A cable cross-bonding grounding system connection state live testing device and method

Abstract

The application discloses a cable cross-connection grounding system connection state live-line testing device and method. A joint or terminal or grounding box copper bar containing an independent lead is selected as a position for coupling injection and current induction testing, a live-line testing device is installed, loop impedance of any phase branch plus parallel impedance of other two phase branches under two different frequencies is tested and obtained, simultaneous equations are established by using Ohm's law and characteristics that resistance and inductance are irrelevant to frequency, impedance and resistance of each branch are calculated, and whether the grounding system has a connection defect is judged according to the calculated impedance and resistance, so that the electrical connection state of the cable cross-connection grounding system can be live-line detected, and the method is simple, convenient and efficient.

Description

Technical Field

[0001] This invention relates to a live testing device and method for the connection status of a cable cross-interconnection grounding system, belonging to the technical field of power transmission and transformation equipment. Background Technology

[0002] In urban and long-distance underground power transmission cable lines, to suppress and reduce circulating currents in the cable's metallic sheath, a cross-connected grounding system using leads and copper busbars is required to commutate the phases of the cable's metallic sheath, thereby canceling out induced potentials and reducing induced circulating currents. When the connections of grounding leads and copper busbars within the cross-connected grounding system become loose, increasing contact resistance, it can easily cause suspended discharges within the cable's aluminum sheath or cable accessories, leading to cable faults. Traditional testing methods can only be conducted when the line is out of service, resulting in poor timeliness and limitations. Summary of the Invention

[0003] To overcome the shortcomings of the existing technology, the present invention provides a live testing device and method for the connection status of a cable cross-interconnection grounding system, which can detect the electrical connection status of the cable cross-interconnection grounding system under live conditions. It is simple, convenient and efficient to operate.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A live-line testing device for the connection status of a cable cross-interconnection grounding system includes:

[0006] A heterogeneous frequency excitation source is used to generate a heterogeneous alternating signal that is distinct from power frequency interference;

[0007] A current coupler is used to couple the alternating signal generated by the different frequency excitation source into the loop formed by any phase branch of the cable cross-interconnection grounding system and two other parallel phase branches connected in series.

[0008] The current testing device is used to measure the loop current formed by any phase branch of a cable cross-interconnection grounding system and two other parallel phase branches connected in series, and sends the measured current to the calculation module.

[0009] The excitation voltage test module is used to measure the output voltage of the heterogeneous frequency excitation source and send the measured voltage to the calculation module;

[0010] The arithmetic module is used to control the heterogeneous frequency excitation source to generate heterogeneous frequency alternating signals, and to calculate the loop impedance formed by any phase branch of the cable cross-interconnection grounding system and the other two parallel phase branches in series based on the received current and voltage.

[0011] Furthermore, the current testing device includes a current sensor, a first filtering module, and a current testing module connected in sequence. The current sensor is used to be detachably sleeved on the independent grounding lead connector or terminal of each branch phase of the grounding box of the cable cross-interconnection grounding system or on the copper busbar of the grounding box.

[0012] Furthermore, the current sensor has an openable and closable assembly structure, which allows the test lead or copper busbar to be inserted into the current sensor without disassembling the grounding lead or copper busbar.

[0013] Furthermore, the current coupler is used to be detachably connected to the independent grounding lead connector or terminal of each branch phase of the grounding box of the cable cross-interconnection grounding system or to the copper busbar of the grounding box.

[0014] Furthermore, the current coupler has an openable and closable assembly structure, which allows the test lead or copper busbar to be inserted into the current coupler without disassembling the grounding lead or copper busbar.

[0015] Furthermore, the current testing device has a testing accuracy better than 1A.

[0016] On the other hand, a method for testing the energized connection status of a cable cross-interconnection grounding system includes:

[0017] Using the aforementioned live test device for the connection status of the cable cross-interconnection grounding system, the loop impedance of any phase branch plus the parallel impedance of the other two phase branches was tested at two different frequencies.

[0018] Based on the tested loop impedance, Ohm's law is used to establish simultaneous impedance equations to calculate the impedance of the three-phase branch at two different frequencies.

[0019] Based on the impedance of the three-phase branch at two different frequencies, equations are constructed using Ohm's law and the inherent parameters of resistance and inductive reactance to calculate the resistance of the three-phase branch.

[0020] Based on the impedance of the three-phase branch at two different frequencies and the resistance of the three-phase branch, determine whether there is a connection defect in the grounding system.

