Protection system and method for an electrical variable speed doubly fed induction machine

Patent metadata

Field	Value
Publication number	US-2016013632-A1
Application number	US-201414771367-A
Country	US
Kind code	A1
Filing date	Feb 25, 2014
Priority date	Feb 28, 2013
Publication date	Jan 14, 2016
Grant date	—

Abstract

A protection system for an electrical variable speed doubly fed induction machine having a stator and a rotor, comprising:
instrument transformers capable of measuring low frequency signals from the rotor and stator, in particular low frequency signals in the range of 0.1 Hz to 6 Hz; a protection relay which is configured to receive measurement values from the instrument transformers and to sample said measurements values at a constant sampling rate.

First claim

1 . A protection system for an electrical variable speed doubly fed induction machine (IM) having a stator (S) and a rotor (R), comprising:
instrument transformers (CTR 1 , CTR 2 , CTS 1 , CTS 2 , VTR 1 , VTR 2 ) capable of measuring low frequency signals from the rotor and stator, in particular low frequency signals in the range of 0.1 Hz to 6 Hz; a protection relay (R 1 , R 2 ) which is configured to receive measurement values from the instrument transformers and to sample said measurements values at a constant sampling rate.

2 . The protection system of claim 1 , wherein the instrument transformers comprise a first set of current transformers (CTR 1 , CTR 2 ) for measuring rotor currents, a second set of current transformers (CTS 1 , CTS 2 ) for measuring stator currents, and a first set of voltage transformers (VTR 1 , VTR 2 ) for measuring rotor voltages.

3 . The protection system of claim 2 , wherein the instrument transformers further comprise a second set of redundant voltage transformers for measuring rotor voltages.

4 . The protection system of any one of claims 1 - 3 , wherein the protection relay (R 1 , R 2 ) is connected to the instrument transformers by means of a merging unit (MU 1 , MU 2 ) which receives and samples the measurement values from the instrument transformers, the sampled measurement values being transmitted to the protection relay which re-samples the measurement values at said constant sampling rate.

5 . The protection system of claim 4 , wherein the protection relay comprises an IEC 61850-9-2 LE compliant interface module to communicate with the merging unit.

6 . The protection system of any one of claims 1 - 5 , wherein the protection relay comprises at least one protection module configured to implement a protection algorithm, said protection algorithm making use of the measurement values sampled at said constant sampling rate.

7 . The protection system of any one of claims 1 - 5 , wherein the protection relay comprises at least one protection module configured to implement a protection algorithm, said protection algorithm making use of root mean square values each calculated for a series of measurement values sampled at said constant sampling rate within a variable window.

8 . The protection system of any one of claims 6 - 7 , wherein the protection relay comprises a stator overcurrent protection module and/or a rotor overcurrent protection module and/or a rotor overvoltage protection module and/or a rotor overfrequency protection module.

9 . The protection system of claim 7 , wherein the protection relay comprises a stator negative phase sequence overcurrent protection module and/or a rotor neutral voltage protection module.

10 . The protection system of claim 9 , wherein the protection relay comprises a stator current transformer supervision module configured to block the stator negative phase sequence overcurrent protection module in case of failure of a current transformer associated to the stator.

11 . The protection system of claim 9 taken in combination with claim 3 , wherein the protection relay comprises a voltage transformer supervision module configured to block the rotor neutral voltage protection module in case of failure of a voltage transformer associated to the rotor.

12 . The protection relay of any one of claims 1 - 11 , wherein the protection relay comprises a rotor overfrequency protection module.

13 . The protection system of any one of claims 1 - 12 , wherein a quality flag is associated with each sampled measurement value.

14 . A method for protecting an electrical variable speed doubly fed induction machine (IM) having a stator (S) and a rotor (R), comprising, at a protection relay (R 1 , R 2 ), receiving measurement values from instrument transformers (CTRL, CTR 2 , CTS 1 , CTS 2 , VTR 1 , VTR 2 ) capable of measuring low frequency signals from the rotor and stator, in particular low frequency signals in the range of 0.1 Hz to 6 Hz, and sampling said measurements values at a constant sampling rate.

Assignees

• Alstom Technology Ltd
• Alstom Technology Ltd

Inventors

• Lloyd Graeme
• Zou Li
• An Chang

Classifications

• H02H7/06 Primary

  for dynamo-electric generators; for synchronous capacitors · CPC title

• H02H7/09

  against over-voltage; against reduction of voltage; against phase interruption · CPC title

• H02H7/08

  for dynamo-electric motors · CPC title