India is one of the leading transformer manufacturing countries in the world. The easy availability of raw materials, cheap labor compared to developed nations, and qualified technical manpower has led India to emerge as one of the global leaders in transformer manufacturing. Transformer manufacturing industry in India is a mature industry and is more than five decades old. The industry has the capability to develop transformers of all kinds – instrument transformers, distribution transformers and power transformers. Transformers manufactured in India are considered to be of high quality and is therefore preferred by buyers from across the globe. In addition to quality, the prices of transformers manufactured in India are lower which provides it a competitive edge in the global marketplace and has led to a considerable growth of the industry in the past few years. Today, transformers manufactured in India are not just used in the domestic market, but are exported to several countries in Africa, Asia, the Gulf region and the European Union.


The transformer manufacturing industry in India is highly fragmented. There are more than 500 transformer manufacturers in India that includes large global players, national players and small regional and local brands. The focus of large global players is concentrated in the power transformers segment that includes transformers of 400 KV and above. National players are focused on distribution transformers while the small independent manufacturers focus their energies primarily in instrument transformers.

According to a report in Electrical India, a leading power magazine in India, the size of the Indian transformer manufacturing industry is estimated to be approximately USD 2 billion. Of this, distribution transformers are estimated to contribute around 50 percent, followed by power transformers that constitute 40 percent of the market. Instrument transformers comprise around 10 percent of the market. The industry has shown steady growth of around 4 percent, year-on-year and is expected to cross USD 5 billion by 2040.

Industry experts feel that the growth of the transformer manufacturing industry in India will primarily be driven by the domestic market. Several recent government of India initiatives that envisage providing electricity to every household in the country will necessitate the need for transformers. In addition to domestic consumers, the growth of the industry due to government initiatives like ‘Make in India’ will result in robust growth of the industrial sector which will drive power demand. It is no secret that for the success of every industry, uninterrupted power supply is a key ingredient. Therefore to meet the growing needs of the industry, significant thrust will be put on power generation, transmission and distribution. In all these key areas, transformers play an important role. So, automatically, there will be a huge spurt in the demand for transformers in the coming years in India.

Globally, too the market for electrical transformers is expected to grow. Countries in Africa are witnessing massive infrastructure spends and power is a core component of infrastructure development. Without power, no infrastructure can be developed. It is critical for economic growth. The domestic industry in most of these countries in Africa is at a very nascent stage. They do not have the technology and infrastructure to manufacture transformers locally. Most of these countries rely on imports from other countries to meet their transformer demands.

Current transformers are a family of instrument transformers that are used for stepping down current in electrical systems and electrical grids. The primary function of a current transformer is to produce proportional alternate current in its secondary terminal compared to primary terminal. There are several defined ratios depending on the system voltage. Current transformers are integral components for measurement of current in electrical systems.

Current transformers are further categorized into various types depending on their make and usage. These include Live Tank Current Transformer, Dead Tank Current Transformer, Resin Cast Current Transformer and Low Voltage Current Transformer. For this article, we will only focus on live tank current transformer and dead tank current transformer.

Live Tank Current Transformers

In live tank current transformers, the main core of the transformer is placed in the top tank. The top tank also houses the secondary winding which is termed as ‘live’ part of the transformer body. Before placing them inside the tank, which is typically made of mild steel, the core and secondary winding is insulated with various types of insulating material to protect it from high voltage current.

The primary winding in a live tank CT is constructed of short length. This is done intentionally as a shorter shape provides higher levels of durability and strength when the primary winding is exposed to short time current.

In terms of functionality, in a live tank current transformer the heat generated during a short term current test is minimal due to faster dissipation of heat by the primary coil into the transformer oil which is filled in the tank.

In terms of costs, a live tank current transformer is cheaper to manufacture as it is more compact in size. Less steel is required in construction of the transformer tank body which means it uses lesser transformer oil. Thus it becomes more economical to produce.  They are also smaller in size which reduces the volume of space required to store or transport them.


Dead Tank Current Transformers

These are a category of current transformers in which the core of the transformer and its secondary winding are placed in the bottom part of the transformer tank. This tank is earthed which gives it the term ‘dead’ tank.

The primary winding in a dead tank CT is insulated similarly to other current transformers and is then brought down to the bottom tank where it is earthed. Further, the primary is made to pass through an insulated porcelain. In Dead tank CTs, the length of the primary conductor decides the mechanical force exerted on the transformer when it is exposed to short time dynamic current. It is therefore important to increase the length of the primary conductor to ensure that there is no damage to the transformer when it is exposed to high currents.

