The subject matter disclosed herein relates to a system for identification of an electrical phase of a cable and more particularly to a system that determines an electrical phase where the cable has either a conductive outer cover or a nonconductive outer cover.
Electrical cables are used in a wide variety of application to transfer a electrical power from one location to another. In some cases, high levels of electrical power need to be transferred requiring the use of particular cables. A variety of types of conductors may be used, such as paper insulated lead covered cable, solid dielectric cable, oil filled pipe type cable or gas-filled insulated cable for example. In three-phase operation, three cables will be used together each carrying a single electrical phase. Over time, a break or open condition may occur in these cables for a variety of reasons such as maintenance, construction or an electrical fault for example. When a break occurs in the cables, it is necessary to identify the phase of each cable prior to reconnecting the ends of the cable.
Identification of the correct phase is important for the proper operation of the power system. The crossing of phases during repairs will result in having to re-work the splice and risk potential failures that could damage the conductors and other equipment in the electrical network.
Before any work can be performed on the conductors, the feeder circuit in the distribution network needs to be identified and protected (grounded) for work. The method of identifying the feeder circuit will depend on how the conductors were damaged. If only one of the conductors is broken, applying a tracing current to the two remaining conductors can identify the feeder circuit. This technique is effective because the remaining conductors provide a return path for the tracer current.
When the fault causes a break in all three conductors, the tracing current method will not be effective since there is no return path. In this case, a spear is applied to the cable shorting all three conductors. This creates a path for the tracing current so that the feeder can be identified. However, the phase of each cable cannot be identified with the spear in place.
Commonly, the identification of the phases and the repairs of the cables are performed by separate personnel: a Splicer who repairs and splices the conductors back together, and a phase identification crew. Separate personnel are used because the tracing method used for identifying the phase requires additional special training. Further, the phase identification crew needs to locate and travel to the transformers located on either side of the section having an open circuit condition. The transformers are grounded, isolating the section having an open circuit condition. The Splicer then prepares the conductors for splicing. The identification crew applies an audio frequency tracing tone to the conductors on the transformer side of the conductor and then travels back to the section having the open circuit condition. The phase identification crew uses the trace tone to identify and label the phase on each of the conductors. This is repeated for each set (3 conductors) of cable ends that need to be spliced. In the case of medium voltage transmission cables, the transformers are located a distance from the location of the failure. It is time consuming for the phase identification crew to travel, set up to enter an underground structure to perform the splice, and then perform the testing required to establish the phases. In addition, multiple trips may be required. This is performed for each set of cable ends (a minimum of two).
Once the conductors are labeled, the Splicer may complete the repair and splice the conductors on either side of the open circuit section back together. The power lines may then be re-energized and electrical service restored.
Accordingly, while the process for identifying and repairing conductors any three-phase system is suitable for its intended purposes the need for improvement remains, particularly in allowing the identification of electrical phase for a variety of cable types.
According to one aspect of the invention, a system for identifying an electrical phase of three conductors in a three-phase electrical system at an open end is provided. The system includes a transmitter and a receiver unit. The transmitter unit has three current transformers configured to removably couple with one of the three conductors adjacent the transformer. The transmitter unit further having a first communication device configured to transmit a phase identification signal indicating at least one electrical phase detected on one of the three conductors. The receiver unit has a first output lead configured to removably couple at the open end with a first conductor and a second output lead configured to couple with a second conductor. The receiver unit is configured to transmit a trace current onto the first output lead. The receiver further displays phase identification information in response to receiving the phase identification signal.
It should be appreciated that while embodiments herein describe the system 100 in connection with a three-phase electrical distribution or transmission system, this is for the exemplary purposes and the claimed invention should not be so limited. Embodiments of the present invention may include three or more electrical phases or may also include multiple three-phase circuits arrange in parallel for example.
According to another aspect of the invention, a method of identifying the electrical phase of three conductors in a three-phase electrical system is provided. The electrical conductors having a first end coupled to a transformer and a second open end. The method includes coupling three current transformers to the three conductors adjacent the transformer. A first output lead is coupled a first of the three conductors at the open end and a second output lead at a second of the three conductors at the open end. A trace current is transmitted with the first output lead onto the first conductor. The trace current is detected with at least one of the current transformers. A phase identification signal is transmitted with a transmitting unit coupled to the three current transformers. The phase identification signal is received with a receiving unit coupled to the first output lead and the second output lead. Cable phase identification information is displayed on the receiving unit in response to receiving the signal.
