Power Supply Installations Overview

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary function of sub-stations in the electric traction system?

To ensure continuous power supply. (correct)

To record passenger information.

To monitor train schedules.

To manage maintenance personnel.

What should be recorded in the inspection book at a sub-station?

Train departure times.

Weather conditions every hour.

Observations made by supervisory officials. (correct)

Daily passenger counts.

What is the maximum permissible temperature rise for the winding of a traction transformer at an ambient temperature of 45 degrees Celsius?

40 degrees Celsius.

55 degrees Celsius.

65 degrees Celsius.

50 degrees Celsius. (correct)

After how long can a traction transformer experience another 50% overload following continuous operation at maximum ambient temperature?

3 hours. Signup and view all the answers

Who is responsible for controlling switching operations at sub-stations?

Traction Power Controller. Signup and view all the answers

What is the overload capacity of traction transformers for a 100% overload?

5 minutes. Signup and view all the answers

Which part of the traction transformer has a maximum permissible temperature rise of 35 degrees Celsius?

Current carrying parts. Signup and view all the answers

What is a significant consequence of thermal and electrical stresses in oil-filled equipment?

Gas formation and lowering of flash point Signup and view all the answers

Which method is considered the most sensitive and efficient for detecting incipient faults in transformers?

Dissolved gas analysis (DGA) Signup and view all the answers

What happens to the condition of cellulosic insulation due to insufficient monitoring?

It suffers from reduced mechanical and dielectric strength Signup and view all the answers

Which action should be undertaken to prepare for the overhaul of a transformer?

Ensure spare gaskets of proper quality are available Signup and view all the answers

What is the recommended frequency for drawing oil samples for analysis in transformer condition monitoring?

Annually Signup and view all the answers

What aspect of oil is significantly affected by temperature rise in transformer operation?

Dielectric properties and flash point Signup and view all the answers

What should be done with bushings during the transformer overhaul process?

Carefully remove and protect them Signup and view all the answers

What can dissolved gases indicate in the context of transformer operation?

Incipient faults and deterioration Signup and view all the answers

In extreme cases, what can lower the flash point of the oil in transformers?

Gas formation due to electrical stress Signup and view all the answers

What is one main purpose of conducting gas chromatography on transformer oil?

To timely detect insulation deterioration Signup and view all the answers

What is the primary purpose of tap changers in Traction Transformers?

To adjust output voltage based on load conditions Signup and view all the answers

What voltage level must daily OHE voltage peaks remain below at the traction sub-station?

27.5 KV Signup and view all the answers

How often should a 24-hour record of voltages at neutral sections be taken?

Once a year Signup and view all the answers

What specifications are adopted for EHV grade oil used in transformers?

IS-335 and IS-1866 Signup and view all the answers

Which test can be conducted in PSI depots or sub-stations every six months?

Breakdown voltage (BDV) test Signup and view all the answers

What is the primary purpose of providing wedges in traction transformers?

To hold the windings tightly together against mechanical forces. Signup and view all the answers

What is the purpose of connecting a recording voltmeter at the traction sub-station?

To monitor voltage variations over time Signup and view all the answers

What condition may indicate a failure due to overheating in transformers?

Evidence of carbon deposits or flash marks on critical components. Signup and view all the answers

Which factor requires the CTFO/PSI to stay in contact with supply authorities?

To address changes in grid system connections Signup and view all the answers

What should be done regarding tools used during transformer maintenance?

All tools used must be listed out and accounted for to avoid hazards. Signup and view all the answers

What is a potential consequence of exceeding 27.5 KV at the traction sub-station?

Decreased lifespan of the transformer Signup and view all the answers

What is a characteristic feature of transformer failure due to lightning discharge?

Presence of flash marks on the end coil and nearby grounded parts. Signup and view all the answers

What is the primary characteristic monitored through the acidity test in transformer oil?

Degradation of insulation material Signup and view all the answers

What is recommended to counteract coil displacement in transformers?

Tighten the pressure screws and ensure wedges are fully home immediately. Signup and view all the answers

What should be noted if a transformer has been opened due to an internal fault?

Abnormalities such as carbon deposits and unusual odour Signup and view all the answers

What is the recommended location for replacing a burnt-out coil in a traction transformer?

In the manufacturer's works Signup and view all the answers

What cleaning measures should be taken inside the transformer tank?

Thoroughly clean and wash with fresh oil Signup and view all the answers

What is the best method to remove sludge from inaccessible places in a transformer?

Direct a thin jet of transformer oil under pressure Signup and view all the answers

Which of the following is NOT a recommended practice to protect the windings from moisture?

Ignore the moisture during service maintenance Signup and view all the answers

What should be done to the oil-tight gasket around the valve seat during maintenance?

Lightly polish the valve seat and renew the gasket Signup and view all the answers

How should debris and sludge be removed from transformer components?

With a wooden or fiber wedge to prevent damage Signup and view all the answers

What should you inspect if the coil assembly has been lifted after several years of service?

The amount of sludge formation present Signup and view all the answers

What is the first step in the maintenance process after opening a transformer?

