IMM 8001/8002 – Digital Motor Protection Relay
ICE / CEE
____________________________________________________________________________________________
IMU307-1 GB Ind. B
55
TESTS : Verification of the protection AGAINST TOO LONG STARTS [48]
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
- balanced three-phase
1
2-4 phase 1
3-5 phase 1
10-12 phase 3
11-13 phase 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
Equation for time/current characteristic
t =
)²
/
(
)²
(
1
.
1
In
IPos
tst
x
Ist
>
>
For this test simulating start, inject an Ipos current instantaneously changing
from 0 to the injection value.
Check of overcurrent unit against too long starts
Unit check with starting current value
Put into service the protection, and route it to a chosen unit.
Note the adjustment value of starting current
Ist>
Note the adjustment value of starting time
tst>
Connect the current generator according to the desired connection, deduce
M
Preset the current to be injected to the displayed starting current by taking
M
into account so that (IPos/In)² = Ist>
I = Ist> x
M
If necessary, check the value of IPos on the display.
Inject the current.
If necessary, check the values of the last recorded current and starting time.
Note
: the function is put into serviced during twice the programmed starting
time, i.e. 2 x tst>
Caution :
the minimum response time automatically becomes 250 ms
when
-
the function [50] (I>>) is disabled.
-
Current > 2 Ist.
t =
)²
(
)²
(
1
.
1
>
>
>
Ist
tst
x
Ist
= 1.1 x tst>
at the end of adjusted 1.1 x tst> :
the selected relay must be energised,
the Start Function indicator LED illuminates
instantaneously,
the Internal Trip indicator LED illuminates at
the end of the time-delay,
the fault message and related informations must
be displayed.
Note
: the Start Motor indicator LED remains ON
during a time equal to 2 x tst> or during the injection
time.