Quid notandum est in electione transformatoris currentis pro circuitu transformatoris stationis 10kV?
Experientia Practica Condivisa ab Ingeniero Electrico in Campo
Auctor Iacobus, Decem Anni in Industria Electrica
Salvete omnes, ego sum Iacobus, et decem annos in industria electrica laboravi.
A primis operibus in designo substationum et electione apparatorum, usque ad praefecturam commissionis systematis protectionis relai et automationis pro totis projectis, unus de frequentissimis apparatis in meo opere fuit transformator currentis (CT).
Nuper amicus, qui nunc initium facit, rogavit me:
“Quid debeat observari in electione transformatorum currentis pro circuitis stationis 10kV?”
Bona quaestio! Multi putant electionem CT esse de ratio currentis nominata — sed ut vere congruat necessitatibus circuiti, plures factores considerare debes.
Hodie vobiscum in simplici sermone — ex mea experientia manu propria per annos paucos — quae sunt puncta clava in electione CT pro circuitis stationis 10kV, quid singula parametra significent, et quemadmodum electionem rectam facias.
Nulla jerga complicata, nulla standardia infinita — sola scientia practica quam in vita reali uti possis.
1. Cur Importans Est Cura In Electione CT Pro Circuitis Stationis?
Licet stationis servitor non sit principalis transformer potentiae, tamen partem criticam in suppeditatione internae potentiae intra substationem agit — sicut potentia controlis, lux, potentia maintenance, et systemata UPS.
Si stationis transformer deficiat vel eius protectio mala geratur, potest evenire:
Amisso potentiae controlis;
Systema DC amittendo capacitate charging;
Tota substation claudens.
Et cum transformator currentis sit pars medulla pro protectione et mensuratione, eius electio directe afficit utrum protectio sit fidelis et mensurationes accuratae.
Itaque, eligere CT rectum = securitas + fidelitas + cost-effective.
2. Sex Puncta Clava in Electione CT Pro Circuitis Stationis 10kV
Ex mea decennali experientia in campo et praxi projecti, haec sunt sex consideranda maxime importantia:
Punctum 1: Currentes Nominati Primarii et Secundarii
Scopus: Ut CT normaliter operetur et exigentias sensibilitatis protectionis impleat.
Hoc est parametrum basicum et maxime importantem.
Combinatio communis:
Currentes primarii: 50A, 75A, 100A, 150A (ex capacitate stationis transformer)
Currentes secundarii: 5A vel 0.5A (plures dispositiva protectionis moderna 0.5A utuntur)
Consilium meum:
Usualiter elige currentem primarium ut 1.2~1.5 tempora nominati currentis stationis transformer;
Pro protectione microprocessor-based, prefer 0.5A output ut onus secundarium reducas;
Vita ne rating nimis altus eligas — aliter accuratio in currentibus parvis mala erit, affectans operationem protectionis.
Punctum 2: Gradus Accuratae Congruens Applicationi
Scopus: Ut diversae functiones (sicut protectio, mensuratio, metratio) signa accurata accipiant.
Diversae applicationes gradus accuratae diversos requirunt.
Gradus communes:
Winding mensurationis: Gradus 0.5
Winding metrationis: Gradus 0.2S
Winding protectionis: 5P10, 5P20, 10P10, etc.
Experientia mea:
Circuiti stationis transformer solent non exigere metrationem altae precisionis nisi in rebus billing;
Windings protectionis debent lineariatem tenere in short circuit;
CT multi-winding offerunt flexibilitatem maiorem et commendatur.
Punctum 3: Capacitas Output Nominata (VA Value)
Scopus: Ut CT possit dispositiva metrationis vel protectionis connecta movere.
Capacitas insufficiens potest cadere voltum causare, affectans accuratiam metrationis vel operationem protectionis.
Formula calculi:
Onus Totale = Impedance Cables + Impedance Input Dispositivorum Instrumentorum/Protectionis
Consilium meum:
Usualiter elige inter 10–30 VA;
Dispositiva protectionis microprocessor-based minus potentiam consumunt — capacitas minor acceptabilis;
Si cable secundarius longus (sicut plus quam 50 metrorum), capacitas opportuniter augeatur;
Noli cecus capacitas altus eligas — vitare saturatio nucleo.
