CN110824383A - Method for calculating short circuit impact cumulative effect of transformer - Google Patents

Abstract

The invention relates to a method for calculating a short-circuit impact cumulative effect of a transformer, which comprises the following steps: (1) collecting main parameters of the transformer to be analyzed and the maximum short-circuit current value I 'bearable on each side'_K(2) Calculating the maximum short-circuit current I allowed by the transformer_k(3) Collecting short circuit impact data (4) of each time in the whole life cycle of the transformer, and calculating the risk degree d caused by the magnitude of the short circuit current of the ith time_{i_n}(5) Calculating the degree of danger d caused by the duration of the short circuit_{i_t}(6) Calculating the risk degree d caused by the short circuit_i(7) And calculating the accumulated risk degree D of short circuit impact. The method can quantitatively calculate the influence of the short-circuit current and the short-circuit duration on the deformation risk of the transformer winding on the basis of acquiring short-circuit impact data of the transformer in the whole life cycle.

Description

Method for calculating short circuit impact cumulative effect of transformer

Technical Field

The invention belongs to the field of analysis of running states of transformers, and particularly relates to a method for calculating short-circuit impact cumulative effects of transformers.

Background

According to the statistical data of the transformer faults of the national grid company in the last 10 years, the insufficient short-circuit resistance is the primary cause of the transformer faults and accounts for 35.7 percent. Through the research on the deformation faults of a large number of transformer windings, the last short-circuit impact causing the deformation of the windings is not very serious, but because the windings are subjected to the short-circuit impact for many times, the tiny deformation of the windings is accumulated continuously, and finally the serious deformation is caused. Therefore, the method can accurately evaluate the state of the transformer subjected to short circuit impact and prevent the winding deformation risk caused by the cumulative effect, and has important practical significance for improving the operation reliability of the transformer.

The existing short circuit impact cumulative effect analysis method is mainly a finite element analysis method, accurate modeling needs to be carried out on a short-circuited transformer, and required parameters are often difficult to obtain accurately, so that the practicability in production practice is poor.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, provides the method for calculating the short circuit impact cumulative effect of the transformer, has simple process, is convenient for comprehensively calculating the transformer in operation in a power grid, and is a practical method.

The technical scheme adopted by the invention for solving the technical problem is as follows:

a method for calculating the short-circuit impact cumulative effect of a transformer comprises the following steps:

(1) collecting main parameters of the transformer to be analyzed and the maximum short-circuit current value I 'bearable on each side'_K

(2) Calculating the maximum short-circuit current I allowed by the transformer_k

(3) Collecting each short circuit impact data in the whole life cycle of the transformer

(4) Calculating the risk degree d caused by the ith short-circuit current_{i_n}

(5) Calculating the degree of danger d caused by the duration of the short circuit_{i_t}

(6) Calculating the risk degree d caused by the short circuit_i

(7) And calculating the accumulated risk degree D of short circuit impact.

Furthermore, it is possible to provide a liquid crystal display device,

wherein, U_HIs the effective value of the maximum operating voltage, Z, of the power supply side of the transformer_SConverting the short-circuit impedance of the power grid system on the power supply side of the transformer into the value Z on the short-circuit side of the transformer_KIs a short circuit impedance value of the short circuit side of the transformer, I'_KThe maximum short-circuit current can be borne by the transformer winding obtained by checking according to the design scheme of the transformer and is provided by a transformer manufacturer.

Furthermore, it is possible to provide a liquid crystal display device,

k_iis a current proportionality coefficient, I_iIs the effective value of the short-circuit current during the short-circuit duration in the ith short-circuit, I_kShort circuit current is allowed for the transformer.

Furthermore, it is possible to provide a liquid crystal display device,

wherein t is_iShort duration, in units of s.

And, d_i＝d_{i_n}+d_{i_t}。

Furthermore, it is possible to provide a liquid crystal display device,

where n is the number of short circuit impacts experienced during the full life cycle of the transformer.

The invention has the advantages and positive effects that:

1. the method can quantitatively calculate the influence of the short-circuit current and the short-circuit duration on the deformation risk of the transformer winding on the basis of acquiring short-circuit impact data of the transformer in the whole life cycle.

2. The calculation method of the invention needs small data quantity, is easy to obtain data, does not need to newly increase detection equipment, and can complete calculation only by using the recorded data of the transformer protection device for the previous short circuit impact.

3. The calculation result of the method can provide scientific and accurate decision basis for the transformer to carry out winding deformation detection, is also beneficial to timely mastering the running state of the transformer, and provides a suggestion for operation and maintenance of the high-risk transformer.

Drawings

FIG. 1 is a flow chart of the method of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following embodiments, which are illustrative only and not limiting, and the scope of the present invention is not limited thereby.

