FIELD OF INVENTION
This invention is directed to an apparatus for monitoring power and generating signal. Thus, the present invention relates to power quality monitoring and more particularly to the power quality monitoring which works simultaneously for multiple channels.
RELATED ART
As a result of the widespread use of computers and other microprocessor-based equipment, the quality of power and other environmental conditions at sites having such equipment has become increasingly important. Utility companies deliver electric power to customer sites as an alternating current (AC) voltage through a secondary power distribution system. Various distribution system and environmental factors, however, can cause power line transients, such as spikes, surges, or sags, and can cause blackouts, brownouts, or other distribution system problems that greatly affect the quality of power received by the customer at a site. Electronic equipment, such as computers and other equipment with microprocessors are susceptible to damage and/or a faulty operation as a result of power line transients and other poor power quality conditions. The quality of power is likely to become increasingly important as the utility industry is deregulated and the utility companies compete more aggressively for power users.
One attempt at improving the quality of power at a site has been to install a power conditioner. This solution, however, often provides a false sense of security. Power protection manufacturers typically design power conditioner systems assuming that a site meets the National Electrical Code for safety. Power protection manufacturers also assume that a site has good, solid earth ground and only one grounding path. With substandard grounding, many power conditioners will not provide optimum protection and the resulting impulse let through and high frequency noise will adversely affect system performance. Thus, power conditioners may suffer from the same problems caused by poor power quality. Also some power conditioners do not address all potential power quality problems, such as voltage regulation issues or outages. The typical power conditioner is designed to filter high frequency events only leaving the system vulnerable to low frequency events, such as power factor correction and harmonics.
Another solution is to use power monitoring equipment to monitor the power quality at a site either before installing electronic equipment or after problems occur with the electronic equipment. Conventional power monitoring equipment suffers from numerous drawbacks. Existing power monitoring equipment is overly complex, expensive and typically requires a special setup, depending upon the site. In addition to not being user-friendly, the existing systems are not capable of organizing the data and presenting the data in a useful format. Although existing systems are capable of gathering large amounts of data, these systems are unable to adequately process, save and transmit that data for use in generating power quality reports that facilitate correcting the problems. In these systems, the vast amount of data must often be recorded and sent out for processing and a report is mailed much later.
In addition to systems that generate too much data, some existing systems generate too little data such that a determination cannot be made as to why certain power events might
have occurred. Existing power monitoring equipment also does not have the capability of monitoring multiple channels including extensive monitoring of environmental conditions as well as power conditions and power events. Traditional power monitors are also not set up to do interactive tests (e.g., input and output of a UPS or power conditioner, data gathering of the UPS status log, or a line impedance test for measuring the line resistance). The ability to provide a more comprehensive data gathering for all of the site's conditions has traditionally been lacking.
Accordingly, a system and method is required for monitoring power which can also generate signal. A power monitoring and signal generating system and method is also needed that improves the processing, storage and transfer of data using data compression techniques. A power monitoring and signal generating system and method is also needed that is capable of presenting analyzed data in a format that allows a customer to understand the problem and to attempt to correct that problem. A power monitoring and signal generating system and method is also needed that monitors multiple channels in real time, including environmental condition signals and has the ability to run interactive tests and gather data from remote devices (i.e., UPS system logs).
US patent no 6,598,003 discloses a power and environmental condition monitoring system for monitoring power and environmental conditions at a site. The system comprises at least one analog signal receiver including a plurality of analog signal channels for receiving a plurality of analog measurement signals representing power and environmental conditions, for converting the analog measurement signals into digital signals including digital signal data, and for buffering the digital signal data.
US patent no 7,315,790 discloses a system and method of quantifying voltage anomalies which may be used to quantify low frequency voltage transients such as the type caused by power factor correction (PFC) or similar events. Voltage anomalies include a sub-cycle disturbance in a voltage waveform having a frequency less than 15 kilohertz.
US patent no 6,507,794 provides a system for monitoring power quality events of electrical energy to an energy meter via a service type. The system comprises a memory for storing reference information reflective of different service types, a digital signal processor for measuring characteristics of the electrical energy and a microcontroller for retrieving the reference information from the memory and comparing the measured characteristics to the reference information for the service type to determine the occurrence of power quality events. Their present a storage means comprising an EEPROM In the present invention storage means not only EEPROM but also PC since huge amount of data can be stored & retrieved for future analysis.
US patent no 6,675,071 discloses a method of monitoring variations. The monitoring method is carried out within an electrical energy meter containing means for metering a quantity of electrical energy generated by a supplier and transferred via a power supply line to a load. This method is suitable only for line voltage waveform measurement.
Publication no KR20040038130 discloses a power monitoring system having a position information system receiver to perform a phase angle comparison process and enhance the reliability & the accuracy by using a GPS time synchronization signal.
Publication no KR20030038062 discloses a spectrum analyzer. In the analyzer, a GUI is mounted within a power amplifier for controlling and mounting characteristics of an IMD (intermodulation distortion), to minimize the amount of the IMD and identify a state of a channel by monitoring a final output of a linear amplifier. Further, a coupler is used for extracting partially the power from a power amplifier.
Publication no CN1416197 discloses online monitoring system. The system includes the devices for online monitoring the quality of power supply and at least one server. The devices are allocated at the electrical power system and several consumer distribution networks for real time collection, analytical processing, displaying and transferring the quality of power supply of the power network monitored. In order to analytical process the parameters of the quality of power supply sent by the devices and provide the analyzed result for user browsing, the server through the telephone line and several said devices constitutes the monitoring network. The advanced technique such as double digital signal processing chips (DSP), the double ports RAM, the local FLASH with large capacitance etc. are adopted in the device.
