JP3847556B2 - Soundness evaluation method and test method for electromagnetic induction equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a soundness evaluation method and a test method for iron cores of electromagnetic induction devices such as transformers, current transformers, alternators, and instrument transformers.
[0002]
[Prior art]
Conventionally, the soundness of iron cores of transformers, current transformers, or instrument transformers (hereinafter collectively referred to as transformers) has been evaluated by the circuit shown in FIG. 10 is a test transformer, 11 is an AC power supply having the same frequency as the rated frequency of the test transformer, 12 is a circuit breaker connected to the AC test power supply 11, and 13 is a voltage connected to the output side of the circuit breaker 12. The regulator 14 is a step-up transformer connected to the voltage regulator 13, 15 is a current transformer connected to the secondary side of the step-up transformer 14, and 16 is connected to the secondary side of the current transformer 15. 17 is a current measuring shunt resistor connected to the secondary side of the current transformer 15, and 18 is a memory for observing the excitation current waveform of the test transformer converted into a voltage by the shunt resistor 17. A device, in this case an oscilloscope.
[0003]
First, the circuit breaker 12 is turned on, the voltage of the AC test voltage 11 is adjusted by the voltage regulator 13, and the rated voltage is applied to the test transformer 10. The soundness of the iron core after on-site assembly is evaluated based on the instruction of the ammeter 16 and the current waveform of the storage device 18 at this time. In addition, as a simple method for evaluating the soundness of an iron core, there is a method of confirming soundness by exciting the iron core by winding a few turns around the iron core after stacking the iron core.
[0004]
[Problems to be solved by the invention]
The problems of the conventional method for evaluating the soundness of transformer cores are as follows.
Since it is necessary to generate the iron core magnetic flux of the transformer up to the rated magnetic flux level, (1) a large capacity power supply device and a step-up transformer are required to apply the rated capacity and rated voltage.
(2) Since a rated voltage is applied, high voltage equipment with an iron core in oil cannot be measured in the air and can only be evaluated after the transformer is assembled.
(3) Since repair of the iron core diagnosed as abnormal due to the item (2) is troublesome, it takes time and costs such as labor costs increase.
(4) The soundness of the iron core by generating a magnetic flux higher than the rated magnetic flux level cannot be evaluated.
[0005]
In addition, as a problem in soundness confirmation when an exciting winding is wound around an iron core for a few turns, (1) it is difficult to raise the iron core magnetic flux of the transformer to the rated magnetic flux level.
(2) Soundness can be evaluated after iron core loading, but not after transformer assembly is completed.
[0006]
The present invention has been made to solve the above-mentioned problems, and has been diagnosed as abnormal without requiring a large-capacity power supply device and a step-up transformer so that soundness can be evaluated at low frequency and low voltage. The purpose of the present invention is to simplify the subsequent repair and generate a magnetic flux higher than the rated magnetic flux level to easily obtain a soundness evaluation method and a test method for an iron core.
[0007]
[Means for Solving the Problems]
(1) A method for evaluating the soundness of an electromagnetic induction device according to claim 1 of the present invention is the method for evaluating the soundness of an electromagnetic induction device having an iron core such as a transformer, wherein a rated frequency and a rated voltage are applied to the electromagnetic induction device. Apply a low frequency / low voltage lower than the rated frequency / rated voltage so that it is equivalent to the magnetic flux of the core, and based on the excitation current and magnetic flux characteristics and excitation current waveform , It is to evaluate sex.
[0008]
(2) The soundness evaluation method for an electromagnetic induction device according to claim 2 of the present invention is lower than the rated frequency / rated voltage of the electromagnetic induction device in the soundness evaluation method for an electromagnetic induction device having an iron core such as a transformer. While applying a low frequency / low voltage, change the frequency of the low frequency and / or the voltage value of the low voltage to generate a magnetic flux exceeding the rated excitation level in the iron core, and the excitation current and magnetic flux at that time The soundness of the iron core is evaluated based on the relationship.
[0009]
(3) The electromagnetic induction device testing method according to claim 3 of the present invention assembles the soundness evaluation method of claim 1 or claim 2 before shipping the electromagnetic induction device manufacturing factory, and disassembles and transports it at the installation site. It is something to be done.
