Method for checking cross correctness of protection range of current transformer for relay protection of tank-type circuit breaker

Abstract

The invention relates to the field of electric power supply systems, and discloses a method for checking protection range crossing correctness of a current transformer for relay protection of a tank-type circuit breaker. In order to solve the problem that a protection'dead zone 'is easily caused in the field installation process of a tank-type circuit breaker, the inspection method provided by the invention utilizes the structural characteristic that a tank-type circuit breaker outgoing line sleeve is used as a primary winding of a mutual inductor; a tank-type circuit breaker tank body (namely an ascending flanged base part sleeved with an annular iron core of a current transformer) is innovatively adopted as a circulation path of test current, and through detection of primary test current and the amplitude and phase of secondary current of a corresponding protection device, index conditions of polarity, transformation ratio, open circuit and the like of the current transformer CT are checked. The method can accurately judge the corresponding relation between the physical installation positions and the electrical positions of the current transformers on the two sides of the tank-type circuit breaker and the protection equipment and between the secondary circuits of the current transformers and the protection equipment, thereby achieving the detection of the crossing correctness of the protection range of the current transformers for relay protection of the tank-type circuit breaker, and eliminating the potential protection dead zone.

Description

Technical Field

[0001] The invention patent relates to the field of electric power supply system, and discloses a method for checking the correctness of the cross protection range of a current transformer used for relay protection of a tank circuit breaker. Background Art

[0002] In the power system, the relay protection device is an automatic device used to respond to the failure or abnormal operation of the electrical equipment in the power system, and works to trip the circuit breaker or send a signal. The relay protection device of each set of electrical equipment has its own pre-defined protection range, that is, the protection zone, which stipulates that any part of the system must be covered by the protection range, and the fault at any point in the system can be discovered and removed. It is required that the protection ranges of any two adjacent power elements must intersect with each other to ensure that any fault occurring at any point is within the protection zone, and no protection "dead zone" is allowed. The current transformer and its secondary cable lead are used to linearly convert the large current signal of the primary power equipment into a small current signal suitable for the relay protection device, and are the first criterion for the action of the relay protection device. The actual installation position of the current transformer and its secondary cable lead determines the most realistic protection range of each relay protection device.

[0003] Tank type circuit breakers have compact structure, good seismic performance, and convenient operation and maintenance. With the development of economy and technology, tank type circuit breakers are widely used in new and expanded power transmission and transformation projects of 220kV and above in the system.

[0004] The tank circuit breaker of this structure comes with an external bushing current transformer (CT for short), which is respectively mounted on the tank body under the bushings on both sides of the circuit breaker. It can completely solve the problem of failure between the conventional porcelain column current transformer and the circuit breaker and no rapid protection action. In theory, there is no "protection dead zone" problem. Considering the problem of transportation, the tank circuit breaker is transported to the site by the manufacturer according to the tank body, CT, bushing, mechanism, etc. for assembly, including each secondary winding of the current transformer. The factory installation personnel assemble it according to the factory design drawings, the installation unit number and installation diagram of each CT, and lay the secondary cable between the current transformer body and the circuit breaker mechanism box according to the installation unit number diagram of the current transformer. Finally, the current transformer is capped and sealed. During the on-site installation process, it is easy to cause a protection "dead zone". The actual installation position of the current transformer determines the protection range of the relay protection device. During the on-site installation of the tank circuit breaker, the most likely situations to cause a protection "dead zone" are: first, the current transformer for relay protection that should be located on the left side of the tank circuit breaker is installed on the right side, while the current transformer for relay protection that should be located on the right side of the tank circuit breaker is installed on the left side; second, the secondary cable of the current loop from the direction of the control protection room should be connected to the secondary tap of the current transformer for relay protection on the left side of the tank circuit breaker, but is actually connected to the secondary tap of the current transformer for relay protection on the right side of the circuit breaker, while the secondary cable of the current loop that should be connected to the secondary tap of the current transformer for relay protection on the right side of the tank circuit breaker is actually connected to the secondary tap of the current transformer for relay protection on the left side of the circuit breaker. The above two situations will result in no rapid protection action to cut off when a fault occurs inside the tank circuit breaker, thus forming a protection "dead zone".

