CN102222880B - Method for identifying inrush exciting current of transformer and avoiding differential protection maloperation of transformer - Google Patents

Abstract

The invention provides a method for identifying inrush exciting current of a transformer and avoiding differential protection maloperation of the transformer. A method for judging whether preset conditions of various input and output side switches of a locked transformer are accorded at present is that: the preset conditions of various input and output side switches are not accorded if any of the following conditions occurs, wherein the first condition is that: after protection is started, current on any side of the transformer is not reduced; the second condition is that: after protection is started, current on any two sides of the transformer is greater than a preset threshold value; furthermore, other two conditions are present, namely the third condition is that the maximum current on any side of the transformer is greater than the preset maximum inrush exciting current value in preset time after protection is started, and the fourth condition is that the current value on any side of the transformer is greater than a preset current value at a corresponding moment on any time point in the preset time after protection is started. By the method, inrush exciting current conditions of the transformer can be more accurately judged; therefore, the transformer is accurately controlled.

Description

Identification transformer excitation flow is also avoided the method for transformer differential protection malfunction

technical field:

The present invention relates to tranformer protection field, relate in particular to and a kind ofly identify transformer excitation flow and prevent the method that it causes transformer differential protection malfunction.

background technology:

When air-drop transformer, can produce larger magnetizing inrush current, may cause transformer differential protection malfunction, current transformer differential protection is all to utilize the feature of magnetizing inrush current waveform to identify magnetizing inrush current, the feature of magnetizing inrush current waveform as: waveform has interval angle, waveform symmetry degree is different from normal current, or the harmonic wave amount of other frequencies (as: contains second harmonic higher than normal value, quintuple harmonics etc.), current processing means are that judgement draws it is that after magnetizing inrush current, tranformer protection takes the methods such as locking in short-term to prevent transformer differential protection malfunction.

The groundwork flow process of tranformer protection at present, as shown in Figure 1, concrete step is as described below:

1), first, transformer self-inspection, and judge that self-detection result whether within the scope of normal condition, as self-detection result is all normally, enters step 2); As self-detection result exists abnormal condition, enter step 8);

2), transformer by set point drop into protection, then, enter step 3);

3), transformer both sides electric current, information of voltage are gathered, enter afterwards step 4);

4), the electric current, the information of voltage that obtain according to step 3) judge the current default tranformer protection entry condition that whether meets, if meet, enters step 5), if do not meet, returns to step 3);

5), the electric current, the information of voltage that obtain according to step 3) judge the current default transformer fault condition that whether meets, if meet, enters step 6), if do not meet, returns to step 3);

6), the electric current, the information of voltage that obtain according to step 3) judge currently whether meet that default locking transformer is respectively inputted, output side switch condition, if meet, returns to step 3), if do not meet, enters step 7);

7), carry out the actions such as tripping operation, alarm;

8), improper self-detection result information is carried out to alarm; Afterwards, enter step 9);

9), judged whether slot signal, if having, return to step 1), if do not have, return to step 8).

But; at present to the 6th) the determination methods more complicated of identification magnetizing inrush current in step " whether meet default locking transformer is respectively inputted, the condition of output side switch "; amount of calculation is large; efficiency is lower; easily there is erroneous judgement; thereby there is transformer differential protection incorrect operation, if can judge more exactly the magnetizing inrush current situation of transformer, can avoid more accurately transformer differential protection malfunction.

summary of the invention:

The object of this invention is to provide a kind of method of identifying transformer excitation flow and avoiding transformer differential protection malfunction, judge more exactly the magnetizing inrush current situation of transformer, thereby avoid the differential protection malfunction of transformer.

Identify transformer excitation flow and avoid the method for transformer differential protection malfunction, concrete step is as described below:

1), first, transformer self-inspection, and judge that self-detection result whether within the scope of normal condition, as self-detection result is all normally, enters step 2); As self-detection result exists abnormal condition, enter step 8);

2), transformer by set point drop into protection, then, enter step 3);

3), transformer both sides electric current, information of voltage are gathered, enter afterwards step 4);

4), the electric current, the information of voltage that obtain according to step 3) judge the current default tranformer protection entry condition that whether meets, if meet, enters step 5), if do not meet, returns to step 3);

5), the electric current, the information of voltage that obtain according to step 3) judge the current default transformer fault condition that whether meets, if meet, enters step 6), if do not meet, returns to step 3);