[0021] Furthermore, the simultaneous impedance equations constructed based on the tested loop impedance are as follows:

[0022] ZA_F1+(ZB_F1*ZC_F1) / (ZB_F1+ZC_F1)=K1_F1

[0023] ZB_F1+(ZA_F1*ZC_F1) / (ZA_F1+ZC_F1)=K2_F1

[0024] ZC_F1+(ZA_F1*ZB_F1) / (ZA_F1+ZB_F1)=K3_F1

[0025] ZA_F2+(ZB_F2*ZC_F2) / (ZB_F2+ZC_F2)=K1_F2

[0026] ZB_F2+(ZA_F2*ZC_F2) / (ZA_F2+ZC_F2)=K2_F2

[0027] ZC_F2+(ZA_F2*ZB_F2) / (ZA_F2+ZB_F2)=K3_F2

[0028] Where F1 and F2 are two different frequencies; K1_F1 is the loop impedance of the first branch plus the parallel impedance of the second and third branches at frequency F1; K2_F1 is the loop impedance of the second branch plus the parallel impedance of the first and third branches at frequency F1; K3_F1 is the loop impedance of the third branch plus the parallel impedance of the first and second branches at frequency F1; K1_F2 is the loop impedance of the first branch plus the parallel impedance of the second and third branches at frequency F2; K2_F2 is the loop impedance of the third branch plus the parallel impedance of the first and second branches at frequency F1; The loop impedance at frequency F2 is the second branch plus the parallel impedance of the first and third branches; K3_F2 is the loop impedance at frequency F2 is the third branch plus the parallel impedance of the first and second branches; ZA_F1 is the impedance of the first branch at frequency F1; ZB_F1 is the impedance of the second branch at frequency F1; ZC_F1 is the impedance of the third branch at frequency F1; ZA_F2 is the impedance of the first branch at frequency F2; ZB_F2 is the impedance of the second branch at frequency F2; ZC_F2 is the impedance of the third branch at frequency F2.

[0029] Solving the simultaneous equations yields the impedances at frequencies F1 and F1 of the first branch, F1 and F1 of the second branch, F1 and F2 of the third branch, respectively.

[0030] Furthermore, the simultaneous equations based on the impedances of the three-phase branch at two different frequencies are as follows:

[0031] RA^2+(XA_F1)^2=ZA_F1^2

[0032] RA^2+(XA_F2)^2=ZA_F2^2

[0033] RB^2+(XB_F1)^2=ZB_F1^2

[0034] RB^2+(XB_F2)^2=ZB_F2^2

[0035] RC^2+(XC_F1)^2=ZC_F1^2

[0036] RC^2+(XC_F2)^2=ZC_F2^2

[0037] Wherein, RA is the resistance of the first branch; XA_F1 is the reactance of the first branch at frequency F1; XA_F2 is the reactance of the first branch at frequency F2; RB is the resistance of the second branch, XB_F1 is the reactance of the second branch at frequency F1; XB_F2 is the reactance of the second branch at frequency F2; RC is the resistance of the third branch, XC_F1 is the reactance of the third branch at frequency F1; XC_F2 is the reactance of the third branch at frequency F2; ZA_F1 is the impedance of the first branch at frequency F1; ZB_F1 is the impedance of the second branch at frequency F1; ZC_F1 is the impedance of the third branch at frequency F1; ZA_F2 is the impedance of the first branch at frequency F2; ZB_F2 is the impedance of the second branch at frequency F2; ZC_F2 is the impedance of the third branch at frequency F2.

[0038] Solving the simultaneous equations yields the resistances of the first branch RA, the second branch RB, and the third branch RC.

[0039] Furthermore, the step of determining whether there is a connection defect in the grounding system based on the impedance and resistance of the three-phase branch at two different frequencies includes:

[0040] If the ratio of any two of the impedances of the first, second, and third branches at the first frequency is greater than 1.2, or the ratio of any two of the impedances of the first, second, and third branches at the second frequency is greater than 1.2, or the ratio of any two of the resistances of the first, second, and third branches is greater than 1.2, or the resistance of any one of the first, second, and third branches is greater than 300mΩ, then the grounding system is judged to have a connection defect.