[0005] The current detection method of the current transformer and its secondary circuit of the tank circuit breaker still follows the detection method of the porcelain column current transformer, which is a conventional detection method of injecting current from the primary conductor (referred to as primary current rise) and measuring the secondary current in the control protection room. In this detection method, the primary test current flows through the current transformers on both sides of the tank circuit breaker at the same time, and it is impossible to distinguish which side of the tank body each relay protection current transformer is installed on, resulting in: 1. It is impossible to accurately judge the correspondence between the CT arrangement on the left and right sides of the tank circuit breaker and its secondary cable lead-out wiring and relay protection equipment, and it is impossible to accurately distinguish whether the CT protection range on the left and right sides of the circuit breaker is completely crossed, and it is impossible to find the possible protection "dead zone". 2. It is necessary to install a test line on the primary terminal board at the top of the circuit breaker casing. The wiring before the test and the removal of the test wiring after the test require the cooperation of high-altitude workers and high-altitude working machinery, and the safety risk of high-altitude work is high; for the construction site of the renovation (expansion) project, there is also a risk of inductive electric shock during the connection (removal) of the test line. 3. The test wire is drawn down from high altitude, with a long path and large test loop impedance, which limits the amplitude of the primary test current to a certain extent, and its value usually does not exceed 150A. Since the test current is small, it sometimes interferes with the test personnel's accurate judgment of the current transformer ratio, polarity and the reliability of its secondary circuit. 4. Affected by the position and status of the primary equipment. The tank circuit breaker is required to be in the closed position and the disconnectors on both sides are in the open position. 5. Affected by the on-site construction environment. The primary equipment involved in this detection technology includes circuit breakers, disconnectors and their connecting wires, all of which are used as test loops. They are required to be installed and debugged and have energized conditions. During the test, the above equipment is in a energized state, and no other installation or maintenance work is allowed.

[0006] Although tank circuit breakers are prone to causing protection "dead zones" during on-site installation, the current detection methods for tank circuit breaker current transformers and their secondary circuits still follow the detection methods of porcelain column current transformers, using conventional methods such as loop wiring verification and current injection from the primary conductor (referred to as primary current rise). Conventional detection methods cannot fully detect which side of the tank body the transformer that provides protection current to the relay protection equipment is specifically installed on, which brings great confusion to the on-site relay protection staff in the correct judgment of the crossover of the protection range of the tank circuit breaker current transformer. If this judgment is wrong and the protection "dead zone" is formed, it will bring fatal risks to the safe and stable operation of the power grid. Therefore, in order to completely eliminate the hidden dangers of the crossover of the protection range of the tank circuit breaker, a detection method for the correctness of the crossover of the protection range of the current transformer for the tank circuit breaker relay protection is urgently needed on site. Summary of the invention

[0007] The purpose of the present invention is to solve the deficiencies of the prior art and provide a detection method for quickly, clearly and accurately identifying the installation positions of current transformers on both sides of a tank circuit breaker and the corresponding relationship between their secondary circuits and protection devices, which has the following significant features:

[0008] 1. The new detection method can not only realize all the functions of conventional detection technology, including checking the polarity, transformation ratio and open circuit of the current transformers CT on both sides of the tank circuit breaker, but also accurately identify the installation position of the current transformers on both sides of the tank circuit breaker and the correctness of the corresponding relationship between their secondary circuits and protection devices, that is, the detection of the protection "dead zone".

[0009] 2. The path of the primary test current of the new detection technology no longer relies on the primary conductive circuit such as the circuit breaker, disconnector and its connecting wires.

[0010] (1) The entire test process is not affected by the status and position of the circuit breaker and the isolating switches on both sides;

[0011] (2) The installation and removal of the test wire can be completed on the ground. There is no need for the cooperation of high-altitude workers and high-altitude working machinery, and there is no risk of electric shock from induction electricity. The transfer from conventional "high potential" operation to "ground potential" operation is well realized, and the safety risk of operation is significantly reduced;

[0012] (3) The test wire path is much shorter than that of conventional detection methods, the test loop impedance is significantly reduced, and the test current value can be increased from the conventional 100A to 150A to 300A to 450A, greatly improving the reliability of the entire test;

[0013] (4) During the test and inspection process, the primary equipment such as tank circuit breakers and disconnectors are not energized, which will not affect the installation and maintenance work on the primary equipment, reducing the difficulty of on-site organization and coordination.

[0014] The method can comprehensively judge whether there are loop defects and protection "dead zones" in the AC current loops of the current transformers on both sides of the tank circuit breaker, thereby achieving the purpose of improving the safe and stable operation of the power grid control and protection system.