Punctum 4: Examen Stabilitatis Thermalis et Dynamicae
Scopus: Ut CT possit currentem short-circuit tolerare sine damno.
In systematibus 10kV, currentes short-circuit potest attingere millia ampere.
Quomodo facias:
Inspece maximum currentem short-circuit (Ik);
Verifica CT stabilis thermalis currentem (It) et stabilis dynamicae currentem (Idyn);
Generaliter, It ≥ Ik (pro uno secundo), Idyn ≥ 2.5 × Ik
Casus realis: Olim habui CT explosisse post short circuit — extitit quod stabilis dynamicae currentem non satisfecit requirementibus systematis. Reponendo CT altioris rating solvit problemam.
Punctum 5: Modus Installationis et Typus Structurae
Scopus: Ut CT facile installetur et conservetur, et spatium disponibile conveniat.
CT communes includunt:
Typus core (communis in switchgear)
Typus post (aptus pro usu externo)
Typus bushing (saepe in transformeribus)
Consilium meum:
In switchgear 10kV, CT core-type sunt maxime communes;
Certe ut diameter foraminis nuclei conveniat magnitudini conductoris;
Pro spatiis angustis, considera CT split-core pro facilitate installationis et remotionis;
In ambientibus humidis vel corrosivis, elige modellos resistentes umori vel corrosioni.
Punctum 6: Polaritas et Modus Connectionis
Scopus: Ut directio signi ad relais protectionis et instrumenta correcta sit, vitando iudicium falsum.
Polaritas incorrecta potest ducere:
Mala operatio vel defectus protectionis;
Iudicium falsum de directione fluxus potentiae;
Falsa alerta in protectione differentiale.
Experientia mea:
Omnes CT debeant terminalia polaritatis (P1, P2) clare notare;
Uti connectione subtractive polaritatis consistentiter;
Semper fac testum polaritatis post installationem vel maintenance;
Uti tester polaritatis dedicatum vel methodum DC pro verificatione.
3. Alia Consilia Practica
In addition to the six key points above, here are some other important notes:
Configuratio Multi-Winding:
Separate windings for protection, measurement, and metering to avoid interference;
Reserve spare windings for future expansion.
Characteristics Excitationis:
Especially for protection windings, good excitation characteristics improve protection reliability;
If possible, perform an excitation curve test to confirm core performance.
Sample Selection Reference for a 50kVA Station Transformer
4. My Final Suggestions
As someone with 10 years of field experience, I want to remind all professionals:
“Don’t just look at the model number — always consider the actual circuit, protection setup, and installation environment when selecting a CT.”
Especially in seemingly "simple" 10kV station transformer circuits, improper selection often leads to serious consequences.
Here are my recommendations for different roles:
For Maintenance Personnel:
Learn how to read CT nameplate information;
Understand basic parameter meanings;
Be familiar with polarity testing methods;
Report any abnormalities promptly.
For Technical Staff:
Master CT selection calculation methods;
Understand protection winding characteristics;
Know how to interpret system short-circuit parameters;
Be able to analyze excitation curves.
For Managers or Procurement Teams:
Clearly define technical specifications;
Choose reputable manufacturers with stable quality;
Request full test reports from suppliers;
Maintain equipment records for traceability.
5. Closing Thoughts
Current transformers may look small, but they are the eyes and ears of the entire power system.
They’re not just about reducing current — they’re the basis for protection, the foundation for metering, and the guarantee of safety.
After 10 years in the electrical field, I often say:
“Details determine success or failure, and proper selection ensures safety.”
If you ever run into difficulties selecting CTs, dealing with frequent protection misoperations, or unsure if your parameters are suitable, feel free to reach out — I’m happy to share more hands-on experience and solutions.
May every current transformer operate stably and safely, safeguarding the accuracy and reliability of our power grid!
— Iacobus
