A method for setting an arc line in an arc fault simulation test of a current transformer

Abstract

This invention discloses a method for setting up an arc-starting wire in an arc fault simulation test of a current transformer, including determining the arc-starting wire for the arc fault simulation test and placing the arc-starting wire at the head of an inverted oil-immersed current transformer; the method for determining the arc-starting wire for the arc fault simulation test is based on the requirements for the arc-starting performance index; when the arc-starting wire determined by the arc-starting performance index cannot meet the simulation test requirements, the material, cross-sectional area, and length of the arc-starting wire are adjusted until the simulation test requirements are fully met.

Description

Technical Field

[0001] This invention relates to a method for setting up an arc-leading wire in a current transformer arc fault simulation test. Background Technology

[0002] Statistics show that in the past five years, eight faults and 39 serious and critical defects have occurred in inverted current transformers at voltage levels of 220kV and above in the Jiangsu power grid. The highest failure rate was observed at the head of the inverted oil-immersed current transformer. Explosions are common in accidents caused by inverted oil-immersed current transformers. These accidents not only reduce the transmitted power but also damage other nearby equipment in the substation, posing a significant threat to the safety and reliability of the power grid. The root cause of the explosion is an internal arc fault leading to the rapid expansion of the oil-gas mixture, which in turn causes the oil conservator to rupture due to excessive pressure. Due to the complex internal structure of the transformer and the rapid development of arc faults, the oil-gas conversion process and its distribution, as well as the diffusion law of the oil-gas mixture, are currently unclear. Therefore, research on the internal arc faults of inverted oil-immersed current transformers is particularly important.

[0003] Current domestic and international research has completed preliminary work on the heat flow distribution, partial discharge, and structural defects of oil-immersed current transformers under normal conditions, mostly focusing on inverted oil-immersed current transformers. However, the discharge process, heat flow distribution, and pressure changes after a main insulation breakdown fault (often forming an arc) remain unclear. This is mainly due to the complexity of fault formation factors, the difficulty in identification, and the rapid development of the fault. Therefore, there is an urgent need to conduct arc fault simulation tests on inverted oil-immersed current transformers to study and analyze the above issues. Among these, the selection and layout of the arc-leading wire is a crucial aspect of arc fault simulation tests. Summary of the Invention

[0004] The purpose of this invention is to propose a method for setting up the arc-starting wire in the arc fault simulation test of a current transformer. By determining the arc-starting performance index requirements of the arc-starting wire, the cross-sectional area of ​​the arc-starting wire is determined, and a suitable position is selected to fix the arc-starting wire, thus providing the necessary experimental conditions for the arc fault simulation test of an inverted oil-immersed current transformer.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for setting up an arc-starting wire in an arc fault simulation test of a current transformer includes determining the arc-starting wire for the arc fault simulation test and laying the arc-starting wire at the head of an inverted oil-immersed current transformer; wherein, the determination of the arc-starting wire for the arc fault simulation test is based on the requirements for the arc-starting performance index, and the requirements for the arc-starting performance index are determined by Formula 1.

[0007] First, determine the material, cross-sectional area, and length of the arc-starting wire to meet the requirements of the simulation test. Then, determine whether the arc-starting wire meets the requirements of the simulation test based on the arc-starting performance index. If the arc-starting wire determined by the arc-starting performance index cannot meet the requirements of the simulation test, adjust the material, cross-sectional area, and length of the arc-starting wire until it fully meets the requirements of the simulation test.

[0008]

[0009] in:

[0010] Δ represents the arc-starting performance index;

[0011] k is the arc-starting correction coefficient;

[0012] U(V) is the voltage applied to both ends of the arc-leading wire;

[0013] I(A) is the current flowing through the arc-leading wire;

[0014] T(s) is the duration of the current in the arc-starting wire;

[0015] S(mm 2 () represents the cross-sectional area of ​​the arc-leading wire after the outer insulation layer has been removed;

[0016] L (mm) is the length of the arc;

[0017] σ(S / m) is the conductivity of the arc-leading wire.

