Protection arrangement of an electric power system

• US 8,736,090 B2
• Filed: 08/06/2010
• Issued: 05/27/2014
• Est. Priority Date: 08/12/2009
• Status: Active Grant

• Current Assignee: Wartsila Italia SPA (Wärtsilä Corporation)
• Original Assignee: Wartsila Italia SPA (Wärtsilä Corporation)
• Inventors: Riihimki, Vesa
• Primary Examiner(s): TA, THO DAC
• Application Number:
  US13/389,997
• Publication Number:
  US 20120139264A1
• Time in Patent Office: 1,390 Days
• Field of Search: 290/40.R, 290/40.B, 290/40.C, 290/52
• US Class Current: 290/40.R
• CPC Class Codes: H02P 9/04 Control effected upon non-electric prime mover and dependent upon electric output value of the generator
• CPC Class Codes: H02P 9/105 for increasing the stability
• CPC Class Codes: H02P 9/107 for limiting effects of overloads

Abstract

The inventive protection arrangement of an electric power system comprises a relay arrangement (12) for measuring current, voltage or both of an electric grid (15). The relay arrangement is adapted to detect over-current, under-voltage or both. The protection arrangement comprises also a speed/load controller (16) that is in connection with the relay arrangement (12). The speed/load controller is arranged to drive a prime mover (11) of a generator (10) set as a response for the said detection. The speed/load controller (16) is connectable with said prime mover (11). In more detail the controller (16) is arranged to drive power output of the prime mover (11) to a lower level when over-current, under-voltage or both is detected.

Claims

1. A protection arrangement of an electric power system, the electric system comprising a generator set, the protection arrangement comprising a relay arrangement for measuring current, voltage or both of an electric grid, which relay arrangement is adapted to detect over-current, under-voltage or both, the generator set being separable from a grid when over-current, under-voltage or both are detected, and the detected over-current, under-voltage, or both does not stop before a critical clearing time, the critical clearing time determining a period, during which resynchronization of the generator set with the grid is possible, wherein the protection arrangement comprises a speed/load controller that is in connection with the relay arrangement, which speed/load controller is arranged to drive a prime mover of the generator set as a response for said detection, said speed/load controller being connectable with said prime mover, the speed/load controller driving power output of the prime mover to a lower level when over-current, under voltage or both is detected, the driving of the power output to the lower level is arranged to initiate during a fault of the power system and before the critical clearing time of a generator of the generator set.

2. The arrangement according to claim 1, wherein the speed/load controller comprises a fault detection unit.

3. The arrangement according to claim 1, wherein the relay arrangement comprises an instrument transformer.

4. The arrangement according to claim 1, wherein the speed/load controller is in a direct connection with the relay arrangement.

5. The arrangement according to claim 1 wherein the driving of the power output to the lower level during the fault of the power system and before the critical clearing time of a generator of the generator set reduces the driving torque P_m of the generator, moving the critical clearing time of the generator and providing a longer time for the fault clearing.

6. The arrangement according to claim 5 wherein the speed/load controller is arranged to drive power output of the prime mover to an higher level when the detection of over-current, under-voltage or both ceases.

7. A method for protecting an electric power system, the method comprising a phase for measuring at least one of current and voltage of an electric grid, the method further comprising phases for forming a detection signal in case of measurement of at least one of over-current and under-voltage, and adjusting speed/load control of a prime mover of a generator set in response to the detection signal,

wherein the adjusting phase is arranged to drive power output of the prime mover to a lower level in response to the detection signal, the driving of the power output to the lower level initiating during a fault of the power system and before the critical clearing time of a generator of the generator set.

8. The method according to claim 7, wherein the adjusting phase is arranged to drive power output of the prime mover to an higher level when the detection signal of at least one of over-current and under-voltage ceases.