MPA3 V5.4 MOTOR PROTECTION RELAY MANUAL
Issue: R0, CRN: 8168, Date: 11/2010
MPAB009 Rev0
MPA3 V5.4 Motor Protection Relay Manual
Page 15
The ‘testing’ phase takes 3 seconds during which time the IT input must remain active in order to obtain a valid
result. The last IT result is retained in memory and displayed until a subsequent test or power down.
The measurement range is 125 M
down to 0.8 M
, with <0.8 M
displayed for values less than 0.8 M
.
The trip level is selected via the ‘
ITst Trp
’ setting (Level 7, Position 17) and is adjustable between 1.0 M
and 100
M
.
The alarm level is selected via the ‘
ITst Alm
’ setting (Level 7, Position 18) and is adjustable between 1.0 M
and
100 M
.
A trip takes priority if both trip and alarm conditions occur as a result of an IT.
IT alarms self-clear when a subsequent IT result is greater than the selected alarm value. They can also be reset
manually by operating the reset key/digital input.
IT trips are latched and prevent subsequent IT’s until the trip is manually reset by operating the reset key/digital input.
Setting either the ‘
ITst Trp
’ or ‘
ITst Alm
’ setting to ‘OFF’ disables that function.
10
Under-voltage Trip
The optional Insulation Test Module (MPA-I) allows Under-voltage protection that is enabled as soon as the main
contactor is closed (indicated by closing the MCI input). If any of the phase voltages drop below the selected trip
setting of the nominal line voltage for 1.5 Seconds then the MTR relay is de-energised.
To reset the relay following an under-voltage trip, operate the reset key/digital input.
The trip level is selected via the ‘
UV Level
’ setting (Level 7, Position 19) and is adjustable from 40% to 95%. Setting
the trip level to ‘Off’ disables this function.
11
PT-100 RTD Temperature Protection
The optional Monitoring Module (MPA-M) allows temperature monitoring of 5 PT-100 RTDs, connected in 3-wire
mode. The three-wire connection allows compensation of installation lead resistance. The RTD inputs are configured
as ‘Group1’ RTD’s (1, 2 and 3) and ‘Group 2' RTD’s (4 and 5). Each Group has a separate alarm and trip level.
Group 1 (G1) is intended for monitoring stator temperature while group 2 (G2) is intended for bearing temperature.
The Trip levels are selected via the ‘
RTD G1 T
:’ and/or ‘
RTD G2 T
:’ settings (Level 7, Position 20 and 22) and are
adjustable from 60°C to 200°C. If the measured value exceeds the trip level for 2 seconds, a trip occurs. Trips are
latched, and cannot be reset by the reset/digital input until the temperature falls back below the trip threshold.
Setting the trip level to ‘Off’ disables this function.
The Alarm levels are selected via the ‘
RTD G1 A
:’ and/or ‘
RTD G2 A
:’ settings (Level 7, Position 21 and 23) and are
adjustable from 50°C to 200°C. If the measured value exceeds the alarm level for 2 seconds, an alarm occurs.
Alarms self clear once the measured value falls below selected value for 2 seconds. Setting the alarm level to ‘Off’
disables this function.
A trip takes priority if both trip and alarm conditions occur as a result of a RTD’s temperature.
