Differential Protection Method and Protective Apparatus for Carrying Out a Differential Protection Method

• US 20150293166A1
• Filed: 11/26/2012
• Published: 10/15/2015
• Est. Priority Date: 11/26/2012
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Mieske, Frank
• Granted Patent: US 10,871,513 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01R 19/10 Measuring sum, difference or ratio
• CPC Class Codes: G01R 31/088 Aspects of digital computing
• CPC Class Codes: G01R 31/40 Testing power supplies testing photovoltaic devices H02S50/10
• CPC Class Codes: H02H 3/283 and taking into account saturation of current transformers
• CPC Class Codes: H02H 7/045 Differential protection of transformers
• CPC Class Codes: H02H 7/0455 taking into account saturation of current transformers

Abstract

A differential protection method for generating a fault signal. Current measurement values are acquired at different measuring points of a component. Differential current values and stabilizing values are formed using the current measurement values, and the fault signal is generated when a tripping range test indicates that a measured value pair formed from one of the differential current values and the respective associated stabilizing value lies in a predetermined tripping range. Differential current values are estimated from successive differential current values and associated stabilizing values and associated estimated stabilizing values are formed. A value of an expected future trend of the differential current values and of the stabilizing current values is estimated. A tripping range test finds the position of a measured value pair formed from an estimated differential current value and the respective associated estimated stabilizing value. An electrical protective device has a corresponding evaluation unit.

Claims

1-9. -9. (canceled)

10. A differential protection method for generating a fault signal, the method comprising:

measuring respective current measurement values at two or more different measurement locations of a component;

forming differential current values and stabilization values from the current measurement values;

estimating, from successive differential current values and associated stabilization values, differential current values and associated estimated stabilization values, and estimating therefrom at least one value of an expected future profile of the differential current values and the stabilization current values;

conducting a tripping range test by evaluating a position of a measurement value pair formed from an estimated differential current value and the respectively associated estimated stabilization value; and

if the tripping range test indicates that a measurement value pair formed from one of the differential current values and the respectively associated stabilization value lies in a predefined tripping range, generating the fault signal.

11. The method according to claim 10, which comprises forming a respective estimated differential current value in each case from a present differential current value and a differential current value directly preceding the present differential current value, and using in each case the present stabilization value and the stabilization value directly preceding the present stabilization value for forming a respective estimated stabilization value.

12. The method according to claim 11, wherein the respective estimated values indicate an amplitude of the expected future profile of the differential current values and an amplitude of the expected future profile of the stabilization values.

13. The method according to claim 12, which comprises in each case forming the respective estimated differential current value and the respective estimated stabilization value using a first estimated value portion formed by an integrating element and a second estimated value portion formed by a differentiating element.

14. The method according to claim 10, which comprises blocking an output of the fault signal if a predefined number of successive measurement value pairs lie in a predefined stabilization range.

15. The method according to claim 10, which further comprises comparing the estimated differential current values with a differential current threshold value and also generating the fault signal if a predefined number of successive estimated differential current values exceed the differential current threshold value.

16. An electrical protective apparatus for forming a fault signal, the apparatus comprising:

connections for direct or indirect connection to at least two mutually different measurement locations of a component;

an evaluation device connected to receive current measurement values from said connections;

said evaluation device being configured to form differential current values and stabilization values from the current measurement values, wherein said evaluation device forms, from successive differential current values and associated stabilization values, estimated differential current values and associated estimated stabilization values, which are used to estimate at least one value of an expected future profile of the differential current values and the stabilization current values; and

said evaluation device being configured to process a tripping range test and to generate a fault signal if a measurement value pair formed using one of the differential current values and the respectively associated stabilization value lies in a predefined tripping range, wherein said evaluation device evaluates a position of a measurement value pair formed from an estimated differential current value and the respectively associated estimated stabilization value.

17. The electrical protective apparatus according to claim 16, wherein said evaluation device is configured to block an output of the fault signal if a predefined number of successive measurement value pairs lie in a predefined stabilization range.

18. The electrical protective apparatus according to claim 16, wherein said evaluation device is configured to also compare the estimated differential current values with a differential current threshold value and to also generate the fault signal if a predefined number of successive estimated differential current values exceed the differential current threshold value.