交流电流监测用电压传感器 技术领域 TECHNICAL FIELD
本发明涉及电力系统在线电流或用电设备的工作电流监测装置的传感器,具 体地说是一种交流电流监测用电压传感器。 The present invention relates to a sensor of a power system on-line current or a working current monitoring device of a power-consuming device, and in particular, it is a voltage sensor for AC current monitoring.
背景技术 Background technique
目前对电力系统或用电设备的工作电流的监测主要是通过电流互感器来进 行的, 常用的电流互感器的结构由一次主回路导电板、二次电感线圈及环形铁芯 构成, 通过电磁感应, 将主回路的大电流转化为二次线圈上的小电流进行测量。 传统的测量方法是在二次线圈上直接串联电流表, 但随着科技的发展,逐渐采用 数字化运算处理。而数字运算的采样信号为电压信号, 因此首先要对二次线圈上 的模拟电压信号作 A/D转换, 由于电流互感器二次输出的电压信号较低, 经放大 后干扰信号也会同时放大, 又会出现较大误差, 影响测量精度, 特别是放大过程 中抗干扰能力差, 同时上述结构的电流互感器对大电流测量也较困难,又无法实 现与主回路隔离进行测量。 At present, the monitoring of the working current of power systems or electrical equipment is mainly performed by current transformers. The structure of commonly used current transformers consists of a primary main circuit conductive plate, a secondary inductance coil and a toroidal core. , The large current of the main circuit is converted into a small current on the secondary coil for measurement. The traditional measurement method is to directly connect the ammeter in series with the secondary coil, but with the development of science and technology, digital arithmetic processing is gradually adopted. The digitally calculated sampling signal is a voltage signal. Therefore, the analog voltage signal on the secondary coil must be A / D converted first. Because the voltage signal of the secondary output of the current transformer is low, the amplified interference signal will also be amplified at the same time. However, a large error will occur, affecting the measurement accuracy, especially the poor anti-interference ability during the amplification process. At the same time, the current transformer with the above structure is also difficult to measure large currents, and it is impossible to measure the circuit from the main circuit.
根据传统的电磁理论, 电流和磁感应强度函数是多解的, 这一点从磁滞回线 中可见, 因而二次电感线圈所得到的感应电压也是多解的,无法用来作为测量信 号。而采用二次电感线圈的感生电压作为釆样信号,则上述问题又是不可避免的。 According to the traditional electromagnetic theory, the current and the magnetic induction intensity function are multiple solutions, which can be seen from the hysteresis loop. Therefore, the induced voltage obtained by the secondary inductance coil is also multiple solutions and cannot be used as a measurement signal. When the induced voltage of the secondary inductance coil is used as the sample signal, the above problems are unavoidable.
但是,传统的电磁理论在分析二次电磁线圈电压时忽略了磁介质中涡流的作 用, 它所得出的磁滞回线也是通过静态测量的, 因此不能真实反应互相之间的动 态关系。事实上, 二次电磁线圈上的感应电压除了实际测量得到的电流所对应的 那部分感应电势外,还包括磁介质中的涡流在二次电感线圈中的感应电势, 反应 到磁滞回线上来,横座标对应的电流值应为磁介质中的涡流与一次主回路导电体 中电流的叠加, 从以下更详细的分析中可知, 上述叠加电流与磁感应强度之间的 关系是呈线性的, 并且,这一论点通过现代科技手段所提供的在线动态测量得到 证实。 However, the traditional electromagnetic theory ignores the role of eddy currents in the magnetic medium when analyzing the voltage of the secondary electromagnetic coil. The hysteresis loops obtained from it are also measured statically, so they cannot truly reflect the dynamic relationship between them. In fact, the induced voltage on the secondary electromagnetic coil includes the induced potential of the eddy current in the magnetic medium in the secondary inductance coil in addition to the part of the induced potential corresponding to the actual measured current, which is reflected on the hysteresis loop. The current value corresponding to the abscissa should be the superposition of the eddy current in the magnetic medium and the current in the primary circuit conductor. As can be seen from the more detailed analysis below, the relationship between the superimposed current and the magnetic induction intensity is linear, and This argument is confirmed by online dynamic measurements provided by modern technology.
