Abstract]
[Keywords:]
With the rapid development of China's national economy, high-grade intelligent buildings have become the mainstream of today's architecture. This paper talks about the application of electrical automation in intelligent buildings.
Electrical automation intelligent building grounding
I. TN-S system
Second, TN-C-S system.
Third, exchange work basis.
Fourth, safety protection grounding
Five, shielding grounding and anti-static grounding
Six, DC grounding
Seven, lightning protection and grounding
Eight. Concluding remarks
TN-S system connects neutral line N and protective grounding line.
PE is a strictly isolated low-voltage distribution system, which is three-phase four.
The grounding system adopts wires and PE wires. Neutral line n and protective grounding line
PE is grounded at the neutral point of the transformer, and the two wires are no longer connected.
There are any electrical connections. When the system is running normally, it is neutral.
N line is charged and PE line is not charged. The grounding system is equipped with safety devices.
Completely reliable reference potential, PE line is not allowed to break, to ground.
There is no voltage, so the metal shell of the equipment is connected to the PE line.
Complete and reliable. Therefore, TN-S system can be used as an intelligent building.
The electrical wiring system is based on. In intelligent buildings, single-phase power is used.
There are many equipments, the proportion of single-phase load is large, and three-phase load is common.
It is often unbalanced, so there is random electricity on the neutral line n.
Flow. In addition, due to a large number of fluorescent lamps, it
The generated third harmonic is superimposed on the N line, adding N lines.
The magnitude of the current, if the N line is connected to the equipment shell, will make
Electric shock or fire accident; If TN-S system
N-wire and PE-wire are connected together, then connected to the equipment shell, and then
The danger is even greater. All the equipment and casings connected to the PE line are
Charged; Will increase the scope of electric shock accidents; If the n line,
PE line and DC ground line are connected together, except that the above situation will happen.
In addition to the danger, electronic equipment will also be disturbed and unable to work.
Work. Therefore, intelligent buildings should be equipped with DC connections for electronic equipment.
Grounding, AC working grounding, safety protection grounding and public buildings.
Buildings should also be grounded by lightning protection. Besides, because of wisdom,
There are many program-controlled switches with anti-static requirements in the building.
Computer room, computer room, fire control and fire alarm monitoring room
And a large number of precision electronic instruments susceptible to electromagnetic interference.
Equipment, so in the design and construction of intelligent buildings, it should also be
Consider the requirements of anti-static grounding and shielding grounding.
TN-C-S system consists of two grounding systems. The first one
One part is TN-C system, and the second part is TN-S system.
The interface is at the connection point of N line and PE line. The first system
Generally used for building power supply, attracted by regional substations.
TN-C system should be adopted before entering the house, and repeated entry should be made.
Grounding, it becomes TN-S system after entering the room. TN-S grounding system
The system obviously improves the safety of people and things. At the same time, as long as I
We use grounding leads, and each lead leads from the grounding body.
Out, and choose the right grounding resistance value to make electronic equipment * * *
By obtaining the equipotential reference point and other measures, TN-
C-S system can be used as a grounding method for intelligent buildings.
System.
Working grounding mainly refers to the neutral point or neutral point of transformer.
The sex line (N line) is grounded. N-wire must be insulated with copper core.
There are auxiliary equipotential terminals in power distribution, which
Terminals are usually in the cabinet. It must be pointed out that this connection
Wire terminals shall not be exposed; Can't with other grounding system, such as
DC grounding, shielding grounding, anti-static grounding and other mixed connections;
You can't connect the PE line either. In high pressure system, medium is used.
Neutral grounding mode can make grounding relay protection act accurately.
Eliminate single-phase arc grounding overvoltage. Neutral grounding may
Prevent zero-sequence voltage deviation and keep the three-phase voltage basically flat.
For low-pressure systems, balance is very meaningful.
Use single-phase power supply.
Safety protection grounding means that electrical equipment is not charged.
Make a metal connection between the metal part and the grounding body.
Electrical equipment in the building and some places near the equipment.
Metal components, connected with PE wire, but it is forbidden to use PE wire.
Connect with n lines.
In modern buildings, it is required to protect the grounding device safely.
There are many devices, including high-voltage devices, weak-current devices and one
Some uncharged conductive equipment and components must be safe.
Protective grounding measures. Safety protection and grounding are carried out when there is no electricity.
When the insulation of gas equipment is damaged, its shell may be charged.
If the human body touches the shell of this electrical equipment, it may be charged.
Injury or life-threatening. We know: in the merger,
In a circuit, the current value and resistance flowing through each branch.
The size is inversely proportional, that is, the smaller the grounding resistance, the greater the flow through the human body.
