THD Overload: Jinsi Mawasilisho Yanayoharibu Vifaa vya Umeme
Wakati THD halisi ya Mipango yakidhulumiwa (kama mfano, THDv ya Umeme > 5%, THDi ya Kengele > 10%), hii huachia athari kibora kwa vifaa vyote katika mzunguko wote wa Nishati — Kutumika → Kutambua → Kufuatilia → Kudhibiti → Kutumika. Mbinu muhimu ni zao la ziada, mwendo wa kengele wa juu, mabadiliko ya nguvu na kuburudisha mseto. Mbinu na ujumbe wa athari unabadilika sana kutegemea na aina ya vifaa, kama linavyoonyeshwa chini:
1. Vifaa vya Kutumika: Kupata Moto, Kuzeeka, na Muda wa Maisha kuongezeka
Vifaa vya kutumika vinatuma umeme/kengele wa grid moja kwa moja. Harmoniki zinazidi zao la ziada na kusafiri kwenye insulation. Vikundi muhimu vilivyopata athari ni mstari wa kutumika (kabele/mtaro) na transformers za kengele (CTs).
1.1 Mistari ya Kutumika (Kabele / Mistari ya Juu)
Mbinu ya Athari: Marefu ya harmoniki inayozidi hii huongeza "skin effect" (mara ya juu ya kengele yanayokokoteliwa kwenye usimamizi wa conductor, kuchelewesha eneo lenye umuhimu), kuzidi resistance ya mstari. Zao la copper za ziada zinazidi kwa mraba wa harmonic order (mfano, zao la copper ya 5th harmonic ni 25× zaidi ya asili).
Athari Zenye Uwezo:
Kupata Moto: Kwenye THDi = 10%, zao la copper zinazidi kwa 20%-30% kulingana na masharti yaliyotathmini. Hali ya moto ya kabele inaweza kusonga kutoka 70°C hadi 90°C (kutokana na ukubaliki wa insulation), kuchelewesha kuzeeka na kuganda kwa viungo vya insulation (mfano, XLPE).
Muda wa Maisha unaongezeka: Kupata moto kwa muda mrefu kungharibu muda wa maisha wa kabele kutoka 30 mwaka hadi 15–20 mwaka, kwa uwezo wa "insulation breakdown" na matatizo ya short-circuit. (Uwanja wa kiwango cha kimataifa kilipiga kabele mbili za 10kV ndani ya mwaka mmoja kutokana na 3rd harmonic, kutumia zaidi ya 800,000 RMB katika majaratibu ya sarafu.)
1.2 Transformers za Kengele (CTs)
Mbinu ya Athari: Kengele za harmonic (hasa 3rd na 5th) huchanganya "saturation ya fasi" ya cores za CT, kuzidi hysteresis na zao la eddy current (zao la iron za ziada). Saturation hunyanyasa waveform ya output ya secondary side, kukatafa uonyeshaji wa upasuaji wa primary.
Athari Zenye Uwezo:
Core Overheating: Hali ya moto ya core ya CT inaweza kusonga zaidi ya 120°C, kupiga insulation ya secondary windings na kuachia ratio inaccurate.
Protection Misoperation: Secondary current ikiwa imechanganyika huiwasha relays za protection (mfano, overcurrent protection) kuona "line short circuits" kwa uongo, kuteleka false tripping. (Mtandao wa distribution alitokea 10 feeder trips kutokana na saturation ya CT, kuathiri 20,000 nyumba.)
2. Vifaa vya Distribution: Matatizo Maradhi, Kupungua Usalama wa Mfumo
Vifaa vya distribution ni muhimu kwa "kuunganisha juu na chini" katika grid. THD ikidhulumiwa hutengeneza athari ya maradhi. Vikundi muhimu vilivyopata athari ni transformers za nishati, banks za capacitors, na reactors.