发明内容 Summary of the Invention
本发明要解决的是现有电流互感器由于自身结构及取样信号的限制,在利用 电流互感器实现模数转换 (A/D) 时存在一系列技术难题而限制了测量准确性的
问题, 提供一种交流电流监测用电压传感器, 它是基于上述分析结果, 将交流电 流直接转换成电压信号,直接经电阻分压就可作 A/D转换成数字信号供数字运算 使用, 由于传感器直接能转换成足够大的电压信号,所以不会受到幅射式传导干 扰, 抗干扰能力极强, 测量范围也是够宽, 又能与主回路隔离测量, 而且传感器 可随意脱离或靠近主回路,这给随时测量电流提供了方便条件。解决上述问题釆 用的技术方案是: 交流电流监测用电压传感器, 包括一次主回路导电体、 二次线 圈和铁芯, 三者通过绝缘紧固件定位,所述主回路电流方向与所述铁芯截面相垂 直,所述铁芯为开放式, 二次电感线圈输出电压经桥式整流及电容滤波后输出直 流电压供测试用。 What the present invention is to solve is that due to the limitations of the existing current transformer and its sampling signal, there are a series of technical difficulties when using the current transformer to achieve analog-to-digital conversion (A / D), which limits the measurement accuracy. A voltage sensor for AC current monitoring is provided, which is based on the above analysis results, and converts AC current directly into a voltage signal, which can be directly converted into digital signals by A / D for digital operation. It can be directly converted into a sufficiently large voltage signal, so it will not be subject to radiated conduction interference, strong anti-interference ability, wide measurement range, and isolated measurement from the main circuit, and the sensor can be freely detached from or close to the main circuit. This provides convenient conditions for measuring current at any time. The technical solution used to solve the above problems is: A voltage sensor for AC current monitoring, which includes a primary main circuit conductor, a secondary coil, and an iron core. The three are positioned by insulating fasteners, and the main circuit current direction and the iron are The core cross section is perpendicular, the iron core is open, and the output voltage of the secondary inductor coil is bridge-rectified and capacitor-filtered to output a DC voltage for testing.
空心线圈作为二次线圈, 主回路为一次回路, 当二者位置固定后,一次主回 路电流产生的磁通与二次线圈交链的磁链 Ψ 21正比于 L,比例系数为 M21称为互感 系数, 有下式成立:The hollow coil is used as the secondary coil, and the main circuit is the primary circuit. After the positions of the two are fixed, the magnetic flux generated by the primary circuit current and the flux linkage of the secondary coil Ψ 21 are proportional to L, and the proportionality factor is M 21. The mutual inductance coefficient is as follows:
一次主回路电流为交流时, 在二次线圈中产生的感生电势 U2, 满足下式: When the primary main circuit current is AC, the induced potential U 2 generated in the secondary coil satisfies the following formula:
U2=- ά Ψ2ΐ =-M21 di! ( 2- dt dt U 2 =-ά Ψ2ΐ = -M 21 di! (2 -dt dt
由于 ^空心线圈, 空气的磁导率可视为常数等于真空磁导率, 故 M21为常数, 这就是用空心线圈测量一次回路的电流的原理。但是由于是空心线圈, 与一次主 回路交链的磁链非常弱, 所以 U2值非常小, 直接测量 U2产生很大困难。 Due to the hollow coil, the magnetic permeability of air can be regarded as a constant equal to the vacuum permeability, so M 21 is a constant. This is the principle of measuring the current of the primary circuit with the hollow coil. However, because it is an air-core coil, the magnetic flux interlinked with the primary circuit is very weak, so the value of U 2 is very small, and it is very difficult to directly measure U 2 .
一次主回路与二次线圈之间采用硅钢片叠压而成的闭合磁路交链时,由于铁 芯的磁导率是变量必须克服铁芯需要的激磁电流的影响,才能不考虑变化的磁导 率的影响, 所以要求二次回路阻抗非常小, 这时二次电流 12与二次线圈匝数 N2 乘积为 N2I2, 当 N2I2远大于铁芯激磁电流时, 那么铁芯激磁电流就可忽略, 因此 有下式成立: When the primary magnetic circuit and the secondary coil are laminated with a closed magnetic circuit using silicon steel sheets, the magnetic permeability of the iron core is a variable. The influence of the exciting current required by the iron core must be overcome to change the magnetic field Effect conductivity, it requires a very small impedance of the secondary circuit, then the secondary current coil 12 and the secondary product of the number of turns N 2 N 2 I 2, N 2 I 2 when the exciting current is much larger than the core, then The core excitation current can be ignored, so the following formula holds:
NJ^ N2I2 (3)NJ ^ N 2 I 2 (3)
^是一次主回路匝数, !^是忽略铁芯激磁电流后的一次主回路电流。 公式 (3) 就是电流互感器的工作原理。 同样由于二次线圈给出的是电流信号, 又要求二次 回路阻抗必须非常小, 因此能取出的电压信号也是非常小的,很难满足模数转换 要求的技术条件。 ^ Is the number of turns of the main circuit at a time,! ^ Is the primary circuit current after ignoring the core magnetizing current. Equation (3) is the working principle of the current transformer. Also, because the secondary coil gives a current signal and the secondary loop impedance must be very small, the voltage signal that can be taken out is also very small, which is difficult to meet the technical requirements for analog-to-digital conversion.
