Title of Invention

AN INDUCTION TYPE CURRENT SQUARE INTEGRATING METER

Abstract

Disclosed herein is an induction type current square integrating meter for estimation of energy loss in a single phase power distribution network, which comprises of an aluminum disc having two electromagnets placed on either side of the disc, said disc being fixed on a shaft mounted on bearings and is connected to a revolution counter and a display device to record, store and display the total number of revolutions of the said disc, the said disc being made to rotate at a constant velocity proportional to the square of the current that is being supplied to the electromagnets .

Full Text

This invention relates to an induction type current square integrating meter for estimation of energy loss in electrical power networks, both in single phase power supply and three phase power supply. At present the following methods are used for estimating the energy loss during power distribution: (i) Estimation of energy losses as the difference in the uiput energy and output energy; or (ii) Estimation of energy losses using approximate formulae based on system peak load and loss factors. Energy loss estimation as the difference between input and output requires that all inputs and outputs are measured. Moreover the readings of all the meters at the beginning and end of the interval of interest must be available. The readings must correspond to the same instant of time, hi the present state of our utilities, there is very little metering. Even when all the load points are metered, the number of meters involved make it almost impossible to guarantee that all meters are working, accurate and read simultaneously. Further, even if one manages to get all the readings, since no meter is perfect, the scheme of assessment is inherently very sensitive to the errors in measurement, as it envisages computing loss - a small quantity as a difference of two large quantities - input and output. Therefore, any small percentage error in the measurement of these two large quantities manifests as a very large percentage error in the loss estimation. The formula based method is also prone to error. The estimation of peak load is based on peak power and an assumed power factor. Peak loss is estimated assuming nominal voltages. Loss factor is obtained as a function of load factor. The load factor (LF) estimation is based on the peak load and total energy input. The loss factor is related to the load factor through a thumb rule as 0.2LF + 0.8LF^. This thumb rule seems to be based on typical load curves seen in western utilities 70 years ago. The load variations that are seen in our systems due to load shedding and single pulse operations are vastly different from such typical variations. Indian utilities did not pay any serious attention to this issue till recently, as they were in the pubUc sector and were more service oriented. With the advent of restructuring, the state utilities have to justify their loss estimates to Regulatory Commissions. There is a very urgent need to evolve simple and reliable means for estimating losses in electrical distribution networks. Further, there appears to have been no serious efforts in the past to evolve efficient loss estimation schemes for radial distribution networks. In the developed countries, these losses are very small and the research emphasis was always on bulk power generation and transmission systems. Even with the advent of restructuring in the electric power sector, there has been little interest in the distribution networks and their loss estimation. The situation in developing countries has been totally different; Distribution losses are very high. Even then the emphasis in the past has been on extending the networks rather than improving their efficiencies. Moreover electric utilities have always worked as service providing government entities rather than profit making commercial organization. Hence, the lack of previous work can be attributed to the lack of incentives in estimating these losses accurately The present invention proposes to overcome the shortcomings of the existing methods. The proposed system does not make use of input and output energy measurements or is based on any thumb rules. The core idea is to measure a quantity, which has a direct bearing (nearly proportional) to the loss in the network and accoimt for the current distribution in the network by appropriate means. Proposed herein is a novel the design of a meter, which can be used to measure the time integral of the square of the current supplied to the network. The energy loss in the network is computed as the product of the measured value and a factor, which can be determined given the network structure and the load distribution. The method of estimating the energy losses in a network in terms of the reading recorded in the new meter proposed herein. There is no reference to loss estimation through a measurement as proposed here in any textbooks or any other literature. Accordingly, the main object of the present invention is to provide an induction type current square integrating meter, hereinafter referred to as " j/^ dt meter", which measures a quantity, which has a direct bearing on the energy losses and use a factor to account for the spatial distribution of the load in the network in order to estimate the energy losses in a reliable way. A further object of the present invention is to provide a meter, which is intended for use in radial HT and LT distribution networks where the network topology remains fixed and the power flows are unidirectional. Yet another of the present invention is to provide both induction and digital type J ^^ dt meter. The invention thus provides both induction and digital types of J/^ dt meters. The induction type meter having two electromagnets 2, 3 placed on either sides of a suitably shaped aluminum disc fixed on a shaft (not shown). The coils of the electromagnets being energized by currents 4, 5 proportional to the current whose square is to be integrated and obtained as shown in Fig.l of the accompanying drawings, so that the two coil currents 4,5 are in phase quadrature and produce a torque proportional to the square of the cxirrent to drive the aluminum disc. The said disc is made to rotate at a constant velocity proportional to the square of the current 1 (1) by using a braking magnet and the disc's velocity is made to be proportional to the square of the current throughout the range of the meter with the use of magnetic shunts. The set of electromagnets 2, 3, brake magnet and magnetic shunts and the disc (not shown) repUcated (for use in polyphase systems) three times for use in a 3-phase, 3-wire system, and four times for a 3-phase, 4- wire system, with all tiie discs fixed to a common shaft mounted on bearings and the shaft linked to a revolution counter and a display device to record, store and display the total number of revolutions of the disc system so that when the number of revolutions are multiplied by a meter constant the corresponding amp hr recorded by