Publication no JP2002199579 detects and estimates abnormality in the quality of power and the causes of failures using a small amount of operation loads and a small memory capacity. In this invention, abnormality is calculated by comparing the actual effective voltage with the minimum and maximum
US publication no 20080215264 is high speed digital transient waveform detection system and method for use in an intelligent device. This system and method detects transients for input voltages in either phase to phase or phase to neutral measurements and permits a user to set threshold levels for detecting transients in input voltages. The system includes a field programmable gate array as a controller for managing transient detection.
US publication no 20070179737 discloses a mobile apparatus and method for monitoring and controlling the detection of stray voltage anomalies. The mobile apparatus is comprises a detection system unit and an imaging system unit. These units provides streaming data of electric field measurements and corresponding video image frames of a particular scene being patrolled and examined for anomalies. Data from both the detection system unit and the imagining system unit are synchronized and provided to a video based graphical user interface (VGUI) to enable an operator of the VGUI with a "moving chart" graphical display of electric field strength overlaid on video image frames of a particular location in the scene at the time of the measurement. This is limited for only voltage anomalies.
US publication no 20060259254 discloses systems and methods related to monitoring of energy usage on a power line. The data collector is preferably capable of (i) receiving data from and transmitting data to the metering device over the power line, (ii) storing
data received from the metering device over the power line, and (iii) receiving data from and transmitting data to a remotely located computer (preferably, a billing computer). This invention comprises electronic microprocessor-controlled digital electricity. Data collector is coupled to the metering device via the power line.
US publication no 6,947,854 is about systems and methods related to monitoring of energy usage on a power line. In a preferred embodiment, this system comprises (a) an electronic microprocessor-controlled digital electricity metering device coupled to the power line and comprising a non-volatile non-battery-powered data-storage device, wherein the metering device is capable of interval metering and of receiving a data request and transmitting data in response to the request over the power line; and (b) a data collector (preferably, a transponder) coupled to the metering device via the power line. The data collector is preferably capable of (i) receiving data from and transmitting data to the metering device over the power line, (ii) storing data received from the metering device over the power line, and (iii) receiving data from and transmitting data to a remotely located computer (preferably, a billing computer). This invention comprises electronic microprocessor-controlled digital electricity. Data collector is coupled to the metering device via the power line.
US publication no 7,342,507 (20060066456) and US patent no 7,006,934 are power quality detection, monitoring, reporting, recording and communication in a revenue accuracy electrical power meter is disclosed. Transient events, sags, swells, harmonic frequencies and symmetrical components are detected in the system. Incoming waveforms are stored to memory. All recorded and computed data is moved to nonvolatile storage via direct memory access transfer in the event that a power quality event jeopardizes the operating power of the meter. In this invention, all recorded and computed data is moved to non-volatile storage.
US publication no 20080215264 discloses a system and a method for the detection and capture, and in particular for an ultra high speed detection and capture, of transients in input voltages by an intelligent electronic device. This system captures only transients in the input voltage.
US publication no 2008228448 and 2007126412 discloses an apparatus and a method for measuring a waveform including ringing. This apparatus includes: a digital filter for removing a large-amplitude changing component from an input signal and for outputting a resultant output signal with a small-amplitude noise component left. This system only measures waveform but not voltage and frequency.
US publication no 20070262799, US2006197697 and publication no JP2008157971 discloses an on-ship signal waveform measurement apparatus for, on multi-channels, measuring signal waveforms at detection points on fixed voltage wiring lines such as internal signals, power source voltages, ground voltages, well voltages, and substrate voltages of a semiconductor large-scale integrated circuit (LSI), and a signal waveform measuring system including the on-ship signal waveform measurement
apparatus. The present invention is a sampling timing signal generator for use in the signal waveform measurement system.
US publication no 20030058970 discloses a method for analyzing a signal. The system measures or gates an incoming waveform at time intervals dictated by a clock signal recovered from the incoming waveform. This system is suitable for only single channel measurement.
Publication no JP2007205837 discloses a waveform measuring device capable of easily determining whether Go occurs or NoGo occurs in measured data at a specific time. This system is suitable for only single channel measurement.
Publication no JP2006349345 discloses a measurement device capable of acquiring the measurement waveform to each acquisition memory based on the being delayed before and after trigger signals without changing the delay time. This system is suitable for only single channel measurement.
US publication no 2005234665 discloses a waveform measuring apparatus that writes measurement data to a memory for waveform data acquisition based on a trigger signal. This system is suitable for only single channel measurement.
Publication no JP2003344455, JP2002040056, JP2003248021 discloses waveform measuring devices. This measurement through these systems is only single channel source. There is no provision of measuring multiple channels simultaneously
Publication no JP2005351658 discloses waveform measuring device equipped with at least one channel of measurement part for outputting the measured waveform of the measurement object, for storing the waveform from the measurement object in a first memory, and for displaying the waveform of the first memory on the display or storing in the memory means. Two memories are being used for the system.
Publication no JP2006133061 discloses waveform measuring device equipped with a waveform storage means for storing information of a time change of an output signal from a measuring probe is equipped with a phenomenon information storage means for storing a discrimination name capable of discriminating the generated phenomenon and a prescribed operation content correlatively with the discrimination name. This system is suitable only for single channel waveform measurement but not for the simultaneous measurement of multiple channels waveform and voltage / frequency.
Publication no JP2000147016 discloses a device which automatically acquires a waveform measured value to store it by using a measuring device with a video display. This system is suitable for only single channel measurement.
US patent no 7,174,258 discloses a device for measuring electrical energy in an electric circuit. The device includes at least one sensor coupled with the electric circuit and operative to sense at least one electrical parameter in the electric circuit and generate at least one analog signal indicative thereof.
US patent no 7,209,804 discloses a system and method for providing remote monitoring of a power device. The system includes a service device with a transceiver circuitry and a computation circuitry. In addition, the service device includes a display circuitry that displays the computed electrical value in conjunction with operational parameters of the power device.
