Eaton Cutler-Hammer FP 5000 Instruction Leaflet page 135

IL17569C
Page 8-4
Effective Date: 12/05
NOTICE
AS SHOWN IN FIGURE 8.4, THE ANSI AND IEC "CURVE
SHAPES" ARE IN TERMS OF MULTIPLES OF I
CURRENT OF THE CT PRIMARY), WHEREAS, "SHORT DELAY"
AND "INSTANTANEOUS" ARE IN TERMS OF MULTIPLES OF I
(5 A OR 1 A SECONDARY OF CT CURRENT). THE THERMAL
CURVE IS REPRESENTED IN TERMS OF MULTIPLES OF I
FOR ITS CURVE SHAPE, SHORT DELAY AND INSTANTANEOUS
SETTINGS. THIS MUST BE CONSIDERED IN THE COORDINA-
TION STUDY AND IN THE PROGRAMMING OF THE FP-5000
PROTECTIVE RELAY.
The ANSI curves are defined by ANSI C37.112, and IEC curves are
defined by lEC 255-3. These curve shapes combined with the
customized capability of the short delay and instantaneous functions
allow for very versatile coordinated protection schemes. The thermal
curve shape is also customized by the user for any desired type of
coordinated protection scheme.
Figure 8-5. Sample Electronic Trip Curves
Adjustability
The adjustability of the relay permits movement of its characteristic
curve or parts of the curve. This movement can be done in both a
horizontal and vertical direction on the time current grid. The actual
shape of the curve can be changed along with the curve movement.
This adjustability permits distinct curves to be established to match
the electrical protection to the application. (Figure 8-6 through
Figure 8-11.) Horizontal movement of the ANSI and lEC curve
shapes is controlled by changing the pickup setting. Changing the
pickup setting of the thermal curves moves the point at which the
relay starts to time out along the curve shape.
Page 8-4
FP-5000
(PICKUP
PU
NOM
NOM
For more information visit:
These curves show how and when a particular relay will act for given
values of time and current. The more versatile the relay, the easier it
is to accomplish close coordination and achieve optimum protection.
Since the FP-5000 Protective Relay is very versatile, the makeup of
a typical curve is presented for clarification.
For the sake of simplification, the curve discussion will center on a
single line curve. Keep in mind, however, that a characteristic curve
in reality is represented by a band of minimum and maximum values,
not a line (Figure 8-5, Sample Electronic Trip Curves, below).
Minimum and maximum values are generally the result of manufac-
turing tolerances for components and the relay's accuracy. Any
expected value of tripping current or time could be the nominal value
anticipated within a plus or minus tolerance. The tolerances are
usually stated in terms of the relay's accuracy and frequently
highlighted on the actual working curves. Accuracy is stated in
terms of a plus or minus percentage and represents a permitted
fluctuation on either side of the nominal tripping point for a family of
relays, like the FP-5000.
Figure 8-6. Typical Inverse Time Overcurrent
Pickup Horizontal Movement
www.eatonelectrical.com Effective Date: 12/05