RU87536U1 - DEVICE FOR OPERATIONAL CONTROL OF RESISTANCE OF A SHORT CLOSING OF A SINGLE-PHASE DOUBLE-WISE TRANSFORMER IN OPERATING MODE - Google Patents

Abstract

A device for operational monitoring of short circuit resistance of a single-phase double-winding transformer in operating mode, characterized in that it contains an electrical signal recorder whose outputs are connected in series with the input of the unit for calculating the effective values of the current of the secondary winding and the inputs of the unit for calculating the effective values of the voltage of the primary and secondary windings; the output of the unit for calculating the effective values of the current of the secondary winding is connected to the input of the unit for calculating the short circuit resistance of the transformer; one of the outputs of the unit for calculating the effective values of the voltages of the primary and secondary windings is connected to the input of the drive unit and the third input of the unit for calculating the phase angle between the voltages of the primary and secondary windings, the other output of the unit for calculating the effective values of the voltages of the primary and secondary windings is connected to the input of the unit for calculating the voltage drop and the fourth input of the block for calculating the phase angle between the voltages of the primary and secondary windings; the first and second inputs of the block for calculating the phase angle between the voltages of the primary and secondary windings are connected to the corresponding outputs of the recorder of electrical signals, the output of the block for calculating the angle of the phase shift between the voltages of the primary and secondary windings is connected to one of the inputs of the block for calculating the voltage drop, the output of the cast unit is connected to the input of the voltage drop calculation unit, the output of the voltage drop calculation unit is connected to the input of the transformer short circuit resistance calculation unit, the other input of which connected to the output of the control unit changes the frequency, the input of block

Description

The utility model relates to the field of electromechanics, namely, to the use of information processing tools in electromechanics, and can be used for operational monitoring of short-circuit resistance of a single-phase double-winding transformer in operating mode.

A known device for monitoring the internal windings of power transformers [A.S. USSR No. 1221620, G01R 31/02, publ. 03/30/1986. Bull. No. 12], selected as a prototype, contains the first and second voltage transformers, clamps for connecting the primary and secondary windings of the controlled transformer, current transformer, first and second intermediate transformers, a voltmeter, ammeter and frequency meter, and clamps for connecting the primary and secondary windings of the controlled power transformer connected to the primary windings of the first and second voltage transformers, respectively, the secondary windings of which are connected to the primary windings of the first of the second and second intermediate transformers, the secondary windings of which are connected in series, opposite to each other and in series with a voltmeter, a current transformer is installed on the secondary side of the monitored power transformer, an ammeter is connected in parallel with it, a frequency meter is connected in parallel with the terminals for connecting the secondary winding of the monitored power transformer.

The disadvantages of the known device:

- the presence of additional intermediate transformers, which greatly complicates the installation of the device, increases its size and cost;

- the use of intermediate transformers can lead to the appearance of additional instrumental errors caused by losses in these transformers;

- at non-sinusoidal currents and voltages, the type of measuring instruments used (voltmeters and ammeters) will influence the result of the calculations, which can lead to an increase in the total instrumental error.

The objective of the proposed utility model is the creation of a device for the operational control of the short circuit resistance of a single-phase double-winding transformer in operating mode.

The problem is solved due to the fact that the device for operational control of short circuit resistance of a single-phase double-winding transformer in operating mode, as well as a prototype, is connected to the secondary windings of the first and second voltage transformers, the primary windings of which are connected to the primary and secondary windings of the controlled transformer, and to the secondary winding of a current transformer, the primary winding of which is included in the secondary circuit of the controlled transformer.

Unlike the prototype, the proposed device contains an electrical signal recorder, the outputs of which are connected in series with the input of the unit for calculating the effective values of the current of the secondary winding and the inputs of the unit for calculating the effective values of the voltages of the primary and secondary windings. The output of the unit for calculating the effective values of the current of the secondary winding is connected to the input of the unit for calculating the short circuit resistance of the transformer. One of the outputs of the unit for calculating the effective values of the voltages of the primary and secondary windings is connected to the input of the drive unit and the third input of the unit for calculating the phase angle between the voltages of the primary and secondary windings. The other output of the unit for calculating the effective values of the voltages of the primary and secondary windings is connected to the input of the unit for calculating the voltage drop and the fourth input of the unit for calculating the phase angle between the voltages of the primary and secondary windings. The first and second inputs of the block for calculating the phase angle between the voltages of the primary and secondary windings are connected to the corresponding outputs of the recorder of electrical signals. The output of the block for calculating the angle of phase shift between the voltages of the primary secondary windings is connected to one of the inputs of the block for calculating the voltage drop. The output of the cast unit is connected to the input of the voltage drop calculation unit. The output of the voltage drop calculation unit is connected to the input of the transformer short circuit resistance calculation unit, the other input of which is connected to the output of the frequency change control unit. The input of the frequency change control unit is connected to the output of the network frequency measuring device. The output of the transformer short circuit resistance calculation unit is connected to the input of the data acquisition and transmission device.