[0018] A further step in the solution is: the arrangement of the arc-leading wire at the head of the inverted oil-immersed current transformer is:

[0019] Step 1: First, crimp the connecting terminals to both ends of the selected arc-lead wire;

[0020] Step 2: Drill holes in the outer shell of the oil conservator at the head of the current transformer to expose the insulation outside the secondary winding shield.

[0021] Step 3: Make internal openings in the exposed insulation until the secondary winding shield is exposed;

[0022] Step 4: Drill threaded holes in the exposed secondary winding shield, and then use copper screws to screw into the threaded holes to position and fix the connecting terminal at one end of the arc-leading wire to the secondary winding shield; the connecting terminal at the other end of the arc-leading wire is connected to a sealing block. The sealing block seals the external opening from the outside of the head oil tank housing by welding, thus forming a connection between the other end of the arc-leading wire and the head oil tank housing.

[0023] A further provision of the scheme is that the diameter of the external opening is at least three times the diameter of the arc-leading wire, and the diameter of the internal opening is at least twice the diameter of the arc-leading wire.

[0024] The scheme is further defined as follows: when the arc-starting correction coefficient k = 10.05:

[0025] When 0.95≤Δ≤1.20, the selected arc conductor meets the requirements of the simulation test;

[0026] If Δ>1.20 or Δ<0.95, the selected arc-starting line does not meet the requirements of the simulation test. Adjust the material, cross-sectional area, and length of the arc-starting line until it fully meets the requirements of the simulation test.

[0027] The beneficial effects of this invention are: by determining the cross-sectional area of ​​the arc-initiating wire according to the arc-initiating performance index requirements, and selecting a suitable position to fix the arc-initiating wire, the necessary experimental conditions are provided for the arc fault simulation test of the inverted oil-immersed current transformer.

[0028] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the layout of the leading-arc line. Detailed Implementation

[0030] A method for setting up an arc-starting wire in an arc fault simulation test of a current transformer includes determining the arc-starting wire for the arc fault simulation test and laying the arc-starting wire at the head of an inverted oil-immersed current transformer; wherein, the determination of the arc-starting wire for the arc fault simulation test is based on the requirements for the arc-starting performance index, and the requirements for the arc-starting performance index are determined by Formula 1.

[0031] First, determine the material, cross-sectional area, and length of the arc-starting wire to meet the requirements of the simulation test. Then, determine whether the arc-starting wire meets the requirements of the simulation test based on the arc-starting performance index. If the arc-starting wire determined by the arc-starting performance index cannot meet the requirements of the simulation test, adjust the material, cross-sectional area, and length of the arc-starting wire until it fully meets the requirements of the simulation test.

[0032]

[0033] in:

[0034] Δ represents the arc-starting performance index;

[0035] k is the arc-starting correction coefficient;

[0036] U(V) is the voltage applied to both ends of the arc-leading wire;

[0037] I(A) is the current flowing through the arc-leading wire;

[0038] T(s) is the duration of the current in the arc-starting wire;

[0039] S(mm 2() represents the cross-sectional area of ​​the arc-leading wire after the outer insulation layer has been removed;

[0040] L (mm) is the length of the arc;

[0041] σ(S / m) is the conductivity of the arc-leading wire.

[0042] Since the test was conducted on the head of the inverted oil-immersed current transformer, where the failure rate is highest, the arc-leading wire needs to be installed at the head. For example... Figure 1 As shown, the arrangement of the arc-leading wire 1 at the head of the inverted oil-immersed current transformer is as follows:

[0043] Step 1: First, crimp the connecting terminals to both ends of the selected arc lead wire 1;

[0044] Step 2: Drill a hole 201 at the triangular area of ​​the oil conservator shell 2 at the head of the current transformer to expose the insulation 4 outside the secondary winding shield 3.

[0045] Step 3: Drill holes 401 inside the exposed insulation 4 until the secondary winding shield 3 is exposed.

[0046] Step 4: Drill threaded holes in the exposed secondary winding shield 3, and then use copper screws to screw into the threaded holes to position and fix the connecting terminal at one end of the arc-leading wire to the secondary winding shield 3; the connecting terminal at the other end of the arc-leading wire 1 is connected to a sealing block 5. The sealing block 5 seals the external opening from the outside of the head oil tank housing 2 by welding, and forms a connection between the other end of the arc-leading wire and the head oil tank housing 2.

