KR100945142B1 - Pad mounted transformer - Google Patents

Abstract

PURPOSE: A method for checking a ground transformer is provided to check the status of the ground transformer by analyzing dissolved gas in insulating oil used in the ground transformer. CONSTITUTION: An insulating oil sample is collected for testing the quality of a ground transformer and analyzing dissolved gas in insulating oil(100). The abnormality of the ground transformer is determined by measuring a voltage, a current, a load, an infrared temperature, a ground resistance, and checking oil leakage(200). The deterioration of the insulating oil is measured by testing moisture and insulation breakdown withstand voltage(300). The dissolved gas in the insulating oil is analyzed(400).

Description

Ground transformer check method {Pad mounted transformer}

The present invention relates to a method of inspecting a ground transformer, and more particularly, to collect a sample of insulating oil used in the ground transformer, and to test and analyze the gas in the oil of the insulating oil and to check the equipment of the ground transformer so that the ground transformer can be used safely. A ground transformer check method.

As electricity consumption has increased along with domestic industrial development, large-scale electrical facilities such as power transformers and circuit breakers have been added to the industry since the late 1960s. Since these existing power facilities have been used for a long time, the aging is remarkable now. Especially, stable power supply is an important requirement due to the recent automation and advancement of industrial facilities. The management of old power equipment is very important in terms of preventing economic losses and industrial safety accidents.

Power facilities are generally expensive and large, so replacement costs are very high, requiring long hours of work and a lot of manpower. In addition, most facilities must be individually designed and manufactured for each application, and if many years of intentional progress are not made, losses due to production disruptions can be enormous, and the wavelength threatens social stability such as large power outages. To the level of

Recently, the consumption of electricity is increasing rapidly due to the increase of cooling loads and electric information processing facilities and convenience facilities such as computers, and this phenomenon is indicated by the expansion of the overload area and the increased load bias area. As a result, the load of the column and ground transformers located at the system end is increased irregularly, and frequent breakdown of the transformer occurs due to deterioration due to overload and external environment.

Such a transformer is responsible for important functions related to the stable supply of power, and requires higher reliability than any other power equipment. Insulation breakdown of the insulating oil that cools the charging part of the transformer causes burnout of the transformer.

The main causes of burnout of transformers due to dielectric breakdown are that when the temperature difference between the inside and outside of the transformer occurs, water is generated inside the transformer, and the moisture is contained in the insulating oil, or the viscosity of the insulating oil increases due to long-term use, thereby greatly increasing the cooling efficiency. It has been shown to be due to carbon, impurities, etc. that are degraded or generated during use.

Therefore, in order to prevent the burnout of the transformer due to the dielectric breakdown of the conventional transformer, it is necessary to remove moisture, carbon and impurities generated during use and filter the insulating oil. However, the conventional transformer has a disadvantage in that the insulating oil cannot be checked in a state in which power is supplied to the transformer and operated, that is, in a live state.

In addition, in the related art, since the voltage and current load measurement of the device, whether the connection cable is overheated and the low voltage side connection bus terminal check are not performed, there are various problems in that it is not possible to effectively determine the overall ground transformer abnormality.

Therefore, the object of the present invention was devised in view of the above problems, and by taking a sample of the insulating oil used in the ground transformer and testing and analyzing the gas in the oil of the insulating oil and at the same time check the equipment of the ground transformer to use the ground transformer safely To provide a method of checking the ground transformers.

As a means for achieving the above object, the present invention is to collect the insulating oil used in the ground transformer in operation in a separate sample container and use it as a sample for quality test, and the sample sample is in close contact with the atmosphere An insulating oil sampling step of sealing and transporting a label prepared in advance to a sample container in a field; A device checking step of determining whether there is an abnormality of the device by measuring voltage and current load of the ground transformer, measuring infrared temperature, measuring ground resistance, and visually inspecting the oil leakage site when the sampling of the insulating oil is completed; The sample is subjected to a moisture test, dielectric breakdown voltage test to determine the presence of impurities such as moisture and dust in the insulating flow rate, and to determine whether the insulating oil is deteriorated by testing the computational value; Including the oil-in-oil-dissolved gas analysis step to prevent the accident by determining the type, place, and degree of failure by investigating the component, amount, and secular variation of oil-dissolved gas contained in the oil. It is a basic feature.