According to yet another aspect of the invention, a system for identifying an electrical phase of conductors in a three-phase electrical system at an open location between and distal from a first transformer and a transformer is provided. The system includes a first transmitter unit, a second transmitter unit and a receiver. The first transmitter unit has three current transformers, each of the three current transformers being configured to removably couple with one of the three conductors adjacent the first transformer, the first transmitter unit further having a first communication device configured to transmit a first phase identification signal indicating at least one electrical phase detected on one of the three conductors. The second transmitter unit has three current transformers, each of the three current transformers being configured to removably couple with one of the three conductors adjacent the second transformer, the second transmitter unit further having a second communication device configured to transmit a second phase identification signal indicating at least one electrical phase detected on one of the three conductors. The receiver unit includes a first output lead configured to removably couple at the open location with a first conductor coupled to the first transformer and a second output lead configured to removably couple at the open location with a second conductors coupled to the first conductor. The receiver unit also includes a third output lead configured to removably couple at the open location with a third conductor coupled to the second transformer and a fourth output lead configured to removably coupled at the open location with a fourth conductor coupled to the second transformer. The receiver unit is configured to transmit a trace current onto the first output lead and the third output lead, the receiver unit having a second communications device configured to couple for communication with the first communications device and the second communication device, the receiver having a display electrically coupled to the second communications device to display information in response to receiving the first phase identification signal and the second phase identification signal.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
Embodiments of the present invention provide advantages in allowing the identification of electrical phases in a three-phase system where the cable end is remotely located from a transformer. Embodiments of the present invention provide further advantages in allowing the identification of electrical phases for a variety of electrical cable types including but not limited to paper insulated lead covered cable, solid dielectric cable, oil filled pipe type cable or gas-filled insulated cable. Embodiments of the present invention provides still further advantages in allowing identification of electrical phases without having a direct electrical connection at the transformer.
In the exemplary embodiment, a deadline phase identification system 100 is provided having a phase receiver unit 102 (
In one embodiment, the phase receiver unit 102 uses electrical power from an external source, such as line power, from a generator or from an inverter. In one embodiment the phase receiver unit 102 operates at 120 VAC at 3 A during operation. The phase receiver unit 102 is configured to transmit a tracing current via the output leads 120. In one embodiment the tracing current is limited to 9 V or less and may have a tracing current range from 0.1 to 9.0 amps depending on the impedance of the cables under test. The phase receiver unit 102 may include a cable having a NEMA L1-15 twistlock receptacle on one end that facilitates connecting the output leads 120 to the phase receiver unit 102. The output leads 120 may include alligator clips to facilitate connection with the cable being identified.
The phase transmitter unit 104 includes three current transformers 122, a cellular modem 124 and a battery that allows for remote operation. In LCD display 126 show system operation and status, while to toggle switches 128 allow for changes in the system operation to be made. The phase transmitter unit 104 is contained within a case 130 that includes an area 132 sized to receive and store the current transformers 122. Each of the current transformers 122 includes indicia 134 indicating the phase for that particular current transformer 122. It should be appreciated that while embodiments herein describe the communications between the phase transmitter unit 104 and the phase receiver unit 102 as being cellular communications, this is for exemplary purposes and the claimed invention should not be so limited. Embodiments of the invention may use other forms of communication, including but not limited to wireless, wired, wide-area computer networks, local-area computer networks, and radio for example.
Referring now to
The transmitter unit 104 is positioned adjacent a transformer 136 that is located opposite the open end 142 of electrical cables 138. Each of the current transformers 122 are coupled to one of the cables 138 adjacent the transformer elbows 140 (
At the open end 142 of the cables the phase receiver unit 102 is positioned adjacent the end of the cables 138. A first output lead 120A is connected to the copper conductor 144 a first cable, such as cable 138B for example. A second output lead 120C is connected to the neutral strap 146 of a second cable, such as cable 138C for example. In one embodiment, the neutral straps 146 are connected together by a bond wire 147 (
It should be appreciated that at the location of open-end 142 there will be two sets of cables that need to be identified on either side of the break. In one embodiment, a second transmitter unit 104 is located at a second transformer 136 and the electrical phase identification is performed on this second cable as well. After all of the cables have been identified in splicing operations have reconnected the ends of the cables, the tracing current may be applied once again. When this step is performed, each of the transmitter units 104 should transmit to the receiver unit 102 the same electrical phase identification to provide verification. In one embodiment, the identification process occurs simultaneously on each side of the open end 142.
