A remarkable new type of low cost and easily installed intelligent powerline sensors are nearing commercial readiness. They come in three flavors:
– Medium Voltage Single Phase Overhead (4 – 69 KV)
– Medium Voltage Single Phase Underground
– Low Voltage Single and Multi-phase Underground (e.g., 208 V)
The medium voltage devices simply clamp on the cable, and measure voltage and current without a connection to ground or a phase-to-phase connection. There is no penetration of cable voltage insulation. (It is not applicable to coax or multiple conductor configurations–only single unshielded cables.) The underground units are self-powered by the power line, and the overhead ones use batteries that will last 5 years or more.
They are said to be approximately ten times cheaper to buy and install, and offer far greater capabilities than anything else on the market. Measurement accuracies (I, V, P) are quoted at better than 3%, though the units invariably do much better. It is not a revenue meter, however.
Evaluation units are available now, and the first production units will be ready before the end of the year. Five utilities (including one or two UFTO companies) have been testing overhead sensors.
The sensors measure current and voltage and can be equipped to measure and/or detect a number of additional conditions or quantities including temperature, moisture, specific substances, light, acceleration, and vibration. Underground sensors utilize two-way powerline carrier communications over the existing lines and overhead sensors communicate through two-way low power RF systems.
Each sensor has its own local on-board intelligence to perform data processing and analysis. In typical applications the sensors calculate true rms voltage and current, power factor and harmonic content. Peak rms quantities and fault recognition capabilities can also be employed.
The sensors report by exception, when polled, or at determined times. Since data is processed at the sensors, communications bandwidth requirements are relatively low. Only processed data or observed data related events (like faults, voltage dips, or high current limits) are reported — not extensive strings of raw data.
Typical functions of these sensors (both overhead and underground) include:
– Detection and location of faults
– Measurement of power quality
– Identification of grounding and cable insulation issues
– Detection of non-technical losses
– Detection of unanticipated loads
– Confirmation of recloser, sectionalizer and other switch operations
– Support capacitor switching algorithms
– Monitoring distributed generation
– Distribution Automation
– Operations Support
– Fault Detection, Classification and Location
– Power-line losses
– Power Factor and VAR Monitoring
– Switch Operation Confirmation
– Planning Studies
– Circuit Design
Condition Based Maintenance
– Cable Burnout and Circuit Limiter Detection (low voltage U/G)
– Equipment Health Status (Fuse, Cutout, Transformer, Switch)
– Tree Trimming Effectiveness
Beyond the Meter Services
– Power Quality
– Sub-metering and Beyond-the-Meter Distribution Networks
– Harmonic Analysis
The underground sensors were initially developed for Consolidated Edison’s Secondary Underground Network Distribution Automation System (SUNDAS). The objective was to develop a comprehensive sensing system that would be relatively inexpensive to purchase, install, operate and maintain.
Con Ed has tested experimental versions of the low voltage underground sensors in their Battery Park City and Harlem networks. These tests demonstrated the capabilities of these sensors to monitor powerline conditions and to detect variations in line conditions associated with circuit limiter loss, arcing faults, changes in network protector relay status and unusual changes in power flow patterns. Based on the performance of the experimental sensors, Con Edison will install GridCom sensors throughout the Hunter network with installations beginning this fall.
US Patent No. 5,892,430: Self-powered powerline sensor
The company’s website has a lot of information and pictures:
Contact: Rich Wiesman, 781-684-4387 email@example.com