded GND. The capacitive device includes a main insulating capacitor C1, a capacitor C2, a reference voltage capacitor C3 and a capacitor C4. The main insulating capacitor C1 and the reference voltage capacitor C3 are connected in parallel between the bus voltage U and the ground GND. The capacitor C2 is connected in series between the main insulating capacitor C1 and the ground GND. The leakage current I is the current generated by applying the bus voltage U to the main insulating capacitor C1, and flows into the ground GND through C2. The capacitor C4 is connected in series between the reference voltage capacitor C3 and the ground GND. One input end of the current sampling unit 3 is connected to the current signal output end between the main insulating capacitor C1 and the capacitor C2, and the other input end is connected to the ground end. One input end of the voltage sampling unit 4 is connected to the voltage signal output end between the reference voltage capacitor C3 and the capacitor C4, and the other input end is connected to the ground end. The ground end can be directly connected to the flange of the capacitive device for grounding or grounded through the current sampling unit and the voltage sampling unit, that is, the two ends of the capacitor C2 are respectively connected to the input end of the current sampling unit 3, and the two ends of the capacitor C4 are respectively connected to the input end of the voltage sampling unit 4. The output end of the current sampling unit 3 and the output end of the voltage sampling unit 4 are respectively connected to the capacitive device insulation parameter measuring device 5. The capacitive device insulation parameter measuring device 5 is connected to the capacitive device insulation parameter measuring device through a signal cable, and based on the current sampling signal and the voltage sampling signal, the calculation of the capacitive device dielectric loss, and / or capacitance, and / or total current, and / or capacitive current, and / or resistive current is realized.

[0083] Preferably, the current sampling unit 3 is a resistive element and the input impedance of the current sampling unit 3 is much smaller than the impedance of the capacitor C2, such as the current sampling unit 3 includes a sampling resistor, and the voltage sampling unit 4 is a capacitive element and the input impedance of the voltage sampling unit 4 is much larger than the impedance of the capacitor C4, such as the voltage sampling unit 4 includes a sampling capacitor. Further, the input impedance of the current sampling unit 3 is much smaller than the impedance of the capacitor C2; the input impedance of the voltage sampling unit 4 is much larger than the impedance of the capacitor C4. Further preferably, the input impedance of the current sampling unit 3 is 0.5%-1.5%, preferably 1%, of the impedance of the capacitor C2; the input impedance of the voltage sampling unit 4 is 50-150 times, preferably 100 times, of the impedance of the capacitor C4. There is no phase shift between the output signal of the current sampling unit 3 and the leakage current I of the main insulation capacitor C1, or there is a stable phase shift parameter; there is no phase shift between the output signal of the voltage sampling unit 4 and the bus voltage U, or there is a stable phase shift parameter.

[0084] Preferably, after receiving the output signals of the current sampling unit 3 and the voltage sampling unit 4, the capacitive device insulation parameter measuring device 5 performs the following operations to calculate the dielectric loss, capacitance, total current, capacitive current and resistive current:

[0085] The output signal of the current sampling unit is: U0;

[0086] I=U0 / Z1;

[0087] The phase offset parameter between the output signal of the current sampling unit and the leakage current I of the main insulation capacitor C1 is: Δθ0=θU0-θi;

[0088] Among them, U0 is the output signal of the current sampling unit, I is the leakage current generated by applying the bus voltage U to the main insulation capacitor C1; Z1 is the input impedance of the current sampling unit, which is a known value; θU0 is the initial phase of the output signal of the current sampling unit; θi is the initial phase of I;

[0089] The output signal of the voltage sampling unit is: U1;

[0090] U=U1 / K;

[0091] The phase offset parameter between the output signal of the voltage sampling unit and the bus voltage is:

[0092] Δθ1=θU-θU1;

[0093] Among them, U1 is the output signal of the voltage signal output terminal of the capacitive device, U is the bus voltage; K is the impedance voltage conversion coefficient of the voltage sampling unit, which is a known value; θU is the initial phase of the bus voltage; θU1 is the initial phase of the output signal of the voltage sampling unit;

[0094] The phase difference between the leakage current I of the main insulating capacitor C1 and the bus voltage U is:

[0095] ΔθiU=θi-θU=θi-θU1-Δθ0-Δθ1;

[0096] The dielectric loss of the capacitive device is: tanδ=tan(90-ΔθiU);

[0097] The capacitance of the main insulating capacitor C1 of the capacitive device is:

[0098] The resistive current of the capacitive device is: Ir = I*sin(90-ΔθiU);

[0099] The capacitive current of the capacitive device is: Ic=I*cos(90-ΔθiU);

[0100] Where, f is the power signal frequency, that is, the frequency of the bus voltage;

[0101] The total current is the leakage current I detected.