如果将二次^圈绕在用硅钢片叠压而成的一段铁芯上,铁芯长度应稍大于
二次线圈长度, 也可采用等截面的槽型铁芯, 将二次线圈绕在槽底的铁芯上, 将 二次线圈包好绝缘, 测量时使一次主回路导体贴紧二次线圈并使位置保持不变, 由于有铁芯存在使一次主回路与二次线圈之间交链磁链增大几百倍,这样一次主 回路交流电流在二次线圈中产生的感生电势就比空心线圈增大几百倍。只要铁芯 磁导率是常数, 又能保证一次主回路与二次线圈的位置不变, 那么一次主回路与 二次线圈的互感系数 M21就会是常数, 公式 (1 ) 及公式 (2) 仍成立。 If the second ^ turn is wound on a section of iron core laminated with silicon steel sheet, the core length should be slightly larger than For the length of the secondary coil, a slot-shaped iron core with an equal cross-section can also be used. The secondary coil is wound on the core at the bottom of the slot. The secondary coil is wrapped and insulated. Keep the position unchanged, because the presence of the iron core increases the interlinking magnetic flux between the primary circuit and the secondary coil several hundred times, so that the induced potential generated by the primary circuit AC current in the secondary coil is hollow The coils increase hundreds of times. As long as the core magnetic permeability is constant and the position of the primary and secondary coils is constant, the mutual inductance M 21 of the primary and secondary coils will be constant. Formula (1) and formula (2) ) Still valid.
本发明的实质性技术进步在于找到了保证铁芯磁导率在激磁电流变化非常 大的范围内仍能保持为常数的方法。一次主回路电流作为产生磁势的激磁电流又 是被测电流, I lmSin , 代入公式 (2) 得
The substantial technical progress of the present invention is to find a method to ensure that the magnetic permeability of the iron core can be kept constant within a very large range of exciting current change. The primary loop current is used as the exciting current that generates the magnetic potential and is the measured current. I lmSin, which is substituted into formula (2) to get
=M21 ω Im Sin ( ω ί- π /2 ) (4) 公式 (4) 就是本发明电流电压传感器的测试原理, 从公式 (4) 知道, ¾ 与一次主回路电流的相角差为 90度( π /2)。本发明找到了一种测量交流电流的 新方法, 这种测量方法具有明显优点, 一是测量装置可与被测电流回路相隔离, 并可在被测回路工作状态下将测量装置进入测量位置进行测量,不用断开回路又 可移动测量装置。二是将被测电流直接转换为高电压信号经电阻分压后可用 A/D 模块转换成数字直接进行显示、计算, 程序控制或通讯。而且无须考虑干扰及温 度影响产生的误差。 三是测量范围宽, 并可直接测量主回路短路电流值。 = M 21 ω Im Sin (ω ί- π / 2) (4) Formula (4) is the testing principle of the current-voltage sensor of the present invention. It is known from formula (4) that the phase angle difference between ¾ and the primary main circuit current is 90 Degrees (π / 2). The invention finds a new method for measuring AC current. This method has obvious advantages. First, the measurement device can be isolated from the current circuit under test, and the measurement device can be entered into the measurement position under the working state of the circuit under test. Measure without moving the loop and move the measuring device. The second is to directly convert the measured current into a high-voltage signal, which can be converted to digital by the A / D module after being divided by a resistor for direct display, calculation, program control or communication. And there is no need to consider the errors caused by interference and temperature effects. Third, the measurement range is wide, and the short circuit current value of the main circuit can be directly measured.
