Circuit breaker controller contains two features: SOTF and frequent-operation counter. SOTF protects the AR function in permanent faults.
The circuit breaker position information is controlled with the CB closed Pos status setting. The setting value "TRUE” means that when the circuit breaker is closed, the CB_POS input is TRUE. When the setting value is “FALSE”, the CB_POS input is FALSE, provided that the circuit breaker is closed. The reclose command pulse time can be controlled with the Close pulse time setting: the CLOSE_CB output is active for the time set with the Close pulse time setting. The CLOSE_CB output is deactivated also when the circuit breaker is detected to be closed, that is, when the CB_POS input changes from open state to closed state. The Wait close time setting defines the time after the CLOSE_CB command activation, during which the circuit breaker should be closed. If the closing of circuit breaker does not happen during this time, the autoreclosing function is driven to lockout or, if allowed, an auto-initiation is activated.
The main motivation for autoreclosing to begin with is the assumption that the fault is temporary by nature, and that a momentary de-energizing of the power line and an automatic reclosing restores the power supply. However, when the power line is manually energized and an immediate protection trip is detected, it is very likely that the fault is of a permanent type. A permanent fault is, for example, energizing a power line into a forgotten earthing after a maintenance work along the power line. In such cases, SOTF is activated, but only for the reclaim time after energizing the power line and only when the circuit breaker is closed manually and not by the AR function.
SOTF disables any initiation of an autoreclosing shot. The energizing of the power line is detected from the CB_POS information.
SOTF is activated when the AR function is enabled or when the AR function is started and the SOTF should remain active for the reclaim time.
When SOTF is detected, the parameter SOTF is active.
The frequent-operation counter is intended for blocking the autoreclosing function in cases where the fault causes repetitive autoreclosing sequences during a short period of time. For instance, if a tree causes a short circuit and, as a result, there are autoreclosing shots within a few minutes interval during a stormy night. These types of faults can easily damage the circuit breaker if the AR function is not locked by a frequent-operation counter.
- Frq Op counter limit
- Frq Op counter time
- Frq Op recovery time
If the circuit breaker is manually closed during the recovery time, the reclaim time is activated after the recovery timer has elapsed.