Make a careful note of the internal conditions Signup and view all the answers

What is an important step after cleaning the transformer tank and before painting?

Ensure no rust or traces of oil remain Signup and view all the answers

What is the first action that should be taken to ensure the soundness of bonding and earthing connections?

Check physically the soundness of the connections. Signup and view all the answers

Which procedure is essential before checking the resistance of each group of earth electrodes?

Disconnect the group from the common earth system. Signup and view all the answers

What action should be taken if a battery is found to have excessive sediment accumulation?

Replace the battery with a new set. Signup and view all the answers

How often should the insulation resistance of motor windings be checked for motor-operated isolators?

Annually or as recommended during checks. Signup and view all the answers

What is the purpose of using a ‘Ductor’ in maintenance procedures for bus bars and connectors?

To measure the contact resistances of heavy current connections. Signup and view all the answers

What is the primary quality to be preserved during the purification of transformer oil?

Di-electric strength Signup and view all the answers

What occurs to the insulation resistance during the initial stages of the drying out process?

It drops to a low value due to heating Signup and view all the answers

At which point in the drying process should oil circulation be discontinued?

Upon completion of the drying out operation Signup and view all the answers

When does the insulation resistance rise above the leveling off point during the cooling process?

As oil cools after the drying out operation Signup and view all the answers

Which equipment specifications are referenced for purifying transformer oil?

RDSO’s Specification No.ETI/PSI/103 Signup and view all the answers

What factors can cause moisture absorption in transformer oil?

Defective breathers and untreated make-up oil Signup and view all the answers

What temperature is associated with a low insulation resistance during the drying out process?

75 degrees C Signup and view all the answers

What significant change occurs to the dielectric strength of cellulosic insulation over time?

It decreases due to mechanical stress. Signup and view all the answers

What method is utilized for condition monitoring of power transformers primarily based on gas analysis?

Dissolved gas analysis Signup and view all the answers

What happens to the flash point of transformer oil under extreme thermal stress?

It drops to between 50 degrees C and 80 degrees C. Signup and view all the answers

Why does the Buchholz relay fail to respond during the early stages of trouble in a transformer?

It requires a certain volume of gas to trigger. Signup and view all the answers

In what condition is it recommended to periodically undertake the overhaul of a transformer?

If it is faulty or at the end of 7-10 years. Signup and view all the answers

What is the primary purpose of gas chromatography in transformer condition monitoring?

To analyze the type and amount of dissolved gases. Signup and view all the answers

Which equipment condition requires immediate attention during transformer overhaul?

Excess sludge accumulation. Signup and view all the answers

What must be done with the oil before commencing maintenance work on a transformer?

It should be drained out. Signup and view all the answers

What is the first step when preparing for the removal of a transformer core during overhaul?

Ensure spare gaskets are available. Signup and view all the answers

What is the procedure for monitoring the condition of battery cells?

Check general conditions of all cells and measure specific gravity and voltage of the pilot cell, then for all cells if issues arise. Signup and view all the answers

Which action is required for bonding and earthing of electrical equipment?

Visually inspect all earth connections, ensuring duplicate earths are present for every equipment. Signup and view all the answers

During the inspection of insulators, what should specifically be looked for?

Cracks, chippings, and flashover marks, with replacement considered for badly chipped ones. Signup and view all the answers

What should be monitored regarding traction transformers?

The maximum oil temperature, silica-gel conditions, and gas collection in Buchholz relay. Signup and view all the answers

What must be done if the silica-gel in traction transformers appears pink?

Replace with dry gel and recondition the old silica-gel. Signup and view all the answers

What is the first step in checking oil levels in transformers and related equipment?

Inspect the oil level in the sight gauge glass and check for leaks. Signup and view all the answers

Regarding the operation of circuit breakers, what is a primary maintenance check?

Open the cover of the control box to inspect the operating mechanism. Signup and view all the answers

What should be done with minor chippings on insulators?

Apply a light coating of epoxy resin to prevent moisture ingress. Signup and view all the answers

In the context of traction transformers, which of the following is necessary for maintaining the silica-gel breather?

It must be monitored for color change and substituted when turning pink. Signup and view all the answers

How should checks be conducted for gas collection in Buchholz relays?

Gas collection must be checked continuously to ensure safety. Signup and view all the answers

What should be done if a battery is not in a fully charged condition?

Perform a boost charge and increase the trickle charging rate after investigation. Signup and view all the answers

What is a crucial aspect of maintaining the contact surfaces during maintenance?

Touch up the high spots on the contact surfaces to achieve a good fit. Signup and view all the answers

Which procedure must be followed for PTs during maintenance?

Check the fuse holders on the LV side to confirm their condition. Signup and view all the answers

During quarterly maintenance of batteries and battery chargers, what should be documented?

The specific gravity and cell voltage of every cell. Signup and view all the answers

What is the first step in maintaining booster transformers?

Replace or recondition the silica-gel breather, if necessary. Signup and view all the answers

When conducting inspections on auxiliary transformers, what value should be recorded alongside temperature?