[0015] The technical solution proposed by the present invention is implemented as follows: a method for checking the correctness of the cross protection range of the current transformer for the relay protection of a tank circuit breaker, comprising step 1, completing the on-site installation of the primary equipment of the tank circuit breaker; step 2, completing the installation of the AC secondary equipment of the tank circuit breaker; step 3, completing the collection of relevant technical parameters of the current transformer; step 4, using the structural characteristics of the outlet bushing of the tank circuit breaker as the primary winding of the transformer, using the tank body of the tank circuit breaker (that is, the raised seat part of the ring core set of the current transformer) as the flow path of the test current, respectively installing the test wires between the flange bolts under the bushings on the left and right sides of the tank circuit breaker and the large tank shell (earth) of the circuit breaker tank body to form a test circuit, simulating the current transformer with load; step 5, completing the primary wiring of the current circuit detection of the current transformer on the bus side of the tank circuit breaker; step 6, completing the tank The current transformer current loop on the line side of the tank type circuit breaker detects the primary wiring; step 7, the current transformer current loop parameter measurement on the bus side, the measured parameters include, the primary applied voltage, current amplitude, phase measurement of the bus side current transformer, and phase determination; the amplitude and phase measurement of the secondary current of the bus side current transformer, and phase determination; step 8, the current transformer current loop parameter measurement on the line side, the measured parameters include, the primary applied voltage, current amplitude, phase measurement of the line side current transformer, and phase determination; the amplitude and phase measurement of the secondary current of the line side current transformer, and phase determination; step 9, establish a new technology test loop impedance model; step 10, analyze the test results according to the on-site inspection quality control standard of the current transformer on the bus side of the tank type circuit breaker; step 11, analyze the test results according to the on-site inspection quality control standard of the current transformer on the line side of the tank type circuit breaker.

[0016] The wiring method described in step 5 is: use three 50mm2 multi-core soft copper wires with a length of about 3 to 4 meters to connect the primary side of the current booster ST to the flange bolts under the bushing on the bus side of the corresponding tank circuit breaker, and install three clamp-type ammeters A2, A3, and A4 for measuring the primary test current on the three-phase test wires. Use the tank body of the tank circuit breaker (that is, the raised seat part of the ring core set of the bus side current transformer) as the path of the test current to form a test circuit; then, according to the transformation ratio of the current transformer on this side, apply a test current of 300A to 400A to simulate the load of the bus side current transformer.

[0017] The wiring method described in step 6 is: use three 50mm2 multi-core soft copper wires with a length of about 3 to 4 meters to connect the primary side of the current booster ST to the flange bolts under the line-side bushing of the corresponding tank circuit breaker, and install three clamp-type ammeters A2, A3, and A4 for measuring the primary test current on the three-phase test wires, respectively. Use the tank body of the tank circuit breaker (that is, the raised seat part of the ring core suit of the line-side current transformer) as the path of the test current to form a test circuit; then, according to the transformation ratio of the current transformer on this side, apply a test current of 300A to 400A to simulate the load of the line-side current transformer.

[0018] The current loop described in step 7 includes an AC circuit breaker QF, an auto-voltage regulator YT, a current booster ST, an ammeter A, a digital multimeter V, and multiple 4mm2 and 50mm2 multi-strand soft copper wires. The parameter measurement method is as follows: a) close the test power supply AC circuit breaker QF, and apply the corresponding primary three-phase positive sequence symmetrical test power supply to the primary side of the busbar side current transformer; b) boost the voltage (current) from zero through the auto-voltage regulator YT, so that the primary side circuit of the raised seat part of the ring core suit of the current transformer on the busbar side of the tank circuit breaker is energized, and detect the primary phase c) According to the design drawings, at the current terminals of each terminal box, control cabinet, and panel cabinet, respectively measure the amplitude and phase of the secondary winding current (including the backup current loop) of each current transformer on the bus side of the tank type circuit breaker, and record them; d) According to the design drawings, at the current terminals of each terminal box, control cabinet, and panel cabinet, respectively measure the amplitude and phase of the secondary winding current (including the backup current loop) of each current transformer on the line side of the tank type circuit breaker, and record them; e) After the test is completed, restore the tested circuit to its original state.

[0019] The current loop described in step 8 includes an AC circuit breaker QF, an auto-voltage regulator YT, a current booster ST, an ammeter A, a digital multimeter V, and multiple 4mm2 and 50mm2 multi-strand soft copper wires. The parameter measurement method is as follows: a) close the test power supply AC circuit breaker QF, and apply the corresponding primary three-phase positive sequence symmetrical test power supply to the primary side of the line-side current transformer; b) boost the voltage (current) from zero through the auto-voltage regulator YT, so that the primary side circuit of the raised seat part of the ring core suit of the current transformer on the line side of the tank circuit breaker is energized, and detect the primary phase c) According to the design drawings, at the current terminals of each terminal box, control cabinet, and panel cabinet, respectively measure the amplitude and phase of the secondary winding current (including the backup current loop) of each current transformer on the line side of the tank type circuit breaker, and record them; d) According to the design drawings, at the current terminals of each terminal box, control cabinet, and panel cabinet, respectively measure the amplitude and phase of the secondary winding current (including the backup current loop) of each current transformer on the bus side of the tank type circuit breaker, and record them; e) After the test is completed, restore the tested circuit to its original state.

