CN102494644A - Method for simply detecting thickness of silver coating of high-voltage isolating switch contact - Google Patents

Abstract

The invention discloses a simple method for detecting the thickness of the silver-plated layer of the contact of a high-voltage isolating switch. Different positions are measured to obtain a set of measurement data, and the set of measurement data includes at least 3 data values; Step 2, according to the measured silver plating layer composition content and thickness relationship curve y=-ln(1-x)/0.1466 (10 ≤y≤25) as the basis, where y is the thickness of the silver plating layer, x is the percentage of Ag content, and the silver plating is judged by the value of the minimum value Agmin of the Ag content and the maximum difference δmax between the Ag content in each set of measurement data Whether the thickness of the layer is qualified, when Agmin≥94.7% and δmax≤4% in each set of measurement data, it is judged that the silver plating layer is qualified. The method of the invention can realize rapid on-site non-destructive testing of the thickness of the silver-plated layer of the high-voltage isolating switch.

Description

A simple detection method for the thickness of the silver-plated layer of the contacts of the high-voltage isolation switch

technical field

The invention belongs to the detection technology of electric equipment, and in particular relates to a simple detection method for the thickness of a silver-plated layer of a contact of a high-voltage isolation switch.

Background technique

High-voltage isolating switches play an important role in isolating power sources, changing system operation modes, switching small load currents, and performing switching operations in power systems. Its usage is usually 2 to 3 times that of circuit breakers. Although its structure is relatively simple, it is also one of the high-voltage equipment that cannot be ignored in power grid operation. It has an important impact on the safe operation of the power grid.

The quality of the silver-plated layer of high-voltage disconnector contacts, especially the thickness of the coating, directly affects the ampacity and service life of the disconnector. At present, the high-voltage isolating switches operating in the national 35-500kV power grids generally have the problem of contact heating, which leads to damage to the conductive part and a decrease in electrical performance. From 2007 to 2011, the infrared temperature measurement of the knife switch of several substations in Hunan Province showed that the temperature exceeded the standard, and the reason was that the thickness of the silver coating was not enough.

Usually, manufacturers of high-voltage isolating switches use the anodic dissolution coulomb method to test the thickness of the silver-plated layer of the contacts. Since this method requires the contacts to be tested on a test bench, the liquid medicine must be replaced and cleaned during the test, which is cumbersome and difficult to test. It takes a long time and is destructive to the silver-plated layer of the contacts. Especially for the assembled isolating switch, the contacts need to be removed and tested before installation, which affects the progress of the project. This method is difficult to apply on site. Therefore, it is necessary to develop a simple on-site non-destructive testing technology for the silver-plated layer of high-voltage isolating switch contacts.

Contents of the invention

The purpose of the present invention is to provide a simple detection method for the thickness of the silver-plated layer of the contact of a high-voltage isolating switch, so as to realize the on-site non-destructive detection of the thickness of the silver-plated layer of the high-voltage isolating switch.

The technical solution adopted to realize the object of the present invention is: a simple detection method for the thickness of the silver-plated layer of the high-voltage isolating switch contact, carried out according to the following steps:

Step 1. Use an X-ray fluorescent alloy analyzer to measure different parts of the silver-plated layer of the high-voltage disconnector contact with its probe to obtain a set of measurement data. This set of measurement data includes at least 3 data values, preferably 5 data value;

Step 2. Based on the measured silver-plated layer composition content and thickness relationship curve y=-ln(1-x)/0.1466 (10≤y≤25), where y is the thickness of the silver-plated layer, and x is the percentage of Ag content , judge whether the thickness of the silver plating layer is qualified by the value of the minimum value Ag min of the Ag content and the maximum difference δmax between the Ag content in each group of measurement data, when Ag min ≥ 94.7% and δmax ≤ 4% in each group of measurement data , the silver-plated layer is judged to be qualified.

The method of the present invention is a set of methods for on-site rapid and non-destructive detection of the thickness of the silver-plated layer of the contact finger of the high-voltage isolating switch based on the X fluorescent alloy analyzer. On-site rapid sampling inspection of the thickness of the silver-plated layer of the contact finger.

The present invention will be further described below in conjunction with accompanying drawing.

Description of drawings

Figure 1 is a fitting diagram of the thickness and composition of the silver plating layer.

Fig. 2 is a criterion diagram of the thickness of copper-based silver-plated layer.

