Method for phase controlled energizing of power transformer

Patent metadata

Field	Value
Publication number	US-11245254-B2
Application number	US-201616327809-A
Country	US
Kind code	B2
Filing date	Aug 23, 2016
Priority date	Aug 23, 2016
Publication date	Feb 8, 2022
Grant date	Feb 8, 2022

Abstract

A method for phase controlled energizing of a power transformer includes acquiring electrical voltage signal from a voltage sensing device connected to the power transformer. Determining a first characterizing data in the voltage signal within a pre-determined set of cycles at about an opening operation of a circuit breaker and determining a second characterizing data within the pre-determined set of cycles in the voltage signal subsequent to the opening operation of the circuit breaker. Estimating a level of magnetization of the core of the power transformer based on at least one of second characterizing data, and the first characterizing data and the second characterizing data. Operating the circuit breaker at a determined instant of switching based on the estimated level of magnetization for a phase controlled energizing of the power transformer by the circuit breaker.

First claim

The invention claimed is:

1. A method for phase controlled energizing of at least one power transformer in an electrical system wherein the power transformer is connected to a circuit breaker operated by a controller for performing controlled switching, the circuit breaker connected between at least one phase of a power source and a winding of the power transformer; the method comprising:
acquiring an electrical voltage signal from a voltage sensing device connected to the power transformer;
determining a first characterizing data in the acquired electrical voltage signal within a pre-determined set of cycles, the first characterizing data representative of an aspect characteristic to the acquired electrical voltage signal within the pre-determined set of cycles at about an opening operation of the circuit breaker, the aspect characteristic based on at least one of a shape of a waveform pattern, a co-efficient of Fast Fourier transform, an area under a curve, a peak value, a Root Mean Square value, or a measurement at a particular phase of the electrical voltage signal corresponding to at least a subset of the pre-determined set of cycles;
determining a second characterizing data within the pre-determined set of cycles in the acquired electrical voltage signal subsequent to the opening operation of the circuit breaker, the second characterizing data representative of the aspect characteristic to the acquired electrical voltage signal within the pre-determined set of cycles subsequent to the opening operation of the circuit breaker;
estimating a level of magnetization of a core of the power transformer based on a comparison between the first characterizing data and the second characterizing data;
determining an instant of switching in at least one phase of the power source based on the estimated level of magnetization; and
operating the circuit breaker at the determined instant of switching for a phase controlled energizing of the power transformer.

2. The method as claimed in claim 1 , wherein estimating a level of magnetization comprises categorizing the levels of magnetization into one of a full de-magnetization level, a partial de-magnetization level, or a zero de-magnetization level.

3. The method as claimed as claim 1 , wherein categorizing the levels of magnetization is based on a shape related aspect of the second characterizing data.

4. The method as claimed in claim 1 , wherein the second characterizing data comprises a waveform pattern of the acquired voltage signal.

5. The method as claimed in claim 1 , wherein estimating a level of magnetization of core of the power transformer includes comparing the first and second characterizing data.

6. The method as claimed in claim 1 , wherein the second characterizing data is based on at least one of a form factor of the acquired electrical voltage signal, a waveform pattern of the acquired electrical voltage signal, a co-efficient of a Fast Fourier transform of the acquired electrical voltage signal, a time period value derived from the acquired electrical voltage signal, an area under a curve of the acquired electrical voltage signal, a peak value of the acquired electrical voltage signal, a Root Mean Square value of the acquired electrical voltage signal, a measurement at a particular phase of the acquired electrical voltage signal, or a processed value derived from the acquired electrical voltage signal.

7. A controller configured to operate at least one circuit breaker connected between a power transformer and at least one phase of a power source, the controller comprising:
one or more processors configured to:
acquire an electrical voltage signal from a voltage sensing device connected to the power transformer over a time period corresponding to a predetermined set of cycles beginning with an opening operation of the at least one circuit breaker connected between the at least one phase of the power source and a winding of the power transformer;
determine a characteristic of the electrical voltage signal corresponding to the time period, the characteristic based on at least one of a shape of a waveform pattern, a co-efficient of Fast Fourier transform, an area under a curve, a peak value, or a Root Mean Square value of the electrical voltage signal corresponding to at least a subset of the time period;
based on the characteristic, estimate a magnetization level of a core of the power transformer corresponding to the winding;
determine a switching time for at least one phase of the power source based on the estimated magnetization level; and
operate the circuit breaker at the switching time to cause a phase controlled energizing of the power transformer.

8. The controller as claimed in claim 7 , wherein the controller is further configured to operate the circuit breaker at a phase angle of at least one phase of the power source wherein the phase angle corresponds to the determined switching time for a phase controlled energizing of the power transformer.

9. The method as claimed in claim 1 , wherein the predetermined set of cycles comprises at least two cycles.

10. A method for phase controlled energizing of a power transformer, the method comprising:
acquiring an electrical voltage signal from a voltage sensing device connected to the power transformer over a time period corresponding to a predetermined set of cycles beginning with an opening operation of a circuit breaker connected between at least one phase of a power source and a winding of the power transformer;
determining a characteristic of the electrical voltage signal corresponding to the time period, the characteristic based on at least one of a shape of a waveform pattern, a co-efficient of Fast Fourier transform, an area under a curve, a peak value, a Root Mean Square value, or a measurement at a particular phase of the electrical voltage signal corresponding to at least a subset of the time period;
based on the characteristic, estimating a magnetization level of a core of the power transformer corresponding to the winding;
based on the estimating, determining a switching time for the at least one phase of the power source; and
operating the circuit breaker at the switching time to cause a phase controlled energizing of the power transformer.

11. The method as claimed in claim 10 , wherein the estimating include categorizing the magnetization level into one of a full de-magnetization level, a partial de-magnetization level, or a zero de-magnetization level.

12. The method as claimed in claim 10 , wherein the characteristic further comprises a phase of the electrical voltage signal corresponding to at least a subset of the time period.

13. The method of claim 10 , wherein the predetermined set of cycles comprises at least two cycles.

Assignees

• Hitachi Energy Switzerland Ag

Inventors

• Parikh Urmil
• Stanek Michael

Classifications

• H01H9/56

  for ensuring operation of the switch at a predetermined point in the AC cycle · CPC title

• H02H7/04

  for transformers · CPC title

• H02H3/06

  with automatic reconnection · CPC title

• H01F27/42

  Circuits specially adapted for the purpose of modifying, or compensating for, electric characteristics of transformers, reactors, or choke coils (circuits for controlling transformers, reactors or choke coils, for the purpose of obtaining a desired output H02P13/00; impedance networks H03H) · CPC title

• H02H1/0092

  concerning the data processing means, e.g. expert systems, neural networks · CPC title