GE DBF, Instructions Manual

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7. INSTALLATION AND MAINTENANCE
GEK-106168E DBF Breaker Failure Protection 39
7. 7. 7. 7. INSTALLATION AND MAINTENANCE INSTALLATION AND MAINTENANCE INSTALLATION AND MAINTENANCE INSTALLATION AND MAINTENANCE
7.1. INSTALLATION
The relay should be installed in a clean, dry and dust-free place, with no vibrations.
The DBF system is supplied in a 19’’ rack case 2 units high. Figure 5 shows the dimension diagram.
The relay should be mounted on a vertical surface. Figure 6 shows a diagram for panel drilling.
Given that the design of the DBF unit is based on high performance digital technology it is not necessary to
calibrate the relay. However if the tests show that it is necessary to readjust the relay, it is recommended to return
the unit to the factory to check it.
7.2. CONNECTION-TO-GROUND AND DISTURBANCES SUPPRESSION
The terminal (see Figure 2) should be connected to ground so that the disturbance suppression circuits in the
system works correctly. This connection should be as short as possible (preferably 25 cm or less) to guarantee
maximum protection. In this way the capacitors that are internally connected between the inputs and ground divert
high frequency disturbances directly to ground without passing through the electronic circuits. Then the internal
circuitry is perfectly protected.
In addition this connection also guarantees the physical safety of the personnel when handling the relay, since the
whole casing is connected to ground.
7.3. MAINTENANCE
Given the important role that the protection relays play in the operation of any installation, a periodic program of
tests is highly recommended. The unit incorporates built-in diagnostic functions that permit the fast identification of
some of the most likely circuit failures. Testing the unit is recommended at intervals of 2 years or more. Although
the built-in diagnosis does not reduce the average time between failures, it does increase the availability of the
protection because it allows a drastic reduction in the average interruption time involved in detecting and repairing
the fault.
The set of tests which can be performed to test that all aspects of the DBF unit function properly is described in
detail in the chapter entitled ACCEPTANCE TESTS.
Since most of the protection and communications functions are integrated in two separate programs, it is unlikely
that faults will occur due to problems of wear and tear, short-circuits or aging which are typical in other
electromechanical protection systems, whether analogue or hybrid. Moreover, a failure in the communications
processor does not affect the protection functions, which are implemented by a dedicated processor.