US publication no 20040186670, 20030212512, 20030101008 (6,694,270) and 20030220752 are phasor monitoring systems and apparatuses for use with a distribution system for electricity wherein periodic three phase electricity is distributed in a plurality of circuits.
US publication no 20080093100 discloses a system for power quality monitoring. The system includes first and second controllers coupled together with a communication channel. The first controller provides a first signal to the second controller and the second controller provides a second signal to the first controller in response. The second signal includes information about an electrical load. At least one of the first and second controllers can be integrated with an electrical outlet.
Publication no 3832/CHENP/2006 discloses a method of compressing values of a waveform of a monitored electrical power signal. The method includes of acquiring data representative of periods of the waveform, decomposing the waveform of the power signal into a plurality of components, over a plurality of periods of the waveform compressing the values of at least some of the components over a plurality of periods, individually and storing these values and extent. This invention is restricted to Waveform only.
Publication no 433/CAL/2002 discloses a power monitoring system for a wide region. The region to which electric power is supplied from an electric power supply organization is divided into some areas and electric power is supplied beach of the divided areas as a unit block.
Publication no 2616/DEL/2004 discloses a system for dynamic power management in a distributed architecture system on a chip. The system comprises a means for dynamically defining the feasibility of entering a low power mode of operation, a means for entering or exiting safely from a low power state based on said feasibility, a means for decreasing the power centric communication between various processors, a means for decreasing the power centric communication between various processors and a means for increasing the low power mode time.
Publication no JP1253673 describes a highly accurate high-speed measurement output, by correcting errors based on a data obtained from a high-speed measuring device for measuring an analog input to be measured and a data of a characteristic data memory with an A/D converter.
Publication no KR880000186B provides four input channels of digital data to a counter keeping a running count of the data from the metering devices. A buffer and latch select a running count in response to a chip select signal from a decoder, acting with a microprocessor to provide control signals and input the sample to microprocessor. In the microprocessor, the input sample has a prior sample value, stored in RAM, subtracted from it. The result is added to an interval sum stored in the RAM.
US publication no 20080019068, 20080019067 and 20080125988 are current protection apparatuses and methods that may include programmable current protection characteristics. A current protection apparatus may include a power distribution unit with power distribution outlets, each having a corresponding circuit breaker unit.
US patent no 6,566,891 discloses a measurement system and a method of determining characteristics associated with a waveform that compensates for distortion associated therewith. The system includes a monitoring device that detects distortion in a waveform propagating along the transmission medium. This system is restricted only to waveform.
Publication no WO0040976 discloses a method of monitoring variations carried out within an electrical energy meter containing means therein for metering a quantity of electrical energy generated by a supplier and transferred via a power supply line to a load. The method includes a first step of sensing a line voltage transferred via the power supply line to the load during the energy measurement time interval.
Publication no JP6308167 measures an effective value and the like at every cycle of an input waveform. A signal to be measured is shaped to a rectangular waveform by a shaper circuit and a PLL (phase locked loop) circuit generates a sampling clock having frequency N times of and in sync with that of the rectangular waveform.
Reference is made to an article by L H Sia, et al Al, Meas. Sci. Technol 18, 35-40, 2007. The article describes a digital signal processor (DSP) based waveform generator, which can generate a sine wave, up to 24 kHz, a square wave, up to 5 kHz and a triangular wave, up to 12 kHz. A DSP starter kit with Code Composer Studio has been used in the design of a waveform generator. The waveform generators can also produce periodic arbitrary waveforms and amplitude modulated signals. Two synchronized signals can be obtained by using the waveform generator too. The spectral components of the signals generated are found comparable with a commercially available signal generator. The total harmonic distortion of the sine wave generated is less than 0.6%.
Reference may also be made to an article by Jin-Yi Lin, Master's Thesis, July 03, 2001. The thesis explains design and implementation of a digital signal processor based power quality monitoring device. Several event-triggering methods are studied and implemented
to detect system disturbances. Simulation and test results indicate that the proposed design can meet the requirements for power measurements and transient event recording during steady and transient states. This system is restricted for only event-triggering methods
Reference may also be made to an article by Hung-Rung Chung, Master's Thesis, July 30, 2001. The paper explains design and implementation of a DSP based multi-function monitoring control system, operating for induction motor, intelligent battery charger and residual capacity estimator and uninterrupted power system to develop effectively and complete well.
Reference may also be made to an article by (UK) National Instruments, Laboratory talk, 27 Mar 2001. The article talks that National Instruments has announced its collaboration with Texas Instruments and Spectrum Digital in the development of the new TI C55X power optimization DSP starter kit (DSK), the industry's first DSP design tool to offer designers incorporated test and measurement functionality The new kit incorporates virtual instrumentation- combining National Instruments USB-based measurement hardware with a power monitoring application based on NI Lab view software - to deliver a complete set of power estimation and measurement tools for accurately planning, analyzing, managing and optimizing real-time power consumption
Reference may also be made to an article by Lakshmikanth, A.; Morcos, M.M., Digital Object Identifier, Volume 50, Issue 3, Page(s) 724 - 731, Jun 2001. This paper presents a case study in which a DSP-based solution was developed for a power quality monitoring application is presented. Through the case study, the issues involved in adopting system architecture, selecting a DSP and developing software for an application are discussed. The methodology described in this paper presents broad guidelines which can be intelligently applied to develop DSP-based solutions to meet specific requirements.
Reference may also be made to an article by Kang Wei et al, Power Electronics and Motion Control Conference (IEEE), 2006, Page 420 - 424, Aug. 2006. The article explains a power quality monitoring system based on DSP and PCI bus technique. This system combines the powerful operational capability of DSP chip and the abundant resource of the computer together. It can monitor the five targets of power quality realtime and storage the history data with database technique. Test proved that this monitoring system can meet the requirement of the modern power quality monitoring.
