Uchambuzi na Upatikanaji wa Matukio ya Kimistari ya Mfumo wa Kusambaza Umeme wa Nje wa 35 kV

1. Ushauri

Ukosefu wa nyuzi na ukosefu wa fuse ya upande wa kwanza katika transforma zilizounganishwa huathiri usahihi wa uchunguzi wa nishati na hupata sana utaratibu wa matumizi ya umeme. Hii inachambua marudio ya kuongeza ukosefu wa PT na fuse na kutathmini sababu za hitimisho, kutafuta suluhisho, na kupunguza miktadha ya nishati bila usahihi kwa kutumia viwango vya tamaani. Hii inaweza kupunguza hasara za grid na kupunguza hatari za huduma.

1.1 Ushauri kuhusu Transforma Zilizounganishwa

Katika mfumo wa umeme, transforma zilizounganishwa ni muhimu kwa ajili ya udhibiti na usalama. Zinafaa kuunda PT (voltage transformers) na current transformers, wakati wanatumia tofauti ya maonyesho ya coils za upande wa kwanza na upande wa pili ili kubadilisha voltage na current kali ya upande wa kwanza kwenye voltage na current ndogo yenye ustawi wa upande wa pili. Pia, wanaweza kufanya usafi wa kiwango cha umeme kati ya upande wa kwanza na upande wa pili ili kukuhusisha usalama wa watu na vifaa.

2. Hatari za Hitimisho la Transforma Zilizounganishwa

Kama vifaa muhimu vya uchunguzi wa nishati, PT ya transforma zilizounganishwa inahusika kubadilisha ishara za high-voltage kwenye ishara za low-voltage kwa ajili ya metering/protection devices. Waktu PT huonekana au high-voltage fuse huuonekana, hatari ni:

• Uchunguzi Usio sahihi : Ukosefu wa PT na fuse unaweza kuchanganya mfumo wa uchunguzi wa nishati, kunyanyasa usahihi wa uchunguzi na kutengeneza magogoro kati ya mashirika ya umeme na wateja.

• Marejeo Ya Vifaa Kilichoongezeka : Ukosefu wa PT unaweza kusababisha imbalansi ya system voltage (juu/sikitiko), kunyang'anya ustawi wa mfumo; hitimisho la transformer linaweza pia kusababisha malengo ya vifaa vya protection, kunyanyasa hatari ya marejeo ya vifaa vingine.

• Hatari za Kibinafsi : Transforma zilizounganishwa ni vifaa vya high-voltage. Ukosefu unaweza kusababisha breakdown ya insulation na leakage, kunyanyasa salama ya watu ambao wanaendesha na kuweka ustawi.

3. Sababu za Hitimisho la Overvoltage kwenye Transforma Zilizounganishwa

Wakati wa matumizi halisi, transforma zilizounganishwa mara nyingi huonekana kwenye ukosefu wa fuse ya high-voltage na PT. Sababu muhimu zinazohusiana ni:

• Ferromagnetic Resonance Overvoltage : Mtaani ferromagnetic huwa linear chini ya rated voltage. Wakati wa hitimisho, magnetic circuit husawa, na inductance huanza kubadilika non-linear. Huundwa loop ya oscillation na capacitance ya mfumo, inayatengeneza ferromagnetic resonance. Overvoltage hii huonekana mara nyingi fuse ya high-voltage ya PT, kunyanyasa usalama wa grid.

• Ongezeko la Secondary Load : Ongezeko la secondary load huonekana kwa transformer kuongeza joto na kuwa na ugumu wa kupunguza. Joto la winding linaongea juu, hujenga PT.

• Primary - Secondary Side Short Circuit : Short circuits ya upande wa kwanza/pili ya PT hunza currents kali, kunyanyasa ukosefu wa high-voltage fuse na equipment burnout.

• Switching Overvoltage : Matumizi yasiyo sahihi yanaweza kuchanganya overvoltage, kunyanyasa ukosefu wa high-voltage fuse ya PT.

• Lightning Overvoltage : Direct/inductive lightning overvoltage hukosa winding insulation, kunyanyasa vifaa.

