Power Supply for Traction Systems
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Questions and Answers

What is the primary frequency of power supply for electric traction?

  • 55 Hz
  • 48.5 Hz
  • 60 Hz
  • 50 Hz (correct)

What voltage range must be maintained at the feeding posts for reliable traction supply?

  • 20 kV to 22 kV
  • 22 kV to 24 kV
  • 25 kV to 27.5 kV (correct)
  • 28 kV to 30 kV

What is one of the key responsibilities of the Railway concerning power supply reliability?

  • To ensure supply system is completely independent of Supply Authorities
  • To reduce traction loads during peak periods
  • To establish periodic meetings with Supply Authorities (correct)
  • To supply power from alternative sources

Which of the following measures is NOT suggested for maintaining power supply reliability?

<p>Disconnection of traction load during exigencies (B)</p> Signup and view all the answers

What cumulative effect can short-duration power supply interruptions have on Railway operations?

<p>Severe disruptions to Railway working (B)</p> Signup and view all the answers

When are the traction voltage limits particularly emphasized during meetings with Supply Authorities?

<p>When addressing reliability of supply (B)</p> Signup and view all the answers

What action is required if traction load is not treated as an essential load?

<p>Periodic efforts at high-level meetings to secure acceptance (D)</p> Signup and view all the answers

What is one of the items that must be checked before passing bills from the Supply Authorities?

<p>The payee is indicated as per the agreement. (D)</p> Signup and view all the answers

Which condition is necessary to avoid penalties related to power factor at traction sub-stations?

<p>Power factor should be as close to unity as possible. (A)</p> Signup and view all the answers

What should be done in case of any disputes or discrepancies related to billing?

<p>Payments should be made 'under protest.' (C)</p> Signup and view all the answers

When planning power factor improvement, which sub-station should be prioritized?

<p>The ones feeding large marshalling yards. (B)</p> Signup and view all the answers

What should be done if the average monthly power factor is calculated?

<p>Make sure it does not go leading while correcting. (D)</p> Signup and view all the answers

What is required for the power supply for electric traction before it can be taken?

<p>A specific agreement with the concerned Supply Authority (A)</p> Signup and view all the answers

What happens when the grid supply to a traction sub-station fails?

<p>Emergency working is needed by extending the feed from adjacent sub-stations (C)</p> Signup and view all the answers

What principle regarding maximum demand has been agreed upon by most supply authorities for billing purposes?

<p>Ignoring temporary increases in maximum demand during emergencies (B)</p> Signup and view all the answers

How is the railways' traction power recommended to be charged according to the latest methodology?

<p>On the basis of simultaneous maximum demand of contiguous sub-stations (C)</p> Signup and view all the answers

What aspect of electric traction costs is highlighted as substantial?

<p>Energy costs (B)</p> Signup and view all the answers

What should be considered in the tariff structure for electric traction?

<p>Multiple parameters that could affect pricing (C)</p> Signup and view all the answers

What should the contract demand for each sub-station relate to?

<p>The expected actual maximum demand to avoid excess charges (B)</p> Signup and view all the answers

What is a consequence of not finalizing the power supply agreement promptly?

<p>Increased costs and operational delays (D)</p> Signup and view all the answers

Who bears the cost of the equipment needed for the methodology changes regarding the charging of traction power?

<p>The Railways (C)</p> Signup and view all the answers

What is the preferred notice period for altering Contract Demand?

<p>4 to 6 weeks (C)</p> Signup and view all the answers

What should be considered to minimize the energy bill in electric traction?

<p>Maximum Demand Charge (D)</p> Signup and view all the answers

What happens when the power factor falls below a specified value?

<p>A penalty charge is applied (C)</p> Signup and view all the answers

How is the billing demand usually determined?

<p>It is the higher of contract demand or actual MD. (B)</p> Signup and view all the answers

What is the excess energy calculation based on?

<p>Total energy adjusted for maximum demand and contract demand (C)</p> Signup and view all the answers

What is a common minimum guarantee percentage return stipulated in agreements?

<p>15 to 20% (B)</p> Signup and view all the answers

What charge accounts for variations in fuel costs and calorific value?

<p>Fuel Adjustment Charge (FAC) (D)</p> Signup and view all the answers

What is a consequence of exceeding the Contract Demand for just 15 minutes?

<p>Proportionate units for the entire month are charged at a higher tariff (D)</p> Signup and view all the answers

What should be done to avoid penal charges related to Contract Demand?

