Mfano wa Sera ya Mtegesho na Uchunguzi wa Vifaa vya Kubadilisha Kwa Nishati Elektroniki
1 Usalama wa Mfano wa Voltage na Current Transformers
1.1 Usalama wa Mfano wa Voltage
Transformers za kiambatanishi huchukua voltage kwa kutumia njia ya capacitive voltage division. Tangu voltage juu ya capacitor haawezi kubadilika haraka, voltage ya pili inayopatikana moja kwa moja kupitia capacitive voltage division ina jibu la muda chache na upimaji wa chini. Kwa kuongeza usahihi wa upimaji, resistor rasimu wa sampling unaofanikiwa unafanikiwa kuhusishwa kwa parallel juu ya capacitor ya voltage chache. Usalama wake unavyoonyeshwa katika Fig 1.
Katika Fig 1, kwa hatua
Voltage ya pili ya capacitor ya voltage division ni muunganisho wa time-derivative ya voltage iliyopimwa. Kwa kuongeza link ya integration, voltage ya mwisho unaweza kupimwa.
Katika Fig 1, tangu zaidi ya drop ya voltage kunafanyika juu ya C1, kuna maagizo magumu sana ya insulation ya capacitor C1. Katika electromagnetic voltage transformers, power capacitors mara nyingi hutumiwa, lakini katika electronic voltage transformers, power capacitors hawatumii; badala yake, equivalent capacitors hufundishwa.
Muundo wa capacitor ya voltage division ni kuwa cylinder uliyojengwa na material ya insulating uneopeshwa kwenye rod ya conductive. Kisha, double-layer flexible circuit board inajulikana kwenye nje ya cylinder. Resistor rasimu ni chip resistor unayoelekezwa kwenye outer layer ya flexible circuit board. Schematic diagram ya structure ya capacitor voltage divider inavyoonyeshwa katika Fig 2.
Capacitance ya C1 inajengwa na inner-layer cylinder. Rod ya conductive ni sawa na electrode plate moja, na copper film ya nje ya flexible circuit board ni sawa na electrode plate nyingine, na material ya insulating kama dielectric. Capacitance ya C2 inajengwa na outer-layer cylinder. Double-sided copper films za double-layer flexible circuit board ni sawa na electrode plates, na base material ya flexible circuit board, kama vile polyimide, inafanya kazi kama dielectric. Radial cross-sectional view yake inavyoonyeshwa katika Fig 3. Equivalent capacitance C inaweza kuhesabiwa kwa kutumia Formula.
Katika formula: r1 ni radius ndani ya cylinder; r2 ni radius nje ya cylinder; H ni urefu wa flexible printed circuit board; εr ni relative permittivity ya electrolyte; ε0 ni vacuum permittivity.
1.2 Usalama wa Mfano wa Current
Transformers za kiambatanishi huchukua current kwa kutumia Rogowski coils. Uhusiano wa voltage ya pili na current ya mwisho inavyofanuliwa ni kama ifuatavyo:
Katika formula, M ni constant isiyo na uhusiano na position ya current iliyopimwa. Voltage ya pili ya Rogowski coil ni muunganisho wa derivative ya current iliyopimwa. Kwa hiyo, kwa kuongeza link ya integration baada ya output ya Rogowski coil, current iliyopimwa inaweza kurudia.
Katika mradi huu, Rogowski coil ni Rogowski coil uliojengwa na printed circuit board. Sensitivity, accuracy ya upimaji, performance stability, product interchangeability, na production efficiency zao zote ziko zaidi kuliko za traditionally wound coils.
Kutokasisha madhara ya magnetic field ya accessory na kuongeza accuracy ya upimaji, Rogowski coil uliojengwa na printed circuit board mara nyingi hutumia two coils connected in series kufanya input tofauti. Directions za winding za PCB coils hizi ni tofauti. Moja inawound kulingana na right-hand rule, na nyingine inawound kulingana na left-hand rule. Hivyo, induced voltages watatu wana polarity tofauti, na voltage ya pili ya series connection ni mara mbili ya single Rogowski coil, kama inavyoonyeshwa katika Fig 4.