[0041] The beneficial technical effects achieved by this invention are as follows: This invention obtains the loop impedance of the first branch plus the parallel impedance of the second and third branches at two different frequencies, the loop impedance of the second branch plus the parallel impedance of the first and third branches, and the loop impedance of the third branch plus the parallel impedance of the first and second branches. Utilizing Ohm's law and the characteristic that resistance and inductance are independent of frequency, a simultaneous equation is established to calculate the impedance and resistance of each branch. Based on the impedance and resistance, the grounding system status is determined. This invention can detect the electrical connection status of a cross-connected grounding system of cables while the cables are energized. It is simple, convenient, and highly efficient. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure of the device of the present invention;

[0043] Figure 2 This is a schematic diagram of a cable cross-connection grounding system;

[0044] Figure 3 This is a schematic diagram of the test of the first branch of the cable cross-interconnection grounding system of the present invention;

[0045] Figure 4 This is the equivalent circuit diagram of the cable cross-interconnection grounding system of the present invention. Detailed Implementation

[0046] The present invention will be further described below with reference to specific embodiments. These embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0047] like Figure 1 As shown, a live testing device for the connection status of a cable cross-interconnection grounding system includes: a current coupler, a different frequency excitation source, a current testing device, an excitation voltage testing module, and a computing module.

[0048] A heterogeneous excitation source is used to generate a heterogeneous alternating signal that is distinct from power frequency interference.

[0049] A current coupler is used to couple the alternating signal generated by the different frequency excitation source into the circuit formed by connecting any phase branch of the cable cross-interconnection grounding system with two other parallel phase branches in series.

[0050] The current testing device is used to measure the loop current formed by any phase branch of a cable cross-interconnection grounding system and two other parallel phase branches connected in series, and sends the measured current to the calculation module.

[0051] The excitation voltage test module is used to measure the output voltage of the heterogeneous frequency excitation source and send the measured voltage to the calculation module.

[0052] The calculation module is connected to the frequency excitation source, the current test module, and the excitation voltage test module. It is used to control the frequency excitation source to generate frequency alternating signals and to calculate the loop impedance formed by any phase branch of the cable cross-interconnection grounding system and the other two parallel phase branches in series based on the received current and voltage.

[0053] Among them, the different frequency excitation source can emit different frequency alternating signals, including but not limited to sine waves, triangle waves, square waves, etc.

[0054] Current couplers can be installed and connected to the independent grounding lead connectors or terminals of each branch phase in the grounding box of the cable cross-interconnection grounding system, or to the copper busbar of the grounding box.

[0055] The current coupler has an openable assembly structure, which allows the test lead or copper busbar to be inserted into the current coupler without removing the grounding lead or copper busbar.

[0056] like Figure 1As shown, a second filter module is connected between the frequency excitation source and the current coupler. The second filter module is used to filter out power frequency interference signals other than the frequency signals generated by the frequency excitation source.

[0057] like Figure 1 As shown, the current testing device includes a current sensor, a first filtering module, and a current testing module connected in sequence.

[0058] The current sensor can be installed and connected to the independent grounding lead connector or terminal of each branch phase of the grounding box in the cable cross-interconnection grounding system, or to the copper busbar of the grounding box.

[0059] The current sensor adopts an openable assembly structure, which allows the test lead or copper busbar to be inserted into the current sensor without disassembling the grounding lead or copper busbar.

[0060] The current sensor is used to collect the frequency response signal. After the first filtering module filters out the power frequency interference signal, it is sent to the current testing module. The current testing module converts the collected signal into a digital current signal.

[0061] Among them, the current testing device has a testing accuracy better than 1A.

[0062] This invention also provides a method for testing the energized connection status of a cable cross-interconnection grounding system, comprising the following steps:

[0063] Step S1: Using the cable cross-interconnection grounding system connection state live test device, test the loop impedance of any phase branch impedance plus the parallel impedance of the other two phase branches at two different frequencies.

[0064] A schematic diagram of a cable cross-connection grounding system is shown below. Figure 2 As shown. Select the test location for the cross-connected grounding system under test. Select any direct grounding box or cross-connected protective grounding box of the cross-connected grounding system as the test location. The grounding box or accessory at the test location must meet the requirement of having a connector or terminal with independent leads or a copper busbar in the grounding box as the location for coupling injection and current induction testing. The test diagram for the first branch is shown below. Figure 3 As shown.

