Uchunguzi wa Matukio ya Kutumika Kwa Mzunguko wa 10kV Puffer-Type Load Switch

1. Ufundi la Hitilafu

Mwajuni 2013, hitilafu ilifanyika katika kipengele cha umeme wa kiwango cha juu kinachofanya kazi katika eneo fulani la mji, kusababisha line ya 10kV kukata. Tafiti za nchi zilizopatikana zilionyesha kuwa kipengele chenye hitilafu kilikuwa switchgear ya pneumatic ring-network high-voltage (Aina ya HXGN2-10), na sifa ya hitilafu ilikuwa arc short circuit yenye tatu matumizi. Baada ya kutengeneza hitilafu na kurudia usambazaji wa umeme kwa wateja, ni muhimu kuzingatia kuwa switchgear ya aina hii ile yaliyopo katika eneo hili, ambayo ilianzishwa kati ya mwaka 1999 na 2000 (na muda wa kufanya kazi zaidi ya miaka 12, rated current inayotathmini ni 630A, na current halisi ya kufanya kazi ni zaidi ya ≤ 300A), imehitimu mara nyingi na hitilafu tofauti, kusababisha hatari kwa ufanisi wa grid ya umeme.

2. Sera ya Kufanya Kazi ya Pneumatic Load Switches

Kibanda cha ring-network kinanambarika kwa sababu ya kuwa na pneumatic load switch. Barua ya mawimbi yake pia inafanya kazi kama silinda ya hewa - mdhara unaonothibitisho wa "piston", unayodirishwa na mshtani mkuu kutokuwa na mawimbi ya kufunga na kufungua. Wakati wa kufungua, piston huongeza haraka hewa ndani ya barua ya mawimbi (silinda ya hewa), na hewa inayoungwa hutoka kwa arc uliofunika kwa separation ya arc-extinguishing contacts kupitia nozzle ya plastiki inayotegemea arc, kutokomeka arc kwa kutegemea; mzunguko wa hewa wa haraka hukurudi mara moja uwezo wa insulation wa medium kwenye kujitoa, kuzuia arc kutokomeka tena.

Kwa sababu ya uwezo mdogo wa switch kutoa fault currents (tu inapatikana kwenye mitandao chini ya 35kV ), mtazamo wa "separating the conductive element from the arc-igniting element" umetumika:

• Conductive element: Red copper plum-shaped contact fingers + conductive rod, amri ya kutuma current;

• Arc-igniting element: Copper-tungsten alloy arc-igniting rod + arc-igniting ring, hasa kwa arc ignition and extinction.

Wakati wa kufungua, sura ya nje ya barua ya mawimbi ya kubadilisha kwanza inasafiri kutoka kwa static contact fingers, basi arc-igniting ring inasafiri kutoka kwa arc-igniting rod. Arc unaweza kukaa kwenye arc-igniting components tu, kuzuia uzalishaji wa malipo kwa majukumu makuu; barua ya mawimbi na terminal ya chini zimeunganishwa kwa plum-shaped contact fingers ili kutahidi conduction ya umeme.

3. Tafiti ya Kina kuhusu Sababu za Hitilafu
(1) Tafiti ya Mwanzo (Ufundi wa Nje)

Rated current imetathmini ya switch hii ni 630A, lakini data ya dispatching inaonyesha kuwa operating current ya switch ya outgoing ya substation ni 283A, na theoretical current inayopita kwenye switchgear kwenye njia ni ≤ 283A. Pamoja na mazingira ya mahali (mashariki, hakuna mazingira ya kimvivyo kwenye kibanda), ufundi wa nje kama over-current, over-voltage, na flashover ya mazingira yanaweza kutengenezwa moja kwa moja, na hitilafu itasababishwa na ubovu wa switchgear yenyewe.

