GE MULTILIN 269 MOTOR MANAGEMENT RELAY Series, Инструкция по эксплуатации

Страница: 4 / 142

1 INTRODUCTION
1-1
1.1 Motor Protection Requirements
Three phase AC motors have become standard in
modern industry. These motors are generally rugged
and very reliable when used within their rated limits.
Newer motors, however, tend to be designed to run
much closer to these operational limits and thus, there
is less margin available for any type of abnormal sup-
ply, load, or operating conditions.
In order to fully protect these motors, a modern protec-
tive device is required. Accurate stator and rotor ther-
mal modeling is necessary to allow the motor to
operate within its thermal limits and still give the maxi-
mum desired output. As well, other features can be
incorporated into a modern relay to fully protect the
motor, the associated mechanical system, and the
motor operator from all types of faults or overloads.
Motor thermal limits can be exceeded due to increased
current from mechanical overloads or supply unbal-
ance. Unbalance can greatly increase heating in the
rotor because of the large negative sequence current
components present during even small voltage unbal-
ances. A locked or stalled rotor can cause severe
heating because of the associated large currents drawn
from the supply. Many motor starts over a short period
of time can cause overheating as well. Phase-to-phase
and phase-to-ground faults can also cause damage to
motors and hazards to personnel. Bearing overheating
and loss of load can cause damage to the mechanical
load being driven by the motor.
The ideal motor protection relay should monitor the
rotor and stator winding temperatures exactly and shut
off the motor when thermal limits are reached. This
relay should have an exact knowledge of the tempera-
ture and proper operating characteristics of the motor
and should shut down the motor on the occurrence of
any potentially damaging or hazardous condition.
The GE Multilin Model 269 Motor Management Relay
®
uses motor phase current readings combined with sta-
tor RTD temperature readings to thermally model the
motor being protected. The relay also monitors the
motor and mechanical load for faults and problems.
With the addition of a GE Multilin meter (MPM), the
269 may also monitor voltages and power and perform
several protection functions based on these values.
1.2 269 Relay Features
The GE Multilin Model 269 Motor Management Relay
®
is a modern microcomputer-based product designed to
provide complete, accurate protection for industrial
motors and their associated mechanical systems. The
269 offers a wide range of protection, monitoring, and
diagnostic features in a single, integrated package. All
of the relay setpoints may be programmed in the field
using a simple 12-position keypad and 48 character
alphanumeric display. A built-in "HELP" function can
instruct the user on the proper function of each of the
programming keys and on the meaning of each dis-
played message.
One 269 relay is required per motor. Phase and
ground fault currents are monitored through current
transformers so that motors of any line voltage can be
protected. The relay is used as a pilot device to cause
a contactor or breaker to open under fault conditions;
that is, it does not carry the primary motor current.
All setpoints are stored in the 269 non-volatile memory
within the relay. Thus, even when control power is re-
moved from the 269, all relay setpoints and pre-trip
values will remain intact.
The 269 can provide one of various output signals for
remote metering or programmable controller attach-
ment. Analog signals of motor current as a percentage
of full load, hottest stator RTD temperature, percentage
of phase CT secondary current, motor thermal capac-
ity, or bearing temperature are available by simple field
programming. A total of four output relays are provided
on the 269, including a latched trip relay, an alarm re-
lay, and two auxiliary relays. All output relays may be
programmed via the keypad to trip on specific types of
faults or alarms.
When an output relay becomes active, the 269 will dis-
play the cause of the trip, and if applicable, the lock-out
time remaining. Pre-trip values of average and individ-
ual line motor current, unbalance, ground fault current,
and maximum stator RTD temperature are stored by
the 269 and may be recalled using the keypad.
The correct operation of the GE Multilin 269 relay is
continually checked by a built-in firmware self-test rou-
tine. If any part of the relay malfunctions under this
self-test, an alarm indication will tell the operator that
service is required.
1.3 Typical Applications
The many features of the 269 make it an ideal choice
for a wide range of motor protection applications. Ver-
satile features and controls allow the relay to protect
associated mechanical equipment as well as the motor.
The 269 should be considered for the following and
other typical uses:
1. Protection of motors and equipment from operator
abuse.
2. Protection of personnel from shock hazards due to
winding shorts or earth leakage current from
moisture.
3. Protection of gears, pumps, fans, saw mills, cut-
ters, and compressors from mechanical jam.