Thus, the proposed device allows to obtain information about the values of the short circuit resistance of the transformer in operating modes, both with sinusoidal and non-sinusoidal currents and voltages.

Figure 1 - shows a hardware diagram of a device for operational control of short circuit resistance of a single-phase double-winding transformer in operating mode.

The outputs of the electrical signal recorder 1 (RES) connected through a switch to current and voltage transformers of the measurement circuit of a double-winding transformer (not shown in Fig. 1) are connected in series with the input of the unit for calculating the effective values of the current of the secondary winding 2 (BRT) and the inputs of the unit for calculating the effective values voltages of the primary and secondary windings 3 (BRN). The output of the unit for calculating the effective values of the current of the secondary winding 2 (BRT) is connected to the input of the unit for calculating the short circuit resistance of transformer 4 (BRS). One of the outputs of the unit for calculating the effective values of the voltages of the primary and secondary windings 3 (BRN) is connected to the input of the casting unit 5 (BPR) and the third input of the unit for calculating the phase angle between the voltages of the primary and secondary windings 6 (BRF). The other output of the unit for calculating the effective values of the voltages of the primary and secondary windings 3 (BRN) is connected to the input of the unit for calculating the voltage drop 7 (BRPN) and the fourth input of the unit for calculating the phase angle between the voltages of the primary and secondary windings 6 (BRF). The first and second inputs of the block for calculating the phase angle between the voltages of the primary and secondary windings 6 (BRF) are connected to the corresponding outputs of the electrical signal recorder 1 (RES). The output of the unit for calculating the angle of phase shift between the voltages of the primary and secondary windings 6 (BRF) is connected to one of the inputs of the unit for calculating the voltage drop 7 (BRF). The output of the casting unit 5 (BPR) is connected to the input of the unit for calculating the voltage drop 7 (BRPN). The output of the unit for calculating the voltage drop 7 (BRPN) is connected to the input of the unit for calculating the short circuit resistance of the transformer 4 (BRS), the other input of which is connected to the output of the control unit for changing the frequency 8 (BCF). The input of the frequency change control unit 8 (BCH) is connected to the output of the network frequency measuring device, which is not part of the device (not shown in Fig. 1). The output of the short circuit resistance calculation unit of the transformer 4 (BRS) is connected to a data acquisition and transmission device (not shown in FIG. 1).

As the recorder of electrical signals 1 (RES) can be selected digital recorder of electrical signals of the type "Parma" or "Black box". The unit for calculating the effective values of the current of the secondary winding 2 (BRT), the unit for calculating the effective values of the voltages of the primary and secondary windings 3 (BRN), the unit for calculating the short circuit resistance of the transformer 4 (BRS), the drive unit 5 (BPR), the unit for calculating the phase angle between voltages of the primary and secondary windings 6 (BRF), the unit for calculating the voltage drop 7 (BRF) and the control unit for changing the frequency 8 (BCF) can be performed on the Atmel AT89S8253 series 51 microcontroller.

In the operating mode of the transformer, when its primary winding is connected to an AC voltage source with a known frequency, measured using a frequency measuring device, and the load is connected to the secondary winding, using the electrical signal recorder 1 (RES) in the operating mode for the same moments time register arrays of instantaneous voltage values at the input and output of the transformer and current in the secondary winding of the transformer with a certain discreteness in time Δt, corresponding to the number of samples per period e N.

From the output of the electrical signal recorder 1 (RES) an array of instantaneous values of the secondary current enters the input of the unit for calculating the effective values of the current of the secondary winding 2 (BRT), in which the array of instantaneous current values determines the effective value of the current of the secondary winding

,

where N is the number of samples of instantaneous values on the current period;

From the output of the unit for calculating the effective values of the current of the secondary winding 2 (BRT), the effective value of the current of the secondary winding I _{2 is} fed to the input of the unit for calculating the short-circuit resistance of the transformer 4 (BRS).

At the same time, from another output of the analog-to-digital converter of the electrical signal recorder 1 (RES) an array of instantaneous values of the primary winding voltage comes to one of the inputs of the unit for calculating the effective values of the voltages of the primary and secondary windings 3 (BRN) and the first input of the unit for calculating the phase angle between the voltages of the primary and secondary windings 6 (BRF), and an array of instantaneous values of the voltage of the secondary winding from the corresponding output of the electrical signal recorder 1 (RES), it goes to the other input of the unit for calculating the effective values of the voltages of the primary and secondary windings 3 (BRN) and to the second input of the unit for calculating the phase angle between the voltages of the primary and secondary windings 6 (BRF).

Then, in the block for calculating the effective values of the voltages of the primary and secondary windings 3 (BRN) by arrays of instantaneous values of the voltages of the primary and secondary windings , determine:

- the effective value of the voltage of the primary winding:

,

where N is the number of samples of instantaneous values on the voltage period;

- the effective value of the voltage of the secondary winding:

From the outputs of the unit for calculating the effective values of the voltages of the primary and secondary windings 3 (BRN), the effective value of the voltage of the primary winding U _{1 is} fed to the input of the casting unit 5 (BPR) and the third input of the unit for calculating the phase angle between the voltages of the primary and secondary windings 6 (BRF), and the actual value of the voltage of the secondary winding U ₂ goes to the input of the unit for calculating the voltage drop 7 (BRPN) and to the fourth input of the unit for calculating the phase angle between the voltages of the primary and secondary windings 6 (BRF).