[0020] The test loop impedance model described in step 9 is composed of a voltage regulator YT, a current booster ST, a current loop equivalent resistance R, a current loop equivalent inductive reactance ZL, and a multi-core soft copper wire to form a current transformer AC current loop. A 50mm2 high-current multi-core soft copper wire is used to install the test wire at the flange bolt below the tank circuit breaker bushing. The tank body of the tank circuit breaker (i.e., the raised seat part of the current transformer ring core set) is used as the path of the test current to form a test loop. The loop impedance model is a straight line with two sections of 3m in length and a wire radius r0 of 0.004m. The inductance calculation formula used is: L=μ0×l×(ln2l / r0-0.75) / 2π. The calculated impedance of the test loop is 0.003Ω per phase, and the loop test current value can be increased from the conventional 100A to 150A to 300A to 450A.

[0021] The quality control standard for on-site inspection of the current transformer on the bus side of the tank type circuit breaker described in step 10 is: a) Taking the A phase voltage of the 380V AC test power supply as the reference, the amplitudes of the three phases A, B, and C of the test power supply voltage should be equal, and the phase angles should differ by 120° in the positive phase sequence; b) The voltage (current) of the primary circuit of the current transformer on the bus side of the tank type circuit breaker A2, A3, and A4 should be balanced in three phases through the autocoupler voltage regulator YT from zero; c) According to the transformation ratio of each current transformer on the bus side of the tank type circuit breaker, the primary test current value is converted into the secondary calculation current; d) The tank type circuit breaker The measured amplitude and phase of the secondary current of each current transformer on the bus side of the circuit breaker are compared with the converted value of the primary test current. The amplitude and phase relationship of the primary and secondary currents should be consistent with the transformation ratio and polarity terminal lead-out method of each current transformer on the bus side of the tank type circuit breaker, and the amplitude error should not exceed 5%, and the phase error should not exceed ±3°; e) The amplitude and phase of the secondary winding current (including the standby current loop) of each terminal box, control cabinet, and panel cabinet current terminal, and each current transformer on the line side of the tank type circuit breaker should be 0, that is, the secondary value of the current in the bus protection current loop should be 0.

[0022] The quality control standard for on-site inspection of the current transformer on the line side of the tank circuit breaker described in step 11 is: a) Taking the A phase voltage of the 380V AC test power supply as the reference, that is, the amplitudes of the three phases A, B, and C of the test power supply voltage should be equal, and the phase angles should differ by 120° in the positive phase sequence; b) The primary loop current A2, A3, and A4 amplitudes of the current transformer on the line side of the tank circuit breaker should be balanced in three phases through the autocoupler voltage regulator YT zero-start boost (current); c) According to the transformation ratio of each current transformer on the line side of the tank circuit breaker, the primary test current value is converted into the secondary calculation current; d) The tank circuit breaker The measured amplitude and phase of the secondary current of each current transformer on the line side of the circuit breaker are compared with the converted value of the primary test current. The amplitude and phase relationship of the primary and secondary currents should be consistent with the transformation ratio and polarity terminal lead-out method of each current transformer on the line side of the tank type circuit breaker, and the amplitude error should not exceed 5%, and the phase error should not exceed ±3°; e) The amplitude and phase of the secondary winding current (including the standby current loop) of each terminal box, control cabinet, and panel cabinet current terminal, and each current transformer on the bus side of the tank type circuit breaker should be 0, that is, the secondary value of the current in the line protection current loop should be 0.

[0023] The inspection method proposed in the present invention utilizes the structural characteristics of the outlet bushing of the tank circuit breaker as the primary winding of the transformer, and innovatively adopts the tank body of the tank circuit breaker (i.e., the raised seat part of the ring core set of the current transformer) as the flow path of the test current. During the field test, the test wires are installed between the flange bolts under the bushings on the left and right sides of the tank circuit breaker and the large tank shell (earth) of the circuit breaker tank body to simulate the current transformer with load. By detecting the primary test current and the amplitude and phase of the secondary current of the corresponding protection device, not only can the polarity, ratio, open circuit and other indicators of the current transformer CT be checked, but also the physical installation position and electrical position correspondence between the current transformers and their secondary circuits and the protection equipment on both sides of the tank circuit breaker can be accurately judged. Thereby, the detection of the correctness of the cross protection range of the current transformer used for the relay protection of the tank circuit breaker is realized, and the potential protection "dead zone" is eliminated.

