Issue Caused By Faulty Analog Module

MAINTENANCE LOG SHEET	Date:2079/02/05                   Day: Thursday
	Time: 10:30AM
Related Equipment/Part:	Analog module, HMI and LCU panel of Unit-1

Reason for Maintenance	Temperature sensor data of unit-1 is not displayed in control room SCADA as well as HMI of LCU panel and analog module gets non-functional after about half an hour of replacement.
Primary Suspect	Faulty analog module or some factor causing module to get damaged.

Maintenance Activity	Analog module was replaced with the new one and found to be non-operational after some time.   Then the sensor lines connected to the analog module was checked by measuring the voltage obtained in the analog module from that specific sensor circuitry.   It is found that voltage signal to the analog module obtained from the shaft current measuring section was 36 V which was more than expected and is suspected to be the main cause of damaging the analog module. So, this section was disconnected from the analog module.     Also suspecting the higher voltage can damage analog module again the sensor wires were bypassed from their original terminals and was connected to analog module via spare terminals.   After finishing terminal wiring, the terminals needed to be redefined in HMI software so that temperature data can be displayed in control room SCADA as well as LCU panel HMI.    The Chinese team faced problem with the Chinese font in HMI software and also backup of HMI program file is not available with the company since the beginning. So, the software issue was later solved from their side along with the font problem. (Annex-4 and Annex-5)
Status after maintenance	After bypassing the sensor wire through the spare terminal, only sensor data of single sensor-instead of two- connected in turbine-generator parts is displayed in ‘unit’ section of control room SCADA. This is due to lack of available space in spare terminal. (Annex-1 and Annex-2)   The ‘monitor’ section of the control room SCADA and HMI of control panel is not displaying sensor data due to software issue. (Annex-3)   Shaft current is also not displayed as it is disconnected from the analog module.   However analog module is working normally after the maintenance.
Recommendation	The root cause of higher voltage obtained from shaft current measuring section is to be identified. Also, the backup program of HMI system should be made available to the company from the Chinese counterparts.

ANNEX

Annex 1: Wires bypassed from original terminal and connected to the spare terminal

Annex 2: Display of Single Sensor Data in ‘unit’ Section of Control Room SCADA

Annex 3: No Data Displayed in ‘monitor’ Section of Control Room SCADA

Annex 4: Chinese Font Problem in HMI of Unit-1 LCU Panel

Annex 5: HMI of LCU Panel After Rectification of the Font Problem