CN1333503C

CN1333503C - Protection and fault positioning method for generator stator winding single-phase earthing

Info

Publication number: CN1333503C
Application number: CNB2004100061764A
Authority: CN
Inventors: 毕大强; 王祥珩; 王维俭
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2004-03-05
Filing date: 2004-03-05
Publication date: 2007-08-22
Anticipated expiration: 2024-03-05
Also published as: CN1560976A

Abstract

The present invention discloses a single phase grounding protection and fault positioning method for a generator stator winding, and belongs to the technical field of primary device relay protection of electric power systems. The present invention is characterized in that the present invention solves the defect that the parameters of a generator neutral point grounding device influence grounding resistance values; the present invention adopts the fault positioning when the phase-to-ground voltage and the zero sequence voltage of the generator end carry out the stator winding single phase grounding. The present invention solves the low precision problem of calculating grounding fault resistance values of the single phase grounding protection of the existing additional 20HZ power supply stator windings. The present invention can delimit error within 10%, and simultaneously, the present invention accordingly solves the fault positioning problem of the single phase grounding of a generator stator. Thereby, the present invention enhances the accuracy of protection and detection fault and the fault positioning.

Description

Protection and Fault Location Method for Single-phase Grounding of Generator Stator Winding

技术领域technical field

本发明属于电力系统主设备继电保护技术领域，尤其涉及一种外加20Hz电源和基波零序电压的发电机定子单相接地保护及故障定位方法。The invention belongs to the technical field of relay protection for main equipment in a power system, and in particular relates to a generator stator single-phase ground protection and fault location method with an external 20Hz power supply and fundamental wave zero-sequence voltage.

背景技术Background technique

相比发电机绕组内部短路故障，虽然定子接地故障的危害较小，但它是更严重短路故障的先兆。接地故障的及时发现将极大地降低发电机内部短路故障的发生几率，因此定子单相接地保护是发电机继电保护系统中的重要组成部分之一。Although a stator ground fault is less harmful than an internal short circuit fault in the generator winding, it is a precursor to a more serious short circuit fault. Timely detection of ground faults will greatly reduce the probability of generator internal short-circuit faults, so the stator single-phase ground protection is one of the important components of the generator relay protection system.

目前新建和将建的大型发电机采用配电变压器二次侧接电阻的中性点接地方式，装设外加电源型定子单相接地保护逐渐增多。现有外加20Hz电源定子接地保护主要采用导纳判据计算接地故障电阻，当接地故障电阻计算值低于电阻的高整定值时保护发信号告警，当接地故障电阻计算值小于电阻的低整定值时保护动作于跳闸。导纳判据中接地故障电阻R_g的计算值是单相接地保护执行的动作性质和监测绝缘水平的主要依据，准确地计算R_g是十分必要的。但现有运行的外加电源单相接地保护都没有考虑中性点接地变压器参数的影响，这导致接地电阻的计算结果将存在较大偏差。At present, large-scale generators newly built and to be built adopt the neutral point grounding method of the distribution transformer secondary side connection resistance, and the installation of external power supply type stator single-phase grounding protection is gradually increasing. The existing 20Hz power supply stator grounding protection mainly uses the admittance criterion to calculate the ground fault resistance. When the calculated value of the ground fault resistance is lower than the high setting value of the resistance, the protection sends an alarm signal; when the calculated value of the ground fault resistance is lower than the low setting value of the resistance Time protection acts on tripping. The calculated value of the ground fault resistance R _g in the admittance criterion is the main basis for the action nature of the single-phase ground protection and the monitoring of the insulation level, and it is very necessary to calculate R _g accurately. However, the existing single-phase grounding protection of external power supply does not consider the influence of the neutral point grounding transformer parameters, which leads to large deviations in the calculation results of grounding resistance.

因为缺少必要的故障信息，目前发电机定子单相接地保护还不具备故障定位的功能。若进一步能够诊断出故障位置，将为接地故障后的处理工作提供更多的便利。一方面若接地故障发生在发电机的机端引线或中性点外，保护能够诊断出故障位置，就有利于尽快排除故障和减少不必要的停机损失；另一方面若接地故障发生在发电机绕组内部，诊断出故障位置也有利于停机检修。Due to the lack of necessary fault information, the current generator stator single-phase ground protection does not have the function of fault location. If the fault location can be further diagnosed, it will provide more convenience for the processing work after the ground fault. On the one hand, if the ground fault occurs outside the generator terminal lead or neutral point, the protection can diagnose the fault location, which will help to eliminate the fault as soon as possible and reduce unnecessary shutdown losses; on the other hand, if the ground fault occurs in the generator Inside the winding, diagnosing the fault location is also conducive to shutting down for maintenance.

为了解决现有外加20Hz电源定子单相接地保护计算接地故障电阻值偏差较大的问题，本发明通过考虑发电机中性点接地装置等效参数对导纳型判据中由二次侧测量的电流和电压计算一次侧接地故障电阻值的影响，对导纳型判据进行修正，大幅提高了故障电阻计算的准确度，改善了保护动作行为的正确性。进一步本发明综合利用外加20Hz电源单相接地保护和基波零序电压保护所提供的故障信息，即外加20Hz电源定子单相接地保护计算的接地故障电阻值和零序电压保护中的机端各相对地电压和零序电压的变化，对定子绕组单相接地故障进行定位。In order to solve the problem that the existing 20Hz power supply stator single-phase grounding protection calculates the large deviation of the grounding fault resistance value, the present invention considers the equivalent parameters of the neutral point grounding device of the generator to the value measured by the secondary side in the admittance criterion The influence of the current and voltage on the calculation of the resistance value of the primary side grounding fault, and the correction of the admittance criterion greatly improve the accuracy of the calculation of the fault resistance and the correctness of the protection action behavior. Further, the present invention comprehensively utilizes the fault information provided by the single-phase ground protection of the external 20Hz power supply and the zero-sequence voltage protection of the fundamental wave, that is, the ground fault resistance value calculated by the single-phase ground protection of the stator of the external 20Hz power supply and the machine terminal in the zero-sequence voltage protection The phase-to-ground fault of the stator winding is located based on the change of the phase-to-ground voltage and the zero-sequence voltage.

发明内容Contents of the invention

本发明的目的在于提供一种发电机定子绕组单相接地的保护和故障定位方法。The purpose of the present invention is to provide a protection and fault location method for single-phase grounding of a stator winding of a generator.

发电机定子绕组单相接地的保护方法具体特征在于：The specific characteristics of the protection method for the single-phase grounding of the stator winding of the generator are as follows:

(1)发电机中性点与配电变压器一次侧的绕组断开，向配电变压器二次侧注入外加20Hz电源，由配电变压器的空载和短路实验测得配电变压器在20Hz下折算到二次侧的激磁阻抗R_m′、X_m′，短路阻抗R_k、X_k，把它们的值存入计算机；(1) The neutral point of the generator is disconnected from the winding on the primary side of the distribution transformer, and an additional 20Hz power supply is injected into the secondary side of the distribution transformer. The distribution transformer is converted at 20Hz according to the no-load and short-circuit experiments of the distribution transformer. To the secondary side excitation impedance R _m ′, X _m ′, short-circuit resistance R _k , X _k , store their values in the computer;

(2)设配电变压器在20Hz下折算到二次侧的下述各参数值为：(2) Assume that the following parameters of the distribution transformer converted to the secondary side at 20Hz are:

一次绕组的漏阻抗R₁′、X₁′：R₁′＝R_k/2，X₁′＝X_k/2，Leakage impedance R ₁ ′, X ₁ ′ of the primary winding: R ₁ ′=R _k /2, X ₁ ′=X _k /2,

二次绕组的漏阻抗R₂、X₂：R₂＝R_k/2，X₂＝X_k/2，Leakage impedance R ₂ and X ₂ of the secondary winding: R ₂ =R _k /2, X ₂ =X _k /2,

把R₁′、X₁′、R₂、X₂的值存入计算机；Store the values of R ₁ ′, X ₁ ′, R ₂ , and X ₂ into the computer;

(3)发电机中性点与配电变压器一次侧的绕组联接，向配电变压器的二次侧注入外加的20Hz电源；(3) The neutral point of the generator is connected to the winding on the primary side of the distribution transformer, and an additional 20Hz power supply is injected into the secondary side of the distribution transformer;

