Opening time - for a circuit-breaker tripped by any form of auxiliary energy, the opening time is the time interval between the instant of energizing of the shunt opening release, the circuit-breaker being in the closed position, and the instant when the arcing contacts have separated in all poles.
Definitions (IEC 62271-100): 3.7.136
Post simultaneity requirement during single-closing and single-opening operations
Main contact operating time measurement
Conventional method (one side connected to ground)
Both sides grounded (BSG) method:
a) Tank under voltage circuit breaker
b) Dead tank circuit breakers
c) GIS circuit breakers
Both sides grounded on AIS (live tank)
IEEE Standard 510-1983 "IEEE Recommended Practices for High Voltage and High Power Test Safety"
IEEE Standard 510-1983.
Main contact wire connection for BSG for AIS circuit breakers
BSG - timing in Both Sides Grounded
The same cables are used as for conventional timing
Works correctly for a grounding path resistance ≥10 mΩ
Both sides Grounding timing on the dead tank circuit breaker
The method is based on injecting direct current (a few tens of amperes per phase) through the main circuit and the grounding path and measuring the response signals at the secondary terminals of the current transformer (CT).
Both sides grounded in GIS (gas insulated substation) CB
The method is based on the injection of high DC current through the grounding and main circuit and the simultaneous recording of the response in the secondary of the current transformers (current or voltage).
Contact resistance (static)
IEC56 (IEC62271-100): 50 A ≤I
IEEE C 37.09: 100 A ≤I
Why is high DC current used
The higher the current, the higher the accuracy, contamination and oxidation of the contact surface
According to the standard, a test current as close as possible to the rated current
Some devices can generate up to 800 A
Continuous DTR test for stable results on GIS and Dead Tank circuit breakers
Both sides grounded
Dynamic resistance measurement
The DRM test is performed by injecting a high current through the breaker contact and simultaneously monitoring the voltage drop across the breaker contact during operation.
DRM on Open, Close, CO, O-CO, and O-CO operations!
Important for arcing contact analysis
DRM - measuring principle
Main contact up to 100 microOhm
MilliOhms arc pair contacts
Full DRM test
Contact voltage drop and motion measurements allow calculation of arcing contact sweep
Case Study 1 - DRM Test
The customer wanted to demonstrate the effectiveness of the DRM test
The DRM test was performed at 24 kV of CB oil
Arc contacts in good condition
After disassembly they had intentionally damaged the arcing contact
Damaged arcing contact had been reassembled to CB
DRM test has been performed again
Comparison of DRM results (resistance increase - change in resistance curve)
Case study 2
Periodic commissioning test
The DRM test was performed on the ABB LTB145D1/B
Task: Confirm the status and length of the arcing contacts
After disassembly, the length of the contacts was measured with a caliper and compared with the results of the DRM, and confirmed with the results obtained with the CAT device.
Testing of the operating mechanism
Movement and speed
Motor load time and motor current
Examples of transducer mounting:
Examples of transducer mounting:
Transducer mounting examples.
ABB LTB 245 E1 (245 kV SF6)
SIEMENS 3AP1FI 245 kV
Mitsubishi SF6 138 kV (120-SFMP-40HE)
Motion and velocity measurement - graphical analysis
Speed (average velocity) is calculated between two points on this motion curve.
Contact sweep - total overlap distance of the main and arcing contacts (from the first touch of the arcing contacts to the closed state).