How to speed up the development and construction of China's UHV power grid and new energy to ensure the safe, reliable and stable operation of the power grid? How to further improve the traditional breaker breaking time, to solve the impact current is too large? In the face of the common attention of the world's power science and technology community, the good news recently came from the Xi 'an High Voltage Electrical Equipment Research Institute: 363kV/5000A/63KA rapid vacuum circuit breaker has made key technical breakthroughs, and the short-circuit current time of breaking has been increased from 60 milliseconds to 10-20 milliseconds.

What does 60 milliseconds and 20 milliseconds feel like? According to the definition of the medical community, it takes about 0.1 seconds for normal people to blink their eyes, that is, 100 milliseconds, 60 milliseconds means that it is too late to complete a blink, and 20 milliseconds is only equivalent to one eyelid flutter. In the instant of electric fire, the fast vacuum circuit breaker successfully completes the opening action, successfully cuts out the power grid fault line, and ensures the stable and safe power supply of power grid equipment and thousands of households.

If you want to do it, you must do it best

"Although it has not been officially certified, it is not an exaggeration to say that it is' the world's first ultra-high voltage fast vacuum circuit breaker '!" Huang Yongning, one of the participants of the project and head of the science and Technology Department of the Ningxia Institute of Electric Science and Technology of the State Grid, said proudly.

The 363kV/5000A/63KA rapid vacuum circuit breaker project began in 2011, and was implemented by 51 R & D teams from power grid enterprises and scientific research institutions, which lasted 7 years to overcome difficulties and continuously broke through a number of worldwide technical problems. According to Huang Yongning, the technology achieved the short-circuit current breaking ability from the research and development goal of 63 kiloampere to 80 kiloampere, breaking through the current traditional circuit breaker the maximum ability to break 63 kiloampere short-circuit current; The short-circuit current is increased from 60 milliseconds to 10-20 milliseconds, breaking through the world's current range of vacuum circuit breakers the fastest short-circuit current speed; It realizes the direct breaking of short circuit current at 363 kV voltage level, which will make a new breakthrough in the application of ultra-high voltage power grid..."

Lightning acts like a nerve center

The fast circuit breaker operation time from 60 milliseconds to 20 milliseconds, for ordinary residential electricity, almost imperceptible, and shorten the fault duration of 40 milliseconds, for industrial enterprises production electricity is of great significance.

According to relevant data, in the past 20 years, the loss caused by voltage dips (including short-time voltage interruptions) in the world accounted for about 60% of the total loss of industrial samples. For example, in the late 1990s, a British paper mill due to a voltage drop lasting only 0.3 seconds caused the key load device trip, production line operation interruption, the direct economic loss to the enterprise up to 140,000 pounds; According to the survey of Beijing Capital Iron and Steel plant by China Electric Power Research Institute, voltage sag occurred 19 times in 2002, and the direct economic loss caused by each time amounted to 2-3 million yuan.

When the short circuit fault occurs, the 363kV/5000A/63KA fast vacuum circuit breaker detects the short circuit current, predicts the current zero within 2 milliseconds, the controller responds quickly, issues the opening command, the ultra-fast electromagnetic repulsion mechanism receives the opening command and begins to act, and the opening operation is completed within 5 milliseconds, that is, the fault current is disconnected.

Just like a person's finger is suddenly pricked by a needle, the human nerve center quickly transmits the information to the brain, and the brain receives the instruction to direct the finger action, completing the finger action from the needle tip within 5 milliseconds, thus protecting the finger from greater damage.

Scientific and technological development of the road acceleration

Traditional circuit breaker breaking time is long, the impact current is large, when the short-circuit fault occurs, the relay protection device operation time is usually 10 to 20 milliseconds, the circuit breaker inherent opening time is 30 to 60 milliseconds, the arc time is 10 to 20 milliseconds, and then the fault cutting time is as long as 60 milliseconds to 140 milliseconds.

According to industry insiders, for the domestic 50 Hz power grid, the maximum impulse current has been reached within 5 to 10 milliseconds after the short circuit. For the higher grade 363 kV voltage grade line, the fastest opening time of the more advanced sulfur hexafluoride circuit breaker at home and abroad is also more than 50 milliseconds. This means that before the circuit breaker is broken, the system's equipment has been hit by five or six times of large current, and the consequences can be imagined.

"From 2011 to determine the development of fast vacuum circuit breaker, to 2013 fast circuit breaker opening time test only increased by 5 milliseconds, every 1 millisecond or the voltage level is a little higher, there will be jitter phenomenon, fast disconnection can not self-healing, equipment does not act and other problems, can be described as difficult."

In order to break through the research and development barriers, the scientific research team led by Ai Shaogui, chief expert of Ningxia Electric Power Co., LTD., and honorary president of Ningxia Electric Research Institute, conducted 15,000 tests in 7 years, successfully broke through a number of key core technologies, and finally achieved the goal of developing a fast vacuum circuit breaker prototype.