High Voltage Circuit Breaker Mechanical Characteristics Tester Test Solution

1 Overview
The mechanical characteristics test of high-voltage circuit breakers is an indispensable part of the switch production, installation and commissioning process, and is of great significance for detecting and identifying the mechanical characteristics of circuit breakers. The inherent opening (closing) time, speed and stroke, and the quality of the operating power supply (I-U curve of the operating winding) are important parameters for whether the high-voltage circuit breaker can work reliably. Due to the short action time and large vibration of high-voltage circuit breakers, the early detection devices lacked reliable detection means for the detection of these transient parameters, especially the detection of speed and displacement, due to the limitations of sampling technology and sensor technology. With the development of modern industrial technology, the new circuit breakers currently produced have small opening distances and fast speeds, and the requirements for high-voltage circuit breaker mechanical characteristics testers are more stringent. Therefore, the market urgently needs a new high-voltage circuit breaker test instrument with advanced testing principles, convenient on-site operation, and reliable measurement data.

With the development of computer technology and sensor technology, it is possible to realize the non-contact high-voltage circuit breaker mechanical characteristics tester based on process measurement. After repeated market research and long-term tracking of the status quo and development trend of displacement sensors, Beijing Hezhicheng Technology Co., Ltd., Xi'an High Voltage Power Supply Bureau Substation Repair and Testing Institute, and Jiaozuo Power Plant Maintenance Branch jointly proposed an implementation plan for a non-contact high-voltage circuit breaker mechanical characteristics tester based on process testing, and achieved satisfactory results after nearly a year of research and testing. The instrument is designed and manufactured according to the relevant test items and term definitions in the national standards GB 3309-1989 and GB 1984-1989. The items it can detect and the data processing are better than the relevant national standards. The measurement method for speed and displacement is unique. The sensor does not need to contact the action connecting rod of the circuit breaker, making on-site measurement convenient and reliable, and can realize process measurement, which changes the shortcomings of the previous state measurement method.

2 Based on characteristic state measurement method

State measurement means that the detection device can only analyze, process and judge the measured parameters based on some specific state data, and does not record or respond to other non-characteristic state data. At present, the contact tester based on characteristic state data is widely used to test the mechanical characteristics of high-voltage circuit breakers. The principle of this tester is simple and easy to implement, but it can only make a qualitative judgment on the rough situation of the measured parameters of the equipment. In addition to being acceptable in the measurement of inherent opening and closing, it is powerless to distinguish mechanical action time and electrical response time, and the test of other types of parameters is also unsatisfactory.

Although with the popularization of computer technology, many electrical measuring devices have been digitized, but limited by the level of computer technology and sensor technology when the instruments were developed, the testing principles of many measuring devices are basically a simple reinterpretation of traditional analog testing methods from a digital perspective, and they have not fully exploited the advantages of digital measurement methods in data storage and processing to make appropriate extensions and functional expansions. Traditional high-voltage circuit breaker mechanical characteristics testers are no exception.

The high-voltage circuit breaker mechanical characteristic tester based on state measurement cannot meet the requirements of some dynamic characteristic tests, frequent disturbances, and multi-parameter joint measurement tests.

(1) Test of the inherent time of the circuit breaker. By definition, the inherent time refers to the time from the issuance of the action command to the separation or contact of the first break. The curve is shown in Figure 1. No distinction is made between the circuit response time and the inherent action time of the device itself. The timing start of the inherent time is triggered by the operation command, and the timing stop is triggered by the first state change of the break signal, that is, the inherent time T=t1+t2. From the voltage curve of the operating winding, time t1 is the circuit response time. Reasonably speaking, the inherent action time of the circuit breaker should end when the position of the last break changes. Due to the limitations of the state test, we are forced to ignore the circuit response time and the break phase difference time in this test. This is actually a compromise solution.

Figure 1 Intrinsic time curve

Figure 1 Intrinsic time curve

Figure 2 Displacement-time curve

(2) Speed ​​test. Speed ​​is a time quantity. Currently, the average value is obtained by calculating the time it takes to complete a fixed displacement. The displacement-time curve is shown in Figure 2. Since the state test requires a clear state flag, the moment the command is issued naturally becomes the starting point of the displacement movement, and the speed can only be obtained through V=S1/(t1+t2). Because, in the state test, the characteristics of the moment t1 or the moment of the origin of the action are not obvious and cannot be captured; in addition, there is a lack of state flags required for the state test within the t2 time corresponding to S1. Therefore, the speed can only be obtained through the average value, which is contrary to the definition of the just-opened/just-closed speed defined based on the movement moment.

(3) Performance test of the operating power supply. Whether the circuit breaker can operate correctly is due to both its own reasons and the operating power supply (such as insufficient operating power supply capacity, aging batteries, or small wire cross-section). How to determine which factor is the cause? It is impossible to test the performance of the operating power supply using state measurement, because the state test does not consider what happened during the operation. However, if we can record the I-U curve of the operating winding during the operation based on the process test,

3. Process measurement based on

3.1 Process measurement:

The so-called process measurement is relative to state measurement, and its core has two aspects: ① Record the whole process of the measured parameters; ② All measured parameters are based on the same reference system, which can realize the correlation between related parameters. In the process measurement thinking, the traditional event calibration method (characteristic state or characteristic data) is abandoned, all measured quantities are based on the same reference system (mostly time reference system), all event processing is based on this reference system, and all states or data in the entire test are treated equally and continuously, which simplifies the test logic and creates the possibility for mutual calibration between related quantities. It is very simple to deal with the above three problems with the process measurement thinking.

