WO2021253705A1 - 基于电流合成和精密磁势转换的高精度零序电流传感器 - Google Patents

基于电流合成和精密磁势转换的高精度零序电流传感器 Download PDF

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WO2021253705A1
WO2021253705A1 PCT/CN2020/125415 CN2020125415W WO2021253705A1 WO 2021253705 A1 WO2021253705 A1 WO 2021253705A1 CN 2020125415 W CN2020125415 W CN 2020125415W WO 2021253705 A1 WO2021253705 A1 WO 2021253705A1
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precision
zero
lpct
current
coil
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PCT/CN2020/125415
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English (en)
French (fr)
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丁永生
李自清
宋云翔
李力
冯娟
邢峻
施闻博
陆军
姜富修
杜丽
胡永建
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上海置信智能电气有限公司
国网电力科学研究院有限公司
上海置信电气非晶有限公司
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Publication of WO2021253705A1 publication Critical patent/WO2021253705A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
    • G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
    • G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
    • G01R15/181—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers using coils without a magnetic core, e.g. Rogowski coils

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  • the invention belongs to the technical field of current transformers, and relates to a high-precision zero-sequence current sensor based on current synthesis and precise magnetic potential conversion.
  • the traditional zero-sequence current transformer adopts a racetrack coil design, and the three-phase wires pass through a zero-sequence current transformer together.
  • the zero sequence current is detected through electromagnetic induction mutual inductance.
  • the magnetic permeability of the transformer core cannot be evenly distributed.
  • the second is the winding process of the transformer coil, the coil cannot be completely uniformly wound on the core;
  • the third is the asymmetry of the magnetic field caused by the arrangement of the primary conductors, which affects the magnetic balance characteristics of the zero-sequence current transformer.
  • a 600/5 zero-sequence current transformer will induce a zero-sequence current when the primary balance current reaches 400A. Therefore, the traditional racetrack zero-sequence current design method is not suitable for zero-sequence current sensors that require high-precision measurement.
  • Electromagnetic zero-sequence current transformers have the following shortcomings: First, there is magnetic saturation when the primary current is 400A, which makes it impossible to collect zero-sequence currents above 400A; second, the core material and magnetic circuit are not uniform, and the magnetic permeability is low (special performance In the magnetic saturation zone) and the current conductors are not uniformly distributed in the inner cavity of the iron core, it is easy to produce magnetic errors. For the magnetic potential superposition type zero sequence current sensor, the distribution of the three-phase current conductors in the zero sequence core is very scattered, and the core leakage is serious, which will introduce considerable magnetic errors.
  • the third is the inability to accurately collect low-current (200mA-1A) zero-sequence signals, which reduces the accuracy of single-phase grounding fault identification, which easily leads to the transfer of single-phase grounding faults to phase-to-phase faults, causing fire and other vicious accidents.
  • the purpose of the present invention is to provide a high-precision zero-sequence current sensor based on current synthesis and precise magnetic potential conversion to solve the problem of low accuracy in the prior art.
  • a high-precision zero-sequence current sensor based on current synthesis and precise magnetic potential conversion including an LPCT coil, a precision current transformer, and a high-precision sampling resistor R 0 ;
  • the LPCT coil includes LPCT coil A, LPCT coil B, and LPCT coil C
  • the LPCT coil A, LPCT coil B, and LPCT coil C are respectively connected to a precision current transformer;
  • the precision current transformer is connected in parallel with a high-precision sampling resistor R 0 ;
  • the LPCT coil A, LPCT coil B and LPCT coil C are respectively connected in parallel There are resistance R A , resistance R B and resistance R C.
  • the precision current transformer includes a primary side and a secondary side; the secondary side is connected in parallel with a high-precision sampling resistor R 0 .
  • the precision of the precision current transformer is 0.1 grade; the precision of the high precision sampling resistor R 0 is 0.1%.
  • LPCT coil A LPCT coil A
  • LPCT coil B LPCT coil C
  • the primary winding of the precision current transformer is 10 turns; the secondary winding is 2000 turns.
  • LPCT coil A, LPCT coil B and LPCT coil C are respectively connected to the A-phase, B-phase and C-phase wires.
  • the LPCT coil A, the LPCT coil B and the LPCT coil C are respectively connected to the precision current transformer to obtain the secondary zero-sequence current, and the method of directly collecting small signals through the high-precision sampling resistor R 0 satisfies the situation that the primary zero-sequence current is small
  • the lower measurement accuracy ensures the load capacity of the current sensor and the miniaturization of the sensor.
  • Fig. 1 is a circuit diagram of an embodiment of the present invention.
  • a high-precision zero-sequence current sensor based on current synthesis and precise magnetic potential conversion including LPCT coil, precision current transformer and high-precision sampling resistor R 0 ;
  • LPCT coil includes LPCT coil A, LPCT coil B And LPCT coil C;
  • LPCT coil A, LPCT coil B and LPCT coil C are respectively connected to precision current transformers; precision current transformers are connected in parallel with high-precision sampling resistor R 0 ;
  • LPCT coil A, LPCT coil B and LPCT coil C are respectively connected in parallel with resistors R A , resistance R B and resistance R C.
  • the precision current transformer includes a primary side and a secondary side; the secondary side is connected in parallel with a high-precision sampling resistor R 0 .
  • the LPCT coil A, LPCT coil B and LPCT coil C are respectively connected to the A-phase, B-phase and C-phase wires.
  • phase-sequence current and zero-sequence current are collected by independent coils.
  • CT current transformer
  • the present invention does not adopt the design of the zero sequence racetrack coil, and adopts the current synthesis method to connect the three-phase LPCT coil end to end in parallel to obtain the secondary zero sequence current.
  • the method of directly collecting small signals through the high-precision sampling resistor R 0 meets the requirements of the primary zero
  • the measurement accuracy when the sequence current is small ensures the load capacity of the current sensor and the miniaturization of the sensor.
  • the obtained secondary zero-sequence current is connected in series with a precise current transformer and a parallel high-precision sampling resistor to obtain a high-precision small voltage signal.
  • the three-phase current synthesis zero-sequence current method greatly reduces the volume of the sensor and avoids the influence of asymmetric magnetic fields in principle.
  • phase sequence current and the zero sequence current of the present invention share the primary current collection coil, which avoids the interference of the space magnetic field and the errors introduced by magnetic leakage, greatly improves the collection accuracy, greatly reduces the volume of the current transformer, and is not only easy to install, Moreover, it can be directly poured into the switch pole to integrate with the switch; the zero sequence output loop and the phase sequence output loop are isolated by a current transformer, which is directly connected to the neutral line of the secondary side of the phase sequence current transformer. While the series connection of resistors affects the phase sequence accuracy, it also solves the disadvantages of zero-sequence impedance matching and the requirement to configure high-power resistors.
  • the invention improves the sampling accuracy of the tiny primary zero-sequence current (200mA-1A), extends the low-temperature characteristics (-40°C) downwards, and ensures the accuracy stability in the range of -40°C to +70°C, and -40°C
  • the error change within the range of ⁇ +70°C does not exceed 0.5%; through compound anti-interference measures such as single-point grounding and ferromagnetic shielding cover, the error change of the sensor signal under the influence of the zero sequence current by the magnetic field does not exceed 1/4, and the solution
  • the accuracy error of the zero sequence signal output caused by the magnetic effect is eliminated.
  • Test method During the test, use a primary current conductor of appropriate length to penetrate through the product's AP1 current bus hole, and then pass it through the product's CP1 current bus hole to pass the rated primary thermal current; use AC millivolts with an error of not more than 5%
  • the meter measures the zero-sequence voltage output of the product, and the ratio of the measured value to the zero-sequence rated secondary voltage should not exceed 1/4 of the zero-sequence current sensor protection limit coefficient (1/4 of the 10P level error limit of 10% (2.5%) )).

