SERVICE MANUAL R5888C
QUADRAMHO Chapter 5
Page 8 of 24
4.5.3 Phase faults
The appropriate loop impedance is now:
2 x K14
(K1 + K2) (K11 + K12 + K13)
ohms
I
n
Carry out the tests as for the ground faults, starting with A–B and proceeding to
B–C and C–A faults.
Note: If using a ZFB, VTS indication will now be obtained. Also the relay may
fail the self-check, see Section 4.15.
If scheme 08 or 09 is selected carry out 5.1 next.
4.6 Zone 2 reach tests
When checking Zone 2 reaches the effect of the expansion of the reach when any
trip occurs may be apparent.
If a fault is applied less than 5% outside the Zone 2 boundary and inside the
Zone 3 boundary, then if Zone 3 times out giving a trip output, Zone 2 indication
will also be seen if the fault is maintained for Zone 2 time after the Zone 3 trip
occurs.
The ground fault loop impedance required is:
(K1 + K2 + K4 + K5 + K6) (K21 + K22) K24
ohms
I
n
and for phase faults the loop impedance required is:
2 x (K1 + K2) (K21 + K22) K24
ohms
I
n
The reach for each type of phase-ground and phase-phase element of the relay
should be checked as in Section 4.5 and the operation of the appropriate
outgoing contacts confirmed.
Note: At the Zone 2 boundary some chatter of the fault locator contacts may be
heard prior to the trip, causing expansion of the zones.
4.7 Zone 3 reach checks
If ∞ has been set on t
Z3
, the switch must temporarily be moved to the left to enable
the reach checks to be done. Zone 3 has the facility for setting forward and
reverse reaches on the line angle up to the same impedance. There are three
different shapes available as selected by the customer when ordering the relay.
These are circular, lenticular or a quadrilateral for ground faults.
The presence of the lenticular shape is indicated on Module 3 by a switch labelled
a/b which controls the aspect ratio as illustrated on the frontplate. When a/b is set
to 1 the characteristic is circular.
The presence of the quadrilateral shape is indicated on Module 1 when a switch
(K3) for the setting of the resistive forward rach of Zones 1, 2 and 3 is fitted.
(see Figure 5). The resistive check will be described later.
The ground fault loop impedance required for forward checks is:
(K1 + K2 + K4 + K5 + K6) (K31 + K32) K33
ohms
I
n
To Next Page
Loading...