Comhleacan Forbraiteach go hIomlán chun Togail agus Ríomhaireachtú Cáilleadóirí Circe

Conas mar a mheastar agus a shocraítear Briseáin Ciorcail

1. Cineálacha Briseán Ciorcail

1.1 Briseán Ciorcail Aer (ACB)
Ciúitear é freisin mar bhriseán ciorcail moldeáilte nó iarmhaiseach, agus tá gach comhbhaint á mbainistiú laistigh de fhoirm meicile isolaíoch. Is cosúil gur é an t-oidhreacht atá ann, ag ciontacht a chur ar aon seón leis na comhbhaill agus na codanna, agus is féidir é a chur chun cinn le roinnt acmhainní. Úsáidtear ACBs go minic mar scuabanna príomhfhóirithint. Icht trí réimeas a bhaineann leis na nitric trip san ACB: ilchumhachtach, eileac-tronic, agus eolach. Tugtar cosaint ceathrúil: am thréimhse fada, am thréimhse gairid, láithreach, agus faill sa talamh, agus is féidir gach suíomh cosanta a riaradh laistigh den réimse bunaithe ar mhéid an fhoirme.

Is oiriúnach ACBs do líonraí 50Hz AC le voltáid reatha 380V nó 660V agus curracha reatha idir 200A agus 6300A. Úsáidtear iad go príomha do díobháil cumhachta agus cosaint in aghaidh forlucht, undervoltage, cúrsaí gairide, agus talamh aon phhás. Tugann na briseáin seo roinnt feidhmeanna cosanta eolaíoch agus cosaint roghnach. Faoi chondae normálta, is féidir iad a úsáid don chuid uafásach gearrthacaíocht. ACBs le ráta suas go 1250A is féidir leo a chosaint ó forlucht agus cúrsaí gairide i gcórais 380V/50Hz.

Iarratais ginearálta ná scuabanna príomhfhóirithint ar an taobh 400V de transfeormaithe, scuabanna bus tie, scuabanna fóirithint ard-capacité, agus scuabanna rialú mórtór mór.

1.2 Briseán Ciorcail Moldeáilte (MCCB)
Ciúitear é freisin mar bhriseán ciorcail pluigin, agus tá a therminals, arc extinguishers, trip units, agus mechanisme oibriú laistigh de chothúchán plastic. Teastaíonn teagmháil cúnta, undervoltage trip units, agus shunt trip units go minic modiúla, ag tarlú a dhesign compordach. Ní hí an t-oidhreacht atá ag MCCBs go forleathan agus úsáidtear iad go minic cosaint scuab beag.

Tá thermal-magnetic trip units san ábhar i ndán do chuid mhór MCCBs. D'fhéadfadh modh mór a bheith ag cur isteach sensors solid-state. Is féidir overcurrent trip units a bheith ilchumhachtach nó eileac-tronic. Is gnách nach bhfuil MCCBs ilchumhachtach, ag tabhairt cosaint am thréimhse fada agus láithreach amháin. Tugann MCCBs eileac-tronic ceithre fheidhm cosanta: am thréimhse fada, am thréimhse gairid, láithreach, agus faill sa talamh. I measc na n-eisiomptaí nua, tá interlocking zonach selectach.

Úsáidtear MCCBs go minic do rialú agus cosaint scuab fóirithint, scuabanna príomhfhóirithint ar transfeormaithe díobhála beaga, teorainn rialú mórtór, agus mar scuabanna cumhachta do roinnt macasamhail.

1.3 Briseán Ciorcail Mín (MCB)
Is iad MCBs an t-eisiomptacht is leithne atá ann do chosaint teorainn i gcórais leictreachta foirgnimh. Cosnaíonn siad cúrsaí gairide, forlucht, agus undervoltage i gcúrsaí aon phhás agus trí phhás suas go 125A. Tá siad ar fáil i gcofigureáid 1P, 2P, 3P, agus 4P.

Consóidtear MCB as mechanisme oibriú, teagmháil, devices cosanta (réimsí trip éagsúla), agus system arc extinguishing. Dúnann teagmháil go manuálta nó leictreach agus coimeádann mechanisme free-tripping i bhfeidhm. Coil an overcurrent trip unit agus element heating an thermal trip unit táid connecteadh in series leis an gcircuit príomh, agus coil an undervoltage trip tá sé connecteadh in parallel leis an gcumhacht.

Sa díobháil leictreach foirgnimh, úsáidtear MCBs do forlucht, cúrsaí gairide, overcurrent, undervoltage, ground fault, protection fuar, automatic transfer dual power sources, agus motor starting agus cosaint uafásach.

2. Paramaithe Téchniciúla Príomha Briseán Ciorcail

• Voltáid Oibriú Rátáilte (Ue)
  An voltáid ainmnithe a bhfuil an briseán ciorcail deartha chun oibriú leanúnach faoi chondae speisialta. In China, do chórais go dtí 220kV, is é an voltáid oibriú is airde 1.15 uair an chomhthéacs rátáilte; do 330kV agus os cionn, is é 1.1 uair. Caithfidh an briseán cothrom le dáth agus déan oibriú switch ag an voltáid oibriú is airde an chórais.

• Currach Rátáilte (In)
  An currach a d'fhéadfadh an trip unit a thógáil leanúnach ag teorainn teoranta 40°C. Do tripp units a riaradh, is é seo an currach riatraithe is airde. Ag teorainn os cionn 40°C (go dtí 60°C), is féidir derating.

