circuit breaker - pqpm system application for circuit breakers & reclosers

7/31/2019 Circuit Breaker - PQPM System Application for Circuit Breakers & Reclosers

1/30

Power Quality Predictive Maintenance (PQPM)Systems Application for Circuit Breakers and

Reclosers

Predictive Maintenance through Monitoring

1000561


2/30


3/30


4/30


5/30


6/30


7/30


8/30


9/30

ix

CONTENTS1 POWER QUALITY PREDICTIVE MAINTENANCE (PQPM) SYSTEM APPLICATION FORCIRCUIT BREAKERS AND RECLOSERS............................................................................. 1-1

Circuit Breaker Introduction ............................................................................................... 1-1 Application of Power Quality Monitors for On-Line Monitoring of Breaker Condition.......... 1-3 Maintaining and Testing Circuit Breakers .......................................................................... 1-5

Different Maintenance Strategies................................................................................. 1-6 Testing Circuit Breakers .............................................................................................. 1-6

Application of Power Quality Monitoring System for Breaker Maintenance........................ 1-8 Limitation of Power Quality Monitoring System for Breaker Maintenance .................... 1-8 Circuit Breaker Main Contact Time Variation ............................................................... 1-9 Circuit Breaker Protection for Failure to Close ............................................................1-10 Protection for Current Through an Open Breaker .......................................................1-10 Maintenance Scheduling Based on Breaker Operation...............................................1-10 Circuit Breaker Emergency Load-Current-Carrying Capability ....................................1-11

Reclosers.........................................................................................................................1-13 Existing Maintenance Practices for Reclosers ............................................................1-14 Application of Duty Factor for Determining Maintenance Basis...................................1-15 Application of a PQPM System for Reclosers.............................................................1-15

References.......................................................................................................................1-17


10/30


11/30


12/30


13/30


14/30


15/30


16/30


17/30

1-7

testing, it is also possible or even necessary to look at the different waveforms as uniquesignatures for an individual breaker [2, 3]. This may also be utilized when measuring a circuitbreaker in-service, online, and under load.

It is important to understand that the signature data are not precise single-numbered values for apass-fail decision. Instead, the signature should be used for comparisons with benchmarks,ideally taken from the same breaker or at least from the same circuit breaker type. Comparingsignatures by using overlays has proven to be a reliable method of detecting important changesin breaker performance.

The following parameters can be measured and evaluated during in-service testing:

Trip and Close-Coil Currents

Measuring the trip and close-coil current reveals interesting data, such as maximum current,latch release time, and current interruption time. The current waveform for the individual breakeris unique and is a good indicator of circuit breaker performance [4].

Auxiliary (A/B) Contact Timing

As in many condition-monitoring systems, the auxiliary contacts can be used as an indirectmeasurement of the main contact. The switching times of the A/B contacts are correlated to themain contact timing, and, depending on the actual design of the breaker, the statistical deviationbetween the two may be very small. Within the limitations of the breaker design, the A/B contacttime provides an accurate and repeatable reference for the main contact timing [5]. Auxiliarycontacts are used for this, but where breakers are in critical locations, the use of these contactshas not proven reliable. Current is monitored as an indication of operation rather thandetermining if a breaker has operated properly by noting whether the A switch has opened.This is a positive point for in-service monitoring.

Travel Motion

If the design of a circuit breaker allows a linear or rotary transducer to be mounted at a safedistance inside the mechanism, a travel-motion measurement is no different than an off-line test.From the travel-motion trace, numerous parameters such as average and instantaneous velocity,stroke, wipe, and damping can be calculated automatically. When using rotary transducers, therecorded travel-motion trace is often different from the manufacturers specification. Use of conversion tables [6] is a way to overcome this problem and make it possible to do directcomparisons with the manufacturers data.

Load Current/Main Contact Timing

Using the secondary current from the measurement transformer for the circuit-breaker current, itis possible to measure the load current by using a Hall-effect clamp-on current sensor. From thewaveform and depending on the actual test setup, contact closing, contact opening, and themoment when arcing is extinguished may be detected.


18/30


19/30


20/30


21/30


22/30

1-12

temperature for an emergency period of 4 hours, or 10C above for an emergency period of 8hours. The factors are expressed as the ratio of emergency load current allowed at an ambienttemperature of 40C I e to the rated continuous current I r and can be applied with the followingrestrictions:

The circuit-breaker component with the highest values of limiting temperatures, max and r , shall be used to select the proper emergency load-current-carrying capability factorfrom Table 1-1. Unless rated otherwise by the manufacturer, contacts and conducting

joints in other than oil or air are assumed to have the temperature limitations of silver,silver alloy, or equivalent materials in air (65C hottest-spot temperature rise, 105Chottest-spot total temperature).

The four-hour factor shall be used for a cycle of operation consisting of separate periodsof no longer than 4 hours each, with no more than four such occurrences beforemaintenance.

The eight-hour factor shall be used for a cycle of operation consisting of separate periodsof no longer than 8 hours each, with no more than two such occurrences before

maintenance. Each cycle of operation is separate, and no time-current integration is permissible to

increase the number of periods within a given cycle. However, any combination of separate four-hour and eight-hour emergency periods may be used, but when they total 16hours, the circuit breaker shall be inspected and maintained before being subjected toadditional emergency cycles.

Emergency Operation at an Ambient Temperature Other Than 40C

When a circuit breaker is operating at an ambient temperature other than 40C, the emergencyload-current-carrying capability I ea can be calculated by the equation:

8.11

8.1

r

e8.1

r

area 1I

III

II

+

= (1-1)

where,

Iea = emergency load current in amperes at actual at actual ambient temperature.

Ir = rated continuous current amperes.

