CN103808789A - Method for detecting antioxidant content of transformer oil by step wave voltammetry method - Google Patents

Abstract

The invention discloses a method for detecting antioxidant content in transformer oil by step wave voltammetry. The method is to ultrasonically dissolve a certain amount of transformer oil to be tested in a certain volume of supporting electrolyte to obtain a sample to be tested, and then use a 6mm diameter The graphite electrode is used as the working electrode, and the electrochemical workstation adopts the step wave voltammetry method. Under specific conditions, the sample to be tested is electrochemically detected. On the basis of the proportional relationship between the concentration in transformer oil, a method for detecting the content of T501 antioxidant in transformer oil by step wave voltammetry was established. Compared with the prior art, the invention has simple operation, low cost, rapid measurement and high accuracy, and can realize on-site analysis of samples.

Description

Method for Detecting Antioxidant Content in Transformer Oil by Step Wave Voltammetry

technical field

The invention belongs to the technical field of chemical detection. Specifically, the invention relates to a method for detecting antioxidant content in transformer oil by step wave voltammetry.

Background technique

In order to effectively complete the various functions of transformer oil, the transformer oil itself must have good chemical, physical and electrical properties. Transformer oil is inevitably oxidized during operation, producing a large amount of peroxides and oxidation products such as alcohols, aldehydes, ketones, acids, etc. These oxidation products are very harmful to the safe operation of power system equipment.

Transformer oil is added with T501 antioxidant before leaving the factory to improve the oxidation stability of the oil. However, excessive antioxidants will affect the electrical properties of the oil. At the same time, due to factors such as the operation of the purifier and the aging products in the oil treated by the oil filter, the content of antioxidants in the oil will gradually be lost. GB/T7595—2008 "Quality Standards for Transformer Oil in Operation" stipulates that the mass fraction of T501 in domestic new oil and recycled oil should not be lower than 0.3% to 0.5%, and that in running oil should not be lower than 0.15%, otherwise it should be supplemented.

At present, the commonly used methods for detecting the content of T501 antioxidant in transformer oil include spectrophotometry, liquid chromatography and infrared spectroscopy, but each method has great defects: spectrophotometry, sample pretreatment is complicated, and the used There are many instruments and medicines, and the repeatability is poor; liquid chromatography and infrared spectroscopy are relatively accurate in detection, but the instruments and equipment are very expensive, and the measurement time is long, which is not conducive to the large-scale promotion of the method.

Obviously, there is no relatively mature and simple method for the determination of T501 antioxidant content in transformer oil.

Therefore, it is of great significance to develop a method for the determination of T501 antioxidant content in transformer oil with low cost, simple operation, rapid measurement and high accuracy.

Contents of the invention

The purpose of the present invention is to provide a method for measuring antioxidant content in transformer oil with low cost, simple operation, rapid measurement and high accuracy, so as to overcome the defects in the prior art and meet the needs of actual conditions.

The technical scheme that the present invention solves the problems of the technologies described above is as follows:

A method utilizing ladder wave voltammetry to detect antioxidant content in transformer oil, comprising the following steps:

1. Pretreatment of the working electrode: use 0.3 μm alumina polishing powder to polish the graphite electrode with a diameter of 6 mm, then rinse it with deionized water, and ultrasonicate it in absolute ethanol for 3 minutes.

2. Preparation of the sample to be tested: ultrasonically dissolve the transformer oil in the supporting electrolyte, wherein the volume ratio of the transformer oil and the supporting electrolyte is 1 to 1.5:50, and the supporting electrolyte is potassium hydroxide of 0.1 to 0.3 mol L ^-1 weak.

3. Electrochemical detection: a graphite electrode with a diameter of 6mm is used as the working electrode, a saturated calomel electrode is used as the reference electrode, and a 213-type platinum electrode is used as the auxiliary electrode to form a three-electrode system. The samples were subjected to electrochemical tests. The measurement conditions of ladder wave voltammetry are: initial potential -0.1V, end potential -0.4V, potential increment 10mV, sampling width 0.001s, resting time 2s.

4. Determination of T501 content in the oil sample to be tested: according to the preparation steps of the sample to be tested, the T501 content was respectively 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.1%, 0.2%, 0.3% , 0.4%, and 0.5% standard transformer oil samples were prepared as standard samples, and then the ten standard samples obtained were electrochemically tested by step wave voltammetry according to the electrochemical detection steps. In the TXT text corresponding to the graph, read the peak current of the T501 antioxidant characteristic peak respectively, take the T501 content as the abscissa, and take the peak current as the ordinate to draw the standard curve of the T501 content. According to the same steps, take a certain amount of transformer oil samples to be tested, prepare the samples to be tested, and then use the electrochemical workstation to adopt step wave voltammetry. For chemical testing, read the peak current A of the T501 antioxidant characteristic peak in the TXT text corresponding to the obtained ladder wave voltammetry curve, and bring A into the standard curve to calculate the T501 antioxidant content in the transformer oil sample to be tested.

