Cast Resin Transformer

Fire resistant 
  The cast coil with Epoxy resin with non-flammable characteristics has a self-fire-extinguishing performance, to be free from a fire from electrical sparks. 
    
Higher short circuit strength 
  The cast coil with Epoxy resin with the high electrical and mechanical strength is manufactured in a robust structure against an electro-mechanical force occurring during short circuit, external impacts, and abnormal vibrations.  
    
Moisture Proof 
  The cast coil with Epoxy resin has an enhanced dielectric strength and doesn’t suffer from the deterioration of dielectric property due to humidity and the aging effects of insulating materials, even after a long term without maintenances. 
    
Compact size 
  Compact size and lightweight type can be embodied by designing and manufacturing the coil by casting in a high vacuum using Epoxy resin and insulating materials with good dielectric strength. 
    
 High overoad capabillty
  The cast coil with Epoxy resin has a high thermal time constant factort, therefore it can endure much higher overloads for a short time. 
    
Low Loss, Low Noise 
  Low-loss and low-noise are embodied through the optimal compact design using silicon steel of low-loss and good insulating materials. 
    
Maintenance free 
  The cast coil with Epoxy resin doesn’t suffer from the deterioration of an insulating property due to humidity and moisture, therefore it is easy to inspect and maintain a transformer including the coil. 
    
Environmentally safe 
  Comparing to an oil-immersed transformer, it is free from an environmental pollution due to oil spill. 

Construction

KP’s Cast Resin Transformer comprises standard components such as high and low voltage coils, a steel core and a supporting structure, and is provided with further components by additional orders.

Installation & Operation

In order to increase safety and lengthen life span of a cast resin transformer, it must be installed properly and operated under suitable conditions.

ㆍ On mounting : A vibration proof rubber must be installed between the ground and a base channel when a cast resin transformer is mounted on the ground.

ㆍ Anchor Bolt : When a cast resin transformer is mounted on the ground, it must be installed after a Anchor bolt is buried as a below figure.
 
 

  
ㆍ In enclosure
 When a Casr Resin transformer is mounted on the ground, it must be installed after a Anchor bolt is buried as a below figure.

 
ㆍ High-voltage coil surface potential 
 
  
ㆍ Electric potential on a resin surface 
Typically, an electric potential on an Epoxy resin surface of a cast resin transformer is equal to about that on an inner conductor of the coil. Therefore it is very dangerous to touch the Epoxy resin surface during operation.An electric potential on an Epoxy resin surface is calculated like below. For example, in case of mounting a 22.9KV cast resin transformer in a housing, if a distance (150 mm) between a coil surface and a housing is maintained, an electric potential(Vs) on an Epoxy resin surface is calculated into
    

   wherein 
   Vo : Voltage to ground = 22,900 (V)
   te : Outer epoxy thickness of coil = 3 (mm)
   ta : air gap = 150 (mm)
   εe : Specific inductive capacity of Epoxy resin ≒ 4
   εa : Specific inductive capacity of air ≒ 1
    

 As above, an electric potential on an Epoxy resin surface becomes similar to that on an inner conductor of the coil. Even though a charging current is limited to a very low value, an impact due to touching the coil surface is very dangerous. Keep a person from touching the coil surface and attach a danger mark on the coil surface 
  
ㆍ Matters that demand special attention on the connection of high and low voltage terminals 
When connecting a bus bar and a cable to high and low voltage terminals, a flexible bus bar must be used in order to reduce a stress onto high and low voltage terminals. 
  
ㆍ Method for reducing noises from a transformer 
  ㆍl Install a vibration proof rubber between a base channel and the ground ㆍl Install a flexible bus bar when connecting high and low voltage terminals. ㆍl When installation in a housing, prevent vibration of a housing by separating the transformer from the housing. ㆍl Prevent vibration of a body of a transformer by maintaining it parallel to the ground. 

Maintenance & Overhaul

Check points when installing a cast resin transformer

Installing conditions  

Installing place must be clean and free from care of submersion under water, especially not exposed water drops from a ceiling of it. There must be a ventilation means for getting rid of the heat generated from a transformer.  

Check of a transformer being taken custody for long term  

When dusts are deposited on a transformer according to long term custody, eliminate dusts by a vacuum cleaner or blow away dusts by compressor, and wipe it by a dry duster.      

A vinyl package for preventing from inserting of dusts, screws, nuts, washers and etc, must be maintained until power is on after installation.(when connection of 1st and 2nd terminals, tear off partly)    

Torque for HV Terminal connection  

Unit : kg-cm

Torque for LV Terminal connection  

Unit : kg-cm
 

  Check points before receiving power

Get rid of a vinyl package, and check connection status, insulating separation distance, whether alien substances remain, whether a component is damaged, and bolt torque.

Check whether tap connections accord with that of a label.

Measure insulations using an insulation ohmmeter(DC 1000V Megger) like below.  

When measuring values are below than above values, check humidity, and if it is, get rid of humidity by dryer, and measure an insulation resistance again. Nevertheless if a measured insulation resistance is below than the limit value, contact with the A/S(after-sale service) department.

 Maintenance

In case of general operating circumstance, get rid of dusts and blow away over deposited dusts by dry compressor every year. Cleaning term depends on circumstances. Check engagements of bolts by a torque wrench during performing a maintenance work