Medium and Large Power Transformers

Arya Transfo Ghodrat Co. a subsidiary company of the Arya Transfo Group was established by a very large investment in order to manufacture a variety of power transformers. This company manufactures products with high quality and in-line with customer requirements. Manufacturing processes utilise modern and full-automatic machinery, advanced workshop facilities and equipment, the latest know-how, advanced software design, experienced-knowledgeable engineers, based on high quality raw materials.

 

 

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Phase shifting transformers

 

Phase Shifting Transformers

Today's large electrical high-voltage transmission systems have to provide reliable and efficient electrical energy to the customer. Due to de-regulation of the market, existing systems are often stressed to the limit. According to the laws of physics, power will flow through the system using the path with the lowest impedance. Technically and economically, this is not always the most optimal path. To ensure an optimal and reliable operation of the grid, the need for power flow control becomes evident.

Applications

The use of phase shifting transformers (PSTs) can help to manage power flow problems resulting from complex parallel transmission paths and system inter-ties by controlling the real power flow. The variation of the in-phase voltage magnitude controls the reactive power flow through a line, whereas the phase angle variation controls the real power flow.

PSTs can be built to provide a discrete phase angle shift or continuous variable phase angle shift. Some designs allow for magnitude as well as phase angle control. PSTs can be manufactured with many different winding configurations, depending on the rated voltage, the power throughput, the maximum required phase angle and whether or not voltage control is required. Discrete PSTs provide settings for a plus-or-minus fixed degree value and zero shift. If a variable phase-shift is desired, an OLTC will be installed. OLTCs are used to provide several tap positions for in principle any desired phase angle range.

 Basic principle

When power flows between two systems, there is a voltage drop and a phase shift between the source and the load that depends upon the magnitude and power factor of the load current. If the systems are connected together with two or more parallel lines, any difference in the individual line impedances will cause unbalanced loading of the lines. By installing a PST in one of the parallel lines, an additional voltage phase angle increase or decrease can be introduced in this line. This additional phase angle will bring the power flow between the parallel lines more in balance.  

How a PST is designed strongly depends on the throughput power in combination with the required phase angle, the system voltage and the system short circuit power. In general, PSTs can be designed as a single core or two core design in one or more tanks. PSTs can have a direct or indirect regulation.

700 MVA, 240kV , ±30º in ±16 steps PST

 The required phase angle and impedance of the PST is normally based on a secure system study. Based on this study, the most optimal PST design solution can be defined in cooperation with the PST manufacturer.

The figure shows a circuit with indirect regulation with an  intermediate circuit arrangement. It illustrates very clearly how the phase-angle between the voltages of the source and load systems can be varied by the OLTC position. Various other circuit arrangements have been implemented.

Circuit diagram, winding connections and phasor diagram of a two tank, two core design phase shifting transformer.

Benefits

  • Improved operational performance and grid reliability.
  • Energy savings by optimizing the power flow in the electrical system.
  • Dramatically lower costs than most FACTs devices.
  • Reliable, long lasting power transformers technology.
Power plant step-up transformers

 

The power plant transformers are one of the most important parts of energy networks. These transformers step up the output voltage range from generators to a higher level and perform a role as the conveyer of energy from generators to the power transmission line.
Considering transportation limits, Arya Transfo Ghodrat Co. is able to manufacture a variety of power plant transformers for thermal power plants, combined cycle, water, wind, etc. in 3 phase or single phase, based on customer requirements.
Arya Transfo Ghodrat Co. is able to produce 3 phase power plant transformers up to 420 kV and 550 MVA and also in single phase up to 420 kV and 300 MVA.

Shunt reactors

Shunt reactors are vital parts for the efficient operation of long HV power transmission lines. These devices compensate the capacitive load generated in the power lines, in order to avoid non-controlled voltage rise, especially on lightly loaded lines. The simple design and robust build-up make shunt reactors the most cost efficient means to compensate the capacitive load of high voltage lines.

Reactors can be manufactured as gapped core design or shielded core (air core). Large gapped core reactors are typically built as a 5-limb design. The smaller units are more typically manufactured as a 3-limb design. The choice between a 3-limb or 5-limb design may also be determined by the zero sequence requirements of the system.

In some cases a system requires a more flexible control of reactive power. For these applications, a controllable Shunt reactor with an on-load tap-changer can be an optimal solution. The maximum regulating range (MVAR/step) is manly determined by the step capacity of the tap changer and the maximum allowable transient voltage across the regulating winding and tap changer contacts.  

Shunt reactors provide the network operator with more flexibility for controlling the power flow and voltage profile. To achieve this purpose, shunt reactors with or without  on-load tap-changers can be designed and manufactured in Arya-Transfo Co., in cooperation with ROYAL SMIT TRANSFORMERS, depending upon the wishes of the customer.

Benefits

Shunt reactors are used for various areas of application:

  • Compensation of capacitive power of transmission lines, in particular in networks that are lightly loaded.
  • Reduction of system-frequency over voltages when a sudden load drop occurs.
  • Improvement of the voltage stability and efficiency of energy transmission.
  • Reliable, long lasting power transformers technology.

 

Advantages Of Variable Shunt Reactors

Improved voltage profile

Regulated network adjusts and improves voltage quality

Complying with the permissible voltage band

Reducing line losses

Reduction of system costs and required installation area

Higher number of operations with on-load tap changer regulated shunt reactors compared with switch mode operation of conventional shunt reactors through circuit breaker.

50-120MVAR (in 12 steps), 135kV Variable Shunt Reactor Active Part made by Royal SMIT Transformers.