Nashville Electric Service (NES) has deployed Telemetric TC012 MicroRTUs to monitor and control their distribution capacitor banks. Using the Telemetric TC012, Nashville is now able to affordably obtain near real-time information on the condition of their capacitor banks. In the past, NES relied on physical inspections to locate faulty capacitor banks. This system would often leave capacitor banks out of service for extended periods before the condition was known and corrected. Early detection of the loss of capacitor banks will allow NES to decrease the total number of banks that must be installed to keep a given amount of power factor correction on-line; thereby decreasing capital costs.
The Telemetric solution has the added benefit of allowing NES to remotely operate their capacitor banks; thus adding more flexibility to the control of distribution system voltage. Although switching of these banks is presently done only for maintenance purposes, safety associated with local operation has been a concern and remote switching will eliminate this concern.
Walter Brostrom, Senior Engineer with NES said, “Now, we have critical information about our distribution equipment that we were never able to capture before. By knowing the status of our capacitor banks, we are able to respond to equipment problems much faster. This has the dual benefit of decreasing our maintenance costs and improving our system power factor.”
“In the past, utilities would never have dreamed of communicating with fixed capacitor banks, now Telemetric’s low-cost solution makes this possible,” said Scott Schoenherr, Telemetric’s CEO. He added, “With up-front costs of less than $1,000 and communications costs as low as $6 per month utilities are now able to communicate with all sorts of down-line equipment that in the past was thought to be too remote to cost-justify communications.”
The TC012 is an application specific configuration of the field tested and proven Telemetric T646 MicroRTU. It provides information on the condition of the capacitor bank by monitoring the neutral current of the bank. A sensor provides the bank control with a 0-10 VAC signal corresponding to the level of the 0-100 Amp capacitor bank neutral current. From the level of this signal, an inference is made as to the condition of the bank as follows: A neutral current of zero indicates that the installation is switched out of service. Normal neutral current (a nominal value above zero) when the bank is closed, indicates that the bank is in service and operating properly. A level of neutral current higher than the nominal normal bank current indicates the presence of high harmonic current or a partial pack failure. A higher, predefined level of current indicates a blown fuse or other serious problem. The device provides capacitor bank control through two-30 amp relays. Following detection of a change of status, the device reports the AC line voltage, open/close status, and the neutral current.
The module includes an internal cellular radio providing true two-way communication with coverage available to 98% of the populated area of North America. Information can optionally be viewed over SCADA or a secure, password protected web server. By utilizing the "control channel" of the cellular network, Telemetric allows customers to send small packets of data over the existing cellular infrastructure, which provides far better coverage at a much lower cost than other methods of communication. No cellular account is necessary.
Telemetric has helped nearly 100 utilities control costs and improve customer service by allowing them to cost-effectively monitor and control equipment located outside their substations.