SU1644295A1 - Automatic device to control double-wound power transformers at two-transformer substations - Google Patents

Abstract

The invention relates to the control of the modes of the power system elements and is intended for the automatic control of the number of separately operating power two-winding transformers of two transformer substations. The purpose of the invention is to reduce active power losses by separately taking into account the currents of transformer loads and determining the minimum power losses in transformers. The number of separately operating power two-winding transformers is controlled using a device that implements an algorithm for determining the minimum power loss in transformer substations in adjacent modes of operation and contains two current transformers for voltage 1 and 2, to the inputs of which a signal is supplied from the load current pickups of two transformers, and from the outputs through the first and second chains of series-connected quadres 3.1,4.1 and 5 1 and multiplication blocks 3.2, 4.2 and 5.2. Signals proportional to the loss of power The cores in the first and second transformers arrive at the first and second inputs of the summation unit 7, and the third input receives a signal from the setpoint parameter of the transformer 8, the output from the summation unit, a signal proportional to the power loss in two separately working transformers, goes to the second input of the unit Comparison 9 for comparison with a signal from the output of the first computational circuit and proportional power losses in one transformer, moreover, at the output of the comparator unit (depending on the ratio, comparing proxy signaling) gave zero or logic unit control signal which directly or through the NAND gate 10 enters the shutter time elements outputs 11 and 12, wherein undergoes temporal offset and input to the execution unit 13, generating Enable, Disable. 4 il. About 4 4 U CHE

Description

The invention relates to the control of the modes of power system elements and is intended for automatic control of the number of separately operating power two-winding transformers of two transformer substations.

The purpose of the invention is to reduce active power losses by separately taking into account the currents of transformer loads and determining the minimum power losses in transformers.

Figure 1 shows diagrams for determining the economic mode of a substation with two separately operating double-winding transformers; on figa - daily graphs of loads of transformers; Fig. 26 is a daily chart for the switching of transformers; FIG. 3 is a schematic diagram of the device; figure 4 - timing diagrams of the output signals of the functional blocks.

Figure 1 shows the line of the boundary combination of loads of separately operating double-winding transformers, dividing the zone of their economical loads, which corresponds to the minimum active losses in transformers of the substation. The boundary combination of transformer loads corresponds to the equality of active losses in a higher power transformer (mode a) and two separately operating transformers (mode b). Figure 2a shows daily graphs of transformer loads, lines I, II, III, IV, corresponding to their boundary combination, as well as the time intervals tKiv corresponding to the coincidence of the boundary and actual combinations of loads of transformers of the substation; Fig. 2b is a graph of the operation of transformers 1T, 2T, which are controlled by the device (for the case of setting the time delay blocks to zero). Fig. 3 shows a schematic diagram of a substation with two separately operating transformers indicating the secondary circuits of current transformers to which the proposed device is connected and a functional diagram of the device that has current conversion voltage units 1.2, computing units 3-5, which contain quadratures 3.1, 4.1, 5.1, multiplication blocks 3.2,4.2, 5.2 and resistance adjusters of the transformer 1Т 3.3 and transformer 2Т 5.3, two adders 6 and 7, setpoint for no-load losses of the transformer 2Т 8, comparison unit 9, logical element 10 is NOT 10, elements of time delay 11, 12 and executive unit 13. Figure 4 shows time diagrams of output signals (Xg-Xia) of functional blocks of the device, showing its operation during the intervals of days 0-ti, t | -tn, til-tin, tm-tiv, which correspond to the alternation of the zone of economic modes of operation of the substation, where AtB ID to set-up time for switching on and turning off, respectively.

Conversion units 1.2 are used to convert the load current signals of two transformers to a voltage (Xi (2) h (2)). The summing unit 6 is designed to sum the signals proportional to the load currents Hb (H2).

The squares 3.1,4.1, 5.1 allow to get the output signals proportional to the square of the input signals of these circuits (Хз.1 (H-l2) 2, Hl.1 I2. X51 I22. And blocks

multiplying 3.2,4.2,5.2 - signals, respectively, equal to Хз.2 () 2 X42 И2,. The magnitudes of the signals proportional to the resistances of transformers IT, 2T are set by the resistance control knobs 3.3 and 5.3, respectively (Xs., HB.C. R2), and the signal proportional to the no-load loss of the 2T transformer is set by the adjuster 8 (Xe Pc2). Adder 7 is designed to add incoming signals at its inputs X - l22 R2 Pea). Comparison unit 9 performs the operation of comparing two analog signals proportional to the power loss in the single mode.

transformer 1Т Хз.2 Ri (f H2) 2 and power losses in the separate operation of two transformersX (h Ri-lz). The comparison unit is executed on analog-discrete devices and is configured in

mode that satisfies the following conditions:

Hd 1 Хз.2 Х7 Хэ 0 Хз.2 X The logical element NOT 10 performs

logical negation by generating a discrete signal at the output equal to one at zero potential of the input signal and vice versa. The elements of time delay 11, 12 are intended for

delays by an adjustable interval (Ate, Ato) of control output signals. Executive unit 13 converts the input control signals into On and Off commands.

