Sub-Stations and Switching Stations Overview

Responsible for safe and efficient operation of traction power supply installations, sub-stations, switching stations, booster, and auxiliary transformers within their assigned area.

Prescribed plans for inspection and repair, ensuring equipment is always ready.

Coordination with the traction power controller for reliable power supply.

The team's preparedness to quickly address equipment failures.

Following a schedule for inspecting and maintaining safety equipment like protective relays and bonding.

Ensuring staff follows safety procedures and properly utilizes equipment in maintenance tasks.

Monitoring spare parts stock and taking action to replenish supplies needed for maintenance and operation.

Monitor gas pressure and temperature; supply gas if pressure is low; check pressure switches.

Clean porcelain, inspect/replace contacts, replace absorbent, and evacuate the breaker quickly.

Verify stroke, check clearances, re-lubricate parts, assess pressure gauge and pneumatic system leakage, check housing for issues and ensure fasteners are tight.

Follow guidelines for general maintenance (operating mechanism, housing), but vacuum bottle(interrupting chamber) does not require specific maintenance, except for the pneumatic circuit.

Essential equipment in power supply installations; proper maintenance is crucial.

110V, 200Ah lead acid cells used for control, protection, and indication circuits in traction sub-stations.

110V or 72V, 40Ah lead acid batteries for circuit breakers, interrupters, and motor-operated isolators in switching stations.

Batteries of suitable voltage and capacity, connected to sub/switching station batteries to reduce the number of batteries at a location.

Mains-operated chargers should provide trickle charge or boost charging and should be sized according to battery capacity.

Environmental factors that negatively impact the quality of work.

Scheduling inspections to avoid overlapping among inspectors, ensuring all locations are inspected within a set timeframe.

The schedule for performing maintenance tasks, which can be adjusted based on local needs.

Establishing maintenance schedules for new equipment, using manufacturer guidelines and external recommendations.

Maintenance schedules for SF6 type circuit breakers, as defined by manufacturers.

Work on or near active electrical equipment is not allowed unless power is off and other safety measures are implemented.

Preventing unauthorized access to and tampering with unattended electrical equipment.

Unannounced inspections that help deter unauthorized actions at substations/switching stations.

Duty of all electrical department staff members to remain aware of and observe for any activity of unauthorized intervention.

A measure of the battery's charge level, indicating the concentration of acid in the electrolyte.

Applying a higher charging current to a depleted battery to quickly restore its charge.

Regular inspection and maintenance of Potential Transformers (PTs) and Current Transformers (CTs) to ensure accurate voltage and current readings.

Ensuring the booster transformer is properly connected to the earth for safety and to prevent electrical shocks.

Measuring the resistance of the transformer winding to prevent electrical leakage and ensure insulation integrity.

Visually inspect insulators for damage like cracks or chips, clean with a dry cloth, and replace badly damaged insulators.

Minor chips on insulators can be sealed with a thin layer of epoxy resin to prevent moisture from entering.

Check the oil level in the transformer's sight gauge glass and ensure it's within the specified range. Replenish oil if necessary.

Record the maximum oil temperature on the dial indicator and reset the indicator after each inspection.

Inspect the explosion vent diaphragm for any damage and ensure it's free of oil. This vent serves as a safety device in case of a pressure build-up.

Check the silica-gel breather for moisture absorption. If it turns pink, replace it with dry silica-gel. A wet breather indicates moisture entering the transformer.

Check for gas collection inside the transformer. If gas is present, it might indicate internal faults.

Inspect the transformer for oil leakage, particularly at the body, conservator tank, drain valve, and foundations. Address any leakage by tightening bolts or replacing gaskets.

Ensure the transformer's heater, located in the marshalling box, is functioning properly and that all terminal connections are in order.

Clean the circuit breaker's control box, examine the interior, and check for signs of moisture, corrosion, or worn parts. Ensure protective gaskets are in good condition.

A type of circuit breaker that uses sulfur hexafluoride (SF6) gas as an insulating and arc-quenching medium. SF6 gas offers excellent electrical insulation, thermal stability, and arc-quenching properties.

SF6 gas is inert, thermally stable, and has exceptional dielectric strength (resistance to electrical breakdown). It also has excellent arc-quenching properties, meaning it can quickly extinguish electrical arcs.

During arcing, a small amount of SF6 gas decomposes into solid byproducts. These byproducts are usually metallic fluoride which appears as a fine grey powder with good dielectric strength.

A high-quality absorbent material is incorporated into the SF6 circuit breaker to remove any decomposed gaseous byproducts, ensuring the gas remains pure and effective.

Circuit breakers that use oil as insulation and to quench electrical arcs. They were used in older systems but require frequent oil replacement and maintenance.

Regular maintenance of all types of circuit breakers (SF6, oil, vacuum) is crucial to ensure their reliable operation and prevent potential failures.

Always refer to the manufacturer's detailed instructions for the correct installation, commissioning, operation, and maintenance procedures for all types of circuit breakers/interrupters.

Regularly inspect Potential Transformers (PTs) and Auxiliary Transformers (ATs) for leakage of oil, ensuring they function properly.

Ensure the correct alignment of blade tips in the fixed contact jaws of isolators, and check the alignment of arcing horns.

Inspect the acid level, sedimentation, specific gravity, and voltage of batteries. Check for sulfation and tightness of inter-cell connectors. Ensure proper functioning and size of the charger fuses.

Check the control box gaskets for water and dust tightness. Verify smooth local and remote operation and inspect the mechanism. Also, monitor oil level and look for leakages.

Inspect the switchyard for vegetation, fencing, cable trenches, and trench cabins. Ensure proper maintenance and security.

The health of a lead acid battery can be assessed by the color of the deposits on the plates. Whitish deposits indicate undercharging, while brown deposits indicate a healthy battery. Excessive shedding of active material from the positive plates signals overcharging.

Overcharging a battery leads to excessive shedding of active material from the positive plates, resulting in brown-colored deposits. This indicates the battery is being stressed.

Undercharging a battery leads to the formation of whitish deposits on the plates, indicating the battery is in a discharged state.

Boost charging is a quick solution for a deeply discharged battery. It involves applying a higher charging current to rapidly restore the charge level.

Trickle charging involves providing a low and continuous charge to maintain a battery's health and prevent it from being fully discharged.

Inter-cell connectors need to be clean, tight, and in good contact with cell lugs to ensure proper electrical flow between cells within a battery.

Maintaining inter-cell connectors involves inspecting for cleanliness, tightness, and corrosion. Applying Vaseline can help prevent corrosion.

Inspect copper connectors for any signs of copper sulfate corrosion, which can be cleaned up to prevent further damage.

Specialized staff trained in the maintenance, testing, and calibration of protective relays is crucial for maintaining the safety and reliability of electrical systems.

A register should be maintained for each protective relay, recording details such as installation date, maintenance history, and calibration information.

During maintenance, check the gas pressure and temperature. If the pressure is below the specified value, supply gas. Also, verify the settings of the gas pressure switches.

Lead-acid batteries are critical components in power supply installations, and proper maintenance is crucial for their reliable operation.

Batteries are installed in traction sub-stations (110V, 200Ah), switching stations (110V or 72V, 40Ah) and at remote control locations. The remote control equipment is often connected to the battery at the sub-station/switching station to reduce the number of batteries needed.

Vacuum circuit breakers have a special vacuum bottle component that doesn't require regular maintenance, unlike other types of circuit breakers.

Lead-acid batteries are essential for power supply installations, and proper maintenance is crucial for their reliable operation.