First, distribution transformer winding fault 1, short circuit between turns: refers to the short circuit fault caused by the insulation damage of the wire itself.
1) Signs: The temperature of the transformer's overheated oil increases; the current on the power supply side increases slightly; sometimes there is a buzzing sound in the oil and a buzzing sound; in severe cases, the oil pillow is injected.
2) Cause: Long-term overload damages the insulation between turns, and the winding is short-circuited by the short-circuit current of the transformer, causing vibration and deformation to damage the inter-turn insulation, and the oil level is lowered to expose the winding to the oil line. Breakdown: Atmospheric overvoltage intrusion damages åŒ insulation during lightning strikes, no defects are found during winding winding (causing burrs, poor wire bonding and incomplete wire insulation) or wire arrangement and transposition, winding crimping is incorrect, etc. The insulation between the turns is damaged.
3) Inspection test method: the appearance of the lifting body is checked, the insulation at the short circuit between the turns is black-focus; the DC resistance of the winding is measured, the three-phase resistance is unbalanced; the short-circuit phase resistance is small; 10%-20 is applied to the low-voltage side winding The rated voltage of % (in air) is tested for no-load, and if there is damage, it will smoke.
2. Winding grounding: Refers to the short circuit of the winding to the grounding part.
1) Signs: The oil quality deteriorates, and the grounding phase of the grounding phase drops for a long time and the fuse is burnt.
2) Cause: The lightning over-voltage and the over-voltage of the lightning cause the winding to be deformed by the impact of the short-circuit current, and the main insulation is aging, broken and broken; the dielectric strength of the transformer oil is reduced after the damp, the oil level is lowered or the insulation is aging;
3) Inspection test method: Use a shaker to measure the insulation resistance of the winding to the ground. If the resistance is zero or close to zero, it is the grounding phase. Lift the body to check for debris, insulation bushing between the winding and the iron core, insulation board, whether the cable is deformed or not. The oil is subjected to a simplified test (whether the breakdown voltage of the test oil is acceptable).
3. Phase-to-phase short circuit: The insulation between the winding phases is broken down to cause a short circuit. Please visit: Transmission and Distribution Equipment Network for more information
1) Signs: The oil temperature increases sharply, the oil pillows are injected, and the blown fuses are blown.
2) Cause: The main insulation aging edge is reduced; the transformer oil breakdown voltage is low; or caused by other fault expansion, such as the winding has a turn-to-turn short circuit or ground fault, due to the arc and the molten copper (aluminum) particles scattered Splashing causes the accident to spread and develop into a phase-to-phase short circuit.
3) Inspection method: the appearance of the lifting body is checked, the main insulation is burnt in the phase-to-phase short circuit; the insulation resistance is measured, the phase resistance is zero or close to zero; the DC resistance and transformation ratio of the winding are measured, and the factory value or The comparison of the previous measurement records can determine the damage of the windings.
4, winding and lead disconnection:
1) Signs: Arcing often occurs, causing oil to decompose and vaporize, sometimes causing phase-to-phase short circuits.
2) Causes: Mostly due to poor soldering inside the wires, overheating and melting or blown due to short circuit between turns, and winding breakage caused by short-circuit stress.
3) Inspection method: Check the core; use the bridge to measure whether the three-phase DC resistance is balanced.
Second, distribution transformer casing failure
1. Signs: casing damage, cracks, flashovers and oil spills.
2, the cause: external damage; the seal is not strict, the insulation is deteriorated by moisture; casing fouling is serious.
3. Inspection method: externally check the damage, crack and scale of the porcelain casing; use a shaker to check whether the insulation resistance between the porcelain casing and the ground meets the specified requirements.
Third, the distribution transformer tap changer The tap changer is in poor contact or the position is not correct, the contact surface is melted and burned, the phase contact discharge or each tap discharge.
1. Signs: The tap changer is partially overheated and burned.
2, the cause: switch structure and assembly defects, such as unreliable contact, spring pressure is not enough; contact overheating when short circuit; overvoltage breakdown; foreign objects in the transformer or contact dirt, insulation moisture.
3. Inspection method: Check the insulation resistance of the tap-changer to the ground with a shaker. If there is a fault, the resistance is very large. Measure the DC resistance of each tap and the factory value or the previous measurement record. If the difference is large, the indication is The head is faulty.
Fourth, distribution transformer core failure
1. Core damage:
1) Signs: oil temperature rises, oil quality deteriorates, and sound is abnormal.
2) Cause: The insulation between the core laminations is damaged; the iron core has multiple points of grounding; or the conductive material on the surface of the iron core may cause damage to the iron core. In addition, the core is missing; the iron core oil passage or the underside of the clamp is loose; if the fastening parts of the iron core are loose, abnormal sound will occur.
3) Inspection test method: Firstly, it is measured whether the insulation resistance of the core to the ground meets the specified requirements; then the body is lifted out for visual inspection; the insulation resistance between the sheets can also be measured by DC voltage and current method. In addition, do a no-load test to measure whether the no-load loss is too large.
2. The iron core grounding piece is broken:
1) Signs: A slight humming sound inside the transformer.
2) Cause: The assembly quality during manufacturing or maintenance is not good, such as the grounding piece is disconnected or not inserted, and the grounding is poor. ,
3) Inspection method: Check the grounding piece with the hanging core.
