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Three-phase three-wire system phase voltage measuring method

A measurement method, three-phase three-wire technology, applied in measuring devices, measuring electrical variables, measuring current/voltage, etc., can solve problems such as potentials that are not equal to the actual ground

Inactive Publication Date: 2011-08-24
FUJIAN NORMAL UNIV
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Problems solved by technology

The essence of the method published in this patent is to connect three sets of symmetrical resistors from the power grid under test in a star-shaped (also known as Y-shaped) connection for measurement, which includes the use of voltage division to attenuate the signal and filter it with a capacitor. As a sampling; because the three-phase three-wire grid has no neutral line (zero line), the common access point of the three sets of resistors is essentially a fictitious ground. When the three-phase voltage of the grid is unbalanced (that is, the amplitude is not equal), The potential of the imaginary ground will not be equal to the potential of the actual ground, so this method will introduce a principled measurement error

Method used

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Embodiment Construction

[0024] Below in conjunction with Fig. 2, the principle and implementation steps of the technical solution of the present invention are further described, and the small triangle △AOB, △BOC, △COA are respectively applied to the law of cosines to obtain the following three relational expressions:

[0025]

[0026]

[0027]

[0028] The left and right sides of the equal signs of the three expressions are reversed and arranged:

[0029]

[0030]

[0031]

[0032] Suppose half of the perimeter of the large triangle △ABC is denoted by L, that is

[0033]

[0034] According to the formula for calculating the area of ​​the known triangle side length, the area S of the large triangle △ABC is

[0035]

[0036] The areas of the three small triangles △AOB, △BOC, △COA can be expressed as

[0037] , ,

[0038] The area of ​​the large triangle △ABC is equal to the sum of the areas of the three small triangles △AOB, △BOC, △COA, namely

[0039] , sorted o...

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Abstract

The invention relates to a three-phase three-wire system phase voltage measuring method, in particular to a measuring method by a digital integrated electric parameter measuring system by aiming at phase voltages in a three-phase three-wire system connection method. The invention has the technical scheme that the method comprises the following steps: 1. testing three wire voltages UAB, UBC and UCA; 2. calculating the half L of the algebraic sum of the three wire voltages; 3. calculating the area S of a triangle using the three wire voltages as the lengths of three edges; 4. calculating the sum m of the three phase voltages to be measured; and 5. obtaining the respective phase voltages UA, UB and UC of the three phase wires against the ground through calculation. The invention has the advantages that the measuring method has no theoretical error, is applicable to any electric parameter measuring system with the digital operation function, and can calculate the phase voltages on the basis of the measured wire voltage without increasing any hardware circuit cost.

Description

technical field [0001] The invention relates to a phase voltage measurement method of a three-phase three-wire connection method, in particular to a phase voltage measurement method for a three-phase three-wire connection method of a digital comprehensive electrical parameter measurement system. Background technique [0002] Monitoring the AC parameters at the end of the electrical equipment is of great significance to the safe operation of the equipment, the traceability of the accident, and the power distribution of the power grid. Phase voltage is one of many AC parameters. Its measurement method is related to the wiring method of electrical equipment. The power line connection method of three-phase electrical equipment is divided into three-phase three-wire system and three-phase four-wire system. Three-phase three-wire system The line voltage of the connection method can be directly measured and calculated, but the phase voltage cannot be directly measured because there...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R19/00
Inventor 廖晓东洪亲林潇
Owner FUJIAN NORMAL UNIV
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