4. Tathmini ya Mfano
4.1 Taarifa ya Mtumiaji Msingi

Tarehe 23 Agosti 2021, ukosefu wa PT wa A-phase ulihitimu kwenye transforma zilizounganishwa ya mtumiaji wa 35 kV, kunyanyasa usahihi wa uchunguzi wa nishati. Katika mwaka uliopita, transforma hii ilikuwa na hitimisho tatu. Kabla ya Januari 2021, mtumiaji alipewa nguvu kutoka kwa Shazi Substation ya 35 kV na uchunguzi wa kawaida. Baada ya Agosti 2021, nguvu zilipewa kutoka kwa mzunguko wa 35 kV wa Zhoujiaba Substation ya 110 kV (Zhouwan Line #353 na Zhouri Line #354). Umbo la mzunguko ni umbali wa karibu 1.5 km. Upande wa 35 kV una ground kwa arc-suppression coil. Points za uchunguzi zimeundwa kwenye mzunguko wa 2-circuit 35 kV ya Zhoujiaba Substation ya 110 kV. Primary wiring imeonyeshwa kwenye Chumba 1.

4.2 Points za Uchunguzi na Timeline ya Hitimisho

Mipengele yote miwili yamechaguliwa 35 kV combined transformers, na connection ya three-phase three-wire na V/V connection kwa voltage transformers. Kati yake:

• 35 kV Zhouri Line #354 (Point 2 ya Uchunguzi): Inafanya kazi vizuri, hakuna hitimisho;

• 35 kV Zhouwan Line #353 (Point 1 ya Uchunguzi): Marudi ya hitimisho.

Timeline ya Hitimisho:

• Agosti 23, 2021: Ukosefu wa PT wa kwanza, ulirekebishwa na bidhaa za Henan Xinyang Hutong Electric Co., Ltd.;

• Machi 4, 2022: PT hurekebishwa tena, ulirekebishwa na combined transformers za Jiangxi Gandi Electric Co., Ltd.;

• Juni 13, 2022: C-phase high-voltage fuse huuonekana, voltage loss;

• Septemba 21, 2022: A-phase high-voltage fuse huuonekana, voltage loss tena.

4.3 Tathmini ya Hitimisho

Wakati hitimisho lilifika, mizigo ya mtumiaji lilikuwa kidogo, wiring ya pili ilikuwa safi, na hakukuwa na short circuit. Baada ya ujaribishaji:

• Resistance ya grounding ya mzunguko ilikuwa safi, na ilikuwa ya mfumo usio sahihi. Grounding faults zinaweza kusababisha lightning current isisaidie, kunyanyasa ukosefu wa fuse;

• Hakuwa na overvoltage wakati wa matumizi, kunyanyasa sababu za binadamu.

Pamoja na majiba ya hitimisho na sababu zinazofanikiwa, sababu kuu inaelekea kuwa ferromagnetic resonance overvoltage, na scenarios za kuongeza:

• Kuondolewa na Grounding Faults: Wakati single-phase grounding linavyofika mzunguko, PT winding na line-to-ground capacitance hufanya parallel circuit, kufikia conditions za ferromagnetic resonance. Single-phase grounding huchanganya voltage ya mbili ya phase, iron core husawa haraka, na resonance huchanganya winding current, kunyanyasa ukosefu wa high-voltage fuse; overcurrent la muda mrefu pia linaweza kuchanganya PT.

• Kuondolewa na Matumizi Yasiyo sahihi: Three-phase load ya mfumo ni balance, lakini wakati wa switching operations, phases tatu hazijafanya kwa pamoja (closing/opening si simultaneous), kuchanganya inrush current kwenye winding na iron core ya voltage transformer, kunyanyasa ferromagnetic resonance overvoltage.

4.4 Suluhisho

Baada ya kutathmini sababu za hitimisho, hatima hizi zimechaguliwa:

• Install Harmonic Elimination Devices: Install 1 set of harmonic elimination devices kwenye upande wa 35 kV bus ya substation ili kupunguza recurrence ya ferromagnetic resonance.

• Overvoltage Protection kwenye Upande wa Pili: Install overvoltage protection devices kwenye upande wa pili ili kupambana na overvoltage zinazotokana na environmental factors na kuhifadhi insulation ya ndani ya transformer.

• Harmonic Detection and Treatment: Tutumia on-site electric energy meter calibrator kudeteza harmonics kwenye voltage ya pili. Ikiwa kuna abnormality, tuwasiliane na wateja kutafuta suluhisho ili kutathmini GB/T 14549 - 1993 "Power Quality - Harmonics in Public Power Grids": Total harmonic distortion rate of 35 kV voltage ≤ 3%, odd-order harmonics ≤ 2.4%, even-order harmonics ≤ 1.2%.

