Why do we need to first connect the grounding wire and then connect the broken wire when grounding the instrument on site?
Answer: During on-site testing, due to the high induced voltage between the fracture of high-voltage switches (especially above 220kV) and the ground, this voltage value is large and the energy is small, but it is enough to threaten the safety of the instrument itself. Inside the instrument, there is a discharge circuit connected between the fracture signal input terminal and the ground. First, connect the ground wire, and in reality, prioritize the connection of the discharge circuit. At this point, even if a high voltage is induced at the fault signal line, it can be discharged to the ground through the discharge circuit, ensuring the safety of the instrument’s fault channel.
2. How to determine if the instrument port is normal?
Answer: Select [Test] – [Close Test], and there are 12 real-time status displays at the bottom of the instrument’s LCD screen.
In this interface, it is possible to check whether the fracture channel of the instrument is intact. If the fracture input is suspended, it should display “open”. If there is a short circuit to ground, it should display “closed”. So short-circuit each fracture to ground and observe the changes in the status display to determine if the instrument fracture time channel is normal.
3. What is the initial opening (closing) speed? What is the difference between defining the opening (closing) speed of a switch based on time and distance periods?
Answer: The so-called initial opening (closing) speed refers to the average speed of the high-voltage switch during a certain period of time (or distance) after (or before) the initial opening. If time is used as the definition standard, IEC standards and China’s national standards generally define it as the average speed of 10ms before and after closing. Based on the different definitions of certain countries or switch manufacturers, our company’s instruments can be redefined by adding the degree of addition through computer and matching speed definitions. It can be defined as both a time period and a distance period, providing flexible and convenient speed testing for high-voltage switches. Taking a vacuum switch as an example, the opening distance of a 10kV switch is generally around S=11mm, and its initial closing (opening) speed is defined as the average speed of 6mm before (after) the initial closing. Some manufacturers also define it as the following:
(1) Take the average speed of the entire process when closing, and take the average speed of 6mm immediately after opening;
(2) Close the switch and take the average speed of the entire process, and open the switch and take the average speed of the entire process;
Tip: With the speed definition adding program function, it is also convenient to conduct speed testing based on specific vacuum switches. In addition, during the speed test of the vacuum switch, the average speed of the entire opening process is very low due to the buffering mechanism acting during the opening process. The average speed before the buffer mechanism takes effect during the opening process of a vacuum switch is generally defined as 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 6mm just after opening is closer to the true value. Due to the fact that the opening distance of 35kV vacuum switches is generally around S=22mm, all the values 6 defined for the speed of 10kV vacuum switches above can be changed to 10 or 11.