[0102] Preferably, the capacitive device insulation parameter measuring device 5 comprises a signal processing unit, a data analysis unit, a data storage unit and an output transmission unit for sending the capacitive device insulation parameter to the client, which are respectively connected to the current sampling unit 3 and the voltage sampling unit 4. Further, the data analysis unit can be implemented by a software method using an existing control chip, the control chip is a microprocessor or a single-chip microcomputer, or the data analysis unit is implemented by a hardware circuit.

[0103] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A capacitive device, characterized in that: It includes a main insulating capacitor C1, a capacitor C2, a reference voltage capacitor C3 and a capacitor C4 arranged in a capacitive device, wherein two ends of the main insulating capacitor C1 and the capacitor C2 connected in series are connected between the high voltage end and the ground end of the capacitive device, and the main insulating capacitor C1 and the capacitor C2 form a current signal sampling capacitor group, and two ends of the reference voltage capacitor C3 and the capacitor C4 connected in series are connected between the high voltage end and the ground end of the capacitive device, and the reference voltage capacitor C3 and the capacitor C4 form a voltage signal sampling capacitor group, and one end of the capacitor C2 connected to the main insulating capacitor C1 is a current signal output end, and one end of the capacitor C4 connected to the reference voltage capacitor C3 is a voltage signal output end; The capacitive device also includes an insulating core, in which a reference voltage capacitor C3 and a capacitor C4 are arranged, and are composed of a plurality of capacitor screens alternately wound with the insulating layer in the insulating core; the reference voltage capacitor C3 is composed of a group of mutually insulated and mutually overlapping capacitor screens wound or laid axially from the high voltage end to the ground end of the capacitive device outside the corresponding main insulating capacitor C1, and the capacitor C4 is composed of a group of capacitor screens wound outside the outermost capacitor screen of the reference voltage capacitor C3.

2. The capacitive device according to claim 1, characterized in that: The insulating core is embedded with a plurality of capacitor screens alternately arranged with the insulating layer. The main insulating capacitor C1, capacitor C2, reference voltage capacitor C3 and capacitor C4 are all embedded in the insulating core and are composed of a plurality of capacitor screens embedded in the insulating core.

3. The capacitive device according to claim 1, characterized in that: The capacitive device is provided with a current signal interface (210) and a voltage signal interface (230); the current signal output end between the main insulating capacitor C1 and the capacitor C2 is connected to the current signal interface (210); and the voltage signal output end between the reference voltage capacitor C3 and the capacitor C4 is connected to the voltage signal interface (230).

4. The capacitive device according to claim 2, characterized in that: The main insulating capacitor C1 is composed of a plurality of coaxial capacitor screens with gradually increasing diameters and alternately arranged with insulating layers, and the capacitor C2 is composed of a group of capacitor screens arranged outside the outermost capacitor screen of the main insulating capacitor C1.

5. The capacitive device according to claim 1, characterized in that: The capacitive equipment is a bushing, a lightning arrester, a current transformer, a voltage transformer, a cable terminal or a cable intermediate head.

6. The capacitive device according to claim 2, characterized in that: The insulating core body is formed by using glass fibers impregnated with epoxy resin as insulating layers and semi-conductive tapes or metal tapes as capacitive screens, and the insulating layers and the capacitive screens are wound alternately.

7. The capacitive device according to claim 2, characterized in that: The capacitive device is a bushing, which includes a conductor (1), the insulating core is arranged outside the conductor (1), the two ends of the insulating core are respectively provided with an upper flange (12) and a lower flange (13), and the middle of the insulating core is provided with a mounting flange (15); the main insulating capacitor C1 is composed of a plurality of coaxial capacitor screens, which are arranged alternately with the insulating layer and have gradually increasing diameters and gradually decreasing lengths; the capacitor C2 is composed of a group of capacitor screens arranged outside the outermost capacitor screen of the main insulating capacitor C1; the reference voltage capacitor C3 is composed of a group of mutually insulated and mutually overlapping capacitor screens arranged outside the corresponding capacitor screen of the main insulating capacitor C1 along the axial direction from one end of the upper flange (12) to the grounding end of the mounting flange (15); and the capacitor C4 is composed of a group of capacitor screens wound outside the outermost capacitor screen of the reference voltage capacitor C3.

8. The capacitive device according to claim 7, characterized in that: A current signal interface (210) and a voltage signal interface (230) are provided on the mounting flange (15) of the bushing; the first capacitor screen on the innermost side of the main insulating capacitor C1 is electrically connected to the conductor (1) at the same potential, the current signal output end between the main insulating capacitor C1 and the capacitor C2 is connected to the current signal interface (210), and the outermost capacitor screen of the capacitor C2 is connected to the ground end; the first capacitor screen on the innermost side of the reference voltage capacitor C3 is electrically connected to the conductor (1), the voltage signal output end between the reference voltage capacitor C3 and the capacitor C4 is connected to the voltage signal interface (230), and the other end of the capacitor C4 is connected to the ground end.