<p>Review Contract Demand periodically (A)</p> Signup and view all the answers

What is typically true about the energy charge in electric traction?

<p>It varies as Paisa/kWh. (B)</p> Signup and view all the answers

How should billing figures be calculated when a second set of meters is provided at Railways' cost?

<p>Based on the average readings of the two sets of meters (D)</p> Signup and view all the answers

Who is responsible for taking the monthly meter readings?

<p>Representatives of both the Supply Authority and the Railway (B)</p> Signup and view all the answers

What additional information should a supervisory official obtain during meter readings at grid sub-stations?

<p>Current maximum demand for traction (C)</p> Signup and view all the answers

Why should the Supply Authorities' bills be carefully scrutinized?

<p>To ensure accuracy with reference to the Agreement and tariff (C)</p> Signup and view all the answers

What should be done if the minimum charge payable exceeds the actual energy consumption?

<p>Notify CEE and the operating Department for special steps (D)</p> Signup and view all the answers

When are the readings recorded for billing considered valid?

<p>When jointly recorded by both parties (D)</p> Signup and view all the answers

What might Supervisory officials suggest regarding the Supply Authority's network?

<p>Implement changes to improve power supply reliability (B)</p> Signup and view all the answers

What is laid down jointly with the Accounts Department in relation to bill scrutiny?

<p>A time schedule for scrutiny and passing of the bill (C)</p> Signup and view all the answers

What does the term 'penal charges' refer to in the context of bill scrutiny?

<p>Additional charges for late payments (C)</p> Signup and view all the answers

What should be done to prevent the recurrence of penal charges?

<p>Take appropriate remedial measures during scrutiny (A)</p> Signup and view all the answers

What is a key consideration when selecting kVAr ratings for power factor improvement capacitors?

<p>The guidelines issued by RDSO (B)</p> Signup and view all the answers

Which of the following should NOT be checked prior to passing bills from the Supply Authorities?

<p>The historical performance of traction equipment (C)</p> Signup and view all the answers

In a scenario of significant departures in billing, what action is recommended?

<p>Pay the disputed amount under protest (C)</p> Signup and view all the answers

Which condition should be maintained concerning the average monthly power factor?

<p>It should remain as close to unity as feasible (C)</p> Signup and view all the answers

What is the priority in planning for power factor improvement at traction sub-stations?

<p>Sub-stations feeding large marshalling yards and facing penalties (A)</p> Signup and view all the answers

What principle should be accepted by Supply Authorities regarding maximum demand during emergency working?

<p>Ignore temporary increases in maximum demand. (A)</p> Signup and view all the answers

How should the tariff structure for electric traction be approached to reduce costs?

<p>Study the implications of various parameters of tariffs. (A)</p> Signup and view all the answers

What must the contract demand for each sub-station be related to?

<p>The anticipated maximum peak demand. (D)</p> Signup and view all the answers

What is the role of the Central Electricity Authority in relation to billing for traction power?

<p>To review maximum demand measurement methodology. (B)</p> Signup and view all the answers

What is indicated by variations in billing demand charges for electric traction?

<p>They are based on simultaneous maximum demand across sub-stations. (C)</p> Signup and view all the answers

What action is recommended if the electricity supply agreement has not been finalized?

<p>Take urgent action to finalize it without delay. (C)</p> Signup and view all the answers

Who is responsible for bearing the cost of the equipment required for implementing the new methodology for traction power charging?

<p>The Railways. (C)</p> Signup and view all the answers

What is the penalty mechanism prescribed if the power factor falls below a certain value?

<p>An additional charge per kVA of Maximum Demand (A)</p> Signup and view all the answers

Which component does NOT affect the computation of excess energy charges?

<p>Minimum Guarantee percentage (A)</p> Signup and view all the answers

What is typically defined as billing demand?

<p>A specific percentage of the actual Maximum Demand or Contract Demand, whichever is higher (B)</p> Signup and view all the answers

What element should be checked periodically with Supply Authorities regarding charges?

<p>Fuel Adjustment Charge accuracy (B)</p> Signup and view all the answers

In determining the Contract Demand, which condition must be considered to avoid penal charges?

<p>Reviewing and adjusting for future consumption forecasts (B)</p> Signup and view all the answers

If excess energy is computed, how is it typically calculated according to the given formula?

<p>TU multiplied by the ratio of 1 minus CD/MD (D)</p> Signup and view all the answers

What minimum return percentage on capital cost is typically guaranteed in agreements with SEBs?

<p>15 to 20% (B)</p> Signup and view all the answers

Which of the following does NOT feature in the careful consideration for energy bill reduction?