(4)计算机通过电压互感器和电流互感器测得二次侧的电压和电流，再以0.1秒为计算周期，即以10Hz为基频，用傅立叶算法提取二次谐波20Hz电压和电流

分量；(4) The computer measures the voltage and current on the secondary side through the voltage transformer and current transformer, and then takes 0.1 second as the calculation period, that is, takes 10Hz as the fundamental frequency, and extracts the second harmonic 20Hz voltage with the Fourier algorithm and current

weight;

(5)以变压器T型等效电路为基础，计算机求得折算到一次侧的接地故障电阻值R_g，它的步骤为：(5) Based on the T-type equivalent circuit of the transformer, the computer obtains the ground fault resistance R _g converted to the primary side, and its steps are as follows:

(5.1)计算机根据上述得到的R_m′、X_m′、R₂、X₂、并用以下公式计算得到变压器T型等效电路中流过R₁′+jX₁′且离开节点的电流折算到二次侧的发电机对地容抗-jX_C′两端的电压 (5.1) R _m ′, X _m ′, R ₂ , X ₂ , And use the following formula to calculate the current flowing through R ₁ ′+jX ₁ ′ and leaving the node in the T-type equivalent circuit of the transformer Converted to the generator's capacitance reactance to the ground of the secondary side - jX The voltage at both ends of _C ′

${\overset{\cdot}{I}}_{s} = \overset{\cdot}{I} - {\overset{\cdot}{I}}_{m},$

为流过R₂+jX₂的电流，指向上述节点，为流过R_m′+jX_m′的电流，离开上述节点，

{\overset{&Center Dot;}{I}}_{the s} = \overset{&Center Dot;}{I} - {\overset{\cdot}{I}}_{m},

is the current flowing through R ₂ +jX ₂ , pointing to the above node, is the current flowing through R _m ′+jX _m ′, leaving the above node,

${\overset{\cdot}{I}}_{m} = \frac{\overset{\cdot}{U} - {\overset{\cdot}{U}}_{2}}{R_{m}^{'} + j X_{m}^{'}},$

为R₂+jK₂上的电压，指向上述节点，

为中性点二次侧接地电阻R_n上的电压，

{\overset{&Center Dot;}{I}}_{m} = \frac{\overset{&Center Dot;}{u} - {\overset{&Center Dot;}{u}}_{2}}{R_{m}^{'} + j x_{m}^{'}},

is the voltage across R ₂ +jK ₂ , pointing to the above node,

is the voltage on the secondary side grounding resistance R _n of the neutral point,

${\overset{\cdot &Center Dot;}{U u}}_{s the s} = = \overset{\cdot &Center Dot;}{U u} - - {\overset{\cdot &Center Dot;}{U u}}_{22} - - {\overset{\cdot &Center Dot;}{U u}}_{11};;$

(5.2)得到二次侧计算的定子绕组对地导纳Y：(5.2) Obtain the ground admittance Y of the stator winding calculated on the secondary side:

$Y Y = = \frac{{\overset{\cdot &Center Dot;}{I I}}_{s the s}}{{\overset{\cdot &Center Dot;}{U u}}_{s the s}};;$

(5.3)得到折算到一次侧的接地故障电阻R_g：(5.3) Obtain the ground fault resistance R _g converted to the primary side:

$R_{g} = n^{2} \frac{1}{Re (Y)},$ n为配电变压器变比； $R_{g} = {no}^{2} \frac{1}{Re (Y)},$ n is the transformation ratio of the distribution transformer;

(6)计算机根据设定并存储的保护用接地故障电阻高整定值和低整定值来与上述测算的接地故障电阻值比较：(6) The computer compares the above calculated ground fault resistance value with the set and stored high setting value and low setting value of the protective ground fault resistance:

当上述测算的接地故障电阻值低于保护设定的接地电阻高整定值时发出告警信号；When the ground fault resistance value calculated above is lower than the high ground resistance setting value set by the protection, an alarm signal is sent;

当上述测算的接地故障电阻值低于保护设定的接地电阻低整定值时发出跳闸信号。When the ground fault resistance value calculated above is lower than the low ground resistance setting value set by the protection, a trip signal is issued.

发电机定子绕组单相接地的故障定位方法具体特征在于：The specific characteristics of the fault location method for the single-phase grounding of the stator winding of the generator are as follows:

(1)设定发电机三相绕组对地电容分别为C_a、C_b、C_c，发电机中性点接地电阻折算到一次侧的值为n²R_n，n为配电变压器变比；(1) Set the ground capacitance of the three-phase windings of the generator as C _a , C _b , and C _c respectively, and the value of the ground resistance of the neutral point of the generator converted to the primary side is n ² R _n , and n is the transformation ratio of the distribution transformer ;

(2)发电机中性点与配电变压器一次侧的绕组断开，向配电变压器二次侧注入外加20Hz电源，由配电变压器的空载和短路实验测得配电变压器在20Hz下折算到二次侧的激磁阻抗R_m′、X_m′，短路阻抗R_k、X_k，把它们的值存入计算机；(2) The neutral point of the generator is disconnected from the winding on the primary side of the distribution transformer, and an additional 20Hz power supply is injected into the secondary side of the distribution transformer. The distribution transformer is converted at 20Hz according to the no-load and short-circuit experiments of the distribution transformer. To the secondary side excitation impedance R _m ′, X _m ′, short-circuit resistance R _k , X _k , store their values in the computer;

(3)设配电变压器在20Hz下折算到二次侧的下述各参数值为：(3) Assume that the following parameters of the distribution transformer converted to the secondary side at 20Hz are:

(4)发电机中性点与配电变压器一次侧的绕组联接，向配电变压器的二次侧注入外加的20Hz电源；(4) The neutral point of the generator is connected to the winding on the primary side of the distribution transformer, and an additional 20Hz power supply is injected into the secondary side of the distribution transformer;

(5)计算机通过电压互感器和电流互感器测得二次侧的电压和电流，再以0.1秒为计算周期，即以10Hz为基频，用傅立叶算法提取二次谐波20Hz电压

和电流分量；(5) The computer measures the voltage and current on the secondary side through the voltage transformer and current transformer, and then takes 0.1 second as the calculation period, that is, takes 10Hz as the fundamental frequency, and uses the Fourier algorithm to extract the second harmonic 20Hz voltage

and current weight;

(6)以变压器T型等效电路为基础，计算机求得折算到一次侧的接地故障电阻值R_g，它的步骤为：(6) Based on the T-type equivalent circuit of the transformer, the computer obtains the ground fault resistance R _g converted to the primary side, and its steps are as follows:

(6.1)计算机根据上述得到的R_m′、X_m′、R₂、X₂、

并用以下公式计算得到变压器T型等效电路中流过R₁′+jX₁′且离开节点的电流

折算到二次侧的发电机对地容抗-jX_C′两端的电压 (6.1) R _m ′, X _m ′, R ₂ , X ₂ ,

And use the following formula to calculate the current flowing through R ₁ ′+jX ₁ ′ and leaving the node in the T-type equivalent circuit of the transformer

Converted to the generator's capacitance reactance to the ground of the secondary side - jX The voltage at both ends of _C ′

${\overset{\cdot}{I}}_{s} = \overset{\cdot}{I} - {\overset{\cdot}{I}}_{m},$ 为流过R₂+jX₂的电流，指向上述节点，

为流过R_m′+jX_m′的电流，离开上述节点，

{\overset{&Center Dot;}{I}}_{the s} = \overset{&Center Dot;}{I} - {\overset{&Center Dot;}{I}}_{m},

is the current flowing through R ₂ +jX ₂ , pointing to the above node,

is the current flowing through R _m ′+jX _m ′, leaving the above node,

${\overset{\cdot}{I}}_{m} = \frac{\overset{\cdot}{U} - {\overset{\cdot}{U}}_{2}}{R_{m}^{'} + j X_{m}^{'}},$ 为R₂+jX₂上的电压，指向上述节点，

为中性点二次侧接地电阻R_n上的电压，

{\overset{&Center Dot;}{I}}_{m} = \frac{\overset{&Center Dot;}{u} - {\overset{&Center Dot;}{u}}_{2}}{R_{m}^{'} + j x_{m}^{'}},

is the voltage on R ₂ +jX ₂ pointing to the above node,

${\overset{\cdot \cdot}{U u}}_{s the s} = = \overset{\cdot \cdot}{U u} - - {\overset{\cdot \cdot}{U u}}_{22} - - {\overset{\cdot \cdot}{U u}}_{11};;$

(6.2)得到二次侧计算的定子绕组对地导纳Y：(6.2) Obtain the ground admittance Y of the stator winding calculated on the secondary side:

(6.3)得到折算到一次侧的接地故障电阻R_g：(6.3) Get the ground fault resistance R _g converted to the primary side:

