What is the relationship between the phase wire and the shell of the three phase four wire generator

Three-phase four-wire diesel generator, measured in the case of all the taps removed, each tap and the shell is not connected (its insulation resistance is infinite), indicating that the insulation of the three-phase power coil and the shell is good, but according to the star connection, the insulation resistance of the generator phase wire and the neutral line and the shell are 192 ohm, indicating that the neutral wire (zero line) is not well grounded, please connect the neutral wire (zero line) of the generator with the neutral line of the mains and the shell of the generator in parallel, and must be firm and reliable, Otherwise, the line voltage will be normal and the phase voltage will be abnormal. The simplest solution is to use a thicker (diameter 8-12) multi-strand copper wire to connect in parallel with the mains power distribution panel (zero lint) and the neutral wire (zero line) of the generator and the generator shell (including the grounding wire point of the generator distribution panel) respectively. I have encountered such a phenomenon in actual work, the line voltage (400V) and phase voltage (230V) when using the mains are normal, as long as the switch to the self-provided diesel generator set will have a problem, the speed of the diesel generator set running (1500 rpm), frequency (50Hz), line voltage (400V), three-phase electrical equipment all work normally, but the phase voltage (230V) electrical equipment can not work normally, the actual phase voltage measured is only 160V, Even the fluorescent lamp could not be started to light, and finally the cause was investigated, and the result was that the copper grate of the neutral wire (zero wire) of the generator and the indirect line point of the aluminum wire had been oxidized, resulting in the poor grounding of the neutral wire (zero wire) and the abnormal phase voltage.

After your problem is solved according to the above methods, you can start the generator to generate electricity.

The generator is a three-phase four-wire (three fires and one zero), and the distribution cabinet is a three-phase five-wire (three fires and one zero), and after the fire is zero to zero, the ground wire of the distribution cabinet is directly grounded.

If the distribution cabinet and the generator are very close, the distribution cabinet and the generator should share the same wire, that is, the generator shell, the distribution cabinet shell, the generator zero line (neutral line) are connected together, the ground wire of the distribution cabinet is taken on the zero line, and the metal shell of the distribution cabinet is the same, and there is no need to take the generator anywhere.

If the distribution cabinet is far away from the generator, the distribution cabinet must be made of a grounding body that meets the regulations, and the ground wire of the distribution cabinet and the metal shell of the distribution cabinet are connected together.

The 380V 220V low-voltage power distribution system can be divided into IT system, TT system and TN system according to the different forms of protective grounding.

The neutral point of the power supply of the IT system is insulated from the ground or grounded with high impedance, while the metal casing of the electrical equipment is directly grounded. That is, in the past, it was called the protective grounding of the three-phase three-wire power supply system.

The neutral point of the power supply of the TT system is directly grounded; The metal casing of the electrical equipment is also directly grounded and has nothing to do with the grounding of the neutral point of the power supply. That is, the protective grounding in the three-phase four-wire power supply system in the past.

TN system, in the 380 220V three-phase four-wire low-voltage power grid where the neutral point of the transformer or generator is directly grounded, the metal shell of the electrical equipment that is not charged during normal operation is directly electrically connected to the neutral point of the power supply through the common protection line. That is, the protection zero connection in the past three-phase four-wire power supply system.

The neutral point of the power supply of the TN system is directly connected to ground, and there is a neutral lead out. According to the form of its protection line, the TN system is divided into three types: TN-C system, TN-S system and TN-C-S system.

1) TN-C system (three-phase four-wire system), the neutral wire (N) and the protection wire (PE) of the system are integrated, and the line is also called the protection neutral wire (PEN) line. It has the advantage of saving one wire, and the disadvantage is that the three-phase load unbalanced or when the protective neutral wire is disconnected, the metal casing of all electrical equipment carries a dangerous voltage.

2) TN-S system is a three-phase five-wire system, the N line and PE line of the system are separated, and the five-wire power supply is used from the transformer. It has the advantage that there is no current passing through the PE line under normal conditions, so there is no electromagnetic interference to other devices connected to the PE line. In addition, since the N-line is separated from the PE line, the disconnection of the N-line will not affect the protection of the PE line.

TN-C-S system (three-phase four-wire and three-phase five-wire hybrid system), the system is from the transformer to the user's distribution box type four-wire system, the neutral wire and the protective ground wire are integrated; From the distribution box to the user's neutral wire and protective ground wire is separated, so it has the characteristics of both TN-C system and TN-S system, and is often used in places with poor environment at the end of the distribution system or strict requirements for electromagnetic anti-interference.

