An Optimization and Improvement Method for the Out-of-Step Protection Blocking Element of the Generator-Transformer Unit

Abstract

The present invention discloses an optimized improvement method for the out-of-step protection blocking element of a generator-transformer unit. The present invention calculates the out-of-step protection tripping allowable current by setting the CT position for connecting the current of the blocking element in the out-of-step protection blocking element of the generator-transformer unit, setting the out-of-step protection action outlet switch object, and based on the actual current connected to the blocking element and the breaking capacity of the circuit breaker actually tripped by the out-of-step protection, so as to ensure the reliability of the action of the out-of-step protection element of the generator-transformer unit and guarantee the safety of the circuit breaker and the power grid.

Description

Technical Field

[0001] The present invention belongs to the technical field of relay protection of power systems, and particularly relates to an optimization and improvement method for a loss-of-synchronism protection locking element of a generator-transformer unit. Background Art

[0002] The loss-of-synchronism protection is applicable to large generator-transformer units. When the system undergoes an unstable oscillation, i.e., loss of synchronism, which endangers the safety of the unit or the system, it acts on signals or trips. When the loss-of-synchronism protection trips the circuit breaker, if the potential difference δ between the two sides of the system is 180° at the time of tripping, on the one hand, the cut-off current is large at this time, greater than the three-phase short-circuit current, and on the other hand, the voltage between the contacts of the circuit breaker rises instantaneously when the current is cut off. At this time, the current-breaking capacity of the circuit breaker decreases. When the cut-off current is greater than the breaking capacity of the circuit breaker, there is a risk of damage to the circuit breaker during tripping. Therefore, the tripping allowable current of the loss-of-synchronism protection is used as the locking condition for the action outlet of the loss-of-synchronism protection.

[0003] According to the regulation DL / T684-2012 "Guide for Relay Protection Setting Calculation of Large Generator Transformers", the tripping allowable current can be calculated as I off =K rel I brk where K rel is the reliability coefficient, and I brk corresponds to the allowable breaking current of the circuit breaker corresponding to the tripping of the loss-of-synchronism protection outlet. This breaking current can be taken from the CT on the high-voltage side of the main transformer or from the CT at the generator terminal. At present, only the tripping allowable current setting module is given in the loss-of-synchronism protection module of the generator-transformer unit protection device in China, and no fixed-value items related to the CT position for connecting the allowable breaking current of the circuit breaker are given, nor are the fixed-value setting items for the switch object of the loss-of-synchronism protection action outlet given. This will result in the tripping allowable current of the loss-of-synchronism protection not being calculated according to the actual access current and the actual breaking capacity of the corresponding circuit breaker, which will surely cause the loss-of-synchronism protection of the generator-transformer unit to refuse to operate or malfunction, threatening the safety of the circuit breaker itself and the power grid. Summary of the Invention

[0004] The purpose of the present invention is to propose an optimization and improvement method for a loss-of-synchronism protection locking element of a generator-transformer unit in view of the mis-setting caused by unclear setting conditions in the fixed-value setting of the existing loss-of-synchronism protection locking element of a generator-transformer unit.

[0005] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0006] An optimization and improvement method for a loss-of-synchronism protection locking element of a generator-transformer unit, including setting the CT position required for the locking element in the loss-of-synchronism protection locking element of the generator-transformer unit, and setting the switch object of the loss-of-synchronism protection action outlet.

[0007] A further improvement of the present invention is that the loss-of-synchronism protection locking element of the generator-transformer unit refers to a circuit breaker breaking capacity locking element.

[0008] A further improvement of the present invention lies in that a CT position for leading out the blocking element is set in the out-of-step protection blocking element of the generator-transformer unit, and the CT position for leading out the blocking element is set, including:

[0009] M1: CT on the high-voltage side of the main transformer; M2: CT at the generator terminal.

[0010] A further improvement of the present invention lies in that an out-of-step protection action outlet switch object is set in the out-of-step protection blocking element of the generator-transformer unit, and the out-of-step protection action outlet switch object includes:

[0011] N1: Switch on the high-voltage side of the main transformer; N2: Generator outlet circuit breaker GCB.

[0012] A further improvement of the present invention lies in that a CT position required for leading out the blocking element is set in the out-of-step protection blocking element of the generator-transformer unit, and an out-of-step protection action outlet switch object is set, and they are respectively set through protection control words, and are used to calculate the out-of-step protection tripping allowable current I off .

[0013] A further improvement of the present invention lies in that a CT position required for leading out the blocking element is set in the out-of-step protection blocking element of the generator-transformer unit, and an out-of-step protection action outlet switch object is set;

[0014] When the current of the blocking element is led from the CT on the high-voltage side of the main transformer, i.e., M1, and the out-of-step protection action outlet is the switch on the high-voltage side of the main transformer, i.e., N1, then the out-of-step protection tripping allowable current is calculated by the following formula:

[0015] I off = K rel I brk

[0016] Wherein, K rel is the reliability coefficient, and I brk corresponds to the allowable interrupting current of the circuit breaker on the high-voltage side of the main transformer.

