MAINTENANCE & SERVICING OF TRANSFORMER
ECS also performs maintenance on transformers
A power transformer is most costly and essential equipment of an electrical transformer. So for getting high performance and long functional life of the transformer, it is desired to perform various maintenance activities. Not only that, a power transformer also requires various maintenance actions including measurement and testing of different parameters of the transformer. There are mainly two types of maintenance of transformer. We perform one group is in routine basis, and second group is as when required.
That means for getting smooth performance from a transformer we have to perform some maintenance actions in regular basis. Some other type of maintenance of transformer we perform as when they are required. But if one performs regular maintenance properly, he may not have any provision of performing emergency maintenance. The regular checking and maintenance of transformer is also known as condition maintenance.
Hence by proper condition maintenance one can avoid emergency and breakdown maintenance. That is why one technical personnel should mainly concentrate on condition maintenance. As 100% condition maintenance causes 0% breakdown of equipment. There are many different maintenance actions, to be performed on a power transformer. Some of them in yearly basis, some of them are monthly basis, some other are quarterly, some are half-yearly basis. These are mainly transformer maintenance action, which to be performed in 3 to 4 years interval.
TRANSFORMER TEST EQUIPMENT
- Fully automatic micro-controller operated
- Measure 3ph transformer connection to IEC 76.
- Identify group to IEC 76
- Measure ratio 10,000: 1 to IEC 76
- Measure PT/CT ratio to IEC 60044
- Measure excitation current
- Polarity mark check for 1 ph to IEC 60044
- Calculate ratio error to PRESET standard ratio
- 8 G memory: saves up to 10,000 groups
INTRODUCTION: The new style of Digital Insulation Resistance Tester is DIT913. It has fashionable design and improved electronic circuit, so that has more fully function, higher precision, easier operation.
The output testing voltage can be selected in 250V/500V/1000V/2500V for deferent measurement. Resistance range can touch 20Gꭥ. Alternating voltage also can be tested.
This tester apply for all kinds of electric equipment and insulation materials such as transformer, electromotor, cable, switch appliance, etc. It is a perfect electrical testing meter
This meter is designed in accordance with ICE publication 1010, pollution degree II and insulation category (over voltage category) II
- Low power consumed CMOS double integral A/D convertor IC, auto zero.
- 3-1⁄2 Digits LCD Display, the max reading is 1999.
- Data Hold with symbol
- LED indicating show high voltage is generated.
- Low battery indicated
- Output short current is over 1.5mA
- Range: 0-20Gꭥ, Auto Range
- Perfect circuit protect
- Size of LCD 67 x 28mm (Height of character is 20mm)
- Power: R6P(AA)(1.5V)6
- Size: 150 x 100 x 70mm
- Weight: 680g(including batteries)
- Working temperature: 0-400C relative humidity < 80%
- Storage temperature: -10-500C, relative humidity <85%
- Temperature to ensure precision: 230C ± 50C, relative humidity <75%
- DISPLAY -: 12.5mm LED
- POWER-:230V ± 15%, 50/60 Hz
- OPERATING TEMP-: 5° TO 45° C
- TEMP COEFFICIENT -: 50 P.P.M
- DUTY CYCLE -: 2 mins (100A) / 4 mins (50A) ON
- 6 mins OFF
FOR MEASURING VERY LOW RESISTANCE OF;
- CIRCUIT BREAKERS
- METALLURGICAL TESTING
The OC E-Series Liquid Dielectric Test Set are fully automated, digital dielectric system designed to reliably and accurately test the dielectric strength of insulating liquids. The controller is pre-programmed with test procedures to automatically perform ASTM D877, ASTM D1816 and IEC 156 specified tests, and includes an integrated control and data acquisition system. Data from standard tests is automatically stored in one of the 25 internal memory slots. After testing is complete, results can be downloaded to a computer using the RS232 port. There is also the option to add a printer with the ability to print the results directly.
The rugged, lightweight and portable design ensures years of safe and trouble-free operation in both the field and the factory. The OC E-Series automatically terminates high voltage upon sample breakdown, and the digital memory kilovoltmeter automatically records the breakdown voltage for each test sample. This product ranges includes models in 60kV AC.
• Preprogrammed with standard test profiles
• Easily upgradeable software as standards change
• Digital memory kilovoltmeter
• Internal Storage 25 most recent tests
• Single piece construction
- Multi-purpose compact design for use in the field and factory
- Easy integrated controller
- Sturdy and reliable for a long and trouble free life
- Report Generation with the optional printer or standard RS232 port for easy downloading
- Additional parameters allow users to enter additional test parameters such as temperature or viscosity.
