General lnformation
Overcurrent Protection Conf igurations
Static Trip lll trip units are available in six basic overcurrent
protection configurations to meet specific protection require-
ments, All trip units have Long Time fault protection with
switchable thermal memory. This is designated by the suffix
identifier T immediately following the letters RMS in the catalog
number designation. AII trip units include the LCD target
indicator and fault pickup LED's. The "-T" suffix after the basic
overcurrent protection identifier shows the LCD target is pro-
vided. Zone interlocking capability is also standard on trip
units with short time or ground fault protection, but additional
components and wiring are required to connect trip units
together into a functioning zone-interlocked system. fhe "2"
suffix indicates zone interlocking capability. Available protec-
tion conf igurations are:
Protection Conf iguration
Long Time/lnstantaneous
Long Time/Short Time
Long Time/Short Time/lnstantaneous
Long Time/lnstantaneous/Ground Fault
Long Time/Short Time/Ground Fault
Long Time/Short Time/l nstantaneous/
Ground Fault
LCD Targets
A custom liquid crystal display (LCD) provides a visual indica-
tion of an overcurrent tripping action. Target retention is
provided by capacitive stored energy in the trip unit, eliminat-
ing the need for batteries. ln addition to the tripping informa-
tion, improper operation of the protection microprocessor is
displayed on the LCD. The displayed legends are:
o OVERLOAD - long time delay tripping
. SHORTCIRCUIT-shorttime delayor instantaneoustripping
. GROUND FAULT - ground fault delay tripping
o DISABLED - watchdog circuit indicates protection micro-
processor not f unctioning properly
Communications and Metering Functions
Static Trip lllC trip units meter and communicate phase cur-
rents; Static Trip IIICP trip units meter and communicate
currents, voltages, power, and energy information. Neutral
and ground current metering is available on both models. (See
table for list of parameters measured.)
A second microprocessor, referred to as the communications
microprocessor, is used in these trip units to implement the
communications and metering functions, A green "Comm
Watch' LED, visible from the front of the trip unit, provides a
visual indication of the operation of the second microproces-
sor. When the control powei is present and the microprocessor
is passing the built-in-test routine, the LED blinks with a half-
second pulse every three seocnds. A burst of pulses also
occurs whenever the trip unit is communicating to a master
device via the RS-485 port at the back of the unit.
The same current sensors, used in the overcurrent protec-
tion function, are used in the current metering function.
Special purpose Potential Transformer (PT) modules are
used in measuring the voltages, (see Accessories section).
The accuracy of the integrated digital metering functions
is comparable to separate traditional analog instrumentation.
O lncluded when ground fault protection specified
@ Requ res "N" option and neutral current sensor
O Only displayed for four wire systems
Two communications ports are available from which to read
the metered data. A port on the front of the trip unit provides
access for local monitoring with the Siemens BDU Breaker
Display Unit, (see Breaker Display Un t section). A port on the
back of the trip unit allows the trip unit to be integrated into
the Siemens ACCESSTT/ electrical distribution communica-
tion system. The metered data can be displayed at a Power
MonitorrNa panel or personal computer. Network communica-
tions are over a shielded twisted pair data bus, SEAbus. The
real-time clock in the trip unit is periodically synchronized with
a master clock in the network for accurate, to the second, time
stamping of events.
Extended Protective Relaying
Static Trip ll|CPX trip units provide the same overcurrent
protection, communications, and metering as the Static Trip
lllCP model plus seven additional protective relaying func-
tions. The protection functions have independent pickup
thresholds and delays. The pickup and delay set-points may
be accessed and set remotely via the communications bus
or locally via the BDU Breaker Display Unit, (see Breaker
Dlsplay Unit section), Adjusting of the set-points is protected
by a password to preventtheir being changed by unauthorized
personnel. Viewing of the set-point values is unprotected.
Identifier
RMS-TI-T
RMS-TS.TZ
RMS-TSI-TZ
RN/S-TIG-TZ
RN/S-TSG-TZ
RMS-TSIG-TZ
v
Metering Functions
Measured
Parameiers l\ilodel
iltc iltcP
Phase Current
Avg. Phase Currents
Ground Current O
Neutral Current O oni on1
Phase Voltages O
Avg. Phase Voltage O
Line Voitages
Avg. Line Vo tage
kW Demand
kW Hours
kW Hours Reverse
KVAR
kVAR Hours
Power Factor
Freq uency
v