Reference may also be made to an article by Birdi, Harjit Singh, Thesis, 8 August 2006. This thesis describes a technique to automate the classification and analysis of the power quality events using relay recorded data. The technique uses voltage duration and magnitude of three phases to detect and classify the events. The classified results are then presented in a user-friendly graphical form. Fast Fourier Transform (FFT) is used to estimate the fundamental frequency and harmonic components in power systems. The graphical user interface of the power quality analysis tool is developed using Microsoft Visual C++ IDE and the algorithms are programmed in C++.
Reference may also be made to an article by Ukai et al, Digital Object Identifier Volume 50, Issue 6, Page(s): 1159 - 1164, Dec 2003. This paper presents the advanced measurement system of harmonics in a wide-area distribution system. The measurement unit at each point in the distribution system consists of a digital signal processor as a high-speed processor and a global positioning system as a synchronization measurement. These units as terminals at multipoint in the distribution system are connected to the central monitoring station by the Internet. By using this system, the harmonic flows in the distribution system are measured and hence, harmonic modeling can be realized in real time.
Reference may also be made to an article by Aramendi et al, Digital Object Identifier Volume 2, Page(s) 908 -912 vol.2, May 1996. This paper presents a new system for two important applications of digital recording in real time characterization of electric signals. The first one consists of a digital recorder of the time evolution of voltage signals working in two modes: recording directly the evolution of the signal waveform or the evolution of the main electric parameters: RMS, power components and frequency values. The second application consists of a digital recorder of voltage dips. Both applications are based on the same hardware that includes a PC with two DSP cards, which make possible a real time working multichannel system.
Reference may also be made to an article by Vaclav Matz et al, Instrumentation and Measurement Technology Conference Poland, May 1-3, 2007. This paper presents a system for detection and classification of power quality (PQ) voltage disturbances. The proposed system applies the following methods to detect and classify the PQ disturbances: digital filtering and mathematical morphology are used to detect and classify transients and waveform distortions, while in case of short and long duration disturbances (such as sags, swells and interruptions) the analysis of the RMS value of the voltage is employed. The decision and classification process is based on disturbances knowledge base of an expert system.
Reference may also be made to an article by Emilio Ghiani et al, The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, Vol 23, Issue I, 92 - 103, 2004. This paper deals with the uncertainty in digital measurement systems designed for power quality applications. The main goal of this work is to evaluate such uncertainty by means of a Monte Carlo method recently proposed in the literature. The accuracy of the measurement result obtained with a DSP-based instrument for power quality metering depends on the behavior of the devices located in both the conditioning block and A/D conversion stage: it is thus necessary to consider the uncertainties introduced by each component of the system and the propagation of their effects through the measurement chain. Here, the uncertainty is estimated starting from the technical specifications provided by the manufacturers of these devices.
Reference may also be made to an article by Sen Ouyang, International Journal of Electrical Power & Energy Systems, February 2007. The article explains a new fast approach to the detection of transient disturbances in a noisy environment. In the proposed approach, the appropriate morphologic structure element, new proper

combination of the erosion and the dilation morphologic operators can enhance the MM's capability. Furthermore, the soft-threshold de-noising method based on the wavelet transform (WT) was used for reference. This method possesses the following advantages: high calculation speed, easy implementation of hardware and better use value.
Reference may also be made to an article by Tao Lin and Alexander Domijan, Jr., Electric Power Systems Research, August 2006. The article explains three criteria for selecting or developing an appropriate measurement technique. Based on these criteria, the performances of the measurement techniques in common use or newly developed are analyzed. A novel complex filter and the associated recursive algorithm are further presented in this paper, which achieve both high measurement accuracy in all service conditions and low computational complexity.
Reference may also be made to an article by P. K. Dash, International Journal of Electrical Power & Energy Systems, October 1999. The article explains a new approach for the classification of transient disturbance waveforms in a power system by using a Fourier linear combiner and a fuzzy expert system. The measured voltage or current waveforms at a distribution bus are passed through a fourier linear combiner block to provide peak or root mean square (RMS) amplitude and phase of the fundamental component at every sampling instant.
Reference may also be made to an article by Juanying Qin; Xuhua Yang; Guoping Wu, IEE Conference, 10-13 Oct. 2004. The paper explains that the system includes an intelligent control scheme of the double power supplies system based on digital signal processor (DSP) and controller area network (CAN). In this scheme, the power inverter can synchronously track the network precisely in double power supplies condition, and switch in double directions seamlessly (in less than 2.4 ms) between double power supplies. This control system provides online detection and calculations, monitoring and adjustment, setting and modifying of parameter, storing and inquiring, computer management and communication for double power supplies information.
There needed a system which can be used with low as well as high Frequency and have facility to record data in PC . Some of the prior systems includes dual double power supplies dual DSP/ controller. Some systems are restricted only to voltage anomalies, event-triggering methods and detection of transient disturbances in a noisy environment, Some prior systems are suitable for five targets and power quality analysis tool is developed using Microsoft Visual C++ IDE and the algorithms are programmed in C++.
With all the above discussed restrictions or limitations it is required to have improved power quality monitoring and signal generating system. The present invention provides power quality monitoring and signal generating system. At least six channels are present for power quality monitoring. Thus simultaneously multiple devices can be monitored. It captures wave shape of signal along with spikes, under voltage etc. It audits quality over a period of time from one to infinity. The present system can accept all types of waveforms eg. Sinewave, triangular, rectangular etc. This system has integrated GPRS
modules and sends data over web server. THD is also calculated for all the power sources. It can compare the power quality of multiple apparatus. It generates sine wave form using single dgital signal processor (DSP) internally to help comparison of different waveform with that of the standard Sinewave
OBJECTS OF THE INVENTIQN-
The primary object of the present invention is to provide a system which can monitor the power and generate the signals.
Another object of the present invention is to provide a system which can monitor multiple devices simultaneously.
Yet another object of the present invention is to provide a system which can capture wave shape of signal along with spikes, under voltage etc
Still another object of the present invention is to provide a system which audits quality over a period of time from one to infinity.