6) electric current, the information of voltage, obtaining according to step 3) judges that current whether locking transformer is respectively inputted, the condition of output side switch, if meet, locking transformer is respectively inputted, the condition of output side switch, return to step 3), if do not meet, locking transformer is respectively inputted, the condition of output side switch, enters step 7);

7), carry out the actions such as tripping operation, alarm;

8), improper self-detection result information is carried out to alarm; Afterwards, enter step 9);

9), judged whether slot signal, if having, return to step 1), if do not have, return to step 8);

Wherein: in step 6), the concrete grammar of " judge current whether meet that default locking transformer is respectively inputted, the condition of output side switch " is: following arbitrary situation occurs, be judged as and do not meet that default locking transformer is respectively inputted, the condition of output side switch:

Situation one: after protection starts, the each side current value of transformer does not all reduce phenomenon;

Situation two: when protection starts, transformation has a high regard for both sides electric current to be greater than the default stream threshold value that has.

Described identification transformer excitation flow is also avoided the method for transformer differential protection malfunction; wherein: in described step 6) in the concrete grammar of " judge current whether meet that default locking transformer is respectively inputted, the condition of output side switch ": be judged as and do not meet that default locking transformer is respectively inputted, the condition of output side switch, also comprise following arbitrary situation:

Situation three), protection start after in the stipulated time, transformer either side lowest high-current value is greater than predefined maximum magnetizing inrush current current value;

Situation four), protection start after in arbitrary moment point in the stipulated time, transformer either side current value is greater than the current value in predefined corresponding moment.

The present invention will reach following technique effect after adopting technique scheme:

Identification transformer excitation flow of the present invention is also avoided the method for transformer differential protection malfunction, that after utilizing transformer air-drop, the rapid feature decaying of magnetizing inrush current is identified magnetizing inrush current, and the short circuit current that transformer fault causes is unattenuated, even if drop in failure transformer, though there is magnetizing inrush current in electric current, but after this current attenuation, still have very large fault current, the inventive method does not change the groundwork flow process of current tranformer protection, the locking Rule of judgment that has been only unique design, can judge whether more exactly to meet barring condition, thereby can avoid transformer differential protection malfunction in identification transformer excitation flow.

brief description of the drawings:

Fig. 1 is the groundwork flow chart of tranformer protection in prior art;

Fig. 2 judges in identification transformer excitation flow of the present invention the method for avoiding transformer differential protection malfunction currently whether to meet that default locking transformer is respectively inputted, the concrete grammar schematic diagram of output side switch condition.

embodiment:

Identification transformer excitation flow of the present invention is also avoided the method for transformer differential protection malfunction, and concrete step is as described below:

1), first, transformer self-inspection, and judge that self-detection result whether within the scope of normal condition, as self-detection result is all normally, enters step 2); As self-detection result exists abnormal condition, enter step 8);

2), transformer by set point drop into protection, then, enter step 3);

3), transformer both sides electric current, information of voltage are gathered, enter afterwards step 4);

4), the electric current, the information of voltage that obtain according to step 3) judge the current default tranformer protection entry condition that whether meets, if meet, enters step 5), if do not meet, returns to step 3);

5), the electric current, the information of voltage that obtain according to step 3) judge the current default transformer fault condition that whether meets, if meet, enters step 6), if do not meet, returns to step 3);

6) electric current, the information of voltage, obtaining according to step 3) judges that current whether locking transformer is respectively inputted, the condition of output side switch, if meet, locking transformer is respectively inputted, the condition of output side switch, return to step 3), if do not meet, locking transformer is respectively inputted, the condition of output side switch, enters step 7);

7), carry out the actions such as tripping operation, alarm;

8), improper self-detection result information is carried out to alarm; Afterwards, enter step 9);

9), judged whether slot signal, if having, return to step 1), if do not have, return to step 8);

Wherein: in step 6), the concrete grammar of " judge current whether meet that default locking transformer is respectively inputted, the condition of output side switch " is: following arbitrary situation occurs, be judged as and do not meet that default locking transformer is respectively inputted, the condition of output side switch:

Situation one: after protection starts, the each side current value of transformer does not all reduce phenomenon;

Situation two: when protection starts, transformation has a high regard for both sides electric current to be greater than the default stream threshold value that has;

After situation three, protection start, in the stipulated time, transformer either side lowest high-current value is greater than predefined maximum magnetizing inrush current current value;

In arbitrary moment point after situation four, protection start in the stipulated time, transformer either side current value is greater than the current value in predefined corresponding moment.