[0024] By using the inspection method proposed in the present invention, the path of the primary test current no longer depends on the primary conductive circuits such as circuit breakers, disconnectors and their connecting wires. (1) The entire test process is not affected by the status and position of the circuit breakers and the disconnectors on both sides thereof; (2) The installation and removal of the test wires can be completed on the ground. There is no need for the cooperation of high-altitude workers and high-altitude working machinery, there is no risk of induced electric shock, and the operational safety risk is significantly reduced; (3) The test wire path is greatly shortened compared to conventional detection methods, the impedance value of the test circuit is significantly reduced, and the test current value can be increased from the conventional 100A to 150A to 300A to 450A, greatly improving the reliability of the entire test; (4) During the test and detection process, primary equipment such as tank circuit breakers and disconnectors are not energized, which will not affect the installation and maintenance work on the primary equipment, reducing the difficulty of on-site organization and coordination. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the tank circuit breaker structure;

[0026] Figure 2 Schematic diagram of conventional primary current rise of tank type circuit breaker current transformer;

[0027] Figure 3 Schematic diagram of conventional primary current rise of tank type circuit breaker current transformer;

[0028] Figure 4 Schematic diagram of the bushing CT structure on one side of the tank circuit breaker;

[0029] Figure 5 Flow chart for on-site inspection of current transformer current loop of tank circuit breaker.

[0030] Figure 6 Current transformer AC current loop test model.

[0031] Figure 7 Schematic diagram of 500kV tank type circuit breaker.

[0032] Figure 8 Prior Art Loop Impedance Model.

[0033] Fig. 9 New Technology Loop Impedance Model.

[0034] Fig.10 Schematic diagram of three-phase power circuit wiring.

[0035] Fig.11 Schematic diagram of AC current circuit detection of current transformer on busbar side of tank type circuit breaker.

[0036] Fig.12 Schematic diagram of AC current loop detection of current transformer on the line side of tank type circuit breaker.

[0037] Figure 1 In the circuit breaker, CT is an external bushing current transformer. Figure 6 In the figure, YT is the voltage regulator, ST is the current booster, R is the equivalent resistance of the current loop, and ZL is the equivalent inductive reactance of the current loop. Fig.10 In the figure, QF is an AC circuit breaker with overcurrent protection, and its capacity should meet the test requirements. YT is a three-phase auto-voltage regulator, V is a digital multimeter, ST is a current booster, A1 is an ammeter, A2, A3, A4 are clamp-type ammeters, DETAILED DESCRIPTION

[0038] according to Figure 5 The on-site inspection flow chart of the current transformer current loop of the tank circuit breaker is carried out.

[0039] 1. Collection of technical parameters of current transformers for tank-type circuit breakers. Relevant technical parameters are collected based on the on-site manufacturer's information, product nameplates and design drawings of tank-type circuit breakers, including the transformation ratio, polarity, accurate level of each CT winding and its installation arrangement position, purpose and circuit number of the current transformer, and a relevant parameter table is formed.

[0040] Technical Parameters

[0041]

[0042] 2. Determine the test model. Figure 2 The circuit wiring diagram of the existing field test is shown, taking the 500kV tank circuit breaker commonly seen on site as an example. Figure 7 In the test, a 50mm2 high-current multi-core soft copper wire is used to connect the terminal block connectors on the top of the incoming bushing and the outgoing bushing to form a test circuit. According to the primary current path and line layout of the on-site test, the primary conductor path and the area enclosed by the test are required. Figure 8 The prior art loop impedance model is designed to be a trapezoid, see Figure 8 (a) is equivalent to a rectangle with a width of 2m and a length of (8.162+6.902)m, such as Figure 8 (b) The entire test loop is expected to be 35m. The test loop can be equivalent to a single-turn rectangle with a length of 15m, a width of 2m, and a conductor radius r0 of 0.004m. According to the inductance calculation formula of a single-turn rectangle,

[0043]

[0044] Where:

[0045] L is the loop inductance (H); a is the length of the rectangle; b is the width of the rectangle; r0 is the radius of the circular wire; μ0 is the magnetic permeability of vacuum, μ0 = 4π10 -7(H / m), and: r0 << a, r0 << b. Substituting a = 14.254 m, b = 2 m, and r0 = 0.004 m, we get: L = 40.9 mH; calculating ZL = 12.84 Ω.

[0046] As the capacity of the power system continues to expand, the transformation ratio of the current transformers used in the new power system also expands accordingly. Current transformers with a transformation ratio of 2000 - 4000 / 1 are usually adopted. To prevent signal interference and achieve complete and accurate detection of the AC current loop from the loop to the device, it is required that the test current value applied to the primary side of the current transformer also increases.

