RU2316778C1 - Method of elimination of influence of nonsimultaneos switching of single-phase transformers' voltage control devices of power three-phase automatic transformers for oscillogrphic tested currents of contacts of contactors and device for realization - Google Patents

Abstract

FIELD: power engineering; complex testing of power transformers.

SUBSTANCE: to estimate parameters of switching process, oscillographic tested currents of contactors' contacts are branched along winding of average and high voltage in such a way that currents in any phase of power transformer create two mutually compensating magnetomotive force. Dev ice has three-channel dc voltage source, three-channel digital oscillograph, connecting four-wired cable, tested power transformer and conductor which connects outputs of high-voltage winding with its neutral point. Contacts of contactors can be switched without opening tanks of transformers' voltage control devices and drainage of transformer oil.

EFFECT: reduced cost and labor input; improved precision of estimation of parameters.

2 cl, 7 dwg

Description

Technical field

The invention relates to the diagnosis of power transformers in the electric power industry, namely, electrical measurements of the process of switching contacts of contactors (with active resistances) of single-phase high-speed regulators under load (on-load tap-changers) installed on the medium voltage winding of a power autotransformer and having a separate drive in each phase (without opening the tanks On-load tap-changer and transformer oil discharge).

The method can be used in the energy sector for complex inspections of power autotransformers of voltage class, for example, 220 kV during commissioning, preventive, periodic tests of on-load tap-changers, for the diagnosis of its malfunctions.

It is proposed for three-phase power autotransformers with single-phase high-speed on-load tap-changers installed on its middle winding, a way to eliminate the effect of not simultaneous switching of single-phase regulators under load (on-load tap-changers) of power three-phase autotransformers on oscillographically contactor contact currents. Oscillograms of contactor contact currents are subsequently used to evaluate the parameters of the on-load tap-changer switching process without opening the on-load tap-changer tanks and draining transformer oil.

State of the art

A known method for evaluating the process of switching contactor contacts of a high-speed controller under load (with active resistances) on-load tap-changer of a three-phase power transformer, including oscillography of the contactor contact currents without taking into account the influence of the inductance of the winding of the power transformer with opening the on-load tap-changer and draining the transformer oil [Collection of methodological manuals for monitoring the state of electrical equipment . Section 2 Methods of monitoring the status of power transformers, autotransformers, shunt and suppressor reactors. Moscow, ORGRES, 1997, p.100].

However, this method requires opening the cover of the on-load tap-changer tank and draining the transformer oil to connect the oscilloscope inputs to the connection nodes of the voters, contacts of the contactor and branches with active resistance of the on-load tap-changer, since the contactor contacts are structurally located in the on-load tap-changer tank filled with transformer oil. This method requires the involvement of specially trained personnel to connect the oscilloscope to the conclusions of the contacts of the on-load tap-changer. In addition, the discharge of transformer oil is a time-consuming process and for its implementation it is necessary to have a specially prepared clean overall drained tank, oil pump, hose for pumping oil, etc., as well as additional personnel. When draining and subsequent pouring oil, its dielectric properties and environmental pollution may be degraded, as well as insulation resistance of the bakelite cylinder of the on-load tap-changer tank. In addition, at high humidity and in conditions of negative ambient temperatures, oscillography of the contacts of the contactor is practically impossible.

Therefore, the oscillography of high-speed on-load tap-changers with oil drain requires significant material resources and labor, and is only practicable in the warm season under favorable weather conditions.

Closest to the proposed method and device for its implementation is a method for evaluating the parameters of the switching process of the contactors of the high-speed on-load tap-changer contactor (with active resistances) of the regulator under the load of a three-phase power transformer, including oscillating the on-load tap-changer contactor without opening the on-load tap-changer and draining the transformer oil relative to the winding of the power transformer to which is connected to the on-load tap-changer, with subsequent analysis of the waveforms and parameter estimation [Fedorov Yu.A., Mikheev G.M., Shevtsov V. M., Batalygin S.N. A positive decision on the grant of a patent of the Russian Federation on the application No. 2004137182/28 (040442) dated 12/20/2004].

However, the above method is applicable for high-speed on-load tap-changers, the contacts of the contactor of all phases of which are in the same capacitance and are switched simultaneously using a single drive, for example, on-load tap-changers such as PC, PHTA, SDV, SCV, SAV.

The application of this method for single-phase on-load tap-changers with separate drives in each phase installed on the medium-voltage winding of a power autotransformer (for example, on-load tap-changers of the RNOA-110/1000 type) in the case of the presence of a difference in switching of phase contactors leads to distortion of current shapes when the magnetic circuit is affected oscilloscope currents without draining transformer oil and opening the on-load tap-changer tanks. Using the device of the prototype does not allow to evaluate the parameters of the process of switching contacts of the contactors relative to the winding to which the controller is connected.

