Dry-Type Transformer Overhaul Procedures
I. Scope
These procedures specify the overhaul, maintenance cycles, items, and quality requirements for dry-type transformers in all low-voltage distribution rooms of the company.
These procedures apply to the maintenance and overhaul work of dry-type transformers in all low-voltage distribution rooms of the company.
II. Normative References
GB/T 10228-2008 Technical Parameters and Requirements for Dry-Type Power Transformers
GB 1094.1-1996 Power Transformers - Part 1: General Principles
GB 1094.2-1996 Power Transformers - Part 2: Temperature Rise
GB 1094.3-2003 Power Transformers - Part 3: Insulation Level and Insulation Tests
GB/T 1094.4-2005 Power Transformers - Part 4: Guidelines for Lightning Impulse and Switching Impulse Tests of Power Transformers and Reactors
GB 1094.5-2003 Power Transformers - Part 5: Short Circuit Withstand Capacity
GB/T 1094.10-2003 Power Transformers - Part 10: Sound Level Measurement
GB 1094.11-2007 Power Transformers - Part 11: Dry-Type Transformers
GB 311.1-1997 "Insulation Coordination of High Voltage Transmission and Transformation Equipment"
GB 5273-85
"Terminal Connections of Transformers, High Voltage Electrical Appliances and Bushings"
GB 4208-2008
"Degrees of Protection Provided by Enclosures"
GB/T 7354-2003
"Partial Discharge Measurement"
JB/T 10088-2004
"Sound Level of 6kV～500kV Power Transformers"
GB 6450
Dry-type Power Transformers
GB 147
High Voltage Electrical Construction and Acceptance Specifications
DL 408
Electrical Safety Work Regulations
DL/T 573
Power Transformer Maintenance Guidelines
DL/T 596
Preventive Testing Procedures for Power Equipment
JB/T 7631
Resistance Thermometers for Transformers
ZBK 4103
Technical Conditions for Three-phase Resin Insulated Dry-type Power Transformers
III. Equipment Technical Parameters
(1) Technical Parameters of Transformers in Each Branch Plant (Workshop)
Name
Item
109# Working Transformer 101#, 106# Working Transformer
104# Working Transformer
105#, 110# Working (Standby) Transformer
102#, 103#, 105#, 110#, 201# Working (Standby) Transformer
Apartment Building Working (Standby) Transformer
Air Separation Station Transformer
Model
SCB10--500/10
SCB10—1000/10
SCB10—1600/10
SCB10—2000/10
SCB10—2500/10
SCB10—630/10
SCB10-1250KVA
Capacity
500KVA
1000KVA
1600KVA
2000KVA
2500KVA
630KVA
1250KVA
Rated
Voltage
High
10000V
10000V
10000V 10000V 10000V 10000V 10000V
Low 400V 400V 400V 400V 400V 400V 400V
Rated
Current High 28.9A 57.7A 92.4A 115.5A 144.3A 36.37
Low 721.7A 1443.4A 2309.4A 2886.8A 3608.4A 909.3
Number of Phases 3 3 3 3 3 3 3
Frequency 50HZ 50HZ 50HZ 50HZ 50HZ 50HZ
Wiring Group Dyn11 Dyn11 Dyn11 Dyn11 Dyn11 Dyn11 Dyn11
Load Loss: 4.26KW 7.1KW 10.24KW 12.61KW 14.99KW 5.96KW
No-load Loss: 1.07KW 1.6KW 2.2KW 2.75KW 3.25KW 1.3KW
Impedance Voltage: 4% 6% 6% 6% 6%
Weight: 1750kg 2980kg 4000kg 4600kg 5900kg
Cooling Method: AN/AF AN/AF AN/AF AN/AF AN/AF AN/AF AN/AF
Manufacturer: XJ Transformer Co., Ltd. XJ Transformer Co., Ltd. XJ Transformer Co., Ltd. XJ Transformer Co., Ltd. Chint Transformer Co., Ltd. XJ Industrial Control Systems Co., Ltd.
