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Title:
METHOD FOR MEASURING TWO-PHASE ENERGY
Document Type and Number:
WIPO Patent Application WO/2017/168434
Kind Code:
A1
Abstract:
A method for measuring two-phase energy is disclosed. The present method of measurement, measures the power as V*I as against the actual power of 1.15 *V*I which accounts for the error factor.

Inventors:
KHADE, Suresh Pandurang (103 Gomati CHS, Suchidham Gen A K Vaidya Marg,Malad Mumbai, Maharashtra 7, 400097, IN)
Application Number:
IN2016/050284
Publication Date:
October 05, 2017
Filing Date:
August 26, 2016
Export Citation:
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Assignee:
KHADE, Suresh Pandurang (103 Gomati CHS, Suchidham Gen A K Vaidya Marg,Malad Mumbai, Maharashtra 7, 400097, IN)
International Classes:
H01L21/00; G01R22/00; G05D23/00; H02P8/00
Foreign References:
US4568821A1986-02-04
US6141626A2000-10-31
Attorney, Agent or Firm:
SAWANT, Prajakta (Plot No. 360 A, Sector 31A Near Kerala House,Vashigaon, Vashi, Navi Mumbai, Maharashtra 3, 400703, IN)
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Claims:
CLAIMS:

1. A correct method for measuring two-phase energy, said method comprising the following steps:

• The two-phase energy is 1.15*V*I and is considered so far as measured correctly by three phase meters.

• It is found by experiments that the meter measures 15% less energy than actually consumed.

• As indicated in the summary , the meter senses the three phase with voltage as V/V3

• The error factor of 15% needs to be accounted for the correct measurement of energy.

The method as claimed in claim 1, wherein measurement of two phase energy/ power has an error of 15%.

The method as claimed in claim 2, wherein said error factor at least partly accounts for the energy transmission and distribution losses.

The method as claimed in claim 1, wherein said method for measuring two- phase energy is applicable for a 25 kV traction system.

The method as claimed in claim 1, wherein the energy recorded is 15% less than that consumed which is a loss of revenue to electric supply company.

The method as claimed in claim 1, wherein the three phase energy meters used for measuring two phase power needs to have a multiplying factor to take care of 15% energy not getting recorded.

Description:
METHOD FOR MEASURING TWO-PHASE ENERGY

FIELD OF INVENTION

The present invention relates to a method for measuring two-phase energy. BACKGROUND

The electric energy industry occupies a significant place in a country's GDP (gross domestic product). The significance of accurate electric energy measurement is distinctly the key for constructing an efficient energy management system. Also, accurate measurement of electric power and energy is important for an ever-growing industrial economy.

Today, worldwide, railways are among the largest consumers of electric energy. The railway trains run by electric locomotives require significant capital expenditure for the energy supply. The railway electrification systems commonly use 25 kV alternating current electrification.

The traction power uses a 25 kV system. Traction supply to the railway use only two phases of the normal three-phase supply. The energy in the 25 kV traction system is measured by three phase meters. The 25 kV traction system uses two phases for the measurement of energy and in addition, PT earth is connected to the energy meter. This traditional method of measurement of energy in the two phase systems is inaccurate and faulty. The present invention is directed to a method for accurately measuring two phase energy, typically in a 25 kV traction system, which method will overcome afore-noted drawback in the traditional method. SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a method for measuring two-phase power or energy, which is accurate, simple and economical. Other aspects, objects and advantages of the present invention will be apparent from the following description.

Accordingly, in accordance with the present invention, there is disclosed a method for measuring two-phase energy, said method comprising the following steps:

- The method now adopted assumes that a three-phase wattmeter arrangement measures the two phase power. The method assumes that power for one phase will be V P * I P and hence for the two phases the power will be 2* V P * I P where V P & I P are the phase voltage and phase currents. Either line voltage or line current will be same as its phase value. Assuming that a star connection, phase and line currents would be same or I . The V P , the phase voltage will be V/V3 . With this 2* V P * Ip will be 2* (v 3)* I

or about 1.15*V*I .

