SERVICING OF HYDROGENERATORS
One of the basic tasks of hydrogenerator servicing is to provide safety in operation. The experience in servicing has shown that observing daily, monthly and yearly reports only, is not sufficient. Special significance has been given to surveying and timely checking of the actual condition of main parts of the generator. Main parts of the generator are under mechanical and thermal stresses, whereas the insulation of windings is under electrical field stress.
Water power was one of the first energies used and a great part of generators requires refurbishment or updating. The main philosophy guiding MG SERVIS activities is to control the condition of the generator and find best technical solution providing safety in operation.
MG SERVIS activities fall in four groups:
A >ANNUAL MAINTENANCE
Annual maintenance can be performed every 1 to 2 years depending on working hours and working condition
The annual maintenance entails:
- checking the operating data
- checking the stator end witning
- checking the winding leads and terminal
- checking the coolers and cooling system
- checking the brake ring, brake and braking system
- checking the slip ring
- checking the fans
- electrical test on windings
This type of activties require dismantling of the part of upper and lower cover.
B >GENERAL MAINTENANCE
When to do general maintenance? When to do the general maintenance can be calculated by means the results of annual maintenance, working condition and working hours, as follows:
t = ttr + 10Ns (h)
where
t = calculated working hours
ttr = actual working hours
Ns = number of starting
The experience has shown that the first general maintenance should be after 20 000 calculated working hours. The next general maintenance follows after 80 000 calculated working hours.
The visual control, control of dimension, control of centre line, electrical and mechanical tests make the basis of diagnostic assessment of the condition of generator main parts.
With general maintenance, the following parts are checked up:
- stator frame
- stator magnetic core
- stator winding
- rotor winding
- rotor shaft and rim
- upper and lower brackets
- guide and thrust bearings
- fans and brake ring
- brakes
- coolers and cooling system
- slip rings and brushes
- electric and mechanical test
Depending on the above check-ups and reports on annual maintenance, decision can be brought as to what should be done on the generator.
This type of maintenance requires dismantling of the complete generator, disalignment of turbine shaft and taking out of rotor.
C >REFURBISHMENT
Long period in operation and new technology of hydrogenerators has made us aware that change of main parts on an old generator is more economical.
HIGH AVAILABILITY AND HIGH EFFICIENCY MEAN ECONOMY TO-DAY MORE THAN EVER BEFORE.
In cooperation with world known companies we can refurbish your generators, providing:
- project (electrical and mechanical)
- drawings
- fabrication of parts
- removing of old parts and installing the new ones
- electrical and mechanical tests
- put in operation
D >MONITORING
The standard equipment required for generator operation consists of measuring and protection devices. The listed equipment ensures operation of generator
as physical unit within electricity generation. Equipment required to detect the condition of generator and its wear and tear used not to be a part of standard equipment. Recently special equipment has been installed in the unit to monitor the generator wear and tear. Generators with fenol and epoxy based insulation have been monitored through specific annual electric tests. In cooperation with world known companies, we can make project and install the following monitoring:
- vibration monitoring
- temperature monitoring
- PD measurement
- ozone measurement
- air gap monitoring
