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REAL-TIME MONITORING AND ASSESSMENT OF CIRCUIT BREAKER OPERATIONS FOR DIAGNOSTICS AND CONTROL APPLICATIONS REAL-TIME MONITORING AND ASSESSMENT OF CIRCUIT
BREAKER OPERATIONS FOR DIAGNOSTICS AND
CONTROL APPLICATIONS

M. Kezunovic , G. Latisko, N. Ved
Texas A&M University, College Station, TX 77843-3128

Abstract
Circuit breakers (CBs) are very important elements in the power system. They
are used to switch other equipment in and out of service. Circuit breakers need
to be reliable since their incorrect operation can cause major issues with power
system protection and control. Todays practice in monitoring circuit breaker
operation and status in real time is reduced to the use of Remote Terminal Units
(RTUs) of Supervisory Control and Data Acquisition (SCADA) system to assess
CB status. More detailed information about the control circuit performance may
be obtained by CB test equipment typically used for maintenance diagnostics [1].

This paper addresses two important issues: a) how improved CB monitoring
may be implemented in real-time, and b) what would be the benefits of such an
implementation.

The results reported in this paper are coming from two research projects,
conducted using funding from CenterPoint Energy and DOE-CERTS aimed at
development of software for automated analysis of CB data and the other
covering development of the CB data acquisition unit respectively.

The paper is devoted to description of a prototype implementation of a real-time
CB monitoring system. The system consists of a new CB monitoring data
acquisition IED that is located at circuit breaker and captures detailed
information about its operation in real-time. The CB files are transferred to the
concentrator PC where the application software performs automated analysis
and makes an assessment about the operational status of the breaker. The
software is based on signal processing and expert system processing. Application
example using actual field data is discussed.

The paper ends with some conclusions, acknowledgments and a list of
references. Introduction
System wide real-time monitoring of circuit breaker operation and statuses
currently is implemented using Remote Terminal Units (RTUs) of Supervisory
Control and Data Acquisition (SCADA) system. Based on detected voltage levels
on circuit breaker contacts, these units are providing information on final
statuses of the circuit breakers such as OPEN or CLOSE. The transitions in
time of control signals, such as Trip or Close Initiate, X and Y coil currents,
Control and Yard DC voltages, Closing Coil and others, used by protection and
maintenance engineers for evaluation of CB performance cannot be monitored
using RTU and SCADA approach.

A solution called Circuit Breaker Monitoring and Analysis (CBMA) developed at
Texas A&M University, intends to solve described problems by integrating
customized software and hardware solutions into a single, real-time monitoring
and analysis system.

The system for real-time monitoring and analysis of circuit breaker operations
described in this paper is an extension of widely used portable circuit breaker
testing device concept [2]. The traditional testing devices are temporally
connected to the circuit breakers control circuit to record analog and digital
signals. The operator opens and closes the circuit breaker each time the test is
performed and data are recorded. The traditional analysis is done manually by
overlaying traces from a good case recorded earlier and making a judgment of
how different the new case is.

The new solution is based on a new CB monitoring data acquisition IED called
Circuit Breaker Monitor (CBM) which would be permanently connected to the
substation CBs. CBM captures detailed information about each CB operation in
real-time, regardless of whether the operation is initiated manually by the
operator or automatically by the protection and control equipment and stores
them in COMTRADE file format [3], [4]. As soon as the relevant CB control
circuit signals are recorded and transmitted by wireless link to the concentrator
PC, analysis software automatically performs the analysis.

CBMA provides better understanding of the condition and operating
performance of each individual breaker by monitoring and analyzing expanded
set of analog and digital signals from circuit breaker control circuitry. The
advanced signal processing algorithms and knowledge base of the expert system
implemented in the analysis software, significantly improve the reliability and
consistency of the analysis results. Thanks to the fast and low cost CBM devices,
new monitoring and control system described in this paper, enables permanent, real time monitoring of status and performance of circuit breakers for the entire
network.

In the first section of the paper, architecture of the whole system and basic
processing algorithm are described. Second section explains the structure and
basic functions of the hardware part of the system. Focus of the following section
is on the organization of analysis software of the CBMA system. Basic building
blocks, such as signal processing and expert system are elaborated and brief
overview of knowledge base rules is given. At the end, an example of the stuck
breaker case is illustrated with waveforms of relevant signals and expert system
rules involved in problem detection process.

Architecture of CBMA system
The CBMA system supports client/server architecture. The client part resides in
substation. It consists of the CBM devices attached to the CBs and a software
running on concentrator PC, both permanently installed in the substation, as
shown in Figure 1.


Figure 1
CBMA system architecture

When breaker operates, recorded files are wirelessly transmitted to the
concentrator PC. The client application automatically performs the analysis of
recorded signals from the circuit breaker control circuit. For more efficient data
manipulation, IEEE file naming convention is used for naming the recordings
files [5]. The signal processing module of the analysis software extracts various
parameters from recorded signal samples and expert system evaluate them against empirically obtained values and tolerances selected for specific type of
circuit breaker.

The resulting report describes detected abnormalities and possible causes of the
problem. If discovered problem presents serious threat to the reliability of future
circuit breaker operation, programmable notification is sent to the server located
in the central office. The notification is then processed and a warning is sent via
email or pager to the maintenance and protection personal. Reporting is
provided for both local and geographically dislocated users through
implementation of local database and web server supporting information
exchange through dynamic HTML pages.

Recorded files and reports can be downloaded to the server via Ethernet network
relying on standard, fast and reliable TCP/IP protocol. In the central office or
control center, the server part of CBMA consisting of the analysis module, a
central database and master web server is running. The central database allows
for easy archiving and retrieving of the records and analysis reports from all
system substations. Master web application allows remote users to search for the
records and/or analysis reports from anywhere on the corporate network
(intranet).

Description of CBMA hardware
The system hardware in substation consists of circuit breaker monitors located
on each breaker in the switch yard and a concentrator PC, used for gathering
data, placed in the control room.

Circuit Breaker Monitor IED
The circuit breaker monitor IED (CBM) has three main tasks:
Perform data acquisition of signals from the Circuit Breaker control circuit
and record sequences of tripping and closing
Convert captured signals into files according to COMTRADE file
specifications
Transmit files wirelessly to the concentrator device.



Control
DC +
Control
DC _
52
TC
CC
52
Close
Initiate
Trip
Initiate
52a
52Y/