当被测回路出现几万安培的特大短路电流时,将 u2经桥式整流后给存储电容 允电将峰值电压转换成存储电容的允电电压可保存一段时间,这样就有充分时间 经 A/D转换成数字信号了。被测电流超过几千安后,非闭合回路的铁芯的磁感应 强度仍会出现饱和: 但由于 U2超前于 L90度(π /2), 因此 U2在 I,电流过零处达 到峰值 Um, 故此 Um值不会因铁芯饱和而改变线性关系, 将 t=0代入公式 (4), 由于 sin ( ω ί+ π /2) =1得: When the circuit under test has a very large short-circuit current of tens of thousands of amperes, U 2 is bridge-rectified to the storage capacitor and allowed to convert the peak voltage into the storage capacitor's allowed voltage for a period of time. / D is converted into a digital signal. After the measured current exceeds several thousand amperes, the magnetic induction strength of the non-closed loop iron core will still saturate: However, because U 2 is ahead of L90 degrees (π / 2), U 2 reaches the peak Um at I and the current crosses zero. Therefore, the Um value will not change the linear relationship due to the saturation of the core. Substituting t = 0 into the formula (4), since sin (ω ί + π / 2) = 1 is:
Um=M21 ω Im (5) (5) 公式 (5) 说明一次回路被测电流峰值与二次经圈感生电压峰值成正比, 因 此二次线圈峰值电压值始终与一次主回路被测电流峰值成线性关系,与铁芯是否 出现饱和无关。 公式 (5) 就是测量特大短路电流的原理, 所以本发明提供一种 测量特大电流的新方法。那就是将被测电流作为二次线圈的非闭合磁路的铁芯的
激磁电流,使二次线圈产生感生电势, 二次线圈感生电势的峰值正比于被测电流 的峰值, 比例系数为被测电流的角频率与被测电流对二次线圈的互感系数的乘 积。 这样就将被测电流信号成功的转换为电压信号, 而且是线性关系。 Um = M 21 ω Im (5) (5) Formula (5) shows that the peak value of the measured current of the primary circuit is proportional to the peak value of the induced voltage of the secondary warp loop, so the peak voltage value of the secondary coil is always the same as the measured current of the primary circuit. The peaks are linear and have nothing to do with whether the core is saturated or not. The formula (5) is the principle of measuring a very large short-circuit current, so the present invention provides a new method for measuring a very large current. That is the core of the non-closed magnetic circuit that uses the measured current as the secondary coil. The exciting current causes the secondary coil to generate an induced potential. The peak value of the secondary coil induced potential is proportional to the peak value of the measured current. The proportionality factor is the product of the angular frequency of the measured current and the mutual inductance of the measured current to the secondary coil. . In this way, the measured current signal is successfully converted into a voltage signal, and the relationship is linear.
为了验证公式(5 )中的被测电流峰值变化范围多大能保证互感系数 M21是常 数, 可用试验直接测量。 为试验方便起见, 在二次线圈外层绕 N匝导线形成一次 线圈, 一次线圈电流 作为激磁电流代替被测主回路电流, I^NLn与一次线圈 串联一个小电阻1?, 电阻上的电压 Ur, 则 Iin=Ur/R, 用双踪示被器分别将 Ι,η及 U2显示在荧光屏上或经接口送给打印机打印出来,当 U2波形为正弦波形而且无畸 变发生时, 说明 M21为常数。 逐渐增大 Ln, U2波形开始出现畸变, 开始出现畸变 点以前的电流峰值 .Im对应的 M21都是常数。 从 U2畸变点开始铁芯接近饱和磁导 M 值下降, 但是从波形图上仍可看作 Um与 Im仍是线性关系, 甚至于 Um还稍有上 升。 说明公式 (5 ) 在几十安培到几千安培或几万安培都成立。 由实验证明这种 新发明的电流电压传感器的测量原理是成立的,测量范围是非常大的, 并且准确 性较好。 由于铁芯起始磁导率较小, 维持 M21的线性关系的被测电流值的下限范 围随减小而下降。如果被测电流值下限仍不够,还可以增加一次线圈的匝数使下 限进一步扩大范围。 In order to verify how large the range of the peak value of the measured current in formula (5) can ensure that the mutual inductance M 21 is constant, it can be directly measured by experiments. For the convenience of the test, a primary coil is formed by winding N turns of wires on the outer layer of the secondary coil. The primary coil current is used as the exciting current instead of the main circuit current to be measured. I ^ NLn is connected in series with the primary coil with a small resistor 1 ?, and the voltage on the resistor Ur Then, I in = Ur / R. Use a dual tracer to display I, η, and U 2 on the fluorescent screen or send them to the printer for printing through the interface. When the U 2 waveform is sinusoidal and no distortion occurs, explain M 21 is constant. Gradually increasing Ln, the U 2 waveform starts to appear distorted, and the current peak before the distortion point starts to appear. The M 21 corresponding to Im is constant. Starting from the U 2 distortion point, the M value of the core decreases toward saturation saturation, but from the waveform diagram, it can still be seen that Um and Im are still linear, and even Um has slightly increased. It is shown that the formula (5) holds from tens of amps to thousands of amps or tens of thousands of amps. The measurement principle of this newly invented current-voltage sensor is proved by experiments, the measurement range is very large, and the accuracy is good. Because the initial magnetic permeability of the iron core is small, the lower limit range of the measured current value that maintains the linear relationship of M 21 decreases as it decreases. If the lower limit of the measured current value is still insufficient, the number of turns of the primary coil can be increased to further expand the lower limit.