<p>Duration of electricity supply (A)</p> Signup and view all the answers

How might two sets of trivector meters influence Maximum Demand charges?

<p>The higher of the two readings is taken (B)</p> Signup and view all the answers

What should be the basis for billing when a second set of meters is provided at Railways' cost?

<p>The average readings of both sets of meters (A)</p> Signup and view all the answers

Who initiates the meter card and printomaxigraph chart reading for joint recording?

<p>Both parties' representatives (B)</p> Signup and view all the answers

Which of the following additional information is NOT typically collected during meter readings at grid substations?

<p>Future traffic movement forecasts (B)</p> Signup and view all the answers

What action should be taken if the billed amount exceeds actual energy consumption due to minimum charges?

<p>Raise the issue with CEE and the operating Department (A)</p> Signup and view all the answers

What is the main purpose of scrutinizing the Supply Authorities' bills in the Divisional office?

<p>To validate against the Agreement and tariff (B)</p> Signup and view all the answers

What is one of the key recommendations for ensuring prompt payment rebates regarding bill scrutiny?

<p>To establish a time schedule with Accounts Department (C)</p> Signup and view all the answers

What might supervisory officials suggest during their visits to grid substations?

<p>Implementing changes for improved supply reliability (B)</p> Signup and view all the answers

Which element is crucial for accepting readings for billing purposes?

<p>Joint recording of the meter readings (C)</p> Signup and view all the answers

What should be done in response to penal charges levied on bills?

<p>Review the charges for correctness and prevent recurrence (B)</p> Signup and view all the answers

Where should a notification be directed if there is an excess of penalties related to the actual energy consumption?

<p>To both CEE and the operating Department (A)</p> Signup and view all the answers

What is the maximum allowable total harmonic voltage distortion (Vt) at the point of supply?

<p>3% (D)</p> Signup and view all the answers

What is a potential consequence of setting the contract demand too high?

<p>Risk of penal charges (C)</p> Signup and view all the answers

When conducting harmonic analysis, what is the RMS value of the fundamental voltage denoted as?

<p>V (D)</p> Signup and view all the answers

What is the stipulated percentage for the individual harmonic distortion (Vn) limit?

<p>1% (D)</p> Signup and view all the answers

Why is it necessary to strike a balance between high and low contract demand?

<p>To avoid inadequate load factors and penal charges (B)</p> Signup and view all the answers

What should be conducted annually on the supply authority’s meter to ensure accuracy?

<p>Testing and certification (D)</p> Signup and view all the answers

What is the maximum average load factor stipulated for contracts?

<p>30% (C)</p> Signup and view all the answers

What does the formula for calculating total harmonic voltage distortion (Vt) involve?

<p>Sum of squares of all harmonic voltages divided by the fundamental (B)</p> Signup and view all the answers

Why should the rates charged for traction be periodically reviewed with the SEB?

<p>To maintain competitive rates compared to EHV tariff charges (C)</p> Signup and view all the answers

What factor could lead to failure in achieving the minimum average load factor?

<p>High frequency of heavy trains without passenger support (A)</p> Signup and view all the answers

Flashcards

Electric Traction Power Source

Single-phase 50 Hz power for electric trains comes from a step-down transformer connected to a 220/132/110/66 kV three-phase grid.

Traction Substation Feeders

Two-phase duplicate feeders deliver power to traction substations from the supply authority’s substation.

Power Supply Reliability

Ensuring continuous and dependable power for trains.

Power Supply Liaison

Maintaining communication between railway and power supply authorities.

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Voltage & Frequency Limits

Power supply voltage (25-27.5 kV) & frequency (48.5-51.5 Hz) must be maintained precisely to avoid traffic disruptions.

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Traction Load Priority

Traction power should have priority over other power demands. It should not be interrupted or reduced.

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Power Supply Interruptions Review

Divisions should regularly review power interruptions, determine root causes, and report to CEE (Central Electrical Engineer).

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Power Supply Agreement

A formal agreement between the railway and supply authority for electric traction power supply, necessary before power is used.

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Emergency Grid Supply

Using power from adjacent substations to maintain operation when one's supply fails.

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Shared Grid Transformer Electricity

Railways should be charged based on the simultaneous highest power demand in connected substations, instead of each substation separately.

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Electric Traction Energy Cost

A significant part of a railway's total operating and maintenance expenses.

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Varying Electricity Tariffs

Different state electricity boards use various pricing structures, from a simple flat rate to complex methods.