- Test results can be stored internally, exported via RS232 or printed via optional onboard printer.
APPLICATION: Testing of insulating liquids in:
Tan Delta Bridge / Fully Automatic Precision Capacitance & Dissipation Factor Test Set (HCl2840)
Mode: HCl2840 (12kV)
Fully Automatic Precision Capacitance & Dissipation Bridge Is designed to measure dissipation(tan δ ) and capacitance (C) in many environment. Its can also be used as oil dissipation factor test set. Normally the accuracy of dissipation factor less than 0.0001, tested under the environment with very-low interference.
MAIN TEST OBJECT
- High voltage bushing
- Transformer winding
- Shunt reactor
- Instrument transformer (CT, VT, CVT)
- Capacitor of circuit breaker, surge arrester
- 12kV 200mA inner power source
- Standard capactior (CN)
- Power switch
- Sound & Light alarm
- Voltage & Current monitor
- Socket & Plugs
- High Voltage Test Equipment
- Liquid Tan Delta Measuring
Monthly Basis Maintenance of Transformer
Let us first discuss about the action to be taken on power transformer in monthly basis.
- The oil level in oil cap under silica gel breather must be checked in one month interval. If it is found the transformer oil inside the cup comes below the specified level, oil to be top up as per specified level.
- Breathing holes in silica gel breather should also be checked monthly and properly cleaned if required, for proper breathing action.
- If the transformer has oil filled bushing the oil level of transformer oil inside the bushing must be visually checked in the oil gage attached to those bushing. This action is to be done monthly basis.
If it is required, the oil to be filled in the bushing up to correct level. Oil filling to be done under shutdown condition.
Daily Basis Maintenance and Checking
There are three main things which to be checked on a power transformer in daily basis and they are:
- Reading of MOG (Magnetic Oil Gage) of main tank and conservator tank.
- Color of silica gel in breather.
- Leakage of oil from any point of a transformer.
In case of unsatisfactory oil level in the MOG, oil to be filled in transformer and also the transformer tank to be checked for oil leakage. If oil leakage is found take required action to plug the leakage. If silica gel becomes pinkish, it should be replaced.
Yearly Basis Transformer Maintenance Schedule
- The auto, remote, manual function of cooling system that means, oil pumps, air fans, and other items engaged in cooling system of transformer, along with their control circuit to be checked in the interval of one year. In the case of trouble, investigate control circuit and physical condition of pumps and fans.
- All the bushings of the transformer to be cleaned by soft cotton cloths yearly. During cleaning the bushing should be checked for cracking.
- Oil condition of OLTC to be examined in every year. For that, oil sample to be taken from drain valve of diverter tank, and this collected oil sample to be tested for dielectric strength (BDV) and moisture content (PPM). If BDV is low and PPM for moisture is found high compared to recommend values, the oil inside the OLTC to be replaced or filtered.
- Mechanical inspection of Buchholz relays to be carried out on yearly basis.
- All marshalling boxes to be cleaned from inside at least once in a year. All illumination, space heaters, to be checked whether they are functioning properly or not. If not, required maintenance action to be taken. All the terminal connections of control and relay wiring to be checked an tighten at least once in a year.
- All the relays, alarms and control switches along with their circuit, in R&C panel (Relay and Control Panel) and RTCC (Remote Tap Changer Control Panel) to be cleaned by appropriate cleaning agent.
- The pockets for OTI, WTI (Oil Temperature Indicator & Winding Temperature Indicator) on the transformer top cover to be checked and if required oil to be replenished.
- The proper function of Pressure Release Device and Buchholz relay must be checked annually. For that, trip contacts and alarm contacts of the said devices are shorted by a small piece of wire, and observe whether the concerned relays in remote panel are properly working or not.
- Insulation resistance and polarization index of transformer must be checked with battery operated megger of 5 KV range.
- Resistive value of earth connection and rizer must be measured annually with clamp on earth resistance meter.
- DGA or Dissolve Gas Analysis of transformer Oil should be performed, annually for 132 KV transformers, once in 2 years for the transformer below 132 KV transformer and in 2 years interval for the transformer above 132 KV transformer.
The Action to be taken once in 2 years:
- The calibration of OTI and WTI must be carried once in two years.
- Tan & delta; measurement of bushings of transformer also to be done once in two years.
Maintenance of Transformer on Half Yearly Basis
The transformer oil must be checked half yearly basis that means once in 6 months, for dielectric strength, water content, acidity, sludge content, flash point, DDA, IFT, resistivity for transformer oil. In case of distribution transformer, as they are operating light load condition all the time of day remaining peak hours, so there is no maintenance required.