Instructional Literature
Page
172
Effective: May 2008
Instructions for the FP-6000 Protective Relay
For more information visit: www.eaton.com
IB02602004E
The protection settings for the direct temperature measurements
should be based on the recommended maximum insulation
temperature of the protected object. Take a motor protection as
an example. The user should use the motor manufacturer’s
insulation classification on the nameplate.
Table 49. Example Insulation Temperature Classes
(from NEMA MG-1).
Note:
Rising winding temperature has to travel through the insulation and stator
iron to heat the RTD. When setting the stator temperature alarm and direct ther-
mal trip temperatures, keep in mind that the actual hottest-spot insulation temper-
ature may be 5 to15°C (41 to 59°F) above the hottest RTD measurement. This
additional temperature rise above insulation rating may cause the insulation to age
twice as quickly as it would if kept within rating. Set the thermal trip temperature a
little below the insulation rating for longest motor life.
The FP-6000 relay thermal protections and alarms are designed
not only for motor protection, but also intended for generator,
transformer, cable, etc. Obviously, for the direct temperature
measurements, it really does not matter what type of the
equipment may be protected. For the thermal model method,
the thermal limit curve may vary depending on the type of
equipment to be protected. The negative sequence current will
generate significantly more heat on a rotating machine, but has
the same effect as the positive sequence current for stationary
equipment such as power lines or a transformer. To
accommodate these application variations, the FP-6000 relay lets
the user decide what type of the effective current to choose. For
a rotating machine, I1 + KI2 with a choice of K can be used; while
for stationary equipment, RMS may be the choice. For the
transformer thermal applications, very often the transformer may
be allowed to run for some relatively long time under an
overload condition. In this case, the user could adjust the Ith and
Tth settings as well as the trip delay to achieve a desired thermal
protection and alarm.
The thermal capacity is the key element in the thermal replica
protection and alarm. When the user applies the FP-6000 thermal
protection to power lines or a transformer other than motor or
generator, the settings Locked Rotor Current and Maximum
Allowable Stall Time should be set based on the their thermal
current rating so that the thermal capacity solely determined with
these settings will correctly reflect the thermal limit of the
protected equipment.
Figure 69. Thermal Replica Model Limit and Trip Curves without RTD.
CLASS
A
B
F
H
Ambient Temp., Deg. °C
40
40
40
40
Ambient Rise, Deg. °C
60
80
105
125
Hot Spot Allowance, Deg. °C
5
10
10
15
Hot Spot Temp., Deg. °C
105
130
155
180
Ther
ma
l Repli
ca
Li
m
it
a
nd Trip Cur
v
es Without RTD
1
10
100
1000
0.1
1
10
100
Multiple of Full Lo
a
d A
m
pere
Ti
m
e in
se
c
on
ds
SF=1,TC=100%
Ith=120%,Tth=80%*TC