Wherein, situation three and situation four are applicable to drop the situation of not latch-up protection in the time of failure transformer.

Though magnetizing inrush current is without Mathematical Modeling statement accurately, it observes certain law jointly, that is:

1, magnetizing inrush current only exists within the shorter a period of time of dropping into after transformer; So situation three, four of situations are effective at the appointed time;

2, magnetizing inrush current can be not infinitely great, moment, maximum was no more than the several times of transformer rated current, concrete multiple and transformer capacity, the factors such as structure are relevant, but be confirmable to a concrete transformer, so can being set, a maximum magnetizing inrush current current value (maximum magnetizing inrush current current value is set, need to consider certain surplus, namely this maximum magnetizing inrush current current value is larger, concrete value oneself is determined before use by user, mode by fixed value adjusting enters programming), and short circuit current may be larger than this maximum magnetizing inrush current current value, exceeding maximum magnetizing inrush current current value just thinks and is not magnetizing inrush current, do not meet barring condition.

3, after producing, magnetizing inrush current can within the utmost point short time, reach peak value, decay rapidly subsequently, the rate of decay slows down gradually, so can be arranged on the magnetizing inrush current value that in this process, each time point may be maximum according to this rule, and short circuit can not decay, the current value that exceedes the predefined corresponding moment (arranges the current value in corresponding moment, consider certain surplus, namely larger, concrete value oneself is determined before use by user, mode by fixed value adjusting enters programming), just think and be not magnetizing inrush current, do not meet barring condition.

4, while dropping failure transformer, existing magnetizing inrush current also has fault current, transformer drops into after-current also may there is first big after small phenomenon, but dropping into current maxima, transformer may be greater than maximum magnetizing inrush current current value, its attenuation amplitude is also much smaller than magnetizing inrush current, and in program, facilities three and situation four, can identify this situation, not locking, tripping failure transformer.

Claims (1)

1. identify transformer excitation flow and avoid the method for transformer differential protection malfunction, concrete step is as described below:

1), first, transformer self-inspection, and judge that self-detection result whether within the scope of normal condition, as self-detection result is all normally, enters step 2); As self-detection result exists abnormal condition, enter step 8);

2), transformer by set point drop into protection, then, enter step 3);

3), transformer both sides electric current, information of voltage are gathered, enter afterwards step 4);

4), the electric current, the information of voltage that obtain according to step 3) judge the current default tranformer protection entry condition that whether meets, if meet, enters step 5), if do not meet, returns to step 3);

5), the electric current, the information of voltage that obtain according to step 3) judge the current default transformer fault condition that whether meets, if meet, enters step 6), if do not meet, returns to step 3);

6) electric current, the information of voltage, obtaining according to step 3) judges that current whether locking transformer is respectively inputted, the condition of output side switch, if meet, locking transformer is respectively inputted, the condition of output side switch, return to step 3), if do not meet, locking transformer is respectively inputted, the condition of output side switch, enters step 7);

7), carry out the actions such as tripping operation, alarm;

8), improper self-detection result information is carried out to alarm; Afterwards, enter step 9);

9), judged whether slot signal, if having, return to step 1), if do not have, return to step 8);

In step 6), the concrete grammar of " judge current whether meet that default locking transformer is respectively inputted, the condition of output side switch " is: following arbitrary situation occurs, be judged as and do not meet that default locking transformer is respectively inputted, the condition of output side switch:

Situation one: after protection starts, the each side current value of transformer does not all reduce phenomenon;

Situation two: when protection starts, transformation has a high regard for both sides electric current to be greater than the default stream threshold value that has;

In described step 6), " judge currently whether meet that default locking transformer is respectively inputted, the bar of output side switch

Part " concrete grammar in: be judged as and do not meet that default locking transformer is respectively inputted, the condition of output side switch, also comprise following arbitrary situation:

Situation three), protection start after in the stipulated time, transformer either side lowest high-current value is greater than predefined maximum magnetizing inrush current current value;

Situation four), protection start after in arbitrary moment point in the stipulated time, transformer either side current value is greater than the current value in predefined corresponding moment.