Introduction To Tank Used In Transformer - Online Article

Utilities include WA the tank and the cover are manufactured of hot-rolled, unalloyed steel sheet and profile balks. Fine granular steel is used in transformers for low ambient temperatures.

Areas where strong eddy currents can be generated due to high currents, and where ordinary hot-rolled steel can become too warm, are made of non-magnetic (austenite) steel. Such areas are for example the surroundings if high current bushings and bushbars. The tanks are welded and manufactured in accordance with modern welding methods.

The tank has lifting lugs for lifting the transformer (fully-equipped transformer including oil) and at least four jacking points an the lower part if the tank for lifting by hydraulic jacks. For transport wheels there are fixing points at the bottom of the tank. The tank is provided with at least two earthing lugs made of stainless steel.

The connecting flanges of the coolers and the flanges for filling, draining, filtering and sampling valves are welded to the tank. Also the fixing brackets of cooler fans are welded to the tank. Usually the support of the oil conservator is fastened to the tank too. The transformer cover is fixed to the tank usually by means of a bolt joint using oil resistant rubber cork as the gasket. A gasket made of special rubber can also be used. The cover can also be fixed to the tank by welding. The welded seams are tighter and more reliable than bolted ones. They can be quite easily opened and rewelded.

The transformer cover is constructed so that no water pockets or other water collector points are formed. An air pipe is connected to the gas relay from all the turrets, flanges etc. where it is possible for gas pockets to develop.

wastewater, fuel, electricity, gas, and telecommunications systems. The basic components of utilities include supply and storage equipment, transmission lines, and the connections between these components. Utility components may be located above ground or underground, and rely on poles, grade level foundations, or soils for support.

Utilities commonly suffer earthquake damage for two reasons

  1. Above ground utility equipment, tanks, pipelines, and connections are often inadequately braced or inadequately secured to their foundation structures. Like buildings and other facilities, utilities tend to be designed for vertical gravity loads. As a result, the equipment anchorage and pipeline bracing may not be strong enough to carry the large lateral forces associated with earthquakes.
  2. Underground utility pipelines and connections are often too weak or inflexible to withstand earthquake ground movements and differential settlements, causing them to crack or fail. Materials that are too flexible, however, also cannot handle additional displacements from earthquake forces.

Types of Damages to Utilities

Typical types of utility damage are described below:

  • Supply equipment. Supply equipment such as electrical transformers, pumps, or generators are typically located on grade level foundations or elevated support structures. When this equipment is not supported or anchored properly it may topple or fall from its supports during an earthquake. Supply equipment mounted on separate foundations can also be damaged by differential settlements or movements between the foundations. Porcelain components of electrical transformers are brittle and can break during an earthquake.
  • Utility transmission lines. Utility transmission lines include pipes with joints for water, wastewater, fuel, gas, and electrical conduits that run underground or above grade level. Damage to above ground transmission lines typically occurs along unsupported line sections when lines crack, leak, or fail. Damage to underground transmission lines usually occurs in areas of soil failure where the line sections cannot withstand soil movements or differential settlements.
  • Connections. Damage to connections between utility pipeline sections and/or between utility transmission lines and equipment occur where the connections can not withstand soil movements or differential settlements.
  • Tank structures. Tank structures may be oriented vertically, horizontally, at grade, or elevated. Tall vertical tank structures or standpipes are often damaged by a combination of the structure's reactions to ground shaking and dynamic forces generated by water sloshing inside the tank. Tank foundation supports fail and denting of thin tank wall sections often result. The most serious type of vertical tank damage occurs when the tank walls crush near the base, triggering tank leakage or collapse. Horizontal tanks are often damaged when tanks are not securely anchored to the foundations. Elevated tank structures may be damaged due to buckling of the cross braces between the tank legs.

In addition to the types of damage listed above, damage to utilities can trigger secondary damages that affect the community at large. Leaking or broken utilities can cause water damage, fire or explosion. Since these systems are interconnected, a loss of one utility system (such as electrical power) can often lead to a loss of other systems.

