Eaton Digitrip 3000 series - 1-4 STANDARDS; SECTION 2: FUNCTIONAL DESCRIPTION; 2-1 PROTECTION, TESTING AND COMMUNICATION CAPABILITIES; 2-1.1 RMS SENSING

Instruction Leaflet DT3000
Page 6 Effective: Date 07/02 I.B. 17555D
For more information visit: www.cutler-hammer.eaton.com
Supersedes I.B. 17555C dated November 1999
Fig. 1-5 Installed Jumpers in Place on Terminal Block
TB-1 Disabling the Zone Interlocking Feature
In addition to being able to provide a circuit breaker
“OPEN” or “CLOSED” status to the remote location, the
Digitrip 3000 displays and remotely transmits parameters,
such as:
• Individual phase currents
• Ground current
• Maximum current for each phase and ground since
last reset (A Demand)
• Magnitude and phase of current causing trip
• Cause of trip
• Current transformer ratio
• Existing set point settings
• Software Version
The remote communications capability is made possible by
the Cutler-Hammer Integrated Communications (INCOM)
Chip and Protocol which is compatible with the Power-Net
Monitor and Control System. Reliable two-way
communications can be provided over a twisted pair
communications network. The protocol permits a remote
master computer to perform:
1) Interrogation of relay data
2) Execution of circuit breaker “Close” and “Trip”
commands
3) “Reset” of the relay after a trip
4) Downloading of settings
1-4 STANDARDS
Digitrip 3000 Protective Relays are “Component
Recognized” by the Underwriters Laboratory, Inc.® under
UL File E154862. Refer to Section 2-3 UL Testing and
Specification Summary for more information.
SECTION 2: FUNCTIONAL DESCRIPTION
2-1 PROTECTION, TESTING AND COMMUNICATION
CAPABILITIES
2-1.1 RMS SENSING
Digitrip 3000 Protective Relays provide true RMS sensing
for proper correlation with the thermal characteristics of
conductors and equipment. The root-mean-square (rms)
value is determined by a microprocessor calculation of
discrete sampled points of the current waveform. This rms
value is used for the protection response and metering
displays of the relay.
2-1.2 PICKUP SETTING
A Digitrip 3000 Protective Relay pickup setting is a
discrete, pre-selected value of current used to initiate a
tripping action. The Digitrip 3000 has several current
based tripping functions:
• Phase inverse time overcurrent tripping - Thermal,
ANSI, and IEC Curves.
• Ground inverse time overcurrent tripping - Thermal,
ANSI, and IEC Curves.
• Phase and ground short delay tripping.
• Phase and ground instantaneous tripping.
AS SHOWN IN FIGURE 3-2, THE ANSI AND IEC
“CURVE SHAPES” ARE IN TERMS OF MULTIPLES OF
I
PU
(PICKUP CURRENT OF THE CT PRIMARY),
WHEREAS ‘SHORT DELAY’ AND “INSTANTANEOUS”
ARE IN TERMS OF MULTIPLES OF I
N
(5A SECONDARY
OF CT PRIMARY CURRENT). THE THERMAL CURVE IS
REPRESENTED IN TERMS OF MULTIPLES OF I
N
FOR
ITS CURVE SHAPE, SHORT DELAY, AND
INSTANTANEOUS SETTINGS. THIS MUST BE
CONSIDERED IN THE COORDINATION STUDY AND IN
THE PROGRAMMING OF THE DIGITRIP 3000
PROTECTIVE RELAY.
EXAMPLE: THERMAL CURVES, SHORT DELAY AND
INSTANTANEOUS SETTINGS USING I
N
Ct Rating = I
n
= 1200A
Pickup Setting = 1.5
Pickup (amperes) = (1 200)(1 .5)
= 1800A
Example: ANSI and lEC curves using I
pu
Ct Rating = 1200A
I
pu
= Pickup Current = 1800A