Abstract

一种基于电流合成的高精度零序电流传感器，包括LPCT线圈、精密电流互感器和高精度取样电阻R 0；LPCT线圈包括LPCT线圈A、LPCT线圈B和LPCT线圈C；LPCT线圈A、LPCT线圈B和LPCT线圈C分别连接精密电流互感器；精密电流互感器并联高精度取样电阻R 0；LPCT线圈A、LPCT线圈B和LPCT线圈C分别并联有电阻R A、电阻R B和电阻R C。高精度零序电流传感器将LPCT线圈首尾并接获得二次零序电流，通过高精度取样电阻直接采集小信号的方法满足了一次零序电流较小情况下的测量精度，保证了电流传感器的带载能力和传感器小型化。

Description

基于电流合成和精密磁势转换的高精度零序电流传感器 技术领域
本发明属于电流互感器技术领域，涉及基于电流合成和精密磁势转换的高精度零序电流传感器。
背景技术
传统零序电流互感器采用跑道型线圈设计，三相导线一起穿过一个零序电流互感器。当三相电流不平衡时，根据基尔霍夫电流定律，通过电磁感应互感检测出零序电流。但在实际情况中，有三种情况会对零序电流互感器产生误差，一是互感器铁心磁导率不可能均匀分布，这个跟铁心的烧制工艺(炉内温度、保护气体均匀等)有关；二是互感器线圈绕制工艺，线圈不可能完全均匀的绕制在铁心上；三是一次导体的排列位置导致的磁场不对称，影响了零序电流互感器的磁平衡特性。经过实际测试，受磁场不对称影响，一个600/5的零序电流互感器，在一次平衡电流达到400A时，即会互感出零序电流。因此，传统的跑道式零序电流设计方法对于高精度测量要求的零序电流传感器是不合适的。
电磁式零序电流互感器有以下缺点：一是在一次电流400A时有磁饱和现象，造成400A以上的零序电流无法采集；二是铁心材料和磁路不均匀，磁导率低(特别表现在磁饱和区)以及电流导体在铁心内腔分布不均匀，易产生磁误差。对于磁势叠加型零序电流传感器，三相电流导体在零序铁心中的分布很分散，铁心漏磁严重，会引入相 当大的磁误差。三是不能准确采集小电流(200mA-1A)零序信号，降低了单相接地故障识别的准确率，易导致单相接地故障向相间故障转移，引发火灾等恶性事故。亟需开展高精度电流传感器的技术研究，提升故障识别率和供电可靠性，保障电网安全运行。
发明内容
针对现有技术的不足，本发明的目的在于提供一种基于电流合成和精密磁势转换的高精度零序电流传感器，以解决现有技术中存在的准确率不高的问题。
为解决上述技术问题，本发明采用的技术方案为：
一种基于电流合成和精密磁势转换的高精度零序电流传感器，包括LPCT线圈、精密电流互感器和高精度取样电阻R 0；所述LPCT线圈包括LPCT线圈A、LPCT线圈B和LPCT线圈C；所述LPCT线圈A、LPCT线圈B和LPCT线圈C分别连接精密电流互感器；所述精密电流互感器并联高精度取样电阻R 0；所述LPCT线圈A、LPCT线圈B和LPCT线圈C分别并联有电阻R A、电阻R B和电阻R C。
进一步的，所述精密电流互感器包括原边和副边；所述副边并联高精度取样电阻R 0。
进一步的，所述精密电流互感器的精度为0.1级；所述高精度取样电阻R 0的精度为0.1％。
进一步的，所述LPCT线圈A、LPCT线圈B和LPCT线圈C首尾并接。
进一步的，所述精密电流互感器的一次绕线为10匝；二次绕线 为2000匝。
进一步的，所述LPCT线圈A、LPCT线圈B和LPCT线圈C分别连接A相、B相和C相导线。
与现有技术相比，本发明所达到的有益效果是：
本发明通过LPCT线圈A、LPCT线圈B和LPCT线圈C分别连接精密电流互感器从而获得二次零序电流，通过高精度取样电阻R 0直接采集小信号的方法满足了一次零序电流较小情况下的测量精度，保证了电流传感器的带载能力和传感器小型化。
附图说明
图1为本发明实施例的电路图。
具体实施方式
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。