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Contract Demand

The agreed-upon maximum power demand for a substation, avoiding inflated or penalizing payments.

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Maximum Demand

The highest power consumption rate at a given time.

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SEB (State Electricity Boards)

State-level organizations managing electricity distribution in India.

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Simultaneous Maximum Demand

Highest power demand among connected substations at the same time.

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Notice Period for Contract Demand Change

The time period a party must give notice before changing the contract demand for a service, ideally 4-6 weeks.

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Maximum Demand (MD) Charge

A charge levied on the highest power demand (in kVA) used over a specific period (like a month).

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Energy Charge

A charge based on the total energy (in kWh) used.

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Fuel Adjustment Charge (FAC)

Price variations for fuel costs and fuel quality, factoring in fluctuations and standards over time.

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Low Power Factor Penalty

An extra charge levied when the power factor falls below a certain level.

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Billing Demand

A calculated demand value used for billing, usually based on a percentage of the contract demand or the actual maximum demand (whichever is higher).

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Excess Demand Charge

Higher charges for electricity usage exceeding the contract demand, even for a short period.

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Excess Energy Calculation

The calculation to determine the charges for exceeding the contract demand from total energy consumption.

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Contract Demand (CD)

The agreed-upon maximum power demand a user can demand from the electricity company, which affects charges.

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Minimum Guarantee

A minimum return on investment for the electricity supply company (estimated at 15-20% of capital costs).

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Bill Checking Instructions

Detailed guidelines for verifying bills from power suppliers, ensuring accuracy, and identifying potential issues.

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Power Factor Improvement

Methods to improve the power factor by using capacitors, aiming for unity and avoiding 'leading' power factor when correcting.

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When to Use Capacitors?

Capacitors are best used at substations with large marshalling yards, or where penalty for low power factor exists.

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Average Monthly Power Factor

The ratio of kWh and kVAh over a month, used to track power factor efficiency and identify potential issues.

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Pre-Planned Traction Supply Shut-Downs

Planning for traction power interruptions, leveraging duplicate feeders in substations for uninterrupted train service.

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Billing Procedure (Railways)

Average meter readings from multiple meters are used for billing unless otherwise specified in the agreement. Reading should be jointly recorded by representatives.

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Monthly Meter Reading

Jointly taken by Supply Authority and Railway representatives on an agreed date, including maximum demand reading.

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Additional Grid Data

During meter reading visits, the official should also collect data on daily maximum demand, power factor, load factor, voltage variations, and grid changes affecting traction power supply.

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Scrutinizing Bills

Bills should be thoroughly reviewed against the Power Agreement and tariff. Analyze to find rebates and address any penal charges.

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Agreement and Tariff

The basis for understanding electricity costs and how they are calculated.

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Prompt Payment Rebates

Discounts may be available for timely bill payments, carefully check them.

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Penal Charges

Charges levied for late or incorrect payments; ensure to resolve them.

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Minimum Charge Issue

If the minimum charge is higher than what actual usage warrants, notify stakeholders immediately to seek traffic reallocation.

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Joint Representatives

Representatives from both the Railway and Supply Authority collaborate during procedures.

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Power Reliability

Improve power supply to 100% reliability by identifying and proposing changes.

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Notice Period for Contract Demand

The time period a party must give notice before changing the agreed-upon maximum power demand. Preferably 4-6 weeks.

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Maximum Demand Charge

A fee based on the highest power demand used in a period. It's usually calculated per kVA per month.

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Penalty for Low Power Factor

An extra charge levied when the power factor falls below a specified level.

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Guaranteed Load Factor

A minimum average load factor (e.g., 30%) specified in some power contracts, ensuring a certain level of electricity consumption regardless of actual demand.

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Harmonics

Distortions in the sinusoidal waveform of AC power, caused by non-linear loads like electric trains.

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Harmonic Distortion Limits

The permissible levels of individual harmonic distortion (Vn) and total harmonic voltage distortion (Vt) at the point of supply, typically 1% and 3% respectively.

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Periodic Tariff Review

Regular assessment of the electrical traction tariffs charged by the Supply Authority, ensuring fairness and competitiveness with other consumers.

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Meter Reading & Testing

Regular verification of the accuracy of electricity meters used for billing, including yearly testing and potential certification if accuracy is questioned.

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Joint Meter Reading

A collaborative process where representatives from both Railway and Supply Authority jointly record meter readings and other important data.

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Meter Reading Procedure

Meter readings are taken jointly by Railway and Supply Authority representatives on an agreed date each month. Both parties initiate the meter card and printomaxigraph chart for maximum demand recording. Only jointly recorded readings are used for billing.

