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Daily Preventive Maintenance Checklist

Preventive maintenance is an important approach for the long life and smooth working of equipment in any industry especially in solar plants. Daily visual inspections are essential in identifying potential issues before it’s too late for machinery. This article delves into the importance of a daily preventive maintenance checklist, emphasizing its significance in maintaining the reliability of critical equipment.

Daily Maintenance Checklist:

A comprehensive daily maintenance checklist covers various aspects, including equipment conditions, safety features, and environmental factors. To illustrate the practical application of such a checklist, here are a few points to consider during the first-level inspection.

Inverter Duty Transformers Inspection:

1. Visual Inspection of Temperature Indicators

Examine the WTI (Winding Temperature Indicator) and OTI (Oil Temperature Indicator) on inverter duty transformers. To assess moisture content in transformer oil, you can use the formula;

Moisture Content (%) = 100 X Pv / Pg


Pv is vapor pressure at oil temperature.

Pg is vapor pressure at the dew point.

2. Visual Checking of Gasket Joints and Cable Box

Inspect gasket joints and cable boxes on transformers for any signs of oil leakage or damage.

3. Check for Silica Gel Colour

Ensure the silica gel inside the transformer breathers or drying chambers maintain its specified color.

4. Checking the Oil Level of the Transformer

Verify that the oil level within the transformer is within the recommended range. If the oil temperature is raised, you can calculate it using the formula;


TCOR  is the Corrected temperature of the Oil

TMEAS is measured oil temperature.

α is the coefficient of volume expansion of transformer oil

5. Check Silica Gel Colour & Breather Healthiness

Assess both the silica gel color and breather condition. Moisture results in a change of color of silica.

Visual Inspection of the Auxiliary Transformer:

1. Visual Inspection of the Transformer

Examine the auxiliary transformer for any visible signs of damage, such as dents, cracks, or loose components.

2. Gasket joints and Cable Box

Inspect gasket joints and cable box for any oil leakage from the transformer.

3. Inspect Silica Gel and Breather

Check the silica gel color to see if there is any moisture. Also, inspect the breather for its proper working.

Silica Gel ColourMeaning
BlueDry (No Moisture)
PinkAbsorbed some Moisture
WhiteFully Saturated with Moisture

CCTV System:

1. Inspect the Condition of All Cameras

From the control room, assess the functionality of all cameras within the CCTV system.

2. Checking the Healthiness of Storage Drive

Ensure that the storage drive associated with the CCTV system functions correctly to store critical surveillance footage.

Inverter Inspection:

1. Visual Checks on Exhaust Fans in Inverter Rooms

Inspect the exhaust fans within inverter rooms to confirm they are clean and free from obstructions.

2. Check the Fans Are Operating – Using SCADA

Utilize the Supervisory Control and Data Acquisition (SCADA) system to monitor the status of the fans.

3. Check the Heating – Using SCADA

Similarly, use the SCADA system to monitor the heating elements within the inverter.

Indoor HT Panel:

1. Visual Inspection of Metering and Indication Circuits

Examine the indoor high-tension (HT) panel for any signs of damage or malfunction in metering and indication circuits.

2. Relay Healthiness Check

Perform a health check on relays within the indoor HT panel to confirm their proper functioning.

Outdoor HT Panel:

1. Visual Inspection of Metering and Indication Circuits

Inspect the outdoor HT panel for any issues with metering and indication circuits.

2. Relay Healthiness Check

Conduct a relay health check for the relays within the outdoor HT panel to ensure their reliability.

EquipmentRelay TypeHealth Status
Indoor HT PanelProtective RelayHealthy
Outdoor HT PanelProtective RelayHealthy

Fire Alarm:

1. Visual Inspection

Inspect the fire alarm system for any visible signs of damage or malfunction. 

2. Panel Alarm and Event Checking

Review the fire alarm panel for alarms and events. Investigate and address any alarms or events recorded by the system.

UPS (Uninterruptible Power Supply):

1. Check Input Supply in HMI

Monitor the input supply status on the Human-Machine Interface (HMI) of the UPS to ensure a stable power source. Input supply stability percentage (ISS) can be traced using the below formula.


TStable = Stable input supply time measure

TTotal = Total monitoring time 

2. Check Output Supply in HMI

Similarly, verify the output supply status on the HMI to confirm uninterrupted power delivery.

3. Check for Any Alarms or Events

Review the HMI for any alarms or events related to the UPS. The alarm occurrence rate is a helpful parameter in checking the condition of UPS.

AOR =NAlarm / Total

NAlarm = Number of alarms observed

TTotal = Total monitoring time

LDB (Load Distribution Board):

1. Visual Inspection of LDB

Conduct a visual inspection of the load distribution board to ensure its cleanliness and the absence of loose connections.


daily visual checklist is super important for keeping equipment in different industries working well. It helps organizations catch problems early, prevent breakdowns, and make sure equipment lasts a long time. This checklist, with specific things to look at every day, shows how checking equipment regularly is a practical way to make sure it keeps working well in all kinds of places.

Download the Checklist-Visual PM Checklist

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