Pressure Relief Valves for Transformer

For more than 30 years, Pressure Relief Valves have been used to protect transformer tanks. However, all transformers that explode are equipped with this device. The incapability of Pressure Relief Valves to release the pressure in these cases led to conduct their dynamic mechanical study. In fact, such calculation could not be conducted until the pressure gradients during short-circuit conditions were discovered

Pressure Relief Valves are limited by:
• The spring inertia that delays their response time and opening
• The U-shaped exhaust evacuation that creates energy losses and reduces the pressure evacuation speed
• Their geometry because when it is half opened, the evacuation surface does not exceed 15% of the maximum evacuation surface



The Transformer Protector and Pressure Relief Valve behaviors have been simulated under the same short-circuit conditions in order to compare their performances. For each simulated case:

• The Transformer Protector surpassed the Pressure Relief Valve and prevented the transformer tank explosion
• The Pressure Relief Valve never avoided transformer tank explosion



Picture beside is describe when pressure relieve valve signal can trigger relay 86 to open generator circuit breaker (Unit Trip)








When the pressure of transformer oil tank is increase more than set pressure, the mechanical indicator will be extend and keep extend until the pressure down and operator initiate to reset.

From http://www.transproco.com/research.htm