Answers for energy.

ISCM – Overhead Line MonitoringFor maximum power-throughput and highly effective planning

Transmission line real-time rating is the highest current at which a power line can be operated without violating safety codes, the integrity of line materials, or network reliability. When line current increases, the conductor heats up, elongates, and the line sags increase. If the line is operated beyond its maximum design temperature, the line sags may violate design clearances. Use of the Transmission Line Monitoring System for dynamic ratings allows utilities and transmission operators to develop and apply line ratings in real time, based on actual weather conditions instead of fixed, conservative assump tions. Because transmission systems require a very high level of reliability, unmonitored transmission networks can never be utilized at their full capabilities. A transmission network must always withstand the largest credible contin gency, i.e., the loss of its most critical element.

Valuable information at your fingertips

Overhead Line Monitoring is one of the modules of ISCM, our integrated and flexible solution for energy networks. ISCM covers all relevant components of your electricity supply network – from transformers and switchgear to over- head lines and cables – all monitored, analyzed, and visualized with one system. It can be seamlessly integrated in the existing substation infrastructure. Thus, ISCM provides a major contribution to reliable network operation and management.

All relevant data is well documented and stored for further investigations and as reference for future surveys about similar conditions and events.

Reliable diagnoses through advanced knowledge modules

Using patented temperature sensors, load cells, cellular or radio communications, and advanced rating algorithms, Overhead Line Monitoring is a powerful tool for maximizing the capabilities of transmission lines and avoiding unnecessary operator interventions for transmission line loading relief. Typically, dynamic ratings provide higher line capabilities 98% of the time and provide at least 15–30% additional capability for over 95% of the time.

Data can then be used to optimize the load on overhead lines, so that they can transmit more power, while ensuring that the sag remains well within safety limits.

The system operates “in the background,” sending an alarm signal only when specific conditions occur, and allowing operators to interrogate the systems in anticipation of system changes.

Precise temperature measurements are accomplished by two systems: The ambient temperature sensor is a highly accurate device that provides a reading with a resolution of 0.1ºC. The sensor incorporates an aspirated shield. The net radiation sensor is designed to provide approximately the same emissivity, absorbency, cooling surface, and time constant as the conductor being monitored. The net radiation sensor measures the temperature the conductor would attain if it were de-energized. This provides a baseline measurement for the calculation of the actual temperature of the energized conductor.

Forecast ratings

Short-, medium- and long-term statistical rate forecasts can be made.

• 30-minute forecast – contingency response

• 1–4-hour forecast – minimising or avoiding dispatch changes

• 24 hour forecast – dispatch, generation, and outage scheduling

These forecasts are backed up by accurate, observable real-time ratings and are usable for power marketing, operations planning, maintenance scheduling, and asset manangement decisisions as well as, not least, for operating decisions based on real-time ratings.

For maximum power-throughput and highly effective planning

ISCM – Overhead Line Monitoring

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Your benefits at a glance

Optimized use of infrastructure by maximizing the capacity of transmission paths

Elimination of unnecessary and often risky operator interventions

Quick reaction time for contingencies and responsiveness to weather

Safe and reliable operation above static ratings

Minimal disruption to the network when correcting line dispatch

Meeting new transmission reliability regulations

Rapidly deploy solutions when capacity deficiencies are discovered

Raise transmission capacity by 15–30% to avoid network congestion

Accurately monitor sag on older lines, where design conditions are least certain

Match overhead line ratings to actual load capacity and weather conditions

Provide advance warning of impending clearance violations

Avoid unnecessary operator actions

Additional available capability with Transmission Line Monitoring real time rating

100

Capability

% of Time

Time of day

Additional available capability

Actual real time rating

Risk with static rating

Static rating

Static rating

50

0

50

100

150

200

250

Capability with static rating

Capability

0

100

200

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Published by and copyright © 2009:Siemens AGEnergy SectorFreyeslebenstrasse 191058 Erlangen, Germany

For more information, please contact our Customer Support Center.Phone: +49 180 524 70 00 Fax: +49 180 524 24 71 (Charges depending on provider)E-mail: support.energy@siemens.com

Power Distribution DivisionOrder No. E50001-G730-A130-X-7600Printed in GermanyDispo 19210, c4bs No. 7824fb 1770 61/20160 480484 WS 04093.

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All rights reserved. Trademarks mentioned in this document are the property of Siemens AG, its affiliates, or their respective owners.

Subject to change without prior notice. The information in this document contains general descriptions of the technical options available, which may not apply in all cases. The required technical options should therefore be specified in the contract.