Landodian Company, Arashizaki Company, Hokuri Company, etc. held power industry meetings. About three hundred people came to the conference hall. Landian company spokesman Yan Zhuoshou is fifty years old, has a lot of gray hair, wears a suit, and has a natural smile on his face. He said: "In order to better set up and maintain electrical equipment, the city of Shengshi City has been established The underground city provides a dedicated space for power supply lines and electrical equipment. For us electric workers, there are several benefits. First, we no longer have to squeeze into a small space to repair lines in the future. Second, the lines are concentrated and it is easy to find the corresponding lines. Third, using new power quality testing equipment makes it easier to find problems with power supply lines."
After the speech, the audience applauded for a long time. The people who came to the meeting were technicians and engineers from the electric power company, and they knew the significance of this matter. The original wiring layout was small and scattered, making it difficult to repair problems.
Then the department managers of each company spoke, explaining how to set up new construction plans and maintenance plans for the power system. Until the end of the meeting three hours later.
After the meeting, Yong Han, Fu Shuo, Qu Fei, Shi Qiubing, and Zhu Yan from Landian Company discussed together that the new power system has been built, there are many new construction and maintenance standards, and there are many things to learn. Yong Han and Shi Qiubing are in the technology department, Fu Shuo and Qu Fei are in the engineering department, and Zhu Yan is in the human resources department.
It has begun to rain lightly outside. Zhu Yan said to Shi Qiubing next to her: "My umbrella is broken? Can we hold an umbrella together?"
Shi Qiubing said, "The umbrella is broken? I'm a repair expert. Let me take a look." He took the umbrella over, straightened the iron bars, and put the spring back. Said: "Look, it's fixed, here you go, you're welcome."
Yonghan said to him from behind: "Hey, you only heard the first sentence, didn't you hear the next one?"
Shi Qiubing said, "What's that last sentence?" Zhu Yan rolled her eyes and left. Shi Qiubing didn't react, so he held up his umbrella and left.
Qu Fei came over and said, "Today's young people have too low emotional intelligence and understanding. Others will just hold an umbrella with you, and you can fix it for them and leave."
Yonghan said: "Yes, I feel anxious just looking at it."
Fu Shuo walked up behind Yong Han and Qu Fei and said, "Yong Han, please lend me an umbrella. I have something to do. You two go back first."
Yonghan said, "I'll go back with you."
Fu Shuo winked at Yonghan. Yonghan didn't understand.
Fu Shuo said: "Forget it, you go first." Yonghan and Qu Fei took umbrellas and went back.
Fu Shuo said, "I have the nerve to talk to others. I'm just worried because of you two."
One day after get off work, Yonghan met his classmate Ying Yang. Ying Yang had already started a family and was doing architectural design at Shengshi City Design Institute. Yonghan is rather envious. Yonghan works at Landian Company and is busy all the time. I haven’t started a family yet, and I feel like there’s always something missing in my life. "I see it's a good time in life for you to start a family and start a business."
Ying Yang said: "Don't always look at other people's superficial beauty. I am very tired every day. Sometimes I draw pictures until two o'clock in the middle of the night. Have you heard that there are always abnormal power outages in the city recently. Sometimes, there are unfinished drawings in the computer. The drawing just clicked and disappeared.”
Yonghan said: "I know that our company is investigating this matter recently. Some transformers may need to be repaired."
"Haven't you found the reason yet?"
"We are going to the dungeon tomorrow to check the city's main transformer."
Dungeon is the name for underground passages extending in all directions. The underground city has cables, water pipes, network cables, and telephone lines. Since it is troublesome to lay these pipelines on the ground, they are all moved underground. The space is large and there is enough space for electricians and plumbers to travel and repair. Landian Company has installed many transformers in the underground city, and there are some storage rooms where maintenance tools and spare cables are placed.
"Then I wish you all the best, I haven't gone down to see it yet."
"Everything is beautiful, the humid space, and the dense wires. If you want to go, you can go tomorrow. But it's too dangerous and you can't go near the high-voltage area."
"Forget it, be careful."
Yonghan arrived at the company in the afternoon. Lao Fang, the head of the department, said to him: "We are going to the underground city to check the city's main transformer. Fu Shuo and Qu Fei will go with you."