The smaller the current, the greater the human body resistance than the grounding resistance.
Hundreds of times, the current flowing through the human body is more than that flowing through the grounding body.
The current is one hundred times that of the decimal system. When the grounding resistance is extremely small, it flows through people.
The current in the body is almost equal to zero. In fact, due to grounding electricity
The resistance is very small, and the voltage drop caused by the grounding short-circuit current flowing through it.
Very small, so the voltage of the equipment shell to the ground is not high.
Yes When people stand on the ground and touch the device shell, people
The voltage borne by the body is very low and there is no danger. Additional protection
Protecting the grounding device and reducing its grounding resistance not only
To ensure the safe and effective operation of intelligent building electrical system are
Effective measures should also protect equipment and people in non-intelligent buildings.
Necessary security measures.
In modern buildings, shielding and its correct grounding are preventive measures.
The best protection method to prevent electromagnetic interference. The device housing may be
Connect with PE line; Shielded grounding of conductors requires shielded pipes.
Both ends are reliably connected with PE line; Indoor shielding should also be more coordinated.
PE line connection is reliable. Anti-static interference is also very important. Zaijie
In a clean and dry room, people walk, move equipment,
Every friction will produce a lot of static electricity. For example, under relatively humid conditions.
In the environment of 10 ~ 20%, people can accumulate 35000 when they walk.
Volt electrostatic voltage, if there is no good grounding, not only
It will only cause interference to electronic equipment, and even put the equipment
The chip is broken. Objects with static electricity may generate static electricity.
Objects (non-insulators) are connected to the grounding structure through electrostatic conductors.
The grounding of the circuit is called anti-static grounding. Anti-static connection
Requirements in a clean and dry environment, all equipment shell and
Indoor facilities (including floors) must be connected by PE line.
Through the connection. The grounding resistance of intelligent building grounding device is high.
The smaller the better, the independent lightning protection grounding resistance should be ≤ 10.
Ω; The grounding resistance of independent safety protection shall be ≤ 4Ω; independence
The AC working grounding resistance of should be ≤ 4ω; Independent DC worker
Grounding resistance should be ≤ 4Ω; Anti-static grounding resistance is generally required.
Find ≤ 100ω.
In intelligent buildings, there are many meters.
Computer, communication equipment and building automation equipment with computer
Get ready. In these electronic devices, information input, transmission
Information, converted energy, amplified signals, logical actions and inputs.
A series of processes such as information are all through micropotential or micropotential.
The current flows quickly, and devices often have to go through the Internet.
Work network. Therefore, in order to make it accurate and stable.
Good performance, in addition to the need for a stable power supply, but also
There must be a stable reference potential. You can use a bigger one.
The insulated copper core wire with cross section is used as the lead, and one end is directly connected with the base.
Quasi-potential connection, and the other end is DC grounding of electronic equipment.
Lead wires should not be connected with PE wires, and it is forbidden to connect with N wires.
There are a large number of electronic devices and circuits in intelligent buildings.
Communication automation system, fire alarm and fire control system.
Linkage control system, building automation system, security monitoring
System, office automation system, closed-circuit television system and
Their corresponding wiring systems. These electronic devices and circuits
The system generally meets the requirements of low withstand voltage and anti-interference.
The part of the height most afraid of being struck by lightning. Whether it's a direct hit or a string hit
Both strike and counterattack will cause different degrees of damage to electronic equipment.
Bad or serious interference. Therefore, all the work of intelligent building.
Grounding, must be based on lightning protection grounding system, and built.
Establish a strict and complete lightning protection structure.
Most intelligent buildings belong to the first-class load and should be protected by the first-class prevention.
The protective measures of mine buildings are designed, and the lightning arrester adopts needle belt.
The combined lightning arrester and lightning protection belt are made of 25×4(mm) galvanized flat steel.
The steel on the roof forms a grid of ≤ 10× 10(m), which is similar to a grid.
The metal components of the roof are electrically connected with the steel bars at the top of the column of the building.
For electrical connection, the down conductor shall be made of steel bars and ring beams at the top of the column.
Reinforcement and floor reinforcement are connected with lightning protection system, and the external wall is
Metal components should also be connected to the lightning protection system and reinforced at the top of the column.
Connect with the grounding body to form a cage defense with multi-layer shielding.
Thunder system. This can not only effectively prevent lightning damage to buildings
Internal equipment, but also to prevent external electromagnetic interference.
The application of electrical automation in intelligent buildings is still in its infancy in China.
It is a new technical field with more intelligent buildings.
With the emergence of, there will be more advanced technology to supplement this kind of collar.
Field, make this technology more mature and perfect.