Signaling Circuits in Electrified Zones

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Questions and Answers

What is the maximum permitted length for an unscreened direct feed of a signal on a single track?

180 m (correct)

200 m

250 m

220 m

How should signals located beyond the prescribed distance be supplied?

By using longer cables

By remote monitoring systems only

By battery backup systems

By local controlling relays (correct)

What is required for the electric operation of a point?

Batteries for uninterrupted power

DC relay for better reliability

Manual switches for emergency control

AC-immunized relay for point detection (correct)

What must be ensured about the power transformers feeding circuits according to the guidelines?

They should be different for longer circuits Signup and view all the answers

What is the purpose of specifying a distance limit between signal control relays and the signal?

To ensure adequate voltage for lamplight Signup and view all the answers

What is the maximum length permitted for a signalling line circuit to prevent the induced voltage from exceeding its limit?

2.1 km Signup and view all the answers

What is the induced voltage per kilometre for an underground unscreened cable on a single line under normal conditions?

116 Volts/km Signup and view all the answers

Which type of relay has a maximum permissible length of 1.0 km on a double line?

K50 B1 Signup and view all the answers

What additional safety factor is considered when determining the maximum permissible induced voltage?

1.5 Signup and view all the answers

What is the specification for the signal feed system in the RE area?

110 V 50 Hz Signup and view all the answers

For the K50 relay on a single line, what is the maximum permissible length of the circuit?

900 meters Signup and view all the answers

What is the immunity level for the K50 B1-A2 relay?

450 Volts Signup and view all the answers

In the event of high induced voltage, what should be done to the line circuits?

Sectionalize the line circuits Signup and view all the answers

What should be ensured if the distance between two insulators on the same rod exceeds 300 meters?

Additional insulators must be provided. Signup and view all the answers

How far must the top of a rod be from the bottom of the rail when it crosses the track?

40 mm Signup and view all the answers

What is required for each Point, Trap indicator and lock bar operated by rodding?

They must be electrically isolated from the track. Signup and view all the answers

Which statement about the clearance between the insulator and the adjacent rod roller is correct?

It must be sufficient for normal movement of the rod. Signup and view all the answers

When the Engineering department provides the point lever or point box, what should they also provide?

An insulator on the operating rod. Signup and view all the answers

What is the maximum induced voltage limit prescribed for block wires near electrified tracks?

60 volts Signup and view all the answers

Which of the following equipment should not be used in external circuits in AC electrified areas?

Luminous Indicators Signup and view all the answers

In AC electrified territory, which type of circuit is strictly prohibited aside from barring block-instrument circuits?

Earth-return circuits Signup and view all the answers

What type of insulation is required for the batteries and wiring in location boxes or cabins?

PVC insulation Signup and view all the answers

In cases where multiple cables are laid between two locations, what is the ideal practice?

Ensure all wires of an individual circuit are within the same cable Signup and view all the answers

What is the recommended time delay for slow-acting relays that release an interlocking?

0.6 to 0.8 seconds Signup and view all the answers

Why should polarized relays using permanent magnets not be used in external circuits in 25 KV AC electrified areas?

They lose their magnetic properties due to induced voltages Signup and view all the answers

What type of circuits must all external circuits in AC electrified areas utilize?

Double cutting Signup and view all the answers

What is the maximum permissible parallelism for a point machine with an AC immunity level of 160 volts on a double line?

1100 meters Signup and view all the answers

What factor of safety is specified for point machines?

1.5 Signup and view all the answers

Why must insulators be provided on the rodding in A.C electrified areas?

To protect staff from induced voltage Signup and view all the answers

Which of the following configurations requires an insulator according to the specified requirements?

Additional insulator between crank and point Signup and view all the answers

At what AC immunity level does the maximum permissible parallelism on a single line reach 2200 meters?

400 volts Signup and view all the answers

What is a unique feature of a 3 phase point machine regarding induced voltage?

It is inherently immune to induced voltages. Signup and view all the answers

What precaution should be taken to ensure no contact occurs between insulated and un-insulated portions of rods or signal wires?

Use insulators as per approved drawings Signup and view all the answers

What is the maximum permissible length for a point machine with an AC immunity level of 400 volts on a double line?

2800 meters Signup and view all the answers

Study Notes

Section 4: Signaling Circuits in RE Area

No aerial circuits allowed in electrified zones.
Length of parallelism and Block Wire distance must prevent induced voltage exceeding 60 volts (CCITT limits).
Barring block-instrument circuits, no other earth-return circuits are permitted in AC electrified areas.
Block instruments must have a filter (Chapter 18 of SEM).
Some electrical signaling equipment (e.g., luminous indicators, telephone relays, electrical lever locks, door coils of IRS block instruments, 250 Ohm DC neutral line relays, rotary key transmitters, DC neutral polar relays) are unsafe for use outside cabins/location boxes due to AC voltage induction.
These equipment must be powered by separate battery/DC-DC converters not connected to external circuits.
Batteries and wiring in equipment, boxes, or cabins must be well insulated from the ground using PVC insulated wires (IRS-S-76).
Separate battery/DC-DC converters are required for internal and external circuits.
Wires in cables between locations should be grouped within the same cable.
Polarized relays with permanent magnets are not permitted in 25 kV AC electrified areas because magnets may lose their properties.
Relays used for interlocking must be slow-acting (0.6-0.8 seconds) so they don't release unintentionally due to short-duration voltage variations.
All external circuits in AC electrified areas must use double cutting.

Section 5: Outdoor Signaling Circuits in RE Area

Signalling line circuit length should not exceed limits to prevent induced voltage exceeding 400 volts (normal conditions).
The line circuit needs to be sectionalized if necessary.
If line circuits leave enclosures or buildings in various directions, a sectionalized power supply unit should be provided for each direction.
In underground, unscreened cables, induced voltage is 116V/km for single line and 95V/km for double line under normal conditions. This is calculated at 800A for single line, and 1000A for double line current of the catenary.
Circuit immunity when terminated at relays/equipment must be > 400V AC.
DC circuit length on line relays with unscreened cable should be limited.
Various relay types have different maximum permissible lengths (single and double line).

Section 6: Signal Feed Circuitry in RE Area

Signal feed systems use 110 V 50 Hz or similar approved type.
Distance between signal control relays and signals must not exceed prescribed limits in electrified zones, measured along the line of way.
Appropriate circuit design ensures inadequate voltage for safe operation, even with multiple or severe ground faults.

Section 7: Point Operation & Detection in RE Area

Points can be operated electrically or mechanically (with protection measures).
Maximum length between point control relays and point machines depends on immunity levels.
AC-immunized relays are required for point detection and repeat circuits.
Maximum permissible parallelism for point machines varies depending on type and voltage rating. This applies to both single and double line types.
Three-phase point machines are naturally immune to induced voltage and can be used for point operation over any length.

Section 7: Rod Runs in RE Area

Point rods are subject to induced voltage, even more so in AC electrified areas.
Safe operation requires insulators on rods to protect operating staff.
Insulated rod joints are specified by approved drawings with added insulators at critical locations like near cabins and when the distance between two insulators is greater than 300 meters.
Insulators should prevent contact between insulated and non-insulated parts.
Clearance for rod movement and safety distances (minimum 40mm) need to be maintained.

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Description

This quiz covers the regulations and specifications of signaling circuits in electrified zones, focusing on safety measures, equipment use, and wiring requirements. Participants will learn about the limitations of AC voltages and the importance of insulation for safe operations. Engage with the guidelines to ensure compliance and safety in signaling operations.