GEK-65525
THREE-PHASE POWER-DIRECTIONAL RELAY
TYPE CCP13E
DESCRIPTION
The type CCP13E relay is a very sensitive induction-cylinder power-directional relay
for three-phase alternating-current circuits.
The relay consists of three single-phase directional units with the three rotors
mounted on a single shaft.
The contact assembly consists of two electrically
separate contacts, one normally open and one normally closed.
The normally-closed
contacts are held closed by two spiral springs that also complete the control
circuits to the moving contacts.
There is a target and seal-in coil in series with
the normally-open contact.
The CCP13E relay is functionally equivalent to the CCP13D relay, but the two relays
are not electrically interchangeable.
There are differences in the output circuit
arrangements.
APPLICATION
Because of its sensitivity and its real power-directional characteristics, the
CCP13E relay finds application where it is important to detect extremely small
reverse power flow.
This application is restricted to cases where the normal
direction of power flow is always in the same direction.
The classical example of
such an application is illustrated in Figure 1.
Consider the section of a system shown in Figure 1 with normal load flow from the
system to the load.
If a single-phase-to-ground fault were to occur at F, it would
be cleared at source
#2,
but not necessarily at breaker
#2
because of delta-wye
transformer
#2.
However, it is desirable to open circuit breaker
#2
to clear the
ground fault completely.
This can be accomplished by the CCP13E relay associated
with circuit breaker
#2.
The CCP13E is generally sensitive enough to operate on the
real component of the exciting current (this is the core-loss component) taken by
the transformer through circuit breaker
#2
when source
#2
is removed.
Since the CCP13E is very fast and very sensitive, it might operate for system
disturbances that result in momentary reversals of power through one or the other of
the two banks.
For this reason, the CCP13E should be used in conjunction with some
time delay when applied as discussed above.
Figure
2
shows how this can be done.
Before the CCP13E is applied, certain calculations should be made to check the
sensitivity of the relay,
against the available core-loss component of the
associated transformer, to ensure proper operation.
A sample calculation is
illustrated in the section titled
SAMPLE CALCULATIONS.
In general, the current
transformers (CT•s) that supply the CCP13E relay should be selected with the lowest
possible ratio without exceeding the
5.0
ampere continuous rating of the relay.
3
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