(7)判断发电机的故障相，它依次包含以下步骤：(7) judge the fault phase of generator, it comprises the following steps successively:

(7.1)计算机通过发电机机端电压互感器测得发电机机端三相对地电压，再用傅立叶算法提取机端三相对地基波电压

(7.1) The computer measures the three-phase-to-ground voltage at the generator terminal through the voltage transformer at the generator terminal, and then uses the Fourier algorithm to extract the three-phase-to-ground fundamental wave voltage at the generator terminal

(7.2)计算机通过发电机中性点电压互感器测量发电机零序电压，再用傅立叶算法提取中性点基波零序电压

(7.2) The computer measures the zero-sequence voltage of the generator through the neutral point voltage transformer of the generator, and then uses the Fourier algorithm to extract the zero-sequence voltage of the fundamental wave of the neutral point

(7.3)计算并存储发电机三相绕组基波电动势

{\overset{\cdot}{E}}_{a} = {\overset{\cdot}{U}}_{ag} - {\overset{\cdot}{U}}_{0},

{\overset{\cdot}{E}}_{b} = {\overset{\cdot}{U}}_{bg} - {\overset{\cdot}{U}}_{0},

{\overset{\cdot}{E}}_{c} = {\overset{\cdot}{U}}_{cg} - {\overset{\cdot}{U}}_{0};

(7.3) Calculate and store the fundamental electromotive force of the three-phase winding of the generator

{\overset{&Center Dot;}{E.}}_{a} = {\overset{&Center Dot;}{u}}_{ag} - {\overset{\cdot}{u}}_{0},

{\overset{\cdot}{E.}}_{b} = {\overset{\cdot}{u}}_{bg} - {\overset{&Center Dot;}{u}}_{0},

{\overset{\cdot}{E.}}_{c} = {\overset{\cdot}{u}}_{cg} - {\overset{\cdot}{u}}_{0};

(7.4)比较

与U_set：若

| {\overset{\cdot}{U}}_{0} | > U_{set},

则有定子绕组单相接地故障发生，其中：U_set为基波零序电压定子接地保护电压的整定值；若

| {\overset{\cdot}{U}}_{0} | < U_{set},

且R_g低至发生相应的保护动作，则接地故障发生在发电机中性点附近；(7.4) Comparison

with U _set : if

| {\overset{&Center Dot;}{u}}_{0} | > u_{set},

Then there is a stator winding single-phase ground fault, where: U _set is the setting value of the fundamental zero-sequence voltage stator ground protection voltage; if

| {\overset{\cdot}{u}}_{0} | < u_{set},

And R _g is low enough to cause the corresponding protection action, then the ground fault occurs near the neutral point of the generator;

(7.5)比较发电机机端三相对地电压的大小，根据基波有效值最小的一相为故障相的原则判断故障相；(7.5) Compare the magnitude of the three-phase-to-ground voltage at the generator terminal, and judge the fault phase according to the principle that the phase with the smallest effective value of the fundamental wave is the fault phase;

(8)利用步骤(6)得到的接地故障电阻值R_g计算故障相的故障位置α(故障点到中性点的匝数占一相串联总匝数的百分比)：(8) Use the ground fault resistance value R _g obtained in step (6) to calculate the fault position α of the fault phase (the number of turns from the fault point to the neutral point accounts for the percentage of the total number of turns in a phase):

故障相设为A相，当发电机绕组的三相电动势和对地电容不对称时，The fault phase is set as phase A, when the three-phase electromotive force of the generator winding and the capacitance to ground are asymmetrical,

$α α = = - - \frac{jω jω {C C}_{a a} {\overset{\cdot \cdot}{E E.}}_{a a} + + jω jω {C C}_{b b} {\overset{\cdot &Center Dot;}{E E.}}_{b b} + + jω jω {C C}_{c c} {\overset{\cdot &Center Dot;}{E E.}}_{c c} + + {\overset{\cdot \cdot}{U u}}_{00} ((\frac{11}{{n no}^{22} {R R}_{n no}} + + \frac{11}{{R R}_{g g}} + + jω jω {C C}_{Σ Σ}))}{\frac{{\overset{\cdot &Center Dot;}{E E.}}_{a a}}{{R R}_{g g}}};;$

当发电机绕组的三相电动势和对地电容对称时，When the three-phase electromotive force of the generator winding and the capacitance to the ground are symmetrical,

$α α = = - - \frac{{\overset{\cdot &Center Dot;}{U u}}_{00} ((\frac{11}{{n no}^{22} {R R}_{n no}} + + \frac{11}{{R R}_{g g}} + + jω jω {C C}_{Σ Σ}))}{\frac{{\overset{\cdot \cdot}{E E.}}_{a a}}{{R R}_{g g}}}$

其中：ω＝2πf，f电网频率；C_Σ＝C_a+C_b+C_c。Among them: ω=2πf, f grid frequency; C _Σ =C _a +C _b +C _c .

试验证明：本发明解决了现有外加20Hz电源定子单相接地保护中计算接地电阻值准确度不高的问题，其误差不超过10％；解决了发电机定子单相接地保护不具有故障定位功能的问题，对于金属性接地故障，其故障位置的误差在6％以内。The test proves that the present invention solves the problem that the accuracy of calculating the grounding resistance value in the existing 20Hz power supply stator single-phase grounding protection is not high, and the error does not exceed 10%; it solves the problem that the generator stator single-phase grounding protection does not have the fault location function For the problem of metallic ground fault, the error of its fault location is within 6%.

附图说明Description of drawings

图1是考虑配电变压器参数的高准确度外加20Hz电压源定子单相接地保护的T型等效电路。Figure 1 is a T-type equivalent circuit considering the high accuracy of distribution transformer parameters plus 20Hz voltage source stator single-phase grounding protection.

图2是发电机单相接地故障示意图。Figure 2 is a schematic diagram of a generator single-phase ground fault.

图3是本发明实施例的发电机部分接线示意图。Fig. 3 is a schematic diagram of part of the wiring of the generator according to the embodiment of the present invention.

图4是本发明实施例的定子单相接地保护及故障定位装置工作原理框图Fig. 4 is a block diagram of the working principle of the stator single-phase ground protection and fault location device according to the embodiment of the present invention

图5是本发明实施例中高准确度外加20Hz电源定子单相接地保护的主要流程图。Fig. 5 is a main flow chart of the high accuracy and 20 Hz power supply stator single-phase grounding protection in the embodiment of the present invention.

图6是本发明实施例中定子单相接地故障定位的主要流程图。Fig. 6 is a main flow chart of stator single-phase ground fault location in the embodiment of the present invention.

具体实施方式Detailed ways

下面结合附图来说明一下本发明的原理和具体的实施方式。The principle and specific implementation of the present invention will be described below in conjunction with the accompanying drawings.

过去分析外加电源型单相接地保护的等效电路时，认为配电变压器的漏阻抗很小可以忽略不计，激磁阻抗很大认为开路。实际上，配电变压器的激磁阻抗并非无穷大，漏抗也会产生压降，如图1是考虑配电变压器参数的T型等效电路。其中：R₁′、X₁′与R₂、X₂分别是一、二次侧绕组的漏阻抗；R_m′、X_m′是激磁阻抗；各参数为20Hz下折算到二次侧的值，其中R₁′＝R₂＝R_k/2，X₁′＝X₂＝X_k/2；R_k、X_k是配电变压器短路阻抗。考虑中性点接地装置配电变压器的漏阻抗和激磁阻抗影响，以变压器T型等效电路为基础，由二次侧20Hz电流和电压计算一次侧接地故障电阻值。In the past, when analyzing the equivalent circuit of external power supply type single-phase grounding protection, it was considered that the leakage impedance of the distribution transformer was small and negligible, and the excitation impedance was large and considered an open circuit. In fact, the excitation impedance of the distribution transformer is not infinite, and the leakage reactance will also produce a voltage drop. Figure 1 is a T-type equivalent circuit considering the parameters of the distribution transformer. Among them: R ₁ ′, X ₁ ′ and R ₂ , X ₂ are the leakage impedance of the primary and secondary side windings respectively; R _m ′, X _m ′ are the excitation impedance; each parameter is the value converted to the secondary side at 20Hz , where R ₁ '=R ₂ =R _k /2, X ₁ '=X ₂ =X _k /2; R _k and X _k are the short-circuit impedance of the distribution transformer. Considering the influence of the leakage impedance and excitation impedance of the distribution transformer of the neutral point grounding device, based on the T-type equivalent circuit of the transformer, the primary side grounding fault resistance value is calculated from the secondary side 20Hz current and voltage.