A method for calculating the short-circuit impact cumulative effect of a transformer comprises the following steps:

(1) collecting main parameters of the transformer to be analyzed and the maximum short-circuit current value I 'bearable on each side'_K

I'_KThe maximum short-circuit current can be borne by the transformer winding obtained by checking according to the design scheme of the transformer, and the maximum short-circuit current is generally provided by a transformer manufacturer.

(2) Calculating the maximum short-circuit current I allowed by the transformer_k

For a perfect transformer which does not suffer from short circuit impact, the effective value of the alternating current symmetrical component of the maximum current which flows through the transformer winding and can not cause obvious deformation of the transformer winding within 0.2s is marked as I_k

Wherein, U_HThe effective value of the highest operation voltage of the power supply side (high voltage side) of the transformer is obtained.

Z_SShort-circuit impedance Z 'of power grid system on power supply side of transformer'_SConverted to a value on the short-circuit side (medium voltage side or low voltage side) of the transformer.

Z_KIs the short-circuit impedance value of the short-circuit side of the transformer.

(3) Collecting short circuit impact data of each time in the whole life cycle of the transformer;

(4) calculating the risk degree d caused by the ith short-circuit current_{i_n}

The greater the degree to which the short-circuit current approaches or reaches the permissible short-circuit current, the greater the risk that arises. According to the requirement of GB/T1093, when the short-circuit current reaches 65% or more of the allowable short-circuit current, a winding deformation test is arranged, namely the danger degree brought by the short-circuit current is large.

Defining a short-circuit current proportionality coefficient k_i: the ratio of the actual short-circuit current in the ith short-circuit to the allowable short-circuit current of the transformer.

Wherein I_iEffective value of short-circuit current in short-circuit duration in ith short circuit

Then d_{i_n}Can be calculated by the following formula

(5) Calculating the degree of danger d caused by the duration of the short circuit_{i_t}

The risk of short circuit duration is related to the risk of short circuit current. Generally, it is considered that the statistical number of short circuits increases once every 500ms of the short circuit duration, that is, the risk caused by the magnitude of the short circuit current also increases, and this increment is the risk caused by the short circuit duration.

Then d_{i_t}Can be calculated by the following formula

Wherein t is_iShort duration, in units of s.

(6) Calculating the risk degree d caused by the short circuit_i

Defining the ith short circuit impact risk d of the transformer_i: this secondary short circuit surge creates the possibility of severe deformation of the transformer windings, i.e. the cumulative extent to which the transformer has to be subjected to the necessity of carrying out winding deformation tests.

d_i＝d_{i_n}+d_{i_t}

(7) And calculating the accumulated risk degree D of short circuit impact.

When D reaches or exceeds 1, the possibility of winding deformation of the transformer is high, and a winding deformation test needs to be arranged.

Where n is the number of short circuit impacts experienced during the full life cycle of the transformer.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the inventive concept, and these changes and modifications are all within the scope of the present invention.

Claims (6)

1. A method for calculating the short-circuit impact cumulative effect of a transformer comprises the following steps:

(1) collecting main parameters of the transformer to be analyzed and the maximum short-circuit current value I 'bearable on each side'_K

(2) Calculating the maximum short-circuit current I allowed by the transformer_k

(3) Collecting each short circuit impact data in the whole life cycle of the transformer

(4) Calculating the risk degree d caused by the ith short-circuit current_{i_n}

(5) Calculating the degree of danger d caused by the duration of the short circuit_{i_t}

(6) Calculating the risk degree d caused by the short circuit_i

(7) And calculating the accumulated risk degree D of short circuit impact.

2. The method for calculating the cumulative effect of short circuit impact on the transformer according to claim 1, wherein:

wherein, U_HIs the effective value of the maximum operating voltage, Z, of the power supply side of the transformer_SConverting the short-circuit impedance of the power grid system on the power supply side of the transformer into the value Z on the short-circuit side of the transformer_KIs a short circuit impedance value of the short circuit side of the transformer, I'_KFor checking the obtained variables according to the design of the transformerThe transformer winding can carry the maximum short-circuit current and is supplied by the transformer manufacturer.

3. The method for calculating the cumulative effect of short circuit impact on the transformer according to claim 1, wherein:

k_iis a current proportionality coefficient, I_iIs the effective value of the short-circuit current during the short-circuit duration in the ith short-circuit, I_kShort circuit current is allowed for the transformer.

4. The method for calculating the cumulative effect of short circuit impact on the transformer according to claim 1, wherein:

wherein t is_iShort duration, in units of s.

5. The method for calculating the cumulative effect of short circuit impact on the transformer according to claim 1, wherein:

d_i＝d_{i_n}+d_{i_t}。

6. the method for calculating the cumulative effect of short circuit impact on the transformer according to claim 1, wherein:

where n is the number of short circuit impacts experienced during the full life cycle of the transformer.

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