Another object of the present invention is to provide a system having integrated GPRS modules.
Yet another object of the present invention is to provide a system which can send data over web server.
Still another object of the present invention is to calculate the THD for all the power sources connected to the equipment.
Another object of the present invention is to provide a system which generates pure sine wave using DSP with THD< 0.4%.
Yet another object of the present invention is to provide a system which generates sine wave using DSP and also compares different waveforms Along with THD.
Still another object of the present invention is to provide a system which compares the power quality of multiple apparatus
SUMMARY OF THE INVENTION
In order to overcome the mentioned problems and to achieve the said objects, the present invention provides power quality monitoring and a signal generating apparatus. Multiple devices simultaneously can be monitored by this system. The system captures wave shape of signal along with spikes, under voltage etc. It audits quality over a period of time from one to infinity. This system has integrated GPRS modules and sends data over web server. THD is also calculated for all the power sources. It can compare the power quality of multiple apparatus. It generates sine wave form using DSP internally to help comparison of different waveform with THD < 0.4.
The present system comprises at least one analog signal receiver including a plurality of analog signal channels for receiving a plurality of analog measurement signals representing power conditions, for converting the analog measurement signals into digital signals including digital signal data and for buffering it. The analog signal channels include at least one high/low frequency voltage channel for monitoring voltage signals including high frequency voltage events and at least one configurable multi-purpose channel for monitoring low frequency analog measurement signals. At least one digital signal processor, connected to the analog receiver, reads the digital signal data buffered by the analog signal receiver and processes the digital signal data. The digital signal processor processes the digital signal data by logging at least some of the digital signal data and wherein digital signal processor processes the digital signal data by analyzing at least some of the digital signal data to detect a pattern consistent with an event and by logging selected values of the digital signal data sufficient to define the said event. A post-processing system, connected to the digital signal processor, stores and post processes the processed digital signal data received from the digital signal processor.
The post-processing system preferably includes a communication device for communicating with a remote location and for transmitting the said processed digital signal data to the remote location. In one embodiment, the post-processing system is implemented on a personal computer. In this embodiment, the analog signal receiver includes at least one analog board connected to the personal computer and the digital signal processor includes at least one digital signal processor board connected to the personal computer. The multi-purpose channel is preferably configurable to monitor one of a low frequency voltage signal, a current signal, and an environmental condition signal and the personal computer preferably includes software for configuring the multi-purpose channel.
The present invention also discloses a method of monitoring power quality monitoring and signal generating apparatus. The method comprises the following steps: (1) receiving analog voltage signals over high/low frequency voltage inputs and receiving analog measurement signals over multi-purpose inputs; (2) converting the analog voltage signals and the analog measurement signals into low frequency digital data; monitoring the analog voltage signals to detect high frequency voltage signals representing high frequency voltage events; (3) converting the high frequency voltage signals into high frequency digital data; (4) processing the low frequency digital data by logging selected values of the low frequency digital data into at least one data log file (5) processing the low frequency digital data and the high frequency digital data by detecting events and logging the events in an event log file.
The present invention is also directed to an analog signal receiver for use in a power quality monitoring and signal generating apparatus. The analog signal receiver comprises a plurality of analog signal inputs including high/low voltage signal inputs for receiving voltage signals and multi-purpose inputs for receiving low frequency analog measurement signals. A plurality of isolated measurement circuits measure the voltage signals received on the said high/low voltage signal inputs. Analog signal processing
circuitry processes the voltage signals and the low frequency analog measurement signals. A multiplexer multiplexes the voltage signals and the analog measurement signals into a multiplexed low frequency analog signal. A low frequency A/D converter converts the multiplexed low frequency analog signal to low frequency digital signal data. A low frequency buffer buffers the low frequency digital signal data.
The analog signal receiver further includes a high frequency voltage event detector for detecting high frequency voltage events. At least one high frequency A/D converter converts the high frequency voltage events to high frequency voltage digital data. A high frequency buffer buffers the high frequency voltage digital data.
Each isolated measurement circuit preferably includes an isolation amplifiers and an isolated signal transmitter connected to the isolation amplifier. The isolated signal transmitter can include a linear optocoupler, a transformer coupler and a capacitive coupler. The high frequency voltage event detector preferably includes a peak detect circuit.
The present invention also features a system and method for processing data in a power quality monitoring and signal generating apparatus. The method comprises receiving high frequency data and low frequency data, representing voltage signals and condition signals. The method also comprises generating data log entries, each including at least a date/time stamp and at least some of the low frequency data and logging the data log entry in a data log. The method further comprises classifying the high frequency and low frequency data to determine an event classification, analyzing the high frequency and low frequency data based upon the event classification and selecting sufficient data values to define the event, generating an event data log entry and logging the event data log entry into an event log.
In one aspect of the present invention, the signal can be sine wave, square wave, saw tooth wave etc.
In an embodiment of the present invention, the channels for power quality monitoring can be upto infinity.
In an embodiment of the present invention, display device can be Graphical LCD, touch screen, PC, PDA phone.
In an embodiment of the present invention, integrated communication system can be GPRS, GSM, Wi- Fi and blue tooth.
In an embodiment of the present invention, USB, RS-232, Ethernet can be used for
communication.
In another embodiment of the present invention, the sine wave form can also be
generated by using controller.
