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Generator RTD Malfunction & Fix

The generator experienced vibrations, causing the RTD element measuring stator winding outlet temperature to malfunction. This caused the reported temperature to drop below the setpoint of 40 degrees, triggering the temperature control valve to close. As a result, the primary water temperature rapidly increased until it reached the tripping value of 60 degrees, shutting down the turbine. To address this, an additional capillary RTD element was installed to provide a redundant temperature measurement. The logic was also modified to select the higher reported temperature value and lower the temperature threshold for opening the protection valve from 55 to 50 degrees.

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NILESH
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69 views1 page

Generator RTD Malfunction & Fix

The generator experienced vibrations, causing the RTD element measuring stator winding outlet temperature to malfunction. This caused the reported temperature to drop below the setpoint of 40 degrees, triggering the temperature control valve to close. As a result, the primary water temperature rapidly increased until it reached the tripping value of 60 degrees, shutting down the turbine. To address this, an additional capillary RTD element was installed to provide a redundant temperature measurement. The logic was also modified to select the higher reported temperature value and lower the temperature threshold for opening the protection valve from 55 to 50 degrees.

Uploaded by

NILESH
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Root Cause analysis:-

1. Due to vibration on Generator top the RTD element of stator winding outlet temperature
malfunctioned, This RTD element is used in Primary water temperature control loop.
2. Because of this malfunctioning, the value of primary water stator winding outlet temperature goes
below 40 deg which is used as process value of Primary Water temperature control loop .Set point of
PW temperature control valve is 40 deg .As SP=40 deg and PV = Below 40 deg temperature control
valve got closed and primary water temperature increased rapidly up to tripping value and Unit 08
Turbine tripped on Primary water temperature very High.
(Tripping Value = 60 deg)

Remedial Action taken :-

1.In the place of temperature gauge at primary water stator winding outlet, An additional capillary type RTD
element is installed and its signal is taken in DCS.

Logic Modication work carried out as per below:

Before Modification:

PV
PW Temp. RTD element
PV-SP
SP
Set point = 40 Deg C

After Modification:

Old PW Temp. RTD element PV


MAX

Installed PW Temp. RTD PV-SP


SP
Set point = 40 Deg C

2. Primary water temperature control valve protection open command value is modified from >55 deg to
>50 deg of primary water temperature after cooler.

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