sensortran technology brief mar11

7/27/2019 Sensortran Technology Brief Mar11

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SensorTran Technology Brief

Smart Grid

SensorTran Technology Brief: Smart Grid

The Role of Distributed Temperature Sensing (DTS) in Smart Grid Implementation

Smart Grid and DTS

As electric utilities across North America, Europe,and the world begin to implement Smart Gridtechnologies, there is a growing need forcomplementary monitoring tools. Initial Smart Gridefforts are focused on the nodes of the system -primarily the management of power generationand storage elements. However, with the shiftfrom distant to localized renewable powergeneration and the need for the grid to acceptpower injections from all energy resources, the

reliability, efficiency, and capacity of the cablesconnecting the nodes is core to realizing thebenefits of Smart Grid. The retooling of theelectricity infrastructure in major markets is likelyto occur over a span of 20 30 years. Such alarge changeover comes with a unique set ofchallenges such as standardization oftechnologies and protocols, synchronization ofcross-border regulations, and major decisionsregarding interfaces between old and newsystems. Continuous, cost-effective monitoring ofthese interfaces within the new grid structure areessential to the successful implementation of

Smart Grid.

The Smart Grid initiative is a major undertakingthat the European Commission Directorate-General for Research has compared to the leapthe Internet has made into the Web 2.0 age. In asimilar manner that Web 2.0 features user-generated content, Smart Grid features user-generated power. As power begins to movethroughout the grid in bi-directional flows, itbecomes more important to actively monitor allthe power cables not just the EHV transmissionlines at the core of the traditional grid system.DTS technology is perfectly suited for power cablemonitoring, as it enables continuous, precise, andaccurate temperature measurements to be rapidlyand dynamically collected across distancestypically in the range of 1 to 15km with 0.5msampling resolution, 0.1C temperature resolution,and accuracy within +/-1C.

For power cable monitoring, DTS offers two levelsof load characterization when combined with real-time Cable Ampacity Analysis Software (CAAS) one showing actual (real-time) conditions and theother predicting future conditions (based onpossible loads).

First, by continuously monitoring the cablesthemselves, temperature events (hot spots, cabledamage, over current conditions, etc.) are easily

identified reducing the risk of failures associatedwith operating above the cables specifiedmaximum temperature (e.g. 70C). Because thetemperature is measured directly, rather thanestimated based on load and environmentalconditions, the usable capacity in monitored linesis maximized. Utilities today use conservativemathematical models to estimate the cabletemperature for given load conditions building ina factor of safety to ensure the cable does notoverheat. While these models are effective atprotecting the cables from failure, they areineffective at maximizing the usable capacity of

the circuit. As a result of deploying DTS-based,real-time dynamic monitoring, the cablestemperature is empirically, rather thantheoretically, obtained, allowing for operation ofthe cable closer to its maximum capacity.Maximum capacity results in maximum flexibility which is key to realization of Smart Grid.

The second level uses DTS to make predictions offuture conditions based on various load scenarios.This is accomplished by using dense temperaturedata collected over short measurement times toestimate the heat transfer characteristics of thecable.

What DTS Means to the GridIn summary, DTS is a key Smart Gridinfrastructure technology that enables:

Maximization of usable capacity of thecircuit


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Ability to cost-effectively monitor all powercables from EHV down to LV

Active management of loads with little risk ofover-temperature failures

Predictive Ampacity estimation using actual

temperature data inputs with CAAS

How DTS WorksSingle laser DTS systems use the light sourcefrom a single laser to record temperature traces,deriving the temperature information from twobackscattered signals that operate at two differentwavelengths. One of those wavelengthsrepresents the Raman Stokes signal, and theother represents the Raman anti-Stokes signal.See image below for reference.

Given that the intensity of the optical signalexponentially decays as a function of distance,single laser DTS systems are calibrated utilizingan exponent called Differential Attenuation Factor

(DAF). DAF is the difference in attenuationbetween Stokes and anti-Stokes wavelengths,and it is typically determined by the fiber material.When multiplied by the Stokes, DAF serves as acorrection factor to match the attenuation profile tothat of the anti-Stokes signal. Temperature is thenderived by taking the ratio of the two signals.

Early installations of DTS for power cablemonitoring have been focused on the identificationof problem areas and hot spots. With Smart Gridimplementations however, DTS serves a criticalinfrastructure role in load management. With the

ability to implement DTS monitoring solutions foras low as $10/meter, it is now possible for utilitiesto obtain and use real-time dynamic temperaturemeasurements across all circuits. With theinjection of renewable energy and consumer-generated surplus power into the system, it iscritical to control variable bi-directional flows ofcurrent in order to ensure efficient, failure-free

Smart Grid operation. Using DTS, utilities will beable to closely manage load balancing usingactual rather than calculated temperature data.