The size and shape of dead tank current transformers are large. They use up more steel in construction of transformer tank. Since the size of the transformer tank is larger, it also uses more transformer oil which makes it expensive to produce compared to live tank CTs. They are heavier and as such transportation costs involved in transporting them from manufacturing location to installation locations is more. As such, the demand for dead CTs is lower compared to live tank CTs.




Residual Voltage Transformers (RVT)are a type of instrument transformers that are used for protecting capacitor banks from earthing faults in an electrical system. Their primary function is to detect neutral to ground fault conditions and discharge capacitor banks. In general working conditions, the windings of an RVT have no voltage output. However, when there is an earth fault a voltage is developed across the open delta winding which activates the relay and protects the measuring equipments.

Most people confuse RVTs with voltage transformers. Although both are similar in certain aspects, their functioning is quite different. In some textbooks, therefore RVTs are classified as a sub-group of voltage transformers. The general voltages for residual transformer windings are 110V, 110V/ √3, or 110 V/3. The primary neutral of a use a 3 phase RVT when out to use should be earthed, or else harmonic voltages will be produced across the residual winding and cause damage. Most RVTs have a 5 limb a construction design.

According to Wikipedia, in its simplest form, a RVT is composed of consists of three distinct parts: two capacitors across which the transmission line signal is split, an inductive element to tune the device to the line frequency, and a voltage transformer to isolate and further step down the voltage for metering devices or protective relay.

The tuning of the divider to the line frequency makes the overall division ratio less sensitive to changes in the burden of the connected metering or protection devices. The device has at least four to five terminals: a terminal for connection to the high voltage signal, a ground terminal, and two secondary terminals which connect to the instrumentation or protective relay.

RVT transformers are manufactured for various system voltages. The most popular ones are of 11 kv, 25 kv, 33kv system voltages which can go upto 145 kv. Macroplast is a leading RVT manufacturer in India

Instrument Transformers are a category of transformers that are used to isolate high current and voltage in power systems to standardized lower current and voltage to enable metering by measuring instruments. They act as a buffer between the high voltage or high current circuits and the measuring equipment used for measuring electricity in power systems.

The primary function of Instrument transformers is to step down system voltage and current to standardized levels so that the metering equipment is safeguarded from high current and voltages running in the system.  The most common rating used by metering instruments are 5A & 110V. In a modern power system, the primary winding of an instrument transformer is connected to the high voltage or high current circuit while the metering instrument is connected to the secondary circuit.

The advantages of instrument transformers are:

  • They make it possible to measure alternating current (AC) of high power systems with small and easy to make to measuring instruments
  • They help in standardizing the values of measuring instruments. Most measuring instruments are manufactured to measure 5A & 110V
  • They act as a buffer between the high power current and voltage circuits which protects the measuring instruments from getting burnt or getting damaged

Instrument Transformers are primarily categorized into two types

  1. i) Current Transformers (CT)
  2. ii) Potential or Voltage Transformers (PT/VT)


Current Transformers

Current Transformer is a type of instrument transformer that is designed to produce a proportional amount of current in its secondary terminal compared to the primary. In electrical power systems, the role of current transformers is to reduce high voltage currents to proportional low value currents to enable measurement of high voltage currents using a standard measuring instrument called ammeter. The standard measure in most cases is 5 amperes. The primary winding of a CT consists of one or a sometimes a few more turns in its primary winding.


Current Transformer

Current Transformer

Voltage Transformer

Voltage Transformer or Potential Transformer is a type of instrument transformer that is designed to step down the voltage of power systems to a lower level to make is feasible to be measured by simple measuring instruments. The standard instrument used for measuring voltage in power systems is a voltmeter.  The universally standard measure of a voltmeter is 110-120 Volts. In PT/VT, the system voltage is applied in the primary windings and proportionate secondary voltage is received from the secondary terminals. Compared to CT, where the primary has a single or limited turns, PT/VT has large number of the primary windings and the secondary has lesser turns which is then connected to a measuring voltmeter.

Instrument transformers are one of the most critical components of an electrical power system. They are widely used in power distribution networks, particularly in electrical distribution sub-stations where high currents and voltages need to be stepped down for the purpose of measurement/metering. Instrument Transformers are manufactured in various system voltages starting from 11 kilovolts to 440 kilovolts and even higher.  The basic science however remains the same. Even within these, there are various methods of construction. Some are resin case indoor type, some are oil-filled, are gas filled amongst others. These various types are constructed depending on system requirements and used extensively in power networks.

Voltage/Potential Transformer

Voltage/Potential Transformer