How does the generator excitation circuit insulation inspection device monitor the excitation circui

The generator excitation circuit inspection device is relatively simple, the machine is used in a common set, with the transfer switch 1ck, 2ck and voltmeter 1v to form a transfer switch 2ck to select the measured generator, voltmeter 1v transfer switch 1ck is used to measure the positive and negative poles of the generator to the large shaft (ground) insulation can also measure the excitation voltage of the generator. Normally, because the positive and negative electrodes of the excitation circuit are well insulated to the ground, the insulation resistance of the positive and negative electrodes and the large shaft is also infinite, and if the voltmeter is connected between the positive electrode and the shaft or between the negative electrode and the shaft, the voltmeter is not indicated because the loop cannot be constructed.

1) The stator current and active power of the generator decrease instantaneously and then rise rapidly, and the ratio increases, and begins to swing.

2) The generator can still generate a certain amount of active power after losing magnetism, and keep the direction of the active power sent unchanged, but the pointer of the power meter swings periodically.

3) When the stator current increases, the pointer of the ammeter also swings periodically.

4) From the reactive power sent to the absorbed reactive power, the pointer also swings periodically. The amount of reactive power absorbed is approximately proportional to the amount of reactive power before demagnetization.

5) The rotor circuit induces the alternating current and alternating magnetodynamic potential of the slip frequency, so the rotor voltmeter pointer also swings periodically.

6) The pointer of the rotameter also swings periodically, and the value of the current is smaller than that before the loss of magnetism.

7) When the rotor circuit is open, a certain eddy current is induced on the surface of the rotor body to form a rotating magnetic field, and a certain asynchronous power is also generated.

What are the hazards of generator excitation circuit ground failure? How should the treatment be checked.

The hazard of generator excitation circuit failure: when the generator is in normal operation, there is a certain rapid collapse of insulation resistance and distribution capacitance between the excitation circuit to the ground, their size is related to the structure of the generator rotor, cooling mode and other factors, when the rotor insulation is damaged, it may cause the excitation circuit grounding fault, the common is Yusen one point grounding fault, if not dealt with in time, there may be two points of grounding fault excitation circuit one point grounding fault, because the current loop can not be constructed, it will not constitute a direct hazard to the generator, The main concern is that the second point of grounding fault will occur in the mu imaginary circle, because after a point of grounding fault, the voltage of the excitation circuit to the ground will increase, and the second fault point may occur. The hazards of two-point grounding of the excitation circuit are as follows:

1) One part of the rotor winding is short-circuited, and the other part of the winding current increases, which destroys the symmetry of the generator's air gap magnetic field, causes the generator's violent vibration, and reduces the reactive power output at the same time. (2) The rotor current flows through the rotor body, and if the rotor current is relatively large, the rotor may be burned out, and sometimes the rotor and steam turbine blades and other components will be magnetized (3) Due to the partial current of the rotor body through the rotor, local heating is caused, which causes the rotor to slowly deform and form eccentricity, which further aggravates the vibration.

Summary. Hello dear, according to the situation you described The hazards of generator excitation circuit failure: when the generator is operating normally, there is a certain insulation resistance and distribution capacitance between the excitation circuit and the ground, their size is related to the structure of the generator rotor, cooling mode and other factors, when the rotor insulation is damaged, it may cause the excitation circuit grounding fault, the common is a point grounding fault, if not dealt with in time, a two-point grounding fault may occur The excitation circuit is a grounding fault, because the current circuit cannot be constructed, It will not pose a direct hazard to the generator, mainly because it is worried about the occurrence of a second ground fault, because after a ground fault, the voltage of the excitation circuit to the ground will increase, and a second fault point may occur.

The hazards of two-point grounding of the excitation circuit are as follows: (1) one part of the rotor winding is short-circuited, and the other part of the winding current increases, which destroys the symmetry of the air gap magnetic field of the generator, causes the violent vibration of the generator, and reduces the reactive power output at the same time. (2) The rotor current flows through the rotor body, and if the rotor current is relatively large, the rotor may be burned out, and sometimes the rotor and steam turbine blades and other components will be magnetized (3) Due to the partial current of the rotor body through the rotor, local heating is caused, which causes the rotor to slowly deform and form eccentricity, which further aggravates the vibration.

What are the hazards of generator excitation circuit ground failure? How should the treatment be checked.

Hello dear, according to the situation you described, the hazards of generator excitation circuit failure: when the generator is operating normally, there is a certain insulation resistance and distribution capacitance between the excitation circuit and the ground, and their size is related to the structure of the generator rotor, cooling mode and other factors, when the rotor insulation is damaged, it may cause the excitation circuit grounding fault, the common is a one-point grounding fault, if not dealt with in time, a two-point grounding fault may occur The excitation circuit is a one-point grounding fault, because the current loop cannot be constructed, It will not pose a direct hazard to the generator, mainly because it is worried about the occurrence of a second ground fault, because after a ground fault, the voltage of the excitation circuit to the ground will increase, and a second fault point may occur. The hazards of two-point grounding of the excitation circuit are as follows:

1) Part of the rotor winding is short-circuited, and the other part of the winding current type is increased, which destroys the symmetry of the generator's air gap magnetic field, causes the generator's violent vibration, and reduces the reactive power output at the same time. (2) The rotor current flows through the rotor body, and if the rotor current is relatively large, the rotor may be burned out, and sometimes the rotor and steam turbine blades and other components will be magnetized (3) Due to the partial current of the rotor body through the rotor, local heating is caused, which causes the rotor to slowly deform and form eccentricity, which further aggravates the vibration.