SUMMARY OF THE INVENTION

The objective of the invention is the creation of a method and device for its implementation to eliminate the effect of not simultaneous switching of contactors of single-phase regulators under load (on-load tap-changers) of power three-phase autotransformers to oscilloscable currents of contactors installed on power autotransformers on the side of its middle winding with subsequent diagnosis of the process of switching on-load tap-changers.

The problem is solved due to the fact that the method of eliminating the effect of simultaneous switching of single-phase regulators under load (on-load tap-changers) of power three-phase autotransformers on oscillographically contactor contact currents for evaluating the parameters of the switching process without opening the on-load tap-changer and draining the transformer oil relative to the winding to which the on-load tap-changer is connected, followed by analysis of oscillograms and estimation of parameters by branching the oscillograph currents of contactors along the windings of medium and high voltage zheniya so that the currents in each phase of the power autotransformer create two mutually compensating each other magnetomotive force. To implement this method, it is proposed to use the prototype device according to the application No. 2004137182/28 (040442) of 12/20/2004, in which a conductor is additionally inserted connecting the terminals of the high-voltage winding of the power autotransformer with its neutral.

Brief Description of the Figures

Figure 1 shows the oscilloscope diagram of the process of switching the contacts of the contactors of high-speed on-load tap-changer power autotransformer according to the proposed method. The circuit contains a three-channel DC voltage source (1), a three-channel digital oscilloscope (2), a connecting four-wire cable (3), a tested three-phase power autotransformer with an on-load tap-changer (4), a conductor of 5 connecting the terminals of the high-voltage winding of the autotransformer with its neutral.

Figure 2 shows the waveforms of currents taken on the on-load tap-changer type RNAA-110/1000 according to the scheme without connecting the terminals of the high voltage winding with the neutral of the power autotransformer.

Figure 3 shows the waveforms of currents taken on the on-load tap-changer type RNAA-110/1000 according to the scheme of figure 1.

Disclosure of invention

We will disclose the invention by the example of on-load tap-changer diagnostics of the RNOA-110/1000 type on the ATDCTN-125000/220/110/6 power autotransformer. To determine the parameters of the switching process of the contacts of the on-load tap-changer contactors, the currents are oscillographed without opening the on-load tap-changer and the transformer oil is drained, followed by analysis of the obtained oscillograms according to the scheme according to Fig. 1, which differs from the prototype in that an additional conductor is connected to it, connecting the terminals of the high-voltage winding of the autotransformer with its neutral. The above type of on-load tap-changer in each phase has its own contactor and a separate drive. In practice, it is rarely possible to achieve synchronous switching of contactors of different phases. Therefore, due to the influence of the magnetic circuit and not simultaneous switching of the on-load tap-changer, the oscillograph currents are distorted so much that their subsequent analysis can be difficult or even impossible.

In the case of connecting the terminals of the high-voltage winding to the neutral of the autotransformer, the oscilloscope current flows both on the side of the middle winding and on the side of the high-voltage winding. Due to the fact that the number of turns on the windings of medium 110 kV and high voltage 220 kV on autotransformers is almost the same, and the currents flow through them in opposite directions, the magnetomotive forces in each phase are mutually compensated.

The waveforms of the currents in figure 2 and 3 are obtained on the same tap-changer. Moreover, the oscillograms of FIG. 2 are obtained for the prototype method, and the oscillograms of FIG. 3 are obtained by the proposed method.

Obviously, from the identical waveforms of the phase currents in figure 2, it is impossible to evaluate the switching parameters of the contactors. On the contrary, according to the oscillograms of the phase currents shown in figure 3, which are obtained using the proposed method and device for its implementation (figure 1), it is possible to evaluate the parameters of the process of switching contactors by the prototype method.

Claims (2)

1. A way to eliminate the effect of the non-simultaneous switching of single-phase regulators under load (on-load tap-changers) of power three-phase autotransformers on oscillographically contactor contact currents for evaluating the parameters of the switching process without opening the on-load tap-changer and draining the transformer oil relative to the winding to which the on-load tap-changer is connected, followed by analysis of the oscillograms and parameter estimation characterized in that the oscillographable currents of the contactors branch along the windings of medium and high voltage so that the currents in each phase sludge autotransformer create two cancel each other magnetomotive force. 2. A device for eliminating the influence of the non-simultaneous switching of single-phase regulators under load (on-load tap-changers) of power three-phase autotransformers installed on the side of the middle winding on the oscilloscope currents of the contacts of the contactors, characterized in that an additional conductor is connected to it, connecting the terminals of the high-voltage winding of the power autotransformer with its neutral .

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