Title of Invention

A DEVICE FOR MONITORING ON-LINE DIELECTRIC PARAMETERS

Abstract

This invention relates to a device for continuous and on-line monitoring dielectric parameters comprising an excitat¬ion signal source connected to the insulation of the job in the vacuum impregnation plant, a sensing probe connected in series with said insulation of the job in vacuum impregnat¬ion plant to sense the current in the insulation and provides a signal to a data acquisition device to process said signal to provide dielectric parameter data wherein said data acquisition device comprises a sampling differential amplifier connected to said probe to receive and ,amplify the signal and fed to A/D converter, multiplexer and input/ output bus all connected in series, said processed and conditional signal is fed to data acquisition and analysis software which is connected to a monitor of the computer and plotter to provide dielectric parameters in graphical form. This is a simple, compact and portable device in which sensor can be easilly selected to match the object size. This eliminates manual processing in case of manual technique and extensive electronic processing in case r.f. modulation based instrumentation for the purpose.

Full Text

This invention relates to a device for monitoring on-line dielectric parameters used during the process of insulations/ vacuum impregnation provided on the windings for generators and motors. It is the known art that the dielectric: parameters are monitored manually to provide the suitable insulations on the winding for use in generators and motors. There are disadvantages associated with the manual monitoring of die 1ectric parameters. One of the main disadvantage is that due to individual involve¬ment, the dielectric parameters are not monitored efficiently and correctly. Individual has to capture waveform, find out the phase and magnitude of individual signals and from these signals, he has to calculate the parameters which is a very tedious job with chances of error. Another disadvantage is that the technology was available only for measuring of dielectric parameters at discrete points and that too using complex and discrete circuits/hardware. Further, earlier technology was based on s smaller sample size, size limited by dynamic range. SUMMARY OF THE INVENTION Therfore the main object of the present invention is to propose a device for monitoring on-line dielectric parameters used during the process of insulat ion/impregnation on the windings for the generators and motors which is automatic without any chance of human error. Another object of the present invention is to propose a device which is adapted to work on-line in order to continuously monitor the dielectric parameters during the process of insulation. As regards "sensing probe" stated in this Specification, it refers to sensing element which is basically a resistance element designed and configured in circuit to sense the current and phase signal from which capacitance and tan 8 parameters are extracted. The specific position/location of this sensing probe in the overall circuit is such that signal sensed by sensing probe is free of electrical noise and to eliminate unwanted electrical signals and sense the correct and reliable signal for recording the data. The design, configuration and selection of the sensor makes the wider dynamic measurement of data without necessity to change the range during ongoing process. Further, with this sensor no pre¬processing or any signal conditioning is required. Data signal is directly fed to data acquisition system. Further, the "data acquisition and analysis software" referred to herein is a novel feature of data acquisition system lies in the fact that it eliminates a substantial portion of the hardware involved - like impedance matching, amplification of signal, filtering, phase detection / measurement, resolving of vector, scaling etc and most of the signal processing is carried out using input digitizer and specially designed soft- ware. All these features eliminate substantial hardware and associated hardware problems, increases reliability and makes overall system compact and easy to use. According to the present invention, there is provided a device for monitoring on-line dielectric parameters comprising an excitation signal source connected to the insulation of the job in the vacuum impregnation plant, a sensing probe which is sensing element, basically a resistance element connected in series with said insulation of the job in vacuum impregnation plant to sense the current in the insulation and provides a signal to a data acquisition device to process said signal to provide dielectric parameter data where said data acquisition device comprises a sampling differential amplifier connected to said probe to receive and amplify the signal and fed to A/D converter, multiplexer and input/output bus all connected in series, said processed and conditioned signal is led to data acquisition and analysis software which is connected to a monitor of the computer and plotter to provide dielectric parameters in graphical form. The nature of the invention, its objective and further advantages residing in the same will be apparent from the following description made with reference to non-limiting exemplary embodiments of the invention represented in the accompanying drawings. Fig. 1 shows a schematic block diagram used during monitoring of tan 5 and capacitance on motor vacuum pressure impregnation (VPI) plant; Fig.2 shows the schematic of basic circuit; Fig.3 shows the block diagram of on-line dielectric parameters monitoring device during impregnation; Fig.4 shows the graphical representation of dielectric parameters. According to this invention, the device for monitoring on-line dielectric parameters during the process of insulation of winding of motors and generators comprises an excitation signals source (1) adapted to be connected to the insulation to the impregnation plant (2), a signal sensor probe (3) connected to the said insulation being connected to a data acquisition means (11) provided for processing of said signals (3) and to provide dielectric parameter data. The schematic used for capturing and recording to dielectric parameters like tan 8 and capacitance during