DTS Software

Data integration and communications functionalityare other important components of Smart Gridimplementations. SensorTran DTS systems areavailable with a comprehensive Software Suitecomprised of three main applications:

SensorTran DTS Commander for setting up,calibrating, and managing the DTS system

SensorTran AssetViewer for advancedgraphical asset visualizations

SensorTran Cable Ampacity Analysis

Software (CAAS) for cable ampacitycalculations and on-line query tools

This advanced suite of software tools enablesusers to collect, display, interpret, analyze,manage, and integrate DTS data from multipleunits

DTS InstallationRecent technological advances in DTS technologyhave greatly reduced the time, energy, andexpertise required to successfully deployadvanced fiber optic-based monitoring systems.

These advances are based on three SensorTranproprietary components: PERFECTVISION

,

Calibration Modules, and DTS Commander.These components combine to provide DTSsystems which are easy to calibrate, andperiodically verify that calibration is accuratebased on installed conditions of the fiber and itssurroundings/environment change. This hasgreatly simplified management of DTS, enablingfield crews to set up and operate the systemwithout needing to involve highly skilledtechnicians. Operators of the system can definezones and set alarms through the control panel onthe SensorTran DTS Commander. Afterconfiguration, the system will alert the operatorimmediately when pre-specified temperaturethresholds are approached and/or crossed.

PERFECTVISION

technology is a proprietary dual lasersolution developed by SensorTran which accounts for non-uniform optical losses in fiber probes, enabling calibration andviewing of backscattered light even in damaged or stress-darkened fiber.


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The SensorTran AssetViewer (example shownabove) provides the ability to view temperatureand alarm information mapped to the actual assetbeing monitored enabling both quick andintuitive data interpretation. In addition to anextensive library of existing assets, SensorTrandelivers custom builds for unique or complexsolutions. The example above illustrates asystem-wide view of a substation, includingsatellite imagery as well as a CAD/CAMrepresentation of the actual facility.

Fiber Deployment for DTSSensorTran has hands-on experience deployingfiber for new construction and for retrofitapplications where fiber is added to existinginfrastructure and circuits.

To date, the majority of fiber deployments forpower cables have been during new constructionprojects. In this situation, the fiber is typicallyplaced inside the cable itself or externallybound/banded to the cable. If properly planned forby both the utility and installer, this type ofdeployment is straightforward and easilyaccomplished.

Existing InfrastructureFor situations where existing infrastructure is to bemonitored, the fiber optic probe must be retrofitonto the cable or into the cable duct bank.

SensorTran has proven through practicaldemonstration that fiber probes can besuccessfully retrofit into existing facilities withoutdamaging the power cables, even in situationswith sharp angles of up to 90 degrees.

This ability to effectively retrofit DTS monitoring

solutions is one of the key elements that makesDTS a unique, cost-effective piece of the SmartGrid infrastructure.

DTS Costs

As previously mentioned, DTS monitoring can beimplemented in dense urban conditions for as lowas $10/meter. This low-cost is possible becauseSensorTran DTS systems are designed with thehighest optical budget on the market deliveringa best-in-class signal-to-noise ratio & industry-leading temperature resolution. Given theoutstanding performance of these systems, asingle DTS can be deployed with up to 50channels, enabling a single DTS to monitor amultitude of discrete assets. Depending ondistance and specific monitoring conditions, asingle probe may be used to monitor one cable

using one channel or run serially along multiplecables, enabling one channel to monitor morethan one asset.

Cable Ampacity Analysis SoftwareIn addition to providing real-time distributedtemperature data, Cable Ampacity AnalysisSoftware is now available to provide real-timetemperature rating (RTTR) capabilities. CAASuses the dense DTS temperature measurementsmade over time and real-time load as inputs toimprove the accuracy of ampacity calculations.

CAAS computes the cable conductor coretemperature in-real time and provides variousquery-based tools for the computation of cablethermal ratings as below:

derive ampacity from time and temperature derive temperature from load and time derive time from load and target temperature

This capability is available without requiring anyadditional hardware, further enhancing the valueof DTS deployment.

The ability to use one cost-effective DTS systemto monitor circuits for immediate and futurecapacity-related events is clearly in line with thegoals of efficient Smart Grid implementation making it a key infrastructure technology.


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The SensorTran Advantage

SensorTran, a NASA technology spin-off, is the technology leader in distributed

temperature sensing and is committed to supplying its customers with smart, cost-effective

distributed monitoring solutions. The company employs the largest fully DTS-focused team

in the industry and is leading the charge in pushing the boundaries of the existing

technology while making DTS easier to use. The SensorTran team is dedicated to providing

best-in-industry customer care from project conception to the development of

specifications, through installation, training, and beyond.

SensorTran is ISO-9001 certified and UL registered.

sensortran technology brief mar11

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