5. Using step wave voltammetry, under the same conditions, electrochemically measure the blank sample and the sample to be tested in turn. The measurement conditions are: initial potential -0.1V, end potential -0.4V, potential increment 10mV, sampling Width 0.001s, standing time 2s, get the characteristic curve of step wave voltammetry, in the TXT text corresponding to the characteristic curve of step wave voltammetry, read the T501 antioxidant characteristic oxidation peak in the range of -0.3V～0V Peak value, put the peak value into the corresponding standard curve, and calculate the antioxidant content of T501.

The present invention has following beneficial effects:

(1) The method of the present invention is not only low in cost, simple in operation, rapid in measurement and high in accuracy, but also can realize on-site analysis of samples. It is of great significance for the rapid and accurate determination of T501 antioxidant content in transformer oil.

(2) The measurement conditions of the present invention are: initial potential -0.1V, end potential -0.4V, potential increment 10mV. The three most important aspects of an electrochemical test method are optimized to the greatest extent: scanning direction, scanning range and scanning speed, which greatly improves the sensitivity of the measurement and reduces the lower limit of the method.

(3) The present invention uses a graphite electrode with a diameter of 6 mm as the working electrode, and uses 0.1 to 0.3 mol L ^-1 potassium hydroxide ethanol solution as the supporting electrolyte, optimizing the electrochemical determination conditions of T501 antioxidant content in transformer oil , which greatly reduces the measurement error and provides a guarantee for the accuracy of the experimental results.

(4) The dissolved volume ratio of transformer oil and supporting electrolyte used in the present invention is (1-1.5):50, which greatly improves the peak value of T501 antioxidant oxidation peak in the obtained electrochemical characteristic curve and improves the sensitivity of measurement.

Description of drawings

Fig. 1 is the step wave voltammetry curve obtained in the blank sample analysis in Example 1 of the present invention.

Fig. 2 is a ladder wave voltammetry curve obtained in the analysis of the sample to be tested in Example 1 of the present invention.

Fig. 3 is a ladder wave voltammetry curve obtained in the analysis of the sample to be tested in Example 2 of the present invention.

Fig. 4 is an overlay diagram of the step wave voltammetry curves obtained for the samples to be tested in Example 1 and Example 2 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with specific examples.

Example 1

Method for Detecting Antioxidant Content in Transformer Oil by Step Wave Voltammetry

Detection steps:

(1) Electrode pretreatment: use 0.3 μm alumina polishing powder to polish the graphite electrode with a diameter of 6 mm, then rinse it with deionized water, and ultrasonicate it in absolute ethanol for 3 min.

(2) Pipette 50ml of 0.2mol·L ^-1 potassium hydroxide ethanol solution as a blank sample. Pipette 1.5ml of transformer oil containing T501 antioxidant with a mass fraction of 0.5%, and ultrasonically dissolve it in 50ml of 0.2mol·L ^-1 potassium hydroxide ethanol solution as the sample to be tested.

(3) Electrochemical detection: a graphite electrode with a diameter of 6mm is used as the working electrode, a saturated calomel electrode is used as the reference electrode, and a 213-type platinum electrode is used as the auxiliary electrode to form a three-electrode system. The measured samples were electrochemically tested. The measurement conditions of the ladder wave voltammetry were: initial potential -0.1V, end potential -0.4V, potential increment 10mV, sampling width 0.001s, and resting time 2s.

(4) Draw the standard curve of T501 content: According to the preparation steps of the samples to be tested, the T501 content was respectively 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4% %, 0.5% standard transformer oil samples, prepared as standard samples, and then using the step wave voltammetry method, according to the electrochemical detection steps, the ten standard samples obtained were electrochemically tested, and the obtained step wave voltammetry curve In the corresponding TXT text, read the peak current of the T501 antioxidant characteristic peak respectively, take the T501 content as the abscissa, and take the peak current as the ordinate, and draw the standard curve of the T501 content.