impregnation of sample bars in VPI plant is shown in Fig. 1. During the initial development effort, the sensing resistor was connected in series with the winding insulation of sample (18) under test in VPI plant (12). Excitation signal (Vexc) (.17) was fed to the circuit from a signal generator (17). The voltage drop across the sensing series resistor (Vsig) (13) gave the current flowing in the insulation of the machine which was captured by the digital storage oscilloscpe (DSO) (.1.6) connected in par-all el with the sensing resistor (13). Both the signals corresponding to current in the winding insulation in channel-1 (CHI) (14) and excitation signal in channel-2 (CH2) (15) were fed to the dual channel storage oscilloscope (16) and both these signal waveforms were captured simultaneously and stored. From the phase difference between the two waveforms and their magni¬tude various other parameters were calculated. To monitor the parameters during the whole of impregnation process, it is required to manually capture the waveform, find out phase and magnitude of individual signals and from these calculate the parameters and repeat this exercise, say every 2/3 minutes and then plot the graph. This process was quite time consuming, labo¬rious and practically very difficult to implement. Having established this basic technique it was adapted as it is into automated DAS (data acquisition system) as detailed below. A device for monitoring dielectric parameters during process of insulation/vacuum impregnation of windings of generators and motors are described and illustrated in the accompanying block diagram in Fig.3. The device has an excitation signal source (1) which feeds the excitation signal to insulation in the impregna¬tion plant (2). A sensing probe (3) is connected in series with insulation which senses the current in the insulation and feeds •the signal to the data acquisition ( 11 ) system provided for processing the signals in order to provide the dielectric para¬meters in the graphical form. The data acquisition (1.1) system comprises of sampling differential amplifier (4), A/D converter (5), multiplexer (6), input/output bus 7. The processed and con¬ditioned signal is fed to data acquisition and analysis software (8) which is connected to monitor (9) on the computer and plotter (10) which gives the dielectric parameters in graphical form. This system senses impregnation of job along its maximum length End gives indication of overall magnitude of parameters. As such, represents wider sampling (sensing) as against localised sensing. The probe (3) for capturing the field signal was designed around a bank of resistances in series with the winding insulation under impregnat ion. Considering a wide range of capacity of jobs to be tested using this system the probe (3) was designed with a sensitivity selector in 10 steps to cover a wide dynamic range. The system can be used for capacitance measurement up to 1*3 uf. Dynamic: range of tand variation is 0.01 to 10. Excitation signal magnitude was selected to be 10V peak to peak based on experimental data. The Data Acquisition System has 12 bit analog to digital converter and provision of Ik single-ended or 8 differential, switch selectable channels. It can handle signals from 10 Hz to 10 KHz frequency range. Accuracy of the system is 1.0%. This data is processed and obtained in graphical form as dielectric parameters - capacitance v/s time and dissipation factor v/s time. Tabulation of other parameters can also be obtained on-line. Fig.4 shows the graphical representation of dielectric parameters. The novel device of the invention is very useful for monitoring the dielectric parameters during the insulation process. Excita¬tion signals are sent after a predetermined interval of time which are being processed by the data acquisition means auto¬matically and that it helps to monitor the insulation process. The invention described hereinabove is in relation to non-limiting embodiments and as defined by the accompanying claims. WE CLAIM; 1 - A device for monitoring on-line dielectric parameters comprising an excitation signal source (1) connected to the insulation of the job in the vacuum impregnation plant (2), a jsensing probe (3) connected in series with said insulation of the job in vacuum impregnation plant (.2) to sense the current in the insulation and provides a signal to a data acquisition device (11) to process said signal to provide dielectric parameter data wherein said data acquisition device comprises a sampling differential amplifier (4) connected to said probe (.3) to receive and amplify the signal and fed to A/D converter (5), multiplexer (6) and input/output bus (7) all connected in series, said processed and conditioned signal is fed toccata acquisition and analysis software (8) which is connected to a monitor (9) of the computer and plotter (10) to provide dielectric parameters in g r a p h i c a; 1 for m. 2. A device for monitoring on-line dielectric parameters as claimed in claim 1 wherein said probe (3) is provided with a (Sensitivity selector in 10 steps to cover a wide dynamic range. 3. A device for monitoring on-line dielectric parameters as claimed in claim 2 wherein said probe produces an excitation signal is of magnitude upto 10V peak to peak. 4. A device for monitoring on-line dielectric parameters as claimed in claim 1 wherein said device is used for capacitance tneasurement upto 10µf and dynamic: range of tand variation in 0.01 to 10. 5. A device for monitoring on-line dielectric parameters as claimed in claim 1 wherein said data acquisition system (11) is. provided with 12 bit analog to digital converter (5) and a multiplexer (6) with a provision of 16 single-ended or 8 differential, switch selectable channels. 6. A device for continuous monitoring and trend plotting of on-line dielectric parameters viz. capacitance substantially as herein described and illustrated with accompanying drawings.

Documents:

452-del-2001-abstract.pdf

452-del-2001-claims.pdf

452-del-2001-correspondence-others.pdf

452-del-2001-correspondence-po.pdf

452-del-2001-description (complete).pdf

452-del-2001-drawings.pdf

452-del-2001-form-1.pdf

452-del-2001-form-19.pdf

452-del-2001-form-2.pdf

452-del-2001-form-3.pdf

452-del-2001-gpa.pdf