What Are You Looking For?
During the normal operation of power transformers, it is crucial to ensure that the transformer core has a single reliable grounding point. If the core is not grounded, it may develop a floating potential, leading to intermittent ground breakdown discharge. A single-point grounding effectively eliminates this floating potential. However, if the core is grounded at multiple points, a circulating current may form between the grounding points, potentially causing core overheating faults. In severe cases, this could damage the transformer, requiring the replacement of silicon steel sheets for repair. Therefore, the transformer core must be grounded at only one point.
The gas relay primarily protects transformers against the following faults:
When the main transformer cooler malfunctions, the following actions should be taken:
The following conditions must be met to ensure safe parallel operation of transformers; otherwise, circulating currents or short circuits may occur:
Abnormal transformer noise may be caused by the following:
Tap changer adjustments are prohibited under the following conditions:
Transformer nameplate ratings include the following:
Current source inverters require larger transformer capacities because the input-side power factor is, at most, equal to the power factor of the load's asynchronous motor. Compared to voltage source inverters, the rated capacity is significantly higher.
The transformer’s capacity is mainly related to heat generation, with the core selection determined by voltage and conductor selection influenced by current. Additionally, the rated capacity is constrained by permissible temperature rise.
To enhance transformer efficiency, the following methods can be adopted:
High energy-consuming distribution transformers (e.g., SJ, SJL, SL7, S7 series) have higher iron and copper losses than S9 series transformers. Replacing them with new-generation transformers (e.g., S10, S11 series, or amorphous alloy transformers) can significantly improve energy conversion efficiency and save electricity.
Eddy currents are induced currents generated within a solid conductor when alternating current passes through it, producing an alternating magnetic field around it. Eddy currents waste energy, reduce equipment efficiency, and cause overheating, which can severely impact equipment performance.
Transformer instantaneous protection must avoid low-voltage side short-circuit currents to ensure the selectivity of relay protection. Failure to avoid maximum short-circuit currents on the low-voltage side may extend the protection zone to the low-voltage outgoing lines, compromising selectivity.
The neutral points of two parallel transformers must not be simultaneously grounded to avoid issues with zero-sequence current and voltage protection coordination. Partial neutral point grounding in transformers can limit ground fault current levels and enhance the sensitivity of zero-sequence current protection.
Newly installed or overhauled transformers must undergo energization testing before commissioning to verify whether the insulation can withstand rated voltage and operational overvoltages. Additionally, the test evaluates the mechanical strength of the transformer and the impact of magnetizing inrush current on relay protection.