如图1所示，一种基于电流合成和精密磁势转换的高精度零序电流传感器，包括LPCT线圈、精密电流互感器和高精度取样电阻R 0；LPCT线圈包括LPCT线圈A、LPCT线圈B和LPCT线圈C；LPCT线圈A、LPCT线圈B和LPCT线圈C分别连接精密电流互感器；精密电流互感器并联高精度取样电阻R 0；LPCT线圈A、LPCT线圈B和LPCT线圈C分别并联有电阻R A、电阻R B和电阻R C。精密电流互感器包括原边和副边；副边并联高精度取样电阻R 0。LPCT线圈A、LPCT线圈B和LPCT线圈C分别连接A相、B相和C相导线。
目前主要采用跑道式、圆形等三相穿心电磁式零序电流互感器采集零序电流，相序电流和零序电流均有独立的线圈进行采集。零序电流保护具体应用可在三相线路上各装一个电流互感器(CT)，或让三相导线一起穿过一零序CT，利用这些CT来检测三相的电流矢量和，即零序电流Io，IA+IB+IC＝Io，当线路上所接的三相负荷完全平衡时(无接地故障，且不考虑线路、电器设备的泄漏电流)，Io＝0；当线路上所接的三相负荷不平衡，则Io＝IN，此时的零序电流为不平衡电流IN；当某一相发生接地故障时，必然产生一个单相接地故障电流Id，此时检测到的零序电流I O＝IN+Id，是三相不平衡电流与单相接地电流的矢量和。
本发明不采用零序跑道型线圈的设计，采用电流合成方法，将三相LPCT线圈首尾并接获得二次零序电流，通过高精度取样电阻R 0直接采集小信号的方法是满足了一次零序电流较小情况下的测量精度，保证了电流传感器的带载能力和传感器小型化。
本发明通过精密磁势转换，将获得的二次零序电流，通过串联精密电流互感器和并联高精度取样电阻，得到高精度的电压小信号。三相电流合成零序电流的方式，极大的减小了传感器体积，并从原理上避免了不对称磁场的影响。
根据本发明设计的电流传感器，假定零序电流传感器的额定变比为20A/0.2V；精密电流互感器的一次绕线10匝，二次绕线2000匝，额定变比K 0：K 0＝2000/10＝200；额定一次零序电流I 01：I 01＝20A；额定二次零序电流I 02：I 02＝20A/200＝100mA；额定二次零序转换电 压U 02：U 02＝0.2V；可得零序高精度取样电阻R 0：R 0＝0.2V/100Ma＝2Ω；零序电流传感器的精度要求为1级，选择零序取样电阻为0.1％高精度的精密电阻。
本发明的相序电流和零序电流共用一次电流采集线圈，避免了空间磁场的干扰及漏磁等引入的误差，采集精度大为提高，极大地缩小了电流互感器的体积，不仅易安装，而且还可直接浇注到开关极柱中，与开关成融为一体；零序输出回路和相序输出回路用电流互感器隔离，在解决了直接在相序电流互感器二次侧中性线上串接电阻而影响相序精度的问题的同时，还解决了零序阻抗匹配及要求配置大功率电阻的弊端。
本发明提升了微小一次零序电流(200mA-1A)的采样精度，且向下延展了低温特性(-40℃)，保证了-40℃～+70℃范围内的精度稳定性，-40℃～+70℃范围内误差变化不超过0.5％；通过单点接地和铁磁性屏蔽罩等复合抗干扰措施，将零序电流受磁场影响下的传感信号误差变化量不超过1/4，解决了零序信号输出因磁效应导致的精度误差。
试验方法：试验时用适当长度的一次电流导体从产品的AP1电流母线孔穿入，再从产品的CP1电流母线孔穿出，通以额定一次热电流；用误差不大于5％的交流毫伏表测量产品零序电压输出，测得值与零序额定二次电压之比应不超过零序电流传感器保护限值系数的1/4(10P级误差限值10％的1/4(2.5％))。
额定一次电流 实际二次零序输出 额定二次零序输出 磁误差
600A 1.5mV 200mV 0.75％
以上显示和描述了本发明的基本原理和主要特征和本发明的优点。本行业的技术人员应该了解，本发明不受上述实施例的限制，上述实施例和说明书中描述的只是说明本发明的原理，在不脱离本发明精神和范围的前提下，本发明还会有各种变化和改进，这些变化和改进都落入要求保护的本发明范围内。本发明要求保护范围由所附的权利要求书及其等效物界定。

