IMM 8001/8002 – Digital Motor Protection Relay
ICE / CEE
____________________________________________________________________________________________
IMU307-1 GB Ind. B
40
TESTS : Verification of THERMAL IMAGE protection [49]
CONNECTION, COEFFICIENT OF CORRECTION
The protection, which depends on thermal current Ith, allows for symmetrical components Ipos and Ineg as well as the adjustment of the negative phase sequence
component operating level Ineg> acting as a multiplying coefficient on the negative sequence current.
- During a test with balanced three-phase current, there is no negative phase sequence component, and Ith is directly proportional to Ipos, therefore to injected I
Therefore, it will be possible to test various curve points by using the computation related to equations 1 and 2 below.
- During a single-phase test, a negative sequence component occurs, and the values of Ipos and Ineg are divided by
√
3. Therefore, the value of Ith is fully
modified. In this case, the protection will be checked only at
2In,
and 2 base times will be obtained according to Ineg> adjustment :
injection terminals 2-4 or
10-12 (1 A), terminals 3-5 or 11-13 (5 A).
Caution – the adjustment for coefficient K must be considered in the current to be injected : K = In machine / IN CT
Sequence of operations to be performed
Results to be obtained
Time equation (curves when cold) thermal unit Ith>
from 1.07 to 3.2 In
from 3.2 to 12 In
t = Tau Ln
14
.
1
)²
In
/
Ith
(
)²
In
/
Ith
(
−
t = Tau Ln
14
.
1
)
In
/
Ith
(
2
.
3
)
In
/
Ith
(
2
.
3
−
1
Time equation (curves when cold) thermal alarm unit Ith>Al
from 1.07 to 3.2 In
from 3.2 to 12 In
t = Tau Ln
>
−
IthAL
)²
In
/
Ith
(
)²
In
/
Ith
(
t = Tau Ln
>
−
IthAL
)
In
/
Ith
(
2
.
3
)
In
/
Ith
(
2
.
3
2
Thermal unit check at 2 In function [ 49-1]
Put into service the protection, and route it to a chosen unit.
Note the value of parameterised time constant Tau.
Use the contact of this unit to stop the timer.
Connect the current generator according to the desired connection :
with three-phase correctly balanced or with single-phase.
Preset the injected current to
2 In,
then cut off.
Reset the thermal state with ERST or EL5 / EL6.
Inject the current.
If necessary, check changes in the thermal state.
With three-phase correctly balanced other points can be deduced from
equation
1
or the fig. page 37.
with three-phase correctly balanced
t
(s)
= 60 Tau Ln
14
,
1
²
2
²
2
−
=
20.13 Tau
with single-phase
Ineg> <0.3 In
t(s)
=
5.36 Tau
Ineg> > 0.3 In
t(s)
=
14.44 Tau
the Ith> protection must operate after time :
t(s) = x.xx Tau
the fault message must be displayed,
the Start Function and Internal Trip indicator LEDs
illuminate simultaneously.
Thermal alarm unit check Ith>Al at 2 In function [49-2]
with three-phase correctly balanced
Ith>Al
Energise the protection , and route it to a chosen unit.
Note the value of parameterised time constant Tau.
t(s) = 60 Tau Ln
>
−
IthAl
²
2
²
2
=
1
17.26Tau
0.9
15.29Tau
0.8
13.39Tau
Use the contact of this unit to stop the timer.
Ith>Al
Connect the current generator according to the desired connection.:
with single-phase
1
0.9
0.8
Ineg> < 0.3 In
t(s)=
Ineg> > 0.3In
t(s)=
4.68Tau
12.47Tau
4.19Tau
11.10Tau
3.71Tau
9.76Tau
Preset the injected current to
2 In,
then cut off.
Reset the thermal state with ERST or the EL6 input.
Inject the current.
With three-phase correctly balanced other points can be deduced from
equation
2
or the fig. page 39.
Warning
: with single-phase, please check that at each current injection the
LED "Motor ON" illuminates. Below 1.9
In
the LED
is not illuminated and the
protection use the cooling constant Tau-C instead of Tau.
the Ith>Al protection must operate after time :
t(s) = x.xx Tau
the alarm message must be displayed,
the Alarm indicator LED must be iluminated.