[0047] The impedance model of the new technology test loop is shown in Figure 6 the test model of the AC current loop of the current transformer, Fig. 9 the impedance model of the new technology loop

[0048] According to Figure 6 the test model, without increasing the capacity of the test power supply YT, we can increase the test current by reducing the short - circuit impedance ZL of the test loop to meet the requirements for the accuracy of the test results. The loop of the primary test current of the new detection technology no longer depends on the primary conductive loops such as circuit breakers, disconnectors, and their connecting wires. Instead, test wires are installed on the body of the tank - type circuit breaker itself (see Fig.10 、 Fig.11 、 Fig.12 ) to carry out the test.

[0049] Taking the common 500 kV tank - type circuit breaker on - site as an example, see Figure 7 . The circuit wiring of the on - site test is shown in Fig.10 、 Fig.11 、 Fig.12 . During the test, 50 mm2 large - current multi - core flexible copper wires are used to install test wires at the flange bolts below the bushing of the tank - type circuit breaker. The body of the tank - type circuit breaker (i.e., the riser seat part where the toroidal core of the current transformer is sleeved) is used as the path of the test current to form the test loop. According to the on - site test primary current path and line layout, the path and the area enclosed by the required primary conductors, the impedance model of the existing technology loop is designed as a straight line, see Fig.10 (a), which is equivalent to two straight lines each 3 m long, as shown in Fig.10 (b). The entire test loop is expected to be 6 m. Moreover, the test loop is simplified to two straight lines each 3 m long with a wire radius r0 of 0.004 m. According to the inductance calculation formula for a single wire:

[0050] L = μ0×l×(ln2l / r0 - 0.75) / 2π

[0051] In the formula: L is the loop inductance (H); μ0 is the vacuum permeability, μ0 = 4π10-7 (H / m); l is the wire length (m); r0 is the radius of the circular wire, r0 = 0.004m, substituting into the equation: L = 0.009mH; ZL = wL = 0.003Ω.

[0052] From the above analysis, it can be seen that the length of the test wire of the new technology is shortened from 15 meters per phase in the conventional method to 3 meters per phase; the path of the test current loop is shortened from 35 meters per phase in the conventional method to 6 meters per phase; the impedance of the test loop is reduced from 12.84Ω per phase in the conventional method to 0.003Ω per phase. The impedance value of the test loop is significantly reduced, and the test current value can be increased from the conventional 100A to 150A to 300A to 450A, greatly improving the accuracy of the entire test.

[0053] 3. Main test equipment and tools that need to be prepared

[0054]

[0055] 4. Test power supply preparation

[0056] Meet the capacity requirements of the test equipment and retain 1.2 times the capacity margin.

[0057] 5. Inspection and control of on-site conditions for AC current circuit testing of tank circuit breakers

[0058] First, the tank circuit breaker body has been installed in place, and its ancillary equipment, including operating mechanism, current transformer, bushing, etc., has been installed. The grounding parts of the metal shell of the equipment have been reliably grounded, which meets the relevant requirements of the electrical installation engineering construction and acceptance specifications. Secondly, the tank circuit breaker and its ancillary equipment are all subject to electrical testing in accordance with the test methods specified in GB / T 16927.1, GB / T 16927.2, DL / T 474.1~5 and related equipment standards.

[0059] In addition to meeting the requirements of GB 50150, the electrical test results must also meet the requirements of the layout, polarity and accurate level of the transformer secondary winding, the lead taps and their markings must be clear, fixed and non-detachable, and consistent with the product nameplate diagram and design requirements.

[0060] 6. Installation and debugging of the secondary circuit of the current transformer is completed

[0061] The terminal box, mechanism box, panel cabinet and secondary cable terminal block in the AC secondary circuit of the tank circuit breaker current transformer are all constructed according to the design drawings, in compliance with the relevant requirements of the electrical installation engineering construction and acceptance specifications, and the wiring is correct. The secondary winding taps and transformation ratios of each current transformer of the tank circuit breaker are consistent with the requirements of the dispatch setting notification.

[0062] 7. Test wiring at the inspection site

[0063] On-site test of the secondary current circuit of the current transformer of the tank circuit breaker, where the circuit wiring of the power supply part is as follows Fig.10 During the on-site wiring process, except for the test conductor on the primary side of the test current transformer, which uses 50mm2 multi-strand soft copper wire with an insulating sheath, other test wiring uses 4mm2 multi-strand soft copper wire.

[0064] 8. Complete the test according to the steps in the instruction manual.