The foregoing as well as additional objects, features and advantages of the invention will be more readily apparent from the drawings and their detailed descriptions.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:
Fig. 1 is a schematic diagram of the power monitoring system, according to the present invention;
Fig. 2 is flowchart, according to the present invention;
Fig 3: shows Waveform of Mains, Genset and Inverter
Fig 4: shows Pure sine wave form of the device under measurement
Fig 5: shows Pure square wave form of the device under measurement
Fig 6: shows Graph of frequency and voltage with respect to time
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 illustrates a basic block diagram of a system in accordance with the present invention. The power quality monitoring and signal generating system, is used to monitor the quality of power provided to a site as well as other environmental conditions that might affect the operation of electronic equipment at the site. At least six channels (100) are provided for monitoring power quality. Thus simultaneously multiple devices can be monitored. The system compares the power quality of multiple apparatus. The system detects and records power events, such as spikes, sags, surges, inrush current and other transients and records power conditions, such as voltage level, RMS volts, THD, phase differential, A/C frequency, current, line impedance and ground potential. The system can be used to monitor any type of event or condition capable of being detected or measured. The system audits quality over a period of time from one to infinity. This system has integrated GPRS modules and it sends data over web server. THD is also calculated for all the power sources. It generates sine wave form using DSP (101) internally to help comparison of different waveform with THD < 0.4. In general, the system includes an analog signal receiver (102), a digital signal processor (DSP) (101), measurement devices and a post-processing system.
The analog signal receiver includes a plurality of analog signal channels for receiving analog measurement signals from the measurement devices, such as test leads, passive probes and active probes. One or more of the analog signal channels on the analog signal receiver are capable of monitoring high frequency voltage signals representing high frequency power events, such as high frequency voltage events and high frequency
ground events. In one example, the analog signal receiver includes channels with channels capable of monitoring high frequency voltage signals. The analog signal receiver converts the analog measurement signals into digital signals and buffers the digital signals.
The DSP (101) reads the digital signal data buffered by the analog signal receiver and processes the digital signal data by logging at least some of the digital signal data and by analyzing the digital signal data to detect power events. The DSP (101) buffers the processed data (i.e., the logged data values and the data representing detected events) and transmits the processed data to the post-processing system.
The post-processing system stores the processed data and performs post-processing, such as formatting the processed data and generating reports. The post-processing system can also communicate with a remote client for performing various tasks remotely, such as downloading data, remotely controlling the system and performing diagnostic functions.
According to the exemplary embodiment, the post-processing system includes a PC (103), a storage device, such as a hard drive or memory and one or more communications devices, such as a network card and/or a modem. Analog board (102) includes a plurality of analog signal inputs for connecting the measurement devices to the analog signal channels (100). The inputs include voltage inputs connected to high/low frequency voltage channels (100) capable of detecting high frequency voltage transients as well as low frequency events. In one example, the voltage inputs include voltage inputs for each of three phases (LI, L2, L3), for ground (G) and for neutral (N).
The inputs also include multi-purpose inputs connected to multi-purpose channels (100) used for low frequency monitoring such as current, temperature and the like. Multipurpose channels can also be used for low frequency voltage monitoring, such as DC Volts and ground monitoring. In one example, the multi-purpose inputs include current inputs for each of three phases (LI, L2, L3), for ground (G), for neutral (N) and a DC voltage input. As described in greater detail below, each of the multi-purpose inputs and channels can be configured for any type of low frequency monitoring.
High/low frequency voltage inputs are preferably connected to two isolated measurement circuits for taking a high frequency voltage measurement and a low frequency voltage measurement.
The preferred embodiment of the isolated measurement circuits is a multi-channel (100) differential isolated measurement circuit including an isolation amplifier and an isolated signal transmitter connected to the isolation amplifier. According to one embodiment, the isolated signal transmitter includes a linear opto-coupler. By using an optically coupled isolation amplifier high accuracy, linearity and temperature stability are achieved. This circuit acts as a current-to-voltage converter. By providing isolation between two different potentials, the differential isolated measurement circuit prevents false data commonly found in differential amplifiers, which are the foundation of many circuits.
According to another embodiment, the isolated signal transmitter includes a transformer coupler for magnetically coupling the isolation amplifier to the voltage signal conditioner. According to a further embodiment, the isolated signal transmitter includes a capacitive coupler, such as four (4) and six (6) plate capacitors, for capacitively coupling the isolation amplifier to the voltage signal conditioner.
The analog board further includes analog signal processing circuitry coupled to the isolated measurement circuits and to the multi-channel inputs. In the exemplary embodiment, the analog signal processing circuitry includes over voltage protection, voltage signal conditioners, sample & hold circuits and input buffers. A multiplexer connected to the analog signal processing circuitry multiplexes the analog signals on all of the channels and passes the multiplexed analog signals to an A/D converter. The A/D converter converts the analog signals on each of the channels to digital signal data.
A buffer, such as a FIFO buffer, is coupled to each of the A/D converters (102), for continuously buffering the digital data corresponding to the voltage signals and condition monitoring signals. The control controls the timing and state of the A/D converter (102), FIFO buffer and multiplexer. In one example, the control is a hardware function implemented as a complex programmable logic device (CPLD) field programmable gate array (FPGA).
The analog board preferably includes a high frequency A/D converter for each of the high frequency voltage channels to convert high frequency voltage signals to digital data. The high frequency voltage digital data is sent to a buffer, such as a first-in/first-out (FIFO) buffer or memory. The analog board (102) further includes a high frequency voltage event detector for detecting high frequency voltage events, such as transients. The high frequency FIFO buffer writes the data on and takes the data off until a high frequency event is detected. The FIFO buffer or memory preferably has a capacity capable of buffering the digital data values corresponding to the high frequency event as well as a configurable number of digital data values just prior to the event.
The analog board can also include separate RMS voltage and current circuitry that provide RMS data without using the DSP (101). This RMS circuitry allows fast calculation (e.g., waveshape, harmonics, etc.) to be performed while conserving the processing power of the DSP.
The process digital signal processor used in the system includes a processing and event detection (FED) buffer for buffering the raw data received from the DSP and a PED processing component for processing the raw data and storing the processed data. Data log files are used for the low bandwidth inputs or less frequent data calculations and event log files are used for the high bandwidth inputs.
