It’s critical for rail signalling systems to have consistent and reliable power supply, to ensure safe and normal running of operations, including level crossings, signal lights, point machine operations and interlocking systems.
These signalling systems are normally connected to the railway’s internal electrical network. However, power supplies are prone to disruption, whether by lightning strikes, equipment failure or accidents.
To ensure the reliability of supply to critical loads, a backup supply is normally provided.
Subsequently, when a failure of the normal supply occurs, the load is transferred to a backup or emergency supply, thus ensuring connected loads continue operating normally.
The emergency supply is typically sourced from the local electric utility, primarily from nearby street mains services.
CHKPQ’s Miro ECO Supply Monitor and Logger can facilitate the transfer of supply, intelligently and quickly (see figure on top).
The key features of the Miro ECO Supply Monitor and Logger include:
• Fast switching time
• Monitoring of Emergency supply
• Data logging
• User selectable changeover criteria, THD, undervoltage, and overvoltage
• Prevention of nuisance and repetitive switching operations
The Miro ECO Supply Monitor and Logger instrument can transfer supply in about 25ms to 56ms (depending on configuration and type of contactor).
This short transition time ensures downstream equipment continue operating normally. Most signalling and IT equipment are ‘hardened’ to tolerate short interruptions of supply, making the Miro ECO an ideal solution, compared to UPS (Uninterruptible Power Supply) systems, which can be expensive to purchase and maintain.
Typical change over schemes can take more than 100ms to detect abnormal conditions and transfer supply.
This lengthy transfer time often causes connected loads to malfunction or switch off, causing disruptions to downstream loads (e.g., signalling systems), and subsequently train operations.
The Miro ECO monitors and ensures the alternative supply is within acceptable limits before transferring supply.
The Miro ECO is also a power quality logger and analyser and has user-settable thresholds.
The Miro ECO captures all relevant power quality data, including supply changeovers and voltage deviations. The data can then be used to analyse these events to determine the details of the changeover and possible causes.
CHK PQ Sales Director, Johnson Mariswamy, said the Miro ECO instrument is an intelligent device that prevents nuisance and repetitive switching operations by progressively delaying switchback times.
“All data can be collected and analysed using proprietary Citrus software or AsMoSys (Asset Monitoring System), a database solution created by CHK,” he said.
“AsMoSys is a tool to help manage and review Miro log data. The AsMoSys solution can be set up to create alarms and notify users via email, when a changeover occurs or when set thresholds e.g., THD (Total Harmonic Distortion) are exceeded.”
Various reports, for example, supply availability, supply quality and frequency of changeovers, are available for analysis.
AsMoSys can be used to poll multiple Miro ECO units via remote cellular communications, or optional Ethernet, both which allow remote connection to the instrument to view real time measurements, data download and reconfiguration of the instrument.
The Miro ECO instrument currently comes in two versions:
• The Miro ECO-Block, with a relay output of 0.125A, capable of driving contactors rated up to 80A, e.g., block contactors.
• The Miro ECO-Bar, with a solid-state relay (SSR) output of 2A, capable of driving contactors rated up to 250A, e.g., bar contactors. Single and three phase versions are available.
“Pluggable terminal blocks and compact iron core current sensors, as well as magnetic feet, also make for easy and quick installation,” Mariswamy said.
The Miro ECO can be used for any application where a rapid circuit changeover is required including railway signalling equipment, hospital backup supplies and data centre redundant supply schemes.
CHK Power Quality specialises in power quality and asset condition monitoring products and services, providing the necessary data and analysis tools to help customers identify and resolve issues to increase the reliability of plant and equipment, thereby reducing capital and operating costs.
CHK PQ has developed partnerships with railway companies to design and develop new products, such as the transfer switch controller described above, and point condition monitors.
“We aim to enable customers to improve the power quality and asset monitoring of their power networks utilising innovative and modern technologies,” Mariswamy said.