[0017] A further improvement of the present invention lies in that a CT position required for leading out the blocking element is set in the out-of-step protection blocking element of the generator-transformer unit, and an out-of-step protection action outlet switch object is set;

[0018] When the current of the blocking element is led from the CT on the high-voltage side of the main transformer, i.e., M1, and the out-of-step protection action outlet is the GCB at the generator terminal, i.e., N2, then the out-of-step protection tripping allowable current is calculated by the following formula:

[0019]

[0020] Wherein, K rel is the reliability coefficient, I brk.GCB corresponds to the allowable interrupting current of the GCB at the generator outlet, and U1 and U2 respectively correspond to the rated voltages of the high and low voltage sides of the main transformer.

[0021] A further improvement of the present invention lies in setting the position of the CT for connection required by the blocking element in the out-of-step protection blocking element of the generator-transformer unit, and setting the object of the out-of-step protection action outlet switch.

[0022] When the current of the blocking element is connected from the CT at the machine terminal, i.e., M2, and the out-of-step protection action is output to the switch on the high-voltage side of the main transformer, i.e., N1, the following formula is used to calculate the out-of-step protection tripping allowable current:

[0023]

[0024] Where K rel is the reliability coefficient, I brk corresponds to the allowable interrupting current of the circuit breaker on the high-voltage side of the main transformer, and U1 and U2 respectively correspond to the rated voltages of the high- and low-voltage sides of the main transformer.

[0025] A further improvement of the present invention lies in setting the position of the CT for connection required by the blocking element in the out-of-step protection blocking element of the generator-transformer unit, and setting the object of the out-of-step protection action outlet switch.

[0026] When the current of the blocking element is connected from the CT at the machine terminal, i.e., M2, and the out-of-step protection action is output to the GCB at the generator terminal, i.e., N2, the following formula is used to calculate the out-of-step protection tripping allowable current:

[0027] I off = K rel I brk.GCB

[0028] Where K rel is the reliability coefficient, I brk.GCB corresponds to the allowable interrupting current of the GCB at the generator outlet.

[0029] A further improvement of the present invention lies in that the calculation of the out-of-step protection tripping allowable current is completed through internal calculation of the relay protection device or by relay protection setting calculation personnel.

[0030] The present invention has at least the following beneficial technical effects:

[0031] By setting the position of the CT for connection of the current of the blocking element in the out-of-step protection blocking element of the generator-transformer unit, setting the object of the out-of-step protection action outlet switch, and calculating the out-of-step protection tripping allowable current according to the actual current connected to the blocking element and the interrupting capacity of the circuit breaker actually tripped by the out-of-step protection, the reliability of the out-of-step protection element of the generator-transformer unit is ensured, and the safety of the circuit breaker and the power grid is guaranteed. Description of the Drawings

[0032] Figure 1 This is a typical out-of-step protection logic diagram listed for the present invention.

[0033] Figure 2 This is the logic diagram of the out-of-step protection interruption capacity locking element of the present invention.

[0034] Symbol explanations are as follows:

[0035] & represents the logical "AND" relationship, that is, when all input conditions are fully met, the output is valid; ○ represents the logical "NOT" relationship, that is, the input condition is inverted.

[0036] M1 represents the CT on the high-voltage side of the main transformer; M2 represents the CT at the generator terminal. N1 represents the out-of-step protection tripping the switch on the high-voltage side of the main transformer; N2 represents the out-of-step protection tripping the generator outlet circuit breaker GCB. M1, M2, N1, and N2 can be defined as control words 1 and 0. Specific implementation mode

[0037] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. Hereinafter, the present invention will be described in detail with reference to the drawings and in combination with the embodiments.

[0038] As Figure 1 shown, an optimized improvement method for the out-of-step protection locking element of a generator-transformer unit provided by the present invention includes the following steps:

[0039] 1) Set the CT position required for the locking element in the out-of-step protection locking element of the generator-transformer unit, and set the out-of-step protection action outlet switch object.

[0040] 2) The CT position where the locking element current is connected includes the locking element current being connected from the CT on the high-voltage side of the main transformer (M1) and the CT at the generator terminal (M2); the out-of-step protection action outlet switch object includes the out-of-step protection outlet acting to trip the switch on the high-voltage side of the main transformer (N1) and the out-of-step protection outlet acting to trip the generator outlet GCB (N2). M1, M2, N1, and N2 can be defined as control words 1 and 0.

[0041] 3) Set the CT position (M1 or M2) where the out-of-step protection locking element current is connected and set the out-of-step protection outlet action switch (N1 or N2) through the control word. Calculate the out-of-step protection locking element tripping allowable current value according to the setting. The calculation is divided into the following several methods:

[0042] When the locking element current is connected from the CT on the high-voltage side of the main transformer (M1) and the out-of-step protection action outlet is the switch on the high-voltage side of the main transformer (N1), the out-of-step protection tripping allowable current is calculated using the following formula:

[0043] I off = K rel I brk

[0044] Wherein, K rel is the reliability coefficient, and I brk corresponds to the allowable interrupting current of the circuit breaker on the high-voltage side of the main transformer.

