Winding dc resistance test objects, including casing conductive part, fuses, winding and tap-changer the whole circuit, therefore the unusual situation of winding dc resistance and the structure of the above parts and manufacturing, maintenance links, analysis and deal with the defects need to know about casing structure of conductive sealing head, fuses and winding connection mode and manufacture process, the structure and movement theory of tap-changer and so on, combined with a variety of test data, a comprehensive analysis and judgment,

Winding dc resistance of the field measurement data, and the historical data, especially compare the factory test data or transfer the test data, as a result of the winding temperature will affect the measurement result, therefore, need to be converted to the measured data of two the same temperature, then compare,

Abnormal winding dc resistance is usually divided into two cases:

The first case: the same temperature, each phase winding dc resistance of the initial value differences often;

The second case: the same temperature, the phase winding of the differences between each other often,

Whether it's the kind of situation, for maintenance and repair personnel, need combined with the characteristics of the test data, and related information, determine the cause of the abnormal data, finding defects, and repair,

With tap-changer winding, loop connection link is more, easy to appear problem, this chapter mainly illustrates,

The lack of information collection:

For low voltage winding without tap-changer, maintenance staff should consult the transformer factory specifications, determine the connection mode of winding and fuses, when necessary to transformer oil under the hand hole, open the hand hole check whether the winding connection with wire is loose,

For high voltage winding with on-load tap-changer, conductive circuit of link is more, the screening of fault point is relatively is more complex, the maintenance staff should collect information as much as possible, auxiliary determine the cause of the defects, should collect information including:

1, winding manufacturing plants and casing pipe symbol, the structure of the conductive sealing head;

2, if the loop contains a load switch, should check the load switch factory name and switch model, check the load switch number, ask operators has a load switch current regulating tap scope;

3, if the loop contains no load switch, should check the no load switch factory name and switch model, consult the factory instructions book, determine the structure of the switch;

4, maintenance records, recent involving casing, load or no load switch maintenance work;

5, refer to patrol record, a recent infrared imager detect joint overheating defects;

6, consult the transformer factory specifications, determine the winding and wire connection way;

Defect cause analysis:

1, without tap-changer winding dc resistance test,

Without tap-changer winding electric circuit mainly by the winding, wire and wire terminals, wiring board commonly used between the winding and lead docking, bolt fastening connection, with the method of conductive contact area is large, reliable connection,

Once appear, a phase of low voltage winding is unusual, maintenance staff should first check whether the terminal is loose or craze, if the terminal is normal, and so is likely to be winding wire connection plate poor contact, from oil to low voltage wiring hand hole when necessary, open the hand hole cover plate, check the connection condition of winding and fuses,

2, tap-changer high-voltage winding dc resistance test,

Structural components in this case, a conductive circuit is more complex, containing winding, fuses, tap-changer and bushing conductive sealing head, terminal blocks, etc., among them, tap-changer and bushing structure of conductive sealing head is the most complex, also often appear to touch bad, lead to the winding dc resistance value exceeds bid,

When winding dc resistance abnormal defect occurs, often appear the following 8 defect characteristics of each type of defect characteristics corresponding to one or more causes,

1, casing of conductive sealing head poor contact, in this case, the defect phenomenon should have the following characteristics:

(1) in all tap position, a phase winding dc resistance value are obvious;

(2) the casing of the conductive sealing head structure is more complex, prone to the condition of the poor contact,

2, zero casing conductive sealing head poor contact, in this case, the defect phenomenon should have the following characteristics:

(1) in all tap positions, the three-phase winding dc resistance values are significantly larger;

(2) zero casing of conductive sealing head structure is more complex, prone to the condition of the poor contact,

3, switch dc resistance caused by the abnormal structure defect phenomenon should have the following characteristics:

(1) the dc resistance test data is not stable, differential, and

(2) the switch structure is relatively complex, but often part of the problem is mainly contact group and panel, electrical connection part of the contact group and contact group contact with panel parts prone to poor contact, cause the contact resistance or dc resistance,

4, switch singular contact or dual contactor poor contact, resulting in abnormal dc resistance, in this case, the defect phenomenon should have the following characteristics:

(1) in the odd tapping position (or even tapping location) on winding dc resistance numerical integral slants big, but in number accidentally tap position (position or an odd number of points) on the normal value;

5, select the switch contact abnormal dc resistance, which is usually caused by poor contact, select switch is mainly related to the connection problem of lead and switch, switch contact and contact problem of contact, the two question is easy to cause poor contact, dc resistance paint, in this case, the defect phenomenon should have the following characteristics:

(1) in a certain fixed tap positions, the winding dc resistance is big, in other positions, numerical qualified;

(2) if it is positive and negative pressure regulating mode, half the corresponding points on the pick up location at the same time, the phenomenon of large,

6, polarity switch dc resistance anomalies caused by poor contact, in this case, the defect phenomenon should have the following characteristics:

(1) the positive and negative voltage regulation of load switch, sits than one and a half and half OuZhi resistance data OuZhi resistance whole slants big, differential is stable;

(2) the thickness of on-load voltage regulator switch, the setting location and adjacent position differential change is bigger, compared with the historical data as a whole is larger;

7, fuses and winding abnormal situation caused by abnormal dc resistance in this case, the defect phenomenon should have the following characteristics:

(1) a phase winding large whole, and the differential uniformity;

(2) the photograph casing structure through inspection tighten in place and well connected, is measured at the pin head directly to pick up the test line, dc resistance still slants big, and the differential uniformity;

(3) by hand shaking, lead to test again, winding dc resistance data may change significantly;

8, no-load tap-changer dc resistance anomalies caused by poor contact in this case, the defect phenomenon should have the following characteristics:

(1) conductive loop contains no-load tap-changer;

(2) a phase winding dc resistance is larger;

(3) the no-load tap-changer position indicator display position is not straight;