Page 52 - Energize June 2022

Figure 5: Voltage based timing measurement (Megger)

verifying that the breaker operates within specified operation parameters. Standard test and logs the following information during
voltage is 85% (and 70%) of nominal voltage for close (and open). 5 circuit breaker operation:
The value of the operating voltage affects the operation of the coil as shown in Figure 6. • Trip time (ms) (also known as opening
time)
On line monitoring system for switchgear testing • Arc duration (ms) (phase segregated)
Online testing and monitoring allows the performance to be measured in-circuit. There are • Clearing time (ms) (also known as
some test and performance test methods which are easier to perform online than using test interrupting time)
2
apparatus. Online monitoring gives an indication of the performance of the switch under real • Cumulative I T or IT on the main
operating conditions, and can provide information not available with online testing. contacts (phase segregated) from arcing
• Restrike occurrence (phase segregated)
Breaker performance monitoring is ideally suited for implementing predictive maintenance, • Operation counts
maintenance deferral, condition-based maintenance and increased environmental protection
from SF6 gas leaks. It monitors the condition of the main contacts, mechanism and dielectric, References
1. D Genutis: “Top five switchgear failure causes”,
NETAWorld, 2010.
2. T Raudon: “On-site non-intrusive testing of
AC circuit-breakers”, CIGRÉ A3-069, CIGRÉ,
Winnipeg 2017 Colloquium.
3. A Subramanium, et al: “Switchgear condition
assessment and lifecycle management:
standards, failure statistics, condition
assessment, partial discharge analysis,
maintenance approaches, and future trends”,
IEEE electrical insulation magazine, April 2021.
4. G Paoletti, et al: “Failure contributors of mv
electrical equipment and condition assessment
program development”, IEEE Transactions on
Industry Applications, December 2002.
5. Megger: “Recommended circuit breaker tests”,
https://megger.com//applications/circuit-
breakers/recommended-circuit-breaker-tests.

Send your comments to
Figure 6: Coil current profile for different voltage from 0,25% to 1,25% of nominal voltage 3 rogerl@nowmedia.co.za

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