Download The importance of trip-free operation and its characteristics

White Paper WP131003EN
Effective September 2015
The importance of trip-free
operation and its characteristics
Anthony T. Ricciuti
Specialist Engineer,
Eaton
One of the many, often desirable characteristics in the specifications and
marketing literature for medium voltage circuit breakers is “Trip-Free.”
Unfortunately, there are many misconceptions about this characteristic.
Definitions
Physical requirements
For IEEET rated products, there are several related
definitions of “Trip-Free”:
For IEEE rated products, if a mechanical opening
release operation is maintained on a medium
voltage circuit breaker, then any closing release
operation signal must not result in contact
movement that reduces the open gap between
the contacts by more than 10%. This characteristic
is often confused with the definition of “Trip-Free.”
•
In the most general definition of “Trip-Free,” the
contacts of the circuit breaker must return to
the open position and remain there when an
opening operation follows a closing operation,
regardless of whether the closing signal, force,
or action is maintained.
•
A common variant is called “Electrically TripFree.” For a medium voltage circuit breaker to
be considered “Electrically Trip-Free,” the circuit
breaker must be able to receive and respond
to an electrical opening signal regardless of
whether an electrical closing signal is energized.
•
“Mechanically Trip-Free” operations refer to a
mechanical release mechanism that can open
the medium voltage circuit breaker regardless
of whether any closing release device operated
by any means is activated or maintained.
•
Medium voltage circuit breakers can also be
“Hydraulically Trip-Free” or “Pneumatically
Trip-Free” if they contain a hydraulic or
pneumatic opening release device (respectively)
that are capable of opening the circuit breaker
regardless of whether any closing release
device operated by any means is activated
or maintained.
Any of these variants of “Trip-Free” operation may
include a “Trip-Free Relay,” in which its operation
alters a closing release circuit, permitting an
opening release to operate unimpeded by a
closing release operation in any state.
For IEC rated products, although the standard
recommends that the suitability for “Trip-Free”
operations should be provided to customers that
are specifying medium voltage circuit breakers,
no specific definition is provided for this function.
However, if any opening release operation is
initiated simultaneously with any closing release
operation signal, contact movement up to and
including a momentary touching of the main circuit
breaker contacts is acceptable before the circuit
breaker completes the opening operation.
Additionally, because electrical opening release
operation circuits typically employ auxiliary switch
contacts internal to the circuit breaker, and therefore the electrical release operation circuit remains
open until the main contacts of the circuit breaker
have closed, when an electrical opening release
operation circuit is maintained, the momentary
touching of the main contacts is acceptable
before the circuit breaker completes the
opening operation.
Summary
Eaton VCP-T, VCP-W, VCP-WC, VCP-WG, and
VCP-WHD medium voltage circuit breakers meet
the IEEE definitions of “Trip-Free,” “Electrically TripFree,” and “Mechanically Trip-Free.”
White Paper WP131003EN
The importance of trip-free operation and its characteristics


Effective September 2015
Eaton medium voltage circuit breaker operation
Preforming this action
While maintaning
Mechanical close
action
Electrical close
signal
Mechanical open
action
Electrical open
signal
On (close) button
mechanically
No effect
No effect
Breaker opens
Breaker opens
On (close) button
electrically
No effect
No effect
Breaker opens
Breaker opens
Off (open) button
mechanically
No contact
movement. Breaker
may discharge
stored energy.
No contact
movement. Breaker
may discharge
stored energy.
No effect
No effect
Off (open) button
electrically
Contact touch
allowed. Breaker
opens and remains
open.
Contact touch
allowed. Breaker
opens and remains
open.
No effect
No effect
Figure 1. Eaton circuit breaker operation
References
About Eaton
C37.04-1999—IEEE Standard Rating Structure for AC High-Voltage
Circuit Breakers, Institute of Electrical and Electronics Engineers,
3 Park Avenue, New York, NY 10016-5997, USA.
Eaton is a power management company with 2014 sales of
$22.6 billion. Eaton provides energy-efficient solutions that
help our customers effectively manage electrical, hydraulic
and mechanical power more efficiently, safely and sustainably.
Eaton has approximately 100,000 employees and sells
products to customers in more than 175 countries.
For more information, visit www.eaton.com.
C37.100-1992—IEEE Standard Definitions for Power Switchgear,
Institute of Electrical and Electronics Engineers, 3 Park Avenue,
New York, NY 10016-5997, USA.
62271-100—IEC International Standard for high-voltage switchgear
and controlgear—alternating-current circuit breakers.
Author
Anthony T. Ricciuti is a Specialist Engineer at Eaton in Pittsburgh, PA.
Anthony has a Bachelor’s degree in Mechanical Engineering from the
University of Pittsburgh, and has more than 20 years of experience
in the design, testing, and analysis of circuit breakers.
Eaton
1000 Eaton Boulevard
Cleveland, OH 44122
United States
Eaton.com
© 2015 Eaton
All Rights Reserved
Printed in USA
Publication No. WP131003EN / Z17245
September 2015
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of their respective owners.