2.1 Transformers za Nishati (Distribution / Main Transformers)
Mbinu ya Athari: Voltage za harmonic zinazidi hysteresis na zao la eddy current katika cores za transformer (zao la iron za ziada); kengele za harmonic zinazidi zao la copper za winding. Pamoja, hizi zinazidi zao la jumla la sana. Unbalance ya harmoniki za tatu-phase pia zinazidi kengele ya neutral (hadhi kwa 1.5× kengele ya phase), kuchelewesha kupata moto kwa eneo la chini.
Athari Zenye Uwezo:
Core Overheating: Kwenye THDv = 8%, zao la iron za transformer zinazidi kwa 15%-20%. Hali ya moto ya core inasonga kutoka 100°C hadi 120°C, kuchelewesha kupungua kwa insulating oil (mfano, 25# transformer oil), kuzidi acidity, na kupungua dielectric strength.
Winding Burnout: Kupata moto kwa muda mrefu huchanganya winding insulation paper (mfano, Nomex), kuachia short circuits. Transformer ya 110kV ya substation aliyapata short circuit kwenye winding baada ya miaka 3 kutokana na 5th harmonic, na gharama za sarafu zikizidi 5 million RMB.
Punguza Muda wa Maisha: THD ikidhulumiwa kwa muda mrefu hupunguza muda wa maisha wa transformer kutoka 20 mwaka hadi 10–12 mwaka.
2.2 Shunt Capacitor Banks (kwa Compensation ya Reactive Power)
Mbinu ya Athari: Capacitive reactance hupunguza kwa frequency (Xc = 1/(2πfC)), hivyo harmoniki za juu huchanganya overcurrent. Ikiwa capacitors zinajenga "harmonic resonance" na grid inductance (mfano, 5th-order resonance), kengele inaweza kusonga hadi 3–5× value iliyotathmini—zaidi sana kuliko rating za capacitor.
Athari Zenye Uwezo:
Insulation Breakdown: Overcurrent hupiga moto ndani ya dielectrics (mfano, polypropylene film), kuchanganya puncture, bulging, au hata explosion. (Kitengo cha kiwango cha kimataifa lilitengeneza shamba tatu la 10kV capacitor banks ndani ya mwezi mmoja kutokana na 7th harmonic resonance; gharama ya sarafu kwa bank iliyotathmini ilikuwa zaidi ya 150,000 RMB.)
Protection Failure: Resonant currents hupiga fuse links; ikiwa protection haitekelezi, hatari ya moto inongezeka.
2.3 Series Reactors (kwa Suppression ya Harmonic)
Mbinu ya Athari: Ingawa yanatumika kuzuia harmoniki zisizo sahihi (mfano, 3rd, 5th), reactors zinazidi zao la copper za winding kwa muda mrefu wa kengele za harmonic. Magnetic fields za pulsating kutokana na harmoniki pia huzidi vibaya core vibration, kuchanganya wear ya mechanical.
Athari Zenye Uwezo:
Winding Overheating: Kwenye THDi = 12%, zao la copper za reactor zinazidi zaidi ya 30%; hali ya moto ya winding inasonga zaidi ya 110°C, kuchanganya insulation varnish kuchanganya na kusukuma.
Core Noise & Wear: Frequency ya vibration inawezekana na harmoniki, kutoa sauti ya juu (>85 dB). Kupigana kwa muda mrefu huchanganya silicon steel laminations, kupungua permeability na kuondoa suppression ya harmonic.
3. Vifaa vya Kutengeneza: Kupungua Output, Kusonga Hatari za Usalama
Vifaa vya kutengeneza ni "chombo cha nishati" la grid. THD ikidhulumiwa hupunguza usalama wa utendaji. Vikundi muhimu: synchronous generators, renewable inverters (PV/wind).
3.1 Synchronous Generators (Thermal/Hydro Plants)
Mbinu ya Athari: Harmoniki za grid zinarejelea stator windings za generator, kutengeneza "harmonic electromagnetic torque." Ingawa superimposed kwenye fundamental torque, hii hutengeneza "pulsating torque," kuzidi vibration. Kengele za harmonic pia zinazidi zao la copper za stator, kuchanganya kupata moto kwa eneo la chini.
