AZRS - Power Supply Switching Unit

     
     Synchronous and quasi-synchronous switching
 

      Advanced reliability improvement algorithms
 

      Widely used since 1995

The power supply switching units belong to the basic systems affecting certainty of power supply of consuming systems. The applied algorithms and setpoints have a basic influence among others on the following:

• depth of voltage dips,
• value of auto-starting currents and surge electromechanical moments of started motors.

The value of residual voltage and a phase angle between it and voltage in the network at the moment of restart of the motor decide the values of switching current and surge electromagnetic moment of the motor. Due to the insulation resistance of the standard motors it is assumed that the switching voltage should not exceed the value of 1,4 Un, what simultaneously is a condition ensuring non-violation of admissible values of stator's current and surge electromechanical moment of typical motors. Non-fulfilment of the afore-mentioned conditions results often in a serious breakdown of the motors. Damages of the motors, breaks in power supply of consuming systems cause disturbances / downtimes in technological processes, and in consequence they generate serious financial losses. Therefore, the automation systems must realize power supply switching in a fast, safe and reliable way. The switching should be realized in a synchronous mode (uninterruptible or with short break) or in a quasi-synchronous mode. The detailed requirements related to the algorithms and setpoints of automation power supply switching units depend on a kind of supplied consuming systems, requirements of concrete technological processes and quality / rigidity of backup power supply source.

The power supply switching automation, apart from the realization of automatic transfer switch (ATS) and return transfer switch (RTS) functions, should ensure also planned transfer switch (PTS) and automatic supply switch (ASS). The automatic realization of the RTS ensures a fast and reliable switching eliminating possible delays and errors occurring in a manual switching process.

The AZRS units are designed for operation in MV and LV switchgears supplying important motor or non-motor consuming systems having an essential influence on technological processes. They can be applied both to the systems with standby backup (AZRS2) and hidden backup (AZRS3). These units are constructed basing on dedicated controllers. They are equipped with a front panel on which a synopsis of the switchgear is located. Information on voltage values and executed switching is presented on the liquid crystal display.

The AZRS units realize switching in the following cycles:

• ATS in the fast (required for switchgears supplying motor consuming systems) synchronous, uninterruptible mode and in the synchronous mode with short break;
• ATS in the quasi-synchronous mode;
• ATS in the slow mode;
• ATS in all directions;
• RTS realized automatically after execution of ATS induced by voltage and restoration of basic supply voltage of switchgear;
• PTS in the uninterruptible mode;
• PTS in the synchronous mode with short break in supply;
• PTS in the quasi-synchronous mode;
• PTS in the slow mode

Additionally, AZRS units ensure:

• independent additional voltage control
• free declaration of basic supply of switchgear