WO2018023909A1 - 基于电压量积分判别变压器铁芯饱和的方法 - Google Patents
基于电压量积分判别变压器铁芯饱和的方法 Download PDFInfo
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- WO2018023909A1 WO2018023909A1 PCT/CN2016/108791 CN2016108791W WO2018023909A1 WO 2018023909 A1 WO2018023909 A1 WO 2018023909A1 CN 2016108791 W CN2016108791 W CN 2016108791W WO 2018023909 A1 WO2018023909 A1 WO 2018023909A1
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
- H02H7/045—Differential protection of transformers
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
- H02H7/045—Differential protection of transformers
- H02H7/0455—Differential protection of transformers taking into account saturation of current transformers
Definitions
- the invention relates to a method for discriminating transformer core saturation based on voltage quantity integral, and belongs to the technical field of transformers.
- the magnetizing inrush current When the voltage is restored after the transformer is turned on or the fault is removed, the magnetizing inrush current will occur. When the airdrop or fault is removed, the voltage amplitude will increase. When the operating transformer is in the system fault or some operations (such as non-synchronous closing), the voltage amplitude is generally reduced. And the voltage phase angle changes greatly, that is to say, when the voltage phase angle changes greatly, the voltage amplitude decreases, and the magnetizing inrush current may also occur. This is not noticed when analyzing the mechanism of the magnetizing inrush current.
- Non-synchronous closing refers to whether the power system at both ends of the circuit breaker to be closed is closed at the same time.
- the asynchronous closing may be caused by automatic parallel device failure or staff misoperation.
- the object of the present invention is to provide a method for discriminating the saturation of a transformer core based on voltage quantity integration, which can identify the magnetizing inrush current caused by airdrop or fault cutoff voltage recovery, and the induced and inrush current generated by an adjacent transformer caused by a transformer air charge. It is also possible to identify the magnetizing inrush current caused by the running transformer during a fault or some operation, such as a non-synchronous closing.
- the technical solution adopted by the present invention is: a method for judging the saturation of a transformer core based on voltage amount integration, and for a voltage of each phase of a transformer side, when the voltage variation exceeds a set threshold When the value is considered, the transformer state is considered to be abrupt;
- S e represents the reference value of the standardization
- S 0 is the saturation threshold of the transformer core.
- ⁇ u(t) u(t)-u(t-T)
- u(t) represents the instantaneous value of the voltage at time t
- T represents the voltage period
- ⁇ is the integral variable
- S 0 ranges from 1.15 to 1.4.
- the change of voltage phase may also cause the transformer core to saturate and generate magnetizing inrush current.
- excitation may also occur.
- the proposed discriminant method starts from the root cause of the magnetizing inrush current, that is, the core flux saturation caused by the voltage change of the transformer terminal, which can distinguish the magnetizing inrush current and the inrush current caused by the airdrop or fault cutoff voltage recovery, and can also identify the running transformer. Magnetizing inrush current caused by system failure or some operations (such as asynchronous closing);
- the discriminating speed is fast, which is conducive to improving the speed of the transformer differential protection.
- a method for judging the saturation of a transformer core based on voltage integral which starts from the root cause of the magnetizing inrush current, that is, the saturation of the flux caused by the change of the voltage at the transformer terminal (including the amplitude and the phase angle), and calculates the voltage from the sudden change of the voltage state.
- the absolute value of the absolute value of the half-wave integral S 1 (t) is used to indicate the peak value of the steady-state periodic component of the flux linkage after the sudden change of the state; the absolute value of the integral of the half-cycle voltage change amount starting from the moment of the sudden change of voltage S 2 (t ) to represent the aperiodic component of the flux linkage after the state mutation, and the sum S(t) of the two represents the maximum value that the flux linkage can reach after the state mutation. If S(t) is greater than the threshold value S 0 , the core is judged to be saturated.
- the method can identify the magnetizing inrush current caused by the airdrop or fault cut-off voltage recovery, and can also identify the magnetizing inrush current caused by the operating transformer in the event of system failure or some operations (such as asynchronous closing).
- phase voltage before the transformer state changes is The steady-state voltage after the transformer state changes is
- U m is the voltage peak
- ⁇ is the voltage angular frequency
- ⁇ is the voltage phase angle difference before and after the state change
- ⁇ m U m / ⁇
- C 1 is an integral constant, indicating remanence.
- C 2 is an arbitrary constant.
- ⁇ 2 (t) includes two parts, a steady state component and a direct current component. Since it is difficult to directly obtain the maximum value of the flux linkage after the state change, the voltage amount is equivalently substituted.
- ⁇ is the integral variable.
- the steady-state component of ⁇ 2 (t) That is, it can be expressed by the half-wave integral of the voltage amount.
- the lower limit of integration 0 represents the state of sudden change of the state
- the DC component of ⁇ 2 (t) That is, it can be expressed by the first half wave integral of the voltage change amount.