Claims

1. A method for checking the correctness of the cross protection range of a current transformer for a tank circuit breaker relay protection, comprising the following steps: Step 1, complete the on-site installation of the primary equipment of the tank circuit breaker; Step 2, complete the installation of AC secondary equipment of tank circuit breaker; Step 3, completing the collection of technical parameters related to the current transformer, is characterized in that it also includes the following steps: Step 4: Using the structural characteristics of the outlet bushing of the tank circuit breaker as the primary winding of the transformer, the tank body of the tank circuit breaker (i.e., the elevated seat part of the ring core set of the current transformer) is used as the flow path of the test current, and the test wires are installed between the flange bolts under the bushings on the left and right sides of the tank circuit breaker and the large tank shell of the circuit breaker tank body (ground) to form a test circuit to simulate the current transformer with load; Step 5, completing the primary wiring of the current transformer current loop detection on the bus side of the tank type circuit breaker; Step 6, completing the primary wiring of the current transformer current loop detection on the line side of the tank type circuit breaker; Step 7, measuring the current loop parameters of the bus-side current transformer, the measured parameters include the primary applied voltage and current amplitude and phase measurement of the bus-side current transformer, and phasing; the amplitude and phase measurement of the secondary current of the bus-side current transformer, and phasing; Step 8: Measuring the current loop parameters of the current transformer on the line side, the measured parameters include the amplitude and phase measurement of the primary applied voltage and current of the current transformer on the line side, and phasing; the amplitude and phase measurement of the secondary current of the current transformer on the line side, and phasing; Step 9, establishing a new technology test loop impedance model; Step 10, analyzing the test results according to the on-site inspection quality control standard for the current transformer on the bus side of the tank type circuit breaker; Step 11, analyzing the test results according to the on-site inspection quality control standard for the line-side current transformer of the tank circuit breaker.

2. A method for checking correctness of cross protection range of current transformer for tank type circuit breaker relay protection according to claim 1, characterized in that: The wiring method described in step 5 is: use three 50mm2 multi-core soft copper wires with a length of about 3 to 4 meters to connect the primary side of the current booster ST to the flange bolts below the bushing on the bus side of the corresponding tank circuit breaker, and install three clamp-type ammeters A2, A3, and A4 for measuring the primary test current on the three-phase test wires, respectively. Use the tank body of the tank circuit breaker (that is, the raised seat part of the ring core set of the bus side current transformer) as the path of the test current to form a test circuit; then, according to the transformation ratio of the current transformer on this side, apply a test current of 300A to 400A to simulate the load of the bus side current transformer.

3. A method for checking correctness of cross protection range of current transformer for tank type circuit breaker relay protection according to claim 1, characterized in that: The wiring method described in step 6 is: use three 50mm2 multi-core soft copper wires with a length of about 3 to 4 meters to connect the primary side of the current booster ST to the flange bolts under the line-side bushing of the corresponding tank circuit breaker, and install three clamp-type ammeters A2, A3, and A4 for measuring the primary test current on the three-phase test wires, respectively. Use the tank body of the tank circuit breaker (that is, the raised seat part of the ring core suit of the line-side current transformer) as the path of the test current to form a test circuit; then, according to the transformation ratio of the current transformer on this side, apply a test current of 300A to 400A to simulate the load of the line-side current transformer.

4. A method for checking correctness of cross protection range of current transformer for tank type circuit breaker relay protection according to claim 1, characterized in that: The current loop described in step 7 includes an AC circuit breaker QF, an auto-voltage regulator YT, a current booster ST, an ammeter A, a digital multimeter V, and multiple 4mm2 and 50mm2 multi-strand soft copper wires. The parameter measurement method is as follows: a) close the test power supply AC circuit breaker QF, and apply the corresponding primary three-phase positive sequence symmetrical test power supply to the primary side of the busbar side current transformer; b) boost the voltage (current) from zero through the auto-voltage regulator YT, so that the primary side circuit of the raised seat part of the ring core suit of the current transformer on the busbar side of the tank circuit breaker is energized, and detect the primary phase c) According to the design drawings, at the current terminals of each terminal box, control cabinet, and panel cabinet, respectively measure the amplitude and phase of the secondary winding current (including the backup current loop) of each current transformer on the bus side of the tank type circuit breaker, and record them; d) According to the design drawings, at the current terminals of each terminal box, control cabinet, and panel cabinet, respectively measure the amplitude and phase of the secondary winding current (including the backup current loop) of each current transformer on the line side of the tank type circuit breaker, and record them; e) After the test is completed, restore the tested circuit to its original state.

