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Calculation method of back two-pole current parameter under asymmetric fault condition

A technique for asymmetric faults and current parameters, used in the measurement of electricity, measurement of electrical variables, circuit breaker testing, etc.

Active Publication Date: 2017-03-22
XIAN HIGH VOLTAGE APP RES INST CO LTD +1
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] Aiming at the problems existing in the prior art, the present invention provides a method for calculating the current parameters of the back-opening two poles under asymmetrical fault conditions, which solves the problem that the half-wave peak value of the back-opening two-pole current cannot be obtained through calculation The half-wave duration Δt, the percentage of the DC component at the current zero point, and the slope di / dt of the current zero-crossing point

Method used

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  • Calculation method of back two-pole current parameter under asymmetric fault condition
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  • Calculation method of back two-pole current parameter under asymmetric fault condition

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Embodiment 1

[0055] The present invention is a method for calculating the current parameters of the back-opening poles under asymmetrical fault conditions, which includes the following steps for neutral point non-effectively grounded systems:

[0056] 1) When a three-phase short-circuit fault occurs, the current flowing through the circuit breaker is:

[0057]

[0058] Among them, α is the closing phase angle, is the power factor angle, τ is the inherent time constant, I m is the peak value of the AC component of the short circuit current. Decompose short-circuit current into AC components and DC component operate independently.

[0059] 2) t 0When the phase A short-circuit current crosses zero, the arc is extinguished first, and then the two poles are connected in series to form a single-phase circuit. The voltage and current direction of each point are as follows: figure 1 As shown, the relationship between the voltage and current vectors of each point is obtained by using th...

Embodiment 2

[0066] The present invention is a method for calculating the current parameters of the back-opening poles under asymmetrical fault conditions, aimed at the neutral point effective grounding system, comprising the following steps:

[0067] 1) After a three-phase short-circuit fault occurs, t 0 When the phase A short-circuit current crosses zero at the moment, the arc is extinguished first. Using the symmetrical component method, when the coefficient of the first pole opening is equal to 1.3, that is, X 1 =X 2 , X 0 =3X 1 , can get t≥t 0 When , the expression of the AC component of the B and C two-phase current is:

[0068]

[0069] 2) t 1 The short-circuit current of phase C of the second open stage at the moment is extinguished when it crosses zero. Using the symmetrical component method, it can be obtained that t≥t 1 When , the expression of the AC component of the late opening current is:

[0070]

[0071] 3) After superimposing the DC component, the current exp...

Embodiment 3

[0078] The present invention is a method for calculating the current parameters of the rear-opening poles under asymmetrical fault conditions. For the effective grounding system of the neutral point, for the case where the coefficient of the first-opening pole is equal to 1.2, X 1 =X 2 , X 0 =2X 1 Substitute into the operation, and the rest of the process is the same as in Embodiment 2.

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Abstract

The present invention provides a calculation method of a back-open two-pole current parameter under an asymmetric fault condition, and a problem that the back-open two-pole current parameter can not be obtained through calculation is obtained. The method comprises the steps of (1) obtaining each phase current which passes a circuit breaker before first-open phase crossing zero time t0 when a three-phase short circuit fault happens, (2) carrying out independent vector operation of an AC component and a DC component of the back-open two-pole current after the first-open phase crossing zero time t0, and obtaining corresponding expressions. (3) stacking the estimated AC component and the DC component, and obtaining the back-open two-pole current parameter. According to the method, the obtained back-open two-pole current expressions are suitable for a neutral point effective grounding system and a neutral point non-effective grounding system, after the vector calculation of the AC component and the DC component, the AC component in the vector diagram obtained by a symmetrical component method and the DC component limited by a boundary condition can be stacked, and near-open pole and back-open pole current calculation formulas can be obtained.

Description

technical field [0001] The invention relates to the technical field of short-circuit test of a high-voltage AC circuit breaker, in particular to a method for calculating the current parameters of the back-opening two poles under asymmetrical fault conditions. Background technique [0002] my country's power system is divided into neutral point effective grounding system and neutral point non-effective grounding system. When a three-phase short-circuit fault occurs, the short-circuit current consists of two parts, the AC component and the DC component. Test method T100a is a type test used to assess the severity of the breaking condition of the circuit breaker determined by the moment of contact separation. [0003] In the direct test, as long as the first pole-opening current parameter (the last current half-wave peak The duration of the last half wave Δt, the percentage of the DC component at the current zero point, the slope of the current zero crossing point (di / dt) an...

Claims

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Application Information

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IPC IPC(8): G01R31/327
CPCG01R31/3271
Inventor 董玮刘浩军高享想胡勋
Owner XIAN HIGH VOLTAGE APP RES INST CO LTD
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