The list below is the possible applications for the STR Units. Click the appropriate button to get more details on the twelve applications.
2. Power Quantities Monitoring
The Basic DSTR Units measure the true RMS line current from 6.8 amperes (with LTPS) up to 1000 amperes of steady state RMS current and up to 20,000 amperes of fault current. The Basic TSTR Units measure the true RMS line current from 26 amperes (with LTPS) up to 2500 amperes of steady RMS current and up to 40,000 amperes of fault current.
__DSTR Unit___________ _
Current Range 6.8 to 20,000 A
No measureable phase shift
Current Range 26A to 40,000 A
No measureable phase shift
Option B DSTR Units measure, in addition to the line current, the line to line voltage or the line to neutral voltage of delta connected or wye connected distribution systems, respectively, for system voltages up to 34.5 kV.
The Option B TSTR Units measure both the true RMS line current and the true RMS line to neutral or line to line system voltage up to 345 kV, although these Units are designed to operate up to 500kV.
Since both the Option B DSTR and Option B TSTR Units measure the line current, line to line or line to neutral voltage and power factor, the Powernostics® Software provides calculations of kW, kVar and kVA as instantaneous values or integrated RMS values. Synchro-phasor calculations are made from measured voltage phase angle differences between TSTR Units. Furthermore, this software calculates the percent unbalanced voltage and percent unbalanced current.
V, I, kW, kVAr, kVA, P.F.
V, I, MW, MVAr, MVA, P.F.
- Most electric power utilities only measure the current and voltage and calculate the power quantities for the substation transformers and lines emanating from the substation. Typically, there are no measurements on various segments of the distribution line after it leaves the substation. Also, only line terminal values of power quantities are measured on the transmission lines, unless very high cost voltage transformers and current transformers are installed at other intervening points on these lines.
- The DSTR Units can be placed anywhere on the distribution 3Ø primary line and on 1Ø laterals to measure power quantities. The Basic DSTR Units are installed in minutes with a specially designed hotstick on energized lines without a line shutdown, are powered from the line current itself and do not need solar panels or batteries that need to be replaced, and yet they can operate down to 6.8 amperes with the low threshold current power supply and provide full power to transmit data typically 3 to 5 miles on a continuous basis if required.
- There is no need for a local remote power supply of 120/240V, or solar panel power supply to power the DSTR Unit. There are many locations on a distribution circuit where the 120V/240V secondary does not exist at all. Some competing state-of-the-art suppliers of devices which monitor line power quantities rely completely on the availability of low voltage 120V/240V secondary voltages, or use solar panels to power their devices. Therefore, these competing technologies have to install a separate enclosure on a pole and create an auxiliary local remote power supply where 120V/240V secondaries exist, or use a pole mounted solar panel power supply which cannot provide full power continuously to transmit data on a real time basis. These local remote power supplies with a SCADA RTU and transmitter/receiver can cost an additional $3,000 for labor and hardware to install. Some competing technologies just install battery powered devices on the line, but these products can only collect data for a short period of time and must be taken off the line to download the data. These devices are very labor intensive data collection products.
- There are many applications for a distribution circuit where additional power quantity measurements are required. Normally, a distribution circuit is radial fed with one source from the electric utility. But, with the advent of distributed resources such as wind turbine driven generators, solar farms, fuel cells, gas turbine driven generators, electric vehicles, etc. multiple sources of power can be injected into the distribution circuit. These multiple sources of power can create bi-directional power flows, which may either add or subtract from the power source provided by the utility. Having DSTR Units mounted on various line segments of the distribution circuit can provide the required power quantity information to both monitor and control these distributed generation sources.
- Also, distributed generation can create voltage regulation problems for the electric utility distribution circuit. DSTR Units mounted on the distribution circuit can provide real-time voltage profile information that can aid in controlling the needed amount of reactive power from these sources to regulate the voltage and maintain the voltage within required limits. A recent study, reference  showed the capacity of distributed resource (DR’s) could be increased dramatically if DR’s are allowed to provide reactive power in addition to real power injection into the circuit.