Tank Construction

Tanks are fabricated from M.S. Sheet of best quality by electric welding. The design of the tank is such that the base and cover thickness is related to the size and weight of the finished products. A robust skid and weight of the finished product. A robust skid underbase is provided, and guid bars are located inside the tank to securely fix the core and windings assembly in position, and to prevent any movement during transportation. All tanks are pressure tested before leaving the fabrication department, the level of test pressure being dependent on the service voltage specified. When special test pressures, including negative pressures down to full vacuum are required, tanks are designed accordingly. All tanks for high voltage transformers which are subject to the oil degassing process are designed to withstand full vacuum. All the joints are gasketed to avoid leakage with the help of rubberised cork sheets, which can withstand high oil temperature and do not deteriorate nor contaminate oil in its contact. Pressed steel radiators are used to dissipate heat generated at rated load. For smaller ratings, radiators are directly welded to main tank, while for the bigger ratings detachable type radiators sre provided to facilitate transport and handling at site.

Fittings and Accessories

All the standard fittings; confirming to respective standards are provided on each transformer. In addtion to this the following optional accessories, where ever applicable, can be provided if ordered :

  • Oil Temperature Indicator.
  • Winding Temperature Indicator.
  • Double float Buchholz relay.
  • Magnetic Oil level guage.
  • Pressure relief valve.
  • Disconnecting chambers for cable box. Any other additional special fittings can be provided to suit individual requirement of customer.

Terminations

Terminals to suit Customer's requirements can be provided. Outdoor bushings are normally provided for the HV & LV terminals. HV outdoor bushings are supplied with arcing horns as standard. Air insulated and compound filled cable boxes, with or without disconnecting chambers, can be provided to suit customer's specification. The terminals of our transformers can be made suitable for heat shrinkable cable termination system.

Painting

Metal which has been pre-treated by means of shot/sand blasting to remove rust and welding scale, is throughly cleaned, and then a coat of zinc chromate primer paint is imediately applied to all external surfaces. This anticorrosive primer has rust inhibitive properties and excellent chemical resistance. Two coats of grey, weather enamel finish paint, which is highly resistant to chemicals and oil, are then applied.

Oil

All the Transformers are supplied with first filling of oil conforming to IS 335. Before filling, oil is heated, filtered and vacuum treated in filter machine to remove any foreign particles, moisture and air.

Testing

Before dispatch each & every transformer is subjected to all routine test as specified by IS. We have fully equipped test laboratory for conducting all routine tests and temperature rise test in accordance with IS-2026. Arrangement can also be made to carry out relevent type tests, if required, at recognised laboratories.

  • Safe
  • Reliable
  • Affordable
  • Computerized

Residential & Commercial ATS for Tank Testing

Test results are available on-site:  Our sophisticated testing technology can often evaluate the underground tank & system in 90 minutes or less.

Up against a tight deadline?  Don't worry! If necessary, we can dispatch our environmental testing personnel immediately after calling for an appointment.

We do not remove or repair tanks:  We are only in business of testing them.  This avoids any potential conflict of interest from performing both evaluation and repair/remediation work. 

Test methods:  We offer the Digital DME 2-D Test System, which is our preferred method of testing.  ATS also offers the Alert 1000/1050 tank test system which may be employed at certain locations.

Our test methods are superior to the competition: Learn more about our DME 2-D Test & our Alert 1000/1050 test & see for yourself.

Advantages of using ATS for Tank Testing

Distinguish leaks in vent/fill pipes from leaks in tanks:  Our computerized testing technology system will identify vent/fill pipe leaks from tank leaks. Other companies using tank tests without this feature may recommend removing a whole tank from the ground when only a minor inexpensive piping repair is required. 

State & Federal Certifications:  All our testing processes are federal and state approved test methods for evaluating underground tanks.  In addition, our company holds current licenses in several counties, states and cities.

Confused about tank testing?  See our Tank Testing options page which details our three most popular inspection services.

Uses & Advantage of Tanks

The Transformer Advantage is a precision temperature monitor for liquid immersed power and distribution transformers. It is rugged, fully electronic and field configurable. With Transformer Advantage, users can extend transformer life, utilize maximum capacity and reduce maintenance costs.