"Let Qu Fei go? She's not very skilled, so it's more dangerous."
"What, are you looking down on people?" Qu Fei's voice came from behind.
"No, I'm more concerned about you. After all, this is also a laborious job." Yonghan said.
"It doesn't matter, sooner or later you have to practice this technique. See you tomorrow."
Lao Fang pulled Yonghan aside and said: "Yonghan, although you have done a lot for the company, you have always been the first to take the lead. You are not young anymore, and you can no longer be so masochistic and single."
Yonghan smiled and said, "You have also learned this word, okay, thank you, I will do it as soon as possible."
The next day, Yonghan, Fu Shuo, and Qu Fei changed into electrician uniforms. The company's van took them to the dungeon entrance.
Climb down the ladder, next to the damp wall, into the pipe, there is some moss underneath. Walking on the ground, the sound of footsteps reached far away and reflected back, making a dull echo. Go through the isolation door, the security door, and through a hidden door to reach the main transformer.
Yong Han, Fu Shuo, and Qu Fei were wearing work clothes and carrying portable power recorders, walking in the tunnels of the dungeon.
I opened two more doors and saw the main transformer with input and output lines. High-voltage lines and low-voltage lines are densely packed and criss-crossed.
"Is this a short circuit or an open circuit?" Fu Shuo asked.
"Unlike a short circuit, there is no record of large currents flowing." Information from the main transformer was passed to a portable recorder. Yonghan looked at the portable recorder and said.
Portable recorders are important equipment for current analysis, calculation, and system analysis. It provides effective means for the maintenance of power systems, protection of power equipment during operation, current analysis, and accident early warning.
On electrical circuits, due to various reasons, the current suddenly increases when they are connected or collided, which is called a short circuit. When a short circuit occurs, it usually takes 3 to 5 seconds for the power system to transition from a normal stable state to a short circuit stable state. During this transient process, the changes in short-circuit current are complex. It has many components, and its calculation requires the use of electronic computers. The maximum instantaneous value of the short-circuit current will appear about half a cycle after the short circuit, which is called the inrush current. It generates a lot of electrical power. There will be a short circuit if the phase wires collide with each other; if the phase wires collide with the ground wire, with the ground conductor or with the earth, there will be a short circuit. When the short-circuit current suddenly increases, the instantaneous heat release is very large, which greatly exceeds the heat generated during normal operation of the circuit. It can not only burn the insulation, but also melt the metal, causing combustible materials to burn and cause a fire.
The portable recorder did not show a similar occurrence of maximum instantaneous current.
"The low-voltage side supplies power to the southern part of the city. The power went out for a while and then came back."
“There’s a backup power grid.”
"There is no record of the backup power grid being activated."
"What does that mean? The voltage dropped by itself, and then rose again? Who stole the electricity?"
"On the high-voltage side, the power supply cables were unplugged in several places."
"Then this is man-made."
"Maybe. I don't know if it was intentional, or if someone else forgot to connect it during maintenance."
Qu Fei said, "Look, the outer sheathing is damaged in many places here."
"You said, is there any way to steal electricity like this? Remove the outer sheath and take it out directly? Then why are there so many openings and a lot of damage?"
"What kind of tool do you think this was opened with?"
"It's not a knife or pliers, it's claws, teeth or something like that."
"You chew it with your teeth? Aren't you afraid of being electrocuted?"
Yonghan summarized, "The high-voltage side cable was pulled out, and the sheath layer on the low-voltage side was damaged in many places."
"Is it burnt due to high voltage? It's due to thermal aging."
These transformers are devices that use the principle of electromagnetic induction to change AC voltage. They are mainly composed of primary coils, secondary coils and iron cores. In electrical equipment and wireless circuits, it is often used to increase and decrease voltage, match impedance, and safety isolation. In a generator, whether the coil moves through a magnetic field or the magnetic field moves through a stationary coil, an electric potential is induced in the coil. The values of the magnetic flux remain unchanged, but the amount of magnetic flux intersecting the coil changes. A transformer is a device that uses the principle of electromagnetic mutual induction to transform voltage and current.
So why did this transformer fail? They troubleshoot one problem at a time.
