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Questions and Answers
What is the primary function of a Protective Earth?
What is the primary function of a Protective Earth?
Where should the Bonding Ring Conductor (BRC) be connected if it exists?
Where should the Bonding Ring Conductor (BRC) be connected if it exists?
Which of the following is NOT a purpose of earthing?
Which of the following is NOT a purpose of earthing?
Where should earthing be provided according to the guidelines?
Where should earthing be provided according to the guidelines?
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What is the maximum earth resistance specified by?
What is the maximum earth resistance specified by?
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What should be done if no Bonding Ring Conductor (BRC) exists?
What should be done if no Bonding Ring Conductor (BRC) exists?
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What type of earth is specifically used for conducting current during normal operation?
What type of earth is specifically used for conducting current during normal operation?
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Which of the following locations is NOT required to have an earthing provision?
Which of the following locations is NOT required to have an earthing provision?
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When is it necessary to earth the armouring of unscreened cables used as tail cables?
When is it necessary to earth the armouring of unscreened cables used as tail cables?
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What is the maximum permissible earth resistance for modern electronic equipment used in the relay room?
What is the maximum permissible earth resistance for modern electronic equipment used in the relay room?
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What color is recommended for earthing wires to facilitate quick identification of a loose or disconnected wire?
What color is recommended for earthing wires to facilitate quick identification of a loose or disconnected wire?
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What should be done if the resistance of earth for signalling circuits exceeds the prescribed value?
What should be done if the resistance of earth for signalling circuits exceeds the prescribed value?
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What is the recommended minimum cross-section for earth wires to ensure adequate current carrying capacity?
What is the recommended minimum cross-section for earth wires to ensure adequate current carrying capacity?
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What should be ensured regarding the arrangement of earth wires?
What should be ensured regarding the arrangement of earth wires?
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What is the preferred material for the earthing lead?
What is the preferred material for the earthing lead?
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Which of the following must be connected to a common earth to avoid simultaneous contact with different earths?
Which of the following must be connected to a common earth to avoid simultaneous contact with different earths?
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Which site is least preferred for earthing according to the given guidelines?
Which site is least preferred for earthing according to the given guidelines?
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What distance criterion should be followed when using more than one earth electrode?
What distance criterion should be followed when using more than one earth electrode?
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What method is preferred for connecting the earthing lead to the earth electrode?
What method is preferred for connecting the earthing lead to the earth electrode?
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What can be added to improve soil conductivity when it is poor?
What can be added to improve soil conductivity when it is poor?
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Which of the following is NOT a recommended soil condition for earthing?
Which of the following is NOT a recommended soil condition for earthing?
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Which practice is recommended for preparing soil around earthing electrodes?
Which practice is recommended for preparing soil around earthing electrodes?
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What is the maximum recommended amount of salt to be added for effective soil treatment?
What is the maximum recommended amount of salt to be added for effective soil treatment?
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What type of paint should be used on the nut and bolt of the earthing lead connection?
What type of paint should be used on the nut and bolt of the earthing lead connection?
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What is the recommended depth for driving electrodes into the ground during testing?
What is the recommended depth for driving electrodes into the ground during testing?
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How often should block earths and their connections be examined by JE (Signals)?
How often should block earths and their connections be examined by JE (Signals)?
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Which method is suitable for measuring small earthing systems like a single electrode?
Which method is suitable for measuring small earthing systems like a single electrode?
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What should be done to enhance the effectiveness of maintenance-free earth systems?
What should be done to enhance the effectiveness of maintenance-free earth systems?
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What equipment is connected to the electrodes during the testing process?
What equipment is connected to the electrodes during the testing process?
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What is the typical crank speed for a Magneto Generator Type megger when taking readings?
What is the typical crank speed for a Magneto Generator Type megger when taking readings?
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Which of the following best describes how the resistivity is calculated in the testing procedure?
Which of the following best describes how the resistivity is calculated in the testing procedure?
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What should be done to maintain earth connections according to the maintenance guidelines?
What should be done to maintain earth connections according to the maintenance guidelines?
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What is the minimum recommended distance between equipment earths and system earths?
What is the minimum recommended distance between equipment earths and system earths?
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Which material is recommended for standard electrode systems under ordinary soil conditions?
Which material is recommended for standard electrode systems under ordinary soil conditions?
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What primarily determines the earth resistance in an earthing system?
What primarily determines the earth resistance in an earthing system?