Athari Zenye Uwezo:
Kupungua Output: Unit ya 300MW kwenye THDv = 6% hupata ±0.5% speed fluctuation kutokana na pulsating torque, kupungua output chini ya 280MW, kupungua efficiency kwa 5%-8%.
Winding Overheating: Hali ya moto ya stator inaweza kusonga hadi 130°C (kutokana na limit ya Class A insulation ya 105°C), kuchelewesha kuzeeka kwa insulation na kuathiri turn-to-turn short circuits.
Bearing Wear: Kuzidi vibration kungharibu bearing (mfano, sleeve bearing), kupungua muda wa maisha kutoka 5 mwaka hadi 2–3 mwaka.
3.2 Renewable Inverters (PV / Wind)
Mbinu ya Athari: Inverters ni sensitive kwa THD ya grid (kulingana na GB/T 19964-2012). Ikiwa point-of-interconnection THDv > 5%, inverter hutekeleza "harmonic protection" ili kupunguza athari. Pia, voltage ya harmonic huchanganya balance ya nishati kati ya DC na AC sides, kuchanganya IGBT module kupata moto.
Athari Zenye Uwezo:
Grid Disconnection: Kwenye farm ya wind na THDv = 7%, 20 units za 1.5MW inverters walitengeneza mapenzi sawa, kupunguza zaidi ya 100,000 kWh ya nishati ya wind katika siku moja, kutumia zaidi ya 50,000 RMB katika gharama za sarafu.
IGBT Burnout: Utendaji wa muda mrefu kutokana na harmoniki unazidi switching losses kwenye modules za IGBT (kundi muhimu), kusonga hali ya moto zaidi ya 150°C, kuchanganya "thermal breakdown." Gharama za sarafu kwa inverter inazidi 100,000 RMB.
4. Vifaa vya Dhibiti: Sampling Distortion, Malfunctions ya Mfumo
Vifaa vya dhibiti vinatenda kama "akili na mfumo wa neuroni" wa grid. THD ikidhulumiwa huchanganya data ya sampling na kutengeneza utaratibu wa utambulisho. Vikundi muhimu: protective relays, automation communication systems.
4.1 Protective Relays (Overcurrent / Differential Protection)
Mbinu ya Athari: Kengele za harmonic zinachanganya transient CT saturation, kutengeneza sampled current waveforms (mfano, flat-topped waves), kutengeneza algorithms za protection kuwasha amplitude na phase, kuteleka incorrect actions. Voltage za harmonic pia zinaweza kuchanganya power supplies za relay, kutengeneza malfunctions za logic circuit.
Athari Zenye Uwezo:
False Tripping: Mtandao wa distribution na THDi = 12% alitengeneza output ya CT kutokana na saturation, kutengeneza overcurrent protection kuwasha "line short circuit" na kuteleka 10 feeders, kupunguza nishati kwa 20,000 nyumba kwa masaa minne, kutengeneza gharama za sarafu zaidi ya 2 million RMB.
Failure to Trip : Ikiwa interference ya harmonic chuki ±10% voltage fluctuation kwenye power supply ya relay, logic circuit inaweza kuchapa, isifanye trip wakati wa matatizo halisi, kusaidia escalation ya matatizo.
4.2 Automation Communication Devices (RS485 / Fiber Modules)
Mbinu ya Athari: Electromagnetic radiation kutokana na harmoniki (mfano, 10V/m RF interference) inawezekana na communication lines, kutengeneza "bit flips" kwenye utambulisho wa data. Voltage za harmonic pia huchanganya clock modules, kuzidi synchronization errors.
Athari Zenye Uwezo:
Increased Bit Error Rate: Kutokana na interference ya harmonic, bit error rate ya RS485 communication katika mtandao wa distribution automation ilizidi kutoka 10⁻⁶ hadi 10⁻³, kusonga au kupunguza utaratibu wa utambulisho (mfano, "adjust capacitor switching").
Module Burnout: Harmoniki za juu zinaweza kuchanganya signal isolation circuits (mfano, optocouplers) katika communication modules, kutengeneza failure. Substation moja iliharibi 8 fiber modules ndani ya mwezi mmoja kutokana na interference ya 5th harmonic.