Seven models in the Advantage line offer a range of functions and configurations. All use an accurate and stable platinum temperature sensor (RTD) to precisely measure critical liquid temperatures. Setpoint relays can activate alarms or multiple stages of cooling at different temperatures. A sequencing function equalizes run time between cooling stages. The fan timer can exercise fans at a preset time each day. Seasonal setback is available on any setpoint relay. A frontpanel test mode quickly verifies cooling and alarm operation. The high currentrelay contacts can be configured fail-safe (close on a power fail) or fail as is.

The large alphanumeric display continually shows the selected transformer parameter. Front panel buttons scroll the display through other parameters and relay/alarm status. Peak and valley values for each channel are time stamped and stored in non-volatile memory. These are easily checked and reset by the operator from the front panel. A password-protected supervisor mode accesses all setup parameters. Initial setup can be done from the front panel or through the optional RS232/422/485 digital ports. Windows-based configuration software significantly speeds startup.

The Transformer Advantage is a cost-effective upgrade from analog gauges. It is designed to mount in the existing gauge location and on or in the control cabinet. Probe options fit most popular thermowells, or surface mount on units without wells. The Advantage has been conservatively designed and stress tested to provide years of trouble free service in the harshest environments. A variety of options tailor the Transformer Advantage to each application.

Simulated Winding Temperature: This is the traditional method for indicating transformer winding temperature. A heated thermowell, driven by a bushing CT, simulates the winding temperature rise above the oil temperature. This temperature rise is calibrated by the transformer manufacturer at full load. Performance is optimized for steady state or slowly changing loads. The simulated winding method is often used with digital gauges on existing transformers when a full load temperature rise (gradient) cannot be determined. One, two and three channel Advantage models support this method on new or operating transformers.

Calculated Winding Temperature: A newer method uses oil temperature and load current to calculate winding temperature. The Transformer Advantage analyzes transformer parameters to determine thermal time constants for the oil and windings. These time constants are changed dynamically based on load and cooling conditions. Rate of change information is also utilized in the Weschler CT algorithm to further improve the winding temperature accuracy. This is particularly important when operating above nameplate rating. Three Advantage models use the CT method for winding temperature indication.

Simulated Winding Models:

Advantage SC: The single channel Advantage SC directly measures one liquid temperature using either an RTD probe installed in a thermowell or a magnetic probe mounted on the side of the tank. The display prompt can be set to Top Oil, Fluid, Winding, HWinding, YWinding, XWinding, Ambient, or Bottom Oil. Winding temperature is simulated by using the RTD probe in a heated thermowell. Full scale temperature can be set to either 200°C or 250°C. During setup, the optional form B and form C setpoint relays are individually configured to activate at different values of the measured temperature. Up to eleven relays and one channel of analog output are available in the SC model.

Advantage DC: The Advantage DC provides two channels of temperature monitoring in a single unit. Any mix of thermowell probes and magnetic probes can be used. Each set-point relay can be configured to trigger on channel 1 or channel 2 temperature, time of day or a remote command. Hysteresis, non-alarm state and sensor fail response are also individually setable. One Advantage DC easily replaces the oil and winding gauges on an existing transformer. Three windings and one fluid temperature can be monitored with two DC units.

Advantage TC: The Advantage TC provides additional flexibility in transformer monitoring. Three identical channels can measure any combination of top oil, bottom oil, winding and ambient temperature. The Advantage TC can monitor oil and one or two winding temperatures. The ambient probe coupled to a setpoint relay can be used for a low temperature alarm or pump lockout. Three channels of analog output, with adjustable span, are available.

Calculated Winding Models

Advantage CT: The Advantage CT model directly measures transformer liquid temperature and transformer load current in one phase. Winding temperature is calculated from the measured current, liquid temperature and key transformer parameters. This calculation uses a proprietary algorithm based on recognized IEEE methods. An existing current transformer can be wired directly to the Advantage CT, or the clamp-on option can be ordered to avoid CT loop rewiring. With the 3CT option, currents in three phases are compared and the highest value used for the winding temperature calculation. The three channel analog output option can provide readback of oil temperature, winding temperature and load current.

Advantage CTX: The Advantage CTX adds an extra temperature channel to the capabilities of the Advantage CT. This channel is typically used to monitor ambient or bottom oil. The sophisticated winding temperature algorithm in all CT models provides different thermal profiles for natural, forced or directed fluid cooling. Many control and alarm schemes are possible with up to 9 form C or 6 form C and 5 form B relays.

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