[0065] Install a live-line testing device for the cable cross-connection grounding system connection status and obtain the loop impedances at two different frequencies, F1 and F2, for the first branch plus the parallel impedances of the second and third branches, the second branch plus the parallel impedances of the first and third branches, and the third branch plus the parallel impedances of the first and second branches. The schematic diagram for the test of the loop impedance of the first branch plus the parallel impedances of the second and third branches is shown below. Figure 4 As shown. Specifically:

[0066] Install the current coupler and current sensor clamped to the independent grounding lead or copper busbar of the first branch phase, and test to obtain the loop impedances of the first branch plus the parallel impedances of the second and third branches at frequencies F1 and F2, respectively, K1_F1 and K1_F2.

[0067] Install the current coupler and current sensor to clamp the independent grounding lead or copper busbar of the second branch phase, and test to obtain the loop impedances of the second branch plus the parallel impedances of the first and third branches at frequencies F1 and F2, respectively, which are K2_F1 and K2_F2.

[0068] Install the current coupler and current sensor to clamp the independent grounding lead or copper busbar of the third branch phase, and test to obtain the loop impedances of the third branch plus the parallel impedance of the first and second branches at frequencies F1 and F2, respectively, which are K3_F1 and K3_F2.

[0069] Step S2: Based on the tested loop impedance, use Ohm's law to establish simultaneous impedance equations and calculate the impedance of the three-phase branch at two different frequencies.

[0070] Let the impedance of the first branch at frequency F1 be ZA_F1, the reactance be XA_F1 (in Ω), the impedance of the first branch at frequency F2 be ZA_F2, the reactance be XA_F2 (in Ω), and the resistance of the first branch be RA (in Ω).

[0071] Let the impedance of the second branch at frequency F1 be ZB_F1, the reactance be XB_F1 (in Ω), the impedance of the second branch at frequency F2 be ZB_F2, the reactance be XB_F2 (in Ω), and the resistance of the second branch be RB (in Ω).

[0072] Let the impedance of the third branch at frequency F1 be ZC_F1, the reactance be XC_F1, and the unit be Ω; let the impedance of the third branch at frequency F2 be ZC_F2, the reactance be XC_F2, and the unit be Ω; let the resistance of the third branch be RC, and the unit be Ω.

[0073] (1) Calculate ZA_F1, ZB_F1, ZC_F1.

[0074] According to Ohm's law, we can construct a simultaneous equation for the impedance:

[0075] ZA_F1+(ZB_F1*ZC_F1) / (ZB_F1+ZC_F1)=K1_F1

[0076] ZB_F1+(ZA_F1*ZC_F1) / (ZA_F1+ZC_F1)=K2_F1 (1)

[0077] ZC_F1+(ZA_F1*ZB_F1) / (ZA_F1+ZB_F1)=K3_F1

[0078] in,

[0079] K1_F1 is the loop impedance (Ω) obtained by the live test device for the connection status of the cable cross-interconnection grounding system at frequency F1, which is the first branch plus the parallel impedance of the second and third branches.

[0080] K2_F1 is the loop impedance (Ω) obtained by the live-line test device for the connection status of the cable cross-interconnection grounding system at frequency F1, which is the second branch plus the parallel impedance of the first and third branches.

[0081] K3_F1 is the loop impedance (in Ω) obtained by the live test device for the connection status of the cable cross-interconnection grounding system at frequency F1, which is the sum of the parallel impedances of the first and second branches in the third branch.

[0082] make:

[0083] ZB_F1 / ZA_F1=M1_F1 (2)

[0084] ZC_F1 / ZA_F1=M2_F1

[0085] Where M1_F1 is the ratio of ZB_F1 / ZA_F1, which is dimensionless; M2_F1 is the ratio of ZC_F1 / ZA_F1, which is dimensionless;

[0086] Substituting (2) into (1), we get:

[0087] K1_F1*M1_F1+(K1_F1-K2_F1)*M2_F1=K2_F1

[0088] K3_F1*M1_F1-K2_F1*M2_F1=-K3_F1+K2_F1

[0089] ZA_F1+(M1_F1*M2_F1) / (M1_F1+M2_F1)ZA_F1=K1_F1

[0090] Solving the system of equations simultaneously yields ZA_F1, ZB_F1, ZC_F1, M1_F1, and M2_F1.

[0091] (2) Calculate ZA_F2, ZB_F2, ZC_F2.

