English:
[0001] As is known in the art, the plane of polarization of polarized light rotates in a magnetic field when the light is propagated in a direction parallel to the direction of the magnetic field. This phenomenon is utilized by magneto- optical current transducers (MOCT), to optically measure the current flowing through a conductor. MOCTs are commonly used in electricity metering systems, and in particular, in power distribution sub-stations. For example, U.S. Patent No. 4,578,639 describes a metering system employing an MOCT, and is hereby incorporated by reference in it's entirety. Generally, the MOCT includes an optical source (typically an LED). The light is passed through a collimating lens and a polarizer. The polarized light then travels through an optical path comprising a dielectric material, around a current carrying conductor. The light source is received at a detector, which is commonly a silicon diode. The received signal may then be conditioned and amplified for output.
[0002] Though MOCTs are well accepted and have proven to be very reliable, some drawbacks persist. For example, some MOCT based meters tend to exhibit erroneous non-zero energy meter registration during power outages. Thus, there is a need in the art for an MOCT that does not exhibit non-zero energy registration during power outages.
[0005] Figure 2 is a function block schematic of the optics module for an MOTC according to the present invention.
[0006] Figure 3 is a function block schematic of the Low Input Cutout module according to the present invention.
[0007] With reference now to Fig. 1 , a function block schematic diagram of an sensor system according to the present invention is shown. The sensor system includes an optics module 10, a digital printed circuit board (PCB) 12, a low input cutout (LIC) module 14, and amplifiers 16 for each phase. The amplifiers 16 output to meters (not shown) which receive, store, output and/or display the data.
[0008] With reference now to Fig. 2, the optics component 10 is shown. As discussed above, a polarized light source (LED 18) travels through an optical path (rotator 20) around a conductor 22 to be measured. The light is then received at a sensor (PIN diode 24) where the rotation of the polarized light is be measured. According to one exemplary embodiment, the polarized light is measured as a 60 Hz modulation of the input light intensity. The signal from PIN diode 24 is output to a transimpedance amplifier 26. The PIN diode converts light into electrons which creates a flow of current. The transimpedance amplifier converts the current to a voltage. The signal from the transimpedence amplifier 26 is output to a compensator 28. The intensity of the light is controlled by a feedback control system. The compensator keeps the light intensity loop stable, the output of which drives LED 18. The signal from the transimpedance amplifier 26 is also output to an amplifier 30. According to one embodiment, the amplifier 30 outputs a 2 volt RMS signal at rated current (of the power line to be monitored).
[0009] According to one embodiment, the pin diode 24, transimpedance amplifier 26, compensator 28, LED 18 and amplifier 30 each physically reside on a phase card 32. Meters incorporating an MOCT typically measure three phase power distribution, and thus three separate phase cards 32, performing three separate optical measurements (one on each phase), are used.
[0010] The signal from amplifier 30 from each phase card 32 is output to digital PCB 12. The digital PCB 12 outputs to the LIC module 14 the phase A, B, and C low level voltage signals that are proportional to the respective phase current. It should be appreciated, however, that digital PCB 12 functions merely as a pass-through or router of the signal from the optical module 10. Thus, the digital PCB 12 does not appreciably modify the signal. According to another embodiment, the output signal from optical module 10 may be directly connected to the LIC module 14.
[0011] With reference now to Fig. 3, the LIC module 14 includes three identical and independent circuits that continuously process the phase A, B, and C signals from optical module 10 (either received directly from the optical module 10 or through the digital PCB 12). Each LIC phase circuit outputs to an individual phase amplifier 16 which amplifies the signal and transmits it to the energy sensor or meter.
[0012] Each phase circuit in the LIC 14 includes a narrow band pass active filter 34. According to one embodiment, the filter 34 is set at 60 Hz with a Q equal to 12, which provides a ± 5 Hz bandwidth (for power line 22 frequencies of 60Hz). The band pass active filter may be adjusted to match the power line 22 frequency and may have Q values from 1 to 25. The output of the filter 34 drives an RMS to DC converter 36, which further filters the total RMS input into a DC value. The output of the RMS to DC converter 36 drives a comparator 38. The comparator 38 switches its output at a DC signal level corresponding to a minimum threshold value. According to one embodiment of the present invention, the threshold value is the DC signal corresponding to 0.5% of the rated phase current of power line 22. According to another embodiment the threshold value is the DC signal corresponding to 1 % of the rated phase current of the power line 22. According to yet another embodiment the threshold value is the DC signal corresponding to 0.25% of the rated phase current of the power line 22.