At the same time, information on the value of the network frequency f _m measured during the registration of arrays of instantaneous values of currents and voltages is received from the output of the network frequency measuring device to the input of the frequency change control unit 8 (BCF) , , .

In the control unit for changing the frequency 8 (BCH), the ratio of the measured network frequency to the nominal frequency value f _{nom is} determined:

.

From the output of the control unit for changing the frequency 8 (BCF), the value of the ratio of the measured network frequency to the nominal value of the frequency f ' _{pu is} supplied to one of the inputs of the block for calculating the short-circuit resistance of transformer 4 (BRS).

Further, in the block for calculating the phase angle between the voltages of the primary and secondary windings 6 (BRF) for arrays of instantaneous voltage values of the primary and secondary windings , and the current values of the voltages of the primary and secondary windings U ₁ , U ₂ determine the magnitude of the phase angle between the voltages of the primary and secondary windings of the transformer:

From the output of the block for calculating the phase angle between the voltages of the primary and secondary windings 6 (BRF), the value of the phase angle between the voltages of the primary and secondary windings of the transformer φ _{U1 U2 is} supplied to the corresponding input of the unit for calculating the voltage drop 7 (BRF).

At the same time, in the casting unit 5 (BPR), the effective value of the voltage of the primary winding is brought to the secondary circuit using the casting coefficient K _PR , taken equal to the transformation coefficient from the technical data sheet of the transformer or transformer test report

U ' ₁ = K _PR · U ₁

From the output of the casting unit 5 (BPR), the reduced value of the effective voltage of the primary winding U ' _{1 is} supplied to the input of the unit for calculating the voltage drop 7 (BRPN).

Next, from the values of the effective value of the voltage of the secondary winding U ₂ , the reduced effective value of the voltage of the primary winding U ' ₁ and the phase angle between the voltages of the primary and secondary windings φ _{U1 U2} , the effective value of the total voltage drop on the primary is determined in the unit for calculating the voltage drop 7 and secondary windings

.

From the output of the unit for calculating the voltage drop 7 (BRPN), the effective value of the total voltage drop on the primary and secondary windings ΔU _{12 is} fed to the input of the unit for calculating the short circuit resistance of transformer 4 (BRS).

Then, in the block for calculating the short circuit resistance of transformer 4 (BRS), the previously determined value of the effective value of the current of the secondary winding I ₂ , the ratio of the measured frequency of the network to the nominal value of the frequency f ' _pu and the actual value of the total voltage drop on the primary and secondary windings ΔU ₁₂ determine transformer short circuit resistance

As the final result, at the output of the block for calculating the short circuit resistance of the transformer 4 (BRS), the value of the short circuit resistance Z _{K of a} single-phase two-winding transformer is obtained.

From the output of the block for calculating the short circuit resistance of transformer 4 (BRS), data on the value of the short-circuit resistance of a single-phase double-winding transformer Z _{K is} input to a data acquisition and transmission device.

Determination of the short circuit value of a single-phase double-winding transformer in the operating mode at certain time intervals specified by the operator allows you to carry out operational control of the short-circuit resistance of a single-phase double-winding transformer and fixes the dynamics of its change in time, which in turn can serve as a source of information about the change in the technical state of a mono-phase double winding transformer.

Claims (1)

A device for operational monitoring of short circuit resistance of a single-phase double-winding transformer in operating mode, characterized in that it contains an electrical signal recorder whose outputs are connected in series with the input of the unit for calculating the effective values of the current of the secondary winding and the inputs of the unit for calculating the effective values of the voltages of the primary and secondary windings; the output of the unit for calculating the effective values of the current of the secondary winding is connected to the input of the unit for calculating the short circuit resistance of the transformer; one of the outputs of the unit for calculating the effective values of the voltages of the primary and secondary windings is connected to the input of the drive unit and the third input of the unit for calculating the phase angle between the voltages of the primary and secondary windings, the other output of the unit for calculating the effective values of the voltages of the primary and secondary windings is connected to the input of the unit for calculating the voltage drop and the fourth input of the block for calculating the phase angle between the voltages of the primary and secondary windings; the first and second inputs of the block for calculating the phase angle between the voltages of the primary and secondary windings are connected to the corresponding outputs of the recorder of electrical signals, the output of the block for calculating the angle of the phase shift between voltages of the primary and secondary windings is connected to one of the inputs of the block for calculating the voltage drop, the output of the cast unit is connected to the input of the voltage drop calculation unit, the output of the voltage drop calculation unit is connected to the input of the transformer short circuit resistance calculation unit, the other input of which connected to the output of the frequency variation control unit, the control unit changes the frequency input coupled to an output of the mains frequency measurement device, the output transformer of short-circuit resistance calculating unit is connected to the input of the data collection and transmission device.