[0092] According to Ohm's law, we can construct a simultaneous equation for the impedance:

[0093] ZA_F2+(ZB_F2*ZC_F2) / (ZB_F2+ZC_F2)=K1_F2

[0094] ZB_F2+(ZA_F2*ZC_F2) / (ZA_F2+ZC_F2)=K2_F2 (3)

[0095] ZC_F2+(ZA_F2*ZB_F2) / (ZA_F2+ZB_F2)=K3_F2

[0096] in,

[0097] K1_F2 is the loop impedance (in Ω) obtained by the live-line test device for the connection status of the cable cross-interconnection grounding system at frequency F2, which is the first branch plus the parallel impedance of the second and third branches.

[0098] K2_F2 is the loop impedance (in Ω) obtained by the live-line test device for the connection status of the cable cross-interconnection grounding system at frequency F2, which is the second branch plus the parallel impedance of the first and third branches.

[0099] K3_F2 is the loop impedance (in Ω) obtained by the live test device for the connection status of the cable cross-interconnection grounding system at frequency F2, which is the sum of the parallel impedances of the first and second branches in the third branch.

[0100] make:

[0101] ZB_F2 / ZA_F2=M1_F2 (4)

[0102] ZC_F2 / ZA_F2=M2_F2

[0103] in,

[0104] M1_F1 is the ratio of ZB_F1 / ZA_F1, which is dimensionless;

[0105] M2_F1 is the ratio of ZC_F1 / ZA_F1, which is dimensionless;

[0106] Substituting (4) into (3), we get:

[0107] K1_F2*M1_F2+(K1_F2-K2_F2)*M2_F2=K2_F2

[0108] K3_F2*M1_F2-K2_F2*M2_F2=-K3_F2+K2_F2

[0109] ZA_F2+(M1_F2*M2_F2) / (M1_F2+M2_F2)ZA_F2=K1_F2

[0110] Solving the simultaneous equations yields ZA_F2, ZB_F2, and ZC_F2.

[0111] Step S3: Based on the impedance of the three-phase branch at two different frequencies, use Ohm's law and the inherent parameters of resistance and inductive reactance to form a simultaneous equation and calculate the resistance of the three-phase branch.

[0112] Based on the solved ZA_F1 and ZA_F2, and using Ohm's law and the inherent parameters of resistance and inductive reactance, the following equations are constructed:

[0113] RA^2+(XA_F1)^2=ZA_F1^2

[0114] RA^2+(XA_F2)^2=ZA_F2^2

[0115] Solve the equation to obtain the resistance value of RA.

[0116] Similarly, based on the solved ZB_F1 and ZB_F2, the equations are constructed as follows:

[0117] RB^2+(XB_F1)^2=ZB_F1^2

[0118] RB^2+(XB_F2)^2=ZB_F2^2

[0119] The resistance value of RB is obtained by solving the simultaneous equations.

[0120] Based on the solved ZC_F1 and ZC_F2, the equations are constructed as follows:

[0121] RC^2+(XC_F1)^2=ZC_F1^2

[0122] RC^2+(XC_F2)^2=ZC_F2^2

[0123] The RC resistance value is obtained by solving the simultaneous equations.

[0124] Step S4: Based on the impedance of the three-phase branch at two different frequencies and the resistance of the three-phase branch, determine whether there is a connection defect in the grounding system.

[0125] If any of the following conditions are met, it can be determined whether there is a connection defect in the grounding system:

[0126] (1) The ratio of any two of ZA_F1, ZB_F1, and ZC_F1 is greater than 1.2;

[0127] (2) The ratio of any two of ZA_F2, ZB_F2, and ZC_F2 is greater than 1.2;

[0128] (3) The ratio of any two of RA, RB and RC is greater than 1.2;

[0129] (4) RA, RB and RC, any value of resistance greater than 300mΩ.

[0130] Example

[0131] The following is the testing procedure for a cross-connection grounding system of a cable line:

[0132] Select the test location for the cross-connection grounding system under test. Install the live-line test device for the connection status of the cable cross-connection grounding system and measure and obtain the loop impedance, specifically:

[0133] (1) At the test location, clamp the independent grounding lead or copper busbar of the first branch phase with the current coupler and current sensor of the cable cross-interconnection grounding system connection state live test device; use the cable cross-interconnection grounding system connection state live test device to obtain the loop impedances of the first branch plus the parallel impedances of the second and third branches at frequencies F1 and F2, respectively, K1_F1 and K1_F2. The test wiring is as follows: Figure 3 As shown.