9. The capacitive device according to claim 1, characterized in that: The capacitive device is a lightning arrester, which includes a plurality of valve plates and an insulating core sleeved outside the plurality of valve plates; the main insulating capacitor C1 and capacitor C2 are composed of the plurality of valve plates of the lightning arrester.

10. The capacitive device according to claim 9, characterized in that: The main insulating capacitor C1 is formed by stacking a plurality of valve sheets in sequence, and the capacitor C2 is formed by at least one valve sheet stacked below the plurality of valve sheets of the main insulating capacitor C1.

11. The capacitive device according to claim 9, characterized in that: The two ends of the insulating core are provided with a lightning arrester inlet terminal (10a) and a lightning arrester base (11a), the lightning arrester base (11a) is grounded and the lightning arrester base (11a) is provided with a current signal interface (210) and a voltage signal interface (230); the lightning arrester inlet terminal (10a) is connected to the valve plate at the upper end of the main insulating capacitor C1, the upper end surface of the valve plate of the capacitor C2 is connected to the current signal interface (210), and the valve plate of the capacitor C2 is grounded through the lightning arrester base (11a); the innermost capacitor screen of the reference voltage capacitor C3 is electrically connected to the lightning arrester inlet terminal (10a) at the same potential, the end of the reference voltage capacitor C3 connected to the capacitor C4 is connected to the voltage signal interface (230), and the outermost capacitor screen of the capacitor C4 is grounded through the lightning arrester base (11a).

12. A monitoring device for insulation parameters of capacitive equipment, characterized in that: Used to monitor the capacitive device described in any one of claims 1 to 11, comprising a current sampling unit (3), a voltage sampling unit (4) and a capacitive device insulation parameter measuring device (5); the current sampling unit (3) is connected to the current signal output end of the capacitive device, the voltage sampling unit (4) is connected to the voltage signal output end of the capacitive device, and the output end of the current sampling unit (3) and the output end of the voltage sampling unit (4) are respectively connected to the capacitive device insulation parameter measuring device (5).

13. The device for monitoring insulation parameters of capacitive equipment according to claim 12, characterized in that: The signals of the capacitive device collected by the current sampling unit and the voltage sampling unit (4) are used to monitor the dielectric loss, or capacitance, or total current, or capacitive current, and or resistive current of the capacitive device.

14. The device for monitoring insulation parameters of capacitive equipment according to claim 12, characterized in that: The output end of the current sampling unit (3) and the output end of the voltage sampling unit (4) are integrated in the capacitive device insulation parameter measuring device (5).

15. The device for monitoring insulation parameters of capacitive equipment according to claim 12, characterized in that: The current sampling unit (3) is a resistive element and the input impedance of the current sampling unit (3) is smaller than the impedance of the capacitor C2; the voltage sampling unit (4) is a capacitive element and the input impedance of the voltage sampling unit (4) is larger than the impedance of the capacitor C4.

16. The device for monitoring insulation parameters of capacitive equipment according to claim 13, characterized in that: After receiving the output signals of the current sampling unit (3) and the voltage sampling unit (4), the capacitive device insulation parameter measuring device (5) performs the following operations: The output signal of the current sampling unit is: U0; I=U0 / Z1; The phase offset parameter between the output signal U0 of the current sampling unit and the leakage current I is: Δθ0=θU0-θi; Wherein, U0 is the output signal of the current sampling unit, I is the leakage current generated on the main insulation capacitor C1; Z1 is the input impedance of the current sampling unit; θU0 is the initial phase of the output signal of the current sampling unit; θi is the initial phase of I; The output signal of the voltage sampling unit is: U1; U=U1 / K; The phase offset parameter between the output signal of the voltage sampling unit and the bus voltage is: Δθ1=θU-θU1; Among them, U1 is the output signal of the voltage signal output terminal, U is the bus voltage; K is the impedance voltage conversion coefficient of the voltage sampling unit; θU is the initial phase of the bus voltage; θU1 is the initial phase of the output signal of the voltage sampling unit; The phase difference between the leakage current I and the bus voltage U is: ΔθiU=θi-θU=θi-θU1-Δθ0-Δθ1; The dielectric loss of the capacitive device is: tanδ=tan(90-ΔθiU); The capacitance of the main insulating capacitor C1 of the capacitive device is: The resistive current of the capacitive device is: Ir = I*sin(90-ΔθiU); The capacitive current of the capacitive device is: Ic=I*cos(90-ΔθiU); Where, f is the frequency of the bus voltage; The total current is the leakage current I detected.

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