Date of Manufacture: November 2009 2010.6 2010.5 2011.4 2010.5 2010.6
Quantity: 1 2 1 4 19 2 1
Name: Item
109# Working Transformer
101#, 106# Working Transformers
104# Working Transformer
105#, 110# Working (Standby) Transformers
102#, 103#, 105, 110#, 201# Working (Standby) Transformers
Apartment Building Working (Standby) Transformer
Air Separation Station Transformer
Model: SCB10--500/10
SCB10—1000/10
SCB10—1600/10
SCB10—2000/10
SCB10—2500/10
SCB10—630/10
SCB10-1250KVA
Capacity: Quantity
500KVA
1000KVA
1600KVA
2000KVA
2500KVA
630KVA
1250KVA
Rated
Voltage
10000V
10000V
10000V
10000V
10000V
10000V
10000V
400V
400V
400V
400V
400V
400V
400V
Rated
Current
28.9A
57.7A
92.4A
115.5A
144.3A
36.37
721.7A
1443.4A
2309.4A
2886.8A
3608.4A
909.3
Phase Number
Frequency Rate
50Hz
50Hz
50Hz
50Hz
50Hz
50Hz
50Hz
50Hz
Wiring Group
Dyn11
Dyn11
Dyn11
Dyn11
Dyn11
Dyn11
Load Loss
4.26KW
7.1KW
10.24KW
12.61KW
14.99KW
5.96KW No-Load Loss
1.07KW
1.6KW
2.2KW
2.75KW
3.25KW
1.3KW Impedance Voltage
4%
6%
6%
6%
6%
6% Quantity
1750kg
2980kg
4000kg
4600kg
5900kg
Cooling method
AN/AF
AN/AF
AN/AF
AN/AF
AN/AF
AN/AF
AN/AF
AN/AF
Manufacturer
Xuji Transformer Co., Ltd.
Xuji Transformer Co., Ltd.
Xuji Transformer Co., Ltd.
Xuji Transformer Co., Ltd.
Zhengtai Transformer Co., Ltd.
Xuji Industrial Control System Co., Ltd.
Date of manufacture
2009.11
2010.6
2010.5
2011.4
2010.5
2010.6
Quantity
19
（2）Technical parameters of substation transformer at No.115
Item Name No.1 transformer at No.2 transformer at No.2
Model SC9—50/10KV SC9—50/10KV
Capacity 50KVA 50KVA
Rated
Voltage High 10000V 10000V
Low 400V 400V
Rated
Current High 2.89A 2.89A
Low 72.2A 72.2A
Number of Phases Three-phase Three-phase
Frequency 50HZ 50HZ
Connection Group Yyno Yyno
Impedance Voltage 4.10% 4.03%
Weight 330kg 330kg
Cooling Method ON/AN ON/AN
Manufacturer Ningbo Epoxy Transformer Factory Ningbo Epoxy Transformer Factory
Date of Manufacture 2010.4 2010.4
Project Name
#1 Station Transformer
#2 Station Transformer
Model
SC9—50/10KV
SC9—50/10KV
Capacity
50KVA
50KVA
Rated
Electricity Voltage: 10000V 10000V 400V 400V Rated Current: 2.89A 2.89A 72.2A 72.2A Number of Phases: Three-phase Three-phase Frequency: 50Hz 50Hz Wiring Group: Yyno Yyno Impedance Voltage: 4.10% 4.03% Weight: 330kg 330kg Cooling Method: ON/AN ON/AN Manufacturer: Ningbo Epoxy Transformer Factory Ningbo Epoxy Transformer Factory Date of Manufacture: April 2010 April 2010 IV. Maintenance Cycle Daily Maintenance: Daily inspection of dry-type transformers. Minor Repair Cycle: Eliminate defects found during equipment operation. Major Overhaul Cycle: Annual major overhaul. V. Maintenance Items
1. Routine Maintenance Items:
(1) Observe that the voltage on the high-voltage side of the transformer is 10±5% KV, the current does not exceed the rated current value, and the three-phase current imbalance does not exceed ±5%.
