The method of balancing a three-phase load

 

(57) Abstract:

The inventive measure the complexes unbalanced phase currents of the load and the mains voltage. Calculate the conductivity of the balancing element using the above formula. Balancing element has an active-reactive. Depending on the sign of the calculated reactive component of the balancing element can be either active-capacitive and active-inductive. Baluns connected to phase voltage three-phase network.

The invention relates to electrical engineering and can be used for balancing a three-phase loads and networks, asymmetry which is due to the operation of single-phase and three-phase unbalanced loads.

Known methods for balancing unbalanced three-phase networks and loads [1,2] . These methods mainly balancing system unbalanced currents and voltages using either rational distribution (uniform) loads on phases, or using managed and unmanaged capacitive and inductive balancing devices depending on the nature of the graph loads.

Closest to the proposed method according to the th component of the currents, stress, etc.

Disadvantages of these methods are that they are complex, require high economic costs due to the use of three-phase balancing device at balancing three-phase networks.

The purpose of the invention is to simplify the balancing unbalanced three-phase loads and networks. This method allows you to quickly and inexpensively determine the magnitude of the balancing item for any pre-selected phase and include it only in this phase, to prevent reverse its component in the whole unbalanced three-phase network. The obtained values of the balancing item, which involved when determining the parameters of all three phases, determine the most economical design balancing element.

The objective is achieved by the fact that in this method of balancing a three-phase load, which consists in measuring quantities and arguments unbalanced phase currents load voltage three-phase network, the calculation of the values of the conductances of balancing elements and the connection of balancing elements to the three-phase network with the calculated values of conductivity, which is calculated by the following formula:

g1jb1
U - voltage three-phase network;

that is, complexes of phase currents unbalanced load, index 2 means the look-ahead phase, and the index 3 is lagging phase with respect to the selected phase 1 connects balancing element.

The generalized equation (1) in complex form in the expanded view will look like:

(2) or similar (1)

(3)

Found balancing element can be either active-capacitive or active-inductive; it depends on the size and nature of the loads in phases. The generalized formula is always able to determine alternative values of balancing elements in relation to the selected phase. The absolute values found using the generic formulas (1) and (3) will always be equal to

| I1| = | I2| = | I3|,

|g1b1|= |g2b2|= |g3b3|; integrated their values are not equal

g1jb1g2jb2g3jb3.

In the design process of balancing element value of the element is calculated using the generalized formula (1) and be included in the selected phase to exclude reverse component should Ave the/SUP>IB+aI40A;

IB=I2=862A;

IC=I3=1117A;

UA=UB=UC=220B.

2. Balancing current load is determined by the formula (1)

I = I=(I2+I3)+j(I2-I3)-I1= (3,76-j7,04+10,56-j3,19)+

+j(3,76-j7,04-10,56+j3,19)-14,55+j12,21 = -4,06+j1,2 A,

I= 4,2316A. As can be seen from the result, the obtained value with a negative sign in front of a real part of a complex number is not meaningful.

You can get alternative is balancing element according to the General formula (1) for other selected phase, for example phase (2)

I = I=(I3+I1)+j(I3-I1)-I2= (10,56-j3,19+14,55-j12,21)+

+j(10,56-j3,19-14,55+j12,21)-3,76+j7,04=0,99-j4,2 A,

I = 4,2376A.

For phase (3)

I = I=(I1+I2)+j(I1-I2)-I3= (14,55-j12,21+3,76-j7,04)+

+j(14,55-j12,21-3,76+j7,04)-10,56+j3,19=3,07+j2,91 A,

=4,2343A.

Thus, for balancing a three-phase network (load), you must enable phase In the active-inductive balancing element, either in phase With active - capacitive

g2-jb2= = 0,0045-j0,0187 Cm;

g3+jb3= = 0,014+j0,013 Cm.

Included is matrimonio unbalanced three-phase network (load), i.e., the geometric sum of the actual value of the integrated value of current in the phase In (C) and the magnitude of the balancing item will reverse component of the sequence to zero. The check is performed on the value of the numerator is obtained by the generic formula (1).

Phase

I2= (IB+a2IC+aIA) = (I2+(I-jI)+a2I3+aI1) =

= (3,76-j12,21+(0,99-j4,12)+(- -j)(10,56-j3,19) +

+ (is +j)(14,55-j12,21) = 0.

Phase

I2= (IC+a2IA+aIB) = (I3+(I+jI)+a2I1+aI2) =

= (10,56-j3,19+(3,07+j2,91)+(- -j) (10,56-j3,19) +

+ (is +j)(14,55-j12,21) = 0. As follows from the examples, obtained by balancing the elements: active-inductive included in the phase or active-capacitive included in phase With, in both cases, the result of a three-phase network (load) to zero.

The METHOD of BALANCING a three-PHASE LOAD, which consists in measuring quantities and arguments complexes unbalanced phase currents of the load, the voltage measurement three-phase network, the calculation of the values of the conductances of balancing elements and the connection of balancing elements to the three-phase network with the calculated values of conductivity, characterized in that order uprochnennoi network;

complexes of phase currents unbalanced load;

index 2 - anticipatory phase;

index 3 - lagging phase with respect to the selected phase 1 connects balancing element with active g1and jet b1components of the conductivity, and if the reactive conductivity b1> 0, then the element is capacitive, and if b1< 0, then inductive.

 

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