1) Signs: The temperature of the transformer's overheated oil increases; the current on the power supply side increases slightly; sometimes there is a buzzing sound in the oil and a buzzing sound; in severe cases, the oil pillow is injected.
2) Cause: Long-term overload damages the insulation between turns, and the winding is short-circuited by the short-circuit current of the transformer, causing vibration and deformation to damage the inter-turn insulation, and the oil level is lowered to expose the winding to the oil line. Breakdown: Atmospheric overvoltage intrusion damages åŒ insulation during lightning strikes, no defects are found during winding winding (causing burrs, poor wire bonding and incomplete wire insulation) or wire arrangement and transposition, winding crimping is incorrect, etc. The insulation between the turns is damaged.
3) Inspection test method: the appearance of the lifting body is checked, the insulation at the short circuit between the turns is black-focus; the DC resistance of the winding is measured, the three-phase resistance is unbalanced; the short-circuit phase resistance is small; 10%-20 is applied to the low-voltage side winding The rated voltage of % (in air) is tested for no-load, and if there is damage, it will smoke.
2. Winding grounding: Refers to the short circuit of the winding to the grounding part.
1) Signs: The oil quality deteriorates, and the grounding phase of the grounding phase drops for a long time and the fuse is burnt.
2) Cause: The lightning over-voltage and the over-voltage of the lightning cause the winding to be deformed by the impact of the short-circuit current, and the main insulation is aging, broken and broken; the dielectric strength of the transformer oil is reduced after the damp, the oil level is lowered or the insulation is aging;
3) Inspection test method: Use a shaker to measure the insulation resistance of the winding to the ground. If the resistance is zero or close to zero, it is the grounding phase. Lift the body to check for debris, insulation bushing between the winding and the iron core, insulation board, whether the cable is deformed or not. The oil is subjected to a simplified test (whether the breakdown voltage of the test oil is acceptable).
3. Phase-to-phase short circuit: The insulation between the winding phases is broken down to cause a short circuit. Please visit: Transmission and Distribution Equipment Network for more information
1) Signs: The oil temperature increases sharply, the oil pillows are injected, and the blown fuses are blown.
2) Cause: The main insulation aging edge is reduced; the transformer oil breakdown voltage is low; or caused by other fault expansion, such as the winding has a turn-to-turn short circuit or ground fault, due to the arc and the molten copper (aluminum) particles scattered Splashing causes the accident to spread and develop into a phase-to-phase short circuit.
3) Inspection method: the appearance of the lifting body is checked, the main insulation is burnt in the phase-to-phase short circuit; the insulation resistance is measured, the phase resistance is zero or close to zero; the DC resistance and transformation ratio of the winding are measured, and the factory value or The comparison of the previous measurement records can determine the damage of the windings.
4, winding and lead disconnection:
1) Signs: Arcing often occurs, causing oil to decompose and vaporize, sometimes causing phase-to-phase short circuits.
2) Causes: Mostly due to poor soldering inside the wires, overheating and melting or blown due to short circuit between turns, and winding breakage caused by short-circuit stress.
3) Inspection method: Check the core; use the bridge to measure whether the three-phase DC resistance is balanced.
Second, distribution transformer casing failure
1. Signs: casing damage, cracks, flashovers and oil spills.
2, the cause: external damage; the seal is not strict, the insulation is deteriorated by moisture; casing fouling is serious.
3. Inspection method: externally check the damage, crack and scale of the porcelain casing; use a shaker to check whether the insulation resistance between the porcelain casing and the ground meets the specified requirements.
Third, the distribution transformer tap changer The tap changer is in poor contact or the position is not correct, the contact surface is melted and burned, the phase contact discharge or each tap discharge.
1. Signs: The tap changer is partially overheated and burned.
2, the cause: switch structure and assembly defects, such as unreliable contact, spring pressure is not enough; contact overheating when short circuit; overvoltage breakdown; foreign objects in the transformer or contact dirt, insulation moisture.
3. Inspection method: Check the insulation resistance of the tap-changer to the ground with a shaker. If there is a fault, the resistance is very large. Measure the DC resistance of each tap and the factory value or the previous measurement record. If the difference is large, the indication is The head is faulty.
Fourth, distribution transformer core failure
1. Core damage:
1) Signs: oil temperature rises, oil quality deteriorates, and sound is abnormal.
2) Cause: The insulation between the core laminations is damaged; the iron core has multiple points of grounding; or the conductive material on the surface of the iron core may cause damage to the iron core. In addition, the core is missing; the iron core oil passage or the underside of the clamp is loose; if the fastening parts of the iron core are loose, abnormal sound will occur.
3) Inspection test method: Firstly, it is measured whether the insulation resistance of the core to the ground meets the specified requirements; then the body is lifted out for visual inspection; the insulation resistance between the sheets can also be measured by DC voltage and current method. In addition, do a no-load test to measure whether the no-load loss is too large.
2. The iron core grounding piece is broken:
1) Signs: A slight humming sound inside the transformer.
2) Cause: The assembly quality during manufacturing or maintenance is not good, such as the grounding piece is disconnected or not inserted, and the grounding is poor. ,
3) Inspection method: Check the grounding piece with the hanging core.
Using The Platform,Broadband Antenna,Three Wire Antenna
Mianyang Ouxun Information Industry Co., Ltd , https://www.ouxunantenna.com