Prevent phase-to-phase short circuit caused by loose ends of stator windings
The stator winding should be fastened in the slot, and the slot potential test should meet the requirements.
Regularly check whether the stator winding ends are sinking, loose or worn.
Prevent stator winding insulation damage
Strengthen the inspection of the ring wiring and transition lead insulation of large generators, and regularly conduct tests in accordance with the requirements of the “Protection Test Regulations for Power Equipment” (DL/T 596-1996).
Regularly check the tightness of the stator core screw of the generator. If the tightness of the core screw is found to be inconsistent with the factory design value, it should be dealt with in time. Regularly check that the generator silicon steel sheets are stacked neatly, there is no overheating trace, and the dovetail groove has no cracking and disengagement. If the silicon steel sheet slips out, it should be dealt with in time.
Prevent short circuit between turns of rotor winding.
The dynamic and static inter-turn short-circuit tests should be carried out respectively for the peak-shaving unit during maintenance, and the rotor winding dynamic inter-turn short-circuit online monitoring device can be installed if conditions permit, so as to detect abnormalities as early as possible.
Monitor the vibration and reactive power changes of generators in operation at any time. If the vibration is accompanied by reactive power changes, the generator rotor may have a severe inter-turn short circuit. At this time, the rotor current is firstly controlled. If the vibration suddenly increases, the generator should be stopped immediately.
To prevent local overheating damage to the generator
The generator outlet and the connection part of the neutral point lead should be reliable. During the operation of the unit, infrared imaging temperature measurement should be carried out regularly for the split-phase cable from the excitation to the static excitation device, the cable from the static excitation device to the rotor slip ring, and the rotor slip ring.
Regularly check the contact between the dynamic and static contacts of the electric brake knife brake, and find that the compression spring is loose or the single contact finger is not parallel to other contact fingers and other problems should be dealt with in time.
When the generator insulation overheats alarm, the reason should be analyzed, and if necessary, the machine should be shut down to eliminate the defect.
When the new machine is put into production and the old machine is overhauled, attention should be paid to check the compression of the stator iron core and whether the tooth pressure finger is biased, especially the teeth at both ends. run. The iron loss test should be carried out when handover or when there is doubt about the core insulation.
In the process of manufacturing, transportation, installation and maintenance, care should be taken to prevent small foreign objects such as welding slag or metal chips from falling into the ventilation slots of the stator core.
Prevent generator mechanical damage
When working in the generator wind tunnel, a special person must be assigned to guard the entrance of the generator. The operator must wear metal-free work clothes and work shoes. Before entering the generator, all prohibited items should be taken out, and the items brought in should be counted and recorded. When the work is completed and withdrawn, the inventory is correct to ensure that there are no leftovers. The key point is to prevent the metal debris such as screws, nuts, tools, etc. from being left inside the stator. In particular, a detailed inspection should be carried out on the gap between the end coils and the position between the upper and lower involutes.
The main and auxiliary equipment protection devices should be checked regularly and put into normal operation. When the important operation monitoring meters and devices of the unit fail or operate incorrectly, it is strictly forbidden to start the unit. When the unit is out of control during operation, it must be stopped.
Strengthen the adjustment of the operation mode of the unit, and try to avoid the high vibration area or cavitation area of the unit operation.
Prevent the generator bearing from burning tiles
The thrust bearing with the high-pressure oil jacking device should ensure that in the event of failure of the high-pressure oil jacking device, the thrust bearing is not put into the high-pressure oil jacking device to stop safely without damage. The high-pressure oil jacking device should be checked regularly to ensure that it is in normal working condition.
The oil level of lubricating oil should have remote automatic monitoring function and be checked regularly. The lubricating oil should be tested regularly, and the deterioration of the oil quality should be dealt with as soon as possible, and the unit should not be started if the oil quality is not qualified.
