Page 5-9
MPS Motor Protection System Rev. 6-F-022117
Protective Functions
5.25 DIFFERENTIAL CURRENT PROTECTION
OPI Menu: Setup | Protection | Differential
OPI Menu: Setup | Hardware | DIF Module
OPI Menu: Setup | System Ratings | DF-CT Primary
The MPS-DIF provides three-phase differential
protection. It is intended to be used specifically for motor
protection and not intended for feeder or transformer
differential protection.
Enable the module and communications-loss protection
using the Setup ⏐ Hardware ⏐ DIF Module menu. The
module uses I/O module communications and both trip
and alarm actions are available in the event of
communications loss.
Set DF-CT Primary equal to the differential-CT-primary
rating. For the MPS summation connection, PH-CT
Primary and DF-CT Primary must be equal.
Trip and alarm settings are based on multiples of the
DF-CT Primary rating (I
d
).
Trip Level ............................. 0.10 to 15.00 x I
d
Trip Delay ............................. 0.00 to 10.00 s
Alarm Level .......................... 0.10 to 15.00 x I
d
Alarm Delay ......................... 0.00 to 10.00 s
Protection .............................. Enable/Disable Trip1,2,3
Enable/Disable Alarm1,2,3
Measurement Method ........... DFT c/w CT saturation
compensation.
5.26 PTC TEMPERATURE
OPI Menu: Setup | Protection | PTC Temperature
A positive-temperature-coefficient (PTC) thermistor
input is provided on the MPS-CTU. The total resistance
of series-connected PTC thermistors must be less than
1,500 Ω at 20°C (68°F). A trip or alarm will occur when
series resistance exceeds 2,900 Ω.
NOTE: During Emergency Thermal Reset, a PTC trip is
reset and PTC-temperature protection is disabled. See
Section 5.2.3.
Protection .............................. Enable/Disable Trip1, 2, 3
Enable/Disable Alarm1, 2, 3
5.27 RTD TEMPERATURE
OPI Menu: Setup | Protection | RTD Temperature
OPI Menu: Setup | Hardware | RTD Module
Up to three RTD modules can be connected to the
MPS-CTU. Select the number of modules in the Setup |
Hardware | RTD Modules menu. Each module can
monitor eight RTD’s for a total of twenty-four RTD’s.
RTD type, function, and trip and alarm set points are
programmable for each RTD.
When an RTD type is selected, trip and alarm functions
are determined by Temperature Trip and Alarm settings.
During Emergency Thermal Reset, an RTD trip is reset
and RTD-temperature protection is disabled. See
Section 5.2.3.
RTD failure detection is provided. The actions for an
RTD failure are selectable as Trip1, 2, or 3 and as
Alarm1, 2, or 3. The selections apply to all RTD's.
The MPS supports three MPS-RTD modules with each
module supporting eight RTDs. Each RTD can be
assigned to one of eight function groups; Stator, Bearing,
Load, Ambient, Stator Voting, Bearing Voting, Load
Voting, and Ambient Voting. The specific assignment is
set using the Setup | Protection | RTD Temperature |
Module x | Function menu. Regardless of the assigned
function, individual RTD trip and alarm setpoints remain
active.
When an RTD is assigned to a voting group, it
participates in the voting logic. Within a voting group,
two RTDs must indicate a temperature above their trip
setpoint in order to cause a trip. The first two RTDs that
indicate a high temperature will generate a trip.
Subsequent trips resulting from other RTDs in the group
are not locked out. Trips must be individually reset and
all trips must be reset to allow a start.
Failed sensors do not participate in the RTD voting
logic. For example if six sensors are set to Stator Voting
and two sensors fail, only four participate in RTD voting.
When RTD voting is used, it is assumed that continuity of
service is of high importance. In this case it is
recommended to set the sensor-failure action to alarm
only or to set the trip action to a value different than the
Temperature Trip Action.
If only one RTD is assigned to a group, or if only one
RTD is active because of sensor failures, RTD protection
is the same as the corresponding non-voting function.
RTD voting is not available for alarm setpoints.
RTD voting is contained within the specific function
group and within the RTD module. An RTD in one
module does not participate in the voting logic of another
module.
Name ..................................... 18 Character, Alphanumeric
Type ...................................... Disable, Pt100, Ni100,
Ni120, Cu10
Function ................................ Stator, Bearing, Load,
Ambient,Stator Voting,
Bearing Voting, Load
Voting, Ambient Voting
Trip Range ............................ 40.00 to 200.00°C (104°F to
392°F)
Alarm Range ......................... 40.00 to 200.00°C (104°F to
392°F)
Display Range ...................... -40.00 to 200.00°C (-40°F to
392°F)
Error Codes ........................... -100 = No Sensor
-90 = Open Sensor
-80 = Shorted Sensor
-70 = No Data/Module Error
(Codes accessed via network
communications)
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