1. When Cannot the Transformer On-Load Tap-Changing Device Adjust Voltage?
The on-load tap-changing device is a key component to ensure the stable voltage output of transformers such as 33kv distribution transformer and 2500 kva 3 phase transformer. However, in the following situations, voltage adjustment must be stopped to avoid equipment damage or safety accidents:
Unqualified withstand voltage of the on-load tap-changing device: If the withstand voltage test fails, it indicates that the insulation performance is defective. Forcing voltage adjustment may lead to insulation breakdown. This is a mandatory pre-inspection item for 2500 kva 3 phase transformer used in industrial scenarios.
Transformer load exceeds regulations: When the load exceeds the limit specified in the on-site operation regulations or manufacturer's standards, voltage adjustment will increase the burden on the tap-changer. For example, the 33kv distribution transformer in urban distribution networks must not adjust voltage when overloaded.
Exceeding the specified number of adjustments: Each tap-changer has a limited service life. Excessive operations will accelerate wear. JINSHANMEN TECHNOLOGY reminds that the 33kv distribution transformer should strictly record the adjustment times.
Frequent signals from gas protection of the tap-changing device: Frequent gas signals indicate potential internal faults such as oil decomposition, and voltage adjustment should be suspended for inspection.
Abnormal tap-changing device or no oil in the oil level gauge: Abnormal phenomena such as stuck switches or oil shortage will affect the insulation and arc-extinguishing performance, and operation is strictly prohibited.
2. Why Focus on Checking On-Load Tap-Changing Tank Oil Level and Operation Records During Operation?
For transformers equipped with on-load tap-changers, especially 33kv distribution transformer and 2500 kva 3 phase transformer in key power supply scenarios, checking oil level and operation records is crucial for safe operation:
Oil level monitoring significance: The on-load tap-changing tank is not connected to the main tank, so the oil level is greatly affected by ambient temperature. The tap-changer operates under rated voltage and needs to cut off the parallel branch current during adjustment. Sufficient oil quantity (reaching the marked position) is the key to ensuring insulation and arc-extinguishing. The breakdown voltage of the oil must not be less than 25kV. For the 2500 kva 3 phase transformer used in data centers, oil level deviation may cause equipment downtime.
Significance of operation record statistics: The operation times directly relate to the maintenance cycle. JINSHANMEN TECHNOLOGY recommends that the tap-changer of 33kv distribution transformer should be overhauled after 5,000 operations; if the contact wear is severe (thickness less than 7mm), it should be replaced; and a major overhaul is mandatory after 10,000 operations. The selection switch has high durability, and the first inspection can be carried out after 10,000 operations.
3. What Are the Operation Modes of On-Load Tap-Changer?
The on-load tap-changers of 33kv distribution transformer and 2500 kva 3 phase transformer produced by JINSHANMEN TECHNOLOGY adopt two operation modes: local control and remote control, to adapt to different operation scenarios:
Local control: Operated in the on-site on-load tap-changing control box, including electric and manual operations. Manual operation is mainly used for maintenance personnel to debug the tap-changer during overhaul; electric operation is used as a backup when remote control fails. For example, during the maintenance of 2500 kva 3 phase transformer in industrial parks, local manual operation is usually used.
Remote control: Mainly used by operators to adjust the tap position during the operation of the transformer, which improves the operation efficiency. The adjustment principle is: if the low-voltage bus voltage is high, adjust the high-voltage side tap switch to the upper gear (high-grade voltage); if it is low, adjust it down. The 33kv distribution transformer in urban power grids often uses remote control to realize automatic voltage regulation.
4. What to Do If the Electric Mechanism of On-Load Tap-Changing Device Fails During Operation?
When the electric mechanism of the on-load tap-changer of 33kv distribution transformer or 2500 kva 3 phase transformer fails, manual voltage regulation can be adopted as an emergency measure. JINSHANMEN TECHNOLOGY reminds to follow the following steps:
First, cut off the automatic control voltage regulation power supply to avoid misoperation of the electric mechanism during manual operation.
Use a dedicated handle to adjust the voltage. During the operation, refer to the on-site operation regulations (in accordance with the manufacturer's requirements) and the indication position of the tap switch to accurately adjust to the required position.
After the adjustment is completed, check the voltage output status and record the operation in detail. Arrange for professional personnel to repair the electric mechanism in a timely manner to restore the automatic regulation function.
Bonus: Difference Between Adjusting High-Voltage and Medium-Voltage Taps for Three-Winding Transformers
Some three-winding transformers (including partial 33kv distribution transformer and 2500 kva 3 phase transformer) are equipped with tap switches on both high-voltage and medium-voltage sides. The adjustment effects are quite different:
High-voltage side tap adjustment: Changing the tap position of the high-voltage side can simultaneously adjust the voltage of the medium-voltage and low-voltage sides. It is suitable for scenarios where the system voltage or load changes and both sides need voltage adjustment.
Medium-voltage side tap adjustment: Only the medium-voltage side voltage can be changed, and the low-voltage side voltage is not affected. It is applicable when the low-voltage side needs to be adjusted while the medium-voltage side needs to maintain the original voltage (at this time, the high-voltage side tap needs to be adjusted simultaneously).
About JINSHANMEN TECHNOLOGY CO., LTD
JINSHANMEN TECHNOLOGY CO., LTD is dedicated to delivering high-reliability transmission and distribution equipment solutions backed by years of R&D and production expertise. Our product portfolio covers oil-immersed, dry-type, three-dimensional coiled, mining explosion-proof, amorphous alloy, and on-load capacity-regulating transformers, as well as prefabricated substations and high-low voltage switchgear. Highlight products like 33kv distribution transformer and 2500 kva 3 phase transformer stand out for their stable on-load tap-changing performance, widely serving urban distribution networks, industrial parks, and data centers. With a strict quality control system and responsive after-sales service, we support custom solutions and technical consulting-reach out to partner with us for your equipment needs.