- ⁇ 2 (t) can be obtained indirectly by the amount of voltage, and the transformer core saturation identification scheme is designed accordingly: in order to calculate the maximum value that the flux linkage can reach after the sudden change of the operating state of the transformer, the voltage state is suddenly changed. After that, the half-wave integral S 1 (t) of the absolute value of the voltage is calculated, which is used to indicate the peak value of the steady-state periodic component of the flux linkage after the sudden change of the state, and the absolute value of the integral of the half-cycle voltage change amount at the time of the sudden change of the voltage.
- S 2 (t) represents the aperiodic component of the flux linkage after the state mutation, and the sum S(t) represents the maximum value that the flux linkage can reach after the state mutation. If S(t) is greater than the threshold value S 0 , the core is judged to be saturated.
- the relevant formula is as follows:
- u(t) represents the instantaneous value of the voltage at time t
- S e represents the reference value obtained by the standardization.
- the transformer core saturation identification criterion is: S(t)>S 0 ;
- S 0 has a value ranging from 1.15 to 1.4.
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Protection Of Transformers (AREA)
- Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
Abstract
一种基于电压量积分判别变压器铁芯饱和的方法，对于变压器某侧各相电压，当电压变化量超过设定的门槛值时，认为变压器状态突变，从电压状态突变后开始计算电压量绝对值的半波积分S 1(t)；计算电压突变时刻开始的半个周波电压变化量的积分的绝对值S 2(t)；令，若任一相满足S(t)＞S 0，则判定变压器铁芯饱和；其中：S e表示标幺化取的基准值；S 0为变压器铁芯饱和门槛值。该方法从励磁涌流产生的根源入手，对由电压变化引起的励磁涌流，如空载合闸励磁涌流、故障切除后电压恢复引起的励磁涌流、和应涌流、正常运行变压器在故障或一些操作引起的励磁涌流等，都能在半个周波左右的时间完成判别。
Description
本发明涉及一种基于电压量积分判别变压器铁芯饱和的方法，属于变压器技术领域。
变压器空载合闸或故障切除后电压恢复时会产生励磁涌流，空投或故障切除时电压幅值升高，而运行变压器在系统故障或一些操作(例如非同期合闸)时，一般电压幅值降低，且电压相角变化较大，也就是说在电压相角变化较大时，电压幅值降低也可能产生励磁涌流，这是以往分析励磁涌流产生的机理时没有注意到的。
两电力系统并列的理想条件是频率相等、电压幅值相等、相角差为零，实际合闸时很难达到，但只要偏差不大，并列合闸导致的冲击电流就比较小，不会危及电气设备，合闸后发电机组便能迅速拉入同步运行，不至于对整个系统造成不良后果。非同期合闸是指不管待合闸的断路器两端电力系统是否同期都进行合闸，非同期合闸可能是由于自动并列装置故障或工作人员误操作造成的。
发明内容
本发明的目的在于提供一种基于电压量积分判别变压器铁芯饱和的方法，既可以识别由空投或故障切除电压恢复导致的励磁涌流、一台变压器空充引起相邻变压器产生的和应涌流，也可以识别运行变压器在故障或一些操作(例如非同期合闸)时导致的励磁涌流。
为达到上述目的，本发明所采用的技术方案是：基于电压量积分判别变压器铁芯饱和的方法，对于变压器某侧各相电压，当电压变化量超过设定的门槛
值时，认为变压器状态突变；
从电压状态突变后开始计算电压量绝对值的半波积分S1(t)，表示状态突变后磁链的稳态周期分量的峰值；
计算电压突变时刻开始的半个周波电压变化量的积分的绝对值S2(t)，表示状态突变后磁链的非周期分量；
令
若任一相满足S(t)＞S0，则判定变压器铁芯饱和；
其中：Se表示标幺化取的基准值；S0为变压器铁芯饱和门槛值。
S1(t)和S2(t)的具体算法如下：