(2) Kutengeneza na Kutathmini Kwa Kutumia Majaribio

Baada ya kutengeneza kibanda chenye hitilafu, ni mapenzi ya awali kuwa "malipo mbaya kati ya mawimbi ya kubadilisha na static contacts kunasababisha overheating na burning", lakini hatua inaweza kutathminika kwa sababu ya uzalishaji mkubwa wa kibanda. Hivyo, utaratibu wa kutathmini kwa sampuli umefanyika kwenye switchgear ya aina hii yaliyopo:

• Withstand voltage and loop resistance: Kiwango cha withstand voltage ni sahihi, na loop resistance ni 114μΩ (inakidhi teknolojia );

• Temperature rise test: Data ya majaribio ya current-rising ya dakika 30 (Table 1 ) inaonyesha kuwa temperature rise inafika 84.2℃ kwenye 400A na hadi 133.1℃ kwenye 630A, far exceeding the national standard for stable judgment of “temperature rise ≤ 1K within 1 hour or ≤ 2K within 3 hours”.

(3) Utambuzi wa Sababu Za Kina

Utambuzi wa kina na tathmini ya muundo umaonyesha kuwa hitilafu inatoka kwa ukosefu wa mfumo wa malipo, kwa undani:

• Nguvu ya spring isiyosafi: Inaweza kutumia sana plum-shaped contact fingers, inaleta magonjwa ya "surface contact" kati ya contact fingers na barua ya mawimbi kwa "line contact", na kupunguza nguvu ya malipo;

• Ubovu wa uprocessing precision: Precision isiyo safi kwenye arc surface/planar processing ya plum-shaped contact fingers kunazozea malipo mbaya;

• Oxidation vicious cycle: Contact fingers na barua ya mawimbi zimefunika kwenye hewa, na oxidation inaweza kutumia sana contact resistance → increased heating → further attenuation of spring tension → worse contact effect, finally causing air ionization arc short circuit and line tripping.

4. Transformation ya Vifaa na Solutions za Optimization
(1) Process Upgrade: Precise Control of Contact Quality

Aiming at the core problem of “poor contact”, improvements are made from the material and processing ends:

• Spring selection: Adopt springs with high fatigue resistance to ensure stable spring force within the design life (including the condition of making and breaking the rated current ), avoiding contact problems caused by spring failure;

• Contact finger processing: Strictly control the processing precision of the arc surface and plane of the plum-shaped contact fingers to ensure complete fitting with the cylindrical arc surface of the movable contact rod, eliminating the hidden dangers of line contact/point contact, and ensuring the current-carrying capacity and temperature rise compliance of the contacts.

(2) Design Optimization: Full-process Condition Monitoring

Integrate the “online monitoring” function into the cabinet structure design to realize visual status:

• Temperature measurement window and probe: Set up a convenient temperature measurement window, install a temperature probe at the static contact, and display the temperature of the contact part inside the cabinet in real-time through the panel instrument;

• Data storage and early warning: Configure storage equipment to record operating data. Even if the equipment ages, abnormal situations can be identified in advance through data analysis, triggering the replacement and maintenance process, shifting from passive repair to active operation and maintenance.

(3) Operation and Maintenance Strengthening: Dynamic Defect Treatment

For the equipment in operation, optimize the operation and maintenance methods:

• Observation window transformation: Change the fixed observation window to a movable one to facilitate temperature monitoring inside the cabinet;

• Normalization of partial discharge testing: Carry out partial discharge testing of the switchgear during peak load periods to capture insulation defects in advance and avoid the expansion of faults.

5. Application Scenarios and Development Suggestions

With the increase in electricity consumption, the main lines of the distribution network are upgraded to large-cross-section cables of 300-400㎡, and the capacity of substations continues to grow. The shortcomings of insufficient breaking capacity and vulnerable contacts of pneumatic switchgear are becoming increasingly prominent. It is recommended that:

• Scenario adjustment: Withdraw from line ring-network applications and switch to high-voltage power distribution in terminal transformer areas (with a transformer capacity ≤ 630kVA ), utilizing its advantages of “simple structure and low cost”;

• Technology iteration: For line ring-network scenarios, give priority to selecting switchgear with higher reliability and stronger breaking capacity (such as vacuum load switches ) to meet the requirements of distribution network automation and high reliability;

• Value continuation: After the transformation of “process upgrade + online monitoring”, the pneumatic load switchgear can continue to serve terminal load scenarios and exert its residual value.