Detailed ways

The simple detection method for the thickness of the silver-plated layer of the high-voltage isolating switch contact of the present invention, its detection process is:

(1) Testing instrument requirements: portable X-ray fluorescent alloy analyzer (XRF): the excitation voltage is 45-50eKv, the excitation power is 2W, and the excitation source is constant;

(2) Preheating: The X fluorescent alloy analyzer must be preheated for 5 minutes after starting up and entering the system;

(3) Sampling: Generally, the main surface of the silver-plated layer of the high-voltage isolating switch contact is used as the working surface to ensure that the probe is facing the sampling part. The probe cannot be moved during analysis and should be as close to the surface as possible; Different parts of the silver layer are measured to obtain a set of measurement data, the set of measurement data includes at least 3 data values, preferably 5 data values;

(4) Alloy analysis: Turn on the X fluorescent alloy analyzer for testing, the detection time should not exceed the instrument setting time, and the reading needs to be carried out when the content of Ag and Cu elements tends to be stable. If ±2σ>10%, the reading is considered invalid ;

(5) Probe cooling: Under normal circumstances, the X fluorescent alloy analyzer should stop for ten minutes every time it works for ten minutes;

(6) Based on the composition content and thickness relationship curve of the silver plating layer y=-ln(1-x)/0.1466 (10≤y≤25), where y is the thickness of the silver plating layer, x is the percentage of Ag content, and The value of the minimum value Ag min of the Ag content and the maximum difference δmax between the Ag content in each set of measurement data determines whether the thickness of the silver plating layer is qualified. When Ag min ≥ 94.7% and δmax ≤ 4% in each set of measurement data, The silver-plated layer was judged to be qualified.

Detection principle:

The portable X-ray fluorescent alloy analyzer (XRF) analyzes the composition of the coating, and its analysis signal (that is, the composition of the silver coating measured for it) depends on 4 factors: the chemical composition of the coating, the chemical composition of the coating substrate, the thickness of the coating and the analysis The excitation source of the instrument. When the composition of the coating Ag and the matrix Cu are determined, and the excitation source of the portable X-ray fluorescent alloy analyzer (XRF) is also determined, the analysis signal only depends on the thickness of the Ag coating. Therefore, when the same type of portable X-ray fluorescent alloy analyzer (XRF) is used to measure the silver coating of the contact of the high-voltage isolation switch, the change of the analysis signal is only a parameter of the thickness of the silver coating.

By preparing samples with different silver coating thicknesses (silver coatings are 12.2 μm, 15.9 μm, 19.0 μm, 19.5 μm), and accurately measuring the coating thickness by metallographic measurement methods, and finally using a portable X-ray fluorescence alloy analyzer (XRF) Obtain the component responses of different thicknesses of silver-plated layers, see Table 1 below. Among them, the excitation voltage of the X portable X fluorescent alloy analyzer (XRF) is 45-50eKv, the excitation power is 2W, and the excitation source is constant.

Table 1 The relationship between Ag composition content and thickness of silver-plated layer

Ag/% 0 83.66 90.00 93.93 94.23 Silver layer thickness/μm 0 12.2 15.9 19.0 19.5

Set the thickness of the silver plating layer as y, the percentage of Ag content as x, and fit the above data, the relationship curve and functional relationship between the coating thickness and the Ag content measured by the portable X-ray fluorescence alloy analyzer (XRF) can be obtained: y= f(x). The fitting curve diagram is shown in Figure 1. The functional relationship is as follows:

y=-ln(1-x)/0.1466 (10≤y≤25, R ² =0.9997)

According to the functional relationship, the thickness of the copper-based Ag coating (the thickness of the Ag coating is 10 to 25 μm) can be quickly and easily measured. From the above formula, the curve of copper-based silver plating thickness and Ag component content in Figure 2 can be obtained.

According to the regulations of the State Grid Corporation of China, the thickness of the silver-plated layer of the contact should be greater than or equal to 20 μm. It can be seen from Figure 2 that the Ag content of the coating is 94.7%, and this Ag composition is the criterion for the on-site thickness measurement of the silver-plated layer.

For the uniformity of the thickness of the silver-plated layer, usually a set of data measures 3 values, preferably 5 values. According to the statistical analysis of the test values, the uniformity of the thickness of the contact surface of the contact should not be greater than 4% of the Ag content.

To sum up, it can be seen that the criterion for the measurement of the thickness of the silver-plated layer of the contacts of the high-voltage isolation switch is that the minimum value of the Ag content, Ag min, should be greater than or equal to 94.7%, and the maximum difference of the Ag content of each group of test values should be 94.7%. The value δmax should be less than or equal to 4%.

Claims (2)

1. A kind of high voltage isolation switch contact silver coating thickness simple detection method is characterized in that carrying out according to the following steps:

Step 1, use X fluorescence alloy analysis appearance are measured to obtain one group of measurement data the different parts of the silver coating of high voltage isolation switch contact with its probe, and this group measurement data comprises 3 data values at least;

Silver coating component content and thickness relationship curve y=-ln (1-x)/0.1466 (10≤y≤25) that step 2, foundation are measured are foundation; Y is a silver coating thickness in the formula; X is an Ag content percentage; Numerical value with the maximum difference δ max between the Ag content in the minimum value Ag min of Ag content and the every group of measurement data judges whether silver coating thickness is qualified, when Ag min>=94.7% in every group of measurement data and δ max≤4%, judges that silver coating is qualified.

2. high voltage isolation switch contact silver coating thickness simple detection according to claim 1 method is characterized in that this group measurement data is 5 data values in the said step 1.

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