No. 3, 19 Sayyad Shirazi St, Mashhad, Iran.
051-38824146
Persian
Behso Niro Shargh company
Here, we will comprehensively cover the maintenance and testing methods for various types of posts (substations).
Overall Maintenance Philosophy: Two Main Strategies:
Preventive Maintenance (PM):
Performing scheduled services based on time every 6 months or based on equipment operating hours after 2000 hours of transformer operation. The goal is to prevent the occurrence of a fault.
Condition-Based Maintenance (CBM): Performing service based on the actual condition of the equipment, which is determined through diagnostic tests and continuous monitoring. This method is more cost-effective and efficient.
Overall Maintenance Philosophy: Two Main Strategies:
Preventive Maintenance (PM):
Performing scheduled services based on time every 6 months or based on equipment operating hours after 2000 hours of transformer operation. The goal is to prevent the occurrence of a fault.
Condition-Based Maintenance (CBM): Performing service based on the actual condition of the equipment, which is determined through diagnostic tests and continuous monitoring. This method is more cost-effective and efficient.
Maintenance of Extra High Voltage/High Voltage (EHV/HV) Substations
A) Preventive Maintenance (PM):
Visual inspections:
Periodic daily, weekly, and monthly inspections by site operators.
Checks oil leaks (in transformers and oil circuit breakers), oil level, SF6 gas pressure, corrosion, insulator contamination, paint condition, loose mechanical connections, presence of animals and birds, and signs of damage.
Mechanical services:
Circuit breakers and disconnectors: checking spring mechanisms, spring-charging motors, actuator motors, and greasing joints and connections according to the manufacturer's instructions.
Transformers: checking the operation of pumps and fans in the cooling system, checking the On-Load Tap Changer (OLTC) for oil level and operation count.
Grounding System Service: Inspecting connections and testing the earth grid resistance.
B) Periodic and Diagnostic Testing:
These tests are performed by specialized teams using precision instruments.
Maintenance of Medium Voltage (MV) Substations
Maintenance activities are primarily focused on Medium Voltage Switchgear and distribution transformers.
Preventive Maintenance (PM):
Visual inspection: checking the position indicator of breakers, SF6 gas or vacuum pressure indicators (in Vacuum Circuit Breakers), and oil sight glasses (in oil-filled transformers).
Mechanical service: testing the manual and motorized operation of breakers (racking in/out, closing and opening) to ensure smooth operation. Lubricating connections.
Cleaning: using dry compressed air to clean the inside of the switchgear from dust.
Periodic Tests:
Contact resistance test (Micro-ohm test) for breakers.
Insulation test on breakers and busbars.
Breaker timing test.
Protection relay functional test (secondary injection).
Dissolved Gas Analysis (DGA) for oil-filled transformers.
Ground resistance test.
Maintenance of Low Voltage (LV) Substations
The primary focus is on Distribution Boards (DBs) and the breakers inside them.
Preventive Maintenance (PM):
Visual inspection: checking for signs of heat (discoloration or burning), loose connections, and excessive dust.
Tightening connections (Thermographic Inspection): The most important task! Tightening terminal screws with the appropriate torque (using a torque screwdriver). Loose connections lead to overheating and fire.
Cleaning: energizing and cleaning the inside of the panel with compressed air.
Periodic Tests:
Breaker Functional Test: ensuring the proper opening and closing of Air Circuit Breakers (ACBs) and Miniature Circuit Breakers (MCBs).
Contactor and Relay Function Test.
Insulation Resistance Test: between phases and earth.
Earth Leakage Test: for Residual Current Devices (RCD/ELCB).
Earth Loop Impedance Test: to ensure the correct operation of protection during a short circuit.
Modern Methods and Monitoring Technologies
Thermography (Thermal Imaging Cameras): one of the most powerful tools for preventive maintenance. During inspections, thermal images are taken of connections, breakers, and busbars. Any point with an abnormal temperature (hot spot) is identified and rectified before an incident occurs.
Online monitoring systems:
Online DGA monitoring for transformers.
Partial Discharge (PD) monitoring for equipment insulation.