As described above, according to the present invention, since the sample of the insulating oil used in the ground transformer is collected and tested and analyzed for the gas in the oil of the insulating oil, the equipment of the ground transformer is inspected, and thus the effect of the ground transformer can be safely used. It is.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In order to check the ground transformer of the present invention, the inspection is completed while the insulating oil sampling step 100, the device checking step 200, the insulating oil degradation measurement step 300, and the insulating oil-dissolved gas analysis step 400 are completed.

Insulating oil sampling step 100;

Collect the insulating oil used in the ground transformer in operation in a separate sample container and use it as a sample for quality test. The sample is tightly sealed so that it does not come into contact with the atmosphere, and the previously prepared label is attached to the sample container in the field. To carry.

1) Quality test sample

When insulating oil is collected from the inflow equipment, the electrical insulation oil test method (KSC 2101-1995) should be taken in accordance with 4.7.

When sampling oil in use, care must be taken to ensure safety.

Sample containers should be easy to clean, such as glass bottles and cans, and do not affect the characteristics of the oil. Lids should not be contaminated with the sample.

Pay attention to the contamination of samples by outside air, and avoid collection whenever possible, especially in bad weather.

When taking samples by opening or closing the cock or valve, there is a risk of disaster such as oil leakage due to failure.

Care shall be taken not to damage the sealed inlet electrical appliances and inlet cables.

In order to prevent the sample from being changed, attach the prepared label on site and transport it.

2) Dissolved gas analysis sample

Insulating oil should be collected from the transformer in operation, taking care of the above-mentioned quality test sampling method and following sampling method.

Take a representative sample from the drain valve at the bottom of the transformer tank. This is because the pyrolysis gas generated at the abnormal part of the transformer part is bubble-shaped and diffused and dissolved in the insulating oil while moving to the top of the tank, and then the distribution state of the gas is uniform by forced or natural circulation of the insulating oil. Sampling is of paramount importance for accurate diagnosis of the condition of the transformer.

Remove the cover of the drain valve line, wipe the end clean, connect the rubber stopper adapter, draw about 500ml of insulation oil from the drain line, wash the container with the extracted insulation oil, and then the end of the adapter conduit Make sure you touch the bottom.

Slowly open the valve and push the adapter firmly so that no bubbles are created.The sample is then poured over a 500 ml aluminum can or glass jar, gently tapping the corner of the container to release any remaining air and slowly bleeding out the conduit. The adapter should be tight and the valve open a little longer.)

When the oil is finished, cover the sample container with the lid of the sampling container quickly so that it does not come into contact with the atmosphere, and close the lid with the outer lid to prevent the inner lid from being damaged.

In order to prevent the sample from being changed, attach the prepared label on site and transport it.

Device checking step 200;

When the sampling of the insulating oil is completed, it is determined whether the equipment is abnormal by measuring the voltage and current load of the ground transformer, measuring the infrared temperature, measuring the ground resistance, and visually inspecting the oil leakage.

1) Voltage and current load measurement

Measure the secondary load voltage and current of the transformer in operation by using a measuring device such as a hook on meter or multi tester.

3Φ measures the voltage and current of the low voltage terminals X1, X2, X3, XO, and 1Φ measures the voltage and current of the low voltage terminals X1, X2, X3, and the Korea Electric Power Corporation underground distributor operation manual (ground transformer management) Calculate the load unbalance and load rate in Chapter 3 Measurements (PAGE 194–195) and Measure the measurement time in the Guidelines).

The load unbalance rate is calculated according to the following formula, and corrective action is taken for more than 40% of single-phase three-wire and 30% of three-phase four-wire.

2) Infrared temperature measurement

Whether the high pressure side elbow connection material and the connection cable are overheated by using an infrared temperature measuring device, the temperature of the low pressure side connection bus terminal contacts and the cable is measured for each phase, and the temperature is recorded.

3) Earth resistance measurement

Using a hook-on earth ohmmeter, measure the ground resistance of the ground wire connected to the transformer ground terminal from underneath the foundation.

During the measurement, pay attention to the energization state of the secondary side booth, and record the ground wire's electrical conductivity and ground resistance.

The earth resistance should be kept below the specified value (10Ω) and should be carried out in winter as much as possible and avoided when the weather is cloudy and the earth is damp.

4) Visual inspection of oil leakage

Leakage part inspection point

Visual inspection of BAY-O-NET-FUSE, high pressure side bushing flange, elbow connector and bushing well insert, tap changer, low pressure side gauge, oil thermometer, secondary side bushing enclosure, etc. Record it out.

Insulation oil degradation measurement step 300;

The sample collected is tested for moisture and dielectric breakdown voltage to determine the presence of impurities such as moisture and dust in the insulating flow rate, and the computational value is tested to determine whether the insulating oil is deteriorated.

