Document rBZy7vOGb4DJnK5rNqwYwBzv7

Three Degrees of Generator Maintenance In Ardnscruiha Station Monthly Check Attsool Overhool Major Overhaul--Ivery.4-7 Years raSwj* Cteoacd; polarity reversed ii reetfisd Cleaned; turaed down if re quired Turned down, or replaced if required PSKlar , CUeasd; worn brushes # placed Cleaned and edjested; worn brashes replaced Cleoeed oed adjusted; worn brushes re placed m Tested with megohrnmeter Cteaeed where possible, but not removed. Tested with megohmmeter Removed sod cleaned. Pel* belts tested lei permanent eat oed far tightness. Pol* wind ings reclomped if protruding mice shews leesenrst between turns Net attended to Cleaned where possible. Tested with 01*90)1 ameter. Both Usdlegs end wedges Inspected Ait passages cleorsd. Loose bindings mode good; and connections varnished. Checked for cod deformation or displacement, te> wedge slip. lomlnoltens' condition atom ised a far os possible. Cere bolts tightened if aocoxMry. it* MAJOR OVERHAUL for eoeh mochlne comes or>co every 4-7 yeort- Unit It completely disosiembled end oil worn port* renewed. Generator l< dried out oiler reossembly Electrical Test Program Holds Down Hydro-Plant Outages With reserve capacity in Ireland's Ardnacrusha Hydro Station cut to bore minimum during last war, maintenance assumed major importance. Here:is the electrical side of their successful maintenance plan covering .115,000 )<vo of generating capacity - :i. By 9 BtftNf, fngineer, ArdneowtSo Hrdee Station, Intend Tut Siiakku* Itivtn winds 230 mites in South Ireland befsi ing into the sea. During it* 1 flows through three lakes and bti (all of 300 h. Ardnsetoshi Station, powered hy the Sh/` equipped with four generator* combined rating of 115,000 kv*section of the plant went lnto? in 1929. Dy 1939 when World started, mach of the equipmw* some major maintenance. Largest job to date has complete rebuilding f three stators. A serious increase in ing over the years made this n Before the war, equipment msi ers offered-odvice plus use o! ries and work shops on fWjr'. nance Jobs. In fact, they the entire work on most ol U" in|> dealing with penerntiPel,u 0 HC'wyMlMlJ AND maMaQ(m(nI SCCI'On Sthe war changed this picture, embryonic stage. And (he results were rr'penonnel were thrown on their good. Yardstick was..the comparative "f major repairs. And further' freedom from serious power interrup j were presented. For instance, tions over the past years, even in tbe gUteserve capacity was reduced ' (ace of an increased number of faults. jfftl'nn of about 20,000 kw to esactv- These faults varied from a low of IS ITttrt st certain limes of the day. in 1944 to a peak of 61 In 1949. Poten gpirn allowable time for mainte- tial trouble sources, even though de Was generally channeled into pe* tected before failure occurred, are listed ^tlslde normal working hours: here as faults. Typical faults were light tjagr and early roornlogs. ffjaknenca Ob|etivas. Before lookg^.the specific plan used at Ard- ning damage to station bus, punctured transformer bushing, failure of 110-kv insulators, water (5 gal) in tank of 8P let us consider maintenance 110-kv ocb, relay defects spotted during jyaL. Normally, maintenance is a overhaul. preserving plant and structure Maintenance Plan. Extended main Ijtfat working condition. But with tenance could be carried out only dur reserve generating cs- ing period from April to September, aims took on a slightly when water inflow normally dropped. I" brief, quality of main* And even during ibis season only one of '25'hsd to be upped to the point J|apent faults were located by ttpV ,e*1' ^ hrge proportion the four, units could be taken out of service.' Other 4imes available for work, without wasting water or losing load, fiS ,!* faults just had to be were weekends or early morning hours. SpuMrste, let's consider e single So to meet this double need--maximum ovailabilily and maximum reliability-- JLr- U is equipped with protective the following maintenance plan was jgjW'o Prevent or limit fault dam- evolved (or the four main generating ittJU.eveQ though these protective units. lu #na *^e'r function the Monthly check* consisting' of a me jrrenporerily short-handed, co- chanical end electrical once-over, take the unit being tripped between 6 and 8 hr. In addition each if** r prevent this we mode unit receives an annual general over i ort to detect faults in their haul. This includes i detailed inspection (or wear, thorough cleaning o( exciter, puri6cation of lubricating and servo motor oils, cleaning ol generator stator, plus a genera) electrical eheckup. It does not include generol disassembly of part*. This overhaul takes about' 14 days. Major overhaul for each machine comes once every 4 to 7 years. Unit it completely disassembled and all worn parts renewed. Alter reassembly the generotor is dried out. This work takes 3 to 4 months. Electrical Tests. At one time, instru ments end protective relays were taken down and sent to a central point for bench testing while the machine was being overhauled. But we ran into some' difficulties. For Instance, delicate relays and instruments, haring been tested in the control lab, were occasionally dam aged during transportation or reinstsllation. And since they received oo further check the damage sometimes passed uonoticed till the relay sms called on to operate. Furthermore, taking relays down and reinstalling sfter testing opened op possibility of mistakes in reconnecting. Relsys that are gravity controlled may be tested In one position and Installed In another, affecting operation. These problems were neatly aidestepped by testing sit relsys In position (NOINMIINO AND MANAOlMtMT SKTtON