HARDWARE
For the second case shown on the table, open breaker, its auxiliary contact 52/a remains open, and current cannot flow through it for detecting continuity. In order to correctly monitor the circuit, a resistor must be used, not included in the protection, connected in parallel. The value of resistance will be selected so that the V 52/a input circuit minimum detection current flows, but not as high as to activate the breaker tripping coil. The figure shows the following equation:
V min – 15
R =
2 |
|
Where: |
|
Vmin | Is the minimum voltage, in Volts, expected in the battery (e.g. 80% of Vn) |
R | Resistance, in kilo ohms. |
2 | 2 mA of approximate current flowing through input V 52/a |
As shown in the second case in the table, with an open breaker, as current will flow through R if there is continuity in the WHOLE tripping circuit, voltage will be detected in input V 52/a.
This works correctly in steady state. However, if the breaker trips, while it is opening, the V 52/a input signal can be deactivated without this meaning that the circuit is not correct. This is due to the fact that the tripping relay, terminals
Therefore, if there is a trip signal, it is admitted that no signal will be detected during a period of 1 s to allow the breaker to open, and reopen the tripping relay
FIGURE 3-11 shows the possibility of monitoring the circuit only when the breaker is closed. In this case resistance R will not be used, but it must be observed in the unit logic, that the corresponding signal CONTACT INPUT_00_15 (SUP_COIL2), will be activated showing a failure when the breaker is open, and therefore it will be required to supervise the continuity failure signalling by the breaker status information.
CIO Remote CAN Digital I/O Module | 25 |
