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Analysis of transformer fault and application of transformer protection device

First, the transformer failure analysis

          1, the voltage rise when there is a slight discharge sound. Cause of the malfunction: Grounding piece fracture; Treatment method: Remove the body to check and repair the grounding piece. 

          2, coil insulation resistance decreased. Failure reason: coil damp; Treatment: the coil for drying. 

          3, core sound is not normal. Failure reasons: (1), the iron core or under the clamp loose pieces (2), iron core loose parts loose; Treatment: (1), the free end of the cardboard plug pressed (2), check tight Firmware is fastened. 

          4, gas relay signal circuit action. Fault reasons: (1), inter-core insulation damage (2) through the core bolt insulation damage (3), the core grounding method incorrectly constitute a short circuit. Handling methods: (1). Remove the body, check and repair insulation damage between the core pieces (2) Replace or repair the core bolt (3), change the grounding method 

          5, the gas relay trip circuit action. Fault reasons: (1), the coil turn to turn short circuit (2), coil breakage (3), the coil to the ground breakdown (4), the coil line between the short circuit. Approach: hanging out of the body to conduct a comprehensive inspection, repair damaged parts, eliminate the fault point 

          6, the deterioration of oil insulation. Fault causes: (1), transformer internal fault (2), oil impurities in water exceeded. Treatment: (1), hanging body to check (2), filter or replace the insulating oil. 

          7, casing breakdown on the ground. Fault reason: porcelain surface dirty or cracked. Approach: clean or replace the casing. 

          8, discharge between the casing. Reason for the malfunction: there is debris between the casing. Approach: Check and clean the debris between the casing. 

          9, tap changer contact surface burns. Failure reasons: Deconstruction and assembly defects such as contact is not reliable \ The spring pressure is not enough. Approach: Check and adjust the tap-changer 

          10, tap the contact discharge or tap the discharge. Fault causes: over-voltage effect, the transformer internal dust or insulation damp. Approach: hanging core inspection, cleaning the dust inside the transformer.

Second, how to avoid the transformer in the above types of failures caused by the loss? 

          Then we need to use transformer protection devices to ensure the continuous operation of the power system security, transformer protection devices that have? What do they do? 

          Gas protection . Used to protect the internal transformer fault, when the transformer internal short circuit fault occurs, the oil produced by decomposition or when the transformer oil level decreases, gas protection should be action. 

          Longitudinal differential protection or current instantaneous protection . Used to protect the transformer inside and lead casing failure. Protection against transformer winding and lead-out multi-phase short-circuit, high-current grounding system side winding and lead-out single-phase ground short circuit and winding inter-turn short circuit. 

          Overcurrent protection. Used to protect the transformer internal and external fault, as a (longitudinal) differential protection or current protection against back-up protection. 

          Overload protection. Used to prevent the transformer symmetrical overload, so the protection device only in a phase of the circuit. 

          Zero sequence current protection. Protection of Zero Sequence Current for Transformer External Grounding Short Circuit in Large Current Earthed System. 

          Overexcitation protection. Over-excitation protection of over-excitation of transformer. 

          Temperature protection. The upper transformer oil temperature monitoring does not exceed the specified value (usually 85 ℃). When the oil temperature is exceeded, the temperature signal activates a signal or automatically turns on the transformer cooling fan.

 

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