其中：Δu(t)＝u(t)-u(t-T)，u(t)表示t时刻的电压瞬时值，T表示电压周期；τ为积分变量，t＝0时表示变压器状态突变时刻。
S0的取值范围为1.15～1.4。
与现有技术相比，本发明所达到的有益效果是：
一、首次提出在电压幅值降低的情况下，电压相位的改变也可能使变压器铁芯饱和而产生励磁涌流，例如运行变压器在系统故障或一些操作(例如非同期合闸)时，也可能产生励磁涌流；
二、提出的判别方法从励磁涌流产生的根源入手，即变压器端电压变化导致的铁芯磁链饱和，既能判别空投或故障切除电压恢复导致的励磁涌流、和应涌流，也能判别运行变压器在系统故障或一些操作(例如非同期合闸)时导致的励磁涌流；
三、在半个周波左右的时间即可判别铁芯是否饱和，判别速度快，有利于提高变压器差动保护的动作速度。
基于电压量积分判别变压器铁芯饱和的方法，该方法从励磁涌流产生的根源着手，即变压器端电压(包括幅值和相角)变化所导致的磁链饱和，从电压状态突变后开始计算电压量绝对值的半波积分S1(t)，用来表示状态突变后磁链的稳态周期分量的峰值；以电压突变时刻开始的半个周波电压变化量的积分的绝对值S2(t)来表示状态突变后磁链的非周期分量，以二者之和S(t)表示状态突变后磁链所能达到的最大值。若S(t)大于门槛值S0，则判为铁芯饱和。该方法既可以识别由空投或故障切除电压恢复导致的励磁涌流，也可以识别运行变压器在系统故障或一些操作(例如非同期合闸)时导致的励磁涌流。
以单相为例，假设变压器状态变化前的相电压为
变压器状态变化后的稳态电压为
式中：Um为电压峰值；ω为电压角频率；
为电压初相角，
θ为状态突变前后电压相角差，θ∈[0,2π)；k1、k2为系数，k1＝[0,1]，k2∈[0,1]。
当k1∈[0,1)，k2＝1时为空载合闸励磁涌流或恢复性涌流问题；当k1＝1，k2∈(0,1]时为非同期合闸励磁涌流问题。
根据电压与磁链的关系，可得变压器状态突变前的磁链
式中：ψm＝Um/ω；C1为积分常数，表示剩磁。
变压器状态突变后的磁链为
式中：C2为任意常数。
假设在t＝0时变压器运行状态突变，由于磁链不能突变，有ψ1(0)＝ψ2(0)，从而
由上式可以看出，ψ2(t)包括稳态分量与直流分量两部分。由于很难直接求取状态突变后的磁链的最值，因而利用电压量等效替代。
式中：τ为积分变量。因而ψ2(t)的稳态分量
即可以用电压量的半波积分来表示。
式中：积分下限0表示状态突变时刻；积分上限T/2表示状态突变后半个周波，T＝2π/ω。因而ψ2(t)的直流分量
即可以用电压变化量的前半波积分来表示。对于非同期合闸，由于合闸前变压器已稳态运行一段时间，可以忽略剩磁，认为C1＝0。
综上所述，ψ2(t)可通过电压量间接求得，据此设计变压器铁芯饱和识别方案：为了尽快计算出变压器运行状态突变后磁链所能达到的最大值，从电压状态突变后开始计算电压量绝对值的半波积分S1(t)，用来表示状态突变后磁链的稳态周期分量的峰值，以电压突变时刻开始的半个周波电压变化量的积分的绝
对值S2(t)来表示状态突变后磁链的非周期分量，以二者之和S(t)表示状态突变后磁链所能达到的最大值。若S(t)大于门槛值S0，则判为铁芯饱和。相关公式如下：
式中：u(t)表示t时刻的电压瞬时值；Se表示标幺化取的基准值。
变压器铁芯饱和识别判据为：S(t)＞S0；
式中：S0的其取值范围为1.15～1.4。
以上所述仅是本发明的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明技术原理的前提下，还可以做出若干改进和变形，这些改进和变形也应视为本发明的保护范围。
Claims (3)
- 基于电压量积分判别变压器铁芯饱和的方法，其特征在于，对于变压器某侧各相电压，当电压变化量超过设定的门槛值时，认为变压器状态突变；从电压状态突变后开始计算电压量绝对值的半波积分S1(t)，对应状态突变后磁链的稳态周期分量的峰值；计算电压突变时刻开始的半个周波电压变化量的积分的绝对值S2(t)，对应状态突变后磁链的非周期分量；令若任一相满足S(t)＞S0，则判定变压器铁芯饱和；
其中：Se表示标幺化取的基准值；S0为变压器铁芯饱和门槛值。 - 根据权利要求1所述的基于电压量积分判别变压器铁芯饱和的方法，其特征在于，S1(t)和S2(t)的具体算法如下：
其中：Δu(t)＝u(t)-u(t-T)，u(t)表示t时刻的电压瞬时值，T表示电压周期；τ为积分变量，t＝0时表示变压器状态突变时刻。 - 根据权利要求2所述的基于电压量积分判别变压器铁芯饱和的方法，其特征在于，S0的取值范围为1.15～1.4。
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| CN109100666A (zh) * | 2018-07-23 | 2018-12-28 | 大连理工大学 | 一种用于空载变压器相控开关的剩磁测算交互平台及方法 |
| CN109541506A (zh) * | 2018-10-16 | 2019-03-29 | 中国电力科学研究院有限公司 | 一种电力变压器铁心磁特性测量和分析装置 |
| CN111103481A (zh) * | 2019-12-11 | 2020-05-05 | 国家电网有限公司 | 一种变压器励磁涌流的识别方法 |
| CN113219274A (zh) * | 2021-04-08 | 2021-08-06 | 国电南瑞科技股份有限公司 | 一种变压器励磁涌流识别方法、系统、储介质及计算设备 |
| CN113363939A (zh) * | 2021-05-12 | 2021-09-07 | 北京四方继保工程技术有限公司 | 基于变压器状态识别的不经励磁涌流闭锁的差动保护方法 |
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