[0134] (2) At the test location, clamp the independent grounding lead or copper busbar of the second branch phase with the current coupler and current sensor of the cable cross-interconnection grounding system connection state live test device; use the cable cross-interconnection grounding system connection state live test device to test and obtain the loop impedances of the second branch plus the parallel impedances of the first and third branches at frequencies F1 and F2, respectively, K2_F1 and K2_F2.

[0135] (3) At the test location, clamp the independent grounding lead or copper busbar of the third branch phase with the current coupler and current sensor of the cable cross-interconnection grounding system connection state live test device; use the cable cross-interconnection grounding system connection state live test device to test and obtain the loop impedances of the third branch plus the parallel impedance of the first and second branches at frequencies F1 and F2, respectively, which are K3_F1 and K3_F2.

[0136] The values ​​obtained from the test are as follows:

[0137] F1 = 70Hz; F2 = 110Hz

[0138] K1_F1=2.061Ω

[0139] K2_F1=0.423Ω

[0140] K3_F1=0.422Ω

[0141] K1_F2=2.092Ω

[0142] K2_F2=0.632Ω

[0143] K3_F2=0.630Ω

[0144] According to Ohm's law, establish a system of equations to calculate the impedance and resistance of each branch:

[0145] (1) Calculate ZA_F1, ZB_F1, ZC_F1.

[0146] According to Ohm's law, we can construct a simultaneous equation for the impedance:

[0147] ZA_F1+(ZB_F1*ZC_F1) / (ZB_F1+ZC_F1)=K1_F1

[0148] ZB_F1+(ZA_F1*ZC_F1) / (ZA_F1+ZC_F1)=K2_F1

[0149] ZC_F1+(ZA_F1*ZB_F1) / (ZA_F1+ZB_F1)=K3_F1

[0150] make:

[0151] ZB_F1 / ZA_F1=M1_F1

[0152] ZC_F1 / ZA_F1=M2_F1

[0153] in,

[0154] M1_F1 is the ratio of ZB_F1 / ZA_F1, which is dimensionless;

[0155] M2_F1 is the ratio of ZC_F1 / ZA_F1, which is dimensionless;

[0156] but:

[0157] K1_F1*M1_F1+(K1_F1-K2_F1)*M2_F1=K2_F1

[0158] K3_F1*M1_F1-K2_F1*M2_F1=-K3_F1+K2_F1

[0159] ZA_F1+(M1_F1*M2_F1) / (M1_F1+M2_F1)ZA_F1=K1_F1

[0160] Solving the system of equations simultaneously yields:

[0161] ZA_F1=1.950Ω

[0162] ZB_F1=0.226Ω

[0163] ZC_F1=0.218Ω

[0164] (2) Calculate ZA_F2, ZB_F2, ZC_F2.

[0165] According to Ohm's law, we can construct a simultaneous equation for the impedance:

[0166] ZA_F2+(ZB_F2*ZC_F2) / (ZB_F2+ZC_F2)=K1_F2

[0167] ZB_F2+(ZA_F2*ZC_F2) / (ZA_F2+ZC_F2)=K2_F2

[0168] ZC_F2+(ZA_F2*ZB_F2) / (ZA_F2+ZB_F2)=K3_F2

[0169] make:

[0170] ZB_F2 / ZA_F2=M1_F2

[0171] ZC_F2 / ZA_F2=M2_F2

[0172] in,

[0173] M1_F1 is the ratio of ZB_F1 / ZA_F1, which is dimensionless;

[0174] M2_F1 is the ratio of ZC_F1 / ZA_F1, which is dimensionless;

[0175] but:

[0176] K1_F2*M1_F2+(K1_F2-K2_F2)*M2_F2=K2_F2

[0177] K3_F2*M1_F2-K2_F2*M2_F2=-K3_F2+K2_F2

[0178] ZA_F2+(M1_F2*M2_F2) / (M1_F2+M2_F2)ZA_F2=K1_F2

[0179] Solving the simultaneous equations yields:

[0180] ZA_F2 = 1.923Ω;

[0181] ZB_F2=0.345Ω;

[0182] ZC_F2=0.335Ω.

[0183] (3) Calculate RA, RB, and RC.

