Ardan's transformers are fitted with some accessories as standard and some are per customer's request. The range of accessories includes:

Buchholz relays Gas sampling device

The presence of gas inside an oil insulated transformer is a clear sign of malfunctioning.
The Buchholz relay has the function of collecting and keeping the gas in its interior, and then sending an alarm and/or a trip signal to the transformer.
Nevertheless the Buchholz relay trips the transformer in case of high speed in oil flow, from the transformer to the conservator.

Oil level indicators

Oil level indicators with magnetic joint are usually used on transformers' conservators.
Their function is to give a visual alarm of the oil level contained in the conservator. Furthermore they are provide with microswitches to signal the alarm in case the oil level reaches its minimum and/or maximum.

Porcelain bushing insulators                                                                 

The range of porcelain bushing insulators for oil and air is so wide that it can accomplish all our customers' needs both on power and distribution transformers.
Porcelain bushing insulators, provided with connectors and gaskets, are designed in accordance with the following European and International Standards:

Technical specifications

Nominal voltage
1kV - 3kV - 12kV - 24kV - 36kV - 52kV - 72,5kV
Nominal Current
250A - 630A - 1000A - 2000A - 3150A - 4500A - 5000A - 6500A - 8000A
Plug-in bushings 

The epoxy resin bushings with internal plug connection and internal coupling are manufactured in accordance with EDF HN 52 S 61 - CENELEC EN-50181-50180 - IEEE 386-1995 - UTE C 66-555 - DIN 47636 Standards.

250A, 400A, 630A and 1250A 24 and 36KV
Pressure relief valves

Pressure relief valves are used to evacuate any overpressure found in the oil tanks. They operate in case  the pressure increases in an accidental and uncontrolled way creating the danger of explosion of the same tank.
Their main characteristic is to operate in a very short period of time (few thousandths of a second) by evacuating the pressure increase that has taken place.
These valves are widely used in the metal tanks of oil-cooled electric transformers.
In fact a sudden and violent short-circuit generates instantaneously an enormous volume of gas which, if not readily discharged towards the exterior, could cause the explosion of the transformer itself.
The application of one or more valves and the choice of the proper diameter must be made by taking into consideration the oil volume contained in the transformer.

Integrated Safety detector – R.I.S or DGPT 

Integrated Safety detector cover the need to integrate the functions performed by a number of electric transformer accessories in a single, compact and reliable instrument.
In fact it gathers in just one device the functions of controlling pressure, temperature, oil level, and gassing in oil insulated electric transformers.

Summary of its functions

Pressure switch: closes/opens a circuit on pressure ranging (from 100 up to 500mbar).

Thermometer: visual representation of oil temperature and maximum temperature reached
  • "T2" Thermostat switch (alarm): closes/opens a circuit at a predetermined temperature level (from 30°C up to 120°C).
  • "T1" Thermostat switch (stop): closes/opens a circuit at a predetermined oil level (from 30°C up to 120°C).
  • Indicator: visual detector of any slight variation in oil level
  • Detector: visual detector of any significant variation in oil level through closing/opening of an electric circuit.
  • Detector: closes/opens a circuit when the maximum gas volume is reached (max. 170 cm3).
Shutter valve

In the event of rapid Ioss of oil from a transformer for whatever reason, it is necessary to have an automatic operating valve that prevents the conservator from draining.
RDR-MK II Shutter Valve is used for this purpose.
this valve is considered an essential safety device by many customers. The shutter valve is fitted close to the Buchholz Relay in the feed pipe between the transformer tank and its conservator.
It is caused to operate by the dynamic thrust exerted by the liquid flowing through it when that flow rate exceeds a predetermined limit. Below that limit the valve remains open to allow the normal flow caused by thermal expansion and contraction.

Winding and oil temperature indicators

Oil temperature indicators, and winding temperature indicators, are instruments purposely designed to measure the temperature both of the insulating oil and the winding in the electric power transformers.
It is also possible to have a remote display to visualize the indications.

Accessories for cast resin transformers

Forced Air Ventilation
As cast resin transformers are air cooled, by forcing maximum air flow through the coils the transformer capacity can be increased up to 40%. He use of these fans are in conjunction with thermal sensors, either pre-determined temperature set PTC or dynamic read PT-100 sensors are used in conjunction with control relays.

Temperature control units

Temperature control unit is a digital device which, connected to four PT 100 probes, checks and measures the temperature of electrical circuits used in air and/or resin insulated transformers.
Through a specific software, the unit acquires, stores and signal each anomalous variation in the temperature by sending an alarm and/or by controlling some cooling integrated systems.