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:
g1jb1U - 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)
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;
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)+
I = 4,2376A.For phase (3)
I = I=(I1+I2)+j(I1-I2)-I3= (14,55-j12,21+3,76-j7,04)+
=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.
FIELD: electrical and power engineering.
SUBSTANCE: proposed method intended for measuring current and voltage unbalance level and organizing on-line impact on them in three-phase power systems characterized in low quality of their power characteristics includes measurement of unbalance level with respect to reverse and zero sequence of both line and phase voltages and currents at frequency of each harmonic component. Frequency at which unbalance in analyzed characteristics occurs is found. Results obtained are used to generate control signal by correcting devices.
EFFECT: facilitated procedure.
1 cl, 5 dwg
FIELD: power engineering.
SUBSTANCE: method allows to fully utilize power of traction transformer due to loading its free phase by rectifiers and inverters, one of which is lead by leading phase of contact network, and second one of late phase, which allows to transfer electric energy to contact network, to exclude idling mode, to provide for lower asymmetry on reverse series in power grid 220 (110) kV, and also decreases level of higher harmonics.
EFFECT: higher efficiency, lowered values of quality coefficients of electric energy - asymmetry coefficient of reverse series and values of higher harmonics.
FIELD: electrical engineering.
SUBSTANCE: proposed method intended to enhance power quality characteristics for users subject to negative influence of higher harmonic components includes generation of circuit current higher harmonic components which are in phase opposition to higher harmonics of supply mains using electrical energy of independent power supply.
EFFECT: enhanced electrical energy quality characteristics for power consumers.
1 cl, 3 dwg
FIELD: electrical engineering.
SUBSTANCE: proposed method used to enhance quality characteristics of electrical energy supplied to users susceptible to impact of negative factors of electrical-energy higher harmonic components includes generation of higher harmonic components of current in network which are acting in phase opposition relative to higher harmonics of supply mains.
EFFECT: enhanced quality characteristics of electrical energy supplied to users.
1 cl, 3 dwg
FIELD: electric engineering, possible use in power circuits of various equipment.
SUBSTANCE: three-phased balancing device contains input and output clamps of powering networks. To output clamps, three-phased transformer is connected, primary windings of which are oppositely coupled in a zigzag. In accordance to the invention, between input and output clamps of powering network, first three-phased automatic switch is coupled, having an independent release. Serially with primary windings of three-phased transformer, second three-phased automatic switch is coupled. As zero contact for connection of phase loads, zero contact of primary windings of three-phased transformer, coupled oppositely in a zigzag, is used. Control block is connected serially to independent release, coupled between output clamp of one of the phases and zero contact of powering network, and ensures supply of voltage to independent release and activation of first automatic switch on disabling of second automatic switch.
EFFECT: increased reliability when powered from three-conductor or four-conductor powering network.
FIELD: electric engineering, possible use for powering various equipment.
SUBSTANCE: the balancing three-phased to one-phased transformer of alternating voltage contains input and output contacts, to which a transformer is connected which has primary windings in all three phases and two secondary windings in phases A and C. Primary windings are connected in a "zigzag". Windings of phases A and B, B and C, and also C and A are connected respectively. Secondary windings in phases A and C are coupled oppositely and are connected to output contacts.
EFFECT: reduction of stabilized power and asymmetry of primary currents and voltages.
FIELD: power production.
SUBSTANCE: when non-sinusoidal shape of supply voltage is decreased, electric power is distributed between electronic devices distorting the shape of supply voltage and electronic devices improving the shape of supply voltage during the semi-wave of supply voltage. Device is connected in parallel with consumers introducing distortions of voltage shape. Main voltage is supplied to the device input. Device includes serial connection of phase-shifting chain, control pulse shaper, dc power supply and power switcher, which connects consumers improving the shape of supply voltage to the mains at a certain period of time.
EFFECT: improvement of supply voltage shape and simplification of device design.
2 cl, 4 dwg
SUBSTANCE: invention concerns current power transmission equipment, particularly high-voltage power transmission. Device includes reactive shunts connected by reactive switches to line, with additional special reactive shunts connected to the line in star network pattern with unearthed neutral conductor.
EFFECT: enhanced shunt compensation of power transmission line in low load mode, stability and reliability in elimination of single-phase short circuits at single-phase reclosing.
FIELD: electrical engineering.
SUBSTANCE: invention relates to electrical engineering and may be used for hardware designing to improve quality and reduce voltage and electric power losses, when such power is transmitted in three-phase four-wire electric networks due to reduction of anharmonicity and asymmetry. Protection device generates 150 Hz frequency current from phase currents. This current is immediately introduced to harmonics 3 current of neutral working wire in opposite phase.
EFFECT: compensating highest current harmonics flowing along neutral conductor.
2 cl, 2 dwg
FIELD: electrical engineering.
SUBSTANCE: invention relates to electrical engineering, and can be used for phase-to-phase distribution of current in magnetically unstable three-phase signals, for example for neutralisation of zero-sequence harmful effects on current feed circuit in three-phase AC-to-DC and DC-to-AC voltage transformers. Proposed device comprises the transformer with its two phase windings connected, each by one output terminal, to zero input terminal, while their other output terminal is connected to appropriate phase input terminal. The transformer comprises two magnetic cores with phase windings connected in series and furnished with central tap. The said windings have their central and extreme free terminals connected to zero and common phase input terminals, respectively. Note here that central output terminal divides the number of turns in each phase windings into unequal parts, smaller ones being connected to opposing phase input terminals.
EFFECT: possibility to use two single-phase transformers with various-shape magnetic cores instead of three-phase transformer.