1) Moisture Test

 The trace moisture test is performed by taking a sample with a syringe and using a dose titration method or an electricity titration method. The presence of moisture in the transformer insulating oil reduces the insulation breakdown voltage and promotes deterioration of the insulating oil and insulating paper.

Analytical method (using Metlert DL37 KF Coulometer)

Test Method for Electrical Insulating Oil (KS C 2101-1995) 20. Follow the water test and use the measuring instrument and the designated reagent.

Quantitative Method

Electricity titration method: A sample is added to a mixture of pyridine and methyl alcohol mainly composed of iodide ions and sulfur dioxide to react water with iodine generated by electrolysis, and the amount of water (ug) is obtained from the electric quantity. The principle can be explained as follows.

Iodide ions in the mixed solution are oxidized at the anode to become iodine.

[2I + 2e → I ₂ ]

The amount of iodine generated is proportional to the amount of electricity ⓒ consumed for electrolysis, and based on Faraday's law, 1 mol of iodine is generated by an amount of electricity of 96487 x 2C (current (A) x time (S)). The generated iodine reacts with the water in the sample and the chemical equation shown below, like iodine in Karl Fischer reagent.

Since 1 mol of iodine reacts with 1 mg of water, the iodine required to react with 1 mg of water is generated by 96487 x 2/18000 = 10.71 electricity. Therefore, measuring the amount of electricity consumed up to the proper end point can determine the amount of water.

The amount of electricity can be obtained by integrating the electrolytic current with time. In addition, since the generated iodine reacts with water and returns to the iodide ion, the mixed solution can be used repeatedly.

Chemical reaction

Dose titration method: Obtain water by using iodine, sulfur dioxide, pyridine and methyl alcohol as the main components of Karl Fischer reagent (mixed solvent) by quantitatively reacting with water as shown in the above chemical formula.

The Karl Fischer reagent is dropped into the titration flask containing the sample to the point of change in the polarization current. Since the amount of reagent consumed is proportional to the amount of water, the water in the sample can be quantified by expressing the inverse value of the reagent in advance.

Quantification range: 10ug 100 mg water content / sample

           Limit of detection 0.1 ug water

The amount of sample to be injected should be about 1 ~ 10ml depending on the expected water concentration, and the test results should be repeated two or more times so that the difference of test results should not exceed the following tolerance.

The moisture is output in ppm up to the third decimal place from the instrument printer, but the mean value is rounded to an integer value.

2) Insulation breakdown voltage test

Insulation breakdown voltage is measured by increasing the voltage at a rate of about 3kv per second using a spherical electrode obtained by taking insulation oil and adjusting the gap between electrodes to 2.5mm. It is a measure to determine whether the insulating oil can be used under the voltage system, and also to determine the presence or absence of such impurities because the dielectric breakdown voltage is lowered by the moisture, dust or dielectric particles in the insulating oil.

Assay Method (using MEGGERFOSTEROilTestSetsOTS60AF / 2)

Test Method for Electrical Insulating Oil (KS C 2101-1995) 22. Use the instrument in accordance with the dielectric breakdown voltage test.

Quantitative Method

The dielectric breakdown voltage test was used to fill the sample up to the indicator line of the glass test glass test vessel and increase the voltage at a rate of about 3 kv per second using a corresponding sphere electrode 12.5 mm in diameter with the inter-electrode gap adjusted to 2.5 mm. The dielectric breakdown voltage at the commercial frequency of the insulating oil is measured. The device consists of a transformer, a circuit breaker, a resistor, a voltage regulator, an electrode, a container and a voltmeter.

Quantification Range: 0-60 kv

Insulation breakdown voltage is obtained from two samples taken from the same test oil and measured five times for each sample. From the results, the average of eight total values obtained by removing the first value is obtained according to the following equation. The unit is kv, the decimal point is calculated to the first digit, and ends with an integer according to KS A 0021. In addition, the measured value shall specify the test temperature of the sample.

V: dielectric breakdown voltage

V2 + V3 + V4 + V5: measured values of the second, third, fourth and fifth times of the first sample

V2 '+ V3' + V4 '+ V5': Measured value of 2nd, 3rd, 4th and 5th samples of 2nd sample

※ In the case of silicone oil, take 5 samples from the same test oil once

    Let it be five average values measured.

3) Computerized value test

Computerized value test is to measure by indicator titration method after taking insulation oil and dissolving it in mixed solvent. Potassium hydroxide required to neutralize all acidic components contained in 1gr of insulating oil, expressed in mg water.