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What thickness of asphalt or concrete cover is recommended around the earth?
What thickness of asphalt or concrete cover is recommended around the earth?
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What is the equation used to evaluate the resistivity of soil using a megger?
What is the equation used to evaluate the resistivity of soil using a megger?
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What should electrodes be free from to ensure proper functioning?
What should electrodes be free from to ensure proper functioning?
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Which type of electrode is preferable in areas with excessive soil corrosion?
Which type of electrode is preferable in areas with excessive soil corrosion?
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What is the effect of using made-up soil that has not consolidated or is prone to erosion for earthing arrangements?
What is the effect of using made-up soil that has not consolidated or is prone to erosion for earthing arrangements?
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Study Notes
Earthing for Outdoor Signaling Equipment
- Earthing is crucial for block instruments and surge protection. Two types exist: functional (conducts current during normal operation) and protective (dissipates surges).
- Perimeter Ring Earths (PRE) are required around equipment housings.
- Equipment chassis are bonded to a Bonding Ring Conductor (BRC), which connects to a Main Equi-potential Earth Busbar (MEEB). If no BRC exists, equipment chassis directly connect to the MEEB.
- Earthing specifications follow RDSO (Rail Development Systems Organisation) guidelines. Maximum earth resistance is determined by OEM and RDSO recommendations.
- Earthing is crucial for lightning/surge protection, reducing electromagnetic interference, and ensuring safe human interaction.
Purpose of Earthing
- Earthing protects equipment, buildings, and structures from lightning and surges.
- Earthing reduces electromagnetic interference, particularly for telecommunications cables and equipment.
- Ensuring human safety is prioritized in an earthing system.
Earthing Requirements
- Metallic frames of cabins need earthing.
- Earthing points are located at every cable termination point.
- Earthing points are provided for every signal.
- Common earthing systems are established for close location boxes or signal posts.
- Separate earth connections exist for equipment requiring functional earthing.
Earthing of Main Cables
- Main cable sheaths and armouring are earthed at both ends. Armouring doesn't require earthing if tail cable lengths meet prescribed limits.
- Signals close to electrified tracks require protection screens to be earthed.
- Metallic connections must be connected to a single common earth, if separating them isn't possible.
- Common/equi-potential earthing is recommended for modern electronic equipment. The value of earth will be no more than one ohm and should be measured annually during the dry season.
Earthing Wire Specifications
- Distinctive green or green-yellow (GNYE) color signifies earthing wires.
- Earthing wires should be straight and not coiled.
- Earthing wires need adequate current carrying capacity. Minimum copper cross-section should be 4 sq mm.
- Earth resistance up to 10 ohms is normally permissible for protective earth, but for electronic equipment, it must be less than or equal to one ohm.
Earthing for Blocks and Equipment
- Dedicated earthing provisions are required for each block instrument and other signalling equipment.
- Earthing arrangements must be individually provided for earth return circuits.
- Earth resistance should not exceed 10 ohms, or as per OEM/RDSO specifications.
Selecting Earthing Sites
- Sites are prioritized as follows: wet marshy/waste ground, clay soil, loam, and wet sand.
- Optimal choice involves natural well-drained locations.
- Soil should be fine textured and tightly packed. Any lumps/stones/rock are removed from the site prior to earthing installation.
- Chemical treatments can improve poor soil conductivity.
Earthing Resistance Measurement
- Earth resistance results from the combined effects of conductor connections, soil contact, and surrounding soil.
- Standard corrosion-resistant materials (galvanized iron or mild steel, copper or copper-clad steel) are recommended for earth electrodes.
- Resistance will primarily depend on soil type, not electrode itself.
- Earth testers with current sources and multimeters measure Earth resistance directly.
Four-Terminal Megger Method
- Methods are used to measure earth resistivity. An equation exists for calculating the resistivity from the megger readings and the distance between successive electrodes.
Earth Maintenance
- Regular watering and material replenishment can improve earth resistance.
- Earthing connections need regular checks and maintenance to ensure their integrity.
Regular Checks and Upkeep
- Electrical inspections of block connections and relevant wire connections must be carried out regularly to ensure proper performance of the earthing system.
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Description
This quiz explores the crucial aspects of earthing in outdoor signaling equipment, highlighting functional and protective earthing types. It covers the requirements for Perimeter Ring Earths, Bonding Ring Conductors, and main earthing busbars according to RDSO guidelines. Understand the significance of earthing for surge protection and electromagnetic interference reduction.
