What are the main cooling methods for transformers?

Transformers generate heat during operation, which must be dissipated through cooling methods. Common cooling methods include:

ONAN: Relies on natural convection of transformer oil and heat dissipation through the tank surface.

ONAF: Adds fans to the oil-immersed self-cooling system to force air movement and improve cooling efficiency.

OFAF: Uses an oil pump to force oil circulation through an air cooler for higher cooling efficiency.

ODAF: Forces oil flow along specific paths through the windings to directly remove heat, resulting in lower temperature rise.

Our company's transformers support the above cooling methods and can be flexibly configured according to site conditions.

What precautions should be taken when adding oil to a transformer during operation?

Oil can be added to a transformer without powering it off, but to ensure safety, the following steps are recommended:

* Prevent oil mixing: New oil must be tested to ensure compatibility with the existing oil in the tank.

* Switch protection: Before adding oil, temporarily set the heavy gas protection to "signal" mode to prevent false tripping.

* Release gas: After adding oil, check and release any gas accumulated in the Buchholz relay, then restore heavy gas protection to "trip" mode.

* Control oil volume: The oil volume should be appropriate, matching the current oil temperature (refer to the oil level-temperature curve).

* Do not add oil from the bottom: Never add oil through the bottom valve, as this may stir up sediments and affect internal insulation and heat dissipation.

Under what conditions must a transformer be immediately taken out of service?

To ensure equipment and personal safety, the transformer must be stopped immediately if any of the following occurs:

* Abnormal internal noises, such as cracking or uneven humming.

* Continuous abnormal rise in top oil temperature under normal load and cooling conditions.

* Oil spray from the conservator or explosion-proof tube.

* Severe oil leakage, with the oil level falling below the minimum visible mark on the oil gauge.

* Rapid darkening of oil color, even with carbon particles.

* Severe cracking, damage, or intense discharge on bushings.

* Fire or smoke from the transformer.

* Redness, melting, or fusing of connectors or leads.

* A personal injury accident near the transformer requiring power-off rescue.

Reminder: Regular inspection of these key points during daily operation can effectively prevent accidents.

What should be noted when adjusting the tap changer of an on-load tap-changing transformer?

On-load tap-changing transformers allow voltage adjustment under load. However, the following must be observed:

* Monitor oil level: Pay attention to oil level changes in the auxiliary tank.

* Record operations: Record each operation; maintenance is required when the cumulative number approaches the manufacturer's specified limit.

* Avoid simultaneous operation: Do not perform remote and local manual operations at the same time.

* Verify position: Ensure the tap position indicator is correct and the number is centered in the viewing window.

* Follow instructions: Adjustments must be authorized; do not adjust arbitrarily.

* Two-person operation: Two people should work together—one to operate, one to supervise.

* Keep gas protection active: The gas protection for the auxiliary tank must always be in service.

* Use momentary operation: When operating remotely, use short "inching" actions.

* Avoid frequent operation under overload: Do not adjust taps frequently during overload to prevent contact overheating.

* Follow sequence: For manual operation, strictly follow the instructions provided with the equipment.

How to handle a significant rise or drop in transformer oil level?

When oil level rises:

* First, check if the cooling system is operating normally, if the load has increased, or if the ambient temperature has risen.

* If the oil level exceeds the normal range due to temperature rise, contact a professional to drain some oil.

When oil level drops (or is no longer visible):

* Check for oil leaks, load reduction, or ambient temperature drop.

* If there is a major leak, switch to a backup transformer and schedule repairs.

* If the oil level is low due to environmental or load changes but no leak is found, contact a professional to refill to the standard level.

What tests are required before a newly installed or overhauled transformer is put into operation?

To ensure safe and reliable operation, the following tests are typically required:

* Insulating oil and bushing oil tests

* Dielectric loss angle (tanδ) measurement of windings and bushings

* Leakage current test

* Power frequency withstand voltage test

* DC resistance measurement (at all tap positions)

* Voltage ratio measurement and connection group check

* On-load tap-changer operation test

* Insulation resistance and absorption ratio measurement

*Switching impulse test: A newly installed transformer must undergo 5 full-voltage switching impulses; after major overhaul (winding replacement), 3 impulses are required before commissioning.

Our company provides technical support and on-site services for all the above tests.

What performance requirements does the transformer core have for silicon steel sheets?

Silicon steel sheets are the core material of the transformer core. Their main performance requirements include:

* Low iron loss: Reduces no-load loss; the primary indicator of silicon steel sheet quality.

* High magnetic flux density: Achieves high magnetization under strong magnetic fields, reducing core volume and weight.

* Smooth surface and uniform thickness: Improves core stacking factor.

* Good punchability: Easy to process into required shapes.

* Excellent insulation coating: The coating should have good adhesion and weldability, providing corrosion protection and improved punchability.

* No magnetic aging: Stable performance after long-term operation.

Our company's transformers use high-quality, high-permeability silicon steel sheets to effectively reduce no-load losses and noise.

What are the performance differences between copper and aluminum conductors in transformer windings?

Selection advice: For applications requiring frequent short-circuit impact or high reliability, copper windings are still the first choice. For weight-sensitive or cost-priority applications, aluminum windings have advantages.

Our company offers both copper and aluminum winding options for transformers.

What are the main categories of insulating materials used in transformers?

The reliability and service life of a transformer largely depend on the performance of its insulating materials. Common insulating materials fall into three categories:

* Gas insulation: e.g., air, SF₆, used in gas-insulated transformers.

* Liquid insulation: e.g., mineral oil, vegetable oil, synthetic esters, providing both insulation and cooling.

* Solid insulation: e.g., insulating paper, pressboard, corrugated board, epoxy resin, laminated wood/board, rubber, mica products.

Our company selects high-quality combinations of insulating materials based on product type and customer needs, ensuring a balance between safety and service life.