The FED processing component is preferably implemented as software. For data logging, FED processing component receives the raw data from the FED buffer and appends a log entry to the end of a data log file. Each log entry includes at least a date/time stamp and the data values needed to define the condition being logged. The log entry can also include other data such as phase angle, duration, channel number and/or A/C frequency. The system preferably includes a data log file for each of the channels being monitored. Examples of the low frequency data include low frequency ground monitoring, RMS volts, phase differential, A/C frequency and current which are described in greater detail below.
For event detection and logging, the FED processing component receives the raw data from the FED buffer and uses an algorithm to classify the data based upon predefined rules in a knowledge base. The FED processing component also analyzes the event data to determine how the event data values should be stored. If the event is a high frequency event, then, the FED processing component selects the minimum number of data values needed to define the event based upon the classification of the event. For each detected event, an event entry is added to the event log file. Each event entry includes at least a date/time stamp, the event classification and the selected minimum number of data values (i.e., the compressed event data). The high frequency event data is thereby compressed and can be stored and transmitted more easily. Examples of the events processed by the FED processing component include A/C wave-shape events, voltage events and ground events, as described in greater detail below. Also, whenever a system events occur, such as a start, stop, power-up, power-down, an event entry can be generated and appended to the event log.
The DSP buffers and transmits the processed data to the PC (103) for post-processing, storage or transmission through communication port (104). The DSP transmits the processed data in the data log files and the event log file(s) to the PC (103). The PC (103) stores the processed data and can generate a data report using the processed data or can transmit the processed data to a remote location for generation of the report. The raw data for any of the channels can also be stored, if needed.
According to one embodiment, the PC (103) formats the data in a standard form so that the files can be easily accessed and shared across a network. The PC (103) can process the data by removing any start-up or initial test data and by reviewing the data for patterns or irregularities. The data can then be reformatted and archived into a central computer. The data can also be used to generate a specific report for a site being monitored and then archived for use as a monthly, quarterly or yearly summary report for that site. The individual site data can also be compared to other similar sites and compiled into a status report with site comparisons.
The system preferably includes software for configuring and testing the analog boards and the DSP (101) board. The screens shown in Figs.3- 5 illustrate one embodiment of the graphical user interface (GUI) for the software of the present invention. The GUI screens shown are used to configure the system. Configuration options include measurement requirements, operational limits, sample rates, log rates and multi-purpose channels, as will be described in greater detail below. Configuration can be performed remotely or through a local interface. The GUI screens shown in figures are used to test
and debug the system, for example, the analog boards and other hardware components.
A specific example of the data sampling and data processing according to one embodiment of the present invention is described below. According to this example, the inputs to the system include, but are not limited to, voltage, grounds, current, DC voltage etc. The system acquires voltage data on the high/low frequency voltage channels including low frequency voltage data and high frequency voltage data.
The processing includes, but is not limited to, A/C wave-shape events, high frequency voltage events, low frequency ground monitoring, high frequency ground events, RMS volts, phase differential computations, A/C frequency computations, current computations and logging off. Since measuring voltage is the main function in this example, a number of different types of processing are performed on the voltage data.
A/C wave-shape monitoring is preferably used with the high/low frequency voltage channels but can also be configured for any of the multi-purpose channels. A/C waveshape monitoring compares each A/C wave-shape against some nominal wave-shape. When the monitoring system starts, it samples a configurable number of A/C waveshapes and averages them together to generate the nominal A/C wave-shape. Once the nominal A/C wave-shape is generated, a log entry is appended to the event log file including the following information: date/time stamp; event type - Nominal; channel; nominal voltage data filename; A/C frequency and A/C frequency differential (if applicable). This nominal wave-shape is then used to compare each successive A/C cycle. If the voltage deviates by a configurable number of volts from the nominal for a configurable number of points, an event entry is appended to the event log file including the following information: date/time stamp; event type—voltage sag or surge; channel; duration; max voltage; classification of deviation; and event data filename (if applicable).
The raw event data for A/C wave-shape events can also be stored, either unconditionally for diagnostic purposes or through some other criteria. The raw data is stored, beginning with the cycle in which the event occurred; up to some configurable number of raw data points. Raw current data can also be stored for the duration of the A/C wave-shape event. The nominal wave-shaped can be regenerated, for example, if a major change in the wave-shape is detected or unconditionally at some fixed interval.
High frequency voltage event processing is configured for the high/low frequency voltage channels. Certain high frequency voltage data events can be processed using the 10/90/Peak/50 standard by determining when the following data points occur relative to the start of the event (1)10% of peak voltage (2) 90% of peak voltage (3) peak voltage (3) 50% of the falling peak voltage and duration. From these data values, an accurate representation of a high frequency voltage event, such as a unidirectional impulse or a ringing impulse, can be generated. Other data points, in addition to or in place of the 10/90/Peak/50 standard, can also be used to process and store high voltage event data. When processing data for a ringing impulse, for example, in addition to using the 10/90/Peak/50 standard, the peak voltage points and zero-crossing points are determined until the ringing impulse has deteriorated to a predetermined point (e.g., less than 10% of peak). For arcing impulses, the following data points are determined: start of impulse,
positive peak voltage, negative peak voltage, and end of impulse. An event entry for the high frequency voltage event is added to the event log file and includes the following information (1) date/time stamp (2) event type-high frequency voltage (3) channel (4) data points defining event (5) the voltage data filename (if applicable) (6) current data filename (if applicable).
Processing of the high frequency events also includes marking the location where the high frequency event occurs within the wave-shape. The peak voltage data value read from the high frequency event data replaces the data value within the wave-shape data at the point at which the high frequency event occurred. This preserves the general location of the high frequency event and provides a more accurate representation of the event within the wave-shape data. The system can also record raw voltage data to a file, either unconditionally for diagnostic purposes or through some other configurable criteria. If raw voltage data is recorded, the system can also be configured to store the corresponding raw current data.
