1. When the instrument is grounded on site, why do we need to connect the ground wire first and then the break wire?

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Answer: During field tests, there is often a high induced voltage between the fracture of a high-voltage switch (especially above 220kV) and the ground. This voltage has a large magnitude and small energy, but it is enough to threaten the safety of the instrument itself. Inside the instrument, there is a leakage circuit connected from the fracture signal input end to the ground. By connecting the ground wire first, the leakage circuit is actually connected first. When the fracture signal line is connected at this time, even if a high voltage is induced at the fracture, it can be discharged to the earth through the leakage circuit, thereby ensuring the safety of the fracture channel of the instrument.

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2. How to judge whether the instrument port is normal?

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Answer: Select [Test]-[Close Test], and there will be a real-time status display of 12 fractures at the bottom of the LCD screen of the instrument.

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In this interface, you can check whether the fracture channel of the instrument is intact. If the fracture input is floating, it should display “open”. If it is short-circuited to ground, it should display “close”. Therefore, short-circuit each fracture to ground and observe the changes in the status display to determine whether the fracture time channel of the instrument is normal.

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3. What is the initial opening (closing) speed? What is the difference between defining the opening (closing) speed of a switch by time period and distance period?

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Answer: The so-called opening (closing) speed refers to the average speed for a period of time (or a distance) just after the high-voltage switch opens (just before opening). If time is used as the definition standard, IEC standards and my country’s national standards are generally defined as the average speed of 10ms before and after the combination. According to the different definitions of some countries or some switch manufacturers, our company’s instruments can be redefined by adding the degree of computer and supporting speed definition. It can be defined as either a time period or a distance period, which can provide speed testing for high-voltage switches flexibly and conveniently. Taking the vacuum switch as an example, the opening distance of a 10kV switch is generally S = about 11mm, and its just-closing (opening) speed is defined as the average speed of 6mm before just closing (just after opening). Some manufacturers also define the following categories:

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(1) For closing, take the average speed of the whole process, and for opening, take the average speed 6mm just after opening;

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(2) The average speed of the whole process is used for closing, and the average speed of the whole process is used for opening;

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Tip: With the speed definition adding program function, it is also convenient to conduct speed tests based on specific vacuum switches. In addition, when performing a speed test on the vacuum switch, due to the buffer mechanism acting during the opening process, the average speed of the entire opening process is very low. It is generally defined that the average speed before the buffer mechanism takes effect during the opening process of the vacuum switch is the average speed of the entire process, that is, the average speed of the entire process is taken for closing, and the average speed of 6 mm just after opening is taken, which is closer to the true value. Since the opening distance of the 35kV vacuum switch is generally about S=22mm, all the above value 6 in the definition of the 10kV vacuum switch speed can be changed to 10 or 11.