the meter is obtained. The digital type of the meter is a microprocessor or a micro controller based device capable of interfacing with one or more analog to digital converters (ADC) deriving their inputs from the current sensing devices as required by a single phase or a multiphase system through a multiplexer wilh the processor so programmed that it connects to each of the ADC outputs at a regular interval, reads the instantaneous current magnitude and updates a coxmter by a value i At where i is the sensed value of the current and At is the interval between two consecutive current sampling of the same phase current and stores in a memory the counter reading after suitably scaling it to correspond to a suitable amp -time quantity at regular intervals and facilitates the local and remote reading of the meter's present and past readings that are stored in the memory. The method of estimating the energy losses in a network in terms of the reading of the new meter is as follows: Let the reading of the meter corresponding to a given period be K-Amp hr in all the cases situations considered here. (i) Single Phase System Energy loss = K x R x F kwh (1) where, R is the total resistance of the network (considering both conductors) and F the load distribution factor defined as follows: YkVA^-km F^^ (2) where, L = total length of the network in km P = total connected kVA of the network ^kVA^ -km = Sum of the kVA^ - km of all the segments of the network based on connected load. All the lengths to be considered in the calculation of F in (2) are equivalent lengths such that the resistance per unit length will be R/L. The equivalent length calculation would be necessary only when different types of conductors are used for different segments of the feeder. (ii) 3-phase, 3-Wire system Energy Loss = K X R X F kwh K is obtained using a 3 element \P dt meter or by considering all the 3- phase currents in a digital meter, R is the network resistance per phase. F is computed as in (2) considering total 3-phase quantities instead of single phase quantities. (iii) 3-phase, 4-Wire system Energy Loss = K x R x F kwh Where K, R, F are as defined earlier except that K is obtained using a meter which considers the neutral current also in addition to the three phase currents. The invention is usefiil because it is cost-effective. The induction type of meter would be very cheap to build, robust and easy to deploy. The digital version can be built independently or added as an additional feature into electronic digital energy/current meters. The invention fills a very important gap in the present industry practice and would be highly attractive to them. The load distribution factor is calculated based on the network topology and the connected load data. The factor has to be recalculated if there is a major change in any of them. However, it must be noted that several small changes in load distribution does not affect this factor to any significant extent. Utilities can easily evolve the norms for deciding when this factor is to be updated. I CLAIM: 1. An induction type current square integrating meter for estimation of energy loss in a single phase power distribution network, which comprises of an aluminum disc having two electromagnets 2, 3 placed on either side of the disc, said disc being fixed on a shaft mounted on bearings and is connected to a revolution counter and a display device to record, store and display the total number of revolutions of the said disc, the said disc being made to rotate at a constant velocity proportional to the sqxiare of the current 4,5 that is being suppUed to the electromagnets . 2. A meter as claimed in claim 1, wherein the coils of the electromagnets 2, 3 are energized by currents 4, 5 proportional to the current whose square is to be integrated with the coil circuits so designed such that the two coil currents are in phase quadrature and produce a torque on the disc proportional to the square of the current 1. 3. A meter as claimed in claim 2, wherein the torque produced is made to rotate the said aluminum disc at a constant velocity proportional to the square of the current 1 making use of a braking magnet and a magnetic shunt combination, 4. A meter for estimation of energy loss in three phase electrical power distribution network having 3 wire system comprising the set of electromagnet, brake magnet, magnetic shunts and disc as claimed in claims 1-3 replicated three times with the three discs mounted on a common shaft which is in turn coupled to a single counter-display system. 5. A meter for estimation of energy loss in three phase electrical power distribution network having 4-wire system comprising the set of electromagnet, brake magnet, magnetic sh\mts and disc as claimed in claims 1-3 replicated four times with the four discs mounted on a common shaft which is in turn coupled to a single coimter-display system. 6. A digital type current square integrating meter for estimation of energy loss in a single phase electrical power distribution network comprising a microprocessor /microcontroller interfaced to an analog to digital converter whose input is connected to a current transducer sensing the line current I, and the said microprocessor is programmed to read the current magnitude I as the output of the analog to digital converter at regular intervals and update a counter by a value of 7 ^ At where At is the interval between two consecutive current reading instants, and store the contents of the said counter in a memory to record the readings after suitably scaling it to correspond to a suitable amp -time quantity at regular intervals and to display/communicate the I t readings on demand. 7. A digital type current square integrating meter for estimation of energy loss in a multi phase electrical power distribution network comprising a microprocessor/ microcontroller interfaced through a multiplexer to a number (equal to the number of lines in the multi-phase system) of analog to digital converters whose inputs are coimected to current transducers sensing each of the multi-phase line currents, and the said microprocessor is programmed to read the current magnitude I as the output of each of the analog to digital converters at regular intervals At through a polling scheme and update a counter by a value of / ^ At where At is the interval between two consecutive current reading instants of the same line current, and store the contents of the said counter in a memory to record the readings after suitably scaling it to correspond to a suitable amp^ -time quantity at regular intervals and to display/communicate the I^ At readings on demand.

Documents:

520-che-2004 abstract duplicate.pdf

520-che-2004 claims duplicate.pdf

520-che-2004 description (complete) duplicate.pdf

520-che-2004 drawing duplicate.pdf

520-che-2004-abstract.pdf

520-che-2004-claims.pdf

520-che-2004-correspondnece-others.pdf

520-che-2004-correspondnece-po.pdf

520-che-2004-description(complete).pdf

520-che-2004-drawings.pdf

520-che-2004-form 1.pdf

520-che-2004-form 18.pdf

520-che-2004-form 26.pdf