CHAPTER 7: TESTING
239 MOTOR PROTECTION RELAY – INSTRUCTION MANUAL
7–101
7.5
Phase Unbalance Alarm
1.
Alter the following setpoints:
S4: PROTECTION\PHASE CURRENT\UNBALANCE\PHASE UNBALANCE
ALARM:
ON
S4: PROTECTION\PHASE CURRENT\UNBALANCE\PHASE UNBALANCE TRIP:
OFF
S4: PROTECTION\PHASE CURRENT\UNBALANCE\PHASE UNBALANCE ALARM
PICKUP:
20%
S4: PROTECTION\PHASE CURRENT\UNBALANCE\PHASE UNBALANCE DELAY:
0 SEC
2.
Inject three-phase current at the FLA level into all three phases. While viewing
A2:
METERING\CURRENT\CURRENT UNBALANCE U/B
, slowly decrease the current
in one of the phases until the UNBALANCE ALARM message comes on. Please note
that the unbalance feature will not operate if the load is
≤
30% FLC. In the table below,
record the injected current level at the point when the unbalance alarm occurred. Use
the formulae shown below to calculate percent unbalance using the currents
recorded in the table. Compare the calculated value to the displayed value on
A2:
METERING\CURRENT\CURRENT UNBALANCE U/B
and ensure they are match.
3.
Unbalance is calculated as follows:
For average currents (
I
av
) greater than or equal to the motor full load current (
I
FLC
):
For average currents less than motor full load current:
where:
I
m
= RMS current in any phase with maximum deviation from the average current (
I
av
)
I
FLC
= motor full load current
I
a
= phase A current
I
b
= phase B current
I
c
= phase C current
Table 7–3: Phase Unbalance Alarm Test
ACTUAL DISPLAY READING (A)
PHASE UNBALANCE
PHASE A
PHASE B
PHASE C
CALCULATED
DISPLAYED
%UB
I
m
I
av
–
I
av
---------------------
100%
×
for
I
av
I
FLC
≥
=
%UB
I
m
I
av
–
I
FLC
---------------------
100%
×
for
I
av
I
FLC
<
=
I
av
I
a
I
b
I
c
+
+
3
------------------------
average of three phase currents
=
=
Содержание Multilin 239
Страница 6: ...TOC 4 369 MOTOR MANAGEMENT RELAY INSTRUCTION MANUAL TABLE OF CONTENTS ...
Страница 20: ...1 14 239 MOTOR PROTECTION RELAY INSTRUCTION MANUAL CHAPTER 1 OVERVIEW ...
Страница 48: ...3 10 239 MOTOR PROTECTION RELAY INSTRUCTION MANUAL CHAPTER 3 OPERATION ...
Страница 96: ...4 58 239 MOTOR PROTECTION RELAY INSTRUCTION MANUAL CHAPTER 4 PROGRAMMING ...
Страница 108: ...5 70 239 MOTOR PROTECTION RELAY INSTRUCTION MANUAL CHAPTER 5 MONITORING ...
Страница 149: ...CHAPTER 7 TESTING 239 MOTOR PROTECTION RELAY INSTRUCTION MANUAL 7 111 FIGURE 7 2 239 Hardware Block Diagram ...
Страница 150: ...7 112 239 MOTOR PROTECTION RELAY INSTRUCTION MANUAL CHAPTER 7 TESTING ...
Страница 152: ...A 2 239 MOTOR PROTECTION RELAY INSTRUCTION MANUAL CHAPTER A ...