БАО — emergency trip unit for radial substations

Emergency trip unit for (6–10) kV vacuum circuit breakers, shunt-release scheme on AC control power, for radial substations

Purpose:

БАО supplies ВР1 vacuum circuit breakers at transformer substations and packaged switchgear with 220 V AC or rectified control power.
In normal operation БАО supplies the vacuum circuit breakers from the auxiliary transformer, or from an НТМІ instrument transformer with a 100 V winding stepped up to 220 V by the БПН unit.
With no control voltage present, БАО charges the capacitor bank and holds the voltage needed to trip the vacuum breaker, drawing on the relay windings of one or two ТЛК-10 current transformers fed by the outgoing-line current.
On a short circuit in the outgoing lines with no control voltage present — and where the short circuit was preceded by little or no current in those lines — БАО quickly charges the vacuum breakers’ capacitor bank and issues a trip-enable command. It does so by closing volt-free contacts once enough energy has been stored to trip the breaker. The energy for charging the bank comes from the secondary windings of current transformers fed by the outgoing-line current.