Measure whether the neutral (neutral) insulator has leakage from the shell. If there is, it can't be started.

The three-phase four-wire is:

The 10 thousand volt high-voltage input from the substation is used to step down the voltage to the transformer to 380V voltage, divided into yellow, green and red three lines, and then there is a neutral wire from the transformer, which is called the zero line, and the composition of the four lines is a three-phase four-wire system, which is given to factories, schools, hospitals, and civil use.

The relationship between the four lines is:

The composition of any two wires in the three-phase is 380V, which is called the line voltage. Any phase and neutral line composition is called phase voltage, which is the three-phase four-wire system.

When the three-phase alternator supplies power to the outside, the ends of the three groups of coils X, Y, and Z are connected together, and a line is drawn from the connection point, which is called the neutral line, also called the neutral wire. Then from the other end of the coil winding A, B, C each lead out a line, these three lines are called phase wire or live wire, this connection method is called star connection method.

This outward transmission method of the generator constitutes a three-phase four-wire system. If the middle line is not drawn, the power supply to the outside with three wires is called a three-phase three-wire system.

Because the three-phase four-wire power supply can supply two different voltages of 220V and 380V at the same time, it is widely used. The star connection is represented by y, which is also called the y connection.

At present, most of the three-phase four-wire low-voltage power supply system in China is adopted, that is, the 380V 220V neutral point direct grounding low-voltage power supply system, which has three phase wires (live wires) A, B, C, and one neutral line. The reason why this zero line is called the zero line is because it is drawn from the neutral point on the secondary side of the transformer, and the neutral point on the secondary side is directly connected to the ground with the zero potential of the earth, so it is called the zero line. In the three-phase four-wire system low-voltage power supply system, it is both the working zero line and the protection zero line, now called the PEN line, in which PE is the protection zero line, N is the working zero line, together it is the PEN line, and the PEN line represents the working zero line and the protection zero line, commonly known as "zero ground integration".

The wiring method of the three-phase four-wire meter is very worthy of collection when the beginner electrician sees it.

What is the difference between three-phase four-wire three-phase four-pole, the old electrician tells you.

Alternating current has a phase angle, every two phases of electricity in the three-phase electricity are 120 degrees different, two phases of 120 degrees difference of the value of 220 phasors, the sum of their phasors is exactly 380 degrees, with the parallelogram rule, you can calculate it yourself.

Let a certain line be u1=u0*cos t, and another u2=u0*cos( t+4 3), u2-u1 = root number 3*u0*cos( t- 6), the amplitude is 3 times the root number of u0, and the average value is naturally 3 times the root number, note that 220v is not u0 but the average value. 220 root number 3 times

Draw a regular triangle abc, take the intersection point of the middle line as the zero point o, let the phase voltage oa=ob=oc=220, then the line voltage ab=bc=ac=3

It's what we generally call 380 volts.

In the alternator, the three sets of coils are placed at an angle of 120 degrees to each other, and the sequence of the inductance line through the neutral plane is different, and the phase of the alternating current generated is 120 degrees different. The effective values of the voltages to ground are all 220V, due to the phase difference of 120. The effective voltage between the two phase wires is 380V, as for the calculation, you can refer to the upstairs.

1. Three-phase four-wire system: phase line A, B, C, protection zero line PEN, there is a working current on the PEN line, and the PEN should be repeatedly grounded when entering the electricity building, which belongs to the TN-C grounding system.

Three-phase five-wire system: phase line A, B, C, neutral line N, protective grounding wire PE, N line has working current through, PE line usually has no current (only in the event of leakage or short circuit to the ground, there is fault current); The power distribution mode of civil buildings in China adopts TN-S grounding system.

2. The three-phase four-wire system is three live wires that export three sine wave voltages with a difference of 120 degrees, plus a neutral point to draw the zero line. Residential electricity is taken from a line of fire and flows back to the generator from the zero line. The three sine waves at the neutral point cancel each other out, and the voltage is 0, so it is called the zero line (n).

The three-phase five-wire system is based on the three-phase four-wire system and adds an additional grounding ground wire (PE), which is connected to the metal surface of the electrical appliance and uses the zero potential of the earth to guide away the leaked electricity.