Processing of high frequency events further includes controlling the sensitivity level of the frequency at which high frequency events occur. When the monitor starts, as part of the nominal wave-shape processing discussed above, the sensitivity can be continuously decreased until the high frequency input stabilizes. A sensitivity level log entry is then added to the event log file and includes the following information: (1) date/time stamp (2) event type—high frequency sensitivity (3) sensitivity setting. The sensitivity level can be re-adjusted if the high frequency events occur too frequently and can be adjusted according to user defined criteria.
High frequency ground events are configured for one of the high/low frequency voltage channels. High frequency voltage transients for ground are processed in a similar manner to the high frequency voltage events with the exception that no marker is placed on the wave-shape data since there is no wave-shape.
Low frequency ground monitoring can be configured for any one of the high/low frequency voltage channels or the multi-purpose channels. Low frequency ground monitoring logs the minimum, maximum and average voltage read for some configurable period of time. An entry is appended to the ground monitoring data log file used for that channel. The log entry includes: (1) date/time stamp (2) minimum volts (3) maximum volts and average volts.
RMS processing is preferably performed on the high/low voltage channels but can be configured for any of the multi-purpose channels. RMS calculations are made for each A/C volt cycle for a configurable period of time. The maximum, minimum, average RMS values are gathered and added as an entry to the RMS data log file used for that channel. The RMS log entry includes: date/time stamp; RMS minimum; RMS maximum and RMS average.
Phase differential is computed between any two channels capturing A/C voltage by comparing the zero cross points on the two channels and counting the number of data points between the two. Phase differential is computed and reported as part of the
nominal wave-shape event discussed above. Any change in the phase differential shows up within a voltage event, when the nominal wave-shape is recomputed.
A/C frequency is determined prior to generating the nominal wave-shape, as discussed above. Initially, the system samples at the configured sample rate and assume an A/C frequency of 50 Hz. Using the first wave-shape channel with valid data, the system then counts the number of points between zero crossings. If the number of points does not match the number of points/cycle sample rate, the frequency is recomputed and the new A/C frequency is used to compute the sample rate for all of the A/C voltage and current channels. The A/C frequency is reported as part of the nominal wave-shape event discussed above. A change in the A/C frequency results in a voltage event and the A/C frequency is recomputed when a new nominal wave-shape is generated.
For current monitoring, the minimum, maximum and average RMS current is computed and recorded for some configurable period of time. An entry is appended to a current data log file for that channel and includes the following information: date/time stamp; minimum current; maximum current and average current. The rate at which the channel is sampled and the time interval at which the min/max/avg are computed is configurable.
The system can also be used to perform interactive tests by taking measurements on the input and output of a device, such as UPS, while downloading the internal system log of the UPS. The system can also perform line impedance tests by interfacing to an external test system and adding data to the event log of the system. The interactive tests can be controlled automatically by the PC or manually.
Fig 2 shows flowchart according to the present invention. At first, ADC and communication channel are initialized. RMS value of waveform / one cycle samples / pure sine wave samples and frequency of channel are captured. The device transfers the respective values to PC on the request from PC GUI application. RS-232, TCP/IP, GSM/GPRS, USB are used for transferring the values the PC can use either. PC GUI application displays voltage/ frequency vs. time, waveform of channel, pure sine wave generated by device, capturing and comparing waveforms of multiple power sources graphically.
Fig 3 shows comparison of the waveforms of mains, genset and inverter. Green line indicates waveform obtained from genset, black line indicates waveform obtained from inverter and red line indicates waveform obtained from the mains.
Fig 4 and 5 shows pure sine and square wave forms of the device under measurement respectively. Fig 6 shows graph of frequency and voltage with respect to time. Red line shows the variation of voltage with respect to time and blue line shows the variation of frequency with respect to time.
It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims: -

WE CLAIM:
1. An apparatus for monitoring power and generating signal comprises at least one
analog signal receiver including a plurality of analog signal channels for receiving a
plurality of analog measurement signals representing power conditions for converting
the analog measurement signals into digital signals including digital signal data and
for buffering the digital signal data, a digital signal processor (DSP) which reads the
digital signal data buffered by the analog signal receiver and processes the digital
signal data by logging at least some of the digital signal data and by analyzing the
digital signal data to detect power events, measurement devices for a high frequency
voltage measurement and a low frequency voltage measurement, which generate
multiple signals and simultaneously monitor multiple devices and a post-processing
system including a communication device for communicating with a remote client
and for transmitting said processed digital signal data to the remote location..
2. An apparatus as claimed in claim 1 wherein said system detects and records power
events, such as spikes, sags, surges, and other transients and records power
conditions, such as voltage level, RMS volts, THD, phase differential, A/C frequency,
current, line impedance and ground potential.
3. An apparatus as claimed in claim 1 or 2 wherein said system generates sine wave
form using DSP internally to help comparison of different waveform with THD < 0.4.
4. An apparatus as claimed in any of the preceding claims wherein the apparatus has
integrated GPRS modules and sends data over web server
5. An apparatus as claimed in any of the preceding claims wherein the apparatus
generates sine wave using DSP.
6. An apparatus as claimed in any of the preceding claims wherein the apparatus can
monitor one to multiple channels simultaneously.
7. An apparatus as claimed in any of the preceding claims wherein the apparatus audits
quality over a period of time from one to infinity.
8. An apparatus as claimed in any of the preceding claims wherein the DSP buffers the
processed data (i.e. the logged data values and the data representing detected events)
and transmits the processed data to the post-processing system.
9. An apparatus as claimed in any of the preceding claims wherein said post-processing
system stores the processed data and performs post-processing, such as formatting the
processed data and generating reports in which the post-processing system includes a
PC, a storage device, such as a hard drive or memory and atleast one communication
devices such as a network card and/or a modem.
10. An apparatus for monitoring power and generating signal substantially as herein
described with reference to the accompanying drawings.