Selection of Transformers for Mining Projects: Key Considerations for Off-Grid and Grid-Connected Sites

Reliabilitas suplai tenaga listrik tambang secara langsung memengaruhi keselamatan produksi dan efisiensi operasional. Sebagai peralatan inti untuk konversi tenaga listrik, pemilihan transformator menentukan apakah seluruh sistem tenaga listrik tambang dapat beroperasi secara stabil. Namun, tambang tanpa jaringan (off-grid) dan tambang terhubung jaringan (grid-connected) berbeda secara mendasar dalam struktur sumber tenaga listrik dan mode operasi, sehingga fokus pemilihan transformator pun berbeda. Artikel ini menguraikan poin-poin kunci pemilihan transformator untuk kedua skenario tersebut.

Tambang tanpa jaringan sepenuhnya mengandalkan sumber tenaga listrik sendiri (generator diesel, panel surya PV, penyimpanan energi, dll.) dan tidak terhubung ke jaringan eksternal. Sistem harus menyeimbangkan pembangkitan dan konsumsi tenaga listrik secara real time secara mandiri. Artinya, fluktuasi sumber tenaga listrik (seperti sifat intermiten panel surya PV) harus diserap oleh sistem penyimpanan energi dan generator cadangan, sehingga menuntut kontinuitas pasokan yang lebih tinggi.

A grid-connected mine is linked to an external grid, which serves as the main or backup power source and provides stable voltage and frequency support. The mine can buy power from the grid and, where conditions allow, partly self-supply through renewable generation. The system is relatively less complex.

The choice of transformer for a mining project depends first on the safety level of the installation site.

Transformatores in oleo mergitos use insulating oil as the cooling and insulation medium. They have strong overload capacity and good heat dissipation, making them suitable for surface substations, open-pit areas, and other low-risk, heavy-load scenarios. Their purchase cost is lower, the technology is mature, and they offer good value in high-capacity power supply conditions. However, insulating oil carries risks of leakage and fire, and oil quality must be tested regularly.

Transformatores sicci generis utere funditione resinae epoxidicae ad insulandum. Sunt sine oleo, retardantes flammas et igni-resistentes, ideo apti ad cuniculos subterraneos et ad facies operis ubi est alta concentratio gasis vel spatia angusta. Sunt compacti, impervii ad pulverem et ad umorem, cum simplici cura ordinaria. Inconvenientia sunt maior pretium emptionis et capacitas sobrecaricandi relativus exigua.

In brevi: elige primum typum siccum pro locis subterraneis periculosissimis; typus oleo-immersus potest praeferreri pro locis in superficie et pro scenariis minore periculo.

Comparatio Scenariorum Applicationis

1. Adaptation to power source fluctuations. Off-grid systems often use a hybrid setup of "diesel generation + solar PV + energy storage." PV output fluctuations and diesel generator start/stop both cause voltage and frequency changes. The transformer needs good voltage regulation capability; an on-load tap-changing model may be necessary to handle frequent changes on the power source side.

2. Load impact withstand capability. Large equipment such as crushers and ball mills in mines can draw starting currents several times the rated value. An off-grid system lacks the strong support of a grid, so the transformer should have enough overload margin to prevent system voltage from dropping sharply when motors start. Capacity selection should be based on the actual load curve with reasonable redundancy.

3. Transport and installation conditions. Roads to remote mining sites are often limited, so transformer transport dimensions, weight, and on-site assembly feasibility must be considered. If an oil-immersed transformer requires on-site oil filling, oil treatment equipment and conditions must also be available.

1. Short-circuit impedance matching. During grid-connected operation, transformer short-circuit impedance must be coordinated with the grid's short-circuit capacity. Too low impedance leads to excessive short-circuit current, increasing the burden on switchgear; too high impedance causes excessive voltage regulation. Verification should be based on the expected short-circuit current provided by the grid.

2. Vector group selection. Onus extractionis includunt magnam partem apparatus non-linearium, ut convertitores frequentiae et initiatores molles; currentes harmonicorum possunt effectum habere in operatione transformatoris. Gruppus vectorialis Dyn11 melius perficit quam Yyn0 in resistendo harmonicis et supprimendo harmonicis tertius, ideoque est electio communis pro transformatoribus distributionis in minis coniunctis ad rete.

3. Configuratio capacitas et reservatio expansionis. Incrementum onus in minis coniunctis ad rete solitus est relativus stabilis. Capacitas transformatoris potest statui ad "onus actuale × 1,1–1,2", cum spatio expansionis reservato secundum planum cycli vitae mine. Capacitas nimis magna non solum incrementum perditas sine onere, sed etiam deprimet factor potentiae.

Pro proiektum mine carbo Nishbash in Uzbekistan, supplevimus tres stationes transformatorias praefabricatas stili Europaei, coniunctas rete, quarum potestas nominalis est 3150 kVA, et ratio tensionum 10/0.4 kV. Apparatus interruptivus altius tensionis, apparatus interruptivus inferioris tensionis, et transformatoris intra has stationes omnes a nobis fabricati sunt. Pro hoc proiecto, optima instrumenta ad proprietates proprias mine aptata sunt, una cum aliis factoribus ut altitudo, temperatio, et humiditas.

In specie, in electione transformatoris, plene consideravimus requisita coniunctionis ad rete. Denique transformator immersus oleo, cum gruppo vectorum Dyn11 et impedantia curtis circuitus 5.5%, electus est.

Q1. Necesse estne ut transformatores pro mineris usum habeant modulos speciales pro mineris?

Pro locis subterraneis et pro locis cum periculo explosionis, transformatores qui normas pro mineris implent (typus generalis aut typus ignis-resistens) utendi sunt. Stationes transformatoriae superfaciales et loca aperta excavata possunt transformatores industriales normales uti, sed hae normas gradus protectionis et resistentiae corrosioni implere debent.

Q2. Num transformatoribus siccis usus in tectis fieri potest?

Yes, sed custos clausura requiritur, saepe cum protectione gradus IP54 aut superioris, ad pulverem et humiditatem sustinendum.

Q3. Num minea extra reticulum transformator standardem reticuli coniunctum uti possunt?

Non recommendatur. Proprietates fontis electricitatis et schemata impactionis oneris systematum extra reticulum valde differunt ab his quae in systematis reticuli coniunctis inveniuntur. Transformator standardis reticuli coniunctus fortasse non poterit fluctuationes frequentes tensionis et impetus currentis initiationis sustinere.

Differentia principalis inter electionem transformatoris pro minis extra reticulum et pro minis reticuli coniunctis in diversis postulationibus quas proprietates fontis electricitatis in transformatorem imponunt . In scenariis extra rete, transformatoribus opus est quae fortius adaptentur ad tensionem et habeant maiorem marginem supra onus, ut fluctuationes fontium electricorum propriorum et impetus onerum sustinere possint. In scenariis coniunctis ad retem, magis attenditur ad adaptationem impedantiae, suppressionem harmonicorum, et coordinationem cum protectionibus retis. In utroque scenario, gradus securitatis semper est prima linea divisoria inter transformatores oleo-immersos et siccos — sicci subterranei, oleo-immersi in superficie. Haec regula manet immutata sive mina sit extra rete sive coniuncta ad retem.