The cooling water temperature, oil temperature, tile temperature monitoring and protection devices should be accurate and reliable, and the operation accuracy should be strengthened.
When abnormal operating conditions of the unit may damage the bearing, it must be fully checked to confirm that the bearing bush is in good condition before restarting.
Regularly inspect the bearing pad to confirm that there are no defects such as shelling and cracks, and the surface finish of the bearing pad contact surface, shaft collar and mirror plate should meet the design requirements. For Babbitt bearing pads, the contact between the alloy and the pad should be checked regularly, and non-destructive testing should be carried out if necessary.
The bearing shaft current protection circuit should be put into normal operation, and the shaft current alarm must be checked and dealt with in time, and the unit is prohibited from running without shaft current protection for a long time.
Prevent the loosening of hydro-generator components
The connecting parts of rotating parts shall be prevented from loosening and shall be inspected regularly. The rotating fan should be installed firmly, and the blades should be free of cracks and deformation. The air-inducing plate should be installed firmly and keep a sufficient distance from the stator bar.
Stator (including frame), rotor parts, stator bar slot wedge, etc. should be checked regularly. The fixing bolts, stator foundation bolts, stator core bolts and tension bolts of the turbine generator frame should be well fastened. There should be no looseness, cracks, deformation and other phenomena.
In the wind tunnel of the hydro-generator, it is necessary to avoid the use of materials that are prone to heat under the electromagnetic field or metal connecting materials that can be electromagnetically adsorbed. Otherwise, reliable protective measures should be taken, and the strength should meet the requirements for use.
Regularly check the mechanical braking system of the hydro-generator. The brakes and brake rings should be flat without cracks, the fixing bolts should not be loose, the brake shoes should be replaced in time after they are worn, and the brakes and their air supply and oil systems should be free of hairpins. , string cavity, air leakage and oil leakage and other defects that affect the braking performance. The speed setting value of the brake circuit should be checked regularly, and it is strictly forbidden to use the mechanical brake at high speed.
Periodically check the synchronization device to prevent the hydro-generator from being connected to the grid asynchronously.
Protection against generator rotor winding ground faults
When the rotor winding of the generator is grounded at one point, the fault point and nature should be identified immediately. If it is a stable metal grounding, it should be stopped immediately.
Prevent generators from being connected to the grid asynchronously
The computer automatic quasi-synchronization device should be installed with an independent synchronization inspection.
For units newly put into production, overhauled and synchronizing circuits (including voltage AC circuit, control DC circuit, full-step meter, automatic quasi-synchronizing device and synchronizing handle, etc.) that have been modified or whose equipment has been replaced, the following work must be done before connecting to the grid for the first time : 1) Carry out a comprehensive and detailed check and transmission of the device and the synchronous circuit; 2) Use the generator-transformer set with no-load busbar boost test to check the correctness of the synchronous voltage secondary circuit, and check the whole step table. 3) Carry out the false synchronous test of the unit, and the test should include manual quasi-synchronization and automatic quasi-synchronization closing test of the circuit breaker, synchronous blocking and so on.
Prevent generator damage caused by excitation system failure
Strictly implement the dispatch center’s low-excitation limit and PSS setting requirements for generators, and verify them during overhaul.
The over-excitation limit and over-excitation protection settings of the automatic excitation regulator should be within the allowable values given by the manufacturer, and should be checked regularly.
When the automatic channel of the excitation regulator fails, the channel should be switched and put into operation in time. It is strictly forbidden for the generator to run for a long time under manual excitation regulation. During the operation of manual excitation regulation, when adjusting the active load of the generator, the reactive load of the generator must be properly adjusted to prevent the generator from losing its static stability.
When the power supply voltage deviation is +10%~-15% and the frequency deviation is +4%~-6%, the excitation control system, switches and other operating systems can work normally.
In the process of starting, stopping and other tests of the unit, measures to cut off the generator excitation at low speed of the unit should be taken.
Post time: Mar-01-2022
