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RHONA S.A

SERVICE INSTRUCTIONS

DEPARTAMENTO TRANSFORMADORES

SUDDEN PRESSURE RELAY

Branch :

www.indubras.com

Model: RPS-114.A

GENERAL The type RPS-114 and RPS-114.A Sudden Pressure Relays are protection equipment for sealed type transformers, installed above maximum liquid level in the space between the insulating liquid and the transformer cover. The Relay actuates when a sudden internal pressure increase occurs, independently of the transformers working pressure. This Relay does not work for slow pressure changes due to lightning, maneuvering over-voltages, as long as they do not lead to a transformer failure.

RHONA S.A

SERVICE INSTRUCTIONS

DEPARTAMENTO TRANSFORMADORES

CONSTRUCTION AND OPERATION The Sudden Pressure Relays RPS-114 and RPS-114.A are composed of (see figures 1 e 2): Relay body (1) Equalizer (2) Metal bellows (3) Microswitch (5) Terminal box (7) Manual relief valve (4) Connection terminals (6)

FIGURE 1 : Sudden Pressure Relay RPS-114

RHONA S.A

SERVICE INSTRUCTIONS

DEPARTAMENTO TRANSFORMADORES

FIGURE 2 : Sudden Pressure Relay RPS-114.A When the pressure change inside the transformer occurs slowly during normal operation, the equalizer hole is enough to equalize the Relays internal pressure with the transformers tank internal pressure. When the transformers internal pressure change occurs suddenly, the equalizer hole will not be large enough to allow the pressures to equalize. It will, thereby allow the transformers internal pressure to be larger than the internal pressure of the Relay, making the bellows stretch and actuating the microswitch built into it (5). SUDDEN PRESSURE RELAY INSTALLATION The Sudden Pressure Relay is normally mounted on the tanks side wall or on the transformers cover, above the insulating liquid maximum level. MAINTENANCE We recommend that operation simulation tests be carried out for the Sudden Pressure Relay every year or every two years, according to the following procedures: 1- Check the actuating pressure.

RHONA S.A

SERVICE INSTRUCTIONS

DEPARTAMENTO TRANSFORMADORES

2- Check the pressure equalization time, represented by the ratio between the transformer internal pressure and the time necessary to equalize the pressure between the transformer and the Relay by means of Graph 1. It can be done with the transformer energized as long as its the internal pressure is not less than 0,04 kgf/cm². 3- Measure the transformer internal pressure. 4- Turn off the auxiliary Relay feed power (if there is one). 5- Connect an ohmmeter lamp in series on the Sudden Pressure Relays terminals 2 and 3. 6- Open the test valve. The micro-switch will actuate and indicate on the ohmmeter: open circuit. 7- Close the test valve again and measure the necessary time to equalize the pressure that will appear when the Sudden Pressure Realy returns to the normal position, indicating, on the ohmmeter: closed circuit. The values measures should be within or close to the operation area of Graph 1. Large deviations on the measured values indicate that there are problems on the relay that must be corrected.