IMM 8001/8002 – Digital Motor Protection Relay
ICE / CEE
____________________________________________________________________________________________
IMU307-1 GB Ind. B
66
TESTS : Verification of NEGATIVE PHASE SEQUENCE CURRENT protection [46]
CONNECTION, COEFFICIENT OF CORRECTION
Protection verification
Current injection
Coefficient
M
to be applied
Terminals
In =
1A
In =
5A
- single-phase
1.732
2-4 or 10-12
3-5 or 11-13
- unbalanced
three-phase
1
2-4 phase 1
3-5 phase 1
(reverse phase rotation : reversal of phases
10-12 phase 3
11-13 phase 3
1 and 3).
Caution – the adjustment of coefficient K must be taken into account in the current to be injected :
K = In machine/IN
CT
Sequence of operations to be performed
Results to be obtained
Time equation : extremely inverse time response curves
t =
)²
In
/
INeg
(
²
CK
Check of negative phase sequence component unit
Check of curve with nominal value (Ineg/In = 1)
Put into service the protection, and route it to a chosen unit.
Note the values for
C
time constant
K
In machine / IN CT ratio
Ineg>
curve starting operating level
tmin
curve minimum time
Use the contact of this unit to stop the timer.
Connect the current generator according to the desired connection deduce
M
Preset the current to be injected to In x
M
,
then cut it off.
If necessary, check the value Ineg = In on the display.
Inject the current.
Other points can be deduced from the equation or the previous curves,
especially the minimum response time
tmin
for high negative sequence
currents and the maximum time which is fixed and equal to 50 s.
Check of operating level Ineg>
Preset the current to be injected to 1.2 x Ithresh. x
M
,
then cut it off.
Inject the current.
Preset the current to be injected to 0.8 x Ithresh. x
M
,
then cut it off.
Inject the current.
t
(s)
=
²
1
²
CK
= CK²
The protection Ineg> must operate at the end of time t
The time found must be equal to t = C K²
The fault message and related informations must be
displayed at the end of t,
The Start Function indicator LED illuminates
immediately as soon as operating level Ineg> is
reached,
The Internal Trip indicator LED illuminates at the end of
the time-delay.
The protection Ineg> must operate during 40 to 50s
irrespective of the operating level.
The protection must not operate (wait for a clearly higher
time).