Ulinzi wa Mzunguko wa Mchimbaji
Maana ya Upotoso wa Excitation
Upotoso wa excitation kwenye generator hutokea wakati mfumo wa excitation huanguka, chukiwa generator hujifanya kujifunza juu ya kiwango cha synchronous speed.
Mfano wa Generator wa Induction
Bila excitation, generator hupata kuwa induction generator, ambayo inaweza kusababisha matatizo ya moto na ongezeko la mwendo.
Ulinzi wa Relay wa Undercurrent
Relay wa undercurrent unaweza kulinzia dhidi ya upotoso wa field kwa kutumika wakati current ya excitation inapungua chini ya thamani fulani.
Relay hii hutumika ikiwa current ya excitation inapungua chini ya thamani iliyowekwa, mara nyingi ni asilimia 8% ya rated full load current. Ikiwa circuit ya field inabaki sahihi lakini exciter anafeli, induced current ya slip frequency inaweza kusababisha relay kupick up na drop off. Hili kinaweza kudhibiti kwa kubadilisha settings za relay.
Thamani ya asilimia 5% ya normal full load current inahitajika. Relay wa undercurrent una contact normally closed ambayo inabaki wazi wakati relay coil imeenergized na shunted excitation current. Wakati mfumo wa excitation hufeli, relay coil hude-energize, kufunga contact na kutumia nguvu kwa timing relay T1.
Wakati relay coil imeenergized, contact normally open ya relay T1 inafunga. Contact hii inafunga supply kwenye timing relay T2 kingine na pickup time delay yenye changamoto ya sekunde 2 hadi 10. Relay T1 ina time delay on drop off ili kukusanya scheme tena dhidi ya effect ya slip frequency. Relay T2 inafunga contacts zake baada ya muda uliohitaji ili kuingiza shutdown au kuanza alarm. Ina time delay on pickup ili kurudi kwa kutosha operation ya scheme wakati wa fault external.
Timing Relays kwa Stabilization
Tumia timing relays husaidia kustabilisha protection scheme dhidi ya effects za slip frequency na kuzuia false operations.
Tunajua kuwa umbo la system ni ishara kuu ya ustawi wa system. Kwa hiyo offset mho relay imewekwa kushinda machine instantaneously wakati operation ya generator inasambazwa na collapse ya system voltage. Drop katika system voltage inaridhika na under voltage relay ambayo imezetwa kwa asilimia 70% ya normal rated system voltage. Offset mho relay imewekwa kuanza load shedding hadi value salama na kisha kuanza master tripping relay baada ya muda uliohitaji.
Ulinzi Mrefu kwa Generators Kubwa
Kwa generators kubwa, schemes advanced na offset mho relays na under voltage relays zinatumika kudhibiti ustawi wa system kupitia load shedding na master tripping relays.
Mapendekezo