Insulation resistance of the transformer winding. Signup and view all the answers

What maintenance step is specifically mentioned for the earth connections of booster transformers?

Check connections from the bottom to earth electrodes or rails. Signup and view all the answers

During maintenance checks of control and relay panels, what should be done with abnormal voltage or current readings?

Record them and take corrective action. Signup and view all the answers

What is a key maintenance action regarding silica-gel breathers in booster transformers?

Replace or recondition them as necessary. Signup and view all the answers

What should be checked for proper operation during the inspection of control and relay panels?

The state of all indicating and recording instruments. Signup and view all the answers

Study Notes

2020 Introduction

This chapter is divided into four sections
Section 1 covers the organization and duties of Chief Traction Foreman (Power Supply Installations)
Section 2 details the operation of sub-stations
Section 3 covers guiding notes on maintenance of power supply equipment
Section 4 outlines a recommended maintenance schedule for power supply equipment

Organization

Divisional set-up of senior subordinates under Sr. DEE/TRD is arranged in two patterns:
- Territorial basis
- Functional basis

Operational and Maintenance

Sub-stations are vital for continuous power supply
Transmission lines and associated gear (transformers, switch gear, control, and relay panels) are duplicated in case of component failure
Centralized control by a single authority (Traction Power Controller) for switching operations

Overload Capacity of Traction Transformers

Overload ratings typically include:
- 50% overload for 15 minutes
- 100% overload for 5 minutes
Temperature limitations are specified with ambient temperature (45°C)
- Winding temperature: 50°C (by resistance method)
- Oil temperature: 40°C (by thermometer)
- Current-carrying parts temperature: 35°C (by thermometer)
Hotspot temperature limits: ≤100°C

Inspection Book and Log Book at Sub Stations

Substations maintain "Inspection Books" for recorded observations by supervisors
Log books record traction transformer oil temperatures, ambient temperatures, currents, and voltages at set times
Investigate any unusual occurrences and implement corrective actions as required

Duties of Chief Traction Foreman, Power Supply Installation

Supervises installation maintenance according to schedules, ensuring serviceability
Maintains coordination with Power Controller, Chief Foreman (OHE) to ensure power supply reliability
Keeps organization prepared for equipment breakdowns/failures
Oversees safety equipment (relays, bonding, earthing) function, properly trains staff, and enforces safety precautions
Deploys staff for refresher courses for deficient staff
Cares for special instruments and tools used for maintenance and operation
Keeps close watch on spare parts, initiating timely actions to replenish stocks
Ensures proper accounting of all tools and stores
Deploys staff to sub-stations and switching stations when remote equipment fails
Conducts monthly inspections with emphasis on safety
Provides timely updates to AEE/TRD and Sr. DEE/DEE(TRD) on developments
Carries out other duties as directed

Protective Devices

Protective devices (alarms, trips, etc.) ensure safe operation with settings for extended use
Supervisory officials are notified for anomalies
Detailed reports are to be submitted to Sr. DEE/DEE(TrD)

Testing of Transformer Oil

Performance and longevity of transformers are improved with use of EHV grade oil
Standard specifications (IS-335 and IS-1866) apply for new oil and oil in service, and these tests should be carried out regularly

Oil Purification Plant

This plant aims to remove contaminants like water, deposits, dirt, sludge, dissolved moisture, and gases.
The main quality to preserve is dielectric strength
Removal of these contaminants is essential for safe operation.

Insulation Resistance During Drying-Out

Temperature and insulation readings are recorded every two hours during the drying process
Plotting these values on a graph shows four distinct stages of the process
Stages depend on oil temperature and moisture removal, with resistance gradually increasing as moisture leaves

Transformer Overhaul

Covered shops with facilities for core lifting are used to overhaul transformers
Equipment is thoroughly cleaned for internal faults, and component-by-component conditions are meticulously documented
Care must be taken to protect windings during overhaul

Circuit Breakers and Interruptors

There are different types of circuit breakers: Minimum oil, SF6, Vacuum etc.
Manufacturers' instructions for maintenance are available for all these types, with additional, updated directives by RDSO.

Battery Maintenance

Batteries must be in proper working order.
Condition assessment and maintenance for control, protection, and indication circuits is essential
Battery chargers should be appropriately sized
Periodic checks include specific gravity readings to ascertain the health and efficiency
Preventative steps for sulphation or over-charging are essential

Protective Relays

Specialists conduct maintenance, repair, and test all protective relays; proper records are maintained
Strict authorization is required for any relay setting changes
A detailed register is required to show specifics of each relay and associated testing/maintenance info
This information is also to be shared with the Senior DEE/TRD

Maintenance Schedules

Monthly, half yearly, and annual maintenance schedules are provided to ensure proper condition of equipment
These schedules should be adhered to, to prevent equipment failures and ensure safety and operational efficiency

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers key aspects of traction power supply installations, including the organization of Chief Traction Foreman duties, operational details of sub-stations, and maintenance guidelines. It also discusses essential components such as transformers, switch gear, and centralized control operations for efficient power management.