Ie = emergency load current in amperes at 40C ambient temperature.

r

a

I I

=8.1

1

max

r

a

(1-2)

where,

max = allowable hottest spot total temperature.

a = actual ambient temperature.


23/30


24/30

1-14

Most of the faults on overhead distribution lines are temporary in nature. These includelightning, conductor slap, animal contact, and tree contact. The repeater fuse, a concept that hasbeen used in the past, is based on a premise of temporary faults. Under such an arrangement, if afuse is blown, then a second and, if necessary, third fuse are automatically inserted into thecircuit. The success of this scheme led to the development of automatic circuit reclosers. These

are self-controlled interrupting devices that sense fault currents and step through a predeterminedsequence of opening and reclosing operations, followed by resetting, hold-closed, or lockout.Typical recloser specifications include:

Voltage rating. Continuous current rating. Interrupting current rating. Minimum tripping current. Operating or time-current characteristics. Operating sequence.

Reclosing interval. Reset time.

Reclosers are manufactured in single-phase and in three-phase units with mechanical orelectronic control with an interrupting medium of vacuum or oil.

Existing Maintenance Practices for Reclosers

ANSI C37.61-1973, IEEE Standard Guide for the Application, Operation, and Maintenance of Automatic Circuit Reclosers, outlines the maintenance issues that are related to reclosers. In theabsence of manufacturer-specific instructions, a suggested method is to conduct maintenance andinternal inspection at every 100 operations or every three years, whichever occurs first. However,

operating experience with particular designs is the best basis for the establishment of maintenance schedules. Typical inspection procedures include:

Reviewing the overall condition of reclosers by examining insulators, surge arrestors,mounting hardware, brackets, clamps, and ground connection.

Recording the number of operations. Checking connections for signs or corrosion or overheating. Manually opening and closing the recloser to check operation if equipped with by-passes.

Maintenance of lower-voltage reclosers can involve the removal of existing units and replacingthem with overhauled units. Maintenance of regulators involves:

Replacing oil (for oil reclosers). Cleaning or replacing bushings and gaskets. Checking the timing sequence of curves and the number of lockouts. Inspecting internal components, arc interrupters, and contacts.

If the reclosers are electronically operated, the power supply and battery are tested too.


25/30


26/30

1-16

CB PQ

MONITOR

100 kvar Fixed

Substation Secondary Bus

R

R

R

CB

100 kvar Fixed

R

100 kvar Fixed

Figure 1-2Recloser Location on Distribution Feeders

A number of recloser manufacturers provide optional control and communication packages thathave built-in data-acquisition capability that is similar to a power quality monitor. Data fromthese controllers can be interfaced with a utilitys SCADA systems. Historical analysis of thisdata can provide intelligent scheduling of recloser maintenance. One such system is the SEL-351R recloser control that has built-in intelligent recloser maintenance scheduling.

The recloser wear-monitor algorithm of SEL 351R measures the line current at the time of thetrip and the number of close-to-open operations as a means of monitoring recloser wear. Everytime the recloser trips, the relay records the magnitude of the raw current in each phase. Thiscurrent information is integrated on a per-phase basis. When the result of the integration exceedsa threshold, an alarm can be initiated. The set points for the threshold are based on therecommendations for reclosers in ANSI C37.61-1973 or can be user-defined. Only the reclosertype (oil or vacuum) and the interrupt rating are required for the evaluation.


27/30

1-17

References

[1] J. Reason, Circuit Breakers with On-line Condition Monitoring, Electrical World, February 1995.

[2] M. Ohlen, H. Wernli, and W. Dueck, Dynamic Resistance MeasurementsA Tool forCircuit Breaker Diagnostics, in Proceedings of the IEEE/KTH Stockholm PowerConference, Stockholm 1995.

[3] M. Runde et al, Vibration Analysis for Diagnostic Testing of Circuit Breakers, inProceedings of the 1996 IEEE Winter Meeting, Baltimore, 1996.

[4] W. Dueck, Interpretation of Circuit Breaker Operating Coil Signatures, in Proceedings of the 1997 Programma Circuit Breaker Test & Maintenance Conference, Pittsburgh, 1997.

[5] P. Hadorn et al, Reasons for Continuous Circuit Breaker Time Monitoring and Proposal for

a Simple Realization, in Proceedings of the IEEE/KTH Stockholm Power Conference,Stockholm, 1995.

[6] R. Burnett, SFA Timing Test Results, in Proceedings of the Programma TM1600 UserGroup Meeting, Chicago, 1994.

[7] G. Johansson, On-Line Measurements on Circuit Breakers, Private Correspondence, 1997.


28/30


29/30


30/30

About EPRI

EPRI creates science and technology

solutions for the global energy and energy

services industry. U.S. electric utilities

established the Electric Power Research

Institute in 1973 as a nonprofit researchconsortium for the benefit of utility members,

their customers, and society. Now known

simply as EPRI, the company provides a wide

range of innovative products and services to

more than 1000 energy-related organizations

in 40 countries. EPRIs multidisciplinary teamof scientists and engineers draws on a

worldwide network of technical and business

expertise to help solve todays toughest

energy and environmental problems.

EPRI. Powering Progress

2000 Electric Power Research Institute (EPRI), Inc. All

rights reserved. Electric Power Research Institute and EPRIare registered service marks of the Electric Power ResearchInstitute, Inc. EPRI. POWERING PROGRESS is a servicemark of the Electric Power Research Institute, Inc.

1000561

Printed on recycled paper in the United States of America

EPRI 3412 Hillview Avenue, Palo Alto, California 94304 PO Box 10412, Palo Alto, California 94303 USA800.313.3774 650.855.2121 [email protected] www.epri.com

circuit breaker - pqpm system application for circuit breakers & reclosers

Documents