[0010]
(4) According to a fourth aspect of the present invention, there is provided a test method for electromagnetic induction equipment, wherein the soundness evaluation method according to claim 1 or 2 is applied to an existing electromagnetic induction equipment, and the iron core of the electromagnetic induction equipment is abnormal. Is to diagnose.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 shows a circuit configuration for evaluating the integrity of the iron core of the transformer according to the first embodiment of the present invention. 1 is a test transformer, 2 is a low frequency AC power supply, 3 is a switch connected to the low frequency AC power supply 2, 4 is a current limiting resistor connected to the output side of the switch 3, and 5 is a low frequency power supply 2 The connected voltage dividing resistor, 6 is an integrator for inputting the excitation voltage divided by the voltage dividing resistor 5, 7 is a shunt resistor for current measurement connected to the low-frequency AC power supply 2, and 8 is an integrator 6. Are an XY recorder, in this case, an oscilloscope for displaying in the X-axis and Y-axis directions, respectively, with the output voltage and the excitation current converted into voltage by the current measuring shunt resistor as inputs.
Next, a method for evaluating the core integrity of the transformer according to the first embodiment will be described.
In general, the induced electromotive force E of the transformer winding satisfies the relationship of the formula (1) when the voltage frequency is f, the number of turns of the transformer winding is n, and the magnetic flux of the iron core is Φ.
E = 4.44 fnΦ ――――― (1)
That is, the magnetic flux Φ is proportional to E / f. From this, the following procedure is obtained.
[0012]
(1) The frequency of the voltage to be applied is determined.
The initial voltage value of the applied voltage is about 100 V, which is the output voltage of the general-purpose low-frequency AC power supply device 2. For example, if the rated frequency of the target transformer is 50 Hz and the rated voltage is 100 kV, the magnetic flux Φ is proportional to E / f from the equation (1), so the frequency of the applied low voltage is
(100V / 100kV) × 50Hz = 0.05Hz
It becomes.
Since the rated voltage of the low-voltage winding of the transformer is generally 200 kV or less, it is practical to set the excitation voltage frequency to 0.1 Hz or less.
[0013]
(2) Exciting the iron core.
Excitation is started at the initial voltage and frequency determined in (1) above. At this time, the result obtained by the XY recorder 8 inputting and drawing the excitation current converted into the voltage by the shunt resistor for current measurement on the X axis and the magnetic flux obtained by integrating the excitation voltage by the integrator 6 on the Y axis. Examples of this are shown in FIGS. Fig. 2 shows the excitation current and magnetic flux characteristics and excitation current waveform of a healthy iron core. Fig. 3 shows the excitation current and magnetic flux characteristics and excitation current waveform when the iron core is distorted and the loss increases. When the iron core is stacked, the iron core is displaced, and the excitation current and magnetic flux characteristics and the excitation current waveform when gap occurs are shown.
[0014]
(3) Evaluation of soundness of iron core If the characteristics of the exciting current and magnetic flux drawn in (2) above are the same as those in FIG. 2, it is evaluated that the iron core is sound. As shown in FIGS. 3 and 4, when the characteristic different from that shown in FIG. 2 is drawn, it is evaluated that the iron core is abnormal. In addition, as one means of evaluation, evaluation is also performed by comparing the excitation current and magnetic flux characteristics that have been evaluated to be sound in the past.
[0015]
Embodiment 2. FIG.
Conventionally, only a magnetic flux of the rated magnetic flux level could be generated, but in the second embodiment, the application of the low frequency / low voltage of the first embodiment is applied to generate a magnetic flux that exceeds the rated magnetic flux level. To diagnose abnormalities in the iron core.
A low frequency / low voltage is generated from the low frequency power supply 2 and at least one of the frequency / voltage is adjusted to generate a magnetic flux higher than the rated excitation level in the iron core of the transformer 1.
At this time, the XY recorder 8 inputs the excitation current converted into the voltage by the current measuring shunt resistor 7 on the X axis, and the magnetic flux obtained by integrating the excitation voltage by the integrator 6 on the Y axis. And draw the relationship of magnetic flux. By increasing the number of excitation current and magnetic flux characteristics samples when a magnetic flux exceeding the rated magnetic flux level is generated, it is possible to diagnose the abnormality of the iron core.
