Good grounding is more than a safety measure—it not only prevents damage to railway equipment but ensures the safety of passengers and railway personnel working on tracks. National Electric Code (NEC) defines grounding as “a conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth or to somebody that serves in place of the earth.”
Studies reveal that electrical faults and improper grounding are two prime causes of downtime and revenue loss in the rail industry. These faults are responsible for the costs associated with litigation, loss of property, personal and corporate productivity. A railway earthing shall include the design of the entire earth-termination system for all structural components of the railway infrastructure to protect people in the railway environment and ensure reliable rail traffic.
The concept of Earth Grounding has two subjects:
These two grounding systems are distinct and shall be kept separate, except for a connection between the two systems. This avoids differences in voltage potential from a possible flashover from lightning strikes. Besides system and equipment grounding, two additional earthing systems are used for railway and traction systems – Mobile traction system earthing and Securing rail operations through earthing.
The following standards, codes, and guidelines are to be complied with when designing and implementing the grounding of communications equipment, including but not necessarily limited to:
Ground finders are digital multimeters widely used by railway personnel to detect ground resistance and standardize the testing for grounds required by FRA (Federal Railroad Administration, Department Of Transportation) Rules No. 234.249 and 236.107.
Over time, due to percolation of rainwater, high salinity or corrosive soils, and raised temperatures can degrade ground rods and their connections. Despite the low earth ground resistance values during initial installation, these values can increase if the ground rods are eaten away due to corrosion.
Like the S&C’s Model 360 Ground Finder, Grounding testers are indispensable railroad ground troubleshooting tools to maintain uptime. Often, frustrating and intermittent electrical problems could be related to poor grounding or poor power quality.
All grounds and ground connections of railway applications must be checked at least annually as a part of a preventative maintenance plan. While performing the checks, a 20% increase in resistance should be checked. If the rise in resistance is identified, the rods should be replaced, or additional ground rods should be added to the system.
Ground Finder – Measurement Procedure:
Step 1- TEST mode: The device alarms (Red LED, beeper) activate when the maintainer encounters aground. For safety and to allow testing under traffic, the output current is limited to less than 1.0mA in the “TEST” mode.
Step 2 – CONFIRM Mode: Upon ground indication, the maintainer must have track and time (TOP) clearance to switch the tester to the “CONFIRM” mode before verifying that his ground is reportable.
Step 3 – POLARITY Test: Once he has determined that it is safe to switch the Model 360, a quick test in the “CONFIRM” mode tells him the ground value up to 10.0mA (meter full-scale).
Ground finders are similar to a milliohm meter; however, these are capable of testing higher resistances, as required for railway applications. Calibrating ground finders at regular intervals is essential for the following reasons:
Though Ground resistance measurements using ground finders seem straightforward, the equipment needs to be calibrated and maintained following OEM SOPs. To comply with international standards, the repeatability and accuracy of ground finders should be maintained by following an annual calibration process.
Calibration of ground finders also determines the calibration uncertainty value and the deviation from the actual reading. These readings are used as correction factors or to decide if the ground
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