Circuit Breaker Condition Monitoring: recording the number of operations, trip times, and interrupted currents.
Computerized Maintenance Management Systems (CMMS): Such as SAP PM, are used for scheduling, recording history, and managing all maintenance activities.
Final Summary and Safety Notes
Top priority: safety.
All maintenance and testing activities must be performed under a Work Permit and in full compliance with Lockout/Tagout (LOTO) procedures. Nothing replaces safety.
Documentation: recording the results of all inspections, services, and tests is essential for analyzing equipment degradation trends and optimizing planning.
A) Preventive Maintenance (PM):
Visual inspections:
Periodic daily, weekly, and monthly inspections by site operators.
Checks oil leaks (in transformers and oil circuit breakers), oil level, SF6 gas pressure, corrosion, insulator contamination, paint condition, loose mechanical connections, presence of animals and birds, and signs of damage.
Mechanical services:
Circuit breakers and disconnectors: checking spring mechanisms, spring-charging motors, actuator motors, and greasing joints and connections according to the manufacturer's instructions.
Transformers: checking the operation of pumps and fans in the cooling system, checking the On-Load Tap Changer (OLTC) for oil level and operation count.
Grounding System Service: Inspecting connections and testing the earth grid resistance.
B) Periodic and Diagnostic Testing:
These tests are performed by specialized teams using precision instruments.
Maintenance of Medium Voltage (MV) Substations
Maintenance activities are primarily focused on Medium Voltage Switchgear and distribution transformers.
Preventive Maintenance (PM):
Visual inspection: checking the position indicator of breakers, SF6 gas or vacuum pressure indicators (in Vacuum Circuit Breakers), and oil sight glasses (in oil-filled transformers).
Mechanical service: testing the manual and motorized operation of breakers (racking in/out, closing and opening) to ensure smooth operation. Lubricating connections.
Cleaning: using dry compressed air to clean the inside of the switchgear from dust.
Periodic Tests:
Contact resistance test (Micro-ohm test) for breakers.
Insulation test on breakers and busbars.
Breaker timing test.
Protection relay functional test (secondary injection).
Dissolved Gas Analysis (DGA) for oil-filled transformers.
Ground resistance test.
Maintenance of Low Voltage (LV) Substations
The primary focus is on Distribution Boards (DBs) and the breakers inside them.
Preventive Maintenance (PM):
Visual inspection: checking for signs of heat (discoloration or burning), loose connections, and excessive dust.
Tightening connections (Thermographic Inspection): The most important task! Tightening terminal screws with the appropriate torque (using a torque screwdriver). Loose connections lead to overheating and fire.
Cleaning: energizing and cleaning the inside of the panel with compressed air.
Periodic Tests:
Breaker Functional Test: ensuring the proper opening and closing of Air Circuit Breakers (ACBs) and Miniature Circuit Breakers (MCBs).
Contactor and Relay Function Test.
Insulation Resistance Test: between phases and earth.
Earth Leakage Test: for Residual Current Devices (RCD/ELCB).
Earth Loop Impedance Test: to ensure the correct operation of protection during a short circuit.
Modern Methods and Monitoring Technologies
Thermography (Thermal Imaging Cameras): one of the most powerful tools for preventive maintenance. During inspections, thermal images are taken of connections, breakers, and busbars. Any point with an abnormal temperature (hot spot) is identified and rectified before an incident occurs.
Online monitoring systems:
Online DGA monitoring for transformers.
Partial Discharge (PD) monitoring for equipment insulation.
Circuit Breaker Condition Monitoring: recording the number of operations, trip times, and interrupted currents.
Computerized Maintenance Management Systems (CMMS): Such as SAP PM, are used for scheduling, recording history, and managing all maintenance activities.
Final Summary and Safety Notes
Top priority: safety.
All maintenance and testing activities must be performed under a Work Permit and in full compliance with Lockout/Tagout (LOTO) procedures. Nothing replaces safety.
Documentation: recording the results of all inspections, services, and tests is essential for analyzing equipment degradation trends and optimizing planning.