- Since DSTR Units measure the line current of different line segments, this data is paramount to determine if various switching operations (e.g. back-to-back switching between circuits) can be performed without exceeding the thermal limits of lines and equipment.
- The power quantity data provided by DSTR Units is essential in determining the percent unbalanced voltage and percent unbalanced current at various points on a circuit to make decisions as to whether a DR unit can even be installed at the point of common coupling (PCC). There is one case where a $2 Million DR installation was completed and could not be synchronize to the system because of the high percent unbalance voltage at the PCC.
- Having large distributed resources interconnected to transmission lines can also be a problem from both voltage regulation and line loading limit perspectives. TSTR Units which can be installed at a very low cost, typically cost less than 5.0 percent of the cost of conventional high voltage transformers (VT) and current transformers (CT). The accuracy of the voltage and current measurements from the TSTR Units are one percent and, there are no saturation problems, or no measurable phase shift in the measured quantities. The TSTR Units can be installed at one location in one day or less, rather than many months for the installation of traditional VT’s and CT’s. There are no property requirements, no permits, no electrical, or civil designs, no construction plans, no shipping of heavy power equipment from the manufacturer to the site, no special rigging needed, no concrete pads to pour, and no fences to build when TSTR Units are installed on the line itself. The Powernostics® Software receives the transmitted data and creates the tables of power quantities by TSTR location. Each TSTR Unit transmits its own GPS location, and the time stamped data is synchronized per UTC.
- DSTR Units can be installed anywhere on any distribution line up to 34.5 kV whether 3Ø primary or SØ laterals as long as the line current remains above 6.8A (with LTPS) and can transmit data at full power typically a range of 3 to 5 miles at 900 MHz. The mounting jaws of the DSTR Unit can fit any wire size from #6 copper (0.162 inch) to 1000 kc mil aluminum (1.18 inch). The Basic DSTR Units are mounted directly on the line without a line shutdown and are powered from the line current without use of solar panels or batteries. Since the Units are self powered from the line there is no need for a local remote power supply which requires a 120/240V secondary which may not exist. Option B DSTR Units which measure voltage can be installed without a line shutdown. The Basic TSTR can be installed on any transmission line from 41.56 kV and up to 345 kV without a line shutdown. Option B TSTR Units which measure voltage, in most cases, require a line shutdown. The TSTR Units are self powered from the line current and with the adaptable mounting jaws can be installed on conductor sizes ranging from 4/0 copper (0.5 inches) to 2,000 kc mil (2.0 inches).
- Option B DSTR and Option B TSTR Units which measure line current, voltage, and power factor monitor the effects of operating Distributed Resources (DR) on distribution lines and transmission networks and can be used to control these resources.
- Option B DSTR and Option B TSTR Units can be used to control the reactive power from DR’s and monitor the resultant voltage profiles.
- Since these DSTR and TSTR Units measure line current and voltage, various switching operations can be performed with more assurance that lines are not overloaded and voltages remain within criteria.
- Percent unbalanced voltages and currents are needed to determine if a location (point of common coupling) will be acceptable as a possible site for some types of distributed generation.
- The cost of TSTR Units are a fraction of the cost of conventional high voltage transformers and current transformers. Furthermore, the time to prepare designs, acquire the electric power equipment and complete construction for these traditional installations take many months, and the cost for the design, equipment, and construction can be as much as 25X the cost of a TSTR Unit per phase, and yet a TSTR Unit can be installed in less than one day with a bucket truck and two linemen.
- The true RMS current and the true RMS voltage measurements of the DSTR and TSTR Units have a very wide dynamic range of measurement with no saturation and no measurable phase shift with accuracies of 1% for current and voltage. Synchro-phasor calculations (voltage phase angle differences) are obtained from different transmission systems’ TSTR Units.