(2) Observe that there are no signs of local overheating in any part of the transformer, and the temperature controller shows that the transformer temperature does not exceed 80℃. Under balanced three-phase load conditions, the three-phase temperatures should not differ significantly (usually phase B is slightly higher, with a difference of no more than 10℃ from the other two phases).
(3) Pay attention to the sound of the transformer during operation. When the transformer is running normally, there is generally a uniform "humming" electromagnetic sound. The sound should not be too loud, and there should be no abnormal noise.
(4) Check that the transformer is fixed stably and firmly, without tilting, local deformation, or vibration, and that all bolts are secure.
(5) Check that the transformer casing is intact, all connections are secure, and the casing is not damaged.
(6) Check that the transformer environment is clean, free of water accumulation and items that may hinder safe operation.
(7) The transformer must have good ventilation. (8) Check the dry-type transformer fan for severe vibration, abnormal noise, or failure to rotate.
(10) When the transformer temperature exceeds 80℃, confirm the fan is running. If the temperature gradually rises after the fan starts, check the load size and three-phase balance, and take appropriate emergency measures.
(11) In case of drastic weather changes, conduct special inspections on the indoor transformer:
a. After thunderstorms: Check for discharge sounds and traces in all parts.
b. In extremely cold or hot weather: Check the temperature change of the transformer body.
(12) Under overload conditions, check the transformer every half hour and record the overload value, time, temperature, etc., in the operation logbook.
(13) All inspection items should be recorded in detail, and defects should be eliminated promptly.
2. Minor Repair Items:
(1) Check that the transformer grounding device is intact; observe that the transformer lead wire position is normal, the support is firm, and the lead wire insulation is good.
(3) Check the wiring and tighten any loose bolts. (4) Inspect the ventilation and heat dissipation system and clean the dust.
(5) Repair the deformed transformer casing and nameplate.
(6) Inspect the neutral point grounding system and tighten loose bolts.
(7) Tighten the fixing bolts of the voltage regulating connecting plate.
3. Overhaul Items:
(1) Transformer dust removal.
(2) Inspect the iron core.
(3) Inspect the coils.
(4) Inspect the insulators.
(5) Inspect the incoming and outgoing leads.
(6) Inspect all insulating components, fasteners, and connectors.
(7) Transformer high-temperature protection test.
(8) Preventive test of dry-type transformer.
(9) Inspect the ventilation and heat dissipation system.
VI. Overhaul Process and Quality Standards
Item Overhaul Process Quality Standard
1 Transformer Dust Removal Clean the transformer iron core, coil gaps, and fan dust with compressed air. Surface free of dust and impurities
2. Inspect the Iron Core
a) Check if the iron core is flat, if the insulating varnish has peeled off, and the tightness of the laminations.
b) Check the tightness of the upper and lower clamps, square iron, and pressure plates of the iron core, and tighten each bolt of the clamps, square iron, and pressure plates with a wrench.
c) Measure the insulation resistance of the iron core to the clamps and ground using a 2500V insulation resistance meter.
d) Tighten the through bolts of the upper and lower iron cores with a special wrench and measure the insulation resistance of the through bolts to the iron core and ground using a 2500V insulation resistance meter.
a) The iron core should be flat, with no peeling of the insulating varnish, and the laminations should be tightly stacked. The silicon steel sheets on the sides should not be warped or wavy. All surfaces of the iron core should be free of dust and impurities, and free of rust and corrosion. There should be no short circuits or overlaps between the laminations, and the joint gaps should meet the requirements.
b) Bolts are tightened securely; the positive and negative pressure pins and locking nuts on the clamps are not loose, and there is good contact with the insulating washers without any signs of discharge burns.
c) The insulation resistance of the core to the clamps and ground is ≥5MΩ.
d) The through bolts are tightened securely; the insulation resistance of the through bolts to the core and ground is ≥5MΩ.
3. Coil Inspection
a) Check the coil deformation and insulation for integrity.
b) Check the air duct between the high-voltage and low-voltage coils.
