Section 3. Entelliguard Tu Trip Unit System; Introduction; Reliability Without Compromising Protection; Arc Flash And The Entelliguard Tu Trip Unit - GE EntelliGuard G Application Manual

DET-653C
24-May-12
EntelliGuard G Power Circuit Breaker

Section 3. EntelliGuard TU Trip Unit System

Introduction

The EntelliGuard TU Trip Unit offers optimum circuit
protection and optimum system reliability simultaneously
with little or no compromise to either of these critical
functions. Reliability and arc flash protection, in one
package, at the same time, all the time.
EntelliGuard TU series trip units are available as the
standard controller for new production EntelliGuard G
ANSI/UL 1066, UL 489 and IEC circuit breakers. EntelliGuard
TU designs are also available as direct, functional
replacements for GE's PowerBreak, PowerBreak II, WavePro,
AKR, and AK circuit breakers. EntelliGuard TU trip units are
also available in kit form for many popular non-GE and older
GE low voltage power circuit breakers (Refer to DEH-4567).
The EntelliGuard® TU technology is also available in GE's
molded case Spectra Breaker line 400A-1200A. The Spectra
MET (microEntelliGuard) includes the innovative RELT and
Zone Selective Interlocking- Instantaneous feature. New, on-
board features and communications capabilities enable
equipment enhancements, improved operational
performance and life extension programs. Performance will
vary based on associated circuit breaker and equipment
conditions. All EntelliGuard TU Trip Units are Conformal
Coated for increased reliability in humid/damp
environments.
This section describes the functions as implemented in the
EntelliGuard G UL 489 and ANSI/UL 1066 circuit breakers.
References or comparisons to other GE circuit breakers are
for informational purposes only.

Reliability without Compromising Protection

Reliable protection of circuits and equipment has always
been the circuit breaker's primary mission. Providing
appropriate protection of the conductors, while preserving
selective coordination, has been the primary focus of most
system designers. However, what was acceptable in the
past is no longer the standard today.
Modern economic reality, coupled with strict regulatory
requirements, demand optimal system performance with
increased sensitivity to the inherent power system hazards
that face operating and maintenance personnel. Safety
agencies, local authorities and owner-operators demand
better personnel protection and state-of-the-art capabilities
to minimize hazards while simultaneously preserving critical
loads and system capabilities.
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EntelliGuard
Section 3. EntelliGuard TU Trip Unit System
These requirements often seem to be, and sometimes are, in
conflict, pitting the speed and sensitivity required to improve
arc flash protection against the delays and deliberate
decision making required to maximize power system
reliability. The EntelliGuard TU, along with the EntelliGuard
family of circuit breakers, offers flexible solutions for
demanding circuit protection and circuit preservation
environments. The EntelliGuard TU is designed to provide the
utmost in system protection and reliability simultaneously,
with little or no compromise.

Arc Flash and the EntelliGuard TU Trip Unit

Reducing arc flash hazard is a primary concern in many
power system designs. The best way to ensure the lowest
possible hazard for a particular distribution system is to
consider the hazard as the system is designed and make
careful selection of the system's topology, circuit sizes,
equipment sizes and protective devices to minimize hazard
for the operating and maintenance personnel that will need
to use the system for years to come.
The EntelliGuard TU, especially in conjunction with the
EntelliGuard G circuit breaker, provides significant flexibility
towards solving arc flash hazard problems without
excessive sacrifice of system reliability, in terms of
selectivity.
The next three to four pages are an overview of the
EntelliGuard TU's unique features enabling Arc Flash
mitigation and selectivity at the same time. When the
downstream breaker/fuse is current limiting, the Waveform
Recognition Selective Instantaneous is used to achieve lower
Instantaneous pickup settings while maintaining selectivity.
This is very effective for 250A and below devices. For Feeder
devices above 250A, the Instantaneous Zone Selective
Interlocking (I-ZSI) feature is used to achieve selectivity and
arc flash mitigation at the same time. The I-ZSI feature is
available on Spectra MET and EntelliGuard® TU in the
following breakers: EntelliGuard G, Power Break II, WavePro,
AK/AKR, and Conversion Kits. By combining the Waveform
Recognition Selective Instantaneous and I-ZSI, a system with
a 100KAIC bolted fault current can achieve a 8 cal/cm2 or
less incident energy level.
One way to lower potential incident energy is to ensure that
circuit breakers are able to interrupt using their
Instantaneous trips for all expected arcing faults. Figure 3.1
shows the expected arcing currents for 480V systems for
various arc gaps representative of switchgear (32mm),
switchboards (25mm), MCCs (25mm) and panelboards
(13mm). These values were determined using IEEE standard
1548, Guide for Performing Arc-Flash Hazard Calculations,
2002.
® G Circuit Breaker Application Guide
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