二次侧计算的定子对地导纳为 $Y = \frac{{\overset{\cdot}{I}}_{s}}{{\overset{\cdot}{U}}_{s}}$ The stator-to-ground admittance calculated on the secondary side is $Y = \frac{{\overset{&Center Dot;}{I}}_{the s}}{{\overset{&Center Dot;}{u}}_{the s}}$

折算到一次侧的接地电阻值为 $R_{g} = n^{2} \frac{1}{Re (Y)}$ Converted to the ground resistance value of the primary side $R_{g} = {no}^{2} \frac{1}{Re (Y)}$

其中：n为配电变压器变比， ${\overset{\cdot}{U}}_{s} = \overset{\cdot}{U} - {\overset{\cdot}{U}}_{2} - {\overset{\cdot}{U}}_{1},$ ${\overset{\cdot}{I}}_{s} = \overset{\cdot}{I} - {\overset{\cdot}{I}}_{m},$ ${\overset{\cdot}{U}}_{2} = \overset{\cdot}{I} (R_{2} + {jX}_{2}),$ ${\overset{\cdot}{U}}_{1} = {\overset{\cdot}{I}}_{s} (R_{1}^{'} + {jX}_{1}^{'}),$ ${\overset{\cdot}{I}}_{m} = \frac{\overset{\cdot}{U} - {\overset{\cdot}{U}}_{2}}{R_{m}^{'} + j X_{m}^{'}} .$ Among them: n is the transformation ratio of the distribution transformer, ${\overset{&Center Dot;}{u}}_{the s} = \overset{&Center Dot;}{u} - {\overset{\cdot}{u}}_{2} - {\overset{\cdot}{u}}_{1},$ ${\overset{\cdot}{I}}_{the s} = \overset{&Center Dot;}{I} - {\overset{&Center Dot;}{I}}_{m},$ ${\overset{&Center Dot;}{u}}_{2} = \overset{\cdot}{I} (R_{2} + {wxya}_{2}),$ ${\overset{&Center Dot;}{u}}_{1} = {\overset{\cdot}{I}}_{the s} (R_{1}^{'} + {wxya}_{1}^{'}),$ ${\overset{&Center Dot;}{I}}_{m} = \frac{\overset{&Center Dot;}{u} - {\overset{&Center Dot;}{u}}_{2}}{R_{m}^{'} + j x_{m}^{'}} .$

发电机机端各相对地电压大小的变化与故障位置和故障相有密切关系。当发电机中性点经折算到一次侧阻值为n²R_n的电阻接地时，a相α位置(故障点到中性点的匝数占一相串联总匝数的百分比)经过渡电阻R_g发生接地故障，如图2所示，机端三相对地电压为

中性点零序电压为

三相绕组对地电容分别为C_a、C_b、C_c。发电机三相绕组基波电动势分别为

{\overset{\cdot}{E}}_{a} = {\overset{\cdot}{U}}_{ag} - {\overset{\cdot}{U}}_{0},

{\overset{\cdot}{E}}_{b} = {\overset{\cdot}{U}}_{bg} - {\overset{\cdot}{U}}_{0},

{\overset{\cdot}{E}}_{c} = {\overset{\cdot}{U}}_{cg} - {\overset{\cdot}{U}}_{0} .

The change of the relative ground voltage at the generator terminal is closely related to the fault location and fault phase. When the neutral point of the generator is grounded by a resistor with a resistance value of n ² R _n on the primary side, the position α of phase a (the number of turns from the fault point to the neutral point as a percentage of the total number of turns in series in one phase) passes through the transition resistance A ground fault occurs at R _g , as shown in Figure 2, the three-phase-to-ground voltage at the machine terminal is

The neutral point zero sequence voltage is

The capacitances of the three-phase windings to ground are C _a , C _b , and C _c . The fundamental electromotive force of the three-phase winding of the generator is

{\overset{&Center Dot;}{E.}}_{a} = {\overset{&Center Dot;}{u}}_{ag} - {\overset{\cdot}{u}}_{0},

{\overset{\cdot}{E.}}_{b} = {\overset{&Center Dot;}{u}}_{bg} - {\overset{\cdot}{u}}_{0},

{\overset{\cdot}{E.}}_{c} = {\overset{\cdot}{u}}_{cg} - {\overset{&Center Dot;}{u}}_{0} .

由 $\frac{{\overset{\cdot}{U}}_{0}}{n^{2} R_{n}} + \frac{α {\overset{\cdot}{E}}_{a} + {\overset{\cdot}{U}}_{0}}{R_{g}} + ({\overset{\cdot}{E}}_{a} + {\overset{\cdot}{U}}_{0}) \cdot jω C_{a} + ({\overset{\cdot}{E}}_{b} + {\overset{\cdot}{U}}_{0}) \cdot jω C_{b} + ({\overset{\cdot}{E}}_{c} + {\overset{\cdot}{U}}_{0}) \cdot jω C_{c} = 0 - - - (1)$ Depend on $\frac{{\overset{&Center Dot;}{u}}_{0}}{{no}^{2} R_{no}} + \frac{α {\overset{&Center Dot;}{E.}}_{a} + {\overset{\cdot}{u}}_{0}}{R_{g}} + ({\overset{\cdot}{E.}}_{a} + {\overset{\cdot}{u}}_{0}) &Center Dot; jω C_{a} + ({\overset{&Center Dot;}{E.}}_{b} + {\overset{\cdot}{u}}_{0}) &Center Dot; jω C_{b} + ({\overset{\cdot}{E.}}_{c} + {\overset{\cdot}{u}}_{0}) &Center Dot; jω C_{c} = 0 - - - (1)$

可得 $α = - \frac{jω C_{a} {\overset{\cdot}{E}}_{a} + jω C_{b} {\overset{\cdot}{E}}_{b} + jω C_{c} {\overset{\cdot}{E}}_{c} + {\overset{\cdot}{U}}_{0} (\frac{1}{n^{2} R_{n}} + \frac{1}{R_{g}} + jω C_{Σ})}{\frac{{\overset{\cdot}{E}}_{a}}{R_{g}}} - - - (2)$ Available $α = - \frac{jω C_{a} {\overset{\cdot}{E.}}_{a} + jω C_{b} {\overset{&Center Dot;}{E.}}_{b} + jω C_{c} {\overset{&Center Dot;}{E.}}_{c} + {\overset{\cdot}{u}}_{0} (\frac{1}{{no}^{2} R_{no}} + \frac{1}{R_{g}} + jω C_{Σ})}{\frac{{\overset{&Center Dot;}{E.}}_{a}}{R_{g}}} - - - (2)$

${\overset{\cdot &Center Dot;}{U u}}_{00} = = - - \frac{\frac{α α {\overset{\cdot &Center Dot;}{E E.}}_{a a}}{{R R}_{g g}} + + jω jω {C C}_{a a} {\overset{\cdot &Center Dot;}{E E.}}_{a a} + + jω jω {C C}_{b b} {\overset{\cdot &Center Dot;}{E E.}}_{b b} + + jω jω {C C}_{c c} {\overset{\cdot &Center Dot;}{E E.}}_{c c}}{\frac{11}{{n no}^{22} {R R}_{n no}} + + \frac{11}{{R R}_{g g}} + + jω jω {C C}_{Σ Σ}} - - - - - - ((33))$

当发电机绕组的三相电动势和对地电容对称时有When the three-phase electromotive force of the generator winding and the capacitance to the ground are symmetrical, there is

$α α = = - - \frac{{\overset{\cdot &Center Dot;}{U u}}_{00} ((\frac{11}{{n no}^{22} {R R}_{n no}} + + \frac{11}{{R R}_{g g}} + + jω jω {C C}_{Σ Σ}))}{\frac{{\overset{\cdot &Center Dot;}{E E.}}_{a a}}{{R R}_{g g}}} - - - - - - ((44))$

${\overset{\cdot &Center Dot;}{U u}}_{00} = = - - \frac{α α {\overset{\cdot &Center Dot;}{E E.}}_{a a}}{\frac{{R R}_{g g}}{{n no}^{22} {R R}_{n no}} + + 11 + + jω jω {C C}_{Σ Σ} {R R}_{g g}} - - - - - - ((55))$

发电机机端三相对地电压分别为The three phase-to-ground voltages at the generator terminal are respectively

