Apparatus and method for identifying the phase and terminal for power system devices

A method for determining which phase is associated with a first and a second voltage terminal of an intelligent electronic device (“IED”) at a location of an electrical power system based on known phase and known phase angles associated with a first and a second current terminal of the IED at the location of the electrical power system, the method comprising the steps of:

• the IED determining the phase angle associated with the first voltage terminal,
• when the phase angle associated with the first voltage terminal is equal to the phase angle associated with the first current terminal, the IED associating the first voltage terminal with the same phase as the known phase associated with the first current terminal,
• the IED determining a phase angle associated with the second voltage terminal, and
• when the phase angle associated with the second voltage terminal is equal to the phase angle associated with the second current terminal, the IED associating the second voltage terminal with the same phase as the known phase associated with the second current terminal.

A method for determining the phase associated with first, second and third voltage terminals of an intelligent electronic device (“IED”) at a location of an electrical power system based on known phase and known phase angles associated with first, second and third current terminals of the IED at the location of the electrical power system, the method comprising the steps of:

• the IED determining a phase angle associated with the first voltage terminal,
• when the phase angle associated with the first voltage terminal is equal to the phase angle associated with one of the first, second, and third current terminals, the IED associating the first voltage terminal with the phase associated with the one of the first, second, and third current terminals whose known phase angle is equal to the phase angle of the first voltage terminal,
• the IED determining a phase angle associated with the second voltage terminal,
• when the phase angle associated with the second voltage terminal is equal to the phase angle associated with one of the first, second, and third current terminals, the IED associating the second voltage terminal with the phase associated with the one of the first, second, and third current terminals whose known phase angle is equal to the phase angle of the second voltage terminal, and
• the IED associating the third voltage terminal with a phase associated with the current terminal whose known phase is not associated with the first or second voltage terminals.

An apparatus for determining a phase associated with first and second current terminals at a location of an electrical power system based on a known phase and known phase angle associated with a third current terminal at the location of the electrical power system, the apparatus comprising:

• an input terminal for entering the known phase angle associated with the third current terminal, and
• a microprocessor coupled to the input terminal, said microprocessor adapted to:
• associate the first current terminal with a next sequential phase from the known phase associated with the third current terminal and assign the second current terminal with a previous sequential phase from the known phase associated with the third current terminal when a phase angle associated with the first current terminal is equal to the known phase angle associated with the third current terminal minus about 120 degrees, and
• associate the first current terminal with a previous sequential phase from the known phase associated with the third current terminal and assign the second current terminal with a next sequential phase from the known phase associated with the third current terminal when the phase angle associated with the first current terminal is not equal to the known phase angle associated with the third current terminal minus about 120 degrees.

An apparatus for determining which phase associated with a first, a second and a third voltage terminal at a location of an electrical power system based on known phase and known phase angles associated with first, second and third current terminals at the location of the electrical power system, the apparatus comprising:

• an input terminal for entering the phase angle associated with the first and second current terminals,
• a microprocessor coupled to the input terminal, said microprocessor adapted to:
• associate the first voltage terminal with the same phase as the phase associated with one of the first, second, and third current terminals whose known phase angle is equal to the phase angle associated with the first voltage terminal,
• associate the second voltage terminal with the same phase as the phase associated with one of the first, second, and third current terminals whose known phase angle is equal to the phase angle associated with the second voltage terminal, and
• associate the third voltage terminal with a phase associated with the current terminal with a known phase not associated with the first or second voltage terminals.

A method for determining a phase of an electrical power system associated with a first terminal of an electric power system device based on a known phase rotation and known phase associated with a second terminal of the electric power system device, the method comprising the steps of:

• the electric power system device determining a phase angle associated with the second terminal and a phase angle associated with the first terminal;
• when the phase angle associated with the first terminal is equal to the phase angle associated with the second terminal plus about 120 degrees, associating the first terminal to a next phase in the known phase rotation;
• and,
• when a phase angle associated with the first terminal is equal to the phase angle associated with the second terminal minus about 120 degrees, associating the first terminal to a previous phase in the known phase rotation.