[0184] Based on the solved ZA_F1, ZB_F1, ZC_F1, ZA_F2, ZB_F2, and ZC_F2, and using Ohm's law and the inherent parameters of resistance and inductive reactance, the equations are constructed as follows:

[0185] RA^2+(XA_F1)^2=ZA_F1^2

[0186] RA^2+(XA_F2)^2=ZA_F2^2

[0187] Solving the system of equations simultaneously, we get: RA = 1.968Ω.

[0188] RB^2+(XB_F1)^2=ZB_F1^2

[0189] RB^2+(XB_F2)^2=ZB_F2^2

[0190] Solving the system of equations simultaneously, we get: RB = 0.068Ω.

[0191] RC^2+(XC_F1)^2=ZC_F1^2

[0192] RC^2+(XC_F2)^2=ZC_F2^2

[0193] Solving the system of equations simultaneously, we get: RC = 0.060 Ω.

[0194] Determine whether ZA_F1, ZB_F1, ZC_F1, ZA_F2, ZB_F2, ZC_F2, and RA, RB, RC satisfy any of the following conditions:

[0195] (1) The ratio of any two of ZA_F1, ZB_F1, and ZC_F1 is greater than 1.2;

[0196] (2) The ratio of any two of ZA_F2, ZB_F2, and ZC_F2 is greater than 1.2;

[0197] (3) The ratio of any two of RA, RB and RC is greater than 1.2;

[0198] (4) RA, RB and RC, any value of resistance greater than 300mΩ.

[0199] in:

[0200] (1) ZA_F1 / ZB_F1=5.6, ZA_F1 / ZC_F1=8.86, the ratio is greater than 1.2;

[0201] (2) ZA_F2 / ZB_F2 = 5.7, ZA_F2 / ZC_F2 = 5.74, the ratio is greater than 1.2;

[0202] (3) RA / RB = 28.9, RA / RC = 32.8, and the ratio of either of the two is greater than 1.2;

[0203] (4) RA > 300mΩ.

[0204] In conclusion, it is determined that the cross-connected grounding system has a grounding defect.

[0205] The present invention has been disclosed above with reference to preferred embodiments, but it is not intended to limit the present invention. All technical solutions obtained by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the present invention.

Claims

1. A method of testing the connection state of a cable cross-bonding grounding system while energized, characterized by, The device comprises a different frequency excitation source for generating a different frequency alternating signal distinguished from power frequency interference; a current coupler for coupling the different frequency alternating signal generated by the different frequency excitation source into a loop formed by the series connection of an arbitrary phase branch and the parallel connection of the other two phase branches of the cable cross interconnection grounding system; a current test device for measuring the loop current of the loop formed by the series connection of the arbitrary phase branch and the parallel connection of the other two phase branches of the cable cross interconnection grounding system, the current test device comprising a current sensor; an excitation voltage test module for measuring the output voltage of the different frequency excitation source; and an operation module for controlling the different frequency excitation source to generate the different frequency alternating signal and calculating the loop impedance of the loop formed by the series connection of the arbitrary phase branch and the parallel connection of the other two phase branches of the cable cross interconnection grounding system according to the measured loop current and output voltage. The current coupler and the current sensor are sequentially installed on the independent grounding lead joint or terminal or copper bar of the first branch phase, the independent grounding lead joint or terminal or copper bar of the second branch phase, and the independent grounding lead joint or terminal or copper bar of the third branch phase. The loop impedance of the loop formed by the series connection of the first branch and the parallel connection of the second branch and the third branch, the loop impedance of the loop formed by the series connection of the second branch and the parallel connection of the first branch and the third branch, and the loop impedance of the loop formed by the series connection of the third branch and the parallel connection of the first branch and the second branch are respectively tested twice at different frequencies. According to the tested loop impedances, an impedance simultaneous equation is established using Ohm's law to calculate the impedances of the three-phase branches at the two different frequencies. According to the impedances of the three-phase branches at the two different frequencies, a simultaneous equation is established using Ohm's law and the inherent parameter characteristics of resistance and inductive reactance to calculate the resistance of the three-phase branches. According to the impedances of the three-phase branches at the two different frequencies and the resistance of the three-phase branches, it is determined whether the grounding system has a connection defect.