$| | {\overset{\cdot &Center Dot;}{U u}}_{ag ag} | | = = | | {\overset{\cdot &Center Dot;}{E E.}}_{a a} + + {\overset{\cdot &Center Dot;}{U u}}_{00} | | = = | | 11 - - \frac{α α}{\frac{{R R}_{g g}}{{n no}^{22} {R R}_{n no}} + + 11 + + jω jω {C C}_{Σ Σ} {R R}_{g g}} | | \cdot &Center Dot; | | {\overset{\cdot &Center Dot;}{E E.}}_{a a} | | - - - - - - ((66))$

$| | {\overset{\cdot &Center Dot;}{U u}}_{bg bg} | | = = | | {\overset{\cdot &Center Dot;}{E E.}}_{b b} + + {\overset{\cdot &Center Dot;}{U u}}_{00} | | = = | | ((- - \frac{11}{22} - - j j \frac{\sqrt{33}}{22})) - - \frac{α α}{\frac{{R R}_{g g}}{{n no}^{22} {R R}_{n no}} + + 11 + + jω jω {C C}_{Σ Σ} {R R}_{g g}} | | \cdot &Center Dot; | | {\overset{\cdot &Center Dot;}{E E.}}_{a a} | | - - - - - - ((77))$

$| | {\overset{\cdot \cdot}{U u}}_{cg cg} | | = = | | {\overset{\cdot \cdot}{E E.}}_{c c} + + {\overset{\cdot &Center Dot;}{U u}}_{00} | | = = | | ((- - \frac{11}{22} + + j j \frac{\sqrt{33}}{22})) - - \frac{α α}{\frac{{R R}_{g g}}{{n no}^{22} {R R}_{n no}} + + 11 + + jω jω {C C}_{Σ Σ} {R R}_{g g}} | | \cdot &Center Dot; | | {\overset{\cdot &Center Dot;}{\underset{. .}{E E.}}}_{a a} | | - - - - - - ((88))$

比较三相对地电压的大小，有Comparing the magnitude of the three phase-to-ground voltages, there are

${| | {\overset{\cdot &Center Dot;}{U u}}_{cg cg} | |}^{22} - - {| | {\overset{\cdot &Center Dot;}{U u}}_{bg bg} | |}^{22} = = \sqrt{33} αω αω {C C}_{Σ Σ} {R R}_{g g} - - - - - - ((99))$

${| | {\overset{\cdot &Center Dot;}{U u}}_{bg bg} | |}^{22} - - {| | {\overset{\cdot &Center Dot;}{U u}}_{ag ag} | |}^{22} = = α α [[((\frac{\sqrt{33}}{{n no}^{22} {R R}_{n no}} - - ω ω {C C}_{Σ Σ})) {R R}_{g g} + + \sqrt{33}]] - - - - - - ((1010))$

当发电机中性点通过电阻接地时，一次侧电阻通常选取 $n^{2} R_{n} \leq \frac{1}{ω C_{Σ}},$ 这样(10)式恒大于零，即正常相b相的对地电压大于故障相a相的对地电压。由(9)式可知，正常相c相的对地电压不小于另一正常相b相的对地电压。综合所述，故障相的机端对地电压最低。When the neutral point of the generator is grounded through a resistor, the primary side resistor is usually selected ${no}^{2} R_{no} \leq \frac{1}{ω C_{Σ}},$ In this way (10) is always greater than zero, that is, the voltage of the normal phase b to the ground is greater than the voltage of the faulty phase a to the ground. It can be seen from formula (9) that the ground voltage of the normal phase c is not less than the ground voltage of the other normal phase b. In summary, the terminal-to-ground voltage of the faulty phase is the lowest.

本发明采用的装置与现有微机继电保护装置类似，是现有的技术，如图3和图4所示。图3中G表示发电机，T表示主变压器，T_n表示发电机中性点配电变压器，R_n是中性点二次侧接地电阻，VD是二次侧分压器，CT是中间电流互感器，TV是发电机机端电压互感器。本实施例中为外加20Hz电源是由发电机中性点配电变压器二次侧经20Hz带通滤波器注入发电机，通过分压器和中间电流互感器测量二次侧的电压

和电流

通过机端电压互感器TV测量发电机机端各相对地电压

这些电流、电压量输入到定子单相接地保护及故障定位装置中进行运算分析。图4是实施例中定子单相接地保护及故障定位装置的具体实现，电压

和电流经交流变换器(V/V、I/V)将这些二次电压和电流转换成小电压信号、经低通滤波器滤波，CPLD复杂可编程序控制器控制多路开关切换各路输入量以及16位A/D转换器进行模拟量和数字量的转换，各数字量输入到CPU中(DSP TMS320C32)完成定子单相接地保护及故障定位，根据计算结果由CPLD复杂可编程序控制器控制开关量输出，由相应的继电器执行发信或跳闸，同时给出故障信息。其中EEPROM用来存储程序和保护定值，SRAM和FLASH用来存储保护计算的中间变量和故障信息等。The device adopted by the present invention is similar to the existing microcomputer relay protection device, and is an existing technology, as shown in Fig. 3 and Fig. 4 . In Figure 3, G represents the generator, T represents the main transformer, T _n represents the neutral point distribution transformer of the generator, R _n is the secondary side grounding resistance of the neutral point, VD is the secondary side voltage divider, and CT is the intermediate current Transformer, TV is the generator terminal voltage transformer. In this embodiment, the external 20Hz power supply is injected into the generator through the secondary side of the distribution transformer at the neutral point of the generator through a 20Hz band-pass filter, and the voltage on the secondary side is measured through a voltage divider and an intermediate current transformer.

and current

Measure the phase-to-ground voltage at the generator terminal through the terminal voltage transformer TV

These currents and voltages are input to the stator single-phase grounding protection and fault location device for calculation and analysis. Fig. 4 is the specific implementation of the stator single-phase ground protection and fault location device in the embodiment, the voltage

and current These secondary voltages and currents are converted into small voltage signals by AC converters (V/V, I/V), filtered by low-pass filters, and CPLD complex programmable controllers control multiple switches to switch various input quantities and The 16-bit A/D converter converts the analog and digital quantities, and each digital quantity is input to the CPU (DSP TMS320C32) to complete the stator single-phase grounding protection and fault location. According to the calculation results, the CPLD complex programmable controller controls the switch Quantitative output, the corresponding relay will send a letter or trip, and give fault information at the same time. Among them, EEPROM is used to store programs and protect fixed values, and SRAM and FLASH are used to store intermediate variables and fault information for protection calculations.

本发明实施例中的高准确度外加20Hz电源定子单相接地保护的主要流程如图5所示：The main process of the high accuracy plus 20Hz power supply stator single-phase grounding protection in the embodiment of the present invention is shown in Figure 5:

(1)取中性点配电变压器的测量二次侧的电流和电压，以0.1秒为计算周期，即以10Hz为基频，由傅立叶算法提取二次谐波20Hz电压

和电流

分量。(1) Measure the current and voltage on the secondary side of the neutral point distribution transformer, take 0.1 second as the calculation period, that is, take 10Hz as the fundamental frequency, and extract the second harmonic 20Hz voltage by Fourier algorithm

and current

portion.

(2)考虑中性点接地装置配电变压器的漏阻抗和激磁阻抗影响，以变压器T型等效电路为基础，由二次侧20Hz电流和电压计算一次侧接地故障电阻值。(2) Considering the influence of the leakage impedance and excitation impedance of the distribution transformer of the neutral point grounding device, based on the T-type equivalent circuit of the transformer, the primary side grounding fault resistance value is calculated from the secondary side 20Hz current and voltage.