Analysis method (using the titration method)

Electrical insulating oil test method (KS C 2101 1995) 16. Comply with the computerized value test.

Quantitative Method

Computational testing is performed on toluene 3 samples. Dissolve in 100 ml of the mixed solvent for ethyl alcohol 2, add 2 ml of the alkali blue 6B indicator, titrate with potassium hydroxide standard solution, and calculate the calculated value from the standard amount of potassium hydroxide used for neutralization. When measuring the calculated value of silicone oil, use the sample for toluene 1. It is dissolved in a mixed solvent of 1 isopropyl alcohol (or n-butyl alcohol).

Quantification range: 0.01 1.00 mgKOH / g

Take about 20 gr of sample (about 5 gr of high computational value or dark color sample) and test it. Computation value is calculated according to the following formula, and it is calculated to 3 digits after the decimal point and ends with 2 digits after the decimal point according to KS A 0021.

N: Nominal concentration of 1 / 10N potassium hydroxide standard solution

A: Amount of 1 / 10N potassium hydroxide standard solution required for titration (ml)

B: Amount of 1 / 10N potassium hydroxide standard solution required for the background test (ml)

W: weight of sample (g)

Insulating oil oil-dissolved gas analysis step 400;

Investigate the components of dissolved oil in oil, the amount of generation, and the aging change to determine the type, location, and extent of the failure to prevent accidents.

When an abnormality occurs in the transformer, local overheating is generally generated at the location, and the thermal insulation decomposes surrounding insulation (insulating oil, insulating paper, press board, synthetic resin, varnish).

The thermally decomposed insulating material generates a specific gas depending on the type and the temperature of the abnormal site.

Such gases have a high saturation solubility in insulating oil and dissolve in a significant amount of insulating oil. In case of abnormality diagnosis by analyzing gas in insulating oil, the dissolved gas is analyzed by mass spectrometer or gas chromatograph, and the gas component, quantity and secular variation are investigated to determine the type, location and degree of failure. To prevent.

This method is characterized by the electrical test that is a warning, effective for the determination of iron core local accidents, and the occurrence of a gentler accident at an early stage. However, it is difficult to determine accidental accidents such as insulation breakdown in advance.

Gases generated by the accident inside the transformer may include overheating of insulating oil, arc decomposition in oil, overheating of solid insulator, and arc decomposition of solid insulator.

※ In gas analysis of transformer, 12 kinds of gases are generally covered. That is, the flammable gas of H2, O2, N2, CH4, CO, CO2, C2H2, C2H4, C2H6, C3H6, C3H8, C4H8, and mainly H2, CH4, C2H6, C3H6, C2H4, C2H2 as a component that determines normal or abnormality. Moreover, CO, CO2, CH4 are used as a component which determines deterioration of an insulator.

1 is a block diagram of a ground transformer check method according to the present invention;

(Explanation of symbols for the main parts of the drawing)

100; Insulating Oil Sampling Step

200; Instrument Check Step

300; Insulation oil deterioration measurement step

400; Insulating oil-dissolved gas analysis step

Claims (1)

 In order to use the ground transformer for quality test and analysis of dissolved gas in oil, the insulating oil used in the transformer in operation is collected in a separate sample container, and the sample sample is tightly sealed to prevent contact with the atmosphere. An insulating oil sampling step (100) of attaching a label prepared in advance to the sample container in the field;     When the sampling of the insulating oil is completed, measure the secondary voltage and current load of the ground transformer, measure the high voltage elbow connector and connection cable, the infrared temperature according to the low pressure side connection bus terminal and cable overheating, and from the base to the ground terminal of the transformer. Ground resistance measurement of connected ground wire, BAY-O-NET-FUSE, high pressure side bushing flange, elbow connector and bushing well insert, tap changer, low pressure side oil gauge, oil thermometer, secondary side bushing enclosure, etc. A device checking step (200) of determining whether a device is abnormal by checking;     Moisture test to quantify the moisture contained in the sample collected, dielectric breakdown voltage test to measure the drop in dielectric breakdown voltage caused by impurities such as moisture, dust and dielectric particles in insulating oil, Insulating oil degradation measurement step 300 of measuring;     Investigating the dissolved gas in oil, generation amount, secular variation, etc. to determine the type, location, and degree of failure, the oil-in-oil dissolved gas analysis step 400 includes an accident of a transformer in operation. Ground transformer check method, characterized in that to prevent.

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