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Average Meter Readings

When multiple meters exist at a Railway substation, the billing is usually based on the average readings of the meters, unless stated differently in the agreement.

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Grid Data Collection

During meter reading visits, the supervisory official collects additional information like daily maximum demand, power factor, load factor, voltage variations, and grid changes relevant to traction power supply.

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Bill Scrutiny

Bills from the Supply Authority must be thoroughly checked in the Divisional office against the Agreement and tariff. This includes verifying rebates, analyzing penal charges, and taking corrective actions.

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Power Reliability Improvement

During meter reading visits, identify potential changes needed in the Supply Authority's network to ensure 100% reliable electricity supply for traction purposes.

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Joint Representatives Collaboration

Both the Railway and the Supply Authority have designated representatives who work together for procedures like meter reading, bill scrutiny, and agreement negotiations.

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Contract Demand Change Notice Period

A certain amount of prior notice, usually 4 to 6 weeks, needs to be given before changing the agreed-upon maximum power demand (contract demand)

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Study Notes

Power Supply for Traction

  • Single-phase 50 Hz power for electric traction is obtained from 220/132/110/66 kV extra high voltage 3-phase grid system via step-down transformers.
  • Duplicate feeders (only 2 phases) run from the supply authority's substation to the traction substation.
  • A schematic diagram of the traction substation and feeding arrangement is in Figure 1.01.
  • 25kV single-phase conventional system is used on Indian Railways.

Liaison with Power Supply Authorities

  • Regular meetings between Railway and Supply Authority officials at various levels are vital for consistent power supply.
  • Traction voltage (25 kV to 27.5 kV) at feeding posts and frequency (48.5 Hz to 51.5 Hz) must be maintained.
  • Traction load is treated as essential and shouldn't be disconnected, as agreed by most Supply Authorities.
  • Railway authorities should actively work with supply authorities to maintain these voltage and frequency levels.
  • Periodical reviews of power supply interruptions are essential.
  • A specific agreement must be in place between the Railway and Supply Authority before power supply for traction is established.

Tariff for Traction

  • Energy costs are a substantial part of traction operations. Tariffs vary from flat rates to complex structures, including parameters like maximum demand, energy use, and fuel adjustment.
  • Contract demand should be stipulated realistically, avoiding penalties related to exceeding or failing to meet the contract.
  • Shorter notice periods for altering contract demand are preferable.
  • Factors like maximum demand, energy charge (paisa/kWh), and fuel adjustment charge (FAC) significantly influence energy bills.

Power Factor Improvement

  • Installing power factor improvement capacitors at 25kV traction substation buses is crucial.
  • Prioritizing substations that feed large marshalling yards or have low power factor penalties in their tariffs.
  • Average monthly power factor calculation (kWh/kVAh) is essential. Ideally, keep power factor near unity.

Shut-Downs of Traction Supply

  • Duplicate EHV feeders at grid and traction substations owned by the railways are essential for continuous service.
  • Planning shut-downs well in advance is vital.
  • Notifying the Supply Authority of shut-downs is crucial, along with the reasons and expected durations.

Monthly Meter Readings

  • Meter readings should be taken jointly by supply authority and railway representatives each month.
  • Meter accuracy should be verified periodically. An agreed-upon procedure for meter testing and usage is essential.
  • Additional information like maximum demand, power factor, load factor, and voltage variation on interconnection should be documented.

Scrutiny of Bills

  • Supply authority's bills need careful scrutiny in the Divisional office.
  • A schedule should be established for bill review and payment to maximize rebates.
  • Any discrepancies or charges related to minimum charges should be promptly brought to relevant authorities' attention.
  • Accurate meter readings, tariff compliance, maximum demand calculations, and timeliness of payments should be verified when reviewing bills.

Statistical Data

  • Monthly energy consumption statistics (kWh), maximum demand (kVA), average power factor, and monthly average load factor are crucial.
  • Monthly payments for energy, maximum demand, meter rent, fuel surcharge, power factor surcharge, and any minimum guarantee load payments are required.
  • Information should be consolidated and presented to the relevant authorities.

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Description

This quiz explores the principles and practices of power supply for electric traction systems, specifically focusing on the high voltage supply and voltage regulation in Indian Railways. It addresses key collaborations between railway and power supply authorities to ensure consistent delivery of traction voltage and frequency. Test your knowledge on the technical aspects and operational protocols involved in maintaining effective power supply.

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