二次侧计算的定子对地导纳为 $Y = \frac{{\overset{\cdot}{I}}_{s}}{{\overset{\cdot}{U}}_{s}}$ The stator-to-ground admittance calculated on the secondary side is $Y = \frac{{\overset{\cdot}{I}}_{the s}}{{\overset{\cdot}{u}}_{the s}}$

折算到一次侧的接地故障电阻值为 $R_{g} = n^{2} \frac{1}{Re (Y)}$ Converted to the ground fault resistance value of the primary side $R_{g} = {no}^{2} \frac{1}{Re (Y)}$

其中：n为配电变压器变比， ${\overset{\cdot}{U}}_{s} = \overset{\cdot}{U} - {\overset{\cdot}{U}}_{2} - {\overset{\cdot}{U}}_{1},$ ${\overset{\cdot}{I}}_{s} = \overset{\cdot}{I} - {\overset{\cdot}{I}}_{m},$ ${\overset{\cdot}{U}}_{2} = \overset{\cdot}{I} (R_{2} + {jX}_{2}),$ ${\overset{\cdot}{U}}_{1} = {\overset{\cdot}{I}}_{s} (R_{1}^{'} + {jX}_{1}^{'}),$ ${\overset{\cdot}{I}}_{m} = \frac{\overset{\cdot}{U} - {\overset{\cdot}{U}}_{2}}{R_{m}^{'} + {jX}_{m}^{'}};$ R₁′、X₁′与R₂、X₂′分别是一、二次侧绕组的漏阻抗；R_m′、X_m′是激磁阻抗；各参数为20Hz下折算到二次侧的值，其中R₁′＝R₂＝R_k/2，X₁′＝X₂＝X_k/2；R_k、X_k是配电变压器短路阻抗。Among them: n is the transformation ratio of the distribution transformer, ${\overset{&Center Dot;}{u}}_{the s} = \overset{&Center Dot;}{u} - {\overset{&Center Dot;}{u}}_{2} - {\overset{&Center Dot;}{u}}_{1},$ ${\overset{&Center Dot;}{I}}_{the s} = \overset{&Center Dot;}{I} - {\overset{&Center Dot;}{I}}_{m},$ ${\overset{&Center Dot;}{u}}_{2} = \overset{\cdot}{I} (R_{2} + {wxya}_{2}),$ ${\overset{\cdot}{u}}_{1} = {\overset{&Center Dot;}{I}}_{the s} (R_{1}^{'} + {wxya}_{1}^{'}),$ ${\overset{&Center Dot;}{I}}_{m} = \frac{\overset{&Center Dot;}{u} - {\overset{\cdot}{u}}_{2}}{R_{m}^{'} + {wxya}_{m}^{'}};$ R ₁ ′, X ₁ ′ and R ₂ , X ₂ ′ are the leakage impedance of the primary and secondary side windings respectively; R _m ′, X _m ′ are the excitation impedance; each parameter is the value converted to the secondary side at 20Hz, Where R ₁ '=R ₂ =R _k /2, X ₁ '=X ₂ =X _k /2; R _k and X _k are the short-circuit impedance of the distribution transformer.

(3)本实施例中当计算的接地故障电阻值R_g低于保护的高整定值5kΩ时发告警信号，当接地故障电阻值低于保护的低整定值500Ω时发跳闸信号，得到开关量输出，由继电器执行动作。(3) In this embodiment, when the calculated ground fault resistance value R _g is lower than the protection high setting value 5kΩ, an alarm signal is sent, and when the ground fault resistance value is lower than the protection low setting value 500Ω, a trip signal is sent, and the switching value is obtained output, the action is performed by the relay.

在本发明的高准确度外加20Hz电源定子单相接地保护实施例中，当发电机经不同值电阻发生接地故障时，表1是本发明的高准确度外加20Hz电源定子单相接地保护计算的接地故障电阻值与原有不考虑配电变压器参数的导纳判据计算的接地故障电阻值的比较。从计算结果可以看出，不考虑配电变压器参数影响时，接地故障电阻的计算结果误差很大，尤其在接地故障电阻小于1kΩ时，接地故障电阻的计算误差更大。接地故障电阻在小于低整定值时动作于跳闸，但计算结果偏大将严重影响保护的动作性质，对发电机产生危害。而考虑配电变压器参数影响时，从计算结果可以看出，一次侧接地故障电阻值的计算值误差大幅降低，特别是在接地故障电阻较小时，保护需要跳闸的阻值段，计算准确度很高，这就为保护判据执行正确的动作行为提供了保证，也为进一步故障定位做了准备条件。In the embodiment of the high-accuracy plus 20Hz power supply stator single-phase grounding protection embodiment of the present invention, when the generator has a ground fault through different value resistances, Table 1 is the high-accuracy plus 20Hz power supply stator single-phase grounding protection calculation of the present invention The comparison between the ground fault resistance value and the ground fault resistance value calculated by the original admittance criterion without considering the distribution transformer parameters. It can be seen from the calculation results that when the influence of distribution transformer parameters is not considered, the calculation result error of the ground fault resistance is very large, especially when the ground fault resistance is less than 1kΩ, the calculation error of the ground fault resistance is even greater. When the ground fault resistance is less than the low setting value, it will act as a trip, but if the calculation result is too large, it will seriously affect the action nature of the protection and cause harm to the generator. When considering the influence of distribution transformer parameters, it can be seen from the calculation results that the calculation value error of the ground fault resistance value on the primary side is greatly reduced, especially when the ground fault resistance is small, the protection needs to trip the resistance section, and the calculation accuracy is very high. High, this provides a guarantee for the protection criterion to implement the correct action behavior, and also prepares the conditions for further fault location.

表1Table 1

一次侧实际接地故障电阻kΩPrimary side actual earth fault resistance kΩ 二次侧输入装置20Hz电压/VSecondary side input device 20Hz voltage/V 二次侧输入装置20Hz电流/ASecondary side input device 20Hz current/A 不考虑参数影响接地故障电阻 Regardless of the parameters affecting the ground fault resistance 考虑参数影响接地故障电阻 Consider the parameters affecting the ground fault resistance 计算值/kΩ Calculated value/kΩ 误差/％ Error/% 计算值/kΩ Calculated value/kΩ 误差/％ Error/% 10 10 2.833∠177.47° 2.833∠177.47° 0.301∠208.31° 0.301∠208.31° 8.824 8.824 11.76 11.76 9.265 9.265 7.35 7.35 9 9 2.775∠158.24° 2.775∠158.24° 0.315∠186.44° 0.315∠186.44° 8.023 8.023 10.85 10.85 8.376 8.376 6.93 6.93 8 8 2.719∠83.53° 2.719∠83.53° 0.335∠109.15° 0.335∠109.15° 7.024 7.024 12.20 12.20 7.488 7.488 6.40 6.40 7 7 2.637∠317.79° 2.637∠317.79° 0.359∠340.53° 0.359∠340.53° 6.396 6.396 8.62 8.62 6.576 6.576 6.05 6.05 6 6 2.544∠61.77° 2.544∠61.77° 0.389∠81.26° 0.389∠81.26° 5.556 5.556 7.40 7.40 5.671 5.671 5.48 5.48 5 5 2.418∠230.10° 2.418∠230.10° 0.429∠246.07° 0.429∠246.07° 4.699 4.699 6.02 6.02 4.742 4.742 5.16 5.16 4 4 2.255∠142.36° 2.255∠142.36° 0.482∠154.58° 0.482∠154.58° 3.840 3.840 4.00 4.00 3.821 3.821 4.475 4.475 3 3 2.034∠49.88° 2.034∠49.88° 0.559∠57.89° 0.559∠57.89° 2.955 2.955 1.50 1.50 2.879 2.879 4.03 4.03 2 2 1.712∠181.33° 1.712∠181.33° 0.672∠184.43° 0.672∠184.43° 2.046 2.046 2.30 2.30 1.934 1.934 3.30 3.30 1 1 1.204∠23.42° 1.204∠23.42° 0.854∠19.67° 0.854∠19.67° 1.126 1.126 12.60 12.60 0.982 0.982 1.80 1.80 0.9 0.9 1.138∠356.86° 1.138∠356.86° 0.879∠352.14° 0.879∠352.14° 1.034 1.034 14.88 14.88 0.887 0.887 1.44 1.44 0.8 0.8 1.065∠154.54° 1.065∠154.54° 0.904∠148.82° 0.904∠148.82° 0.944 0.944 18.00 18.00 0.790 0.790 1.25 1.25 0.7 0.7 0.991∠307.69° 0.991∠307.69° 0.932∠300.72° 0.932∠300.72° 0.850 0.850 21.42 21.42 0.695 0.695 0.71 0.71 0.6 0.6 0.909∠270.93° 0.909∠270.93° 0.963∠262.39° 0.963∠262.39° 0.756 0.756 26 26 0.597 0.597 0.50 0.50 0.5 0.5 0.823∠307.59° 0.823∠307.59° 0.995∠297.43° 0.995∠297.43° 0.664 0.664 32.80 32.80 0.501 0.501 0.20 0.20 0.4 0.4 0.731∠65.15° 0.731∠65.15° 1.029∠52.75° 1.029∠52.75° 0.572 0.572 43.00 43.00 0.403 0.403 0.75 0.75 0.3 0.3 0.632∠137.37° 0.632∠137.37° 1.067∠122.37° 1.067∠122.37° 0.483 0.483 61.00 61.00 0.305 0.305 1.6667 1.6667 0.2 0.2 0.526∠316.02° 0.526∠316.02° 1.106∠296.78° 1.106∠296.78° 0.396 0.396 98.00 98.00 0.206 0.206 3.00 3.00 0.1 0.1 0.420∠283.84° 0.420∠283.84° 1.151∠258.56° 1.151∠258.56° 0.313 0.313 213.00 213.00 0.110 0.110 10.00 10.00 0(金属性接地) 0 (metallic ground) 0.308∠24.40° 0.308∠24.40° 1.195∠347.45° 1.195∠347.45° 0.246 0.246 0.011 0.011