Circuit fault: The circuit fault of the transformer mainly refers to the short circuit at the outlet of the transformer, the short circuit to ground between the leads or windings inside the transformer, and the short circuit between phases, which leads to the occurrence of faults. For the problem of short circuit at the low-voltage outlet of the transformer, in order to solve the problem, the windings at the faulty location are generally replaced. When the fault is serious, all windings may need to be replaced as necessary.
Winding failures: Specifically, the welding joints of the joints are extremely prone to cracking problems, phase-to-phase short circuit problems, turn-to-turn short circuits, winding ground faults, etc. Reasons include: There is a problem with the insulation of the transformer; there is debris in the winding and the insulator is aging; there are problems with the winding due to deformation: the winding is affected by water vapor; the temperature of the transformer is high.
Transformer oil leakage failure: Oil leakage from power transformers will cause some subsequent problems, such as serious environmental pollution to the air itself, and may also cause a large amount of waste of resources.
Fault of excessive temperature at the joint: The unstable connection of the current-carrying joint of the transformer causes the temperature at the joint to rise rapidly, even exceeding the ignition point of the joint, causing the joint to burn out. Therefore, it is necessary to observe the temperature changes of the current-carrying joints of the transformer to ensure that the temperature of the joints changes within the normal value range.
Problems such as winding failure, oil leakage, and excessive temperature at the joints have all been eliminated. It may be a circuit failure.
But it doesn't look like a short circuit.
Several people were thinking and didn't know what was going on. At this time the isolation door suddenly closed.
Yonghan looked at the door and said, "Is there some abnormal intrusion?"
Qu Fei said: "Did anyone come in? I didn't see it."
Fu Shuo said: "Maybe there are rats."
Yonghan said: "What kind of system is this? How do we get out?"
Fu Shuo said: "There may be electric sparks. When there is an open fire alarm, some doors will be closed."
Qu Fei said: "Then don't you consider whether there is anyone inside?"
Fu Shuo said: "There is a side door to go out from here."
But when he pushed the door, it couldn't be opened. Yonghan only pushed open a crack and shined a flashlight inside.
Yonghan said: "The telephone pole blocked the side door."
Qu Fei said: "It seems like there are mice, vaguely visible."
The mouse probably knocked down the telephone pole.
"There is another door, but it's a long way around." Yonghan took out the drawing of the underground passage. May pass through the water pump room, control center, and small transformer area.
Qu Fei said: "Should we check around here? Or should we go back?"
Yonghan said: "We can only go back along the road on the map."
Turn on the map function on the portable recorder to provide feasible walking routes for this intricate underground passage. Since the satellite positioning signal was relatively weak, I had to draw the map in advance and input it into the portable recorder.
Just like a car driving on the road outside, using satellite positioning. When we got to the garage, there was no signal. Some underground garages have electronic maps that are connected to the car, so the car can continue to navigate. If there is no electronic map in the underground garage, the car will send out a signal: the signal is weak and it is temporarily unable to obtain navigation information.
Water supply pump room
A few of them entered a room and heard the faint sound of a water pump running. Looking around carefully, they saw that it was the water supply pump room.
A woman was checking the water pump. Shen Yi was written on her overalls.
"Who are you?" she asked.
Yonghan said: "We are checking the power supply system and checking the reasons for repeated power outages. Are you here also checking for water pump failure?"
Shen Yi said: "Yes, sometimes there is a loud noise."
Yonghan said: "Is the motor broken, or is the shaft and bearing broken?"
Shen Yi said: "When I came to measure the vibration signals, they were all good, not bad, but there was a sound."
Yonghan said: "Did the water pipe crack?"
Shen Yi said: "I haven't found anything. The flow rates at the inlet and outlet are equal, and there is no leakage."
Yonghan said: "That is to say, sometimes there is a noise. If it is a mechanical failure, it will not recover on its own."
"It's like a magnet comes and the motor fails. Then the magnet leaves again and the motor recovers." Fu Shuo said.
"But the bracket here has signs of being stretched and bent." Yonghan said, shining a flashlight on the pipe.
"Who is so strong? Is the equipment too heavy and bent?" Shen Yi said.
"If it's man-made. The bracket is connected to the pipe, maybe it's trying to climb up the pipe, maybe it's trying to pull the pipe apart."
"There's nothing else that can be seen. Let's move forward." Fu Shuo said.