But it is found by experiments that the energy consumed by two phase circuits is 15% more than that gets recorded. From this it is apparent that the power recorded by the meter is V*I and NOT 1.15V*I as believed.

This can be explained if two phases and a neutral are considered as three phases. The current coils are in phase wires and voltage coils are connected between phase and neutral, as shown in the figure. The meter therefore considers the input as three phase inputs with voltage as V/V3 giving the power as Λ/3* V/V3* I or V*I which give rise to an error factor of 15%. The pf is considered as unity.

Typically, the method comprises accounting an error factor of about 15%. The said error factor at least partly accounts for the energy transmission and distribution losses. The method of the present invention is applicable for measuring two-phase energy for a 25 kV traction system.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

The present invention will be described here below with reference to the following drawing, in which,

FIGURE 1 illustrates a circuit diagram showing the method for measuring two-phase energy, in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting examples in the following description. The examples used herein are intended merely to facilitate an understanding of the ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The present invention envisages a method for measuring two phase energy. Typically, the method is suitable for measuring energy in the 25 kV traction system used in electrification systems for electric locomotives by the Railways. Referring to FIG. 1, therein is disclosed a circuit diagram showing the method for measuring two phase energy in accordance with the present invention. The energy in the 25 kV traction systems is measured by three phase meters. The circuit diagram (100) shows the connection of the three phase energy meter (102) with the load (104) to measure the two phase power, where the wire N is at earth potential.

PRESENT METHOD

The circuit diagram shows how the three phase energy meter can be connected to measure two phase energy, the wire N is at earth potential. It is presumed till now that with above connection, the power per phase gets recorded. The meter adds the power in two phases to give out power in two phases. If the phase voltage and phase current are V p & I P , the per phase power will be V p * I P , the power in two phases will be 2* V p * Ip , the V p =V/V3, V is the line voltage I P will be the line current I. The two phase power therefore works out to, 2* (V/V3) * I or 1.15*V*I

This is considered as the power measured by a three phase meter while measuring two phase power.

MODIFIED APPROACH

Figure 1 indicates that the connection is similar to two watt meter method. The meter considers the two phases and a neutral as a three phase system with phase to phase voltage or line voltage as V/V3,

In this case the meter will read the power as, It is presumed so far that the power measured is 1.15*V*I , where as the meter will measure it as V*I, 15% less than what we assume.

Since the meters we use cannot detect this error, a very simple method was used.

The error factor was calculated as follows. The experiment here below is exemplary and shall in no way limit the scope and ambit of the invention.

The experiment included heating of twenty kilos of water each with single phase and two phase power. Equal amount of single and two phase energy was passed in the water. The energy was measured by single and three phase meter. Two phases and a neutral were connected to a three phase meter to measure the two phase energy. Though, the temperature rise with same energy input from a single and two phase source should be identical, however, the temperature rise with the two phase system was found more by about 15%.

The same meter was used for the single and two phase measurements. 1280 pulses were equivalent to IKWh for the meter used. For 100 pulses the temperature rise in case of single phase was found to be (66 - 32) = 34 deg C, and in case of two phase it was found to be (67 - 28) = 39 deg C. The temperature rise in case of two phase was 5 degrees more or about 14.7% more for the same energy supplied. Thus, an error factor of about 15% must be included while calculating the two phase energy using a three phase four wire energy meter to obtain accurate measurements.

Embodiment of the present invention is applicable over a wide number of uses and other embodiments may be developed beyond the embodiment discussed heretofore. Only the most preferred embodiments and their uses have been described herein for purpose of example, illustrating the advantages over the prior art obtained through the present invention; the invention is not limited to these specific embodiments or their specified uses. Thus, the forms of the invention described herein are to be taken as illustrative only and other embodiments may be selected without departing from the scope of the present invention. It should also be understood that additional changes and modifications, within the scope of the invention, will be apparent to one skilled in the art and that various modifications to the construction described herein may fall within the scope of the invention.