上面实验说明硅钢片软磁材料的磁导率在激磁电流的起始磁导率以上和达 到饱和前的范围内是不变的常数,上述实验是可信的,本发明电流电压传感器也 是实用的。 The above experiment shows that the magnetic permeability of the soft magnetic material of the silicon steel sheet is a constant constant above the initial permeability of the exciting current and before reaching saturation. The above experiment is credible, and the current and voltage sensor of the present invention is also practical .
附图说明 BRIEF DESCRIPTION OF THE DRAWINGS
下面结合附图和实施例对本发明作进一步说明。 The invention is further described below with reference to the drawings and embodiments.
图 1是本发明测量较大电流时实施例的结构示意图。 FIG. 1 is a schematic structural diagram of an embodiment when a large current is measured by the present invention.
图 2是本发明测量较小电流时实施例的结构示意图。 FIG. 2 is a schematic structural diagram of an embodiment when a small current is measured by the present invention.
图 3是本发明测量很小电流时实施例的结构示意图。 FIG. 3 is a schematic structural diagram of an embodiment when a small current is measured by the present invention.
图 4是本发明槽型铁芯的结构示意图。 具体实施方式 FIG. 4 is a schematic structural diagram of a grooved iron core according to the present invention. detailed description
附图所示, 1一二次线圈, 2—二次线圈框, 3—铁芯, 4——次主回路导电 板, 5—绝缘紧固件, 6—桥式整流件, 7—滤波储能电容, 8一一次主回路导线。
当一次主回路被测电流较大时采用图 1的电流电压传感器,用绝缘紧固件将As shown in the figure, 1-secondary coil, 2—secondary coil frame, 3—iron core, 4—secondary main circuit conductive plate, 5—insulating fasteners, 6—bridge rectifier, 7—filter storage Capacitance, 8 once the main circuit wire. When the measured current of the main circuit is relatively large, the current and voltage sensor shown in Figure 1 is used.
—次主回、 铁芯、 二次电感固定, 保证位置和角度不变, 使主回路电流方向与铁 芯截面相垂直, 一次主回路导电体采用导电板, 铁芯采用直型铁芯, 二次电感线 圈输出电压经桥整流为直流,用电容 c滤波储能输出为直流电压, 为保证输出的 直流电容等于二次电感线圈输出的峰值电压, 负载电阻比二次电感线圈内阻大—The secondary main loop, iron core and secondary inductance are fixed to ensure the same position and angle, so that the current direction of the main circuit is perpendicular to the cross section of the core. The primary circuit conductor uses a conductive plate, and the core uses a straight core. The output voltage of the secondary inductor is rectified to DC by the bridge, and the capacitor c is used to filter the energy storage output as a DC voltage. To ensure that the output DC capacitance is equal to the peak voltage of the secondary inductor, the load resistance is greater than the internal resistance of the secondary inductor
2000倍以上。 More than 2000 times.
当一次主回路被测电流较小时采用附图 2型式的电流电压传感器,与图 1实 施例不同之处在于所述铁芯采用槽型等截面铁芯。 参照图 4, 槽型铁芯在底槽上 是对接的, 这样就能插入线圈框内了。每片正反对调接缝不在一个位置上, 又能 压紧铁芯。 - 参照图 3, 当一次主回路被测电流很小, 主回路采用圆导线 8, 可以将一次 主回路绕在包好绝缘的二次线圈外面,包好绝缘也就将绕二匝的一次主回路固定 在二次线圈上了。
When the measured current of the main circuit is small, the current and voltage sensor of the type shown in FIG. 2 is used, which is different from the embodiment of FIG. 1 in that the core uses a slot-shaped equal-section core. Referring to FIG. 4, the slotted iron core is butted on the bottom slot, so that it can be inserted into the coil frame. Each piece is not in the same position as the joint, and it can compact the iron core. -Referring to Figure 3, when the measured current of the primary circuit is small and the main circuit uses round wire 8, the primary circuit can be wrapped around the insulated secondary coil. The circuit is fixed on the secondary coil.