1.2 Usalama wa Mfano wa Current (Imarika)
Kwa sababu ya thermal expansion coefficients tofauti za copper film na PCB substrate, viwango vya deformation vyao vya temperature vyanavuka. Kurekebisha makosa yanayotokana na deformation na kukidhania copper film breakage, PCB coils zinazojengwa huenda kwenye temperature aging process. Process hii, kila upande, huweka stress ndani ya coils ili kurekebisha makosa, na kila upande, huifanya screening ya coils.
Hata hivyo, ingawa Rogowski coils wenye differential output wanayo uwezo mkubwa wa common-mode suppression, electric field interference ya 10 kV bado ni significant. Kwa hivyo, ni lazima kuwrap Rogowski coils kwa copper foil na ground copper foil.
2 Usalama wa Mfano wa Combined Electronic Transformers
2.1 Diagram ya Block ya Combined Electronic Transformers
Diagram ya block ya combined electronic transformer inavyoonyeshwa katika Fig 5. Voltage na current ya mwisho huconvert kwa secondary signals kwa kutumia capacitor na Rogowski coil. Kwa kuintegrate na kushift phase za secondary signals, signals proportional to primary signals zinaweza kupatikana. Kurekebisha accuracy, integration na phase compensation za measurement signals zinaweza kufanyika kwa kutumia digital signal processing methods. Lakini, digital signal processing ina delay fulani na haiwezi kurudi primary signals kwa muda. Kwa hiyo, method hii ya processing si nzuri kwa protection signals. Tangu protection signals zina requirements chache za accuracy, analog circuits zinaweza kutumika moja kwa moja kwa amplification, integration, na phase compensation processing.
2.2 Muundo wa Sensing Head wa Combined Electronic Transformer
Combined electronic transformer hunyakua voltage measurement unit na current measurement unit kwenye muundo unavyoonyeshwa katika Fig 6 kutumia epoxy resin vacuum casting.
Rogowski coil ina cast kwenye current-carrying busbar. Baada ya amplification, signal ya output ya coil inatuma kwenye output terminal kupitia signal line. Tangu amplifier anahitaji dual power supply, 3 of the multi-core signal lines zinatumika kwa power transmission.
Kwa sababu hakuna current inayotoka kwenye conductive rod ya voltage transformer, na kuongeza creepage distance, muundo unaofanikiwa ni kuwa conductive rod na current-carrying busbar perpendicular kwa kila mmoja.
Kwa sababu sensing head ni active type, umri wa components za electronics unachokata sana umri wa sensing head ya electronic transformer. Kwa hiyo, vitu vyote vinapaswa kujaza aging screening kabla ya kutumika.
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3 Testing ya Combined Electronic Transformer
Kulingana na usalama wa juu na muundo, pamoja na standards za IEC 60044-7 na IEC 60044-8, prototype ya 10 kV/600 A integrated voltage/current electronic transformer imeundwa. Kwa voltage transformer, accuracy ya upimaji ni Class 0.5, na protection level ni 3P; kwa current transformer, accuracy ya upimaji ni Class 0.2, na protection accuracy ni 5P20.
Wakati wa testing, currents tofauti zinatoka kwenye electronic transformer na voltages tofauti zinapatikana kwenye. Output ya pili inatoka kwenye digital port. Baada ya kuonyeshwa kwa digital display unit, inachukua kwa reference current transformer na reference voltage transformer. Accuracy ya upimaji yake inafanikiwa design requirements.
Pia, power frequency withstand voltage, partial discharge, lightning impulse, na electromagnetic compatibility tests zinajitokeza kwenye prototype. Passing ya tests hizi inaonyesha ukweli wa scheme ya design.
4 Matakwa
(1) Kutumia capacitor ya voltage division unayofanuliwa na Rogowski coil uliojengwa na printed circuit board kama sensors za voltage na current, una muundo wa chache, product interchangeability nzuri, na accuracy ya upimaji ya juu.
(2) Kwa kutumia teknolojia za printed circuit board na flexible printed circuit board, amplification circuit inaweza kujenga ndani ya sensing head, kurekebisha signal-to-noise ratio ya measurement signal.
(3) Kuhusisha electronic voltage transformer na electronic current transformer kwa moja kufanya combined voltage-current transformer inaweza kuchukua gharama za primary equipment na pia kurekebisha accuracy na capacity ya secondary circuit kwa voltage ya single line. Inafanuliwa miaka mapya ya secondary metering na protection na pia inafanuliwa concept ya control ya modern power systems iliyotumika kwa switchgear intervals kama units.
