To put it bluntly, the protection device is a bit like a fuse. If there is a short circuit, quickly burn the fuse first and the circuit will be broken. Those precious power equipment will not suffer any harm, and there will be no fire at home. However, the protection device will not be really burned. Its function is to direct the switch to trip, which is the same as the fuse burned.

When it comes to line protection, its core significance is naturally to protect large "fuses" of equipment including "wires", "cables", "line switches" and other equipment. Cut off the switch in critical situations when a line failure occurs, which indirectly ensures the safety of surrounding lines and transformers. Without this thing, the speed of your power grid building cannot keep up with the speed of "exploding" the power grid.

There are many factors that "explode" the power grid, maybe it is lightning strike, counter-attack, thunder strike, chain thunder, maybe it is wind skew, ice covering, wildfire... and birds without eyes, kites with short lines, old farmers stealing wires, etc.

Once these terrible accidents occur, lightning protection facilities, bird repelling devices, wind and ice protection designs and national laws fail to prevent the above, the most terrible line breakage, short circuit failure, overvoltage, overcurrent and other abnormal phenomena will occur. The instantaneous large current will sweep over like a tsunami, and finally the word "explosion" is highlighted. It is not enough to explode if you are not finished. Chain accidents are the most terrible, one is connected to the other and explode like dominoes.

Therefore, it is absolutely necessary to configure relay protection devices on transmission lines. The reason why line protection is simpler than generator and transformer protection is that the parameters and calculation principles that need to be observed are relatively simple.

Suppose that the three points a, b, and c are equipped with switches and relay protection, and there is a transmission line between them. At this time, due to various reasons, a grounding fault occurs somewhere. How to capture where this fault point is and then automatically cut off the relevant switch?

This is power transmission. So naturally we need to look at voltage and current. In order to be more scientific and simplified, we choose to only look at their ratio. That is, the voltage divided by current, that is, u/i. A value called impedance, z.

What a classic formula. A guy named Ohm first discovered this formula, so a simple formula r=u/i in middle school textbooks appeared, which is a very popular formula in the middle school textbook, which means that voltage divided by current can obtain a resistance. Then the main use of line protection is actually this formula. The impedance is actually the resistance. Line protection determines whether something bad happened to this line by continuously capturing the "resistance".

Once the "resistance" deviates from the standard value, the line protection can be confirmed that something happened to us, so we will issue a trip order, breaking one of me and protecting everyone.

Return to the three points a, b, and c, assuming that the accident point is between a and b, then since the three points are close, the protection devices of a, b, and c will catch this change. After calculation and analysis, the protection devices of a and b are determined to be an in-region fault, and at the same time, a tripping command is issued within a few tens of milliseconds; the protection devices of a point c are also calculating and analyzing. It judges that it is an out-region fault and does not belong to its own affairs, so it remains unmoved. In this way, the switches of a point a and b jump away, and point c will avoid disaster and continue to operate in a closed state.

There may be a place that is difficult to understand here. The lines between a and b are broken. Is it useful to have your point c closed?

It should be noted that the power grid is a network, with all connections and spider webs, with complex lines. The electricity from point a must be transported to point c, and not just one channel b. If the A line where the accident occurs is cut off, the power will continue to be transmitted from other lines, ensuring the safety and stability of the entire power grid.

Therefore, the core value is the line protection of impedance, and the principle is relatively simple. In the most basic situation, you only need to calculate this impedance and then judge whether it is an accident within the area based on the situation of this value.

Of course, this is only relative. In actual working conditions, a series of data such as frequency and direction must be captured, divided into hundreds of situations to calculate and consider them separately, and finally calculate the most scientific action effect.

This is what the software system needs to do, and the hope of getting rich for science and engineering men and programmers.

Now, the series of simplifications proposed by Chang Jiang are facing this software system. In the long-term development, microcomputer protection is becoming more and more high-end like an operating system. From win3.1 to win95, to xp and 7, more and more functions emerge. It is necessary to intelligently measure the distance of the accident, analyze the communication network and other protection interoperability, etc. Fictionally speaking, the solution given by Zhang Yifu may be win95, but now it is still the Dos era. You only need to make win3.1 to be a big brother. Not only do you have to go directly to win95, but it is also tiring for you to surpass yourself.

"These simplifications are OK, but if you can leave room for expansion, it is best to leave it behind." Zhang Yifu heard Chang Jiang's introduction and glanced at the new plan and said, "For example, the software part can be not done in network communication for the first time, but the port must be left to ensure that we can upgrade new functions through version updates."