[0016]
Embodiment 3 FIG.
The first and second embodiments are basically carried out after the iron core is stacked in the manufacturing plant, but this third embodiment is the confirmation of the soundness of the iron core after the iron core stacking at the installation site after the dismantling and transporting transformer is installed. It also applies to.
First, the soundness of the iron core of the disassembled transport type transformer is confirmed at the factory according to the first embodiment. After disassembling the transformer and transporting it to the site, reassembling the transported transformer on site, measuring the characteristics of the exciting current of the iron core again according to the first embodiment, and the characteristics of the exciting current after factory assembly Compare with Through the above process, the soundness of the disassembled transport transformer after the on-site assembly is confirmed.
[0017]
Embodiment 4 FIG.
Note that the evaluation methods of Embodiments 1 and 2 can also be applied to existing electromagnetic induction devices.
The present invention is also useful for evaluating the soundness of an iron core of an electromagnetic induction device having an iron core other than a transformer, such as a current transformer, an instrument transformer, or an AC device.
[0018]
【The invention's effect】
As described above, according to the first and second aspects of the present invention, since the low frequency and low voltage are used, the soundness of the iron core can be obtained without requiring large capacity and high voltage test equipment such as a step-up transformer. Can be evaluated.
[0019]
According to the third and fourth aspects of the present invention, since it is not necessary to generate a high voltage in the electromagnetic induction device, it is easy even at the manufacturing factory, at the installation site, or for the existing electromagnetic induction device. Can be tested.
[Brief description of the drawings]
FIG. 1 is a diagram showing a circuit configuration for evaluating iron core soundness of a transformer according to Embodiment 1 of the present invention.
FIG. 2 is a diagram showing excitation current and magnetic flux characteristics and a current waveform when a voltage is applied to a healthy transformer core according to Embodiment 1 of the present invention.
FIG. 3 is a diagram showing excitation current and magnetic flux characteristics and a current waveform when a voltage is applied to the transformer core with increased loss in the first embodiment of the present invention.
FIG. 4 is a diagram showing excitation current and magnetic flux characteristics and a current waveform when a voltage is applied to the transformer core in which gap occurs in Embodiment 1 of the present invention;
FIG. 5 is a diagram showing a circuit configuration for evaluating iron core soundness of a conventional transformer.
[Explanation of symbols]
1: Test transformer 2: Low frequency AC power supply 3: Switch 4: Current limiting resistor 5: Voltage dividing resistor 6: Integrator 7: Shunt resistor for current measurement 8: XY recorder 10: Test transformer

Claims (4)

In the soundness evaluation method for electromagnetic induction devices with iron cores such as transformers, the above rated frequency and rated voltage should be set to be equivalent to the magnetic flux of the iron core when the rated frequency and rated voltage are applied to the electromagnetic induction devices. A method for evaluating the soundness of an electromagnetic induction device, wherein a low low frequency and a low voltage are applied, and the soundness of the iron core is evaluated based on the excitation current and magnetic flux characteristics and the excitation current waveform at the time of application. In the soundness evaluation method for electromagnetic induction equipment having an iron core such as a transformer, a low frequency / low voltage lower than the rated frequency / rated voltage of the electromagnetic induction equipment is applied, and the low frequency and low voltage are applied. Electromagnetic induction characterized in that at least one of the voltage values is changed to generate a magnetic flux above the rated excitation level in the iron core, and the soundness of the iron core is evaluated based on the relationship between the excitation current and the magnetic flux at that time Equipment health assessment method.   A method for testing electromagnetic induction equipment, comprising performing the soundness evaluation method according to claim 1 or 2 before shipping the electromagnetic induction equipment at a manufacturing factory and when disassembling and transporting and assembling the equipment at the installation site.   A test method for an electromagnetic induction device, wherein the soundness evaluation method according to claim 1 or 2 is applied to an existing electromagnetic induction device to diagnose an abnormality of an iron core of the electromagnetic induction device.

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