[0045] When the locked element current is taken from the CT (M1) on the high-voltage side of the main transformer and the out-of-step protection action exits at the generator terminal GCB (N2), the allowable current for out-of-step protection tripping is calculated using the following formula:

[0046]

[0047] Wherein, K rel is the reliability coefficient, and I brk.GCB corresponds to the allowable interrupting current of the GCB at the generator outlet, and U1 and U2 respectively correspond to the rated voltages of the high- and low-voltage sides of the main transformer.

[0048] When the locked element current is taken from the CT (M2) at the machine terminal and the out-of-step protection action exits at the switch on the high-voltage side of the main transformer (N1), the allowable current for out-of-step protection tripping is calculated using the following formula:

[0049]

[0050] Wherein, K rel is the reliability coefficient, and I brk corresponds to the allowable interrupting current of the circuit breaker on the high-voltage side of the main transformer, and U1 and U2 respectively correspond to the rated voltages of the high- and low-voltage sides of the main transformer.

[0051] When the locked element current is taken from the CT (M2) at the machine terminal and the out-of-step protection action exits at the generator terminal GCB (N2), the allowable current for out-of-step protection tripping is calculated using the following formula:

[0052] I off = K rel I brk.GCB

[0053] Wherein, K rel is the reliability coefficient, and I brk.GCB corresponds to the allowable interrupting current of the GCB at the generator outlet.

[0054] The calculation of the allowable current for out-of-step protection tripping mentioned above can be completed through internal calculation of the relay protection device. Users only need to input relevant system parameters and circuit breaker interrupting current parameters in the setting list, or it can also be calculated by relay protection setting calculation personnel.

[0055] Adopt the optimized improvement method of the out-of-step protection blocking element of the present invention. By setting the CT position for leading the current of the blocking element and setting the outlet switch object for the out-of-step protection action, ensure the accuracy of the calculated value of the tripping allowable current of the out-of-step protection blocking element, guarantee the reliability of the out-of-step protection action, and ensure the safety of the circuit breaker itself and the safe operation of the power grid.

[0056] Although the present invention has been described in detail with general descriptions and specific embodiments above, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. An optimized improvement method for the out-of-step protection blocking element of the generator-transformer unit, characterized in that, Including setting the CT position required for the blocking element in the out-of-step protection blocking element of the generator-transformer unit, and setting the out-of-step protection action outlet switch object; Setting the CT position for the blocking element in the out-of-step protection blocking element of the generator-transformer unit and setting the CT position for the blocking element includes: M1: CT on the high-voltage side of the main transformer; M2: CT at the generator terminal; Setting the out-of-step protection action outlet switch object in the out-of-step protection blocking element of the generator-transformer unit, and the out-of-step protection action outlet switch object includes: N1: Switch on the high-voltage side of the main transformer; N2: Generator circuit breaker GCB; When the current of the blocking element is taken from the CT on the high-voltage side of the main transformer, i.e., M1, and the out-of-step protection action is at the switch on the high-voltage side of the main transformer, i.e., N1, then the out-of-step protection tripping allowable current is calculated using the following formula: When the current of the blocking element is taken from the CT on the high-voltage side of the main transformer, i.e., M1, and the out-of-step protection action is at the generator terminal GCB, i.e., N2, then the out-of-step protection tripping allowable current is calculated using the following formula: When the current of the blocking element is taken from the CT at the generator terminal, i.e., M2, and the out-of-step protection action is at the switch on the high-voltage side of the main transformer, i.e., N1, then the out-of-step protection tripping allowable current is calculated using the following formula: When the current of the blocking element is taken from the CT at the generator terminal, i.e., M2, and the out-of-step protection action is at the generator terminal GCB, i.e., N2, then the out-of-step protection tripping allowable current is calculated using the following formula: Among them, is the reliability coefficient, corresponding to the allowable interrupting current of the circuit breaker on the high-voltage side of the main transformer, corresponding to the allowable interrupting current of the generator outlet GCB, and correspond to the rated voltages on the high- and low-voltage sides of the main transformer respectively.

2. The optimization and improvement method of an out-of-step protection blocking element for a generator-transformer unit according to claim 1, characterized in that, The out-of-step protection blocking element of the generator-transformer unit refers to the circuit breaker breaking capacity blocking element.

3. An optimized improvement method for the out-of-step protection blocking element of a generator-transformer unit according to claim 1, characterized in that Set the CT position required for the blocking element in the out-of-step protection blocking element of the generator-transformer unit, set the out-of-step protection action outlet switch object, and set them respectively through the protection control word, which is used to calculate the out-of-step protection tripping allowable current .

4. The optimization and improvement method of an out-of-step protection blocking element for a generator-transformer unit according to claim 1, characterized in that The calculation of the out-of-step protection tripping allowable current is completed through internal calculation of the relay protection device or by relay protection setting calculation personnel.

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