CN110146780B - 中性点不接地柔性配电网***铁磁谐振判别方法 - Google Patents

中性点不接地柔性配电网***铁磁谐振判别方法 Download PDF

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CN110146780B
CN110146780B CN201910336859.2A CN201910336859A CN110146780B CN 110146780 B CN110146780 B CN 110146780B CN 201910336859 A CN201910336859 A CN 201910336859A CN 110146780 B CN110146780 B CN 110146780B
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吴楠
史明明
袁宇波
周建华
陈久林
黄成�
孙健
杨雄
焦昊
祁承磊
周涛
张刘冬
曾飞
方鑫
陈雯嘉
袁晓冬
陈兵
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State Grid Corp of China SGCC
State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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State Grid Jiangsu Electric Power Co Ltd
Electric Power Research Institute of State Grid Jiangsu Electric Power Co Ltd
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    • G01MEASURING; TESTING
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Abstract

本发明公开了一种中性点不接地柔性配电网***铁磁谐振判别方法,检测正常运行和故障后母线零序电压、三相电压的相量值,母线电压频率f0,通过判断基频谐振、倍频谐振、基频谐振后,再计算j相电压的相对幅值误差
Figure DDA0002038270570000011
相电压相对相位误差
Figure DDA0002038270570000012
若0<εampi<ξ且0<εphi<ξ,ξ为误差极限,则判断发生铁磁谐振,否则为非铁磁谐振。本发明对中性点不接地***的铁磁谐振进行判别,保证铁磁谐振故障判别高准确性。

