ABB Modures LZ92-1 - OPERATION AND MAINTENANCE GUIDE

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As soon as one or more of the test buttons (R, s or T) are pressed, the corres-
ponding starting unit or units pick up and the auxiliary tripping relay is
interlocked to prevent operating the circuit-breaker inadvertently.
The starting units apply phase quantities to the measuring unit according to
the kind of fault being simulated.
The relay will pick up in some stage or other depending on the load current at
the time and the relay settings. (If the values and phase-angle of the load
quantities is known, it is even possible to test the various zones by suitably
changing the settings.)
Providing the fourth zone is non-directional, the relay must at very least
pick-up in the fourth zone (red LED lights up) •
The fourth zone must be made directional and all the zones be measuring in the
forwards direction in order to check the relay's ability to determine direc-
tion. The corresponding switch positions are: switch Ba in position 1, switch
Sb in position 1 or 2 depending on input transformer connection and switch 7 in
position 1.
Caution! Units may only be withdrawn from the rack when the auxiliary
supply is switched off.
Under the above conditions the relay must pick up when the load energy is
flowing in the forwards direction and block when the energy direction is
reversed by operating switch Sb (part number HESG 439 686) or the frontplate
switch I~ (part number HESG 440 718), or vice versa.
The ability of the relay to pick up and block must be tested in this way for
all kinds of faults.
Withdrawing a relay with non-directional fourth zone can be avoided by setting
the thumbwheel switch N of the corresponding zone to 0% (infinite reach).
Should the direction be incorrect for a particular kind of fault, the polarity
of al 1 c. t' s, p. t 's, leads and connections must be checked (see Sections 5. 3
and 5.4). If the direction is incorrect for all kinds of faults, all the
current connections must be reversed. In the case of relays LZ92 and LZ92-1
with off-set starting characteristics care must be taken that the longest reach
of the starters is in the desired direction (see Section 3.6).
Provision is made on the input transformer unit EW91 from part number HESG 440
754 to apply a signal manually to the auxiliary tripping relay and thus trip
the circuit-breaker. This operation, however, is interlocked for safety rea-
sons. Firstly terminal Ell of the input transformer unit must be connected to
terminal E63 of the main processing unit. Then the sockets & and->\'- must
be connected. Finally a starting button must be pressed. It is not possible to
test the tripping circuit, if the connection Ell-E63 is not made.
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