(5) Using ladder wave voltammetry, under the same conditions, the blank sample and the sample to be tested were electrochemically measured in turn. The measurement conditions were: initial potential -0.1V, end potential -0.4V, potential increment 10mV, The sampling width is 0.001s, and the resting time is 2s to obtain the characteristic curve of step wave voltammetry (Figure 1 and Figure 2). In the TXT text corresponding to the characteristic curve of step wave voltammetry, read the peak A1 of the characteristic oxidation peak of T501 antioxidant in the range of -0.3V to 0V, A1=9.784e-6A. Bring the A1 value into the corresponding standard curve to calculate the antioxidant content X of T501, X=0.498%.

Example 2

Method for Detecting Antioxidant Content in Transformer Oil by Step Wave Voltammetry

Detection steps:

In Example 2, the steps are the same as in Example 1, the difference is only in the preparation of the sample to be tested: pipette 1.0ml of transformer oil containing T501 antioxidant with a mass fraction of 0.5%, ultrasonically dissolve it in 50ml of 0.2mol L ^-1 hydroxide Potassium ethanol solution, as the sample to be tested. The sample to be tested was electrochemically measured by step wave voltammetry, the measurement conditions were: initial potential -0.1V, end potential -0.4V, potential increment 10mV, sampling width 0.001s, resting time 2s, the obtained step wave voltammetry curve Figure, see Figure 3. In the TXT text corresponding to the characteristic curve of step wave voltammetry, read the peak A2 of the characteristic oxidation peak of T501 antioxidant in the range of -0.3V to 0V, A2=8.235e-6A. Bring the A2 value into the corresponding standard curve to calculate the antioxidant content X of T501, X=0.494%.

Refer to FIG. 4 for the overlay diagram of the step wave voltammetry curves obtained for the samples to be tested in Example 1 and Example 2.

The above are only specific embodiments of the present invention, and do not limit the protection scope of the present invention; any replacement and improvement made on the basis of not violating the concept of the present invention shall fall within the protection scope of the present invention.

Claims (1)

1. utilize staircase waveform voltammetry to detect the method for Antioxygen Content in Transformer Oil, it is characterized in that: comprise the following steps:

1) pre-service of working electrode: use the graphite electrode of 0.3 μ m aluminum oxide polishing powder polishing diameter 6mm, then use deionized water rinsing, and in absolute ethyl alcohol ultrasonic 3min;

2) preparation of testing sample: in supporting electrolyte, the volume ratio of transformer oil and supporting electrolyte is 1～1.5: 50 by transformer oil ultrasonic dissolution, and described supporting electrolyte is 0.1～0.3molL ^-1potassium hydroxide-ethanol solution;

3) Electrochemical Detection: take the graphite electrode of diameter 6mm as working electrode, saturated calomel electrode is contrast electrode, 213 type platinum electrodes are auxiliary electrode, composition three-electrode system, utilizes electrochemical workstation to adopt staircase waveform voltammetry to carry out electro-chemical test to testing sample, and the condition determination of staircase waveform voltammetry is: initial potential-0.1V, stop current potential-0.4V, current potential increment 10mV, sampling width 0.001s, time of repose 2s;

4) mensuration of T501 content in oil sample to be measured: according to step 2), be 0.01% by T501 content successively respectively, 0.02%, 0.03%, 0.04%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% standard transformer oil sample, be formulated as standard model, then utilize staircase waveform voltammetry, according to step 3), respectively ten of gained kinds of standard models are carried out to electro-chemical test, in TXT text corresponding to gained staircase waveform volt-ampere curve figure, read respectively the peak current of T501 antioxidant characteristic peak, take T501 content as horizontal ordinate, take peak current as ordinate, draw out the typical curve of T501 content, according to identical step, get a certain amount of transformer oil sample to be measured, preparation obtains testing sample, then utilize electrochemical workstation to adopt staircase waveform voltammetry, under identical condition, successively blank sample, testing sample are carried out to electro-chemical test respectively, in TXT text corresponding to gained staircase waveform volt-ampere curve figure, the peak current A that reads T501 antioxidant characteristic peak, brings A into typical curve, calculates T501 oxidation preventive content in transformer oil sample to be measured,

5) adopt staircase waveform voltammetry, under identical condition, successively blank sample, testing sample are carried out to electrochemical gaging, condition determination is: initial potential-0.1V, stop current potential-0.4V, current potential increment 10mV, sampling width 0.001s, time of repose 2s, obtains staircase waveform voltammetry characteristic curve, in the corresponding TXT text of staircase waveform voltammetry characteristic curve, in read-0.3V～0V interval, the peak value of T501 antioxidant feature oxidation peak, brings peak value into respective standard curve, calculates T501 oxidation preventive content.

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