Claims (6)

  1. 一种基于电流合成和精密磁势转换的高精度零序电流传感器，其特征在于，包括LPCT线圈、精密电流互感器和高精度取样电阻R 0；所述LPCT线圈包括LPCT线圈A、LPCT线圈B和LPCT线圈C；所述LPCT线圈A、LPCT线圈B和LPCT线圈C分别连接精密电流互感器；所述精密电流互感器并联高精度取样电阻R 0；所述LPCT线圈A、LPCT线圈B和LPCT线圈C分别并联有电阻R A、电阻R B和电阻R C。
  2. 根据权利要求1所述的一种基于电流合成和精密磁势转换的高精度零序电流传感器，其特征在于，所述精密电流互感器包括原边和副边；所述副边并联高精度取样电阻R 0。
  3. 根据权利要求2所述的一种基于电流合成和精密磁势转换的高精度零序电流传感器，其特征在于，所述精密电流互感器的精度为0.1级；所述高精度取样电阻R 0的精度为0.1％。
  4. 根据权利要求1所述的一种基于电流合成和精密磁势转换的高精度零序电流传感器，其特征在于，所述LPCT线圈A、LPCT线圈B和LPCT线圈C首尾并接。
  5. 根据权利要求1所述的一种基于电流合成和精密磁势转换的高精度零序电流传感器，其特征在于，所述精密电流互感器的一次绕线为10匝；二次绕线为2000匝。
  6. 根据权利要求1所述的一种基于电流合成和精密磁势转换的高精度零序电流传感器，其特征在于，所述LPCT线圈A、LPCT线圈B和LPCT线圈C分别连接A相、B相和C相导线。
PCT/CN2020/125415 2020-06-18 2020-10-30 基于电流合成和精密磁势转换的高精度零序电流传感器 WO2021253705A1 (zh)

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