1.Check whether the excitation circuit is ignited and worked, and correct it if it is caused by the staff. 2.

Check the excitation circuit, whether there is obvious damage or dirt in each part, and purge if the grounding is caused by dirt. 3.Check whether the grounding point is in the rotor circuit (measurement protection circuit) or in the excitation circuit.

(1) Rectifier output fault and handling of exciter.

The excitation mode of a power plant is brushless excitation type (the system wiring method is as follows), after the excitation current is given when the voltage is boosted, the generator voltage changes little, and the results of many experiments are the same, the three-phase voltage regulator is directly added to the excitation power circuit for rectification, and the generator voltage is still only 30% when the output is to the rated currentThe output current of the excitation device is normal, and the generator voltage still cannot rise after reaching the rated current, and the excitation fault can be basically eliminated. After inspection, it was found that the output of the rectifier part of the exciter was abnormal, and the rectifier diode was faulty, and the boost was normal after the solution.

2) Excitation PT voltage fault and treatment.

A power plant is a thyristor self-excitation magnetic system, after the generator reaches the rated speed, the operator operates the "start-up" switch on the excitation adjustment cabinet, after the generator starts up, the generator voltmeter pointer does not move, and the excitation transformer secondary side voltmeter is soon full, and then the protection action, the degaussing switch jumps away, and the inspection finds that the two contacts of the degaussing switch are burned, and the -C phase thyristor radiator directly above the degaussing switch is seriously blackened, and the continuous inspection finds that the excitation transformer high-voltage insurance (10A) three-phase is too late to fuse, The main body was blown away, and the high-voltage safe was verified and blackened.

After inspection, the main reason for the accident was that the PT voltage was not put in, and the voltage was turned on in an "automatic" way. Since the automatic excitation regulator uses PT voltage as the feedback quantity, no feedback voltage is detected, and the control angle is kept at a minimum angle. The excitation current will continue to rise, the generator voltage will rise to the saturation point, at this time the excitation current continues to increase, due to the large increase rate of current, the voltage will reach more than double, the current and voltage of the high-voltage fuse of the excitation transformer exceed the rated value, the high-voltage fuse is too late to fuse, the energy when the fuse is very large, exceeds the limit of internal absorption of the fuse, and is blown off.

After the insurance is blown up, the three phases arc each other to cause a three-phase short circuit of the generator, and finally the generator differential protection action jumps to open the demagnetization switch.

The alternator you said should be a synchronous generator, because the synchronous generator has the problem of excitation, the synchronous motor has a kind of protection called loss of magnetism protection, the function of this protection is that the synchronous motor excitation circuit can automatically detect the fault when the excitation circuit fails, and then protect the action to protect the motor and the system.

The principle is roughly that by measuring the impedance, after the failure of the excitation circuit of the synchronous motor, it will run out of step, and its impedance characteristics will become the characteristics of an induction motor, and the purpose of identification can be achieved by detecting the impedance characteristics.

The specific principle is not clear in one or two sentences.

You can consult the book on relay protection for power systems in the chapter on magnetism loss protection for synchronous motors.

1: The open circuit can be directly measured by the resistance file of the multimeter.

2: You can choose to use the voltage gear of the multimeter, so that the two meter pens are connected to the two ends of the excitation coil respectively, and touch the two poles of the dry battery, and observe whether the voltage indication becomes larger when the battery is disconnected. If it is directly smaller, it is faulty.

Does your generator have magnets on its own?

The short-circuit test of the generator is a test method to check whether the electrical parts such as the windings and wiring of the generator are normal. Before the short circuit test can be performed, the excitation method needs to be used to provide the generator with a normal electromagnetic field. Here are the steps for the excitation method:

1.Check if the generator is in non-working condition, turn off all load switches and disconnect the excitation system.

2.Connect the excitation winding of the generator to the power supply to ensure that the voltage is stable. According to the rated voltage of the generator, select an appropriate DC power supply.

3.Adjust the excitation current to reach the set current value. The current value is usually indicated on the generator's signage.

4.Measure excitation voltage and current. Ensure that the excitation current and voltage comply with the manufacturer's specifications and are stable within the set value.

5.Before switching to the short circuit test, it is necessary to disconnect the excitation power supply, turn off all switches, ensure that the backup power supply has been disconnected, and make the necessary grounding.

It should be noted that the generator short circuit test needs to be operated by a professional technician. Before the test is carried out in the mountain shed, it must be operated in strict accordance with the relevant regulations and operating procedures to ensure the validity and safety of the test.