S U B S T A T I O N S
SCMSStray Current Monitoring System
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SCMS / STRAY CURRENT MONITORING SYSTEM
The operation of DC traction systems requires suitable measures to prevent corrosion caused by stray currents on railway and non-railway installations. In this scope, the European standard EN50122-2:2011 (Annex B) recommends a continuous supervision of the rail insulation. Sécheron Stray Current Monitoring System is a straightforward and efficient method of stray current monitoring avoiding manual repetitive measurement and any interference with the stray current collecting system. The system measures continuously the rail-to-earth potential under operational conditions, complete with central analysis, visualization, signaling and archiving capacities.
The stray currents are defined as the currents that has deviated from their intended paths.Any metallic structures, for examples a pipe line, buried in soil represents a low resistance current path and is therefore fundamentally vulnerable to the effects of stray currents.1 ampere of stray current can oxidize 9.11 kilograms of iron per year.
As the return is floating, the potential between earth and rails fluctuates.
Stray current definition
Principle of Stray Current Monitoring in floating case
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A healthy system’s presents a specific voltage profile called ‘’reference’’ or ‘’imprint’.A deficiency of insulation between the rail and the earth will modify this voltage distribution.The track potential can be used to ensure the healthy of the insulation and determine a modification in behavior of the stray current by comparison with the reference curves.
Based on a rail potential measure.
Advantages:•Measure more simple and practical•No interference with Stray Current Collecting System•Best arrangement to limit level of stray current
Disadvantages:•Relative and indirect measure•Dependent of the line operation (trains, headway, TSS out)•The line must be certified healthy and compliant with
the requirements of the standard before the reference recording.
Architecture
The Stray Current Monitoring System (SCMS) continuously collects voltage data between the return circuit and the earth structure along the line. The potential value is measured through the Voltage Limiting Device (VLD).
The SCMS includes the following functions:• Set up of network lines & stations, up to 10 lines and 60 control points• Data acquisition and transmission through the communication network• Determination on data reference• Integration of specific algorithm depending on type of network• Supervision of status of VLD at all stations and alarm if the device has operated• Permanent automatic analysis of recorded values, realized by the Central Evaluation Unit plus alarm in case stray current
increases • Localization of the detected fault• Manual analysis of recorded values possible• Archiving of the measured values into CEU• Export of the measured and recorded values• Communication with SCADA system
The SCMS can adapt to either an existing or a new network.
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SCMS / STRAY CURRENT MONITORING SYSTEM
Central Evaluation Unit (CEU)
Functions of SCMS are performed at the CEU. The CEU includes an interface program to plot the real-time data being captured by the SCMS, as well as the data stored in the database. This interface program also allows the user to visualize the data in different ways, export the plotted data, perform various manual analyses of stored data and to parameter the SCMS.
The CEU is designed with enough memory to keep at least 16 weeks of instantaneous values and archiving average values for 10 years. Stored data at the CEU is safely kept in a redundant RAID-1 hard drive system. The data can be exported to text files. The CEU communicates with the network and SCADA system through different types of communication protocols: IEC61850, IEC60870-5-104 (-5-101), Modbus-TCP, DNP3.0 with flexible connectivity (copper cable RJ45, optical fiber).
Measure
Maximum number of lines 10
Maximum number of measuring points Min. 60 for one system
Frequency of acquisition 1 sec
Communication
Communication protocol Standard fieldbus protocol
Visualization and archiving
Instantaneous values • In function of time• Last 16 weeks
Short analysis values • Average values / Average of the absolute value• In function of time or position• Average window from 1 to 60 min• Archiving for 10 years min
Long analysis values • Average values / Average of the absolute value• In function of time or position• Average window from 1 to 30 days• Archiving for 10 years min
Total memory size 1 TB
Available languages English
Histogram of the operation number of the contactor
Analysis
Number of acquisition for the reference profile 10 most relevant measurements
Number of acquisition (global) All points for 16 weeksMean values saved for 10 years
Daily recording period Adjustable
Alarm and event management
Overview of the line Alarms list
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Representation in function of location• Typical values of the line potential during operation (digital imprint)• Reference the localization of the insulation deficiency
Representation in function of time• The short term values allows the analysis of insulation deficiency• The long term values allows the analysis of tendency
At the end of each day, the software generates automatically an analysis file of the data recorded during the day and saved it as csv files.
The analysis window allows having access to the history files and to generate a pdf report.
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SCMS / STRAY CURRENT MONITORING SYSTEM
Measurement and certification of track
Before the recording of the reference data, Sécheron can provide the service of its earthing and bonding experts for the certification of the track. This expertise allows checks if the installation meets the characteristics defined in the standard EN50122-2: 2010:
• Rail resistance measure
• Conductance per length between running rails and structures
• Insulating rail joints certification
• Stray current interference of reinforced concrete structures
• Stray current emission
• Expertise and recommendation
• Training of personal
• Assistance with reference data recording
• Parameterization support
The variation of the structure potential can be considered as null and so compliant with the requirement of EN50122-2 (<200mV).
Project Start
Time
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Earthing and bonding engineering service
Certificate of Rail Insulation Joint
Certificate of trackwork (rail insulation)
Simulation of rail – earth potential
Reference recording phase
Definition of protection settings
Monitoring for maintenance (test interval)
Training to control the conductance betweenearth and rails before welding
Certificate of structure potential changeless than 200 mV
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Data collection from VLD
How to manage stray current?
The Stray Current Monitoring System (SCMS) continuously collects datas from the Voltage Limiting Device (VLD) along the line:• voltage between the return circuit and the earth structure through a high accuracy sensor,• potential current flowing in the VLD through a high accuracy sensor,• VLD status.
• Floating negative return (ungrounded)• Traction substation close to passenger station• Traction substations reasonably spaced• Continuously welded rail• Track slab rebar electrically continuous (“stray current
collector”)• High resistivity concrete for track slab, e.g. silica fume
additive• Depot electrically isolated from the mainline• Relocated utilities designed with stray current control
provisions• High track to earth resistance
PLC PLCPLC
BUS
VA
VA
VA
VLD VLD VLD
STRAY CURRENTSMONITORING SYSTEM
VLD
Sécheron SA Rue du Pré-Bouvier 251217 Meyrin - GenevaCH-Switzerland
Tel: +41 (0)22 739 41 11Fax: +41 (0)22 739 48 [email protected]
This document is not contractual and contains information corresponding to the level of technology at the date of printing. Sécheron reserves the right to modify and/or improve the product, whose characteristics are described in these documents, as required by new technology at any time. It is the purchaser’s responsibility to inform himself, no matter what the circumstances, of the product’s
maintenance conditions and requirements. Sécheron reserves all rights, especially those arising from our “General Delivery Conditions”.
Copyright© 2007 Sécheron SA
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