Referring now to
As before, the receiver unit 102 is positioned adjacent the open-end 142. The first output lead 120A is connected to the copper conductor 144A of a first cable, such as cable 148A. In this embodiment the second output lead 120C is connected to the copper conductor 144C of the second cable, such as cable 148C. The tracing current is then applied via first output lead 120A and received back through second output lead 120C. The tracing current is detected via the current transformers 122 by the transmitter unit 104. The phase transmitter unit 104 having detected the tracing current on cables 148A, 148C then transmits this electrical phase identification to the phase receiver unit 102. The phase receiver unit 102 then displays the electrical phase of the unconnected cable 148B. The operator may then label the cable to which the output leads 120A, 120C are not connected. This process is repeated for each of the cables 148 until the electrical phase for each of the cables is identified.
As discussed above, it should be appreciated that at the location of open-end 142 there will be two sets of cables that need to be identified on either side of the break. In one embodiment, a second transmitter unit 104 is located at a second transformer 136 and the electrical phase identification is performed on this second cable as well. After all of the cables have been identified in splicing operations have reconnected the ends of the cables, the tracing current may be applied once again. When this step is performed, each of the transmitter units 104 should transmit to the receiver unit 102 the same electrical phase identification to provide verification.
It should be appreciated that the transformer 136 ground remains applied while the phase measurements are made. This provides advantages in maintaining a desired electrical ground to protect repair personnel.
During the initial setup of the system 100, the receiver unit 102 is first connected with electrical power and a run/isolate switch is moved to the isolate position. The receiver unit 102 is turned on and a cellular modem is activated. The display 110 shows an initial display such as that shown in
Next, the identification parameters of the transmitter unit(s) 104 that determined and entered into the receiver unit 102. This may be done, for example, by entering the serial number of the transmitter unit(s) 104 as shown in
Where operation is being performed on a rubber coated cable, the alligator clip for the lead 120A is connected to the copper conductor 144. In some applications a copper nail (
During operation performed on a lead coated cable this process is similar except that the second lead 120C is connected to the copper conductor on the second cable as described above. In both modes of operation the run/isolate switch is changed to the isolate position prior to moving the alligator clip between cables. This interrupts the tracing current and indicates to the phase receiving unit 102 that the operator is moving the output lead 122 different cable. At the transformer, the loop is completed by moving the transformer primary ground lever to the “ground” position. If the phasing cables are not yet terminated at the transformer 136, the copper conductors and neutral straps (for rubber coated cables) may be connected together with temporary wires.
In the exemplary embodiment, the phase receiving unit 102 will automatically receive the identified phases from each phase transmitter unit 104 until the tracing current is removed. If the receiving unit 102 and the transmitting unit 104 are not connected for communication, the display 110 will indicate a “phone symbol” as shown in
In an embodiment, the display 110 indicates a signal quality 152 which indicates that more verifications of the displayed phase have been made. In one embodiment four phase measurements are made in order to get a 100% signal quality. As shown in
In one embodiment, when the phase transmitter unit 104 is online, a vertical bar graph symbol 156 is shown on display 110 as shown in
On the phase transmitter unit 104, the display 126 may be used to show the operators the signal being measured at each current transformer 122. In one embodiment, the display 126 shows the frequencies in the format of an oscilloscope waveform as shown in
After the cables have been identified, the system 100 may include a phase verification record to document the splicing of the cables together. This phase verification record 160 may be automatically transmitted via cellular modem 106 to a remote computer for storage. In other embodiments, the phase verification record may be stored locally on the phase receiver unit 102 on removable media, such as a flash drive for example. In still other embodiments, the phase receiver unit 102 may include an output port such as but not limited to a USB port, an ethernet port or serial port for example that allows the phase receiver unit 102 to communicate data of the phase verification record 160 an external device. In still other embodiments, the phase receiver unit 102 may include a wireless connection circuitry including but not limited to Bluetooth or WiFi for example, to allow communication of the phase verification record 160.
In one embodiment, the phase verification record 160 is shown in
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
The Present application claims priority to U.S. Provisional Application Ser. No. 61/585,452 filed on 11 Jan. 2012, the contents of which are incorporated herein in their entirety.
Number | Date | Country | |
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61585452 | Jan 2012 | US |