Description

中性点不接地柔性配电网***铁磁谐振判别方法
技术领域
本发明涉及一种中性点不接地柔性配电网***铁磁谐振判别方法,属于电力***配电自动化技术领域。
背景技术
目前,铁磁谐振过电压是内部过电压的常见形式,它是由于电压互感器(PT)铁心饱和后,与电网对地电容形成的非线性谐振。当前柔性电力电子技术成为改造配电网的一个重要趋势,基于晶闸管投切电容器(TSC)等技术改造的柔性配电网***,通过改变线路对地电容来增大配电网功率因数,减少电网损耗。柔性配电网***改变了传统配电网的线路参数,通常在单相接地故障恢复或电气设备突然投切时,发生铁磁谐振,此时,相电压可能升高至额定值的3-5倍,易击穿电网绝缘薄弱点,PT较大的电流易引起熔丝熔断甚至PT炸裂,影响电网的安全稳定运行。因此,快速判别柔性配电网***铁磁谐振故障至关重要。
铁磁谐振可分为分频谐振、基频谐振和倍频谐振。分频谐振、基频谐振在实际中较常见。倍频谐振和分频谐振时,零序电压呈现倍频和分频特性,较易识别。而基频谐振时,零序电压为工频,且基频谐振时会有一相或多相电压降低,和单相接地故障特征相似,两者较难直接区分。因此,如何区分铁磁谐振和单相接地故障,成为电网故障判断领域需要解决的问题。
发明内容
目的:为了克服现有技术中存在的不足,本发明提供一种中性点不接地柔性配电网***铁磁谐振判别方法,保证铁磁谐振故障判别的准确性。
技术方案:为解决上述技术问题,本发明采用的技术方案为:
一种中性点不接地柔性配电网***铁磁谐振判别方法,包括如下步骤,
步骤1、检测故障后母线零序电压
Figure BDA0002038270550000021
U0
Figure BDA0002038270550000022
的有效值,辨识出
Figure BDA0002038270550000023
的频率为f0,若f0<50Hz则判断发生分频谐振,若f0>50Hz则判断发生倍频谐振;
步骤2、若f0=50Hz,且故障后母线零序电压有效值U0超过相电压有效值,则判断发生基频谐振,或者若f0=50Hz,且故障后三相电压有效值同时升高,则判断发生基频谐振;
步骤3、若不是步骤1或步骤2中判断情况,则检测故障前正常运行时三相稳态电压相量值
Figure BDA0002038270550000024
EA、EB、EC分别为
Figure BDA0002038270550000025
Figure BDA0002038270550000026
的电压幅值;
步骤4、检测故障后三相稳态电压、母线零序电压的相量值
Figure BDA0002038270550000027
Figure BDA0002038270550000028
UA、UB、UC、U0分别为
Figure BDA0002038270550000029
的电压幅值;以某相为基准相,计算该相的起始相位基准值ph1i和母线起始相位基准值ph2i,其中i取A或B或C,公式如下:
Figure BDA00020382705500000210
Figure BDA00020382705500000211
其中,i取A或B或C,Ei为正常运行时i相电压幅值,U′i取基准相故障时电压幅值、U′0取故障时母线零序电压的电压幅值;
步骤5、将基准相故障时电压幅值Ui与基准相起始相位基准值ph1i组合成基准相电压相量基准计算值
Figure BDA0002038270550000031
将故障时母线零序电压的电压幅值U0与母线起始相位基准值ph2i组合成母线零序电压相量基准计算值
Figure BDA0002038270550000032
公式如下:
Figure BDA0002038270550000033
Figure BDA0002038270550000034
步骤6、求除基准相外的j相相量计算值
Figure BDA0002038270550000035
j取A或B或C,公式如下:
Figure BDA0002038270550000036
其中,
Figure BDA0002038270550000037
为正常运行时j相稳态电压相量值;
步骤7、计算j相电压的相对幅值误差εampj、相电压相对相位误差εphj,公式如下:
Figure BDA0002038270550000038
其中,i=j,
Figure BDA0002038270550000039
为故障后i相三相稳态电压的电压幅值;
Figure BDA00020382705500000310
其中,
Figure BDA00020382705500000311
为j相相量计算值
Figure BDA00020382705500000312
的相位角,
Figure BDA00020382705500000313
为基准相电压相量基准计算值
Figure BDA00020382705500000314
的相位角,
Figure BDA00020382705500000315
为故障后j相稳态电压相量值的相位角,
Figure BDA00020382705500000316
为故障后基准相稳态电压相量值的相位角;
步骤8、若0<εampi<ξ且0<εphi<ξ,ξ为误差极限,则判断发生铁磁谐振,否则为非铁磁谐振。
作为优选方案,如果在不具备零序电压互感器条件下,
Figure BDA00020382705500000317
通过计算公式
Figure BDA00020382705500000318
计算得到,其中,
Figure BDA00020382705500000319
分别为故障后A、B、C三相的相电压测量值,且
Figure BDA0002038270550000041
为同一基准相位下测量值。
作为优选方案,所述母线零序电压为柔性配电网***母线处的电压。
作为优选方案,所述ξ≤20%
作为优选方案,所述ξ=20%。
作为优选方案,所述ξ=10%。
有益效果:本发明提供的中性点不接地柔性配电网***铁磁谐振判别方法,对中性点不接地***的铁磁谐振进行判别,保证铁磁谐振故障判别高准确性。
附图说明
图1为本发明的判别方法流程示意图;
图2为柔性配电网***II段母线处录波波形图;
图3为以A相相量为起始相位的相量图。
具体实施方式
下面结合附图对本发明作更进一步的说明,显然,所描述实施例仅仅是本发明的一部分实施例,而不是全部的实施例。基于本发明的实施例,本领域普通技术人员在没有做出创造性劳动的前提下所得到的所有其它实施例,都属于本发明所保护的范围。
一种中性点不接地柔性配电网***铁磁谐振判别方法,包括以下步骤:
步骤1、检测故障后母线零序电压
Figure BDA0002038270550000042
U0
Figure BDA0002038270550000043
的有效值,辨识出
Figure BDA0002038270550000051
的频率为f0,若f0<50Hz则判断发生分频谐振,若f0>50Hz则判断发生倍频谐振。
如果在具备零序电压互感器条件下,
Figure BDA0002038270550000052
可通过零序电压互感器直接采集得到;
如果在不具备零序电压互感器条件下,
Figure BDA0002038270550000053
可通过计算公式
Figure BDA0002038270550000054
计算得到,其中,
Figure BDA0002038270550000055