5. Vifaa vya End-Use: Kupungua Performance, Ajali za Utengenezaji
Vifaa vya end-use vinatenda kama "terminal load" ya grid. Vifaa vya kiwango cha kimataifa na precision hupata athari sana kutokana na THD ikidhulumiwa. Vikundi muhimu: industrial motors, vifaa vya precision (lithography machines / medical MRI).
5.1 Industrial Motors (Induction / Synchronous Motors)
Mbinu ya Athari: Voltage ya harmonic hutengeneza "harmonic currents" kwenye motor stator windings, kutengeneza "negative sequence rotating magnetic fields." Ingawa superimposed kwenye fundamental field, hii hutengeneza "braking torque," kuzidi speed fluctuations na vibration. Kengele za harmonic pia zinazidi zao la stator/rotor copper, kutengeneza kupata moto kwa jumla.
Athari Zenye Uwezo:
Efficiency Drop: Motor ya 100kW kwenye THDv = 7% hupunguza efficiency kutoka 92% chini ya 85%, kutumia zaidi ya 50,000 kWh kila mwaka (kwa 0.6 yuan/kWh, gharama za nishati zinazidi: 30,000 yuan/mwaka).
Burnout: Motor ya rolling mill ya chuo cha chuma lilipata burnout mara mbili ndani ya miezi minne kutokana na exposure ya 7th harmonic; hali ya moto ya stator ilisonga 140°C. Gharama za sarafu kwa motor iliyotathmini ilikuwa zaidi ya 2 million RMB.
Vibration & Noise: Acceleration ya motor vibration ilizidi kutoka 0.1g hadi 0.5g, sauti ilisonga zaidi ya 90dB, kutengeneza mazingira ya kazi na kuchanganya wear ya foundation.
5.2 Precision Equipment (Semiconductor Lithography Machines / Medical MRI)
Mbinu ya Athari: Vifaa hivi vyanahitaji voltage safi sana (THDv ≤ 2%). Harmoniki zinazidi ripple kwenye internal power supplies na kupungua ADC sampling accuracy, kwa ujumla kutengeneza kupungua performance.
Athari Zenye Uwezo:
Loss of Precision: Machine ya lithography ya semiconductor kwenye THDv = 4% ilipunguza laser positioning accuracy kutoka 0.1μm hadi 0.3μm, kupungua wafer yield kutoka 95% hadi 80%, kupungua zaidi ya 500,000 yuan kwa siku moja.
Equipment Shutdown: Harmoniki zilichanganya current fluctuations kwenye gradient coils za MRI, kupungua imaging, kutengeneza shutdowns. (Hospital ilipunguza vitendo vya MRI kwa siku mbili kutokana na excess ya 3rd harmonic, kupungua zaidi ya 100,000 yuan kwa gharama za diagnostic.)
Summary: Core Rules of THD-Induced Equipment Damage
Inductive Equipment (Transformers, Motors, Reactors): Vulnerable to "Additional Losses" — harmoniki zinazidi zao la iron/copper, kupata moto na kuzeeka ni athari muhimu.
Capacitive Equipment (Capacitors): Vulnerable to "Resonant Overcurrent" — harmoniki zinaweza kuchanganya resonance, kupata overcurrent-induced insulation breakdown ni athari muhimu.
Control Equipment (Relays, Communication Systems): Vulnerable to "Sampling Distortion" — harmoniki zinachanganya data, kutengeneza misoperations au failures to operate.
Precision Equipment (Lithography Machines, MRI): Vulnerable to "Waveform Distortion" — harmoniki zinazidi voltage ripple, kutengeneza kupungua accuracy.
Kwa hivyo, grids za nishati lazima kutumia strategia mbili:
"Harmonic Monitoring (controlling THD measurement error ≤ ±0.5%) + Active Filtering (APF) / Passive Filtering"
ili kudhibiti THDv ndani ya limit ya standard ya taifa ya 5%, kwa hivyo kupunguza athari ya vifaa kwa msingi.