The device works as follows.

At a certain point in time t, two power transformers are connected separately. When applying to the input unit 1 signal

the load current of the transformer 1T h (t), and the input of the signal block of the load current transformer 2T i2 (t), at the outputs of blocks 1.2, receive voltages proportional to these currents, which in block 6 are summed.

A signal proportional to the sum of the load currents of the Xe transformers, as well as signals proportional to the load currents of the transformers Xi and Xa, are fed to the inputs of the computing blocks 3-5, where arithmetic operations are performed (squaring and multiplying with the signal proportional to the resistance of the corresponding transformer ). From the output of blocks 4.5 and 8, the signals arrive at

block 7, where their addition occurs. From the output of the block, the signal proportional to the value (I2 Rt + 2 R2 + Pc2) is fed to the input of block 9, which compares it with the signal Hz.2, which is proportional to the value (H + te) Ri. In the time interval 0-ti. tii-tm, (see FIG. 2), the signal Xs.2 is smaller than the signal X, therefore, according to the inequality system, the output signal of block 9 is zero (Xd 0). At zero potential of the input signal, the logical element NOT 10 at the output generates a discrete signal 1 (Hu 1), corresponding to the disconnection of one transformer. In elements 11, 12, these signals undergo a temporary shift and, from the output of the executive unit 13 to the substation, a control signal affects the switching off of one transformer and the subsequent switching on of the sectional switch (Tcl. 1). With increasing load substation Sn or Sia. those. when (h + te) 2 Ri (I2 RI + + 22 R2 + PC2) time intervals t | -tii, tui-tiv, in accordance with the system of inequalities, at the output of the comparison unit 9 a discrete signal Xe 1 is generated, corresponding to the switching on of another transformer, and output of unit 10 Huy 0. Having undergone a temporal displacement in elements 11, 12, these signals fall on the input of the execution unit 13, from the output of which the control signal affects the switching on of another transformer and the subsequent disconnection of the section switch. The control signal for switching on another transformer can also come from transformer protection devices against overload if the duration and magnitude of the load current of the transformer exceeds the permissible values (see Fig. 1) of the maximum load line Zdop together with the boundary combination line of the transformer loads section areas of economic work of the substation).

The use in the proposed device of two current-to-voltage converters, three computational units, control units of transformer resistances and losses of a single transformer 2T, two adders allows with high accuracy

to implement the algorithm of determination; the boundary combination of loads of separately operating double-winding transformers, followed by an indication of their economical operation modes, corresponding to the minimum active power loss and characterized by a different number of transformers included.

Claims (1)

Apparatus of the Invention A device for automatically controlling the number of power double-winding transformers of a two-transformer substation, comprising a conversion unit connected to a load current sensor of a transformer, an adder, a comparison unit whose output is connected to a logical element HE, two time delay elements whose outputs are connected to the inputs of execution units, characterized in that, in order to reduce active power losses by separately taking into account the loads of transformer loads and determining the mini mad and in transformers, it is equipped with a second conversion unit connected to the load current sensor of the second transformer, three quadrants, three multiplication blocks, the inputs of which include transformer resistance sensors, a second adder, to the input of which the transformer idling loss converter is connected the conversion blocks are made with the function of converting current to voltage, the outputs of the first conversion block are connected through the first adder to the first quad and directly These are the second and third quadrants, respectively, the outputs of the second conversion unit are connected to the first adder and the third quadrants, the outputs of the three quadrants are connected to the inputs of three multiplication units, respectively, the outputs of the first multiplication unit are directly connected to the inputs of the second unit , the second output of which is connected to the time delay element, and the output of the logic element is NOT connected to the input of the second time delay element. 8-L 100 100200 300WD 50О 600700Хб А .k6L wo350 500 250 gao 150 Iod so o F (/ g / i h you ng "°) CH L. . v Ф г.2 № go 21 14 U, 6kl2T , /, , , / 0