"Well..." Chang Jiang frowned, "But in this way, in the physical ports and industrial design protected by microcomputer..."

"Leave space." Zhang Yifu nodded affirmatively, "The development of automation and communication is faster than we imagined."

"Okay, let's improve the design of this part." Chang Jiang sighed, not arguing about this matter for now, and turned to the bare metal not far away. Although he was unwilling to admit it, Zhang Yifu was correct most of the time, which was so correct that it was difficult to understand. "In recent debugging, we have tried to manually input various parameters and observe the action situation. The effect is amazing. I don't understand many of the algorithms and models you gave, but I just wrote them down. I thought I needed to constantly modify and rework when debugging, but I didn't expect that the stability was almost full. Occasionally there were problems, and it was all our programming mistakes and had nothing to do with the principle of the algorithm."

"Exceeding the award..." Zhang Yifu didn't know how to answer, so he must not ask the details of the algorithm, as he could not explain it even if he died.

"And, although these things now only achieve less than 30% of the design plan, Mr. Chen and I firmly believe that they are absolutely at the world-class level, and their breakthrough in algorithm principles is even more than many domestic universities." Chang Jiang stared at the bare metal, "We must protect the core, fully encrypt and avoid decompilation."

Xiang Xiaofei slapped her head: "Why do I feel like I have to spend money again..."

Compared with R&D funds, the money spent on data security is actually just a drop in the bucket, which is equivalent to the difference between the money spent on buying a condom and the hotel bill.

"These are all later stories." Chen Yanrui felt that he was a little exhausted and reminded appropriately, "Let's start the experiment first. This experiment will take at least a few weeks. Press the switch first and then discuss the details."

"Yeah." Zhang Yifu expressed his affirmation.

"Everything is done, Mr. Chen." Chang Jiang also nodded at Chen Yanrui.

Chen Yanrui raised his hand and touched the button of the test instrument, but he did not press it. He knew that the meaning of this behavior was not just pressing a button, but also had a very important ritual.

"Yifu, come on." Chen Yanrui hesitated.

"No, come, come."

"I think this is the case, let's come together." Chang Jiang smiled, "Come on, let's put a few hands on the back of Mr. Chen's hand together."

After saying that, he was the first to go over.

Is Chang Jiang quite good at doing it?

Zhang Yifu thought so and took it on.

Then there is Xiang Xiaofei.

Chen Yanrui has lived for so long and has never experienced this feeling. The three young hands, hands with different temperatures, were intertwined with him, the old guy. The pulsation of blood was transmitted through the skin, and along Chen Yanrui's already hardened blood vessels, it reached the somewhat tired heart.

Dongdong... Dongdong...

The heartbeats of the four people were intertwined and merged.

Chen Yanrui felt, listened, and witnessed it personally. He suppressed his excitement and expectation, and with a little fear, he finally pressed the button.

Digital simulation has officially begun!

At the same time, domestically produced independent research and development of microcomputer protection, half of the leg has stepped into the threshold!

This should have been an exciting moment like Apollo's moon landing, but at the test site, there was no physical substantive performance, only the sound of the fan.

Everyone gradually let go, staring at the data on the electronic screen of the test instrument.

Not to mention Xiang Xiaofei, Zhang Yifu couldn't understand it.

Chang Jiang stared at everyone and explained to everyone: "This simulation environment has been set up by Mr. Chen before. For the convenience of testing, the accident frequency is set to 'high incidence' and the time parameters are also set to 'extremely fast'. At about 10 minutes here, it is roughly equivalent to the change of a high incidence transmission line for an accident in half a year."

"That's right." Zhang Yifu smiled, "Time synchronization, accident rate synchronization, and pure simulation, if we stayed on the computer for half a year, there would not be any abnormal data movement."

"Well, according to the instructions in this setting, there are about 5-10 sensitive data changes in one hour, of which 70% are non-accidents, or disturbances caused by other line accidents, and only 30% are accidents in this line that require the output of tripping signals." Chang Jiang stared at the screen seriously, "We must ensure that the 70% of the situation does not send tripping signals. If the calculation and judgment are wrong, it is a false move. At the same time, we must also ensure that the 30% jumps when it should jump, and if it does not jump, it is a refusal. Then integrate these data, calculate the false and refusal rate, and obtain the 'reliability'."

"After all, everything we do is for reliability, and of course there is also speed, selectivity, and sensitivity." Chen Yanrui became nervous after being slightly excited, "only these four characteristics meet the standards can follow-up tests and trial runs be carried out."
Chapter completed!