Customized Neutral Grounding Transformer Manufacturer-33kV

Although fully‑sealed oil‑immersed design reduces daily maintenance workload, regular visual and preventive checks are still recommended.

For on‑site routine inspection, operators should observe oil level indicator to keep oil within normal range, check for oil leakage at weld seams, flange and valve positions, inspect porcelain/composite bushing surface for dirt, crack or tracking discharge traces, verify reliable earthing connection of tank shell. For annual preventive maintenance, oil‑sampling test including dielectric strength is suggested, tightening high‑voltage terminal connections, cleaning insulator surface dirt.

Since earthing transformer operates mostly under no‑load status in normal grid condition, most failures only reveal themselves under actual earth‑fault events, so visual check of external components forms the major part of daily care. Major internal disassembly is generally not required for sealed units under normal service life.

Oil‑immersed earthing transformer uses mineral oil as insulation and cooling medium. It features strong overload capability, good heat dissipation performance and competitive unit cost, well‑suited for outdoor substations, wind‑solar power plants, mining and industrial field sites where fire‑safety restriction is not extremely strict.

Fully‑sealed tank construction supports long‑term maintenance‑free outdoor operation. Dry‑type earthing transformer adopts cast‑resin insulation without combustible mineral oil, mainly applied for indoor locations with strict fire‑protection requirements such as urban underground substations, data‑center auxiliary power houses.

Dry‑type units normally come with higher procurement cost and relatively limited overload margin. There is no absolute good‑or‑bad between two types; selection should balance fire risk, installation location, budget and local specification requirements.

Standard design is validated for altitude up to 1000 m and pollution class II. When equipment is deployed above 1000 m, air dielectric strength decreases with altitude.

It requires increased creepage and clearance distance for high‑voltage bushings, together with corresponding insulation derating. For coastal locations with heavy salt fog, anti‑salt‑fog composite bushings and enhanced anti‑corrosion painting for the whole tank structure will be adopted.

Cooling performance also degrades under high‑altitude low‑air‑density environment, so thermal derating calculation will be completed accordingly.

These environmental modifications are completed during factory production phase instead of on‑site retrofitting, so special operating conditions should be notified at technical clarification stage.

To deliver a fully‑matched technical proposal, several core site parameters should be shared at the early project stage.

Apart from system nominal voltage, you need to provide the measured or calculated total system capacitive earth fault current, selected neutral earthing scheme whether resonant earthing with arc‑suppression coil or resistive earthing with neutral grounding resistor, relay protection operating time which defines required short‑time fault duration.

In addition, actual site environmental conditions including altitude, maximum and minimum ambient temperature, pollution level, relative humidity, installation location indoor or outdoor should be clarified.

If auxiliary station‑service power is required, the load kVA value for secondary winding shall also be specified. Complete site data helps avoid under‑specification or over‑engineering, ensuring the equipment fits local grid protection coordination requirements.

Earthing transformers are designed for short‑time fault duty rather than continuous earth‑fault operation. The short‑time duration defines how long the unit can safely sustain full rated neutral fault‑current without over‑heating.

Rockwill offers standard options of 10 s / 30 s / 60 s. This time setting must be coordinated with your whole‑grid relay‑protection operating time. For example, fast‑tripping resistive‑grounded systems may select 10 seconds, while resonant‑earthed networks with delayed‑fault clearing commonly adopt 30 s or 60 s rating.

Wrong selection of short‑time duration may result in excessive over‑heating risk under actual earth‑fault incidents.

Global standards for grounding transformers fall into IEEE and IEC systems. IEEE 32 (North America) emphasizes fault withstand capability and zero-sequence impedance, while IEC 60076 series covers winding design, insulation, cooling, and short-circuit tests. Chinese standards follow IEC with additional grid-specific requirements on efficiency, temperature rise, and harmonics.