分别为故障后A、B、C三相的相电压测量值,且
Figure BDA0002038270550000056
为同一基准相位下测量值。
全篇涉及的电压为整体柔性配电网***母线处的电压。
步骤2、若f0=50Hz,且故障后母线零序电压有效值U0超过相电压有效值,则判断发生基频谐振,或者若f0=50Hz,且故障后三相电压有效值同时升高,则判断发生基频谐振;
步骤3、若不是步骤1或步骤2中判断情况,则检测故障前正常运行时三相稳态电压相量值
Figure BDA0002038270550000057
EA、EB、EC分别为
Figure BDA0002038270550000058
Figure BDA0002038270550000059
的电压幅值;
步骤4、检测故障后三相稳态电压、母线零序电压的相量值
Figure BDA00020382705500000510
Figure BDA00020382705500000511
UA、UB、UC、U0分别为
Figure BDA00020382705500000512
的电压幅值;以某相为基准相,计算该相的起始相位基准值ph1i和母线起始相位基准值ph2i,其中i取A或B或C,公式如下:
Figure BDA00020382705500000513
Figure BDA00020382705500000514
其中,i取A或B或C,Ei为正常运行时i相电压幅值,U′i取基准相故障时电压幅值、U′0取故障时母线零序电压的电压幅值。
步骤5、将基准相故障时电压幅值Ui与基准相起始相位基准值ph1i组合成基准相电压相量基准计算值
Figure BDA0002038270550000061
将故障时母线零序电压的电压幅值U0与母线起始相位基准值ph2i组合成母线零序电压相量基准计算值
Figure BDA0002038270550000062
公式如下:
Figure BDA0002038270550000063
Figure BDA0002038270550000064
步骤6、求除基准相外的j相相量计算值
Figure BDA0002038270550000065
j取A或B或C,公式如下:
Figure BDA0002038270550000066
其中,
Figure BDA0002038270550000067
为正常运行时j相稳态电压相量值。
步骤7、计算j相电压的相对幅值误差εampj、相电压相对相位误差εphj,公式如下:
Figure BDA0002038270550000068
其中,i=j,
Figure BDA0002038270550000069
为故障后i相三相稳态电压的电压幅值。
Figure BDA00020382705500000610
其中,
Figure BDA00020382705500000611
为j相相量计算值
Figure BDA00020382705500000612
的相位角,
Figure BDA00020382705500000613
为基准相电压相量基准计算值
Figure BDA00020382705500000614
的相位角,
Figure BDA00020382705500000615
为故障后j相稳态电压相量值的相位角,
Figure BDA00020382705500000616
为故障后基准相稳态电压相量值的相位角。
步骤8、若0<εampi<ξ且0<εphi<ξ,ξ为误差极限,则判断发生铁磁谐振,否则为非铁磁谐振。
步骤5中ξ可根据实际现场情况进行整定,一般取值为20%及以下。
实施例:
如图2所示,II段母线处的测量波形,现在图中取T1、T2两个时刻,其中T1时刻为正常运行状态,并获取T1时刻母线电压、A、B、C三相电压相量,如表1所示:
Figure BDA0002038270550000072
表1。
T2时刻为柔性配电网发生故障时,故障现象为站内II段母线C相压变熔丝损毁、避雷器C相炸裂。获取T2时刻母线电压、A、B、C三相电压相量,如表2所示:
Figure BDA0002038270550000073
表2。
由以上波形及相量表格,无法直接判断发生单相接地或铁磁谐振故障。
现以计算B相的相对幅值误差εampB、相对相位误差εphB为例,具体如下:
步骤1:故障前正常运行时,检测到A、B、C三相稳态电压相量值分别为:
Figure BDA0002038270550000071
步骤2:故障后,检测到A、B、C三相稳态电压、母线零序电压的有效值分别为:UA=45.05V、UB=65.60V、UC=69.72V、U0=14.59V,A、B、C三相稳态电压的相量值分别为:
Figure BDA0002038270550000081
Figure BDA0002038270550000082
步骤3:数据分析时,由于T1、T2时刻的A相检测电压的相位都是0°,所以用A相相量计算起始相位基准值,起始相位基准值包括:A相起始相位基准值,母线起始相位基准值。
步骤4:如图3所示,EA=59.44V、U′0=U0=14.59V、U′A=UA=45.05V,EA
Figure BDA0002038270550000083
的电压有效值,U′0为母线零序电压计算值,U′A为A相电压计算值,利用余弦定理,分别求A相起始相位基准值ph1,母线起始相位基准值ph2
Figure BDA0002038270550000084
Figure BDA0002038270550000085
步骤5:将故障时A相稳态电压有效值UA、母线零序电压有效值U0与A相起始相位基准值ph1,母线起始相位基准值ph2组成A相电压相量基准计算值
Figure BDA0002038270550000086
母线零序电压相量基准计算值
Figure BDA0002038270550000087
根据公式5求得B相相量计算值
Figure BDA0002038270550000088
Figure BDA0002038270550000089
Figure BDA00020382705500000810
Figure BDA00020382705500000811
步骤6:将
Figure BDA00020382705500000812
的幅值代入公式6,求出B相电压的相对幅值误差εampB
Figure BDA0002038270550000091
步骤7:将
Figure BDA0002038270550000092
各相量中的相位角代入公式7,求出B相电压相对相位误差εphB
Figure BDA0002038270550000093
步骤8:由公式(6)、(7),求得εampB=12.88%,εphB=7.79%,取ξ=20%,均小于ξ,故判断故障为铁磁谐振。
同理,可求C相相量计算值
Figure BDA0002038270550000094
再计算C相电压的相对幅值误差εampC、C相电压相对相位误差εphC
Figure BDA0002038270550000095
求得εampC=18.83%,εphC=9.81%,取ξ=20%,均小于ξ,故判断故障为铁磁谐振。
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,在不脱离本发明原理的前提下,还可以做出若干改进和润饰,这些改进和润饰也应视为本发明的保护范围。