• Cuirreád Trip Forlucht (Ir)
  Trioptar an briseán le tréimhse ama nuair a mhairíonn an currach Ir, rud a léireann an currach is airde a d'fhéadfadh an briseán a thógáil gan triop. Caithfidh Ir a bheith níos mó ná an currach is airde (Ib) ach níos lú ná an currach cheadaithe (Iz). Do thermal-magnetic breakers, is gnách go bhfuil Ir riatraithe ó 0.7 go 1.0In; trip units eileac-tronic tugann réimse níos leithne, gnách 0.4 go 1.0In. Do tripp units ratch, Ir = In.

• Cuirreád Trip Cúrsa Gairid (Im)
  An tairseach a bhfuil an instantaneous nó short-time trip unit ag éileamh chun an circuit a scuabadh go tapa le linn curracha faill airde.

• Currach Taisce Am Thréimhse Gearr (Icw)
  An currach a d'fhéadfadh an briseán a thaisceadh le tréimhse ama sonraithe gan damáiste téarma.

• Breaking Capacity
  An currach faill is airde a d'fhéadfadh an briseán a scuabadh sábháilte, neamhspleách dá currach rátáilte. Luachanna coitianta ná 36kA agus 50kA. Tá sé roghnaithe i breaking capacity críochnúil (Icu) agus service (Ics).

3. Prionsabail Ginearálta do Thogáil Briseán Ciorcail

• Voltáid oibriú rátáilte ≥ voltáid rátáilte an chircuite.

• Currach making/breaking rátáilte an chircuite ≥ currach an lodáil ríomhtá.

• Currach making/breaking rátáilte an chircuite ≥ an currach faill is airde atá féidir sa circuit.

• Currach faill aon phhás-talamh ag deireadh an chircuite ≥ 1.25 × suíomh (instantaneous nó short-time) trip.

• Undervoltage trip unit rated voltage = circuit rated voltage.

• Shunt trip unit rated voltage = control power supply voltage.

• Electric operating mechanism rated voltage = control power supply voltage.

• Do chuid ghairte, set instantaneous electromagnetic trip current to 6 times the load current.

• For single motor short-circuit protection: 1.35× motor starting current (DW series) or 1.7× (DZ series).

• For multiple motors: 1.3× largest motor starting current + sum of other motors’ running currents.

• As main transformer low-voltage side switch: breaking capacity > transformer’s low-voltage short-circuit current; trip rated current ≥ transformer rated current; short-circuit setting = 6–10× transformer rated current; overload setting = transformer rated current.

• After preliminary selection, coordinate with upstream and downstream breakers to prevent cascading trips and minimize outage scope.

4. Selectivity of Circuit Breakers
Circuit breakers are classified as selective or non-selective. Selective breakers offer two- or three-stage protection: instantaneous and short-time for short circuits, long-time for overload. Non-selective breakers are typically instantaneous (short-circuit only) or long-time (overload only). Selectivity is achieved using short-time delay trip units with different time settings. Key considerations:

• Upstream instantaneous trip setting ≥ 1.1 × maximum 3-phase short-circuit current at downstream breaker’s output.

• If downstream is non-selective, upstream short-time trip setting ≥ 1.2 × downstream instantaneous trip setting to maintain selectivity.

• If downstream is also selective, upstream short-time delay time ≥ downstream short-time delay time + 0.1s.
  Generally, Iop.1 ≥ 1.2 × Iop.2.

5. Cascading Protection
In system design, coordination between upstream and downstream breakers ensures selectivity, speed, and sensitivity. Proper coordination allows selective fault isolation, maintaining power to healthy circuits. Cascading uses the current-limiting effect of the upstream breaker (QF1). When a short circuit occurs downstream (at QF2), QF1’s current-limiting action reduces the actual fault current, allowing QF2 to interrupt a current higher than its rated capacity. This allows use of lower-cost, lower-breaking-capacity downstream breakers. Conditions include no critical loads on adjacent circuits (since QF1 trip would blackout QF3), and proper matching of instantaneous settings. Cascading data is determined by testing and provided by manufacturers.

6. Sensitivity of Circuit Breakers
To ensure reliable operation during minimum fault conditions, sensitivity (Sp) must be ≥1.3 per GB50054-95:
Sp = Ik.min / Iop ≥ 1.3
Where Iop is the instantaneous or short-time trip setting, and Ik.min is the minimum short-circuit current at the protected line end under minimum system operation. For selective breakers with both short-time and instantaneous trips, only the short-time trip sensitivity needs verification.

7. Selection and Setting of Trip Units

(1) Instantaneous Overcurrent Trip Setting.Must exceed the circuit’s peak current (Ipk) during motor startup:
Iop(0) ≥ Krel × Ipk
(Krel = reliability factor)

(2) Short-Time Overcurrent Trip Setting and Time
Iop(s) ≥ Krel × Ipk. Time delays are typically 0.2s, 0.4s, or 0.6s, set to ensure upstream operation time exceeds downstream by one time step.

(3) Long-Time Overcurrent Trip Setting and Time
Protects against overload: Iop(l) ≥ Krel × I30 (maximum load current). Time setting must exceed allowable short-term overload duration.

(4) Coordination Between Trip Settings and Cable Capacity.To prevent cable overheating or fire without tripping:

Iop ≤ Kol × Ial
Where Ial = cable’s allowable current-carrying capacity, Kol = short-term overload factor (4.5 for instantaneous/short-time trips; 1.1 for long-time trip as short-circuit protection; 1.0 for overload protection only). If not satisfied, adjust trip setting or increase cable size.