Matokeo ya Implementation: Baada ya hatima hizi zimefanyika, transforma zilizounganishwa zinaenda vizuri, hakuna ukosefu wa PT au fuse melting faults.

4.5 Reconciliation Calculation ya Electricity Quantity

Usahihi wa uchunguzi wa nishati unahusika na maslahi ya kiuchumi kati ya wateja na mashirika ya umeme. Hitimisho yanahitaji reconciliation ya electricity quantity. Hii inachukua mfano wa hitimisho wa tatu na kutumia correction coefficient method kwa hisabati:

Serikali: Compare active power wakati wa uchunguzi sahihi na wakati wa uchunguzi usio sahihi kutokuwa na correction coefficient k, basi calculate reconciliation electricity quantity \(\Delta W\). Kushtari load balance, formula ya correction coefficient k ni:

(1) Interpretation of Correction Coefficient k

Wakati k > 1, active power wakati wa uchunguzi sahihi ni zaidi ya wakati wa uchunguzi usio sahihi. Energy meter under-registers electricity wakati wa hitimisho, na mtumiaji anapaswa kusaidia electricity quantity. Wakati k = 1, energy meter anachunguza sahihi. Wakati 0 < k < 1, energy meter over-registers electricity, na electricity quantity inapaswa kurudishwa kwa mtumiaji. Wakati k < 0, energy meter anachanganya, na mtumiaji anapaswa kusaidia electricity quantity.

(2) User-related Metering Parameters

Capacity ya mtumiaji ya reception ni 2500 kVA, na njia ya uchunguzi ni high-supply high-metering (metered by a high-voltage combined metering box). Voltage ratio ni 35000 V/100 V, na current ratio ni 50 A/5 A. Multiplier wa uchunguzi wa juu ni 3500. Capacity ya energy meter ni 3&times;100 V/3&times;1.5 - 6 A, na accuracy ni 0.5S.

Hitimisho la tatu la mtumiaji lilifika tarehe Juni 13, 2022, na phase C ilipoteza voltage. Nguvu zilirudi karibu saa 8:00 tarehe Agosti 4, 2022. Time-of-use electricity pricing ilianzishwa tarehe Julai 1, 2022. Data zilizokolekwa kama system voltage, power, na power factor zimeonyeshwa kwenye Meza 1.

Calculation of Reconciliation Electricity Quantity for the First Stage

Kama inavyoonekana kwenye Meza 1, wakati wa Juni 13, 2022 hadi Juni 30, 2022, voltage ya phase A ni normal, average power factor ni 0.82, na element angle ni 34&deg;(L). Basi power factor angle &phi;=4&deg;(L).Assuming that the load is balanced, the correction coefficient is:

The calculation of the reconciliation electricity quantity is as follows:

From Formula (2) and Formula (3), it can be seen that k > 1, meaning the electricity is under-measured, and an additional electricity quantity of 15,134 kWh should be recovered.(2) Calculation of Reconciliation Electricity Quantity for the Second Stage.During the period from July 1, 2022 to August 4, 2022, the voltage of phase A is normal, the average power factor is 0.87, and the element angle is 29&deg;(L). Then the power factor angle &phi;=0&deg;.Assuming that the load is balanced, the correction coefficient is:

The calculation of the reconciliation electricity quantity is as follows:

From Formula (4) and Formula (5), it can be seen that k > 1, meaning the electricity is under-measured, and an additional electricity quantity of 51,996 kWh should be recovered.Total reconciliation electricity quantity to be recovered:

5. Mwisho

Katika matumizi halisi, transforma zilizounganishwa mara nyingi huonekana na ukosefu wa high-voltage fuses, kunyanyasa usalama wa grid. Mara nyingi, suala haya huonekana kutokana na overvoltage resonance, pamoja na design/selection ya vifaa isiyosafi na parameter mismatches.

Wakati wa kutathmini hitimisho: Kwanza, angalia defects za transformer na verification ya high-voltage fuse capacity. Pili, install primary harmonic elimination devices sahihi kumpiga resonance overvoltage. Baada ya ajali, jibu kwa haraka na kushughulikia vizuri ili kupunguza escalation na athari za jamii. Mwishowe, jifunze kutoka kwa tajriba, improve skills za kutatibu hitimisho, na kuhakikisha usalama wa grid.