Determining an operational limit of a power transmision line

• US 20050222808A1
• Filed: 12/11/2002
• Published: 10/06/2005
• Est. Priority Date: 12/21/2001
• Status: Active Grant

• Current Assignee: Hitachi Energy Switzerland AG (Hitachi, Ltd.)
• Original Assignee: ABB Schweiz AG (ABB Limited)
• Inventors: Larsson, Mats, Zima, Marek, Rehtanz, Christian
• Granted Patent: US 7,107,162 B2
• Time in Patent Office: Days
• US Class Current: 702/182
• CPC Class Codes: H02H 3/40 responsive to ratio of voltage and current
• CPC Class Codes: H02H 6/005 using digital thermal images
• CPC Class Codes: H02H 7/226 for wires or cables, e.g. heating wires

Abstract

In a method, computer program and system for determining an operational limit of a power transmission line, time-stamped current phasor information and voltage phasor information for a first end and a second end of the line are determined, an ohmic resistance of the line is computed from the phasor information, and an average line temperature is computed from the ohmic resistance. This allows to determine the average line temperature without dedicated temperature sensors. The average line temperature represents the actual average temperature and is largely independent of assumptions regarding line parameters.

Claims

1. A method for determining an operational limit of a power transmission line, comprising the steps of

determining time-stamped current phasor information and voltage phasor information for a first end and a second end of the line,

computing an ohmic resistance R of the line from the phasor information,

computing an average line temperature T₁ from the ohmic resistance R.

2. The method according to claim 1, comprising the step of controlling a power flow through the line such that the average line temperature T₁ does not exceed a given maximum average line temperature T_max.

3. The method according to claim 1, comprising the steps of computing actual electrical parameters (R, X_L, X_C) of the line and computing, from the actual electrical line parameters, a maximum load s_max that is deliverable by the line.

4. The method according to claim 3, comprising the step of controlling a power flow through the line such that an actual power s delivered by the line does not exceed the maximum load s_max.

5. The method according to claim 4, wherein the step of controlling power the flow through the line ensures that the average line temperature T₁ does not exceed a given maximum average line temperature T_max.

6. A computer program for determining an operational limit of a power transmission line loadable into an internal memory of a digital computer, comprising computer program code means to make, when said program is loaded in the computer, the computer execute the method according to one of claim 1.

7. A system determining an operational limit of a power transmission line, wherein the system comprises a data processing device and means for

determining time-stamped current phasor information and voltage phasor for a first end and a second end of the line,

computing an ohmic resistance R of the line from the phasor information,

computing an average line temperature T₁ from the ohmic resistance R.