[0047] Wherein: the diameter of the external opening is at least 3 times the diameter of the arc-leading wire, and the diameter of the internal opening is at least 2 times the diameter of the arc-leading wire.

[0048] The arc-starting correction factor k is a correction factor given when other physical quantities are calculated in the current unit to avoid the difference in dimensions between the left and right sides. k is equal to 10.05 in numerical terms and is used to offset other units in terms of units, so as to calculate the dimensionless arc-starting performance index.

[0049] Therefore: when the arc-starting correction coefficient k = 10.05:

[0050] When 0.95≤Δ≤1.20, the selected arc conductor meets the requirements of the simulation test;

[0051] If Δ>1.20 or Δ<0.95, the selected arc-starting line does not meet the requirements of the simulation test. Adjust the material, cross-sectional area, and length of the arc-starting line until it fully meets the requirements of the simulation test.

[0052] The above-described embodiment of the method for setting up the arc-leading wire in the arc fault simulation test of the current transformer determines the cross-sectional area of ​​the arc-leading wire by requiring the arc-leading performance index, and selects a suitable position to fix the arc-leading wire, thus providing the necessary experimental conditions for the arc fault simulation test of the inverted oil-immersed current transformer.

Claims

1. A method for setting up an arc-leading wire in an arc fault simulation test of a current transformer, comprising determining the arc-leading wire for the arc fault simulation test and placing the arc-leading wire at the head of an inverted oil-immersed current transformer; characterized in that, The arc-starting wire used in the arc fault simulation test is determined based on the requirements for the arc-starting performance index, which is determined by Formula 1. First, determine the material, cross-sectional area, and length of the arc-starting wire to meet the requirements of the simulation test. Then, determine whether the arc-starting wire meets the requirements of the simulation test based on the arc-starting performance index. If the arc-starting wire determined by the arc-starting performance index cannot meet the requirements of the simulation test, adjust the material, cross-sectional area, and length of the arc-starting wire until it fully meets the requirements of the simulation test. Formula 1 in: Δ represents the arc-starting performance index; k is the arc-starting correction coefficient; U is the voltage applied to both ends of the arc-starting wire, in V; I is the current flowing through the arc-leading wire, in A; T is the duration of the current in the arc-starting wire, in seconds; S is the cross-sectional area of ​​the arc-leading wire after the outer insulation layer has been removed, in mm. 2 ; L is the length of the arc conductor, in mm; σ is the conductivity of the arc-leading wire, in S / m.

2. The method for setting the arc-leading line according to claim 1, characterized in that, The arrangement of the arc-leading wire at the head of the inverted oil-immersed current transformer is as follows: Step 1: First, crimp the connecting terminals to both ends of the selected arc-lead wire; Step 2: Drill holes in the outer shell of the oil conservator at the head of the current transformer to expose the insulation outside the secondary winding shield. Step 3: Make internal openings in the exposed insulation until the secondary winding shield is exposed; Step 4: Drill threaded holes in the exposed secondary winding shield, and then use copper screws to screw into the threaded holes to position and fix the connecting terminal at one end of the arc-leading wire to the secondary winding shield; the connecting terminal at the other end of the arc-leading wire is connected to a sealing block. The sealing block seals the external opening from the outside of the head oil tank by welding, thus forming a connection between the other end of the arc-leading wire and the head oil tank.

3. The method for setting the arc-leading line according to claim 2, characterized in that, The diameter of the external opening is at least three times the diameter of the arc-leading wire, and the diameter of the internal opening is at least twice the diameter of the arc-leading wire.

4. The method for setting the arc-leading line according to claim 1, characterized in that, When the arc-starting correction coefficient k = 10.05: When 0.95≤Δ≤1.20, the selected arc conductor meets the requirements of the simulation test; If Δ>1.20 or Δ<0.95, the selected arc-starting line does not meet the requirements of the simulation test. Adjust the material, cross-sectional area, and length of the arc-starting line until it fully meets the requirements of the simulation test.

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