[0013] The output of the comparator 38 controls a switch 40. At levels below the threshold value (in the first embodiment, 0.5% of the rated current), the switch 40 grounds the output to the power amplifier 16. At levels above the threshold value, the comparator 38 causes switch 40 to pass the phase voltage from the optical component 10 (as received directly or through the digital PCB 12) directly to the power amplifier 16 unmodified. Thus, at current levels above the threshold value, the LIC module 14 passes through the signal unmodified to the amplifiers 16. However, if current levels on the power line 22 drop below 0.5 % of the rated current (indicating a power outage), the LIC module 14 ensures that zero output current is output from the power amplifier 16 to the meters. In this manner, erroneous energy meter registration is eliminated.
[0014] The wideband white noise present during a zero current condition at the input to the LIC module 14 has an approximate value of 5 mV RMS from DC for a 1 kHz 1000 A rated MOCT system. The narrowband filters 18 of the LIC module 14 reduce this noise level to approximately 0.5 mV RMS. If the rated current signal has an amplitude of 2 volts, for the exemplary embodiment wherein the threshold is 0.5% of rated current) the 0.5% rated current signal has an amplitude of 10 mV RMS. Therefore, the LIC module filtering yields an RMS signal to noise ratio of 20 and provides reliable switching at this level of input.
[0015] The present invention may be used in newly assembled MOCT based meters, or may take the form of a field upgrade kit for existing MOCT hardware, in particular, the ABB MOCT 21001. According to this embodiment, the LIC module 14 may be in the form of a printed circuit board and mounted into the 21001 chassis directly above the preexisting digital PCB 12 using 1 inch standoffs supplied with a kit and the existing screw holes in the digital PCB 12. Cables supplied with the kit connect between the digital PCB, the LIC, and the power amplifier that produces the rated 1 A RMS current. Kit installation must be done while the 2100I chassis is de-energized.
[0016] According to one embodiment, the LIC PCB receives its power from the Digital PCB and requires approximately 150 mW of power from each of the "+" and "-" 15 V power supplies. Each power source has considerable head room to accommodate this increase in power and does not add a significant heat load to the interior of the 21001 chassis.
[0018] As will be appreciated by one of ordinary skill in the art, various functions in the present invention may be embodied as or take the form of a computer readable medium having computer-readable instructions stored thereon which, when executed by a processor, carry out the operations of the present inventions as previously described. The computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the user-interface program instruction for use by or in connection with the instruction execution system, apparatus, or device and may by way of example but without limitation, be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium or other suitable medium upon which the program is printed. More specific examples (a non-exhaustive list) of the computer-readable medium would include: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a transmission media such as those supporting the Internet or an intranet, or a magnetic storage device. Computer program code or instructions for carrying out operations of the present invention may be written in any suitable programming language provided it allows achieving the previously described technical results.