(1) In the test of the inherent time of the circuit breaker, since we record the state transition of the breaker and the change curve of the operating winding voltage at the same time, and these two quantities have a unified time coordinate, it is easy to accurately obtain the circuit response time and the action time of the circuit breaker itself.

(2) In speed testing, we can accurately unify the timing start point and the displacement moment origin. It is not necessary to define the timing start point at the time when the operation instruction is issued as in the state test. More importantly, the instantaneous speed at any time can be calculated by the slope of the tangent of the displacement-time curve, rather than the average speed. In addition, the bounce of the contact can also be reproduced in the displacement-time curve.

(3) By recording the entire process of the voltage and current curves on the operating winding and the associated records of other parameters, it is possible to clearly distinguish whether the problem is with the operating power supply or the operating mechanism, and to make a scientific evaluation of the electrical characteristics of the winding and the performance of the operating power supply.

In fact, electrical equipment will show a lot of valuable information in the transition process of reaching a certain state under the stimulation of an excitation source. This information is often more valuable than stable state information. In the past, due to limitations in testing methods and technical levels, transition information was not recorded and used. With the development of technology, it has become possible to record transition information.

3.2 Non-contact method

By using the process measurement method, the high-voltage circuit breaker mechanical characteristics tester can not only realize the scientific and accurate testing of parameters, but also realize the non-contact testing of the displacement and speed of the mechanical characteristics of the high-voltage circuit breaker.

At present, the mechanical characteristic tester of high-voltage circuit breakers basically adopts the contact method to obtain the displacement and speed information of high-voltage circuit breakers in the displacement and speed test, that is, the displacement sensor must be installed in contact with the linkage part of the circuit breaker, and the movement information of the circuit breaker is sensed by contacting the movement of the circuit breaker. Due to the different structures and shapes of high-voltage circuit breakers, this method is very difficult or even impossible to implement in on-site testing.

The principle of light reflection deviation can be used to realize non-contact testing of the speed and displacement of high-voltage circuit breakers. The principle diagram of photoelectric measurement of displacement and speed is shown in Figure 4.

Figure 4 Schematic diagram of photoelectric measurement of displacement and velocity

As can be seen from Figure 4, when the object under test moves from position h2 to position h1, the light reflected from the object under test to the test plane moves from S2 to S1. Through geometric relationships, it is easy to calculate the relationship between the displacement h=h1-h2 of the object under test and the perceived displacement S=S1-S2 of the test plane: h=S/(2tgθ). Since the value of θ is known and S is measurable, the displacement h of the object under test can be obtained through the offset displacement of the reflected light. Since the speed of light is very fast, as long as the scanning speed of the test plane is fast enough (20 kHz, i.e. 50μs), non-contact testing of the displacement and speed of the moving object can be achieved.

The benefits of realizing
non-contact displacement and velocity testing are: ① No tedious on-site installation is required; ② Adapts to all structures (excluding those without exposed linkage mechanisms); ③ Free from interference from severe vibration; ④ Does not cause any obstacles to the operation of the circuit breaker.

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4 Composition of process measuring instruments

(1) Power supply unit: AC power input, the operating power supply is continuously adjustable at 48-250 V AC and DC, and the maximum output current can reach 20 A. When the current of the circuit breaker opening and closing circuit under test exceeds this current value, an external operating power supply can be connected. The voltage stabilized power supply (constant voltage source) has the characteristics of small size, light weight, large output current, high accuracy and good stability. Since the operating power supply and characteristic parameter measurement are integrated, the circuit breaker closing and opening can be directly controlled, and all characteristic parameters can be measured at the same time, and the measurement results can be displayed or printed.

(2) Measuring unit: The measuring unit includes a travel (or displacement) measuring circuit, a timing circuit, and a switch quantity (opening and closing of the circuit breaker) access circuit. The circuit breaker only needs to be operated once to obtain all the measurement data of the corresponding operation.

(3) Central processing unit: Calculates and judges each measurement parameter according to the pre-entered program, and is responsible for communication, connection, coordination, fault diagnosis, and receiving and issuing instructions between the various units in the instrument.

(4) Output unit: It has a large screen display that can display all mechanical characteristic parameters in Chinese characters. The printer is directly embedded in the panel and can print all closing and opening parameters in Chinese characters in table form. It can also display various faults such as wiring errors, refusal to close and refusal to open, data overflow, etc. in Chinese characters.

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5 Main technical indicators

Scanning time range 0～1000ms, accuracy 80μs; ​​displacement range 0～400mm (100～500 mm), accuracy 0.01mm; operating voltage input range DC-400～+400V, accuracy 0.5V; operating current input range 0～120A, accuracy 0.02A; sampling frequency greater than 10kHz; data storage space 6MB (expandable to 14～30 MB); 8 analog channels (4～20mA, 0～5V, 0～10V optional); 8 switch channels for input and 6 for output; working power supply voltage AC220±10%; maximum power consumption of the instrument 150W; working environment temperature -20～+85℃; relative humidity not more than 80%. 

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6 Conclusion

Since the non-contact high-voltage circuit breaker mechanical characteristics tester based on process testing scans, tracks and records the entire process of switch action and unifies the relevant parameters under the same reference system (time), it can not only judge the response results of the switch control circuit and operating mechanism, but also reproduce the transition process. This is of great significance for in-depth and comprehensive research on the action performance of the switch. At the same time, since it realizes non-contact measurement of speed and displacement, it provides a simple, practical and scientific testing method for on-site speed and displacement testing of high-voltage circuit breakers.