In oil type transformers, the changes in environment temperature and the transformer load will change during the operation time, which leads to changes in the transformer oil temperature and results in changes in the volume of the oil in transformer tank. The expansion tank (conservator) is connected with the oil in transformer tank by oil pipes; the expansion and contraction in transformer oil leads to increases and decreases in the volume of transformer oil in the conservator. The transformer oil in the conservator is also exposed to air. In order to prevent humidity contamination of the transformer oil – which will result in a reduction in the insulation resistance of transformer oil and cellulose insulation – a chamber containing desiccant will be used. Additional equipment options for our distribution transformers are available to those regularly used, which can be installed based on customer requirements, examples are given below: A variety of current transformers for measurement and protection Winding thermometers Cable box and bus-duct for HV side and LV side A variety of plug-in bushings The pressure relief relay Buchholz relay Earth resistance