2. The method of claim 1, wherein the method further comprises: The impedance simultaneous equation established according to the tested loop impedances is as follows: ZA_F1+(ZB_F1*ZC_F1) / (ZB_F1+ZC_F1)=K1 _F1 ZB_F1+(ZA_F1*ZC_F1) / (ZA_F1+ZC_F1)=K2_F1 ZC_F1+(ZA_F1*ZB_F1) / (ZA_F1+ZB_F1)=K3_F1 ZA_F2+(ZB_F2*ZC_F2) / (ZB_F2+ZC_F2)=K1 _F2 ZB_F2+(ZA_F2*ZC_F2) / (ZA_F2+ZC_F2)=K2_F2 ZC_F2+(ZA_F2*ZB_F2) / (ZA_F2+ZB_F2)=K3_F2 Wherein, F1, F2 are two different frequencies; K1_F1 is the loop impedance of the first branch plus the second branch and the third branch parallel impedance at frequency F1; K2_F1 is the loop impedance of the second branch plus the first branch and the third branch parallel impedance at frequency F1; K3_F1 is the loop impedance of the third branch plus the first branch and the second branch parallel impedance at frequency F1; K1_F2 is the loop impedance of the first branch plus the second branch and the third branch parallel impedance at frequency F2; K2_F2 is the loop impedance of the second branch plus the first branch and the third branch parallel impedance at frequency F2; K3_F2 is the loop impedance of the third branch plus the first branch and the second branch parallel impedance at frequency F2; ZA_F1 is the impedance of the first branch at frequency F1; ZB_F1 is the impedance of the second branch at frequency F1; ZC_F1 is the impedance of the third branch at frequency F1; ZA_F2 is the impedance of the first branch at frequency F2; ZB_F2 is the impedance of the second branch at frequency F2; ZC_F2 is the impedance of the third branch at frequency F2; Solving the simultaneous equations, the impedance of the first branch at frequency F1, the impedance of the second branch at frequency F1, the impedance of the third branch at frequency F1, the impedance of the first branch at frequency F2, the impedance of the second branch at frequency F2 and the impedance of the third branch at frequency F2 are obtained.

3. The method of claim 1, wherein the method further comprises: The simultaneous equations composed of the impedance of the three-phase branch at two different frequencies are: RA^2+(XA_F1)^2=ZA_F1^2 RA^2+(XA_F2)^2=ZA_F2^2 RB^2+(XB_F1)^2=ZB_F1^2 RB^2+(XB_F2)^2=ZB_F2^2 RC^2+(XC_F1)^2=ZC_F1^2 RC^2+(XC_F2)^2=ZC_F2^2 Wherein, RA is the resistance of the first branch; XA_F1 is the reactance of the first branch at frequency F1; XA_F2 is the reactance of the first branch at frequency F2; RB is the resistance of the second branch, XB_F1 is the reactance of the second branch at frequency F1; XB_F2 is the reactance of the second branch at frequency F2; RC is the resistance of the third branch, XC_F1 is the reactance of the third branch at frequency F1; XC_F2 is the reactance of the third branch at frequency F2; ZA_F1 is the impedance of the first branch at frequency F1; ZB_F1 is the impedance of the second branch at frequency F1; ZC_F1 is the impedance of the third branch at frequency F1; ZA_F2 is the impedance of the first branch at frequency F2; ZB_F2 is the impedance of the second branch at frequency F2; ZC_F2 is the impedance of the third branch at frequency F2; Solving the simultaneous equations, the resistance of the first branch RA, the resistance of the second branch RB and the resistance of the third branch RC are obtained.

4. The method of claim 1, wherein, The method for judging whether the grounding system has a connection defect according to the impedance of the three-phase branch at two different frequencies and the resistance of the three-phase branch, comprising: If the ratio of any two of the three-phase branch impedances at the first frequency is greater than 1.2, or the ratio of any two of the three-phase branch impedances at the second frequency is greater than 1.2, or the ratio of any two of the three-phase branch resistances is greater than 1.2, or the resistance of any of the three-phase branch resistances is greater than 300 mΩ, it is determined that the grounding system has a connection defect.

5. The method of claim 1, wherein, The current testing device further comprises a first filtering module and a current testing module, the first filtering module is connected with the current sensor, and the current testing module is connected with the first filtering module.

6. The method of claim 1, wherein, The current sensor is an openable and closable assembly structure, which allows the tested lead or copper bar to be inserted into the current sensor without disassembling the grounding lead or copper bar.

7. The method of claim 1, wherein, The current coupler is an openable and closable assembly structure, which allows the tested lead or copper bar to be inserted into the current coupler without disassembling the grounding lead or copper bar.

8. The method of claim 1, wherein, The test precision of the current testing device is better than 1A.

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