3. If you are an ordinary user, your home appliance water heater is to be powered by 3-phase 5-wire. Because the ground wire is connected to the shell for protection. If there is no ground wire, it will leak current.

The difference between the three-phase four-wire system and the copy three-phase five-wire system is that the BAI three-phase four-wire system has one less ground wire than the three-phase five-wire zhi system.

The three-phase four-wire system is DAO three phase wires + one neutral wire, and the three-phase five-wire system is three phase wires + one neutral wire + one ground wire.

A three-phase circuit powered by a three-phase AC power supply. Abbreviated as three-phase circuit. Three-phase AC power supply refers to a power supply that can provide 3 voltages or currents with the same frequency but different phases, the most commonly used is a three-phase alternator.

The phase difference of each phase voltage of a three-phase generator is 120°. The order in which the voltage of each phase between them is ahead or lags behind is called the phase sequence. The three-phase motor rotates forward when the positive sequence voltage is supplied, and reverses when it is changed to a negative sequence voltage power supply.

Therefore, it is important to pay attention to the phase sequence when using a three-phase power supply. Some production equipment that requires forward and reverse rotation can control the forward and reverse rotation of three-phase motors by changing the power supply phase sequence. A three-phase circuit is a special type of AC circuit that consists of a three-phase power supply, a three-phase load, and a three-phase transmission line.

Most of the power supply modes in the world's power system use three-phase system.

The difference between three-phase four-wire and three-phase five-wire, three-phase five-wire is one more ground wire.

Today, I learned that there are three forms of three-phase electricity, and many electricians are confused and never understand.

The difference between three-phase four-wire and three-phase five-wire is that three-phase five-wire has one more ground wire.

Three-phase four-wire system: phase line A, B, C, protect the zero line PEN, there is a working current on the PEN line, and the PEN should be repeatedly grounded when entering the electricity building; It belongs to the TN-C grounding system.

In the TN-C system, the guard wire and the neutral wire are merged into the PEN line, which has the advantage of simplicity and economy. When a grounding fault occurs, the fault current is large, and the general overcurrent protection electrical appliance can be used to cut off the power supply to ensure safety.

However, for single-phase loads or three-phase unbalanced loads and lines with harmonic current loads, the normal pen line has current, and the voltage drop generated by it is presented on the metal shell of the electrical equipment and the metal sleeve of the line, which is not good for sensitive electronic equipment.

Three-phase five-wire system: phase line A, B, C, neutral line N, protective grounding wire PE, N line has working current through, PE line usually has no current; The power distribution mode of civil buildings in China adopts TN-S grounding system.

In the TN-S system, the protection wire is separated from the neutral wire (five wires are used for power supply from the transformer), which has the advantages of the TN-C system, but is more expensive. Because the PE wire does not pass the load current under normal circumstances, and the metal shell of the electrical equipment connected to the PE wire does not have potential, it is suitable for data processing and power supply of precision electronic equipment, and can also be used in dangerous environments.

The three-phase four-wire system is the TN-C system, which consists of three phases: L1---A) phase, L2---B) phase, L3 ---C).

Phase and a neutral line pen, is a working neutral line and protection neutral line set up in one zero protection system. pen line.

It is designed to obtain 220V line-to-line voltage from 380V phase-to-phase voltage, and can also be used in some cases.

Zero-sequence current detection is performed for monitoring the balance of the three-phase power supply.

The three-phase five-wire system is the TN-S system (including the TN-C-S system), which contains three phase wires L1---A) phase

L2---b) phase, L3---c) phase, a neutral wire n and a ground wire PE are the working zero and the protection zero.

A zero-connection protection system in which the lines are set separately or partially separately. The PE wire is connected to the N wire on the power supply transformer side.

together, but after entering the user's side, it can not be used as a neutral line.

Code for Design of Power Supply and Distribution System GB50052-95 Article:

The low-voltage distribution voltage should be 220 380V. The type of live conductor system should adopt single-phase two-wire system, two.

Phase three-wire, three-phase three-wire and three-phase four-wire.

The advantage of the three-phase five-wire system is that the protection sensitivity and reliability are higher than that of the three-phase four-wire system, because the PE line (i.e.

Ground neutral) is set separately and is connected directly from the neutral point of the power transformer, which has been.

Reliable direct grounding with low ground resistance to meet system protection requirements.

The three-phase five-wire system is usually used in places and residences with high safety requirements and uniform grounding requirements.