5. The method for checking correctness of cross protection range of current transformer for tank type circuit breaker relay protection according to claim 1, characterized in that: The current loop described in step 8 includes an AC circuit breaker QF, an auto-voltage regulator YT, a current booster ST, an ammeter A, a digital multimeter V, and multiple 4mm2 and 50mm2 multi-strand soft copper wires. The parameter measurement method is as follows: a) close the test power supply AC circuit breaker QF, and apply the corresponding primary three-phase positive sequence symmetrical test power supply to the primary side of the line-side current transformer; b) boost the voltage (current) from zero through the auto-voltage regulator YT, so that the primary side circuit of the raised seat part of the ring core suit of the current transformer on the line side of the tank circuit breaker is energized, and detect the primary phase c) According to the design drawings, at the current terminals of each terminal box, control cabinet, and panel cabinet, respectively measure the amplitude and phase of the secondary winding current (including the backup current loop) of each current transformer on the line side of the tank type circuit breaker, and record them; d) According to the design drawings, at the current terminals of each terminal box, control cabinet, and panel cabinet, respectively measure the amplitude and phase of the secondary winding current (including the backup current loop) of each current transformer on the bus side of the tank type circuit breaker, and record them; e) After the test is completed, restore the tested circuit to its original state.

6. A method for checking correctness of cross protection range of current transformer for tank type circuit breaker relay protection according to claim 1, characterized in that: The test loop impedance model described in step 9 is composed of a voltage regulator YT, a current booster ST, a current loop equivalent resistance R, a current loop equivalent inductive reactance ZL, and a multi-core soft copper wire to form a current transformer AC current loop. A 50mm2 high-current multi-core soft copper wire is used to install the test wire at the flange bolt below the tank circuit breaker bushing. The tank body of the tank circuit breaker (i.e., the raised seat part of the current transformer ring core set) is used as the path of the test current to form a test loop. The loop impedance model is a straight line with two sections of 3m in length and a wire radius r0 of 0.004m. The inductance calculation formula used is: L=μ0×l×(ln2l / r0-0.75) / 2π. The calculated impedance of the test loop is 0.003Ω per phase, and the loop test current value can be increased from the conventional 100A to 150A to 300A to 450A.

7. A method for checking correctness of cross protection range of current transformer for tank type circuit breaker relay protection according to claim 1, characterized in that: The quality control standard for on-site inspection of the current transformer on the bus side of the tank type circuit breaker described in step 10 is: a) Taking the A phase voltage of the 380V AC test power supply as the reference, the amplitudes of the three phases A, B, and C of the test power supply voltage should be equal, and the phase angles should differ by 120° in the positive phase sequence; b) The voltage (current) of the primary circuit of the current transformer on the bus side of the tank type circuit breaker A2, A3, and A4 should be balanced in three phases through the autocoupler voltage regulator YT from zero; c) According to the transformation ratio of each current transformer on the bus side of the tank type circuit breaker, the primary test current value is converted into the secondary calculation current; d) The tank type circuit breaker The measured amplitude and phase of the secondary current of each current transformer on the bus side of the circuit breaker are compared with the converted value of the primary test current. The amplitude and phase relationship of the primary and secondary currents should be consistent with the transformation ratio and polarity terminal lead-out method of each current transformer on the bus side of the tank type circuit breaker, and the amplitude error should not exceed ±5%, and the phase error should not exceed ±3°; e) The current terminals of each terminal box, control cabinet, and panel cabinet, and the amplitude and phase of the secondary winding current of each current transformer on the line side of the tank type circuit breaker (including the standby current loop) should be 0, that is, the secondary value of the current in the bus protection current loop should be 0.

8. A method for checking correctness of cross protection range of current transformer for tank type circuit breaker relay protection according to claim 1, characterized in that: The quality control standard for on-site inspection of the current transformer on the line side of the tank type circuit breaker described in step 11 is: a) Taking the A phase voltage of the 380V AC test power supply as the reference, that is, the amplitudes of the three phases A, B, and C of the test power supply voltage should be equal, and the phase angles should differ by 120° in the positive phase sequence; b) The primary loop current A2, A3, and A4 amplitudes of the current transformer on the line side of the tank type circuit breaker should be balanced in three phases through the autocoupler voltage regulator YT from zero; c) According to the transformation ratio of each current transformer on the line side of the tank type circuit breaker, the primary test current value is converted into the secondary calculation current; d) The tank type circuit breaker The measured amplitude and phase of the secondary current of each current transformer on the line side of the circuit breaker are compared with the converted value of the primary test current. The amplitude and phase relationship of the primary and secondary currents should be consistent with the transformation ratio and polarity terminal lead-out method of each current transformer on the line side of the tank type circuit breaker, and the amplitude error should not exceed ±5%, and the phase error should not exceed ±3°; e) The current terminals of each terminal box, control cabinet, and panel cabinet, and the amplitude and phase of the secondary winding current of each current transformer on the bus side of the tank type circuit breaker (including the standby current loop) should all be 0, that is, the secondary value of the current in the line protection current loop should be 0.

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