本发明实施例中的定子单相接地故障定位的主要流程如图6所示：The main flow of stator single-phase ground fault location in the embodiment of the present invention is shown in Figure 6:

(1)由发电机机端电压互感器测量发电机机端各相对地电压，由发电机中性点电压互感器测量发电机零序电压(发电机的零序电压也可由机端开口三角电压互感器测得U_t)。再由傅立叶算法提取机端三相对地基波电压分别为

中性点基波零序电压为同时计算发电机三相绕组基波电动势分别为

{\overset{\cdot}{E}}_{a} = {\overset{\cdot}{U}}_{ag} - {\overset{\cdot}{U}}_{0},

{\overset{\cdot}{E}}_{b} = {\overset{\cdot}{U}}_{bg} - {\overset{\cdot}{U}}_{0},

{\overset{\cdot}{E}}_{c} = {\overset{\cdot}{U}}_{cg} - {\overset{\cdot}{U}}_{0} .

(1) Measure the relative ground voltage of the generator terminal by the voltage transformer at the generator terminal, and measure the zero-sequence voltage of the generator by the neutral point voltage transformer of the generator (the zero-sequence voltage of the generator can also be measured by the delta voltage at the open terminal of the generator. Transformer measured U _t ). Then the Fourier algorithm is used to extract the three phase-to-ground fundamental wave voltages at the machine terminal as

The fundamental zero-sequence voltage of the neutral point is At the same time, the fundamental electromotive force of the three-phase windings of the generator is calculated as

{\overset{\cdot}{E.}}_{a} = {\overset{&Center Dot;}{u}}_{ag} - {\overset{&Center Dot;}{u}}_{0},

{\overset{&Center Dot;}{E.}}_{b} = {\overset{&Center Dot;}{u}}_{bg} - {\overset{\cdot}{u}}_{0},

{\overset{&Center Dot;}{E.}}_{c} = {\overset{\cdot}{u}}_{cg} - {\overset{\cdot}{u}}_{0} .

(2)由基波零序电压定子接地保护( $| {\overset{\cdot}{U}}_{0} | > U_{set},$ 实施例中U_set＝5V)检测出有接地故障发生。(2) Stator grounding protection by fundamental zero-sequence voltage ( $| {\overset{&Center Dot;}{u}}_{0} | > u_{set},$ In the embodiment, U _set =5V) detects that a ground fault occurs.

(3)比较发电机三相对地电压的大小判断故障相，基波有效值最小的为故障相。(3) Compare the three phase-to-ground voltages of the generator to determine the fault phase, and the phase with the smallest effective value of the fundamental wave is the fault phase.

(4)当发电机发生单相接地故障时，利用高准确度外加20Hz电源定子单相接地保护计算的接地故障电阻值R_g，计算故障位置α(故障点到中性点的匝数占一相串联总匝数的百分比)(4) When a single-phase ground fault occurs in the generator, use the ground fault resistance value R _g calculated with high accuracy and 20Hz power stator single-phase ground protection to calculate the fault location α (the number of turns from the fault point to the neutral point accounts for one Percentage of total turns in series)

$α α = = - - \frac{jω jω {C C}_{a a} {\overset{\cdot &Center Dot;}{E E.}}_{a a} + + jω jω {C C}_{b b} {\overset{\cdot &Center Dot;}{E E.}}_{b b} + + jω jω {C C}_{c c} {\overset{\cdot &Center Dot;}{E E.}}_{c c} + + {\overset{\cdot &Center Dot;}{U u}}_{00} ((\frac{11}{{n no}^{22} {R R}_{n no}} + + \frac{11}{{R R}_{g g}} + + jω jω {C C}_{Σ Σ}))}{\frac{{\overset{\cdot &Center Dot;}{E E.}}_{a a}}{{R R}_{g g}}} - - - - - - ((11))$

当发电机绕组的三相电动势和对地电容对称时，有故障位置的计算进一步简化为When the three-phase electromotive force of the generator winding and the ground capacitance are symmetrical, the calculation of the fault location is further simplified as

$α α = = - - \frac{{\overset{\cdot &Center Dot;}{U u}}_{00} ((\frac{11}{{n no}^{22} {R R}_{n no}} + + \frac{11}{{R R}_{g g}} + + jω jω {C C}_{Σ Σ}))}{\frac{{\overset{\cdot &Center Dot;}{E E.}}_{a a}}{{R R}_{g g}}} - - - - - - ((22))$

其中C_∑＝C_a+C_b+C_c，C_a、C_b、C_c分别为发电机三相绕组对地电容。Where C _∑ ＝C _a +C _b +C _c , C _a , C _b , and C _c are the ground capacitances of the three-phase windings of the generator.

(5)如果基波零序电压定子接地保护没有动作，而外加20Hz电源保护计算的接地故障电阻值较低，相应保护动作，那么接地故障发生在发电机的中性点附近。(5) If the fundamental zero-sequence voltage stator grounding protection does not operate, but the grounding fault resistance value calculated by the external 20Hz power protection is low, and the corresponding protection operates, then the grounding fault occurs near the neutral point of the generator.

在本发明的定子单相接地故障定位方法实施例中，在发电机a相绕组不同的位置经不同的故障电阻进行了接地故障试验，表2给出了接地故障相的判别和故障位置计算的结果。可以看出，发生单相接地故障时，a相电压最低，由机端三相对地电压的大小关系能够正确判断出故障相别是a相，同时故障位置的计算结果也与实际故障位置很接近，误差较小，表现出了良好故障定位效果。In the embodiment of the stator single-phase ground fault location method of the present invention, the ground fault test is carried out at different positions of the a-phase winding of the generator through different fault resistances. Table 2 provides the ground fault phase discrimination and fault position calculation. result. It can be seen that when a single-phase ground fault occurs, the voltage of phase a is the lowest, and the relationship between the three phase-to-ground voltages at the machine terminal can correctly determine that the fault phase is phase a, and the calculation result of the fault location is also very close to the actual fault location , the error is small, showing a good fault location effect.

表2Table 2

接地故障电阻/kΩGround fault resistance/kΩ U_ag/VU _ag /V U_bg/V _Ubg /V U_cg/VU _cg /V 故障相判别 Fault phase discrimination 故障位置 Fault location 实际值 actual value 计算值 Calculated 误差 error 0金属性接地0 metallic ground 56.40 56.40 60.07 60.07 61.50 61.50 a a 5％ 5% 5.05％ 5.05% 1.00％ 1.00% 53.07 53.07 61.82 61.82 63.42 63.42 a a 10％ 10% 10.60％ 10.60% 6.00％ 6.00% 36.15 36.15 75.10 75.10 73.62 73.62 a a 40％ 40% 39.45％ 39.45% 1.38％ 1.38% 0.01 0.01 103.60 103.60 103.65 103.65 a a 100％ 100% 99.98％ 99.98% 0.02％ 0.02% 5.4325.432 57.57 57.57 59.32 59.32 59.80 59.80 a a 5％ 5% 4.35％ 4.35% 13.00％ 13.00% 56.52 56.52 60.95 60.95 61.62 61.62 a a 10％ 10% 10.22％ 10.22% 2.20％ 2.20% 47.42 47.42 66.70 66.70 66.72 66.72 a a 40％ 40% 39.65％ 39.65% 0.86％ 0.86% 28.62 28.62 78.75 78.75 81.00 81.00 a a 100％ 100% 100.85％ 100.85% 0.85％ 0.85% 1111 57.97 57.97 58.70 58.70 59.80 59.80 a a 5％ 5% 5.19％ 5.19% 3.80％ 3.80% 57.17 57.17 60.65 60.65 61.05 61.05 a a 10％ 10% 11.78％ 11.78% 17.80％ 17.80% 51.27 51.27 64.42 64.42 64.47 64.47 a a 40％ 40% 41.05％ 41.05% 2.63％ 2.63% 38.85 38.85 71.60 71.60 73.05 73.05 a a 100％ 100% 101.81％ 101.81% 1.81％ 1.81%

Claims

1. the guard method of generator unit stator winding single-phase earthing is characterized in that it contains following steps successively:

(1) winding of generator neutral point and distribution transformer primary side disconnects, and injects to the distribution transformer secondary side to add the 20Hz power supply, records distribution transformer is converted secondary side under 20Hz excitatory impedance R by the zero load and the short circuit experiment of distribution transformer _m', X _M', short-circuit impedance R _k, X _k, their value is deposited in computer;

(2) the establishing piezoelectric transformer is converted following each parameter value of secondary side and is under 20Hz: the leakage impedance R of a winding ₁', X ₁': R ₁'=R _k/ 2, X ₁'=X _k/ 2, the leakage impedance R of secondary winding ₂, X ₂: R ₂=R _k/ 2, X ₂=X _k/ 2, R ₁', X ₁', R ₂, X ₂Value deposit computer in;

(3) generator neutral point connects with the winding of distribution transformer primary side, injects the 20Hz power supply that adds to the secondary side of distribution transformer;

(4) computer records the voltage and current of secondary side by the voltage transformer summation current transformer, is computing cycle with 0.1 second again, promptly is fundamental frequency with 10Hz, extracts second harmonic 20Hz voltage  and electric current with fourier algorithm

Component;

(5) based on transformer T type equivalent electric circuit, computer is tried to achieve the ground fault resistance value R that converts primary side _g, its step is:

(5.1) computer is according to the above-mentioned R that obtains _m', X _m', R ₂, X ₂, , , and calculate in the transformer T type equivalent electric circuit with following formula and to flow through R ₁'+jX ₁' and leave the electric current of node , convert the generator capacitance to earth-jX of secondary side _CThe voltage  at ' two ends _s:

{\overset{\cdot}{I}}_{s} = \overset{\cdot}{I} - {\overset{\cdot}{I}}_{m}

For flowing through R ₂+ jX ₂Electric current, point to above-mentioned node,

For flowing through R _m'+jX _m' electric current, leave above-mentioned node,

{\overset{\cdot}{I}}_{m} = \frac{\overset{\cdot}{U} - {\overset{\cdot}{U}}_{2}}{R_{m}^{'} + j X_{m}^{'}}

,  ₂Be R ₂+ jX ₂On voltage, point to above-mentioned node,

 is neutral point secondary side earth resistance R _nOn voltage,

 _s＝- ₂- ₁；

(5.2) obtain stator winding that secondary side calculates admittance Y over the ground:

Y = \frac{{\overset{\cdot}{I}}_{s}}{{\overset{\cdot}{U}}_{s}};

(5.3) obtain converting the ground fault resistance R of primary side _g:

R_{g} = n^{2} \frac{1}{Re (Y)}

, n is the distribution transformer no-load voltage ratio;

(6) computer according to set and the protection of storage with the ground fault resistance value of the high setting value of ground fault resistance and low setting value and above-mentioned measuring and calculating relatively:

When being lower than the high setting value of earth resistance of protecting setting, the ground fault resistance value of above-mentioned measuring and calculating sends alarm signal;

When being lower than the low setting value of earth resistance that protection sets, the ground fault resistance value of above-mentioned measuring and calculating sends trip signal.

2. the Fault Locating Method of generator unit stator winding single-phase earthing is characterized in that it contains following steps successively:

(1) sets generator three-phase winding-to-earth capacity and be respectively C _a, C _b, C _c, the value that the generator neutral point earth resistance is converted primary side is n ²R _n, n is the distribution transformer no-load voltage ratio;

(2) winding of generator neutral point and distribution transformer primary side disconnects, and injects to the distribution transformer secondary side to add the 20Hz power supply, records distribution transformer is converted secondary side under 20Hz excitatory impedance R by the zero load and the short circuit experiment of distribution transformer _m', X _m', short-circuit impedance R _k, X _k, their value is deposited in computer;

(3) the establishing piezoelectric transformer is converted following each parameter value of secondary side and is under 20Hz:

The leakage impedance R of a winding ₁', X ₁': R ₁'=R _k/ 2, X ₁'=X _k/ 2,

The leakage impedance R of secondary winding ₂, X ₂: R ₂=R _k/ 2, X ₂=X _k/ 2,

R ₁', X ₁', R ₂, X ₂Value deposit computer in;

(4) generator neutral point connects with the winding of distribution transformer primary side, injects the 20Hz power supply that adds to the secondary side of distribution transformer;

(5) computer records the voltage and current of secondary side by the voltage transformer summation current transformer, is computing cycle with 0.1 second again, promptly is fundamental frequency with 10Hz, extracts second harmonic 20Hz voltage  and electric current with fourier algorithm Component;

(6) based on transformer T type equivalent electric circuit, computer is tried to achieve the ground fault resistance value R that converts primary side _g, its step is:

(6.1) computer is according to the above-mentioned R that obtains _m', X _m', R ₂, X ₂, And calculate in the transformer T type equivalent electric circuit with following formula and to flow through R ₁'+jX ₁' and leave the electric current of node

Convert the generator capacitance to earth-jX of secondary side _CThe voltage  at ' two ends _s:

{\overset{\cdot}{I}}_{s} = \overset{\cdot}{I} - {\overset{\cdot}{I}}_{m},

For flowing through R _m'+jX _m' electric current, leave above-mentioned node,

{\overset{\cdot}{I}}_{m} = \frac{\overset{\cdot}{U} - {\overset{\cdot}{U}}_{2}}{R_{m}^{'} + j X_{m}^{'}},

 ₂Be R ₂+ jX ₂On voltage, point to above-mentioned node,

 is neutral point secondary side earth resistance R _nOn voltage,

 _s＝- ₂- ₁；

(6.2) obtain stator winding that secondary side calculates admittance Y over the ground:

Y = \frac{{\overset{\cdot}{I}}_{s}}{{\overset{\cdot}{U}}_{s}};

(6.3) obtain converting the ground fault resistance R of primary side _g:

R_{g} = n^{2} \frac{1}{Re (Y)},

N is the distribution transformer no-load voltage ratio;

(7) the fault phase of judgement generator, it comprises following steps successively:

(7.1) computer records generator machine end three phase-to-ground voltages by the generator terminal voltage instrument transformer, uses fourier algorithm extractor end three fundamental voltage  relatively again _Ag,  _Bg,  _Cg

(7.2) computer extracts neutral point zero-sequence fundamental voltage  with fourier algorithm again by generator neutral point voltage measuring transformer generator residual voltage ₀

(7.3) calculate and store generator three phase winding first-harmonic electromotive force

{\overset{\cdot}{E}}_{a} = {\overset{\cdot}{U}}_{ag} - {\overset{\cdot}{U}}_{0},

{\overset{\cdot}{E}}_{b} = {\overset{\cdot}{U}}_{bg} - {\overset{\cdot}{U}}_{0},

{\overset{\cdot}{E}}_{c} = {\overset{\cdot}{U}}_{cg} - {\overset{\cdot}{U}}_{0};

(7.4) relatively |  ₀| with U _Set: if |  ₀|＞U _Set, then have the stator winding single phase ground fault to take place, wherein: U _SetSetting value for zero-sequence fundamental voltage stator ground fault protection voltage; If |  ₀|＞U _Set, and R _gBe low to moderate the corresponding protection action takes place, then earth fault occurs near the generator neutral point;

(7.5) size of comparison generator machine end three phase-to-ground voltages is the principle failure judgement phase of fault phase according to one of first-harmonic effective value minimum mutually;

(8) the ground fault resistance value R that utilizes step (6) to obtain _gCalculate the abort situation α (fault point accounts for a percentage that is in series total number of turns to the number of turn of neutral point) of fault phase:

Fault is made as a phase mutually, when the three-phase electromotive force of generator windings and direct-to-ground capacitance are asymmetric,

α = - \frac{jω C_{a} {\overset{\cdot}{E}}_{a} + jω C_{b} {\overset{\cdot}{E}}_{b} + jω C_{c} {\overset{\cdot}{E}}_{c} + {\overset{\cdot}{U}}_{0} (\frac{1}{n^{2} R_{n}} + \frac{1}{R_{g}} + jω C_{Σ})}{\frac{{\overset{\cdot}{E}}_{a}}{R_{g}}};

When the three-phase electromotive force of generator windings and direct-to-ground capacitance symmetry,

α = - \frac{{\overset{\cdot}{U}}_{0} (\frac{1}{n^{2} R_{n}} + \frac{1}{R_{g}} + jω C_{Σ})}{\frac{{\overset{\cdot}{E}}_{a}}{R_{g}}}

Wherein: ω=2 π f, f mains frequency; C _∑=C _a+ C _b+ C _c