Claims (6)

1.一种中性点不接地柔性配电网***铁磁谐振判别方法,其特征在于:包括如下步骤,
步骤1、检测故障后母线零序电压
Figure FDA0003022616800000011
U0
Figure FDA0003022616800000012
的有效值,辨识出
Figure FDA0003022616800000013
的频率为f0,若f0<50Hz则判断发生分频谐振,若f0>50Hz则判断发生倍频谐振;
步骤2、若f0=50Hz,且故障后母线零序电压有效值U0超过相电压有效值,则判断发生基频谐振,或者若f0=50Hz,且故障后三相电压有效值同时升高,则判断发生基频谐振;
步骤3、若不是步骤1或步骤2中判断情况,则检测故障前正常运行时三相稳态电压相量值
Figure FDA0003022616800000014
EA、EB、EC分别为
Figure FDA0003022616800000015
Figure FDA0003022616800000016
的电压幅值;
步骤4、检测故障后三相稳态电压、母线零序电压的相量值
Figure FDA0003022616800000017
Figure FDA0003022616800000018
UA、UB、UC、U0分别为
Figure FDA0003022616800000019
的电压幅值;以某相为基准相,计算该相的起始相位基准值ph1i′和母线起始相位基准值ph2i′,其中i′取A或B或C,公式如下:
Figure FDA00030226168000000110
Figure FDA00030226168000000111
其中,i′取A或B或C,Ei′为正常运行时i′相电压幅值,Ui′′取基准相故障时电压幅值、U0′取故障时母线零序电压的电压幅值;
步骤5、将基准相故障时电压幅值Ui′与基准相起始相位基准值ph1i′组合成基准相电压相量基准计算值
Figure FDA00030226168000000112
将故障时母线零序电压的电压幅值U0与母线起始相位基准值ph2i′组合成母线零序电压相量基准计算值
Figure FDA00030226168000000113
公式如下:
Figure FDA0003022616800000021
Figure FDA0003022616800000022
步骤6、求除基准相外的j相相量计算值
Figure FDA0003022616800000023
当i′=A,j取B或C,当i′=B,j取A或C,当i′=C,j取A或B,公式如下:
Figure FDA0003022616800000024
其中,
Figure FDA0003022616800000025
为正常运行时j相稳态电压相量值;
步骤7、计算j相电压的相对幅值误差εampj、相电压相对相位误差εphj,公式如下:
Figure FDA0003022616800000026
其中,i=j,
Figure FDA0003022616800000027
为故障后i相三相稳态电压的电压幅值;
Figure FDA0003022616800000028
其中,
Figure FDA0003022616800000029
为j相相量计算值
Figure FDA00030226168000000210
的相位角,
Figure FDA00030226168000000211
为基准相电压相量基准计算值
Figure FDA00030226168000000212
的相位角,
Figure FDA00030226168000000213
为故障后j相稳态电压相量值的相位角,
Figure FDA00030226168000000214
为故障后基准相稳态电压相量值的相位角;
步骤8、若0<εampi<ξ且0<εphi<ξ,ξ为误差极限,则判断发生铁磁谐振,否则为非铁磁谐振。
2.根据权利要求1所述的中性点不接地柔性配电网***铁磁谐振判别方法,其特征在于:如果在不具备零序电压互感器条件下,
Figure FDA00030226168000000215
通过计算公式
Figure FDA00030226168000000216
计算得到,其中,
Figure FDA00030226168000000217
分别为故障后A、B、C三相的相电压测量值,且
Figure FDA00030226168000000218
为同一基准相位下测量值。
3.根据权利要求1所述的中性点不接地柔性配电网***铁磁谐振判别方法,其特征在于:所述母线零序电压为柔性配电网***母线处的电压。
4.根据权利要求1所述的中性点不接地柔性配电网***铁磁谐振判别方法,其特征在于:所述ξ≤20%
5.根据权利要求4所述的中性点不接地柔性配电网***铁磁谐振判别方法,其特征在于:所述ξ=20%。
6.根据权利要求4所述的中性点不接地柔性配电网***铁磁谐振判别方法,其特征在于:所述ξ=10%。
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