中文:
[0001]如本领域公知的,当光沿着平行于磁场的方向传播时,偏振光的偏振面在磁场中旋转。磁光电流换能器(MOCT)利用这一现象来光学地测量流经导体的电流。MOCT常常用于电计量系统,且尤其是用于配电分站。例如,美国专利号4,578,639描述了一种使用MOCT的计量系统,在此将其整体合并以作参考。通常,MOCT包括光源(典型为LED)。该光穿过准直透镜和偏振器。然后偏振光传输通过包含围绕着携带电流的导体的介电材料的光学路径。该光源在常常是硅二极管的探测器处接收。然后所接收的信号可以被调节和放大来输出。
[0002]虽然MOCT被很好地接受且已经证明非常可靠,但存在些缺点。例如,一些基于MOCT的仪表倾向于在电源断电时展示错误的非零能量的仪表对准。因此,本领域需要一种在电源断电时不展示非零能量对准的MOCT。
[0005]图2是用于根据本发明的MOTC的光学模块的功能块示意。
[0006]图3是根据本发明的低输入断流器(cutout)模块的功能块示意。
[0007]参照图1,示出了根据本发明的传感器系统的功能块示意图。该传感器系统包括光学模块10,数字印刷电路板(PCB)12,低输入断流器(low input cutout,LIC)模块14和用于每个相位的放大器16。放大器16输出至接收、存储、输出和/或显示数据的仪表(未示出)。
[0008]现参照图2,示出了光学组件10。如上所讨论的,偏振光源(LED18)传输经过围绕待测导体22的光学路径(旋转器22)。然后在传感器(PIN二极管24)处接收光,且在该传感器处测量偏振光的旋转。根据一个示范性实施例,偏振光按60Hz的输入光强度调制度量。来自PIN二极管24的信号被输出至转阻(transimpedance)放大器26。PIN二极管将光转换为建立电流的电子。转阻放大器将电流转换为电压。来自转阻放大器26的信号被输出至补偿器28。光的强度由反馈控制系统控制。补偿器保持光强度环稳定,且其输出驱动LED18。来自转阻放大器26的信号也被输出至放大器30。根据一个实施例,放大器30在(待监测的电源线的)额定电流输出2伏的RMS信号。
[0009]根据一个实施例,PIN二极管24、转阻放大器26、补偿器28、LED 18和放大器30的每个物理地驻留在相位卡(phase card)32上。包含MOCT的仪表典型地测量三种相位电源分布,并且因此使用执行三种分离光学测量(每一相位一种)的三种分离相位卡32。
[0010]来自每一相位卡32的放大器30的信号被输出至数字PCB 12。数字PCB 12将与各自相位电流成比例的相位A、B和C的低平电压信号输出至LIC模块14。然而,应理解数字PCB 12仅起作为来自光学模块10的信号的通过器或路由器的功能。因此,数字PCB 12不会明显地改变信号。根据另一实施例,来自光模块10的输出信号可以直接连接至LIC模块14。
[0011]现在参照图3,LIC模块14包括连续地处理来自光学模块10(从光学模块10直接接收或通过数字PCB 12接收)的相位A、B和C信号的三个等同和独立的电路。每个LIC相位电路输出至单独放大器16,该单独相位放大器16放大该信号并将其传送至能量传感器或仪表。
[0012]LIC 14中的每个相位电路包括窄带通有源滤波器34。根据一个实施例,滤波器34设置在60Hz且Q等于12,其(对频率60Hz的电源线22而言)提供±5Hz的带宽。可以调整带通有源滤波器来匹配电源线22的频率且可以具有Q值从1至25。滤波器34的输出驱动RMS-DC转换器36,该RMS-DC转换器36进而将总RMS输入滤波成DC值。RMS-DC转换器36的输出驱动比较器38。比较器38在对应于最小阈值的DC信号水平上切换其输出。根据本发明的一个实施例,阈值是对应于0.5%的电源线22的额定相位电流的DC信号。根据另一个实施例,阈值是对应于1%的电源线22的额定相位电流的DC信号。根据又一个实施例,阈值是对应于0.25%的电源线22的额定相位电流的DC信号。
[0013]比较器38的输出控制开关40。在低于阈值的水平下(在第一实施例,0.5%的额定电流),开关40将至功率放大器16的输出接地。在高于阈值的水平,比较器38使开关40将来自光学组件10(直接接收或通过数字PCB 12接收)的相位电压直接未修改地传递至功率放大器16。因此,在高于阈值的电流水平,LIC模块14将信号未修改地传递至放大器16。然而,如果电源线22上的电流水平降至0.5%的额定电流以下(指示为电源断电)时,LIC模块14确保将零输出电流从功率放大器16输出至仪表。以这样的方式,错误的能量仪表对准被消除了。
[0014]零电流条件期间在LIC模块14的输入呈现的宽带白噪声具有用于1kHz、1000A的额定MOCT系统的来自DC的大约5mV的RMS值。LIC模块14的窄带滤波器18将该噪声水平减小至大约0.5mVRMS。对于示范性实施例,如果额定电流信号具有2伏特的幅值,其中阈值是0.5%的额定电流,则0.5%的额定电流信号具有10mVRMS的幅值。因此,LIC模块的滤波产生具有20的RMS信噪比并在该输入水平提供可靠的切换。
[0015]本发明可以用于新组装的基于MOCT的仪表,或可以采用用于尤其是ABB MOCT2100I的已有MOCT硬件的现场升级包(field upgrade kit)的形式。根据这一实施例,LIC模块14可以按印刷电路板的形式,且使用供应套件(kit)的1英寸支座和数字PCB 12中的已有螺丝孔来将LIC模块14直接安装在先前的数字PCB 12之上的2100I基座内。供应有套件的电缆连接在数字PCB、LIC和产生额定的1A RMS电流的功率放大器之间。套件安装须在2100I基座断电时完成。
[0016]根据一个实施例,LIC PCB从数字PCB处接收其电源,并需要来自每个“+”和“-”15V电源供应的大约150mW的功率。每一电源具有相当大的头部空间来容纳功率的这一增加并且不会向2100I基座的内部增加明显的热负载。
[0018]本领域技术人员应理解,本发明的各种功能可以具体化为或使用具有计算机可读指令存储在其上的计算机可读介质的形式,其中,当由处理器执行指令时,其执行如前描述的本发明的操作。计算机可读介质可以是能够包含、存储、通信、传播或传输用于由指令执行系统、装置或设备使用的或与指令执行系统、装置或设备连接的用户接口程序指令的任意介质,且其示例可以是但不限于:电子的、磁的、光的、电磁的、红外的或半导体系统、装置、设备或传播介质或者程序印在其上的其他适当介质。计算机可读介质的更具体示例(非穷举列表)将包括:便携式计算机盘、硬盘、随机存储器(RAM)、只读存储器(ROM)、可擦除可编程只读存储器(EPROM或闪存)、光纤、便携式压缩只读存储器盘(CD-ROM)、光存储设备、诸如那些支持互联网或局域网的传送介质、或磁存储设备。用于执行本发明操作的计算机程序代码或指令可以以任意适合的编程语言编写,只要其允许实现前面描述的技术结果。