SU1494112A1 - Device for automatic control of number of power three-winding transformers of two-transformer substation which operate in parallel - Google Patents

Abstract

The invention relates to electrical engineering, namely to the management of the modes of the power system elements. The purpose of the invention is to reduce active power losses by separately taking into account the full capacity of two independent secondary loads of a substation. The parallel-operating three-winding transformers 5 and 6 are controlled by a device that reacts to the magnitudes of the full power of the two secondary windings of the three-winding transformers that are independent of each other and contains two blocks 7 and 8 of converting the current and voltage into the signal of the full power of the secondary windings. The signal from the conversion unit 7 is fed to the input of the comparison unit 10, and from the conversion unit 8 to the functional converter 9, reproducing a function with a negatively increasing derivative, which is the dependence of the boundary power load of the secondary windings of one voltage on the actual power of the secondary windings of another voltage three-winding transformer. After comparing the two signals in block 10, the signal to turn on or off the transformer directly and through the logical element NOT 11 enters the inputs of the time delay elements 12 and 13, the outputs of which are connected to the executive unit 14. 4 Il.

Description

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

The aim of the invention is to reduce active power losses by separately accounting for the full powers of the two loads of the substation.

(Inr. 1 is a diagram for determining the economic mode of operation of a substation with two three-washing transformers; FIG. 2 - daily schedules of full power on buses of secondary voltage of a substation, where lines 1-4 correspond to the boundary combination of secondary loads, time intervals correspond to the points of intersection of the lines of boundary combinations of secondary loads with curves, their actual values, as well as the daily schedule of operation of three-winding transformers; in Fig. 3, a schematic diagram of the device; Fig. 4 - time mennye diag- paMNfci output signals of the device functional blocks,

A device for automatically controlling the number of parallel operating power three-winding transformers 5 and 6 (FIG. 3) includes the first and second blocks 7 and 8 converting current and voltage into a full power signal, a functional converter 9 of the actual value of the total power of one of the secondary loads to the boundary the full power signal of another secondary substation load, block 10 comparing two analog signals, the logical element NOT II, elements 12 and 3 of the time delay, the execution unit 14,

Fig. 1 shows the boundary line of the combination of secondary loads of three-winding transformers, separating their economical load zones, which corresponds to the minimum active losses in the transformer substations. Based on daily load schedules (4ig, 2), discrete values are given with an interval of 2 hours (from 0 to 24) of the actual combinations of secondary loads and the sequence of their changes, indicating the appropriateness of a particular mode of operation of the substation and the order of their

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alternation. Gra} to the combination of secondary loads -, S- corresponds to the equality of active losses in one and two transformers. The limit value of one of the secondary loads at the corresponding actual value of the other is used in the device as a reference signal.

FIG. Figure 4 shows the time diagrams of the output signals of the Functional Blocks of the device, showing its operation during the day at intervals of 0-t, t - t,. ,, ,, tfl- 24, corresponding to the intersection points of the boundary combinations of secondary loads with their actual values curves figure 2, where / 5t d and the settings for the time to enable and disable, respectively.

Blocks 7 and 8 convert the voltage and total current of the same secondary windings into an analog signal for the load power of these windings. The functional converter 9 is designed to obtain the limit value of the signal for the full load power of the like windings of one of the secondary voltages depending on the signal of the actual load power of the windings of the other secondary voltage. The schematic diagram of this unit, made on semiconductor-resistor elements or analog devices, reproduces the function with a negatively increasing derivative, was a boundary combination of secondary loads of three-winding transformers (figure 1). The comparator unit 10 performs the operation of comparing two analog signals — the limiting S and the actual S „values of the total power of the load of the transformer windings of the same name. The comparison unit is made on analog-discrete devices and is configured in a mode that satisfies the following inequalities:

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The logical element He 11 performs a logical negation operation by generating a disc on the output. the retransmitting signal equal to one, at a zero potential of the input signal and vice versa, the elements 12 and 13

These time ticks are designed to delay a certain control over the 1st interval At p and dt (, the time of the control output signals. The executive unit 14 converts the input control signals into the Enable and Disable commands.

The device works as follows.

Suppose that at a certain moment in time t both power three-winding transformers are turned on. When current signals are supplied to the inputs of block 7) and voltage U (t) from the lower voltage circuit of two transformers, and to the inputs of block 8 current signals i (, (t) and voltage Uc (t) from the windings of the three-winding average voltage The transformers at the outputs of block 7 and 8 generate signals of the total power of the actual loads of the windings of the lower S and average S j-voltages, respectively, the values of which characterize the current load mode of the substation. from his release, soo The corresponding low voltage of the load of the lower voltage windings of the coil winding transformers is fed to the first input of the comparison element 10, and the signal X7 corresponding to the actual load power value of the low voltage windings of the transformers from the output of the block 7 is fed to the second input of the comparison element 10 which performs its comparison with the signal X9, In the intervals t - t; (FIGS. 2 and 4) the measuring signal X7 of block 7 is less than the boundary signal X9 of block 9, i.e. therefore, in accordance with the inequality system, the output signal of block 10 is zero (i.e.). Pr zero potential of the input signal the logical element NOT 11 at the output generates a discrete signal T (i.e.) corresponding to the disconnection of one three-winding transformer. In elements 12 and 13, these signals undergo a temporary shift, and from the output of the execution unit 14 to the substation, the control signal will act to disconnect one three-winding transformer (Y 1). When the load of the substation S + SeT.e increases,

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(time intervals, C (5- according to the system) (P1 neernensg on the block 10 of the block 10 of the discontinuity generates a discrete SIGNS1, corresponding to the inclusion of the sys-format of the transducer (; pa, and the output 11 of the block 11 XI. Interpret 4); This CMenian in elements 12 and 13, these signals are fed to the input of block 14, from which the control signal acts on switching on a three-winding transformer,

The use of two measuring units and functional transducers in a pre-installed device to separately account for control signals proportional to the values of the total power of the secondary windings of the three-winding transformers that are independent of each other, allows determining the limits of the economic modes of operation of these transformers, minimum active power loss and characterized by a different number of transformers included.

Claims (1)

Apparatus of the Invention A device for automatic control of a number of parallel-working power three-winding transformers of a two-transformer substation, comprising current and voltage sensors connected to the input of the first current conversion unit and the voltage to the full power signal, the output of which is connected to the reference unit, is output connected} -, the CIM element is NOT, two time delay elements, the outputs of which are connected to the inputs of the execution unit, characterized in that, in order to reduce losses, the asset By separately taking into account the total power of two independent loads 1x from each other of the secondary loads of the substation, it is equipped with a second current and voltage conversion unit into a full power signal, connected by inputs to current and voltage sensors, with a functional converter of the actual value of the total power of one of the secondary loads to the full-power boundary signal of another secondary load of the gun, the output of which is connected to the second input of the comparator unit, the output (1m connected to the first time delay element) and, 714941128 the input of the second element of the time delay is connected to the terminals for raising; it is connected to the output of the logic switch on the secondary side of the HE, and the current sensors and eg a coil of transformers.