Dry-Type Transformer Installation and Ventilation Requirements

Dry-Type Transformer Installation and Ventilation Requirements (On photo dry-type transformer placed and connected)

Installation

Dry-type transformers should be installed over foundations that are properly leveled and capable to withstand their weight.

When a transformer is fitted with wheels, make sure the equipment will be equally supported on its base points in order to assure its stability and to prevent any deformation.

When installing the transformer, the following factors should be carefully taken in account:

1. There should be a minimum spacing of 0,5 m between one transformer and another, and between the transformer and any adjacent wall in order to facilitate the access for inspection and ventilation, depending, however, on the project dimensions and the voltages;

2. The room where the transformer will be installed should be well ventilated as to assure proper natural ventilation, since this is an essential parameter for a proper performance of a dry transformer.

In this regard, it is important that the air inlets are located at the front part of the transformer near the bottom and the air outlets are located at the back part of the transformer, with near the top openings large enough to allow for a circulation of approx. 2,5 cubic meters of air per minute/kW of loss. (See the example calculation below).

Proper ventilation in the transformer room will grant the expected useful life and stable operation either on continuous regime or under momentary overloads.

Figure 1 - Natural transformer ventilation

As normally the natural ventilation is not sufficient, fans can be installed to increase the air flow i n the room according to Figure 2 or, preferably, adopt the refrigeration o f the room where the transformer will operate .

Figure 2 - Forced transformer Room Ventilation

To calculate the approximate size of the openings or the airflow necessary in the room the following expressions cab be used, considering a difference of 15ºC between the inlet air and the outlet air.

where:

P_t = total transformer losses sinked at 115°C [kW]
S = lower opening surface [m²]
S’ = upper opening surface [m²]
H = distance measured between the middle of the height of the transformer and the middle of the upper opening for air outlet [m]
V = cooling air volume[m³/min]

Reference: Instruction Manual For Dry-type Transformers – WEG